Herein, voltage-responsive controlled release film was constructed by grafting ferrocene on the mesoporous inverse opal photonic crystal (mIOPC). The film achieved free-blockage controlled release and realized the monitoring of cargo release without external indicator. Free-blockage was attributed to the voltage switchable nanovalves which undergo hydrophobic-to-hydrophilic transition when applying voltage. Monitoring of cargo release was attributed to the optical property of mIOPC, the bandgap of mIOPC had a red shift when the solution invaded in. The film was hydrophobic enough to stop solution intrusion. Once the voltage was applied, the film became hydrophilic, leading to invasion of the solution. As a result, the cargos were released and the bandgap of mIOPC was red-shifted. Therefore, in this paper both a free-blockage controlled release film and a release sensing system was prepared. The study provides new insights into highly effective controlled release and release sensing without indicator.Keywords: controlled release; free-blockage; hydrophobicity switching; nano valve; release sensing;

Fabricating theranostic nanoparticles combining multimode disease diagnosis and therapeutic has become an emerging approach for personal nanomedicine. However, the diagnostic capability, biocompatibility, and therapeutic efficiency of theranostic nanoplatforms limit their clinic widespread applications. Targeting to the theme of accurate diagnosis and effective therapy of cancer cells, a multifunctional nanoplatform of aptamer and polyethylene glycol (PEG) conjugated MoS2 nanosheets decorated with Cu1.8S nanoparticles (ATPMC) is developed. The ATPMC nanoplatform accomplishes photoluminescence imaging, photoacoustic imaging, and photothermal imaging for in vitro and in vivo tumor cells imaging diagnosis. Meanwhile, the ATPMC nanoplatform facilitates selective delivery of gene probe to detect intracellular microRNA aberrantly expressed in cancer cells and anticancer drug doxorubicin (DOX) for chemotherapy. Moreover, the synergistic interaction of MoS2 and Cu1.8S renders the ATPMC nanoplatform with superb photothermal conversion efficiency. The ATPMC nanoplatform loaded with DOX displays near-infrared laser-induced programmed chemotherapy and advanced photothermal therapy, and the targeted chemo-photothermal therapy presents excellent antitumor efficiency.

•Magnetized carbon nanotube is first used as an immunochromatographic label.•Visual detection of protein in whole blood avoiding complex purification and sample-pretreatment.•The method is rapid, simple, low-cost and portable.The authors describe a magnetized carbon nanotube (MCNT)-based lateral flow strip biosensor for visual detection of proteins directly in whole blood avoiding complex purification and sample pre-treatments. MCNT were synthesized by coating Fe3O4 nanoparticles on the shortened multiwalled carbon nanotube (CNT) surface via co-precipitation of ferric and ferrous ions within a dispersion of shorten multiwalled CNTs. The antibody-modified MCNTs were used to capture target protein in whole blood; the formed MCNT-antibody-target protein complexes were applied to the lateral flow strip biosensor, in which a capture antibody was immobilized on the test zone of the biosensor. The captured MCNTs on the test zone and control zone were producing characteristic brown/black bands, and this enabled target protein to be visually detected. Quantification was accomplished by reading the intensities of the bands with a portable strip reader. Rabbit IgG was used as a model target to demonstrate the proof-of-concept. After systematic optimizations of assay parameters, the detection limit of the assay in whole blood was determined to be 10 ng mL−1 (S/N = 3) with a linear dynamic range of 10–200 ng mL−1. This study provides a rapid and low-cost approach for detecting proteins in blood, showing great promise for clinical application and biomedical diagnosis, particularly in limited resource settings.Combining the superpara-magnetism of Fe3O4 nanoparticles and the outstanding mechanical properties of carbon nanotubes, magnetized carbon nanotube-based lateral flow strip biosensor was first used for visual detection of proteins directly in whole blood avoiding complex purification and sample pretreatment.Download high-res image (144KB)Download full-size image

By combining polymer pen lithography (PPL) patterning with in situ polymerization, we report a straightforward and bottom-up approach for bench-top fabrication of microelectrode arrays (MEAs) with well-controlled dimensions. The as-fabricated MEAs can be used to electrodeposit prussian blue in situ and work as a biosensor for H2O2 with a detection limit as low as 5 nM at a sensitivity of 0.7 A cm−2 M−1.

Prussian blue cubes could be converted at a relatively low temperature (<600 °C) to the N-doped Fe3C@C composites, which showed oxidase-mimicking activity. This study also suggests that the four-electron oxygen reduction catalysts might be candidates for oxidase-mimics.

A high-resolution and universal method for the rapid visualization of latent fingermarks on a broad variety of surfaces has been achieved by simply combining hydrophilic cellulose membrane with dye aqueous solution. In this approach, the relatively hydrophobic characteristic of fingermark residue enable the deposit act as a “mask”, directing dye absorption processes to regions of both furrows without the ridge residues and bare cellulose membrane substrate. This effect during the spatially selective dye absorption generates a negative pattern of the fingermark within a few seconds to minutes depending on the properties of the substrates and fingermark types. It provides observation of latent fingermarks on cellulose membrane surface with high definition of level 2 and level 3 details used for personal identification purposes. It is also highly-efficient for visualizing the latent fingermarks lifted from various common (glass, carton, ceramic cup) and problematic (banknote, human skin and leather) surfaces by using transparent adhesive tape. To examine the generality of the proposed method, eight different kinds of dye aqueous solutions have been tested for developing latent fingermarks and they all provide very good results as expected. Moreover, this approach is easily used for aged fingermarks and natural fingermarks as well. Imaging may be accomplished visibly (by dye color) and topographically (using a microscope or a camera). This approach is a simple, rapid, non-destructive, safe, low-cost, universal and high resolution method compared with conventional approaches, so it demonstrates good potentiality in individual identity validation related applications.

The construction of the Space Station provides a spaceflight laboratory, which enables us to accomplish tremendous short- and long-duration research such as astronomy, physics, material sciences, and life sciences in a microgravity environment. Continuous innovation and development of spaceflight laboratory prompted us to develop a facile detection approach to meet stringent requirements in a microgravity environment that traditional experimental approaches cannot reach. Here we introduce superhydrophilic microwells onto superhydrophobic substrates that are capable of capturing and transferring microdroplets, demonstrating a proof-of-concept study of a biosensing platform toward microgravity application. The capability of manipulating microdroplets originates from the capillary force of the nanoscale dendritic coating in superhydrophilic microwells. Based on theoretical modeling, capillary forces of the superhydrophilic microwells can dominate the behavior of microdroplets against the gravity. Direct naked-eye observation monitoring of daily physiological markers, such as glucose, calcium, and protein can be achieved by colorimetric tests without the requirement of heavy optical or electrical equipment, which greatly reduced the weight, and will bring a promising clue for biodetection in microgravity environments.Keywords: biosensing; colorimetric biosensor; microgravity; superhydrophilic; superhydrophobic; superwettable microchips;

Herein, an efficient electrochemical tracer with advanced oxygen reduction reaction (ORR) performance was designed by controllably decorating platinum (Pt) (diameter, 1 nm) on the surface of compositionally tunable tin-doped indium oxide nanoparticle (Sn–In2O3) (diameter, 25 nm), and using the Pt/Sn–In2O3 as electrochemical tracer and interfacial term hairpin capture probe, a facile and ultrasensitive microRNA (miRNA) detection strategy was developed. The morphology and composition of the generated Pt/Sn–In2O3 NPs were comprehensively characterized by spectroscopic and microscopic measurements, indicating numerous Pt uniformly anchored on the surface of Sn–In2O3. The interaction between Pt and surface Sn as well as high Pt(111) exposure resulted in the excellent electrochemical catalytic ability and stability of the Pt/Sn–In2O3 ORR. As proof-of-principle, using streptavidin (SA) functionalized Pt/Sn–In2O3 (SA/Pt/Sn–In2O3) as electrochemical tracer to amplify the detectable signal and a interfacial term hairpin probe for target capture probe, a miRNA biosensor with a linear range from 5 pM to 0.5 fM and limit of detection (LOD) down to 1.92 fM was developed. Meanwhile, the inherent selectivity of the term hairpin capture probe endowed the biosensor with good base discrimination ability. The good feasibility for real sample detection was also demonstrated. The work paves a new avenue to fabricate and design high-effective electrocatalytic tracer, which have great promise in new bioanalytical applications.

Multifunctional theranostic platform coupling diagnostic and therapeutic functions holds great promise for personalized nanomedicine. Nevertheless, integrating consistently high performance in one single agent is still challenging. This work synthesized a sort of porphyrin derivatives (P) with high singlet oxygen generation ability and graphene quantum dots (GQDs) possessing good fluorescence properties. The P was conjugated to polyethylene glycol (PEG)ylated and aptamer-functionalized GQDs to gain a multifunctional theranostic agent (GQD-PEG-P). The resulting GQD-PEG-P displayed good physiological stability, excellent biocompatibility and low cytotoxicity. The intrinsic fluorescence of the GQDs could be used to discriminate cancer cells from somatic cells, whereas the large surface facilitated gene delivery for intracellular cancer-related microRNA (miRNA) detection. Importantly, it displayed a photothermal conversion efficiency of 28.58% and a high quantum yield of singlet oxygen generation up to 1.08, which enabled it to accomplish advanced photothermal therapy (PTT) and efficient photodynamic therapy (PDT) for cancer treatment. The combined PTT/PDT synergic therapy led to an outstanding therapeutic efficiency for cancer cell treatment.Keywords: graphene quntaum dots; intracellular microRNA detection; photothermal/photodynamic therapy; porphyrin derivative; theranostic nanostructure;

•Recent progress on ultrasound control and propel micro-/nanomotors is summarized.•Two typical devices for ultrasound microparticle manipulation are discussed.•Ultrasound induced interesting phenomenon is presented.•Use of ultrasound fields for biomedical applications is narrated.•Future challenges and opportunities of ultrasound micro-/nanomotors are concluded.Synthetic micro-/nanomachines, which are able to mimic the amazing natural system, can convert energy source into movement, and are expected to help humanity complete environmental and biological tasks. Ultrasound, with major advantages of on-demand motion control, long lifetime, noninvasive, contact free, and great biocompatibility, have been one of the most probable potential toward in vivo drug delivery and clinical diagnosis. In present short review, we intent to summarize the progress in using ultrasound to control and propel micro-/nanomachines during the last decade, and discussed the important aspects toward biomedical applications.Download high-res image (103KB)Download full-size image

AbstractThe formation and metastatic colonization of circulating tumor cells (CTCs) are responsible for the vast majority of cancer-related deaths. Over the last decade, drug-delivery systems (DDSs) have rapidly developed with the emergence of nanotechnology; however, most reported tumor-targeting DDSs are able to deliver drugs only to solid tumor cells and not CTCs. Herein, a novel DDS comprising a composite nanofiber film was constructed to inhibit the viability of CTCs. In this system, gold nanoparticles (Au NPs) were functionalized with doxorubicin (DOX) through an acid-responsive cleavable linker to obtain Au-DOX NPs. Then, the Au-DOX NPs were mixed in a solution of an acid-responsive polymer {i.e., poly[2-(dimethylamino)ethyl methacrylate]} to synthesize the nanofiber film through electrospinning technology. After that, the nanofiber film was modified with a specific antibody (i.e., anti-EpCAM) to enrich the concentration of CTCs on the film. Finally, the Au-DOX NPs were released from the nanofiber film, and they consequently inhibited the viability of CTCs by delivering DOX to the enriched CTCs. This composite nanofiber film was able to decrease the viability of CTCs significantly in the suspended and fluid states, and it is expected to limit the migration and proliferation of tumor cells.

Small size molybdenum disulfide (MoS2) quantum dots (QDs) with desired optical properties were controllably synthesized by using tetrabutylammonium-assisted ultrasonication of multilayered MoS2 powder via OH-mediated chain-like Mo–S bond cleavage mode. The tunable up-bottom approach of precise fabrication of MoS2 QDs finally enables detailed experimental investigations of their optical properties. The synthesized MoS2 QDs present good down-conversion photoluminescence behaviors and exhibit remarkable up-conversion photoluminescence for bioimaging. The mechanism of the emerging photoluminescence was investigated. Furthermore, superior 1O2 production ability of MoS2 QDs to commercial photosensitizer PpIX was demonstrated, which has great potential application for photodynamic therapy. These early affording results of tunable synthesis of MoS2 QDs with desired photo properties can lead to application in fields of biomedical and optoelectronics.Keywords: bioimaging; MoS2 quantum dots; photodynamic therapy (PDT); ultrasonic preparation; up-conversion fluorescence

This study describes a novel ratiometric fluorescent sensor based on chemical etching of gold nanocluster (GNCs) for label-free, separation-free determination of tris(2-carboxyethyl)phosphine (TCEP). TCEP was discovered to exhibit unusual chemical behavior toward fluorescent gold nanoclusters: it quenched the red fluorescent emission of the bovine serum album (BSA)-protected GNCs (GNCs@BSA) and simultaneously restored the blue fluorescent emission of the dityrosine (diTyr) residues of the BSA ligand. The TCEP-induced quenching of the fluorescent GNCs@BSA was investigated with the UV–vis adsorption spectrum, the matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), inductively coupled plasma-mass spectrometry (ICP-MS) and X-ray photoelectron spectroscopy (XPS), revealing the chemical etching of the gold(0) core of the GNCs@BSA by TCEP. Furthermore, the ratio of the blue fluorescence intensity of the diTyr to the red fluorescence intensity of the GNCs@BSA was found to be dependent on TCEP concentration and showed a linear relationship in the TCEP concentration range of 500 nM to 50, 000 nM (R2 = 0.9943) with a limit of detection (LOD) of 130 nM, achieving the higher sensitivity over previous reports. This ratiometric sensor also showed superior selectivity for TCEP over certain common interferences including glutathione, 20 kinds of natural amino acids, and the oxidized form of TCEP. With the developed ratiometric method, the deproteinized human serum samples spiked with TCEP were analyzed with satisfactory results. In addition, it is worth noting that compared with conventional ratiometric fluorescent sensors, the ratiometric sensor developed in this study does not require external fluorophores, avoiding the additional derivation procedures.

Chemical etching of gold by thiols has been known to be capable of generating nonluminescent gold(I) complexes, e.g., in size-focusing synthesis of atomically precise gold nanoclusters (GNCs). These nonluminescent gold(I) complexes have usually been considered as useless or worthless byproducts. This study shows a promising potential of thiol etching of GNCs to prepare novel water-soluble and phosphorescent gold(I) materials for sensing application. First, cysteamine-induced etching of GNCs is used to produce nonluminescent oligomeric gold(I)-thiolate complexes. Then, cadmium ion induces the aggregation of these oligomeric complexes to produce highly water-soluble ultrasmall intra-aggregates. These intra-aggregates can phosphoresce both in dilute aqueous solutions and in the solid phase. Studies on the effect of pH on their phosphorescent emission reveal the importance of the interaction between the amino groups of the ligands and cadmium ion for their phosphorescent emission property. Furthermore, Cu2+ ion is found to quickly quench the phosphorescent emission of the intra-aggregates and simultaneously cause a Cu2+-concentration-dependent peak wavelength shift, enabling the establishment of a novel colorimetric sensor for sensitive and selective visual sensing of Cu2+.

A facile and rapid method for visualizing latent fingermarks (LFMs) on various commonly encountered metallic substrates has been first developed in deep eutectic solvent by utilizing spatially selective co-electrochemical deposition of silver and copper particles. This strategy exploited the LFM residua as an insulating mask and the silver and copper particles were only deposited onto the bare surfaces and the valleys between the papillary ridges on the substrates. As a result, a high contrast negative visualization of LFM that can clearly provide clear ridge minutiae details of the LFMs was obtained under the optimized conditions of electrochemical deposition (applied potential, deposition time and the concentration and ratio of electroplating solution), which demonstrated a promising tool in routine forensic application.

Electrode coating with polydopamine (PDA) is fast becoming a popular surface modification technique. In this study we report the investigation of the use of PDA as electrode coatings with Prussian blue (PB) as an electrode material model. The PB layer was galvanostatically deposited at an Au electrode, followed by PDA coating with the assistance of ammonium persulfate as an oxidant. The thickness of PDA coatings was measured to be ∼60 nm. Electrochemical characterization of the PDA-coated PB electrode revealed that the PDA coatings could stabilize the PB at neutral pH and allow the permeation of hydrogen peroxide (H2O2). Moreover, the PDA coatings were found to effectively exclude the common interfering compounds such as cysteine, ascorbic acid and uric acid, and exhibit selective electrocatalysis towards the electroreduction of H2O2. Accordingly, the PDA-coated PB electrode was applied for determination of H2O2 released from live cells.

The measurement of sulfide, especially hydrogen sulfide, has held the attention of the analytical community due to its unique physiological and pathophysiological roles in biological systems. Electrochemical detection offers a rapid, highly sensitive, affordable, simple, and real-time technique to measure hydrogen sulfide concentration, which has been a well-documented and reliable method. This review details up-to-date research on the electrochemical detection of hydrogen sulfide (ion selective electrodes, polarographic hydrogen sulfide sensors, etc.) in biological samples for potential therapeutic use.

Nano valves have been used in functional porous materials to control molecular transport by changing their properties in response to external stimuli. But most of them are limited by the blocking units and cannot show their state by themselves. Herein, pH switchable nano valves were constructed using mesoporous inverse opal photonic crystal, which realized free-blockage nano valves and achieved the monitoring of the state of the valve by the naked eye without an external indicator. The nano valves were modified by phenylamine groups, which has a convertible hydrophobic/hydrophilic property between deprotonation and protonation. The valves were hydrophobic enough to prevent solution passing through at pH 7.0, and meanwhile a green color was presented. With the decrease of the pH value of the solution, the valves became open and presented a yellow to red color because of the protonation of phenylamine groups followed by the invasion of solution. Thus, in this study not only a free-blockage valve but also nano sensing valve was constructed. We believe that our studies provide new insights into photonic crystal sensors and nano sensing valve.

•A high performance ORR catalyst of Pt/SnO2/C nanofiber was fabricated.•The catalyst exhibits competitive ORR catalytic activity compared to the Pt/C catalyst.•The catalyst displays enhanced methanol tolerance and superior durability.•The mechanism of enhanced ORR catalytic activity was explored.•It provides a guideline for designing analogous structure ORR catalyst.In this report, an efficient oxygen reduction reaction (ORR) electrocatalyst of platinum (Pt) decorated SnO2/C (Pt/SnO2/C) nanofiber was fabricated by using a Pt galvanic displacement of a copper (Cu) layer electrodeposited on electrospinning SnO2/C nanofiber. Microscopic and spectroscopic characterizations revealed that the facile electrospinning and galvanic displacement route generated numerous dispersed Pt nanoparticles on the SnO2/C nanofiber; and Pt nanoparticles (d ~ 2–3 nm) with high composition of Pt (111) facet were preferably deposited at the SnO2/C junctions to form triple junction nanostructures. The resulting Pt/SnO2/C nanocomposite presented an onset potential of 0.02 V vs RHE, specific activity of 1.12 mA cm− 2 and mass activity of 615 mA/mgPt at − 0.05 V vs RHE. It is competitive to commercial Pt/C (10 wt% Pt) catalyst toward ORR. Notably, in comparison with commercial Pt/C, the composition displayed superior electrochemical durability and enhanced methanol tolerance. It was demonstrated that the presence of Pt/SnO2/C triple junction nanostructures coupled with high composition of Pt (111) facets synergistically contributed the enhanced ORR activity, while the good conductivity of the C facilitates the electron transfer during the ORR process. The metal-metal oxide-carbonaceous heterogeneous structure represents a promising platform for designing ORR catalysts with high performance.

A highly sensitive and multiple microRNA (miRNA) detection method by combining three-dimensional (3D) DNA tetrahedron-structured probes (TSPs) to increase the probe reactivity and accessibility with duplex-specific nuclease (DSN) for signal amplification for sensitive miRNA detection was proposed. Briefly, 3D DNA TSPs labeled with different fluorescent dyes for specific target miRNA recognition were modified on a gold nanoparticle (GNP) surface to increase the reactivity and accessibility. Upon hybridization with a specific target, the TSPs immobilized on the GNP surface hybridized with the corresponding target miRNA to form DNA–RNA heteroduplexes, and the DSN can recognize the formed DNA–RNA heteroduplexes to hydrolyze the DNA in the heteroduplexes to produce a specific fluorescent signal corresponding to a specific miRNA, while the released target miRNA strands can initiate another cycle, resulting in a significant signal amplification for sensitive miRNA detection. Different targets can produce different fluorescent signals, leading to the development of a sensitive detection for multiple miRNAs in a homogeneous solution. Under optimized conditions, the proposed assay can simultaneously detect three different miRNAs in a homogeneous solution with a logarithmic linear range spanning 5 magnitudes (10–12–10–16) and achieving a limit of detection down to attomolar concentrations. Meanwhile, the proposed miRNA assay exhibited the capability of discriminating single bases (three bases mismatched miRNAs) and showed good eligibility in the analysis of miRNAs extracted from cell lysates and miRNAs in cell incubation media, which indicates its potential use in biomedical research and clinical analysis.Keywords: duplex-specific nuclease; multiple microRNA detection; signal amplification; tetrahedral DNA nanostructures; ultrasensitive microRNA detection;

The aggregation of Aβ peptides is a crucial factor leading to Alzheimer's disease (AD). Inhibiting the Aβ peptide aggregation has become one of the most essential strategies to treat AD. In this work, efficient and low-cytotoxicity inhibitors, graphene quantum dots (GQDs) are reported for their application in inhibiting the aggregation of Aβ peptides. Compared to other carbon materials, the low cytotoxicity and great biocompatibility of GQDs give an advantage to the clinical research for AD. In addition, the GQDs may cross the blood–brain barrier (BBB) because of the small size. It is believed that GQDs may be therapeutic agents against AD. This work provides a novel insight into the development of Alzheimer's drugs.

One-dimensional Pt nanostructures are of considerable interest for the development of highly stable and sensitive electrochemical sensors. This paper describes a self-interconnecting Pt nanowire network electrode (PtNNE) for the detection of hydrogen peroxide (H2O2) and glucose with ultrahigh sensitivity and stability. The as-prepared PtNNE consists of polycrystalline nanowires with high-index facets along the side surface which provides more active surface atoms on kinks and steps, those ultralong nanowires being interconnected with each other to form a free-standing network membrane. The excellent structural features of the PtNNE promoted its performance as a Pt-based electrochemical sensor both in terms of electrocatalytic activity and stability. Amperometric measurements towards hydrogen peroxide were performed; the PtNNE sensor showed an extremely high sensitivity of 1360 μA mM−1 cm−2. This excellent sensitivity is mainly attributed to the high-index facets of the nanowires resulting in their superior electrocatalytic activity towards H2O2, and the interconnected nanowire network forming an “electron freeway” transport model, which could provide multiple electron pathways and fast electron transport on the electrode, leading to rapid reaction and sensitive signal detection. The as-prepared PtNNE also holds promise as an oxidase-based biosensor. As a proof of concept, a PtNNE-based glucose biosensor also showed an outstanding sensitivity as high as 114 μA mM−1 cm−2, a low detection limit of 1.5 μM, and an impressive detection range from 5 μM to 30 mM.

Photoluminescent (PL) graphene quantum dots (GQDs) with large surface area and superior mechanical flexibility exhibit fascinating optical and electronic properties and possess great promising applications in biomedical engineering. Here, a multifunctional nanocomposite of poly(l-lactide) (PLA) and polyethylene glycol (PEG)-grafted GQDs (f-GQDs) was proposed for simultaneous intracellular microRNAs (miRNAs) imaging analysis and combined gene delivery for enhanced therapeutic efficiency. The functionalization of GQDs with PEG and PLA imparts the nanocomposite with super physiological stability and stable photoluminescence over a broad pH range, which is vital for cell imaging. Cell experiments demonstrate the f-GQDs excellent biocompatibility, lower cytotoxicity, and protective properties. Using the HeLa cell as a model, we found the f-GQDs effectively delivered a miRNA probe for intracellular miRNA imaging analysis and regulation. Notably, the large surface of GQDs was capable of simultaneous adsorption of agents targeting miRNA-21 and survivin, respectively. The combined conjugation of miRNA-21-targeting and survivin-targeting agents induced better inhibition of cancer cell growth and more apoptosis of cancer cells, compared with conjugation of agents targeting miRNA-21 or survivin alone. These findings highlight the promise of the highly versatile multifunctional nanocomposite in biomedical application of intracellular molecules analysis and clinical gene therapeutics.Keywords: cell imaging; gene therapeutics; graphene quantum dots; microRNAs; survivin;

Catalytic films comprising the arrayed mesoporous and big-inner-diameter carbon nanotubes embedded with high density Au nanoparticles were prepared through a template-directed carbonization route.

In this study, we introduce a method for large-area and substrate-independent synthesis of the big-inner-diameter carbon nanotube (BIDI-CNT) thin films by utilizing polydopamine (PDA) as carbon source and ZnO nanorods (NRs) as sacrificing template for the first time. ZnO NRs with hexagonal morphology were coated with PDA films via the ammonium persulfate-induced polymerization of dopamine at neutral pH for avoiding the degradation of amphoteric ZnO at alkaline pH needed by the conventional oxygen-induced polymerization of dopamine. After carbonization in N2 atmosphere at 500 °C followed by ZnO removal, the hollow BIDI-CNTs with tuned wall thickness and hexagonal morphology were obtained. In addition, the obtained BIDI-CNTs were found to be N-doped. Furthermore, on the base of the outstanding substrate-independent growth properties of both ZnO NRs and PDA, the large area thin films of the N-doped BIDI-CNTs could be synthesized on various solid substrates, for instance, Al2O3, gold, fluorine-doped tin oxide-coated glass, platinum, silicon, mica, and quartz.

Herein, a highly sensitive and selective microRNA (miRNA) detection strategy using DNA-bio-bar-code amplification (BCA) and Nb·BbvCI nicking enzyme-assisted strand cycle for exponential signal amplification was designed. The DNA-BCA system contains a locked nucleic acid (LNA) modified DNA probe for improving hybridization efficiency, while a signal reported molecular beacon (MB) with an endonuclease recognition site was designed for strand cycle amplification. In the presence of target miRNA, the oligonucleotides functionalized magnetic nanoprobe (MNP-DNA) and gold nanoprobe (AuNP-DNA) with numerous reported probes (RP) can hybridize with target miRNA, respectively, to form a sandwich structure. After sandwich structures were separated from the solution by the magnetic field, the RP were released under high temperature to recognize the MB and cleaved the hairpin DNA to induce the dissociation of RP. The dissociated RP then triggered the next strand cycle to produce exponential fluorescent signal amplification for miRNA detection. Under optimized conditions, the exponential signal amplification system shows a good linear range of 6 orders of magnitude (from 0.3 pM to 3 aM) with limit of detection (LOD) down to 52.5 zM, while the sandwich structure renders the system with high selectivity. Meanwhile, the feasibility of the proposed strategy for cell miRNA detection was confirmed by analyzing miRNA-21 in HeLa lysates. Given the high-performance for miRNA analysis, the strategy has a promising application in biological detection and in clinical diagnosis.

Here the combination of carboxylated multi-walled carbon nanotubes (CMWCNTs) and Prussian blue (PB) for fabricating pH-responsive electroactive composite thin films is reported. The as-prepared CMWCNT@PB composite films were found to change their electrochemical behaviors in response to the solution pH, including their cyclic voltammetric and the corresponding electrochromic behaviors. The electrochromic state of PB could be switched on and off by the solution pH. Furthermore, a linear relationship was found between the peak-to-peak potential separation of the cyclic voltammogram of PB and the solution pH, indicating that the composite film modified electrode might be useful for the development of novel pH sensors. The approach for the fabrication of pH-responsive electrochemical composite films demonstrated here should be generalizable to other redox nanomaterials.

•Cysteamine is a strong etchant.•Cysteamine can selectively quench the fluorescence emission of the BSA-protected Au25 nanoclusters in the presence of glutathione and cysteine.•An etching-based, label-free and separation-free fluorescent method is developed for selectively sensing cysteamine.•The detection limit for cysteamine is 150 nM (S/N=3).This study describes a novel Au nanocluster-based fluorescent sensor for label-free, separation-free and selective detection of cysteamine (CSH). The sensing mechanism is based on CSH etching-induced fluorescence quenching of the bovine serum albumin-protected Au25 nanoclusters (BSAGNCs). A series of characterizations is carried out towards a better understanding of the CSH-induced fluorescence quenching of the BSAGNCs. It is found that CSH can etch the Au25 nanoclusters, exhibiting the potent etching activity. Other thiol-containing compounds such as glutathione and cysteine and other 19 natural amino acids do not interfere with such CSH-induced etching process. The decreases in fluorescence intensity of the BSAGNCs allow sensitive detection of free CSH in the range of 500–10,000 nM. The detection limit for CSH is 150 nM (S/N=3). The spiked human serum samples can be analyzed with satisfactory results.

•We presented a novel electrochemical immunosensor for the detection of APOE4.•Synergetic effect of Fractal nanostructures and enzyme amplification enhanced the sensitivity of the sensor greatly.•It exhibited a wide linearity from 1 ng/mL to 10,000 ng/mL and a detection limit of 0.3 ng/mL.•The APOE4 protein was firstly detected by electrochemical immunosensor.Human apolipoprotein E4 (APOE4) is a major risk factor for Alzheimer's disease (AD) and can greatly increase the morbidity. In this work, an ultrasensitive sandwich-type electrochemical immunosensor for the quantitative detection of APOE4 was designed based on fractal gold (FracAu) nanostructures and enzyme amplification. The FracAu nanostructures were directly electrodeposited by hydrogen tetrachloroaurate (HAuCl4) on polyelectrolytes modified indium tin oxide (ITO) electrode. The sensing performances of the modified interface were investigated by cyclic voltammetry (CV). After functionalization with HRP-labeled APOE4 antibody, the human APOE4 could be detected quantitatively by current response. The current response has a linear relationship with the logarithm of human APOE4 concentrations in a range from 1.0 to 10,000.0 ng/mL, with a detection limit of 0.3 ng/mL. The fabricated APOE4 electrochemical immunosensor exhibits strong specificity, high sensitivity, low detection limit and wide linear range. The detection of human APOE4 provides a strong support for the prevention of AD and early-stage warning for those susceptible populations.

The protein ligand shells of fluorescent protein-protected gold nanoclusters play an important role in the physiochemical properties and sensing applications of the nanoclusters. Recently, more and more attention has been paid to the investigation of the changes in the protein structure elements induced by the introduction of the nanoclusters in the proteins. In this work, the strategy of removal of the encapsulated gold nanoclusters from the protein ligand cages has been proposed, producing the “hollow” (or possibly “imprinted”) proteins for investigations for the first time. Nontoxic cysteamine was used as the etchant of the gold nanoclusters. With bovine serum albumin, lysozyme, and ovalbumin as model proteins, it was found that the luminescent dityrosine cross-links exist in the protein-protected gold nanoclusters, however, inner filter effect caused by the gold nanoclusters hide them.

A self-powered triboelectric nanosensor (TENS) based on the contact-separation mode between a thin layer of poly(tetrafluoroethylene) (PTFE) with nanoparticle arrays and an aluminum film was fabricated for the detection of dopamine (DA) in the alkaline condition. High selectivity and sensitivity (detection limit of 0.5 μM, a linear range from 10 μM to 1 mM) have been achieved through the strong interaction between the nonstick PTFE and DA via its oxidative self-polymerization, and the output voltage and current of the developed TENS can reach 116 V and 33 μA, which is exceptionally attractive for the fabrication of self-powered and portable device toward the detection of dopamine.Keywords: dopamine; poly(tetrafluoroethylene) nanoparticle arrays; self-powered nanosensor; triboelectric nanogenerator;

Cytochromes P450 (CYPs) enzymes are involved in catalyzing the metabolism of various endogenous and exogenous compounds. A rapid analysis of drug metabolism reactions by CYPs is required because they can metabolize 95% of current drugs in drug development and effective therapies. Here, we describe a study of piezotronic-effect enhanced drug metabolism and sensing by utilizing a single ZnO nanowire (ZnO NW) device. Owing to the unique hydrophobic feature of a ZnO NW that provides a desirable “microenvironment” for the immobilization of biomolecules, our device can effectively stimulate the tolbutamide metabolism by decorating a ZnO NW with cytochrome P4502C9/CYPs reductase (CYP2C9/CPR) microsomes. By applying an external compressive strain to the ZnO nanowire, the piezotronic effect, which plays a primary role in tuning the transport behavior of a ZnO NW utilizing the created piezoelectric polarization charges at the local interface, can effectively enhance the performance of the device. A theoretical model is proposed using an energy band diagram to explain the experimental data. This study provides a potential approach to study drug metabolism and trace drug detection based on the piezotronic effect.Keywords: cytochrome P450; drug metabolism; piezotronic effect; ZnO nanowire;

•A facile and sensitive miRNA biosensor coupling a conformational molecular beacon with target recycling amplification was developed.•The metal ion-meditated molecular beacon uses novel fluorescent Ag nanocluster (AgNCs) as fluorophore.•The competition displacing interaction between the target and the Hg2+ endows the biosensor with high sequence discrimination capability.•Target recycling amplification allows the biosensor to detect the target with high sensitivity.A label-free and high-sensitive microRNA (miRNA) detection approach by coupling a metal ion-meditated conformational molecular beacon (MB), using novel fluorescent Ag nanocluster (AgNCs) as fluorophore, with endonuclease-assisted target recycling amplification was developed. The assay comprised an Hg2+ ion-meditated conformational MB probe and an assistant probe that do not hybridize with each other at a specific temperature and can be annealed to each other in the presence of the target to form a Y-shape junction structure and released Hg2+. The target-MB hybridization event with the help of assistant probe can readily be read out based on the efficient fluorescence quenching of AgNCs by released Hg2+, while the Y-shape junction structure consisting of the probe MB, assistant probe and target miRNA could be recognized by the endonuclease Nt.BbvCI. The MB probe was then effectively cleaved by the endonuclease, and the regenerated assistant probe and the target further attended another cleavage cycle to implement the signal amplification. The competition displacing interaction between the target and the Hg2+ endows the biosensor with high sequence discrimination capability, while the high signal-to-noise ratio and target recycling amplification allows the biosensor to detect the target with high sensitivity. Under the optimal conditions, the concentration of target miRNA could be conveniently read out with a linear range from 10 pM to 1 fM. The proposed approach, avoiding any laborious label, possessing high sensitivity and selectivity, provided significant potential applications in future clinical analysis.

Polydopamine (PDA) is fast becoming a popular surface modification technique. Detailed understanding of the ion permeability properties of PDA films will improve their applications. Herein, we report for the first time the thickness-independent ion permeability of PDA films using a Prussian blue (PB)-based electrochemical method. In this method, PDA films are deposited via ammonium persulfate-induced dopamine polymerization onto a PB electrode. The ion permeability of the PDA films can thus be detected by observing the changes in electrochemical behaviors of the PB coated by PDA films. On the basis of this method, it was unexpectedly found that the PDA films with thickness greater than 45 nm (e.g., ∼60 and ∼113 nm) can exhibit pH-switchable but thickness-insensitive permeability to monovalent cations such as potassium and sodium ions. These observations clearly indicate the presence of a continuous network of interconnected intermolecular voids within PDA films, regardless of film thickness.

•This paper reports a visual detection method for microRNA.•The analysis time is 20 min.•MicroRNA is identified in the cell lysate.We report a DNA-gold nanoparticle (DNA-GNP) based lateral flow nucleic acid biosensor for visual detection of microRNA (miRNA)-215 in aqueous solutions and biological samples with low-cost and short analysis time. Sandwich-type hybridization reactions among GNP-labeled DNA probe, miRNA-215 and biotin-modified DNA probes were performed on the lateral flow device. The accumulation of GNPs on the test zone of the biosensor enables the visual detection of miRNA-215. After systematic optimization, the biosensor was able to detect a minimum concentration of 60 pM miRNA-215. The biosensor was applied to detect miRNA-215 from A549 cell lysate directly without complex sample treatment, and the detection limit of 0.148 million cells was obtained. This study provides a simple, rapid, specific and low-cost approach for miRNA detection in aqueous solutions and biological samples, showing great promise for clinical application and biomedical diagnosis in some malignant diseases.

Here we report a controllable method based on electrodeposition to fabricate Ag nanodendrites (NDs) on a microwell patterned electrode. The microwell patterns on the ITO electrode are fabricated via the microcontact printing technique. By varying the microwell size and electrodeposition time, the morphology of metal deposits on the microwell patterned ITO electrode can be tuned from boulders to dendrites. At the edge of the microwells, the current density was strengthened, which incurs rapid nucleation. The nucleus develops into dendrites because of Mullins–Sekerka instability. However, only boulders were observed at the center of microwells. By reducing the size of the microwells, only NDs were fabricated due to the edge effect. On the basis of understanding the underlying mechanism for dendritic growth in a confined space, our method is used for fabricating other noble metal (Au, Pt) nanodendrites. The controllable synthesis of Au and Pt NDs indicates the universality of this method. Compared with Ag film obtained from electron beam evaporation, the as-prepared Ag NDs exhibit highly enhanced surface-enhanced Raman scattering (SERS) sensitivity when they are used to detect rhodamine 6G (R6G). This approach provides a very controllable, reliable and general way for space-confined fabricating the noble metal nanodendrite arrays which show great promise in catalysis, sensing, biomedicine, electronic and magnetic devices.

A simple method for the preparation of a highly stable and reliable surface-enhanced Raman scattering (SERS) substrate was proposed. The SERS enhancement was demonstrated with good controllability and reproducibility through the controlled formation/deformation of SERS “hotspots” using a reversible DNA nanoswitch. Highly effective DNA detection was achieved using a well-designed sandwich structure.

A novel and simple strategy for visualizing both sebaceous and eccrine latent fingerprints on conductive surfaces (indium/tin oxide-coated glass, gold, platinum and stainless steel coin) has been developed by the use of spatially selective electrodeposition of gold or silver nanoparticles (NPs). In this technique, the fingerprint residue acted as an insulator to the electrodeposition process, so that the metal NPs could only be generated on the areas without residue, which resulted in a negative image of the fingerprint with high contrast. In addition, latent fingerprints could be effectively visualized on various conductive surfaces no matter they were smooth or rough, clean or dirty. The surface morphology of AuNPs was characterized by the field emission scanning electron microscopy (FE-SEM).Highlights► A novel and facile strategy was proposed for visualization of latent fingerprints. ► NPs were selectively electrodeposited only on the valleys of latent fingerprints and the free conductive surfaces. ► Latent fingerprints could be effectively visualized on both smooth and rough conductive surfaces. ► The approach of electrodeposition is simple, rapid, high resolution and eco-friendly.

In this paper, we reported a facile method of fabricating a reusable fluorescent Cu2+-sensor. To fabricate the reusable sensor, the bovine serum albumin-protected gold nanoclusters (BSAGNCs) were complexed with polyelectrolytes, i.e., positively charged polydiallyldimethylammonium (PDDA) and negatively charged polystyrenesulfonate (PSS), and were coated on a glass slide. The prepared film-modified glass slides exhibited the recyclability of fluorescent signal “off–on” behaviors: the fluorescence could be switched “off” by immersing the film sensors in Cu2+ solution and “on” by washing with ethylene diamine tetraacetic acid (EDTA) solution. The prepared film-modified glass slides exhibited high selectivity towards Cu2+ the fluorescence quenching behavior in the form of the Stern–Volmer equation. In addition, the spiked tap water samples were analyzed with satisfactory results. These demonstrations provide a new convenient approach to develop the BSAGNCs-based, reusable fluorescence sensors.Highlights► The BSA-protected GNCs were modified with polyelectrolytes of opposite charges. ► Bare glass slides were modified with the prepared complexes of protein–polyelectrolytes. ► A reusable fluorescence sensor for copper ion was proposed.

A highly sensitive DNA biosensing method down to sub-femtomolar level with excellent selectivity was proposed by designing an amplified synthesis of horseradish peroxidase mimicking DNAzyme and introducing the amplified DNAzyme to chemiluminescent (CL) imaging. The amplified synthesis was achieved by combining a target DNA related ligase reaction with rolling circle amplification (RCA), which produced thousands of repeated sequences to bind hemin and form a mass of horseradish peroxidase-mimicing DNAzyme units. The amplification strategy greatly enhanced the CL emission of the luminol–H2O2 system. The genotyping method displayed highly specific biochemistry in allele discrimination. The novel CL imaging strategy based on ligation-mediated RCA synthesis of DNAzyme showed high fidelity in discriminating single-base mismatch and efficiently facilitated signal amplification for sensitive target DNA detection. It could detect DNA ranging from 1×10−15 M to 1×10−11 M with a detection limit of 0.26 fM. The proposed approach provided a robust, cost-efficient, highly sensitive and specific platform for genetic target analysis in bioanalysis and clinic biomedical application.Highlights► This work constructs a highly sensitive chemiluminescent imaging method. ► A novel signal amplification strategy to enhance the sensitivity is proposed. ► Ligation-mediated rolling circle amplification of DNAzyme is introduced to CL imaging. ► This biosensor can detect target DNA down to sub-femtomolar level.

We report a label-free and ultrasensitive aptasensor based on a fractal gold modified (FracAu) electrode for thrombin detection with a femtomolar detection limit. The FracAu electrode was prepared by electrodeposition of hydrogen tetrachloroaurate (HAuCl4) onto a bare indium tin oxide (ITO) electrode surface. After this process the electrode was characterized by SEM. A thiol-modified aptamer against thrombin was immobilized on the FracAu electrode through a self-assembling process. Upon thrombin binding, the interfacial electron transfer of the FracAu electrode was perturbed by the formation of an aptamer–thrombin complex. The concentration of thrombin in the sample solution was determined by measuring the change in the oxidation peak current of hydroxymethyl ferrocene (C11H12FeO) with differential pulse voltammetry (DPV). The current response (reduced peak current) had a linear relationship with the logarithm of thrombin concentrations in the range of 10−15 to 10−10 M with a detection limit of 5.7 fM. Furthermore, the as-prepared FracAu electrode exhibited high selectivity. The application of FracAu electrodes may be extended to prepare other types of biosensors, such as immunosensors, enzyme biosensors and DNA biosensors. These results show that FracAu electrodes have great promise for clinical diagnosis of disease-related biomarkers.

A simple, highly sensitive, and selective multiple microRNA (miRNA) detection method based on the graphene oxide (GO) fluorescence quenching and isothermal strand-displacement polymerase reaction (ISDPR) was proposed. The capability to discriminate ssDNA and double-stranded nucleic acid structure coupled with the extraordinary fluorescence quenching of GO on multiple organic dye allows the proposed strategy to simultaneously and selectively detect several miRNA labeled with different dyes in the same solution, while the ISDPR amplification endows the detection method with high sensitivity. The strong interaction between ssDNA and GO led to the fluorescent ssDNA probe exhibiting minimal background fluorescence. Upon the recognition of specific target miRNA, an ISDPR was triggered to produce numerous massive specific DNA-miRNA duplex helixes, and a strong emission was observed due to the weak interaction between the DNA-miRNA duplex helix and GO. A miRNA biosensor down to 2.1 fM with a linear range of 4 orders of magnitude was obtained. Furthermore, the large planar surface of GO allows simultaneous quenching of several DNA probes with different dyes and produces a multiple biosensing platform with high sensitivity and selectivity, which has promising application in profiling the pattern of miRNA expression and biomedical research.

A simple, sensitive, and label-free method for microRNA (miRNA) biosensing was described using oligonucleotide encapsulated silver nanoclusters (Ag-NCs) as effective electrochemical probes. The functional oligonucleotide probe integrates both recognition sequence for hybridization and template sequence for in situ synthesis of Ag-NCs, which appears to possess exceptional metal mimic enzyme properties for catalyzing H2O2 reduction. The miRNA assay employs gold electrodes to immobilize the molecular beacon (MB) probe. After the MB probe subsequently hybridizes with the target and functional probe, the oligonucleotide encapsulated Ag-NCs are brought to the electrode surface and produce a detection signal, in response to H2O2 reduction. An electrochemical miRNA biosensor down to 67 fM with a linear range of 5 orders of magnitude was obtained. Meanwhile, the MB probe allows the biosensor to detect the target with high selectivity. The Ag-NCs-based approach provides a novel avenue to detect miRNA with high sensitivity and selectivity while avoiding laborious label and signal amplification. It is convinced that rational introduction of signal amplification strategy to the Ag-NCs-based bioanalysis can further improve the sensitivity. To our best knowledge, this is the first application of the electrocatalytic activity of Ag-NCs in bioanalysis, which would be attractive for genetic analysis and clinic biomedical application.

A novel vacuum metal deposition (VMD) based technique has been efficiently employed for the visualization of latent fingerprints on glass and plastic substrates. Al-doped ZnO thin film (ZAO) was deposited on the bare surface and the valleys between the fingerprint ridges by direct current magnetron sputtering with the oblique target, which yielded normal development of latent fingerprints. The enhanced results of latent fingerprints have been photographed with good contrast by a conventional digital camera. Additionally, an electrochemical method, scanning electrochemical microscopy (SECM), has also been successfully applied to the image acquisition of a latent fingerprint developed on the glass surface due to its superb sensitivity toward the small variation of the conductivities at the substrate surface. The SECM image of a latent fingerprint on glass substrate provided good contrast between valleys and ridges and micrometer-scale resolution images of fingerprints under wet conditions by using ferrocene methanol as a redox mediator to detect the topology of the fingerprint deposits in constant-height feedback mode.

In this preliminary report, the preparation and characterization of a nano-hybrid microprobe, composed of aligned carbon nanotube-modified single carbon fibre coated with gold nanoparticles (GNPs) attached to a polymer film, is described for the first time. The functionalization of the microelectrodes with polymer film prior to the GNP attachment step was demonstrated to significantly improve the GNP surface coverage and distribution. Surface status characterization of these hybrid structured electrodes was performed using scanning electron microscopy and the importance of the presence of polymer was clearly observed. By using cyclic voltammetry, possible application of the proposed nano-composite microprobe for enzymeless glucose detection is demonstrated.Highlights► Development and characterization of nano-hybrid material for sensing application ► Combining carbon fibre covered with aligned carbon nanotubes and gold nanoparticles ► Essential is the use of suitably charged and structured polymer polyethyleneimine ► Only chosen combination of components results in successful direct glucose oxidation ► Voltammetric microprobe model with good capacity for enzymeless glucose sensing

Proteins play important roles in human daily life. To take advantage of the lessons learned from nature, it is essential to investigate the self-assembly of subunits of proteins, i.e., amino acids and polypeptides. Due to its high resolution and versatility of working environment, scanning tunneling microscopy (STM) has become a powerful tool for studying interfacial molecular assembly structures. This review is intended to reflect the progress in studying interfacial self-assembly of amino acids and peptides by STM. In particular, we focus on environment-induced polymorphism, chiral recognition, and coadsorption behavior with molecular templates. These studies would be highly beneficial to research endeavors exploring the mechanism and nanoscale-controlling molecular assemblies of amino acids and polypeptides on surfaces, understanding the origin of life, unravelling the essence of disease at the molecular level and deeming what is necessary for the “bottom-up” nanofabrication of molecular devices and biosensors being constructed with useful properties and desired performance.

Mesoporous silica material with organo-bridged silsesquioxane frameworks is a kind of synergistic combination of inorganic silica, mesopores and organics, resulting in some novel or enhanced physicochemical and biocompatible properties compared with conventional mesoporous silica materials with pure Si-O composition. With the rapid development of nanotechnology, monodispersed nanoscale periodic mesoporous organosilica nanoparticles (PMO NPs) and organo-bridged mesoporous silica nanoparticles (MSNs) with various organic groups and structures have recently been synthesized from 100%, or less, bridged organosilica precursors, respectively. Since then, these materials have been employed as carrier platforms to construct bioimaging and/or therapeutic agent delivery nanosystems for nano-biomedical application, and they demonstrate some unique and/or enhanced properties and performances. This review article provides a comprehensive overview of the controlled synthesis of PMO NPs and organo-bridged MSNs, physicochemical and biocompatible properties, and their nano-biomedical application as bioimaging agent and/or therapeutic agent delivery system.This review provides an overview of controlled synthesis and properties of mesoporous silica nanoparticles with organo-bridged silsesquioxane framework and their nano-biomedicine application as an advanced platform for bioimaging and therapeutic agent delivery.

•A facile and sensitive microRNA biosensor was designed.•It allowed detection of miRNA with the limit of detection down to 0.045 pM.•The stre-GNRs tag was readily served as promising amplification labels in SPR sensing technology.•It employed interfacial biotinylated thiolated DNA molecular beacon as probe.•It was readily served as a powerful ultrasensitive sandwich assay for miRNA detection.Herein, a facile and sensitive microRNA (miRNA) biosensor was designed by using interfacial biotinylated thiolated DNA molecular beacon (MB) as probe and streptavidin functionalized gold nanorods (Stre-GNRs) as tag for the enhanced surface plasmon resonance (SPR) signal. The MB probe with two terminals labeled with biotin and thiol groups, respectively, was modified on the gold film via thiol-gold interaction. Upon hybridization with the target, the biotinylated group became accessible to the Stre-GNRs. The introduction of the Stre-GNRs tag to the gold film produced strong SPR signal for detection. Our work has illustrated that the plasmonic field extension generated from the gold film to GNRs and the mass increase due to the GNRs have led to drastic sensitivity enhancement. Under optimal conditions, this proposed approach allowed detection of miRNA with the limit of detection (LOD) down to 0.045 pM. The results have shown that the MB probe functionalized sensing film, together with streptavidin-conjugated GNRs, was readily served as a plasmonic coupling partner that can be used as a powerful ultrasensitive sandwich assay for miRNA detection, and GNRs were readily served as promising amplification labels in SPR sensing technology.

Catalytic films comprising the arrayed mesoporous and big-inner-diameter carbon nanotubes embedded with high density Au nanoparticles were prepared through a template-directed carbonization route.

Prussian blue cubes could be converted at a relatively low temperature (<600 °C) to the N-doped Fe3C@C composites, which showed oxidase-mimicking activity. This study also suggests that the four-electron oxygen reduction catalysts might be candidates for oxidase-mimics.