Co-reporter:Cheng-bin Gong, Xiao-xiao Ou, Song Liu, Yong-lei Jin, Hai-rong Huang, Qian Tang, Michael Hon-Wah Lam, Cheuk-fai Chow, Qian Tang
Dyes and Pigments 2017 Volume 137() pp:499-506
Publication Date(Web):February 2017
DOI:10.1016/j.dyepig.2016.10.047
•Molecular imprinting-based fluorescent and solvatochromic chemosensor was synthesized.•Chemosensor 1 exhibits a turn-off fluorescent response toward phthalate esters in ethanol.•Chemosensor 2 shows solvatochromic properties.•Chemosensor 2 displays fluorescent-enhancing and colorimetric response toward DBP.This paper reports a molecular imprinting-based fluorescent and solvatochromic multifunctional chemosensor for phthalate esters (PAEs). The multifunctional chemosensor was fabricated through precipitation polymerization using 4-[(1E)-4-(2-hydroxyphenyl) ethenyl]-1-allylpyridinium bromide (HPEAPB) as the functional monomer and phthalamide-4,4′-dibutyl dimethyl ester (PDDB) as the mimic template. The molecular imprinting-based chemosensor shows specific affinity toward PDDB and dibutyl phthalate (DBP) in ethanol. Of note is that the molecular imprinting-based chemosensor shows turn-off fluorescent response toward PAEs in an ethanol solution with a limit of detection of 2.0 × 10−6 mol L-1 (0.7 ppm) when HPEAPB is in the protonated form (chemosensor 1), and shows solvatochromic properties, fluorescent enhancement and a colorimetric (from orange to bright yellow) response toward PAEs in an ethanol solution with a limit of detection of 4.0 × 10−5 mol L-1 by the naked eye when HPEAPB is in the deprotonated form (chemosensor 2). This multifunctional chemosensor is promising for the simple, accurate and low-cost detection of trace PAEs.
Co-reporter:Ka-Lok Ho;Ka-Ki Yuen;Man-Shan Yau
Archives of Environmental Contamination and Toxicology 2017 Volume 73( Issue 3) pp:410-420
Publication Date(Web):02 August 2017
DOI:10.1007/s00244-017-0438-1
Bisphenol A (BPA) glucuronide and sulfate conjugates are major products of Phase II metabolism of BPA in humans. In the past, their determination in body fluids usually involves tedious enzymatic hydrolysis and multiresidual analysis. The recent availability of authentic standards of these conjugates enables our better understand of the human metabolism of BPA and the distribution of their metabolites in body fluids. In this work, we report the chemical synthesis and purification of BPA mono- and di-glucuronide and BPA mono- and di-sulfate. Their levels, as well as that of BPA, in 140 paired human plasma and urine samples collected randomly from voluntary donors in Hong Kong SAR, China, were determined by solid-phase extraction and liquid chromatography–tandem mass spectrometry (LC–MS/MS). BPA was found in more than 135 human plasma and urine samples. Its Phase II metabolites, ranging from N.D. to 36.7 µg g−1-creatinine, also were detected in 139 of the 140 urine samples. Good correlation (r = 0.911) between molar concentration of BPA in the plasma and that of “total urinary BPA” (i.e., ln [(BPA + ∑ BPA phase II conjugate)molar concentration]) was observed. Direct quantification of Phase II metabolites of BPA in human urine can be a useful assessment tool for population exposure to this potent endocrine disrupting chemical.
Co-reporter:Hui Li, Wei Shen, Michael Hon-Wah Lam, Haojun Liang
Analytical Biochemistry 2017 Volume 533(Volume 533) pp:
Publication Date(Web):15 September 2017
DOI:10.1016/j.ab.2017.04.006
•We investigate intracellular degradation of foreign DNA strand by using DNA probes.•We report a novel degradation behavior that only excises the first nucleotide of 5′ terminal of DNA strand.•We propose an effective way to avoid degradation-caused false positive signal for intracellular assay.Intracellular delivery of foreign DNA probes sharply increases the efficiency of various biodetection protocols. Spherical nucleic acid (SNA) conjugate is a new type of probe that consists of a dense oligonucleotide shell attached typically to a gold nanoparticle core. They are widely used as novel labels for in vitro biodetection and intracellular assay. However, the degradation of foreign DNA still remains a challenge that can cause significant signal leakage (false positive signal). Hence, the site and behavior of intracellular degradation need to be investigated. Herein, we discover a localized degradation behavior that only excises the first nucleotide of 5′ terminal from a DNA strand, whereas the residual portion of this strand is unbroken in MCF-7 cell. This novel degradation action totally differs from previous opinion that foreign DNA strand would be digested into tiny fragments or even individual nucleotides in cellular environment. On the basis of these findings, we propose a simple and effective way to avoid degradation-caused false positive that one can bypass the degradable site and choose a secure region to label fluorophore along the DNA stand, when using DNA probes for intracellular biodetection.
Co-reporter:Hui Li;Wei Shen;Haojun Liang
New Journal of Chemistry (1998-Present) 2017 vol. 41(Issue 13) pp:5255-5258
Publication Date(Web):2017/06/26
DOI:10.1039/C7NJ00510E
Herein, we designed and prepared two sets of spherical nucleic acid (SNA) nanocarriers to deliver and release microRNA-34a (miR-34a) in MCF-7 breast cancer cells. In this strategy, survivin mRNA was used as a trigger to start the running of the SNA-based delivery system, resulting in the release of miR-34a from the SNA nanocarriers. The quantitative RT-PCR shows a significant decrease in the mRNA level and ectopic expression of miR-34a. Moreover, the released miR-34a mimics largely reduced the cell viability and induced apoptosis, suggesting the high-efficiency and availability of this SNA-based delivery system.
Co-reporter:Elva Ngai-Yu Lei;Man-Shan Yau
Archives of Environmental Contamination and Toxicology 2017 Volume 72( Issue 2) pp:269-280
Publication Date(Web):2017 February
DOI:10.1007/s00244-016-0342-0
The simultaneous profiling of 43 functional metabolites in the brain of the small model vertebrate organism, marine medaka (Oryzais melastigma), has been accomplished via dansyl chloride derivatization and LC–MS/MS quantification. This technique was applied to examine effects of 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47), one of the most abundant polybrominated diphenyl ether flame retardants in the natural environment, on the central nervous system (CNS) of vertebrates. The model teleosts were fed with bioencapsulated Artemia nauplii for up to 21 days. Multivariate statistical analysis has demonstrated that levels of numerous classical neurotransmitters and their metabolites in the CNS of the fish were perturbed even at the early phase of dietary exposure. Subsequent metabolic pathway analysis further implied potential impairment of the arginine and proline metabolism; glycine, serine and threonine metabolism; d-glutamine and d-glutamate metabolism; alanine, aspartate, and glutamate metabolism; valine, leucine, and isoleucine biosynthesis, and the cysteine and methionine metabolism in the brain of the test organism. Our results demonstrate that targeted profiling of functional metabolites in the CNS may shed light on how the various neurological pathways of vertebrates, including humans, are affected by toxicant/stress exposure.
Co-reporter:Peng Hu;Tianshi Feng;Chi-Chung Yeung;Dr. Chi-Kin Koo;Dr. Kai-Chung Lau;Dr. Michael H. W. Lam
Chemistry - A European Journal 2016 Volume 22( Issue 33) pp:11537-11542
Publication Date(Web):
DOI:10.1002/chem.201601807
Abstract
The use of light to control the course of a chemical/biochemical reaction is an attractive idea because of its ease of administration with high precision and fine spatial resolution. Staudinger ligation is one of the commonly adopted conjugation processes that involve a spontaneous reaction between azides and arylphosphines to form iminophosphoranes, which further hydrolyze to give stable amides. We designed an anthracenylmethyl diphenylphosphinothioester (1) that showed promising Staudinger ligation reactivity upon photo-excitation. Broadband photolysis at 360–400 nm in aqueous organic solvents induced heterolytic cleavage of its anthracenylmethyl–phosphorus bond, releasing a diphenylphosphinothioester (2) as an efficient traceless Staudinger–Bertozzi ligation reagent. The quantum yield of such a photo-induced heterolytic bond-cleavage at the optimal wavelength of photolysis (376 nm) at room temperature is ≥0.07. This work demonstrated the feasibility of photocaging arylphosphines to realize the photo-triggering of the Staudinger ligation reaction.
Co-reporter:Xuemin Du, Sharon Hiu-Man Chiu, Daniel Hock-Chun Ong, Roy Vellaisamy, Michael Hon-Wah Lam
Sensors and Actuators B: Chemical 2016 Volume 223() pp:318-323
Publication Date(Web):February 2016
DOI:10.1016/j.snb.2015.09.116
•Polydispersive photonic micro-beads responsive to metal ions have been fabricated.•The photonic diffraction of the beads shifted significantly in 1 mM Cu2+ solution.•A colour tunable electrochemical photonic device was fabricated.•Photonic diffraction colour of the micro-beads was reversibly switched.•Electrochromic photonic beads demonstrate the potential in reflective displays.This work reports a metal ion-responsive photonic colloidal crystalline (PCC) microspheric material and the convenient, reversible switching of its photonic diffraction properties by the redox reaction of copper in a simple electrochemical cell. The PCC micro-beads were fabricated from the orderly three-dimensional packing of core-shell nanoparticles with hydrogel coatings laden with anionic phosphate functionalities. Electrostatic binding of metal cations by the hydrogel coating lowered its internal osmotic pressure and caused shrinkage of the core-shell nanoparticles. This brought about a blue-shift of the photonic diffraction λmax of the micro-beads. The maximum shift, from 650 to 590 nm (colour change from magenta to green) was found to be produced by Cu2+ at a concentration of 1 mM. A simple electrochemical photonic device was constructed by sandwiching a suspension of the photonic micro-beads in 1 mM Cu2+ solution between two transparent ITO-glass electrodes. Photonic diffraction colour of the micro-beads was reversibly switched via the electrochemical reduction/oxidation of Cu2+ inside the device. The colour change can be observed by naked eyes under ambient light. This concept of rapid electrochemical regulation of photonic diffraction colour of PCC micro-beads may be useful in reflective displays applications.This work reports a metal ion-responsive photonic colloidal crystalline (PCC) microspheric material and the convenient, reversible switching of its photonic diffraction properties by the redox reaction of copper in a simple electrochemical cell. This concept of rapid electrochemical regulation of photonic diffraction colour of PCC micro-beads may be useful as pixels in reflective displays applications.
Co-reporter:Hui Li, Shiyan Xiao, Dongbao Yao, Michael Hon-Wah Lam and Haojun Liang
Chemical Communications 2015 vol. 51(Issue 22) pp:4670-4673
Publication Date(Web):10 Feb 2015
DOI:10.1039/C4CC10114F
A design of DNA–gold nanoparticle probe-fueled DNA strand displacements for detecting single-base changes on the platform of a quartz crystal microbalance with random sequences was developed. After optimizing and testing the detection system, it has been successfully applied to detect mutation of a realistic sequence associated with human cancer, thereby indicating that this method has potential applicability in general.
Co-reporter:Yu-Man Ho, Ngan-Pan Bennett Au, Ka-Leung Wong, Chris Tsz-Leung Chan, Wai-Ming Kwok, Ga-Lai Law, Kwong-Kit Tang, Wai-Yeung Wong, Chi-Him Eddie Ma and Michael Hon-Wah Lam
Chemical Communications 2014 vol. 50(Issue 32) pp:4161-4163
Publication Date(Web):03 Jan 2014
DOI:10.1039/C3CC48934E
Real-time tracking of fast axonal transport of acidic vesicles in live adult mouse dorsal root ganglion (DRG) and cortical neurons in brain slices was visualized by the use of binuclear cycloplatinated complexes, {[Pt(L1)]2(μ-dppm)}2+ (1) and {[Pt(L2)]2(μ-dppm)}2+ (2), as lysosome-specific two-photon imaging probes.
Co-reporter:Sheng Cheng, Bin Zheng, Mozhen Wang, Michael Hon-Wah Lam, Xuewu Ge
Analytical Biochemistry 2014 Volume 446() pp:69-75
Publication Date(Web):1 February 2014
DOI:10.1016/j.ab.2013.10.021
Abstract
A strand displacement reaction (SDR) system that runs solely on oligonucleotides has been developed for the amplification detection of adenosine triphosphate (ATP). It involves a target-induced SDR and an entropy-driven catalytic cycle of two SDRs with five oligonucleotides, denoted as substrate, fuel, catalyst, C-1, and C-2. Catalyst, released from the ATP aptamer–catalyst duplex by ATP molecule, catalyzes the SDRs to finally form the substrate–fuel duplex. All of the intermediates in the catalytic SDR processes have been identified by polyacrylamide gel electrophoresis (PAGE) analysis. The introduction of ATP into the SDR system will induce the ATP aptamer to form G-quadruplex conformation so as to release catalyst and trigger the SDR cycle. When the substrate and C-2 oligonucleotides were labeled with a carboxyfluorescein (FAM) fluorophore and a 4-([4-(dimethylamino)phenyl]azo)benzoic acid (DABCYL) quencher, this SDR catalytic system exhibited a “turn-on” response for ATP. The condition for detecting ATP, such as Mg2+ concentration, has been optimized to afford a detection limit of 20 nM. This work provides an enzyme-free biosensing strategy and has potential application in aptamer-based biosensing.
Co-reporter:Xuemin Du, Ngai-Yu Lei, Hiu-Man Chiu, Xuewu Ge, Zhicheng Zhang and Michael Hon-Wah Lam
Journal of Materials Chemistry A 2013 vol. 1(Issue 11) pp:1535-1540
Publication Date(Web):07 Jan 2013
DOI:10.1039/C2TB00236A
Microspherical photonic colloidal crystalline beads that are responsive to media ionic strength of cationic electrolytes have been developed for in vivo imaging of the morphology and concentration gradient of cationic electrolytes along the gastrointestinal (GI) tract of live Japanese medaka (Oryzias latipes). These responsive photonic beads were assembled from core–shell nano-sized particles with polystyrene-co-polyacrylic acid (PS-co-PAA) cores and poly(hydroxyethyl methacrylate-co-p-styrene sulfonate) (PHEMA-co-PSS) hydrogel shells. The three-dimensional orderly packing of these nano-sized core–shell particles gave rise to the photonic properties of the resultant colloidal crystalline array of microspheres. The cationic electrolyte-induced volume phase transition of the sulfonate-laden hydrogel shells of the nano-sized particles altered the lattice spacing among those particles and brought about the photonic responses of the colloidal crystalline beads. Unambiguous changes in the diffraction colour of the colloidal crystalline beads were observable under ordinary ambient light in solution media of increasing concentration of sodium chloride up to 500 mM. These photonic colloidal crystalline beads were found to possess enough structural integrity for in vivo imaging of the GI tract of live Japanese medaka. With the use of a conventional optical microscope, the gradient in the ionic strength of cationic electrolytes along the GI tract of live Japanese medaka larvae was readily revealed, with a lower electrolyte concentration in the mid-intestine (<50 mM) compared to that of the posterior-intestine (≥50 mM). Our results demonstrated the potential of stimuli-responsive photonic materials in bio-imaging applications.
Co-reporter:Xuemin Du, Ngai-Yu Lei, Peng Hu, Zhang Lei, Daniel Hock-Chun Ong, Xuewu Ge, Zhicheng Zhang, Michael Hon-Wah Lam
Analytica Chimica Acta 2013 Volume 787() pp:193-202
Publication Date(Web):17 July 2013
DOI:10.1016/j.aca.2013.05.022
•Fabrication of pH-responsive photonic colloidal crystalline microspheres.•Specific photonic band-gap responses occurred in the pH range of 4–5.•Remarkably low in vivo toxicity to Japanese medaka (Oryzia latipes).•In vivo imaging of the morphology and pH along GI tract of Japanese medaka.•Demonstrates bio-imaging potentials of stimuli-responsive photonic materials.Colloidal crystalline microspheres with photonic band-gap properties responsive to media pH have been developed for in vivo imaging purposes. These colloidal crystalline microspheres were constructed from monodispersed core–shell nano-size particles with poly(styrene-co-acrylic acid) (PS-co-PAA) cores and poly(acrylic acid-co-N-isopropylacrylamide) (PAA-co-PNIPAM) hydrogel shells cross-linked by N,N′-methylenebisacrylamide. A significant shift in the photonic band-gap properties of these colloidal crystalline microspheres was observed in the pH range of 4–5. This was caused by the discontinuous volume phase transition of the hydrogel coating, due to the protonation/deprotonation of its acrylic acid moieties, on the core–shell nano-sized particles within the microspheres. The in vivo imaging capability of these pH-responsive photonic microspheres was demonstrated on a test organism – Japanese medaka, Oryzia latipes – in which the morphology and change in pH along their gastrointestinal (GI) tracts were revealed under an ordinary optical microscope. This work illustrates the potential of stimuli-responsive photonic band-gap materials in tissue-/organ-level in vivo bio-imaging.
Co-reporter:Bin Zheng, Sheng Cheng, Wei Liu, Michael Hon-Wah Lam, Haojun Liang
Analytical Biochemistry 2013 Volume 438(Issue 2) pp:144-149
Publication Date(Web):15 July 2013
DOI:10.1016/j.ab.2013.03.030
Small molecules are difficult to detect by the conventional quartz crystal microbalance with dissipation (QCM-D) technique directly because the changes in frequency resulting from the binding processes of small biomolecules are often small. In the current study, an aptamer-based gold nanoparticles (AuNPs)-enhanced sensing strategy for detection of small molecules was developed. The QCM crystal was first modified with a layer of thiolated linker DNA, which can be partly base-paired with the detection part containing the adenosine aptamer sequence. In the presence of adenosine, the aptamer bound with adenosine and folded to the complex structure, which precluded the reporter part carrying AuNPs to combine with the random coiled detection part. Therefore, the lower the concentration of adenosine, the more AuNPs combined to the crystal. The resulting aptasensor showed a linear response to the increase of the adenosine concentration in the range of 0–2 μM with a linear correlation of r = 0.99148 and a detection limit of 65 nM. Moreover, the aptasensor exhibited several excellent characteristics such as high sensitivity, selectivity, good stability, and reproducibility.
Co-reporter:Sheng Cheng, Bin Zheng, Mozhen Wang, Michael Hon-Wah Lam, Xuewu Ge
Talanta 2013 Volume 115() pp:506-511
Publication Date(Web):15 October 2013
DOI:10.1016/j.talanta.2013.05.065
•A double-functionalized gold nanoparticle-split aptamer system has been developed.•The LSPR response of this system to ATP was much higher than the traditional one.•Time courses of the AuNPs assembly under various systems and conditions were studied.•This newly developed system provided a general way for design of other biosensors.A newly designed functionalization type for gold nanoparticles (AuNP) with split aptamer has been developed for the detection of adenosine triphosphate (ATP). The ATP aptamer was split into two parts with their 5′ prime or 3′ prime modified with thiol. Both the 5′ SH and 3′ SH modified strands for each split aptamer fragment were functionalized onto the same AuNP to construct double-functionalized AuNP–DNA conjugates. Thus, the split aptamer can be reassembled into intact folded structure in the presence of ATP molecule with two potential assembly types, which induces the assembly of AuNP–DNA conjugates. In this double-functionalized system, the traditional assembly type might facilitate another assembly type, which was found to give much higher LSPR change in the presence of ATP than the traditional assembly type, and improve the sensitivity for ATP detection. Time courses of the assemble processes with different assembly types, Mg2+ concentrations, and aptamer fragments densities on AuNP were followed using the absorption ratio at 650 nm and 520 nm. ATP response with this newly designed system was investigated using absorption spectra and dynamic light scattering method.
Co-reporter:Ka-Lok Ho, Margaret B. Murphy, Yi Wan, Bonnie M.-W. Fong, Sidney Tam, John P. Giesy, Kelvin S.-Y. Leung, and Michael H.-W. Lam
Analytical Chemistry 2012 Volume 84(Issue 22) pp:9881
Publication Date(Web):October 17, 2012
DOI:10.1021/ac302161t
Bromophenol glucuronide and sulfate conjugates have been reported to be products of mammalian metabolism of polybrominated diphenyl ethers (PBDEs), a group of additive flame-retardants found ubiquitously in the environment. In order to explore their occurrence in human urine, four water-soluble bromophenol conjugates, namely, 2,4-dibromophenyl glucuronide, 2,4,6-tribromophenyl glucuronide, 2,4-dibromophenyl sulfate, and 2,4,6-tribromophenyl sulfate, were synthesized, purified, and characterized. An analytical protocol using solid-phase extraction and ion-paired liquid chromatography–electrospray tandem mass spectrometry (LC-ESI-MS/MS) quantification has been developed for the direct and simultaneous determination of these glucuronide and sulfate conjugates in human urine samples. The limit of detections for all analytes were below 13 pg mL–1, with 73–101% analyte recovery and 7.2–8.6% repeatability. The method was applied to analyze 20 human urine samples collected randomly from voluntary donors in Hong Kong SAR, China. All the samples were found to contain one or more of the bromophenol conjugates, with concentration ranging from 0.13–2.45 μg g–1 creatinine. To the best of our knowledge, this is the first analytical protocol for the direct and simultaneous monitoring of these potential phase II metabolites of PBDEs in human urine. Our results have also suggested the potential of these bromophenol conjugates in human urine to be convenient molecular markers for the quantification of population exposure to PBDEs.
Co-reporter:Bin Zheng, Sheng Cheng, Wei Liu, Michael Hon-Wah Lam, Haojun Liang
Analytica Chimica Acta 2012 Volume 741() pp:106-113
Publication Date(Web):5 September 2012
DOI:10.1016/j.aca.2012.07.005
Because of their unique characteristics, DNAs have been widely studied for uses in biosensors. In this work, we utilize single-stranded homopolymeric deoxyadenosines (abbreviated as poly (dA)) as recognition elements and gold nanoparticles (abbreviated as AuNPs) as reporter parts for the construction of pH alarms, which are able to produce sharp colorimetric responses upon specific pH thresholds within the range from pH 2 to 4. These biosensors are convenient to prepare and easy to operate. Their pH thresholds for colorimetric response can be easily tuned by changes of DNA strand length, concentration and DNA sequence. With an increase in the number of nucleotide bases per DNA chain while keeping the overall number of nucleotide base in the system constant, the pH threshold can be raised. Increasing the concentration of the single-stranded poly (dA) DNA lowers the pH response threshold. Moreover, as they can sense a range as narrow as a 0.4 pH unit which equals to 2.5 fold [H+] change, they can be used as a potential pH alarm for specific pH range.Graphical abstractHighlights► It is the first time that poly (dA) ssDNAs have been attempted in pH sensing. ► The system can provide very sharp, naked-eyes detectable colorimetric responses upon a specific media pH. ► The approach is simple and detection threshold can be modulated.
Co-reporter:Yu-Man Ho, Chi-Kin Koo, Ka-Leung Wong, Hoi-Kuan Kong, Chris Tsz-Leung Chan, Wai-Ming Kwok, Cheuk-Fai Chow, Michael Hon-Wah Lam and Wai-Yeung Wong
Dalton Transactions 2012 vol. 41(Issue 6) pp:1792-1800
Publication Date(Web):13 Dec 2011
DOI:10.1039/C1DT11037C
Two new C,N,N-type ligands (HL2 and HL3), containing a Cphenyl, a Npyridyl, and a Nimidazolyl donor, and their cycloplatinated complexes, [Pt(L2)Cl] (1), [Pt(L3)Cl] (2), [Pt(L2)(PPh3)]+ (3) and [Pt(L3)(PPh3)]+ (4), have been successfully synthesized and characterized. Spectroscopic and 3MLCT luminescent properties of these Pt(II) cyclometalated complexes were found to be pH dependent. This was attributed to the protonation/deprotonation of the acidic 1-imidazolyl-NH moieties on the ligands. All the cycloplatinated complexes (both protonated and deprotonated forms) possessed two-photon excitability with two-photon absorption cross-sections ranging from 6.0 to 30.0 GM (protonated forms) and from 16.2 to 24.9 GM (deprotonated forms).
Co-reporter:Cheuk-Fai Chow, Hoi-Kuan Kong, Shu-Wai Leung, Brenda K. W. Chiu, Chi-Kin Koo, Elva N. Y. Lei, Michael H. W. Lam, Wing-Tak Wong, and Wai-Yeung Wong
Analytical Chemistry 2011 Volume 83(Issue 1) pp:289
Publication Date(Web):December 7, 2010
DOI:10.1021/ac102393f
Gaseous biogenic amines such as putrescine, spermidine, aniline, and trimethylamine are important biomolecules that play many crucial roles in metabolism and medical diagnostics. A chemodosimetric detection assay has been developed for those gaseous amines by RuII−EuIII heterobimetallic complexes, K{[RuII(tBubpy)(CN)4]2EuIII(H2O)4} (where tBubpy = 4,4′-di-tert-butyl-2,2′-bipyridine). Synthesis, X-ray crystal characterization, and spectroscopic properties of this RuII−EuIII heterobimetallic complex were reported. Binding properties of the RuII−EuIII complex with common gases revealed that this complex is very selective to gaseous amine molecules. Sensitivity of this complex toward the amines was found as ∼log k = 4.5−4.8. Real time monitoring of gaseous biogenic amines was applied to real fish samples (Atlantic mackerel) by studying the spectrofluorimetric responses of the RuII−EuIII complex toward different biogenic amine concentration. GC/MS studies were also used as a reference for the studies. A linear spectrofluorimetric response was found toward biogenic amine concentration in real fish samples. This complex was found to respond specifically to those biogenic amines down to 10 ppb.
Co-reporter:Hui-Min Feng, Jia-Chuan Zheng, Ngai-Yu Lei, Lei Yu, Karen Hoi-Kuan Kong, Han-Qing Yu, Tai-Chu Lau, and Michael H. W. Lam
Environmental Science & Technology 2011 Volume 45(Issue 2) pp:744-750
Publication Date(Web):December 15, 2010
DOI:10.1021/es102182g
Fenton and photoassisted Fenton degradation of ordinary hydrophobic cross-linked polystyrene microspheres and sulfonated polystyrene beads (DOWEX 50WX8) have been attempted. While the Fenton process was not able to degrade these polystyrene materials, photoassisted Fenton reaction (mediated by broad-band UV irradiation from a 250 W Hg(Xe) light source) was found to be efficient in mineralizing cross-linked sulfonated polystyrene materials. The optimal loadings of the Fe(III) catalyst and the H2O2 oxidant for such a photoassisted Fenton degradation were found to be 42 μmol-Fe(III) and 14.1 mmol-H2O2 per gram of the sulfonated polystyrene material. The initial pH for the degradation was set at pH 2.0. This photoassisted Fenton degradation process was also able to mineralize commonly encountered polystyrene wastes. After a simple sulfonation pretreatment, a mineralization efficiency of >99% (by net polymer weight) was achieved within 250 min. The mechanism of this advanced oxidative degradation process was investigated. Sulfonate groups introduced to the surface of the treated polystyrene polymer chains were capable of rapidly binding the cationic Fe(III) catalyst, probably via a cation-exchange mechanism. Such a sorption of the photoassisted Fenton catalyst was crucial to the heterogeneous degradation process.
Co-reporter:Cheuk-Fai Chow, V. A. L. Roy, Zhou Ye, Michael H. W. Lam, C. S. Lee and K. C. Lau
Journal of Materials Chemistry A 2010 vol. 20(Issue 30) pp:6245-6249
Publication Date(Web):15 Jun 2010
DOI:10.1039/C0JM00523A
Liquid crystal based sulfonic acid, 4-(octadecyloxy)phenylsulfonic acid, 1, effectively transports protons at 80 °C under non-humidified conditions. At its smectic A liquid crystal state, the proton conductivity of 1 was measured to be 1.1 × 10−2 S cm−1. The proton conductivities of 1 at its molten and solid powder states were found to be 1.2 × 10−4 and 1.5 × 10−7 S cm−1, respectively. A lamellar structure of bilayer stacks of 1 with the sulfonic acid groups in a head-to-head configuration was found within the monodomain of SmA phase of 1 from in situ XRD and DFT calculation. We proposed that the efficient proton transporting property of 1 is highly correlated to the formation of supramolecular pathways between the molecules at its liquid crystal phase.
Co-reporter:Qingling Li, Michael H.W. Lam, Rudolf S.S. Wu, Biwang Jiang
Journal of Chromatography A 2010 Volume 1217(Issue 8) pp:1219-1226
Publication Date(Web):19 February 2010
DOI:10.1016/j.chroma.2009.12.035
A new Fe3O4/poly(divinylbenzene-co-methacrylic acid) core-shell magnetite microspheric material have been successfully developed as magnetic-mediated solid-phase extraction micro-particle sorbent in dispersion mode (MM-SPE-MP) for the determination of selected estrogenic endocrine disrupting chemicals (EDCs), namely: estrone (E1), 17β-estradiol (E2), estriol (E3), 17α-ethynylestradiol (EE2) and bisphenol-A (BPA), in natural water, via quantification by HPLC tandem mass spectrometry. The magnetite Fe3O4 core of this MM-SPE-MP sorbent was fabricated by a solvothermal approach and the thin layer of amphipolar poly(divinylbenzene-co-methacrylic acid) (pDVB-MAA) coating was established via suspension polymerization. The resultant core-shell MM-SPE-MP sorbent material was characterized by electron microscopy, X-ray diffraction and Fourier-transformed infrared spectroscopy. Particle size distribution of the core-shell microspheres was within the range 300–700 nm in diameter and the thickness of the pDVB-MAA coating was ca. 10 nm. This magnetite microspheric material can be easily dispersed in aqueous samples and retrieved by the application of external magnetic field via a small piece of permanent magnet. The MM-SPE-MP process for the selected estrogenic EDCs involved the dispersion of the core-shell microspheric sorbent in water samples with sonication, followed by magnetic aided retrieval of the sorbent and solvent (methanol) desorption of extracted EDCs for LC–MS/MS analysis. Partition equilibrium for all the selected EDCs onto this MM-SPE-MP sorbent was achieved within 15 min. Recoveries of the EDCs were in ranges of 56–111%. Analytes with smaller KOW value showed relatively lower recovery (and relatively longer equilibration time for partitioning). Method detection limits achieved were found to be 1–36 pg ml−1 (n = 3), while the repeatability was 6–34% (p < 0.05, n = 3). This work demonstrates the usefulness of MM-SPE-MP in the rapid and highly sensitive monitoring of trace organic contaminants in natural waters.
Co-reporter:Chi-Kin Koo;LeoK.-Y. So;Ka-Leung Wong Dr.;Yu-Man Ho;Yun-Wah Lam Dr.;MichaelH.-W. Lam Dr.;Kwok-Wai Cheah Dr.;ChopenChan-Wut Cheng;Wai-Ming Kwok Dr.
Chemistry - A European Journal 2010 Volume 16( Issue 13) pp:
Publication Date(Web):
DOI:10.1002/chem.201090058
Co-reporter:Chi-Kin Koo;LeoK.-Y. So;Ka-Leung Wong Dr.;Yu-Man Ho;Yun-Wah Lam Dr.;MichaelH.-W. Lam Dr.;Kwok-Wai Cheah Dr.;ChopenChan-Wut Cheng;Wai-Ming Kwok Dr.
Chemistry - A European Journal 2010 Volume 16( Issue 13) pp:3942-3950
Publication Date(Web):
DOI:10.1002/chem.200902919
Abstract
An organometallic cyclometalated platinum(II) complex, [Pt(L3)Cl][PF6], has been synthesised from a specially designed cyclometalating ligand, HL3 (triphenyl{5-[3-(6-phenylpyridin-2-yl)-1H-pyrazol-1-yl]pentyl}phosphonium chloride), that contains a pendant carbon chain carrying a terminal cationic triphenylphosphonium moiety. Aside from its room temperature single-photon luminescent properties in solution, [Pt(L3)Cl]+ can also produce two-photon-induced luminescence at room temperature upon excitation at 700 nm from a mode-locked Ti:sapphire laser. Its two-photon absorption cross-section in DMF at room temperature was measured to be 28.0×10−50 cm4 s photon−1. [Pt(L3)Cl]+ is able to selectively stain the cell nucleolus. This has been demonstrated by two-photon confocal imaging of live and methanol-fixed HeLa (human cervical carcinoma) and 3T3 (mouse skin fibroblasts) cells. This organelle specificity is likely to be related to its special affinity for proteins within cell nucleoli. As a result of such protein affinity, [Pt(L3)Cl]+ is an efficient RNA transcription inhibitor and shows rather profound cytotoxicity. On the other hand, the organelle-specific labelling and two-photon-induced luminescent properties of [Pt(L3)Cl]+ renders it a useful nuclear dye for the 3-dimensional reconstruction of optical sections of thick tissues, for example, mouse ileum tissues, by multiphoton confocal microscopy.
Co-reporter:Maggie Ka-Yi Li, Ngai-Yu Lei, Chengbin Gong, Yijun Yu, Ka-Ho Lam, Michael Hon-Wah Lam, Hongxia Yu, Paul Kwan-Sing Lam
Analytica Chimica Acta 2009 Volume 633(Issue 2) pp:197-203
Publication Date(Web):9 February 2009
DOI:10.1016/j.aca.2008.11.060
An organically modified silicate (ORMOSIL) SPME stationary phase molecularly imprinted with BDE-209 has been successfully fabricated by conventional sol–gel technique from phenyltrimethoxysilane and tetraethoxysilane. The thickness of the ORMOSIL-SPME stationary phase, on fused-silica optical fibres, was measured to be ca. 9.5 μm with a volume of ca. 0.12 μL. Rebinding assays and Scatchard analysis revealed that the imprinted ORMOSIL-SPME stationary phase possessed a binding affinity, KB, of 7.3 ± 1.7 × 1010 M−1 for BDE-209, with a receptor site density, Bmax, of 1.2 × 10−3 pmol per SPME device. Besides its molecular template, the ORMOSIL-SPME stationary phase also showed good affinity (log KB ≥ 9.5) for smaller BDE congeners commonly found in the natural environment. The density of receptor sites within the imprinted matrix for those smaller BDE congeners was even higher than that for BDE-209. This may be attributable to the binding site heterogeneity of the imprinting process that creates deformed binding sites that are suitable for the accommodation of the smaller BDE congeners. Compared to the commercially available polyacrylate and polydimethylsiloxane SPME stationary phases, the imprinted ORMOSIL-SPME devices showed much higher pre-concentration ability towards polybrominated diphenyl ethers (PBDEs), even in direct immersion sampling at room temperature. Coupled with GC–NCI-MS and GC-μECD, the imprinted ORMOSIL-SPME device was able to achieve detection sensitivity of 0.2–3.6 pg mL−1 and 1–8.8 pg mL−1, respectively, for commonly occurring BDE congeners, including medium to high molecular weight PBDEs. The imprinted ORMOSIL-SPME device has been successfully applied to monitor PBDE contents in municipal wastewaters.
Co-reporter:Chi-Kin Koo ; Ka-Leung Wong ; Cornelia Wing-Yin Man ; Yun-Wah Lam ; Leo King-Yan So ; Hoi-Lam Tam ; Sai-Wah Tsao ; Kok-Wai Cheah ; Kai-Chung Lau ; Yang-Yi Yang ; Jin-Can Chen
Inorganic Chemistry 2009 Volume 48(Issue 3) pp:872-878
Publication Date(Web):January 7, 2009
DOI:10.1021/ic801261h
The cyclometalated platinum(II) complex [Pt(L)Cl], where HL is a new cyclometalating ligand 2-phenyl-6-(1H-pyrazol-3-yl)pyridine containing Cphenyl, Npyridyl, and Npyrazolyl donor moieties, was found to possess two-photon-induced luminescent properties. The two-photon-absorption cross section of the complex in N,N-dimethylformamide at room temperature was measured to be 20.8 GM. Upon two-photon excitation at 730 nm from a Ti:sapphire laser, bright-green emission was observed. Besides its two-photon-induced luminescent properties, [Pt(L)Cl] was able to be rapidly accumulated in live HeLa and NIH3T3 cells. The two-photon-induced luminescence of the complex was retained after live cell internalization and can be observed by two-photon confocal microscopy. Its bioaccumulation properties enabled time-lapse imaging of the internalization process of the dye into living cells. Cytotoxicity of [Pt(L)Cl] to both tested cell lines was low, according to MTT assays, even at loadings as high as 20 times the dose concentration for imaging for 6 h.
Co-reporter:Chi-Kin Koo ; Ka-Leung Wong ; Cornelia Wing-Yin Man ; Hoi-Lam Tam ; Sai-Wah Tsao ; Kok-Wai Cheah
Inorganic Chemistry 2009 Volume 48(Issue 16) pp:7501-7503
Publication Date(Web):July 21, 2009
DOI:10.1021/ic9007679
An amphiphilic, water-soluble cyclometalated Pt(II) complex with two-photon emission properties has been developed as a molecular marker specific for in vitro plasma membrane staining.
Co-reporter:Chi-Kin Koo Dr.;Ka-Leung Wong Dr.;Kai-Cheung Lau ;Wai-Yeung Wong
Chemistry - A European Journal 2009 Volume 15( Issue 31) pp:7689-7697
Publication Date(Web):
DOI:10.1002/chem.200802703
Abstract
The bis(diphenylphosphino)methane (dppm)-bridged dinuclear cycloplatinated complex {[Pt(L)]2(μ-dppm)}2+ (Pt2⋅dppm; HL: 2-phenyl-6-(1H-pyrazol-3-yl)-pyridine) demonstrates interesting reversible “pivot-hinge”-like intramolecular motions in response to the protonation/deprotonation of L. In its protonated “closed” configuration, the two platinum(II) centers are held in position by intramolecular d8–d8 Pt–Pt interaction. In its deprotonated “open” configuration, such Pt–Pt interaction is cleaved. To further understand the mechanism behind this hingelike motion, an analogous dinuclear cycloplatinated complex, {[Pt(L)]2(μ-dchpm)}2+ (Pt2⋅dchpm) with bis(dicyclohexylphosphino)methane (dchpm) as the bridging ligand, was synthesized. From its protonation/deprotonation responses, it was revealed that aromatic π–π interactions between the phenyl moieties of the μ-dppm and the deprotonated pyrazolyl rings of L was essential to the reversible cleavage of the intramolecular Pt–Pt interaction in Pt2⋅dppm. In the case of Pt2⋅dchpm, spectroscopic and spectrofluorometric titrations as well as X-ray crystallography indicated that the distance between the two platinum(II) centers shrank upon deprotonation, thus causing a redshift in its room-temperature triplet metal–metal-to-ligand charge-transfer emission from 614 to 625 nm. Ab initio calculations revealed the presence of intramolecular hydrogen bonding between the deprotonated and negatively charged 1-pyrazolyl-N moiety and the methylene CH and phenyl C–H of the μ-dppm. The “open” configuration of the deprotonated Pt2⋅dppm was estimated to be 19 kcal mol−1 more stable than its alternative “closed” configuration. On the other hand, the open configuration of the deprotonated Pt2⋅dchpm was 6 kcal mol−1 less stable than its alternative closed configuration.
Co-reporter:Chengbin Gong, Ka-Leung Wong and Michael H. W. Lam
Chemistry of Materials 2008 Volume 20(Issue 4) pp:1353
Publication Date(Web):January 11, 2008
DOI:10.1021/cm7019526
A water-soluble azobenzene-containing functional monomer 4-[(4-methacryloyloxy)phenylazo] benzenesulfonic acid (MAPASA) was developed for the fabrication of a photoresponsive molecularly imprinted hydrogel material that can function in the biocompatible aqueous media. Cross-linking the functional monomer with various bisacrylamide and bismethacrylamide cross-linkers produced polyacrylamide hydrogels with enough optical transparency in the aqueous media for spectroscopic characterization and measurements. Paracetamol, (N-(4-hydroxyphenyl)acetamide), a common analgesic and antipyretic drug, was adopted as the molecular template for the imprinting. Reorientation of the hydrated sulfonated azobenzene chromophores in the course of their trans−cis photoisomerization was found to be sterically demanding. When incorporated into the relatively confined and rigid hydrogel environment generated by the most commonly adopted polyacrylamide cross-linker, N,N′-methylenebisacrylamide (1-C), these chromophores were not able to undergo photoisomerization. Lengthening the spacers separating the polymerizable acrylamide/methacrylamide functionalities at both ends of the cross-linkers from ethylene (2-C) to octylene (8-C) enhanced the flexibility of the resultant hydrogel matrices and resumed the photoisomerization properties of the chromophores. The rate of photoisomerization gradually increased with spacer length. On the other hand, substrate binding strength of the imprinted receptors dropped with the increasing flexibility of the hydrogels. Balancing these factors, the cross-linker N,N′-hexylenebismethacrylamide (6-C) was subsequently selected as the optimal cross-linker for the fabrication of the photoresponsive imprinted hydrogel. Scatchard analysis revealed the specific and nonspecific binding strength of the resultant imprinted hydrogel to be 1.96 × 105 and 747.0 M−1, respectively. The density of the imprinted receptors in the hydrogel was 0.47 µmol g−1. The affinity of the hydrogel for paracetamol can be photoregulated. Upon irradiation at 353 nm, 83.6% of receptor-bound paracetamol was released from the imprinted hydrogel. Subsequent irradiation at 440 nm caused 94.1% of the released paracetamol to be rebound by the hydrogel again. Such a photoregulated release and uptake process is repeatable. Results of our work demonstrated the potential of stimuli-responsive molecularly imprinted materials as biocompatible smart chemicals and drugs transfer systems.
Co-reporter:Ka-Leung Wong, Ga-Lai Law, Margaret B. Murphy, Peter A. Tanner, Wing-Tak Wong, Paul Kwan-Sing Lam and Michael Hon-Wah Lam
Inorganic Chemistry 2008 Volume 47(Issue 12) pp:5190-5196
Publication Date(Web):May 21, 2008
DOI:10.1021/ic8000416
Emissive europium hydroxide nanorods (ENR) (20 nm × 500 nm) functionalized by a surface coating of chromophore-containing organically modified silicate (ORMOSIL) layer, have been synthesized and characterized by high-resolution transmission electron microscopy (TEM). Low-temperature photophysical characterization of the functionalized nanorods (FENR) demonstrated a strong red 5D0 luminescence both in solid and in suspended solutions. Potentials of this nanorod material for live cell imaging have also been explored. Both the bare and functionalized nanorods are able to enter living human cells with no discernible cytotoxicity. Chromophore-to-Eu3+ energy-transfer in the functionalized nanorods enables staining of the cytoplasm of living human cells. This is confirmed by costaining with fluorescent dextran. The red chromophore-sensitized luminescence from the internalized nanorods in live human lung carcinoma cells (A549) can be observed by confocal microscopy 2 h after loading and reaches maximal emission after 24 h.
Co-reporter:Chi-Kin Koo;Cheuk-Fai Chow;Brenda Ka-Wen Chiu;Ngai-Yu Lei;Wai-Yeung Wong
European Journal of Inorganic Chemistry 2008 Volume 2008( Issue 8) pp:1318-1325
Publication Date(Web):
DOI:10.1002/ejic.200700931
Abstract
A chemosensing approach utilizing a pair of heterodimetallic chemodosimetric ensembles of different analyte selectivity for the specific detection of targeted analytes in aqueousmedia was developed. Two new trinuclear, heterodimetallic donor–acceptor complexes, {Ru(tBubpy)(CN)4[Cu(cyclen)]2}(ClO4)2 ([Ru-Cu]) and {Ru(tBubpy)(CN)4[Ni(cyclen)]2}(ClO4)2([Ru-Ni]), where tBubpy = 4,4′-di-tert-butyl-2,2′-bipyridine and cyclen = 1,4,7,10-tetraazacyclododecane, have been synthesized and characterized. Their formation constants from K2[Ru(tBubpy)(CN)4] and [Cu(cyclen)](ClO4)2 and [Ni(cyclen)](ClO4)2 were measured to be 5.54 × 106 ([Ru-Cu]) and 1.24 × 107M–2 ([Ru-Ni]), respectively, at 298 K. Luminescent chemodosimetric responses of these two ensembles towards various anionic analytes in neat aqueous buffer at pH 7.0 were evaluated. While each of these two ensembles showed relatively low analyte specificity, they can be used together to manifest a chemosensing XOR logic output for the specific detection of tartrate. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Co-reporter:C. B. Gong;M. H.-W. Lam;H. X. Yu
Advanced Functional Materials 2006 Volume 16(Issue 13) pp:
Publication Date(Web):31 JUL 2006
DOI:10.1002/adfm.200500907
A photoresponsive molecularly imprinted polymer (MIP) material is successfully fabricated from an azobenzene-based functional monomer, 4-[(4-methacryloyloxy)phenylazo]benzoic acid (MPABA), using caffeine as a molecular template. The trans–cis photoisomerization properties of MPABA are retained after incorporation into the rigid 3D crosslinked polymer matrix. Substrate affinity of the MIP receptor sites is photoswitchable. This can be attributed to the photoisomerization of azobenzene chromophores within the MIP receptors, resulting in the alteration of their geometry and the spatial arrangement of their binding functionalities. The favorable binding constant of the MIP receptors for caffeine is 5.48 × 104 M–1 in dimethylsulfoxide. The density of the caffeine-specific receptor sites in the MIP material is 0.95 μmol (g MIP)–1. Upon irradiation at 365 nm, 58.3 % of receptor-bound caffeine is released from the MIP material. Subsequent irradiation at 440 nm causes 96.4 % of the released caffeine to be rebound by the MIP material. This near-quantitative uptake of the released caffeine is evidence of the reversibility of the receptor-site configuration and substrate affinity during the photoswitching of the azobenzene chromophores. Although the photoregulated substrate release and uptake processes are generally repeatable, a gradual reduction in the extent of substrate release and rebinding is observed. This may be caused by the slow deformation of MIP receptors during the course of repetitive photoswitching. The results of this work demonstrate the potential of stimuli-responsive MIP materials as smart chemicals and as drug-delivery systems.
Co-reporter:Ivy O. M. Chan, Paul K. S. Lam, Richard H. Y. Cheung, Michael H. W. Lam and Rudolf S. S. Wu
Analyst 2005 vol. 130(Issue 11) pp:1524-1529
Publication Date(Web):09 Sep 2005
DOI:10.1039/B506324H
A SPME–HPLC–post-column fluorescent derivatization method for the direct determination of saxitoxin (STX), the most potent paralytic shellfish poisoning (PSP) toxin, in water has been developed. Commercially available SPME devices with 50 µm Carbowax templated resin (CW/TPR) coating was found to be able to pre-concentrate STX from aqueous media. A special pre-conditioning treatment of soaking the SPME coating in 0.1 M NaOH solution significantly improved the extraction efficiency. The optimal pH for the SPME process is 8.1 and the equilibration time is 40 min. The partition coefficient, K, of the distribution of STX between the SPME coating and the aqueous media was measured to be 2.99 ± 0.04 × 103. Extracted toxin on the SPME stationary phase was difficult to be desorbed by the HPLC mobile phase under dynamic desorption mode. A static ion-pairing desorption technique using a desorption solvent mixture of 20 mM sodium 1-heptanesulfonate in 30% aqueous acetonitrile acidified with 50 mM sulfuric acid was developed to overcome this problem. The method detection limit and repeatability achieved by this SPME–HPLC method were 0.11 ng ml−1 and 3.7%, respectively, with a sample volume of just 5 ml of water. This analytical method is adequate for the monitoring of the PSP toxin in fresh/drinking waters. However, serious interference was observed when this technique was applied to saline water samples. This is probably due to competition of sodium ions with the cationic STX for absorption into the SPME stationary phase.
Co-reporter:HongXia Yu, Ben Kwok-Wai Man, Lily Lee-Ni Chan, Michael Hon-Wah Lam, Paul K.S. Lam, Liansheng Wang, Hongjun Jin, Rudolf S.S. Wu
Analytica Chimica Acta 2004 Volume 509(Issue 1) pp:63-70
Publication Date(Web):29 April 2004
DOI:10.1016/j.aca.2003.12.019
Co-reporter:Brenda Ka-Wen Chiu, Michael Hon-Wah Lam, Derek Yiu-Kin Lee, Wai-Yeung Wong
Journal of Organometallic Chemistry 2004 Volume 689(Issue 18) pp:2888-2899
Publication Date(Web):15 September 2004
DOI:10.1016/j.jorganchem.2004.06.006
A series of mononuclear and binuclear cyclometalated platinum(II) complexes containing new terdentate meta-bis(2-pyridoxy)benzene ligands: 3,5-bis(2-pyridoxy)toluene (L1H) and 3,5-bis(2-pyridoxy)-2-dodecylbenzene (L2H): [Pt(L1)Cl] (1), [Pt(L2)Cl] (2), [Pt(L1)(CH3CN)](ClO4) (3), {[Pt(L1)]2(μ-dppm)}(ClO4)2 (4), {[Pt(L2)]2(μ-dppm)}(ClO4)2 (5), {[Pt(L1)]2(μ-pyrazole)}(ClO4) (6), {[Pt(L2)]2(μ-pyrazole)}(ClO4) (7), {[Pt(L1)]2(μ-imidazole)}(ClO4) (8) and {[Pt(L2)]2(μ-imidazole)}(ClO4) (9), have been synthesized and characterized. These ligands are coordinated to platinum(II) in a “pincer”-like manner and the presence of pyridyl donors enhances the availability of the ligand π∗ orbitals for electronic transition. Spectroscopic properties of these cyclometalated complexes were studied. While the non-coplanar nature of the ligands hinders ligand–ligand and metal–metal interactions in these cyclometalated complexes, the presence of long hydrocarbon side chain on ligand L2H seems to alleviate such hindrance. Intermolecular π–π, and possibly Pt–Pt interactions were observed in complex 2 at high concentration.A series of mononuclear and binuclear cyclometalated platinum(II) complexes containing new “pincer-like” terdentate meta-bis(2-pyridoxy)benzene ligands have been synthesized, characterized and their spectroscopic properties studied.
Co-reporter:Derek Y. K. Lee, Michael H. W. Lam and Wai-Yeung Wong
New Journal of Chemistry 2002 vol. 26(Issue 3) pp:330-335
Publication Date(Web):28 Feb 2002
DOI:10.1039/B108087N
Luminescent properties of the supramolecular complex, [Re(bpy)(CO)3{py-CH[CH(COOMe)2]2}]+
(3, bpy=2,2′-bipyridine), containing a novel ionophore precursor, py-CH[CH(COOMe)2]2
(1), with two adjacent dimethyl malonate moieties joined together by a pyridine substituted methylene bridge, are found to respond selectively to Ba2+ upon deprotonation of the two malonate moieties.
Co-reporter:Mitch K.-P. Leung, Cheuk-Fai Chow and Michael H.-W. Lam
Journal of Materials Chemistry A 2001 vol. 11(Issue 12) pp:2985-2991
Publication Date(Web):24 Sep 2001
DOI:10.1039/B103182C
A novel sol–gel derived molecular imprinted luminescent sensing material has been fabricated by a conventional sol–gel process. 2,4-Dichlorophenoxyacetic acid (2,4-D) was used as template for the imprinting process and a tailor-made organosilane, 3-[N,N-bis(9-anthrylmethyl)amino]propyltriethoxysilane (1), was used as the functional monomer. Luminescent properties of 1 were perturbed by acid–base ion-pair formation with 2,4-D leading to suppression of photoinduced electron transfer (PET) quenching of its anthryl fluorophores. Such PET fluorescent response was preserved after the preorganized monomer–template aggregates were cross-linked by a sol–gel process. The resultant sol–gel derived luminescent material was found to selectively respond to 2,4-D in aqueous media at pH 7. Average binding affinity
of recognition sites in the material for 2,4-D was estimated to be (2.23 ± 0.5) × 106 M−1. Selectivity of the MIP was also evaluated. The present study demonstrated the feasibility of using a PET mechanism as a means of signal transduction for molecular imprinted polymer (MIP) based luminescent sensing of non-fluorescent analytes.
Co-reporter:Michael H. W. Lam, Derek Y. K. Lee, K. W. Man and Cindy S. W. Lau
Journal of Materials Chemistry A 2000 vol. 10(Issue 8) pp:1825-1828
Publication Date(Web):06 Jul 2000
DOI:10.1039/B001914N
A rhenium(I) tricarbonyl complex with a
3-(pyridin-2-yl)pyrazole chromophoric ligand and a functionalized
organosilane spectator ligand, [Re(py-pzH)(CO)3(L1)](CF3SO3)
(1) [where py-pzH = 3-(pyridin-2-yl)pyrazole,
L1
= 3-N-(pyridin-4-ylmethylene)aminopropyltriethoxysilane],
as well as its analog, [Re(py-pzH)(CO)3(py)](CF3SO3)
(2)
(where py = pyridine)
have been synthesized. The room temperature MLCT luminescence properties of 1 and 2
(λmax
at 484 and 489 nm, respectively) were found to be sensitive to
the protonation–deprotonation status of the 3-(pyridin-2-yl)pyrazole
ligand. Spectrofluorometric pH titration of 2
in aqueous media revealed an excited state pKa of 7.05.
Sol–gel material formed from hydrolysis of 1
was successfully spin-coated onto glass microscope slides. The result
was a sol–gel based luminescent pH sensor capable of responding over
a wide pH range from pH 2.3 to 12 in air. The applicability of the
principle of direct perturbation of electronic factors of sensor molecules
in the development of luminescent chemical sensing materials is demonstrated.
Co-reporter:Michael H. W. Lam;Derek Y. K. Lee;Sammi S. M. Chiu;K. W. Man;W. T. Wong
European Journal of Inorganic Chemistry 2000 Volume 2000(Issue 7) pp:
Publication Date(Web):4 JUL 2000
DOI:10.1002/1099-0682(200007)2000:7<1483::AID-EJIC1483>3.0.CO;2-X
A new multidentate ligand L, 1,2-bis{[3-(2-pyridyl)pyrazol-1-yl]ethoxy}ethane, has been synthesized by linking two 3-(pyridin-2-yl)pyrazoles with a 1,2-bis(ethoxy)ethyl spacer. Coordination of L with zinc(II) and europium(III) centres has led to mononuclear complexes of [Zn(L)](ClO4)2 (1) and [Eu(L)Cl2](ClO4) (2). X-ray crystal structures of both complexes have shown that L adopted a helical coordination geometry around both metal centres. The spectroscopic properties of both complexes have also been determined. In 1, photoluminescence was dominated by ligand centred 1(π-π*) fluorescence. In 2, ligand-to-metal energy transfer leading to 5D0 7Fn luminescence at the europium(III) centre was observed.
Co-reporter:Ka-Lok Ho, Ka-Ki Yuen, Man-Shan Yau, Margaret B. Murphy, Yi Wan, Bonnie M.-W. Fong, Sidney Tam, John P. Giesy, Kelvin S.-Y. Leung, Michael H.-W. Lam
Environment International (January 2017) Volume 98() pp:46-53
Publication Date(Web):1 January 2017
DOI:10.1016/j.envint.2016.09.018
•The first report on the synthesis & purification of Phase II metabolites of TBBPA.•Reveals correlations among TBBPA and its metabolites in human plasma and urine.•Contributes to the establishment of convenient TBBPA population exposure markers.3,3′,5,5′-Tetrabromobisphenol-A (TBBPA) is an important brominated flame retardant in epoxy, vinyl esters and polycarbonate resins. Previous studies have already shown the occurrence of its Phase II metabolites, TBBPA-glucuronide and sulfate conjugates, in human urine, after oral administration of TBBPA. The main objective of this work is to examine correlations among level of TBBPA in human blood and those of its Phase II metabolites in human urine. Four water-soluble TBBPA conjugates were synthesized, purified and characterized. An analytical protocol using solid-phase extraction and liquid chromatography–electrospray tandem mass spectrometry (SPE-LC-MS/MS) quantification was developed for the simultaneous analysis of these glucuronide and sulfate conjugates in human urine samples. TBBPA and its Phase II metabolites in paired human plasma and urine samples collected randomly from 140 voluntary donors in Hong Kong SAR, China, were determined. One or more TBBPA conjugates were detected in all of the urine samples, with concentration ranging from 0.19 to 127.24 μg g− 1-creatinine. TBBPA was also quantified in > 85% of the plasma and urine samples. Strong correlations were observed between TBBPA content in plasma and the total amount of TBBPA-related compounds in urine.Download high-res image (96KB)Download full-size image
Co-reporter:Xuemin Du, Ngai-Yu Lei, Hiu-Man Chiu, Xuewu Ge, Zhicheng Zhang and Michael Hon-Wah Lam
Journal of Materials Chemistry A 2013 - vol. 1(Issue 11) pp:NaN1540-1540
Publication Date(Web):2013/01/07
DOI:10.1039/C2TB00236A
Microspherical photonic colloidal crystalline beads that are responsive to media ionic strength of cationic electrolytes have been developed for in vivo imaging of the morphology and concentration gradient of cationic electrolytes along the gastrointestinal (GI) tract of live Japanese medaka (Oryzias latipes). These responsive photonic beads were assembled from core–shell nano-sized particles with polystyrene-co-polyacrylic acid (PS-co-PAA) cores and poly(hydroxyethyl methacrylate-co-p-styrene sulfonate) (PHEMA-co-PSS) hydrogel shells. The three-dimensional orderly packing of these nano-sized core–shell particles gave rise to the photonic properties of the resultant colloidal crystalline array of microspheres. The cationic electrolyte-induced volume phase transition of the sulfonate-laden hydrogel shells of the nano-sized particles altered the lattice spacing among those particles and brought about the photonic responses of the colloidal crystalline beads. Unambiguous changes in the diffraction colour of the colloidal crystalline beads were observable under ordinary ambient light in solution media of increasing concentration of sodium chloride up to 500 mM. These photonic colloidal crystalline beads were found to possess enough structural integrity for in vivo imaging of the GI tract of live Japanese medaka. With the use of a conventional optical microscope, the gradient in the ionic strength of cationic electrolytes along the GI tract of live Japanese medaka larvae was readily revealed, with a lower electrolyte concentration in the mid-intestine (<50 mM) compared to that of the posterior-intestine (≥50 mM). Our results demonstrated the potential of stimuli-responsive photonic materials in bio-imaging applications.
Co-reporter:Cheuk-Fai Chow, V. A. L. Roy, Zhou Ye, Michael H. W. Lam, C. S. Lee and K. C. Lau
Journal of Materials Chemistry A 2010 - vol. 20(Issue 30) pp:NaN6249-6249
Publication Date(Web):2010/06/15
DOI:10.1039/C0JM00523A
Liquid crystal based sulfonic acid, 4-(octadecyloxy)phenylsulfonic acid, 1, effectively transports protons at 80 °C under non-humidified conditions. At its smectic A liquid crystal state, the proton conductivity of 1 was measured to be 1.1 × 10−2 S cm−1. The proton conductivities of 1 at its molten and solid powder states were found to be 1.2 × 10−4 and 1.5 × 10−7 S cm−1, respectively. A lamellar structure of bilayer stacks of 1 with the sulfonic acid groups in a head-to-head configuration was found within the monodomain of SmA phase of 1 from in situ XRD and DFT calculation. We proposed that the efficient proton transporting property of 1 is highly correlated to the formation of supramolecular pathways between the molecules at its liquid crystal phase.
Co-reporter:Yu-Man Ho, Chi-Kin Koo, Ka-Leung Wong, Hoi-Kuan Kong, Chris Tsz-Leung Chan, Wai-Ming Kwok, Cheuk-Fai Chow, Michael Hon-Wah Lam and Wai-Yeung Wong
Dalton Transactions 2012 - vol. 41(Issue 6) pp:NaN1800-1800
Publication Date(Web):2011/12/13
DOI:10.1039/C1DT11037C
Two new C,N,N-type ligands (HL2 and HL3), containing a Cphenyl, a Npyridyl, and a Nimidazolyl donor, and their cycloplatinated complexes, [Pt(L2)Cl] (1), [Pt(L3)Cl] (2), [Pt(L2)(PPh3)]+ (3) and [Pt(L3)(PPh3)]+ (4), have been successfully synthesized and characterized. Spectroscopic and 3MLCT luminescent properties of these Pt(II) cyclometalated complexes were found to be pH dependent. This was attributed to the protonation/deprotonation of the acidic 1-imidazolyl-NH moieties on the ligands. All the cycloplatinated complexes (both protonated and deprotonated forms) possessed two-photon excitability with two-photon absorption cross-sections ranging from 6.0 to 30.0 GM (protonated forms) and from 16.2 to 24.9 GM (deprotonated forms).
Co-reporter:Yu-Man Ho, Ngan-Pan Bennett Au, Ka-Leung Wong, Chris Tsz-Leung Chan, Wai-Ming Kwok, Ga-Lai Law, Kwong-Kit Tang, Wai-Yeung Wong, Chi-Him Eddie Ma and Michael Hon-Wah Lam
Chemical Communications 2014 - vol. 50(Issue 32) pp:NaN4163-4163
Publication Date(Web):2014/01/03
DOI:10.1039/C3CC48934E
Real-time tracking of fast axonal transport of acidic vesicles in live adult mouse dorsal root ganglion (DRG) and cortical neurons in brain slices was visualized by the use of binuclear cycloplatinated complexes, {[Pt(L1)]2(μ-dppm)}2+ (1) and {[Pt(L2)]2(μ-dppm)}2+ (2), as lysosome-specific two-photon imaging probes.
Co-reporter:Hui Li, Shiyan Xiao, Dongbao Yao, Michael Hon-Wah Lam and Haojun Liang
Chemical Communications 2015 - vol. 51(Issue 22) pp:NaN4673-4673
Publication Date(Web):2015/02/10
DOI:10.1039/C4CC10114F
A design of DNA–gold nanoparticle probe-fueled DNA strand displacements for detecting single-base changes on the platform of a quartz crystal microbalance with random sequences was developed. After optimizing and testing the detection system, it has been successfully applied to detect mutation of a realistic sequence associated with human cancer, thereby indicating that this method has potential applicability in general.
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![2-Propenoic acid, 2-methyl-, 4-[2-(4-sulfophenyl)diazenyl]phenyl ester](/data/chemimg/1643800/1005792-99-3_b.png)
![[(3aS,4R,9R)-2,6-diamino-10,10-dihydroxy-9-(sulfooxy)-3a,4,9,10-tetrahydro-3H,8H-pyrrolo[1,2-c]purin-4-yl]methyl carbamate](http://img.cochemist.com/ccimg/60600/60508-89-6.png)
![[(3aS,4R,9R)-2,6-diamino-10,10-dihydroxy-9-(sulfooxy)-3a,4,9,10-tetrahydro-3H,8H-pyrrolo[1,2-c]purin-4-yl]methyl carbamate](http://img.cochemist.com/ccimg/60600/60508-89-6_b.png)
![({[(3aS,4R,9R)-2,6-diamino-10,10-dihydroxy-9-(sulfooxy)-3a,4,9,10-tetrahydro-3H,8H-pyrrolo[1,2-c]purin-4-yl]methoxy}carbonyl)sulfamic acid](http://img.cochemist.com/ccimg/80200/80173-30-4.png)
![({[(3aS,4R,9R)-2,6-diamino-10,10-dihydroxy-9-(sulfooxy)-3a,4,9,10-tetrahydro-3H,8H-pyrrolo[1,2-c]purin-4-yl]methoxy}carbonyl)sulfamic acid](http://img.cochemist.com/ccimg/80200/80173-30-4_b.png)
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![hydrogen (3aS,4R,9S,10aS)-2,6-diamino-4-[(carbamoyloxy)methyl]-10,10-dihydroxy-3a,4,9,10-tetrahydro-3H,8H-pyrrolo[1,2-c]purin-9-yl sulfate](http://img.cochemist.com/ccimg/60600/60537-65-7.png)
![hydrogen (3aS,4R,9S,10aS)-2,6-diamino-4-[(carbamoyloxy)methyl]-10,10-dihydroxy-3a,4,9,10-tetrahydro-3H,8H-pyrrolo[1,2-c]purin-9-yl sulfate](http://img.cochemist.com/ccimg/60600/60537-65-7_b.png)
![[(3aS,4R,6Z,9R)-2-amino-5,10,10-trihydroxy-6-imino-9-(sulfooxy)-3a,4,5,6,9,10-hexahydro-3H,8H-pyrrolo[1,2-c]purin-4-yl]methyl carbamate](http://img.cochemist.com/ccimg/60800/60748-39-2.png)
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![{[(1R,2S,4R,6R)-1-METHYL-7-OXABICYCLO[4.1.0]HEPTANE-2,4-DIYL]BIS(<WBR />OXY)}BIS[DIMETHYL(2-METHYL-2-PROPANYL)SILANE]](http://img.cochemist.com/ccimg/324800/324753-11-9.png)
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