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Comprehensive Summary: The review summaries our achievements in optical, electrochemical, as well as mass spectrometry analysis and imaging with high sensitivity, specificity, and spatiotemporal resolution. We promoted the plasmonic imaging system, and developed ultra‐sensitive plasmonic nanoprobes for the tracking of single molecules in single living cells, as well as plasmonic nanocatalysts for highly efficient energy conversion. In addition, we contributed a lot in electrogenerated chemiluminescence (ECL) analysis and imaging. Pioneering works including localized surface plasmon resonance (LSPR) enhanced ECL, ECL ratiometric detection, BPE based ECL system, multi‐color ECL sensing as well as super‐resolved ECL imaging have been initiated by our group. Furthermore, we also dedicated in nanopipette based electrochemical analysis in single living cells, as well as ESI‐MS analysis on short time scale. The research works of our group promoted the development of chemical measurement and analysis. What is the most favorite and original chemistry developed in your research group? LSPR enhanced ECL and Bipolar electrochemistry analysis, single particle based single cell analysis and super‐resolved imaging. What is the most important personality for scientific research? Strong curiosity, perseverance, strong hands‐on ability. How do you supervise your students? Encourage students to read more, think more, discuss more, and try more. How do you keep balance between research and family? Allocating time reasonably. Who influences you mostly in your life? My PhD director, Prof. Hong‐Yuan Chen. What are your hobbies? I used to like to play badminton, now I'm learning to play table tennis. [ABSTRACT FROM AUTHOR]

Enzymatic biosensors have been valuable bioanalytical devices for analysis of diverse targets in disease diagnosis, biological and biomedical research, etc. Photoelectrochemical (PEC) bioanalysis is a recently emerged method that promptly becoming a subject of new research interests due to its attractive potential for future bioanalysis with high sensitivity and specificity. PEC enzymatic biosensors integrate the inherent sensitivities of PEC bioanalysis and the selectivity of enzymes and thus share their both advantages. Currently, PEC enzymatic biosensors have become a hot topic of significant research and the recent impetus has grown rapidly as demonstrated by increased research papers. Given the pace of advances in this area, this review will make a thorough discussion and survey on the fundamentals, sensing strategies, applications and the state of the art in PEC enzymatic biosensors, followed by future prospects based on our own opinions. We hope this work could provide an accessible introduction to PEC enzymatic biosensors for any scientist. [ABSTRACT FROM AUTHOR]

Photoelectrochemical (PEC) bioanalysis represents a unique and dynamically developing methodology that offers an elegant route for sensitive biomolecular detection. Aptamers are synthetic nucleic acid molecules whose binding characteristics can rival those of protein antibodies. Originated from the fusion of PEC bioanalysis and aptamers, PEC aptasensing has rapidly becoming a subject of new research interests in recent years. Using illustrative examples, this review provides the introductory concept, bioanalysis development, signaling strategies, and the state of the art in this field. The future prospects are also discussed. [ABSTRACT FROM AUTHOR]

Depending on the situation, metal ions may either play beneficial roles or be harmful to human health and ecosystems. Sensitive and accurate detection of metal ions is thus a critical issue in the field of analytical sciences and great efforts have been devoted to the development of various metal ion sensors. Photoelectrochemical (PEC) detection is an emerging technique for the bio/chemical detection of metal ions, and features a fast response, low cost and high sensitivity. Using representative examples, this review will first introduce the fundamentals and summarize recent progress in the PEC detection of metal ions. In addition, interesting strategies for the design of particular PEC metal ion sensors are discussed. Challenges and opportunities in this field are also presented. [ABSTRACT FROM AUTHOR]

A novel electrochemical biosensor for cancer cell detection was developed based on aptamer-based competition and supersandwich G-quadruplex DNAzyme amplification strategy. Due to the stronger affinity between the aptamer and cancer cells than that with its complementary oligonucleotide, the complementary oligonucleotide will be facilely replaced. As a consequence, we can detect cancer cells indirectly by detecting the releasing DNA which is proportional to the concentration of K562 cells. Through the supersandwich G-quadruplex DNAzyme amplification strategy, the sensitivity can be dramatically enhanced with detection limit down to 14 cells. [ABSTRACT FROM AUTHOR]

The evolution of photoelectrochemical (PEC) bioanalysis has resulted in substantial progress in its analytical performance and biodetection applications. The aim of this review is to provide a panoramic snapshot of the state of the art in this dynamically developing field, with special emphasis on PEC DNA analysis, immunoassay, enzymatic biosensing and cell-related detection. The future prospects in this area are also evaluated and discussed. This work will serve as a useful source to inform the interested audience of the latest developments and applications in the field of PEC bioanalysis. [ABSTRACT FROM AUTHOR]

Transconductance (gm) is one important figure of merit for benchmarking organic electrochemical transistor (OECT) biosensors, which nevertheless experiences undesired fluctuation instead of keep constant during the target detection of varied concentrations. Light‐matter interplay is recently shown as a potential way to regulate the OECT characteristics, e.g. maximum gm at zero gate bias is achieved. In this work, the challenge of unstable gm is addressed by using a unique metal‐organic framework (MOF)‐derived hollow tube indium sulfide (m‐In2S3) as the photogate. Interestingly, the light irradiation on m‐In2S3 generate a straight transfer curve, leading to a stable gm that is desirable for biological application. Exemplifying by an aptasening, such a device is then tested for protein quantification with a stable sensitivity during the detection. This work features the feasibility of light‐matter interplay to achieve a stable gm in organic electronics. [ABSTRACT FROM AUTHOR]

In this work, a simple and effective approach to obtain stable, nontoxic and strong electrochemiluminescence (ECL) interfaces is provided by coating TiO2 nanoparticles (NPs) modified glassy carbon electrode (GCE) surfaces with Nafion. Unlike a decrease of the current resulting from the blocked diffusion usually displayed in electrochemical processes by Nafion coating, a Nafion/TiO2 NPs modified electrode not only shows a highly stable ECL, but also shows an 8-fold increase of ECL intensity and a reduction of the overpotential of ca. 300 mV in the presence of K2S2O8 as co-reactant, compared with those of bare TiO2 NPs modified electrodes. The roles of Nafion coating on TiO2 NPs in the ECL process are proposed to be twofold: to provide refuge for the free radicals and to enhance the electron-hole recombination. Benefiting from its excellent ECL performance, the cationic exchange function of Nafion and the susceptible to being oxidized performance of dopamine (DA) by holes, the Nafion/TiO2 composite electrode could be used to sensitively and selectively detect DA with a detection limit of 1.0×10−11 M and a linear range of 1.0×10−11-6.0×10−7 M. The coexisting anionic species such as excess ascorbic acid show little interference on DA detection. [ABSTRACT FROM AUTHOR]

Abstract: We demonstrate herein a newly developed serum total cholesterol biosensor by using the direct electron transfer of cholesterol oxidase (ChOx), which is based on the immobilization of cholesterol oxidase and cholesterol esterase (ChEt) on potassium-doped multi-walled carbon nanotubes (KMWNTs) modified electrodes. The KMWNTs accelerate the electron transfer from electrode surface to the immobilized ChOx, achieving the direct electrochemistry of ChOx and maintaining its bioactivity. As a new platform in cholesterol analysis, the resulting electrode (ChOx/KMWNTs/GCE) exhibits a sensitive response to free cholesterol, with a linear range of 0.050–16.0μmolL−1 and a detection limit of 5.0nmolL−1 (S/N=3). Coimmobilization of ChEt and ChOx (ChEt/ChOx/KMWNTs/GCE) allows the determination of both free cholesterol and esterified cholesterol. The resulting biosensor shows the same linear range of 0.050–16.0μmolL−1 for free cholesterol and cholesteryl oleate, with the detection limit of 10.0 and 12.0nmolL−1 (S/N=3), respectively. The concentrations of total (free and esterified) cholesterol in human serum samples, determined by using the techniques developed in the present study, are in good agreement with those determined by the well-established techniques using the spectrophotometry. [Copyright &y& Elsevier]

Abstract: The enhanced visible absorbance related to electrochromic response (ECR) of CdS nanocrystals (NCs) thin film in aqueous solution was firstly investigated to elucidate the detailed electrochemiluminescence (ECL) mechanism of semiconductor NCs/H2O2 system. The recovery efficiency of ECR was found as the key factor to affect the intensity of ECL. This preliminary study between ECR and ECL of semiconductor NCs in aqueous solution can provide the profound guidance to fabricate enhanced “signal-off” kind ECL sensors to widen its application in analytical field. [Copyright &y& Elsevier]

Abstract: A novel photoelectrochemical immunosensor based on TiO2/CdS hybrid modified electrode was developed. The TiO2/CdS hybrid modified electrode was obtained by alternately dipping the TiO2 modified indium–tin oxide (ITO) electrode into the [Cd(NH3)4]2+ and S2− solution repeatedly. Compared with the routine method using Cd2+ solution for CdS deposition, the as obtained TiO2/CdS electrode showed enhanced photocurrent intensity with fewer coating times. After the ITO/TiO2/CdS electrode was coated with chitosan (CS), α-fetoprotein (AFP) antibodies were covalently conjugated on the surface of the electrode. Thus, a label-free photoelectrochemical immunosensor for the detection of AFP was developed by monitoring the changes in the photocurrent signals of the electrode resulting from the immunoreaction. The immunosensor displayed a linear response to AFP in the ranges from 50pg/mL to 50ng/mL with a relatively low detection limit of 40pg/ml. The photoelectrochemical results for the detection of AFP in five human sera showed acceptable accuracy. The method is simple, sensitive and specific. Moreover, the studied immunosensor possessed acceptable reproducibility and storage stability. The proposed methodology was potentially attractive for clinical immunoassay. [Copyright &y& Elsevier]

Abstract: An ultrathin platinum film is fabricated on a nanoporous gold (NPG) scaffold through a catalytic chemical deposition method. The morphology and active surface area of the deposited Pt film, which will greatly influence the electro-catalytic properties of the catalyst, can be controlled by adjusting the deposition condition. Compared with bare NPG and high Pt loaded NPG, the performances of methanol electro-oxidation on the low-Pt-content bimetallic film are greatly improved, both in its catalytic current enhancement and signal stability. The best condition for methanol oxidation can be achieved when the area ratio of deposited Pt and uncovered Au was 3:1. [Copyright &y& Elsevier]

Abstract: We report a simple approach for the selectively electrochemical sensing of cysteine (CySH) using β-MnO2 nanowires modified glassy carbon (GC) electrode via a direct and facile electrochemical co-deposition process with chitosan hydrogel. The electrode showed excellent electrocatalytic effect toward cysteine oxidation. A possible reaction mechanism related to the formation of surface complexes was proposed: the –SH group is the reacting group in the reaction between cysteine and MnO2, while the –NH2 group acts as an anchor to stabilize the surface complexes. The electrocatalytic behavior is further developed as a sensitive detection scheme for cysteine by amperometric measurement, which shows a large determination range of 0.5–630μM and a low detection limit of 70nM. Other nineteen amino acids in a 20-fold concentration do not interfere in the detection of cysteine. Furthermore, other biological species containing –SH group or Ssuch as glutathione, cystine, and bovine serum albumin (BSA), show no interferences because of steric hindrance and inactive S/ce:simple-para> [Copyright &y& Elsevier]

Abstract: Dopamine-coordinated photoactive TiO2 nanoporous films with a wide excitation range of light in the visible region (up to 580nm) were prepared and used for sensitive detection of NADH. Colloidal TiO2 was firstly covered on an indium–tin oxide (ITO) electrode surface and sintered at 450°C to form a nanoporous TiO2 film, then the electrode was dipped in a dopamine solution to form a dopamine–TiO2 charge transfer complex via coordinating dopamine with undercoordinated titanium atoms on the electrode surface. This charge transfer complex provided an anodic photocurrent under visible light and the photocurrent could be largely enhanced by NADH. The photocurrent enhancement might be due to the electron transfer between NADH and the holes localized on dopamine. A new photoelectrochemical methodology for sensitive detection of NADH at a relatively low potential was developed. The detection limit of NADH was 1.4×10−7 M, and the detection range could extend up to 1.2×10−4 M. The dopamine–TiO2 modified electrode exhibits its major advantages such as effective electronic transducer, fast response and easy fabrication for photoelectrochemical determination of NADH. This strategy largely reduces the destructive effect of UV light and the photogenerated holes of illuminated TiO2 to biomolecules and opens a new avenue for the applications of TiO2 in photoelectrochemical biosensing. [Copyright &y& Elsevier]

Abstract: A simple one-step biomimetic coprecipitation method is reported to prepare a protein based biosensor by immobilizing calcium phosphate/hemoglobin composite nanoparticles directly onto glassy carbon electrode surface. Atomic force microscopy (AFM), attenuated total reflection spectra (ATR) and electrochemical method were used to characterize the as-prepared composite nanoparticles. Hb in the composite film kept their biological activity well, realized its direct electrochemistry with the formal potential of −0.363V in pH 7.0 phosphate buffer solution and gave excellent electrocatalytic performance to the reduction of hydrogen peroxide, by which the mediator-free biosensors could be fabricated. Compared to other immobilization methods, this system not only avoids the tedious synthesis of nanoparticles and the use of reagent detrimental to biomolecules but also possesses the advantages of simple preparation and low cost. [Copyright &y& Elsevier]

Abstract: A novel bi-functional sensor, based on CdS nanocrystals (NCs) and hemoglobin (Hb) multilayer films, designated as {Hb/CdS} n , modified glassy carbon electrode (GCE) by layer-by-layer (LbL) assembly, has been presented. The electrogenerated chemiluminescence (ECL) and electrochemical properties of {Hb/CdS} n have been investigated in detail. Hb in the multilayer films can enhance the stability of electrogenerated species of CdS NCs, and CdS NCs can also promote the direct electron transfer between Hb and GCE. As a consequence experimentally, the multilayer films modified GCE is suitable to be used as a bi-functional sensor, ECL sensor and electrochemical sensor, to determine H2O2 in obviously different concentration. In high concentration of H2O2, this sensor as an ECL sensor shows a linear response from 15μM up to 18mM. In the lower concentration of H2O2, it as an amperometric one shows two linear ranges of amperometric responses to the concentration of H2O2 ranging from 6.0 to 31.0μM and from 6.0μM down to 40nM with a detection limit of 20nM, based on the high stability of ECL by {Hb/CdS} n and the excellent electrocatalytical ability of Hb to H2O2. Thus, {CdS/Hb} n modified electrodes would have a great merit to expand the application of biosensors to life science and environmental science. [Copyright &y& Elsevier]

Abstract: In this paper, a simple and green modification method is developed for biomolecules analysis on poly(dimethylsiloxane) (PDMS) microchip with successful depression of nonspecific biomolecules adsorption. O-[(N-succinimdyl)succiny]-o’-methyl-poly(ethylene glycol) was explored to form hydrophilic surface via in-situ grafting onto pre-coated chitosan (Chit) from aqueous solution in the PDMS microchannel. The polysaccharide chains backbone of Chit was strongly attracted onto the surface of PDMS via hydrophobic interaction combined with hydrogen bonding in an alkaline medium. The methyl-poly(ethylene glycol) (mPEG) could produce hydrophilic domains on the mPEG/aqueous interface, which generated brush-like coating in this way and revealed perfect resistance to nonspecific adsorption of biomolecules. This strategy could greatly improve separation efficiency and reproducibility of biomolecules. Amino acids and proteins could be efficiently separated and successfully detected on the coated microchip coupled with end-channel amperometric detection at a copper electrode. In addition, it offered an effective means for preparing biocompatible and hydrophilic surface on microfluidic devices, which may have potential use in the biological analysis. [Copyright &y& Elsevier]

Abstract: Using chitosan as an effective linker between CMK-3 and glassy carbon electrode surface, {Hb/CMK-3} n multilayer film-modified electrodes were constructed through layer-by-layer assembly. The morphology of thus-formed {Hb/CMK-3} n film was characterized by scanning electron micrographs, and the interaction of hemoglobin (Hb) with CMK-3 was studied by UV–vis spectroscopy and electrochemical methods. Under optimal conditions, {Hb/CMK-3}6 film showed a couple of stable and well-defined redox peaks at about −377 and −296mV in pH 7.0 buffers. Furthermore, the {Hb/CMK-3}6 film displayed excellent electrocatalysis to the reduction of both H2O2 and O2. Based on thus-formed film and its direct electron transfer behavior, a novel biosensor was presented for the determination of H2O2 ranging from 1.2 to 57μM with the detection limit of 0.6μM at S/N=3. CMK-3 provided a desirable matrix for protein immobilization and biosensor preparation. [Copyright &y& Elsevier]

Abstract: The interest in microchip capillary electrophoresis (μ-CE) with electrochemical detection (ECD) has increased considerably because ECD offers perfect features for μ-CE, including remarkable sensitivity, inherent miniaturization and portability, low cost, low-power requirements and great compatibility with microfabrication technologies. This review focuses on recent advances in integrating ECD, especially amperometric detection, with μ-CE. We discuss in detail effects of the separation electric field and development of strategies for isolating and not isolating detection from the separation electric field. We expect that μ-CE-ECD will become a powerful tool for clinical diagnostics, environmental monitoring and biological assays. [Copyright &y& Elsevier]

Abstract: In this paper, a poly(dimethylsiloxane) (PDMS) microchip with electrochemical (EC) detection was developed for rapid separation and detection of morphine and codeine. It was found that morphine and codeine were well separated within 140s in phosphate buffer solution (PBS) (pH 6.6, 40mM)–β-cyclodextrin (β-CD) (20mM)–acetonitrile (30%, v/v). The detection limit was 0.2μM for morphine and 1μM for codeine. The protocol was successfully applied to monitoring the amount of morphine and codeine in human urine. Compared with the conventional methods, the presented method had many advantages such as lower instrument cost, less reagent consumption and shorter analysis time. [Copyright &y& Elsevier]

Abstract: Boron-doped diamond has drawn much attention in electrochemical sensors. However there are few reports on non-doped diamond because of its weak conductivity. Here, we reported a glucose biosensor based on electrochemical pretreatment of non-doped nanocrystalline diamond (N-NCD) modified gold electrode for the selective detection of glucose. N-NCD was coated on gold electrode and glucose oxidase (GOx) was immobilized onto the surfaces of N-NCD by forming amide linkages between enzyme amine residues and carboxylic acid groups on N-NCD. The anodic pretreatment of N-NCD modified electrode not only promoted the electron transfer rate in the N-NCD thin film, but also resulted in a dramatic improvement in the reduction of the dissolved oxygen. This performance could be used to detect glucose at negative potential through monitoring the current change of oxygen reduction. The biosensor effectively performs a selective electrochemical analysis of glucose in the presence of common interferents, such as ascorbic acid (AA), acetaminophen (AP) and uric acid (UA). A wide linear calibration range from 10μM to 15mM and a low detection limit of 5μM were achieved for the detection of glucose. [Copyright &y& Elsevier]

Abstract: Here we reported a novel microfluidic biosensor with an on-column immobilized enzyme microreactor. The fabrication approach of this biosensor is simple and the enzyme microreactors with controlled sizes can be placed at any desired position on the microchip. Taking glucose oxidase (GOx) as an example, electroosmotic flow (EOF) as a driving force and amperometry as a detection method, the performance of biosensors were modulated by changing the length of enzyme reactor from 0.5cm to 3cm, and the linear ranges were changed from 0–8.0mM to 0–30.0mM with the detection limits from 42μM to 6.5μM. The enzyme reactor remained its 65% activity after 23 days storage. It also showed good anti-interference ability and was used to quantify glucose in human serum samples. [Copyright &y& Elsevier]

Abstract: Tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)3 2+)–Zirconia–Nafion composite modified glassy carbon disk electrode as a solid-state electrochemiluminescence (ECL) detector is successfully applied to an electrophoretic microchip system with a wall-jet configuration. Pharmaceuticals such as tramadol, lidocaine and ofloxacin were selected to characterize the performance of this microchip capillary electrophoresis (CE)–ECL detection system. Voltammetric and ECL behaviors of immobilized Ru(bpy)3 2+ were investigated in lidocaine system. Influences of the separation electric field to cyclic voltammograms (CVs) of the immobilized Ru(bpy)3 2+ were also investigated. Tramadol, lidocaine and ofloxacin can be baseline separated without any additives. The detection limits (S/N=3) were 2.5×10−5 molL−1 for tramadol, 5.0×10−6 molL−1 for lidocaine, 1.0×10−5 molL−1 for ofloxacin under the sample injection of picoliters, and the linear ranges were from 5.0×10−5 to 2.5×10−3 molL−1 for tramadol, 1.0×10−5 to 1.0×10−3 molL−1 for lidocaine, and 1.0×10−5 to 2.5×10−3 molL−1 for ofloxacin, respectively. [Copyright &y& Elsevier]

Abstract: An easy and universal wall-jet configuration for microchip CE-ECL detection system was constructed and investigated in this work. Two detection modes of pre-column and post-column were applied to the above system. TPA, tramadol and lidocaine were chosen as model analytes to estimate the system in both modes. The important operational parameters such as the concentration of luminescent reagent and the distance between the separation outlet and the working electrode were optimally obtained and compared for the first time. [Copyright &y& Elsevier]

Abstract: The strong interactions between poly(dimethylsiloxane) (PDMS) surface and amino acids result in unavoidable adsorption on channel surface. This paper described a simple method to decrease adsorption of analytes by dynamic coating of the PDMS surface. When nonionic surfactant (Tween 20) was added in running buffer as dynamic modifier, electroosmotic flow (EOF) was well-suppressed. Moreover, arginine (Arg), proline (Pro), histidine (His) and threonine (Thr) were successfully separated within 80s in a 3.7cm long separation channel and then detected with an end-channel amperometric detection mode at a copper electrode. Under the optimal conditions, the linear ranges of Arg, Pro, His and Thr were all from 50 to 600μM with detection limits of 13.6, 15.3, 10.6 and 12.8μM, respectively. The relative standard deviations (R.S.D.s) of run-to-run, day-to-day and chip-to-chip on the coated PDMS/PDMS microchip were all below 2.4%. Tween 20 dynamic coating provides reproducible amino acids separations with good performances. [Copyright &y& Elsevier]

Abstract: A straightforward, rapid and “green” approach was proposed for the fabrication of gold nano-structured films. A gold electrode was firstly oxidized under a high potential of 10V, and β-d-glucose, as a nontoxic reducing agent, was then chosen to reduce the gold oxide. This process gives a fractal gold nanofilm on the top of the gold electrode in a way of completely “green” chemistry. X-ray photoelectron spectroscopy, atomic force microscopy, scanning electron microscopy and electrochemical methods were adopted to characterize the as-prepared gold nanofilm. The gold nanofilm was found to have abundant adatom state Au∗, evidenced by the electrochemical process of Au∗/Au∗OHads couple. The as-prepared gold nanofilm greatly facilitates the electrochemical oxidation of glucose in neutral solutions. As the gold nanofilm was formed in situ on the gold electrode, additional immobilization procedures are not necessary. A sensitive enzyme-free sensor can be easily developed for the detection of glucose in pH 7.4 phosphate buffer solution, which gives linear ranges up to 57.5 and 30mM with detection limits down to 0.75 and 3.6μM at potential of +0.3 and −0.15V, respectively. A rapid response for glucose could be achieved in less than 2s. At a detection potential of −0.15V, physiological interference agents such as ascorbic acid, uric acid and acetylaminophenol were efficiently excluded. [Copyright &y& Elsevier]

Abstract: We report on the formation of colloidal biocomposites resulting from the electrostatic self-assembly of negatively charged lactate oxidase (LOD) and oppositely charged nanoscaled cobalt phthalocyanine (NanoCoPc) colloid under enzyme-friendly conditions. The biocomposites were further used to fabricate lactate biosensors due to their excellent film-forming ability and strong adsorbability on the surface of glassy carbon electrode. The electrochemical assays of such films revealed a large capacity of NanoCoPc for the retention of LOD. Here, NanoCoPc colloid was not only used as carriers for immobilization of LOD, but also displayed intrinsic electrocatalytic activity for the oxidation of H2O2, a product of enzymatic reaction. A chitosan film containing MnO2 nanoparticles was further electrodeposited as an external layer, which could effectively eliminate the interference from ascorbic acid. Under optimal conditions, the biosensor showed a wide linear response to lactate in the range of 0.020–4.0mM, with high sensitivity (3.98μAcm−2 mM−1), as well as good reproducibility and long-term stability. The biosensor has been used for the determination of lactate in real samples with an acceptable accuracy. [Copyright &y& Elsevier]

Abstract: Poly(dimethylsiloxane) (PDMS) microfluidic channels modified by citrate-stabilized gold nanoparticles after coating a layer of linear polyethylenimine (LPEI) were successfully used to separate dopamine and epinephrine, which were difficult to be separated from baseline in native and hybrid PDMS microchannels. In-channel amperometric detection with a single carbon fibre cylindrical electrode was employed. Experimental parameters of separation and detection processes were optimized in detail. The analytes were well separated within 100s in a 3.7cm long separation channel at a separation voltage of +800V using a 30mM phosphate buffer solution (PBS, pH 7.0). Linear responses of them were obtained both from 25 to 600μM with detection limits of 2μM for dopamine and 5μM for epinephrine, respectively. The modified PDMS channels have a long-term stability and an excellent reproducibility within 2 weeks. [Copyright &y& Elsevier]

Abstract: A biocompatible, nanoporous ZnO film was prepared on graphite electrode by the simple electrodeposition method. Based on the film’s strong adsorption ability and friendly microenvironment, it can be used as a good matrix to immobilize myoglobin (Mb) through simple adsorption. Moreover, the entrapped Mb realized direct electron transfer with the electrode and displayed an elegant catalytic activity toward the reduction of hydrogen peroxide, nitrite, and trichloroacetic acid, by which the mediator-free biosensors could be fabricated. Atomic force microscopy, UV-Vis spectra, electrochemical impedance spectroscopy, and cyclic voltammetry, etc. were used to characterize the nanoporous ZnO film and Mb-modified ZnO film. Compared to other methods, electrodeposition of porous material supplied a more simple and convenient approach to prepare biocompatible materials for biosensors. [Copyright &y& Elsevier]

Abstract: This report described proteins modification of poly(dimethylsiloxane) (PDMS) microfluidic chip based on layer-by-layer (LBL) assembly technique for enhancing separation efficiency. Two kinds of protein-coated films were prepared. One was obtained by successively immobilizing the cationic polyelectrolyte (chitosan, Chit), gold nanoparticles (GNPs), and protein (albumin, Albu) to the PDMS microfluidic channels surface. The other was achieved by sequentially coating lysozyme (Lys) and Albu. Neurotransmitters (dopamine, DA; epinephrine, EP) and environmental pollutants (p-phenylenediamine, p-PDA; 4-aminophenol, 4-AP; hydroquinone, HQ) as two groups of separation models were studied to evaluate the effect of the functional PDMS microfluidic chips. The results clearly showed these analytes were efficiently separated within 140s in a 3.7cm long separation channel and successfully detected with in-channel amperometric detection mode. Experimental parameters in two protocols were optimized in detail. The detection limits of DA, EP, p-PDA, 4-AP, and HQ were 2.0, 4.7, 8.1, 12.3, and 14.8μM (S/N=3) on the Chit–GNPs–Albu coated PDMS/PDMS microchip, and 1.2, 2.7, 7.2, 9.8, and 12.2μM (S/N=3) on the Lys–Albu coated one, respectively. In addition, through modification, the more homogenous channel surface displayed higher reproducibility and better stability. [Copyright &y& Elsevier]

Abstract: Fe3O4 magnetic multilayer films were constructed on several conductive bases (glassy carbon electrode, ITO glass and Al foil) by the firstly electrodeposited chitosan/Fe3O4 nanoparticles thin film and then the layer-by-layer assembly using phytic acid and Fe3O4/chitosan. Scanning electronic microscopy (SEM), UV–vis spectra, electrochemical impedance spectroscopy (EIS) and superconducting quantum interference device (SQUID) measurements were used to characterize the multilayer films. Characteristic superparamagnetic properties of Fe3O4 nanoparticles are well remained in the film and could be controlled simply by changing the assembly layers. Moreover, the multilayer film showed good biocompatibility, the adsorbed hemoglobin (Hb) on the film realized direct electron transfer with the underlying GCE and kept high catalytic activity. This presented system avoid the complex synthesis for protecting Fe3O4 nanoparticles, and supplies a simple, universal way to construct other nanoparticles films on many conductive bases for biosensors’ development. [Copyright &y& Elsevier]

Abstract: A novel hemoglobin (Hb) electrode has been presented through adsorbed Hb onto mesoporous tungsten oxide via one-step electrodeposition. Positions of Soret absorption band showed Hb retained its natural configuration on the resulting films. Electrochemical impedance spectroscopy and cyclic voltammetry were employed to study the electrochemical behavior of adsorbed Hb. The immobilized Hb showed a pair of stable and well-defined peaks at about −284 and −174mV at 100mVs−1 in pH 6.0 buffers and displayed excellent electrocatalytical responses to the reduction of H2O2, and trichloroacetic acid. The presence of meso-WO3 film greatly enhances the protein loadings, accelerates interfacial electron transfer and improves thermal stability of the adsorbed protein. [Copyright &y& Elsevier]

Abstract: This paper reports on the study of electroosmotic flow (EOF) in poly(dimethylsiloxane) (PDMS) microchannels on the basis of indirect amperometric detection method. Gradual increase of EOF rate in freshly prepared PDMS microchannels was observed with the running buffer of phosphate buffer solution (PBS). With the same concentration (10mM) of PBS containing different cations and the same pH value (7.0) and, the time of the stable EOF in PDMS microchannels under the applied separation voltage of 1000V was 49.8 s (Li+-PBS), 57.1s (Na+-PBS), 91s (K+-PBS), respectively. Meanwhile, the different adsorption of cations (Li+, Na+ and K+) on hydrophobic PDMS wall was observed through their separation in PDMS microchannels. Such experimental results demonstrated that the EOF in PDMS microchannels came from the cations and anions adsorbed on PDMS wall. This study would not only help us understand the surface state of PDMS, but also provide a useful guidance for establishing the effective surface modification methods in PDMS microchip CE. [Copyright &y& Elsevier]

Abstract: Detection of native amino acids was accomplished using a capillary electrophoresis (CE)–amperometric detection system, in which a single carbon fiber cylinder (CFC) working electrode instead of a carbon fiber disc (CFD) electrode was mounted in the end part of a poly(dimethylsiloxane) (PDMS)/glass hybrid microchannel. Similar to that using CFD working electrode, here, the electrochemical reduction reaction at the working electrode is also coupled from the separation high voltage system, the coupling degree is related to the in-channel length of the CFC. This property simplifies the fabrication procedure of the working electrode and also provides a convenient and sensitive means for the determination of non-electroactive ions by amperometry. The present detection mode is successfully used to electrochemically detect non-electroactive arginine (Arg), threonine (Thr), glutamic acid (Glu) and electroactive cysteine (Cys). Furthermore, by simply changing the detection potential, we can easily distinguish peak mobilities of electroactive amino acids from that of non-electroactive amino acids. [Copyright &y& Elsevier]

Abstract: The direct electron transfer of hemoglobin (Hb) was successfully realized on Au–zirconium phosphate nanocomposite (Au–ZrP) modified glassy carbon electrode (GCE) based on the synergistic effect between ZrP and Au nanoparticles. The interaction between Hb and Au–ZrP was studied by UV–Vis spectroscopy, electrochemical impedance spectroscopy, and cyclic voltammetry. A couple of stable and well-defined redox peaks of Hb immobilized on Au–ZrP was observed at about −134 and 35mV in pH 6.0 buffers. Moreover, the immobilized Hb showed excellent electrocatalysis to the reduction of H2O2, which was used to construct H2O2 sensors. The obtained sensor could determine H2O2 from 15μmoll−1 to 0.48mmoll−1 with detection limit of 7.4μmoll−1(S/N =3). Its apparent Michaelis–Menten constant, , was 0.65mmoll−1. [Copyright &y& Elsevier]

Abstract: A novel solid-contact potentiometric sensor for ascorbic acid based on cobalt phthalocyanine nanoparticles (NanoCoPc) as ionophore was fabricated without any need of auxiliary materials (such as membrane matrix, plasticizer, and other additives). The electrode was prepared by simple drop-coating NanoCoPc colloid on the surface of a glassy carbon electrode. A smooth, bright and blue thin film was strongly attached on the surface of the glassy carbon electrode. The electrode showed high selectivity for ascorbic acid, as compared with many common anions. The influences of the amount of NanoCoPc at the electrode surface and pH on the response characteristics of the electrode were investigated. To overcome the instability of the formal potential of the coated wire electrode, a novel electrochemical pretreatment method was proposed for the potentiometric sensor based on redox mechanism. This resulting sensor demonstrates potentiometric response over a wide linear range of ascorbic acid concentration (5.5×10−7 to 5.5×10−2 M) with a fast response (<15s), lower detection limit (ca. 1.0×10−7 M), and a long-term stability. Furthermore, microsensors based on different conductors (carbon fiber and Cu wire) were also successfully fabricated for the determination of practical samples. [Copyright &y& Elsevier]

Abstract: The interactions between proteins and Ponceau 4R (PR) in aqueous solution have been studied by the techniques of resonance light scattering (RLS) spectroscopy, the absorption spectroscopy, zeta potential assay and circular dichroism (CD) spectrum. The dry PR can assemble on the surface of protein via electrostatic and hydrophobic forces to produce an associated compound of protein-PR, this compound can enhance the RLS of protein. Based on this fact, a simple, rapid, and sensitive method has been developed for the determination of proteins at nanogram level by RLS technique with a common spectrofluorimeter. Under optimum conditions, the linear range is 0.10–39.2μgmL−1 for the determination of both bovine serum albumin (BSA) and human serum albumin (HSA). The detection limits (S/N=3) are 6.96ngmL−1 for BSA and 5.71ngmL−1 for HSA, respectively. There is almost no interference from amino acids, most of the metal ions, and other coexistent substances. The method has been satisfactorily applied to the direct determination of the total protein in human serum. [Copyright &y& Elsevier]

Abstract: A new strategy for immobilization of horseradish peroxidase (HRP) has been presented by self-assembling gold nanoparticles on chitosan hydrogel modified Au electrode. From a mildly acidic chitosan solution, a chitosan film is electrochemically deposited on Au electrode surface via a negative voltage bias. This process is accompanied by the hydrogen evolution reaction, and the released hydrogen gas made the deposited chitosan film with porous structure, which facilitates the assembly of gold nanoparticles and HRP. The resulting substrates were characterized by atomic force microscopy (AFM) and electrochemical impedance spectroscopy (EIS). The immobilized HRP displayed an excellent catalytic property to the reduction of H2O2 in the presence of methylene blue mediator. The resulting biosensor (HRP-modified electrode) showed a wide dynamic range of 8.0μM–15mM H2O2, and the linear ranges were 8.0μM–0.12mM and 0.50–12mM, with a detection limit of 2.4μM estimated at a signal-to-noise ratio of 3. Moreover, the biosensor remained about 85% of its original sensitivity after four weeks’ storage. [Copyright &y& Elsevier]

Abstract: The Au particles have been intercalated within the gallery spaces of Zn–Al layered double hydroxides (LDHs). Synthesis of this material was obtained by ion-exchange of the LDH-nitrate precursor with AuCl4 − anion followed by reduction with the sodium citrate. Elemental analysis, X-ray diffraction, X-ray photoelectron spectroscopy (XPS), TEM and N2 sorption analyses have been used to characterize the material. TEM micrographs of LDH-Au revealed a typical porous material. Chemical analysis results showed that AuCl4 − anions exchanged with nitrate anions. XPS analysis confirmed the deoxidization of the AuCl4 − anions in the gallery after treatment with the sodium citrate. The XRD diffraction patterns of LDH-Au revealed that the layer structure is maintained after all synthetic steps. The XPS spectra, the elemental results and the TEM patterns proved the intercalation of Au particles into the gallery. [Copyright &y& Elsevier]

We report on the utilization of a novel nanoscaled cobalt phthalocyanine (NanoCoPc)–glucose oxidase (GOD) biocomposite colloid to create a highly responsive glucose biosensor. The biocomposite colloid is constructed under enzyme-friendly conditions by adsorbing GOD molecules on CoPc nanoparticles via electrostatic interactions. The glucose biosensor can be easily achieved by casting the biocomposite colloid on a pyrolytic graphite electrode (PGE) without any auxiliary matter. It has been found that GOD can be firmly immobilized on PGE surface and maintain its bioactivity after conjugating with NanoCoPc. NanoCoPc displays intrinsic electrocatalytic ability to the oxidation of the product of enzymatic reaction H2O2 and shows a higher catalytic activity than that of bulk CoPc. Under optimal conditions, the biosensor shows a wide linear response to glucose in the range of 0.02–18 mM, with a fast response (5 s), high sensitivity (7.71 μA cm-2 mM-1), as well as good thermostability and long-term life. The detection limit was 5 μM at 3σ. The general interferences coexisted in blood except ascorbic acid and l-cysteine do not affect glucose determination, and further coating Nafion film on the surface of the biosensor can effectively eliminate the interference from ascorbic acid and l-cysteine. The biosensor with Nafion film has been used for the determination of glucose in serum with an acceptable accuracy. [Copyright &y& Elsevier]

A glucose detection approach based on the concept of electrochemical depletion of electroactive species in diffusion layer was established, using scanning electrochemical microscopy (SECM). By controlling the glucose oxidase (GOD) modified electrode (substrate electrode) at a proper potential of electrochemical oxidation of interfering electroactive species, i.e., ascorbic acid (AA), an interference-free microcircumstance was formed in the diffusion layer of the substrate electrode. Consequently, we could successfully sense hydrogen peroxide generated from an enzymatic reaction by locating a Pt ultramicroelectrode (UME) (tip electrode, 5 μm in radius) into the diffusion layer of the substrate electrode. Properties of this interference-removing approach based on electrochemical depletion were systematically investigated. Results showed that the interference-removing efficiency was significantly determined by the tip-substrate distance and substrate potential. When the tip-substrate distance was 11 μm (2.2 times of the tip electrode radius) and the substrate potential was 0.5 V, nearly 90% of AA (0.5 mM) could be depleted within 30 s without consumption of H2O2. Under these conditions, 0.1 mM AA showed no influence on the detection of 0.5 mM glucose. The linear range of glucose detection is 0.01–1 mM with a detection limit (DL) of 0.005 mM (correlation coefficient is 0.9948). This research will open a new way for developing selective micro-biosensors. [Copyright &y& Elsevier]

An amperometric biosensor for the quantitative measurement of glucose is reported. The biosensor is based on a biocomposite that is homogeneous and easily prepared. This biocomposite is made of chitosan hydrogel, glucose oxidase, and gold nanoparticles by a direct and facile electrochemical deposition method under enzyme-friendly conditions. The resulting biocomposite provided a shelter for the enzyme to retain its bioactivity at considerably extreme conditions, and the decorated gold nanoparticles in the biocomposite offer excellent affinity to enzyme. The biosensor exhibited a rapid response (within 7s) and a linear calibration range from 5.0μM to 2.4mM with a detection limit of 2.7μM for the detection of glucose. The combination of gold nanoparticles affinity and the promising feature of the biocomposite with the onestep nonmanual technique favor the sensitive determination of glucose with improved analytical capabilities. [Copyright &y& Elsevier]

A chitosan film containing MnO2 nanoparticles was introduced to amperometric glucose biosensors for the elimination of the interference from ascorbic acid. Chitosan was mixed with MnO2 nanoparticles and electrochemically deposited on electrodes previously modified with glucose oxidase. MnO2 nanoparticles incorporated in the chitosan film was very stable and can effectively oxidize AA to electrochemical inactive product, and thus eliminate the interference of AA on the glucose biosensors based on the direct oxidation of hydrogen peroxide. The effect of the content of MnO2 nanoparticles and the deposition time on the characteristics of the film, as well as the stability of the film during continuous exposure to AA was investigated. Glucose biosensors deposited with the film containing MnO2 nanoparticles were suitable for determination of glucose in the presence of AA. [Copyright &y& Elsevier]

Based on the comprehensive analyses of the experimental results of the electrochemical methods, in situ UV-Vis absorption spectra, in situ electron spin resonance (ESR), and attenuated total-internal reflection (ATR) as well as the calculation of UV-Vis absorption data by PM3 Semi-Empirical method, a reaction mechanism for the redox processes of dobutamine was presented. When the anodic sweep is carried out, dobutamine firstly undergoes a free radical reaction with one-electron and one-proton to form semi-quinone free radicals, which will continuously convert to its corresponding quinone form by further electrochemical oxidation reaction. The formed quinone cannot only undergo a cyclization process by chemical reaction to produce a new compound, which can be reduced at more negative potential, but also be reduced to form dobutamine again when subsequent cathodic sweep is followed. The cyclization rate is depended upon pH values, and it increases with the increase of pH. In neutral medium, the corresponding oxidation form of the cyclization reaction product is easy to convert to melanin. [Copyright &y& Elsevier]

It is essential for the information storage in DNA-based bio-chips to construct a reversible exchange interface of DNA. Here, a highly reproducible and reversible adsorption–desorption interface of DNA based on the nano-sized zirconia in different pH solution was successfully fabricated. The results showed that DNA can be adsorbed onto the nano-sized zirconia from its solution, and can desorb from the nanoparticles in 0.10 M KOH solution. When the matrix with nanoparticles returns to the DNA solution again, DNA can be re-adsorbed onto them as initial state. Moreover, the interaction of DNA with non-electroactive molecules, 2,2′-bipyridine, has been studied by electrochemistry method in the aid of probe Co(phen)33+. The experiments showed that when 2,2′-bipyridine was added into the test solution, the voltammetric peak currents of Co(phen)33+ decreased; and the decrease value of peak current against the concentration of 2,2′-bipyridine has a good Langmuir relationship, by which the equilibrium constant of interaction between 2,2′-bipyridine and DNA was estimated to be 1.57×104 M-1. [Copyright &y& Elsevier]

This paper presents an electrochemical detector for poly(dimethylsiloxane) (PDMS) microchip CE with a three-dimensional adjustor which makes it possible to accurately align a separate working electrode that can be easily fabricated in laboratory to the uncertain PDMS microchannel outlet. The substantial influence of the electrode—PDMS microchannel distance was investigated. The optimal electrode-outlet distance was found to be 10 μm for the PDMS microchannel with the width of 50 μm due to its relatively slow electroosmotic flow. Adrenaline and catechol were well separated, with a linear response range from 20 μM to 1 mM, and a detection limit of 2 μM for catechol, using carbon disk electrode (diameter of 300 μm). Furthermore, arginine and histidine can be well separated and detected directly in the PDMS microchannel using a Cu disk electrode (diameter of 150 μm). [Copyright &y& Elsevier]

An ascorbic acid (AA) sensor based on an ion-sensitive field-effect transistor (ISFET) was prepared by modifying the sensitive area of the transducer with MnO2 nanoparticles. An additional Nafion membrane coated on top of the sensor was used to immobilize the MnO2 nanoparticles and restrict the amount of ascorbic acid entering the membrane. The reaction of the MnO2 nanoparticles with ascorbic acid produced a local pH change, which was correlated with the ascorbic acid concentration and could be monitored by the ISFET. The linear range of the ascorbic acid sensor was 0.02–1.27 mM, and the detection limit was 0.01 mM. The effects of buffer concentration, pH, and ionic strength on the sensor performance were also examined. In addition, the sensor has good stability and reproducibility, and the construction and renewal of the sensor are simple and inexpensive. [Copyright &y& Elsevier]

Generally a glucose-sensitive enzyme field-effect transistor (ENFET) is based on local pH change in biomembranes resulted from the formation of gluconic acid. Here we proposed a glucose ENFET based on a new principle. The glucose ENFET was fabricated by coimmobilizing glucose oxidase (GOD) and MnO2 nanoparticles on the gate of an ion-sensitive field-effect transistor (ISFET). The proposed glucose biosensor shows a significant local pH increase in the sensitive membrane with the increase of glucose concentration. The driving force of the pH change in our sensor is essentially different from all the other glucose ENFETs, including those prepared by bulk MnO2. The special reaction ability of MnO2 nanoparticles with hydrogen peroxide might be the main cause of the pH change. In addition, the influence of buffer concentration, pH and ionic strength on the glucose ENFET is investigated in detail. It is found that the ionic strength has little effect on the performance of the ENFET. Under optimal conditions, the proposed ENFET exhibits a linear response with glucose in the range of 0.025–1.90 mM, an extended dynamic upper limit of 3.5 mM glucose, and considerable good reproducibility and stability. [Copyright &y& Elsevier]

Humic acid (HA) films were formed on a gold electrode surface by the self-assembly method. The HA films were used as an immobilization matrix interfacing cytochrome c (cyt c) to Au electrode surface through a dip and phase inversion process. The morphologies of the films, changes of structure and properties of the electrochemistry were investigated by scanning electron microscope (SEM), UV–Vis spectroscopy (UV–Vis) and electrochemical impedance spectroscopy (EIS) and cyclic voltammetry. The results showed that the HA film acted as a good adsorption matrix for cyt c and an excellent accelerant for the redox of cyt c which gives reversible redox peaks with a formal potential of 108 mV vs SCE in pH 7.0 phosphate buffer solution. The average surface coverage of cyt c on the HA film was about 3.49 × 10−11 mol/cm2, indicating a monolayer of cyt c. The electron transfer rate constant was calculated to be 1.0 s−1. [Copyright &y& Elsevier]

While remarkable progress has been made in developing enzyme field-effect transistors (ENFETs), the immobilization of enzymes remains a significant challenge. Recently, nanometer materials such as gold, silver and metal oxide nanoparticles have been widely used in biosensors because of their big surface area and good biocompatibility. However, there are few reports about fabricating biocatalytic layer on ENFETs with nanoparticles. Here, SiO2 nanoparticles were introduced into the construction of ENFET. A glucose-sensitive ENFET was fabricated based on the modification of the gate surface of ion-sensitive field-effect transistors (ISFETs) with SiO2 nanoparticles and glucose oxidase (GOD). Compared with the one without SiO2 nanoparticles, the proposed sensor shows obviously enhanced sensitivity and extended lifetime. It infers that SiO2 nanoparticles can provide a biocompatible environment and improve the enzyme activity, and prevent the immobilized enzymes from leakage as well. The linear range of the ENFET is 0.05–1.8 mM, and the detection limit is ca. 0.025 mM. The effects of buffer concentration, pH and ionic strength were also examined. The biosensor has good stability and reproducibility, and it can be used for the determination of glucose. [Copyright &y& Elsevier]