Comparison of RAFT‐derived poly(vinylpyrrolidone) verses poly(oligoethyleneglycol methacrylate) for the stabilization of glycosylated gold nanoparticles

Carbohydrates dictate many biological processes including infection by pathogens. Glycosylated polymers and nanomaterials which have increased affinity due to the cluster glycoside effect, are therefore useful tools to probe function, but also as prophylactic therapies or diagnostic tools. Here, the effect of polymer structure on the coating of gold nanoparticles is studied in the context of grafting density, buffer stability, and in a lectin binding assay. RAFT polymerization is used to generate poly(oligoethyleneglycol methacrylates) and poly(N‐vinylpyrrolidones) with a thiol end‐group for subsequent immobilization onto the gold. It is observed that poly(oligoethylene glycol methacrylates), despite being widely used particle coatings, lead to low grafting densities which in turn resulted in lower stability in biological buffers. A depression of the cloud point upon nanoparticle immobilization is also seen, which might compromise performance. In comparison poly(vinylpyrrolidones) resulted in stable particles with higher grafting densities due to the compact size of each monomer unit. The higher grafting density also enabled an increase in the number of carbohydrates which can be installed per nanoparticle at the chain ends, and gave increased binding in a lectin recognition assay. These results will guide the development of new nanoparticle biosensors with enhanced specificity, affinity, and stability. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 55, 1200–1208     

A review on environmental applications of chitosan biopolymeric hydrogel based composites

Abstract

Chitosan (CS) is being used for fabrication of low cost, biocompatible materials that have applicability in fields such as agriculture, biotechnology and environment. In Environmental research, one of the applications of CS based hydrogel composites are in form of biosorbents for eviction of toxic dyes, heavy metals and nutrients from effluent streams. The adsorption potential could be attributed to the reactive functional groups existing on the surface of CS. CS based materials can also be employed for oil/water separation, as a fertilizer carrier, in Microbial fuel cells as Electrolyte membrane and as Electrochemical/Biosensors for detecting and analyzing few environmental pollutants such as pesticides. The earlier review papers on the subject matter have concentrated mainly on dye and heavy metal removal without giving details of its utility in the field of electrochemistry and agriculture. Though the biopolymer holds numerous applications, it has not been discussed extensively. Thus, an attempt has been made to elucidate the current and potential applications of CS hydrogels and composites based on the efficacy it has shown in areas of removal of organic and inorganic contaminants such as dyes, heavy metals and nutrients, in agriculture, oil and water separation, Microbial Fuel cells and Electrochemical/Biosensors.

• HIGHLIGHTS

• Chitosan based hydrogel composites could be extensively used in the field of Environment Technology.

• The composites act as effective biosorbents for dye, heavy metal and nutrient removal because of the functional groups present on Chitosan’s surface.

• These can also be effectively used for oil/water separation and also as a fertilizer/pesticide carrier for their slow release.

• Chitosan based electrolytes can become a promising ecofriendly substitute for synthetic polymers in fuel cells.

• These biopolymers have also been researched upon as electrochemical/biosensors in recent years for detecting environmental pollutants.

     

铁氰化铈薄膜固载血红蛋白修饰的过氧化氢生物传感器的制备及性能

采用电化学沉积法将铁氰化铈(CeHCF)薄膜修饰于玻碳电极(GCE)表面,得到铁氰化铈薄膜修饰玻碳电极;将血红蛋白(Hb)固载于该修饰电极表面,成功制得了Hb/CeHCF/GCE过氧化氢生物传感器.考察了铁氰化铈薄膜修饰玻碳电极的氧化还原机理和制备条件,并对血红蛋白在电极上的电子传递过程进行了较为深入的研究.结果表明,铁氰化铈薄膜为血红蛋白提供了温和的固载环境,可实现血红蛋白与电极表面的直接电子转移,提高了血红蛋白的电化学活性;所制得的传感器对过氧化氢具有较高的催化响应和较强的稳定性.相关研究结果在生物医学和临床医学领域具有一定的借鉴意义.     

电化学生物传感器在环境监测中的应用及发展前景

简要介绍了电化学生物传感器的工作原理,重点论述了电化学生物传感器在环境监测领域的应用及其研究进展,主要包括水环境污染物和大气污染物的监测,以及农药残留的监测等.同时,对电化学生物传感器的发展方向及前景进行了展望.     

A Ready‐to‐Use Electrochemical Kit Design for the Diagnosis of Single Nucleotide Polymorphisms

In this study, for the first time a model electrochemical kit was constructed for the detection of a functional polymorphism in catechol‐O‐methyl transferase (COMT) gene which is important for diagnosis of neuropsychiatric disorders as Alzheimer disease. The disposable pencil graphite electrode (PGE) is designed as a “kit” and the probe DNA covered PGE can detect single nucleotide polymorphisms (SNPs) from real samples based on the guanine oxidation signal even after 5 months of kit preparation (150 days durability).The detection limit (S/N=3) of the biosensor was calculated as 1.18 pmol of synthetic target sequence and 6.09×10⁵ molecules of real samples in 30 min detection time.     

Molecularly Imprinted Polypyrrole for DNA Determination

In this study graphite electrodes modified by a thin DNA‐imprinted polypyrrole layer, which was able to bind specific target‐DNA, are reported. For this aim, electrochemical synthesis of polypyrrole was performed on a pencil graphite electrode by cyclic voltammetry (CV) or by potential pulse sequences (PPS). The modified electrode surface was used for electrochemical determination of target‐DNA by differential pulse voltammetry. According to our best knowledge this is a first report on the application of DNA‐imprinted polymer for the determination of target‐DNA. The results showed that the molecularly imprinted polypyrrole (MIPPy) layer that formed on the carbon electrode surface was sensitive for target‐DNA, while the nonimprinted polypyrrole layer was not sensitive to the same target‐DNA. Comparison of electrodes modified using PPS and CV techniques is presented.     

Electrochemical DNA biosensor for human papillomavirus 16 detection in real samples

An electrochemical DNA biosensor for human papillomavirus (HPV) 16 detection has been developed. For this proposed biosensor, l-cysteine was first electrodeposited on the gold electrode surface to form l-cysteine film (CYSFILM). Subsequently, HPV16-specific probe was immobilized on the electrode surface with CYSFILM. Electrochemistry measurement was studied by differential pulse voltammetry method (DPV). The measurement was based on the reduction signals of methylene blue (MB) before and after hybridization either between probe and synthetic target or extracted DNA from clinical samples. The effect of probe concentration was analyzed and the best results were seen at 1000 nM. The hybridization detection presented high sensitivity and broad linear response to the synthetic-target concentration comprised between 18.75 nM and 250 nM as well as to a detection limit of 18.13 nM. The performance of this biosensor was also investigated by checking probe-modified electrode hybridization with extracted DNA from samples. The results showed that the biosensor was successfully developed and exhibited high sensitivity and satisfactory selectivity to HPV16. These results allow for the possibility of developing a new portable detection system for HPVs and for providing help in making an effective diagnosis in the early stages of infection.     

Comparison of BOD optical fiber biosensors based on different microorganisms immobilized in ormosil matrixes

Fiber-optical microbial sensors for determination of biochemical oxygen demand (BOD) are described. Sensing films consisting of layers of an oxygen-sensitive fluorescent material and two different kinds of seawater microorganisms immobilized in poly(vinyl alcohol) sol–gel matrix were investigated. Tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) perchlorate was used as the oxygen fluorescent quenching indicator. After preconditioning, the BOD biosensors could consistently perform well for up to one month. For films of domestic bacilli and films of sieved bacteria from seawater, the linear fluctuant coefficients (R ²) in the range of 4–200?mg/L were 0.9975 and 0.9783 when a glucose/glutamate BOD standard was applied. The relative error of standard deviations for the two microorganism-immobilized BOD sensing films were within 4%?and 2%?of the mean value, respectively. The effects of temperature, pH and sodium chloride concentration on the two microbial films were also studied. For low biochemical oxygen demand, a film of sieved bacteria from seawater had superior sensitivity and is expected to be developed further.     

Investigation of metal activation of a partially purified polyphenol oxidase enzyme electrode

Biosensors can be developed using different biological materials and immobilization technologies. Enzymes are generally used in biosensor construction, and some enzymes need metal ions or small organic molecules as a cofactor for their activation. Polyphenol oxidases can be activated by several metal ions such as Cu²⁺, Mg²⁺, Zn²⁺, Mn²⁺, and Ni²⁺. In this study, a new measurement method has been developed that is based on the metal ion activation of the polyphenol oxidase enzyme used in the biosensor preparation, especially to determine the concentration of Mg²⁺ ions. Polyphenol oxidase (PPO) (EC 1.10.3.1) was partially purified from potato (Solanum tuberosum) by using (NH₄)₂SO₄ precipitation, dialysis, and lyophylization processes. As a result of this processes, approximately 30-fold purification was achieved for PPO. For construction of the biosensor, the enzyme was immobilized on the dissolved oxygen probe membrane using gelatin and glutaraldehyde (2.5%). Using the biosensor, we obtained responses for catechol in the absence and presence of Mg²⁺ ions. Differences between the biosensor responses were related to the concentration of Mg²⁺ ions. The biosensor response depends linearly on concentration of Mg²⁺ ions between 0.05 and 7.5?mM. In the optimization studies, phosphate buffer (pH 7.0, 50?mM) and 35°C were determined to be the optimum conditions. This project will be a novel biosensor study and it might bring a new term, ‘activation based biosensor’ into the biosensor area.