There is increasing evidence indicating that lysosomal H2O2 is closely related to autophagy and apoptotic pathways under both physiological and pathological conditions. Therefore, fluorescent probes that can be exploited to visualize H2O2 in lysosomes are potential tools for exploring diverse roles of H2O2 in cells. However, functional exploration of lysosomal H2O2 is limited by the lack of fluorescent probes capable of compatibly sensing H2O2 under weak acidic conditions (pH = 4.5) of lysosomes. Lower spatial resolution of the fluorescent visualization of lysosomal H2O2 might be caused by the interference of signals from cytosolic and mitochondrial H2O2, as well as the non-specific distribution of the probes in cells. In this work, we developed a lysosome-locating and acidic-pH-activatable fluorescent probe for the detection and visualization of H2O2 in lysosomes, which consists of a H2O2-responsive boronate unit, a lysosome-locating morpholine group, and a pH-activatable benzorhodol fluorophore. The response of the fluorescent probe to H2O2 is significantly more pronounced under acidic pH conditions than that under neutral pH conditions. Notably, the present probe enables the fluorescence sensing of endogenous lysosomal H2O2 in living cells without external stimulations, with signal interference from the cytoplasm and other intracellular organelles being negligible.

Inspired by the primitive role of lipopolysaccharide (LPS) and taking advantage of the membrane-philic properties of amphiphilic gold nanoparticles (AuNPs), we established a facile and efficient fluorescence turn-on detection strategy for LPS. Upon binding onto the surface of liposomes, LPS can tailor the accessibility of liposomes towards AuNPs, reminiscent of its primitive function on the surface of bacteria. Thus, while the fluorescence of the dyes labeled on liposomes can be markedly quenched by the membrane-philic AuNPs, the quenching effect can be efficiently prevented by the surface-bound LPS. The de-quenching effect is highly selective to LPS, relative to other negatively charged bio-analytes, which is due to not only the extremely high affinity of LPS to lipid bilayers, but also the unique molecular structure of LPS. Furthermore, this easy-to-construct method offers a limit of detection of ∼0.65 nM, which is comparable to that obtained from the superb synthetic sensors for LPS reported in the literature. This study would open up a new route for the design of sensing systems for LPS exploiting its unique structural pattern and primitive function.

Intracellular H2O2 plays an important role in regulating a variety of cellular functions. Fluorescent probes that can make response to intracellular levels of H2O2 would provide valuable tools for revealing the functions of H2O2 in living organisms. However, traditional pH-insensitive probes and lysosome-targetable probes can only provide spatially nonspecific visualization of intracellular H2O2 and specific sensing of lysosomal H2O2, respectively. In this work, we developed a H2O2-responsive and pH-switchable fluorescent probe (HP-L1) which can make response sequentially to intracellular H2O2 and lysosomal pH. The fluorescent probe is comprised of a H2O2-responsive boronate moiety and a pH-switchable spirobenzopyran fluorophore. When the probe was applied for intracellular H2O2 sensing, only fluorescent emission from lysosomes is visible, and the fluorescence from other regions is not able to be obviously detected, which is due to the pH-switchable property of the spirobenzopyran fluorophore. Thus, the developed fluorescence probe enables the spatially confined (i.e., lysosome-specific) visualization of the intracellular H2O2. We envisioned that this kind of fluorescent probe (or the proposed sensing strategy) would allow the visualization of the overall levels of intracellular H2O2 without interferences of possible fluorescent signals from other sources (e.g., dyes for cellular staining and multiplex analysis).

The presence of large hydrophobic aromatic residues in cell-penetrating peptides or proteins has been demonstrated to be advantageous for their cell penetration. This phenomenon has also been observed when AuNPs were modified with peptides containing aromatic amino acids. However, it is still not clear how the presence of hydrophobic and aromatic groups on the surface of anionic AuNPs affects their interaction with lipid bilayers. Here, we studied the interaction of a range of anionic amphiphilic AuNPs coated by different combinations of hydrophobic and anionic ligands with four different types of synthetic lipid vesicles. Our results demonstrated the important role of the surface aromatic or bulky groups, relative to the hydrocarbon chains, in the interaction of anionic AuNPs with lipid bilayers. Hydrophobic interaction itself arising from the insertion of aromatic/bulky ligands on the surface of AuNPs into lipid bilayers is sufficiently strong to cause overt disruption of lipid vesicles and cell membranes. Moreover, by comparing the results obtained from AuNPs coated with aromatic ligands and cyclohexyl ligands lacking aromaticity respectively, we demonstrated that the bulkiness of the terminal groups in hydrophobic ligands instead of the aromatic character might be more important to the interaction of AuNPs with lipid bilayers. Finally, we further correlated the observation on model liposomes with that on cell membranes, demonstrating that AuNPs that are more disruptive to the more negatively charged liposomes are also substantially more disruptive to cell membranes. In addition, our results revealed that certain cellular membrane domains that are more susceptible to disruption caused by hydrophobic interactions with nanoparticle surfaces might determine the threshold of AuNP-mediated cytotoxicity.

We have developed conjugated copolymer–photosensitizer molecular hybrids (PFBDBP–IPBP) with a strong, broad (from <400 nm to ∼700 nm) and continuous visible absorption. The photosensitizing ability of PFBDBP–IPBP was demonstrated to be higher than that of the monochromophore-based IPBP, owing to rational manipulation of the multiple intramolecular energy transfer. In addition, we demonstrated that the developed PFBDBP–IPBP displays excellent photostability compared to the IPBP.

The sensing of lipopolysaccharide (LPS) relies on the synergy of multiple electrostatic and hydrophobic interactions between LPS and the sensor. However, how non-covalent interactions are coordinated to impel the recognition process still remains elusive, and the exploration of which would promote the development of LPS sensors with higher specificity and sensitivity. In this work, we hypothesize that Au NPs would provide a straightforward and flexible platform for studying the synergy of non-covalent interactions. The detailed mechanism of interactions between the designed fluorescent probes and Au NPs with two distinct surface properties was systematically explored. We demonstrated that only when the electrostatic attraction and hydrophobic stacking are both present, the binding of fluorescent probes onto Au NPs can be not only highly efficient, but also positively cooperative. After that, hybrid systems that consist of Au NPs and surface-assembled fluorescent probes were exploited for fluorescent turn-on sensing of LPS. The results show that the sensitivity and selectivity to LPS relies strongly on the binding affinity between fluorescent probes and Au NPs. Fluorescent probes assembled Au NPs thus provide an attractive platform for further optimization of the sensitivity/selectivity of LPS sensing.

UV light irradiation triggers Au NPs that are respectively functionalized on the surface by o-nitrobenzyl alcohol and benzylamine to proceed with a covalent ligation reaction, which leads to assembling of Au NPs into anisotropic one-dimensional (1D) arrays in aqueous solution viaindazolone linkages.

A general and facile approach was developed for the synthesis of almost monodisperse fluorescent silica nanoparticles (NPs) doped with inert dyes, which are organic fluorophores that are strongly fluorescent but are hydrophobic or lack a covalent binding group. The prepared NPs were mesoporous and the dye molecules were encapsulated in the pores via hydrophobic interaction with the CTAB template. The NPs were stable and highly fluorescent in aqueous solution, and have potential applications in bioanalysis and fluorescence encoding.

Water-soluble mercaptoacetic acid-coated 3.1 nm CdS quantum dots (QDs) with two concentrations were selected for studying the correlation between the photoluminescence and the crystal growth mechanism. By achieving the classic Ostwald ripening mechanism and oriented attachment (OA) growth mechanism, we have shown that the evolution of the emission spectra were obviously different. The change in both the surface and internal defects during OA crystal growth were responsible for the specific variation of the photoluminescence of CdS QDs. Strategies for obtaining QDs with different luminescent properties are suggested.

Mesoporous silica nanoparticles grafted with light-responsive polymer on the outer surface were developed as novel nanogated ensembles, which allow encapsulation and release of drug and biological molecules under light irradiation.

Au NRs protected with mPEG-SH molecules (mPEG-Au NRs) were demonstrated to be a promising platform for LSPR-based sensing of molecular biothiols in aqueous solution. Surface mPEG-SH molecules endow Au NRs with great stability and biocompatibility and no nonspecific adsorption of biomacromolecules. The LSPR band of mPEG-Au NRs displays a stability and linear response in the spectral shift with respect to a change in their surrounding refractive index with a sensitivity of 252 nm/RIU. The loose structure of mPEG-SH around the Au NRs offers free sites, thereby allowing molecular biothiols to bind onto the surfaces of Au NRs. The LSPR response and the sensitivity of Au NRs to biothiols such as GSH, Cys, Hcy, TGA, GSSG, and BSA were then studied.

The structures of multi-wall carbon nanotubes (MWNTs) were modified by H2SO4–HNO3 and H2SO4–H2O2, respectively. The corresponding products were water-soluble MWNTs-A and MWNTs-B. According to the experiment, it was found that MWNTs-B could emit stable solid substrate-room temperature phosphorescence (RTP) on the surface of paper with Ag+ as perturber. Under the conditions of 70 °C and 15 min, MWNTs-B can react with Tween-80 and p-nitro-phenyl-fluorone (R) to form R-MWNTs-B–Tween-80 micellae compound, which could emit RTP of R and MWNTs-B on the surface of paper, respectively. Pb2+ could cause the RTP of R and MWNTs-B enhanced sharply, respectively. ΔIp is directly proportional to the content of Pb2+. A new solid substrate-room temperature phosphorimetry (SS-RTP) for the determination of trace Pb2+ has been established based on R-MWNTs-B–Tween-80 micellae compound containing double luminescent molecule. The detection limit of this method were 0.035 ag Pb2+ spot−1 (8.8 × 10−17 g Pb2+ ml−1, MWNTs-B) and 0.028 ag Pb2+ spot−1 (7.1 × 10−17 g Pb2+ ml−1, R). This method is of high sensitivity, good selectivity, high precision and accuracy. It could be applied to determine trace Pb2+ in serum samples at wavelength of 453.7/623.0 nm (R) or 475.9/645.0 nm (MWNTs-B) with satisfactory results, showing that SS-RTP has flexibility and utility value. Simultaneously, this method can be used to diagnose human diseases. The reaction mechanism for the determination of trace Pb2+ by SS-RTP based on R-MWNTs-B–Tween-80 micellae compound containing double luminescent molecule was also discussed.

UV light irradiation triggers Au NPs that are respectively functionalized on the surface by o-nitrobenzyl alcohol and benzylamine to proceed with a covalent ligation reaction, which leads to assembling of Au NPs into anisotropic one-dimensional (1D) arrays in aqueous solution viaindazolone linkages.

Mesoporous silica nanoparticles grafted with light-responsive polymer on the outer surface were developed as novel nanogated ensembles, which allow encapsulation and release of drug and biological molecules under light irradiation.

We have developed conjugated copolymer–photosensitizer molecular hybrids (PFBDBP–IPBP) with a strong, broad (from <400 nm to ∼700 nm) and continuous visible absorption. The photosensitizing ability of PFBDBP–IPBP was demonstrated to be higher than that of the monochromophore-based IPBP, owing to rational manipulation of the multiple intramolecular energy transfer. In addition, we demonstrated that the developed PFBDBP–IPBP displays excellent photostability compared to the IPBP.