Baohong Liu

A nanoporous molybdenum carbide nanowire as an electrocatalyst for hydrogen evolution reaction

A highly active and stable electrochemical catalyst of nanoporous molybdenum carbide nanowires (np-Mo2C NWs) has been developed for hydrogen evolution reaction (HER). The np-Mo2C NWs were synthesized simply by pyrolysis of a MoOx/amine hybrid precursor with sub-nanosized periodic structure under an inert atmosphere. The enriched nanoporosity and large reactive surface of these highly dispersed nanowires with uniform Mo2C nanocrystallites provide an efficient electrocatalysis, leading to their superior HER activity with lower onset overpotential and higher current densities than Mo2C microparticles. This study opens a new perspective for the development of highly active non-noble electrocatalysts for hydrogen production from water splitting.

Protein chips and nanomaterials for application in tumor marker immunoassays.

Recent advances in molecular biology elucidate that tumor markers play an important role in diagnosis, prognosis and providing insights into the etiology of cancer. Widespread use of tumor markers in healthcare will ultimately depend upon the detection of many tumor markers with high selectivity and sensitivity. This goal has not been obtained with conventional methods which are time-consuming, have poor precision, or experience difficulty in realizing automation. Recently, much attention has been paid to the use of electrochemical immunosensors for the detection of tumor markers due to their high sensitivity, easy miniaturization and automation. This brief review focuses on the current developments, challenges, and trends of electrochemical immunosensors for tumor markers based on protein chips. Whereafter, the recent applications of nanomaterials in tumor marker immunoassays are reviewed. We also introduce some of our groups research works of novel electrochemical immunosensors for the determination of tumor markers.

pH‐Controlled Delivery of Doxorubicin to Cancer Cells, Based on Small Mesoporous Carbon Nanospheres

Mesoporous carbon nanospheres (MCNs) with small diameters of ≈90 nm are developed as an efficient transmembrane delivery vehicle of an anticancer drug, doxorubicin (DOX). MCNs exhibit a high loading capacity toward DOX due to hydrophobic interactions and the supramolecular π stacking between DOX and the carbonaceous structures, on which the pH-dependent drug release are successfully achieved. Specifically, DOX can be loaded onto MCNs in basic solution and in a physiological pH range, while release occurs in acidic solution in its ionized state. By effective passive and active targeting, MCNs can be readily internalized into HeLa cells, where the carried DOX can be efficiently released in the acidic microenvironment of the tumors for further therapy. The endocytosis and cytotoxicity of DOX@MCNs toward HeLa cells are investigated by confocal microscopy and MTT assay. This smart pH-dependent drug loading and release property of DOX@MCNs makes it possible to reduce the cytotoxicity to normal tissues during circulation in the body since the normal physiological pH is ≈7.4.

Low-cost industrially available molybdenum boride and carbide as “platinum-like” catalysts for the hydrogen evolution reaction in biphasic liquid systems

Rarely reported low-cost molybdenum boride and carbide microparticles, both of which are available in abundant quantities due to their widespread use in industry, adsorb at aqueous acid-1,2-dichloroethane interfaces and efficiently catalyse the hydrogen evolution reaction in the presence of the organic electron donor - decamethylferrocene. Kinetic studies monitoring biphasic reactions by UV/vis spectroscopy, and further evidence provided by gas chromatography, highlight (a) their superior rates of catalysis relative to other industrially significant transition metal carbides and silicides, as well as a main group refractory compound, and (b) their highly comparable rates of catalysis to Pt microparticles of similar dimensions. Insight into the catalytic processes occurring for each adsorbed microparticle was obtained by voltammetry at the liquid-liquid interface.

Size-dependent cellular uptake efficiency, mechanism, and cytotoxicity of silica nanoparticles toward HeLa cells

In this study, we investigated and reported the cellular uptake efficiency, mechanism, and cytotoxicity of silica nanoparticles (SNPs) with different sizes. Using confocal laser scanning microscope (CLSM), flow cytometry (FCM), and graphite furnace atomic absorption spectrometry (GFAAS), the qualitative and quantitative experimental results showed that the cellular uptake of SNPs toward HeLa cells is size-dependent. To further examine the uptake process, three different inhibitors including sucrose, Filipin III, and Cytochalasin D (Cyt D) were introduced to pretreat the HeLa cells. It appeared that the largest SNPs (SNPs-307.6) take an energy-dependent uptake pathway (clathrin dependent and caveolin independent) while that for the medium size SNPs-167.8 involves clathrin and caveolin dependent endocytosis. In contrast, the smallest SNPs (SNPs-55.6) follow not only energy required clathrin and caveolin dependent endocytosis but also an energy independent pathway to efficiently enter the cells. Moreover, the cellular uptake efficiency of SNPs, which also show excellent biocompatibility, is size-dependent in the order of 55.6>167.8>307.6 nm. This knowledge is fundamentally important and will facilitate more development of size-defined SNPs as the transporters for various purposes.

Hydrogen evolution across nano-Schottky junctions at carbon supported MoS2 catalysts in biphasic liquid systems

The activities of a series of MoS(2)-based hydrogen evolution catalysts were studied by biphasic reactions monitored by UV/Vis spectroscopy. Carbon supported MoS(2) catalysts performed best due to an abundance of catalytic edge sites and strong electronic coupling of catalyst to support.

A mediator-free screen-printed amperometric biosensor for screening of organophosphorus pesticides with flow-injection analysis (FIA) system

A mediator-free amperometric biosensor for screening organophosphorus pesticides (OPs) in flow-injection analysis (FIA) system based on anticholinesterase activity of OPs to immobilized acetylcholinesterase enzyme (AChE) has been developed. The enzyme biosensor is prepared by entrapping AChE in Al(2)O(3) sol-gel matrix screen-printed on an integrated 3-electrode plastic chip. This strategy is found not only increase the stability of the embedded AChE, but also effectively catalyze the oxidative reaction of thiocholine, making the Al(2)O(3)-AChE biosensor detects the substrate at 0.25V (versus Ag/AgCl), hundreds mini-volt lower than other reported mediator-free ones. The Al(2)O(3)-AChE biosensor is thus coupled to FIA system to build up a simple and low-cost FIA-EC system for screening OPs in real samples. A wide linear inhibition response for dichlorvos, typical OP, is observed in the range of 0.1-80muM, corresponding to 7.91-84.94% inhibition for AChE. The detection limit for dichlorvos is achieved at 10nM in the simulated seawater for 15min inhibiting time, which allows the biosensor quantitatively detects the ecotoxicological effect of the real samples from the seaports in eastern China, where the OPs pollution is confirmed by GC-MS.

Microchip-based ELISA strategy for the detection of low-level disease biomarker in serum.

A simple and sensitive method has been proposed to determine a trace level of alpha-fetoprotein (AFP), hepatocellular carcinoma biomarker, using poly(methyl methacrylate) (PMMA) microfluidic chips coupled with electrochemical detection system. The PMMA microchannels have been modified with poly(ethyleneimine) (PEI) containing abundant NH(2) groups to covalently immobilize AFP monoclonal antibody. Afterward, the antigen AFP and horseradish peroxidase (HRP)-conjugated AFP antibody can sequentially bind through antigen-antibody specific interaction. Atomic force microscopy (AFM) and confocal fluorescence microscope (CFFM) were utilized to characterize the surface topography and protein immobilization after modification. Coupled with three-electrode electrochemical detection system, the immunochip can perform the detection limit of AFP down to 1 pg mL(-1), and achieve a detectable linear concentration range of 1-500 pg mL(-1) by differential pulse voltammetry (DPV). The on-chip immunoassay platform can not only provide rapid and sensitive detection for target proteins but also be resistant to non-specific adsorption of proteins, which contributes to the detection of low-level protein in real sample. Finally, AFP existing in healthy human serum was detected to demonstrate the utility of the immunochip. The result shows that the proposed approach is feasible and has the potential application in clinical analysis and diagnosis.

Covalently coupling the antibody on an amine-self-assembled gold surface to probe hyaluronan-binding protein with capacitance measurement

Hyaluronan-binding proteins (HABPs), the important structural components of extracellular matrices, served important structural and regulatory functions during development and in maintaining adult tissue homestats. A sensitive, specific and rapid-responsing immunosensor to probe hyaluronan-binding cartilage protein was presented in this work. The novel immunosensor supplied a label-free detection method for HABP, which was based on measuring the capacitance change in-between the unlabeled HABP (antigen) and rabbit-anti-HABP (Ra-HABP, antibody). The HABP immunosensor was prepared by covalently coupling Ra-HABP on an amine-self-assembled gold surface with glutaraldehyde. The capacitance change corresponding to the concentration of HABP, the target antigen, was evaluated by an electrochemical approach called potentiostatic-step in microseconds. The immunosensor showed a specific response to HABP in the range 10-1000 ng/ml. The presented work supplied a promising clinical screening method.

A reagentless amperometric biosensor based on the coimmobilization of horseradish peroxidase and methylene green in a modified zeolite matrix

Abstract A new biosensor for the amperometric detection of hydrogen peroxide was developed based on the coimmobilization of horseradish peroxidase (POD) and methylene green on a zeolite modified glassy carbon electrode without the commonly used bovine serum albumin – glutaraldehyde. The large specific surface area of such a zeolite matrix resulted in high enzyme and mediator loading. The intermolecular interaction between the enzyme and the zeolite was investigated using FT-IR. Cyclic voltammetry and amperometric measurement demonstrated that methylene green coimmobilized with POD in this way displayed good stability and could efficiently shuttle electrons between immobilized enzyme and the electrode. Due to the hydrophilic character of the zeolite the soluble enzyme and methylene green can be retained in the zeolite film, greatly improving the stability of the sensor. Electrocatalytic reduction of H 2 O 2 at the electrode was evaluated with respect to solution pH, temperature and operating potential. The sensor exhibited high sensitivity and could be used for more than two months.