Electrochemical Development of an Immunosensor for Detection Polychlorinated biphenyls (PCBs) for Environmental Analysis

Polychlorinated biphenyls (PCBs) are a highly toxic family of synthetic chemical compounds. PCBs are widely spread in the environment and their toxicity can cause serious ailments to living organisms such as cancer; therefore, developing a device for the detection of PCBs in the environment is significant. In this paper, polyclonal primary anti-PCB antibodies were immobilized onto a gold screen-printed electrode with the purpose of creating an electrochemical immunosensor for the detection of Aroclor 1254. It was modified with 11-mercaptoundecanoic acid (11-MUA) and the activation of the carboxylic acid terminal was performed by cross-linking 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hyrodsuccinmide (NHS) on the electrode surface. Cyclic voltammetry, electrochemical impedance spectroscopy (EIS), linear sweep voltammetry, atomic force microscopy (AFM), scanning electron microscopy (SEM), and contact angle measurement were employed to characterize SAM development on the gold electrode. Using a competitive assay, a 0.09 ng/mL−1 limit of detection and a linear range of 0.101–220 ng/mL−1 were determined. The self-assembled monolayers (SAM) were successful in encapsulating the PCBs on the immunosensor. The electrochemical detection showed better resolution when compared to traditional methods such as the ELISA optical technique. The novel electrochemical immunosensor approach that is discussed in this paper has the potential to offer rapid sample screening in a portable, disposable format and could contribute to the effective control and prevention of PCBs in the environment.

Electrochemical Detection and Capillary Electrophoresis: Comparative Studies for Alkaline Phosphatase (ALP) Release from Living Cells

Alkaline phosphatase (ALP) is one of the main biomarkers that is clinically detected in bone and liver disorders using optical assays. The electrochemical principle is important because point-of-care testing is increasing dramatically and absorbance techniques hardly compete with the medical revolution that is occurring. The detection of ALP using electrochemical detection is contributing to the integration systems field, and hence enhancing the detection of biological targets for pharmaceutical research and design systems. Moreover, in vitro electrochemical measurements use cost effective materials and simple techniques. Graphite screen-printed electrodes and linear sweep voltammetry were used to optimize the electrochemistry of the enzymatic product p-aminophenol using the enzyme kinetic assay. ALP release from embryonic and cancer cells was determined from adhesion cell culture. Additionally, capillary electrophoresis and colorimetric methods were applied for comparison assays. The resulting assays showed a dynamic range of ALP ranging from 1.5 to 1500 U/L, and limit of detection of 0.043 U/L. This was achieved by using 70 μL of the sample and an incubation time of 10 min at an optimal substrate concentration of 9.6 mM of p-aminophenol phosphate. A significant difference (p < 0.05) was measured between the absorbance assays. This paper demonstrates the advantages of the electrochemical assay for ALP release from cells, which is in line with recent trends in gene expression systems using microelectrode array technologies and devices for monitoring electrophysiological activity.

Development of acid phosphatase based amperometric biosensors for the inhibitive determination of As(V)

An enzymatic amperometric procedure for the direct measurement of As(V) in the presence of As(III) was developed. The method is based on the inhibitive action of this species on acid phosphatase enzyme (AcP) activity. Screen-printed carbon electrodes (SPCEs) were used as support for the cross-linking immobilization of the enzyme AcP. 2-Phospho-l-ascorbic acid was used as a novel substrate, in arsenic determination, which amperometric response decreased by the presence of As(V) ions. The optimum working conditions were found using experimental design methodology. Under these conditions, repeatability and reproducibility of the constructed biosensors were determined, reaching values below 8% in terms of residual standard deviation. The capability of detection obtained for As(V) was 0.11 μM for AcP/SPCE biosensors. Analysis of the possible effect of the presence of foreign ions in the solution was performed. The method was successfully applied to the determination of the As(V) content in a ground water sample.

Towards the protein phosphatase-based biosensor for microcystin detection

A colorimetric test for the detection of microcystins based on immobilised protein phosphatase (PP) has been developed. A PP2A produced by molecular engineering has been used and its performance has been compared to those of commercial PP2A and PP1. Covalent immobilisation of the enzyme using glutaraldehyde, encapsulation by sol-gel and entrapment with photocrosslinkable poly(vinyl alcohol) bearing styrylpyridinium groups (PVA-SbQ) have been compared, the latter method providing the highest immobilisation yields. Screen-printed carbon electrodes (SPEs), Maxisorp microtiter wells and Ultrabind modified polyethersulfone affinity membranes have been used as immobilisation supports. Whilst the highest immobilisation yields were obtained with microtiter wells, the highest operational and storage stabilities were achieved with carbon SPEs and membranes, respectively. The immobilisation of PP by PVA-SbQ provided a means to preserve the enzymatic activity, which decreased at fast rates when the enzyme was kept in solution. The colorimetric test using p-nitrophenyl phosphate has demonstrated that the immobilised enzyme is able to recognise both microcystin variants (MC-LR and MC-RR), although optimisation work should be performed to achieve appropriate limits of detection. With the purpose to develop an electrochemical biosensor, several phosphorylated substrates have been used. Promising results have been achieved with the commercial enzymes and alpha-naphtyl phosphate, p-aminophenol phosphate and catechol monophosphate as enzyme substrates, guaranteeing the viability of the electrochemical approach.