Direct electrochemistry of horseradish peroxidase on graphene-modified electrode for electrocatalytic reduction towards H2O2

Graphene was synthesized by a chemical method to reduce graphite oxide and well characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (PXRD) and Fourier transform infrared (FTIR) spectra. Horseradish peroxidase (HRP) immobilized on a graphene film glassy carbon electrode was found to undergo direct electron transfer and exhibited a fast electron transfer rate constant of 4.63 s⁻¹. The HRP-immobilized electrode was investigated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The CV results showed that the modified electrode gave rise to well-defined peaks in phosphate buffer, corresponding to the electrochemical redox reaction between HRP–Fe(III) and HRP–Fe(II). The obtained electrode also displayed an electrocatalytic reduction behavior towards H₂O₂. The new H₂O₂ sensor shows a linear range of 0.33–14.0 μM (R² = 0.9987) with a calculated detection limit of 0.11 μM (S/N = 3). Furthermore, the biosensor exhibits both good operational storage and storage stability.     

Synthesis and characterization of deoxyribonucleic acid (DNA) functionalized Multi-Walled Carbon Nanotube (MWCNT) doped Poly-Vinyl alcohol (PVA) nanocomposite film

ABSTRACT

Nanoparticles, carbon nanotubes and polymers are widely used nowadays to improve biosensing phenomenon. However, studies considering impact of their combination on biosensor sensitivity are rarely reported. Present work involves synthesis of thin films using different combinations and comparisons of their properties. The metal (silver nanoparticles)-polymer (PVA), MWCNT-polymer and Metal-MWCNT-polymer films were analyzed using optical, UV-visible and DMA studies. Prior Functionalization of MWCNTs to attach DNA was confirmed by FTIR and TEM. Metal-MWCNT-polymer film proved to show best mechanical properties and is expected to be useful in artificial tissues or sensing biological responses without electrodes, though, it requires profound interdisciplinary efforts.     

基于高分子化辅酶的脱氢酶修饰碳糊电极

制备了基于高分子化辅酶（PEI-Fc-NAD＋）的脱氢酶修饰碳糊电极。用直接混合法将高分子化辅酶、脱氢酶、碳粉与粘合剂适量混合,利用超声振荡得到均匀的碳糊,从而制得电极并利用循环伏安法进行表征。电化学实验表明高分子化的电子媒介体在电极表面的电极传递过程属于准可逆的电化学过程,而且电化学活性高分子化辅酶修饰电极后可以实现脱氢酶和电极之间的电子传递。     

分子技术快速检测食品有害微生物

介绍了几种生物分子技术如生物传感器、微排列、电子鼻子和纳米装置用于食品中有害微生物的检测。     

生物传感器的发展应用及前景

随着信息技术与生物工程技术的发展,生物传感器得到了极为迅速的发展,当今各发达国家都把生物传感器列为21世纪的关键技术,给予高度的重视。生物传感器不仅广泛用于传统医学领域,推动医学发展,而且还在空间生命科学、食品工业、环境监测和发酵工程等领域广泛应用。     

Characterization of the substructure and properties of immobilized peptides on silicon surface

Immobilization of biomaterials onto solid supports is a means of functionalizing materials for applications such as biosensing. Biologically active peptide (A-A-A-A-G-G-G-E-R-G-D)¹ films were attached to N-hydroxy succinimide ester terminated self-assembled monolayers (SAM) which were covalently linked to a smooth silicon surface via Si–C bonds. The peptide films were characterized using electrical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. The film structures were determined from examination of the capacitance and conductance dispersions with frequency. Analysis of XPS, EIS and FTIR after immobilization of the peptide film at pH 4 and 7 provided information on the extent of the activation and overall coupling efficiencies of the peptides to the N-hydroxy succinimide ester surface. The resulting film structure was markedly altered by attachment of the peptide at pH 4.     

Use of biosensor and impedance spectroscopy assays to investigate the influence of temperature on E. coli sensitivity to 3,5-dichlorophenol

Temperature is one of the most important factors influencing the sensitivity of bacteria to toxicants, but little work investigating the nature of the interaction between microbial cells, temperature and toxicants has been carried out. In this study a biosensor assay and an impedance spectroscopy assay were used to investigate different aspects of the temperature/toxicity interaction in Escherichia coli exposed to the model toxicant 3,5-dichlorophenol (3.5-DCP).The biosensor assay showed that E. coli metabolic rate increased significantly with increasing temperature, but the sensitivity of the cells to 3,5-DCP was significantly reduced at the higher test temperatures. The impedance assay indicated that whilst increasing temperature influenced the physiology of the E. coli cytoplasmic membrane, it had no significant effect on the sensitivity of the cells to 3,5-DCP.Overall the results of the two assays suggest that the manner in which temperature change influences E. coli sensitivity to 3,5-DCP is influenced by temperature induced changes in the metabolic rate of the cells, but not by changes in membrane physiology seen over the temperature range 15-35 °C. The use of two assays, measuring different biological endpoints was beneficial to examining the interaction between temperature and toxicity.     

基于白光干涉的纳米级生物膜层厚度测试的研究

提出了利用光学干涉原理在光纤传感器端面上直接测量生物免疫反应的方法，能够测试到纳米级厚度生物膜层的亚纳米级厚度增加量。将生物膜(如抗原)固定在光纤探针端面上，入射光在光纤生物层、以及生物层一空气的界面处两次反射，由于两束反射光之间存在光程差，所以产生干涉现象，通过分析干涉谱线可以测量出抗原层的厚度。当抗原和抗体发生免疫反应后，生物膜层的厚度产生变化，干涉谱线产生移动，通过检测干涉谱线的移动来判断样本溶液中是否存在待测抗体。能够测试出亚纳米级生物膜厚度的增加量。给出了测试曲线。该方法测试精度高，结果可靠，测试系统简单，具有较强的实用性，并能够进行实时测量。     

Influence of plasticizer configurational changes on the mechanical properties of highly plasticized poly(vinyl chloride)

The effects of configurational changes among nine plasticizers were studied using puncture tests. Ion-selective poly(vinyl chloride) (PVC) membranes were plasticized with three citrate-related compounds (Citroflex A-4 (CFA4), Citroflex A-6 (CFA6), and Citroflex B-6 (CFB6)) and six sebacate-related compounds (dimethyl sebacate (DMS), diethyl sebacate (DES), dibutyl sebacate (DBS), dioctyl sebacate (DOS), dioctyl azelate (DOZ), and dioctyl adipate (DOA)). The strengths, stiffnesses, and toughnesses of the membranes increased at low PHR ratios (which are defined as the actual concentrations of plasticizer to PVC divided by the minimum concentrations of plasticizer required to isolate all of the PVC polar groups) and then monotonically decreased as plasticizer was added above these ratios. The ductilities increased up to PHR ratios of about 2.0 and decreased above PHR ratios of about 4.0. The citrate-related compounds could not be distinguished according to the mechanical properties. The DMS-, DES-, and DOA-plasticized membranes were generally stronger and stiffer than the DBS-, DOS-, and DOZ-plasticized membranes, but the ductilities were reduced using DMS, DES, and DOA. A nomogram was constructed to predict the strength, based on the plasticizer selection and PHR ratio. The strengths, stiffnesses, and toughnesses of the membranes decreased as the log (ionic conductivity, σ) increased, and the ranking of the configurational differences was similar to those of the mechanical properties versus PHR ratio.