Direct Electrochemical Nano‐immunosensor for Microcystin‐LR in Seawater

Abstract

Microcystins are potent hepatotoxins produced by cyanobacteria, which proliferate in wastewaters with high nutrient content. Due to their high toxicity and potential risk to human health, even at low concentrations, the development of a sensitive and rapid method for the monitoring of microcystin‐LR (MC‐LR) in water samples is of great importance. In this context, a new direct electrochemical nano‐immunosensor for MC‐LR detection using the liquid crystal (E)‐1‐decyl‐4‐[(4‐decyloxyphenyl)diazenyl]pyridinium bromide (Br‐Py) as a redox probe and gold nanoparticles stabilized in bovine serum albumin (AuNP‐BSA) is described herein. The microcystin‐LR antibody (anti‐MC‐LR) was covalently immobilized using N‐(3‐dimethylaminopropyl)‐N‐ethylcarbodiimide hydrochloride (EDC) and N‐hydroxysuccinimide (NHS) on an AuNP‐BSA/BrPy film. The proposed sensor response is based on the inhibition of the Br‐Py electrochemical signal after the specific interaction of MC‐LR with immobilized anti‐MC‐LR on the electrode surface. The electrochemical behavior of the immunosensor was studied by square‐wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS). Under optimized conditions, using SWV and an incubation time of 15 min, the immunosensor exhibits a linear response to MC‐LR concentrations of 0.05 to 500.0 ng mL−1 with a detection limit of 0.05 ng mL−1. The anti‐MC‐LR/AuNP‐BSA/Br‐Py/GCE was successfully applied in the determination of MC‐LR in spiked seawater samples.

Label‐free Immunosensor for the Determination of Microcystin‐LR in Water

“…The limit of detection (LOD), calculated as three times the standard deviation of the intercept/slope, was 0.053 ng mL À 1 . Table 1 shows a brief comparison of the linear ranges and detection limits of the GCE/MGNnP-PEI-anti-MC-LR and other immunosensors for MC-LR detection, recently published in the literature [12,14,[16][17][18][32][33][34][35]. It can be observed that the LOD of the proposed immunosensor is close to that of previously reported LOD values.…”

“…It was also found that the highest current suppression was obtained with an incubation time of 40 min, and thus this was considered the ideal time to incubate the MC‐LR antigen. In previous studies on electrochemical immunosensors used to detect MC‐LR, incubation times ranging from 10 to 240 min have been applied . The incubation time selected for the proposed immunosensor is therefore compatible with those cited in the literature.…”

“…Table shows a brief comparison of the linear ranges and detection limits of the GCE/MGNnP‐PEI‐anti‐MC‐LR and other immunosensors for MC‐LR detection, recently published in the literature . It can be observed that the LOD of the proposed immunosensor is close to that of previously reported LOD values.…”

“…Thin-layer chromatography, high-performance liquid chromatography, enzyme-linked immunosorbent assay, liquid chromatography/mass spectrometry and protein phosphatase inhibition assays are the techniques generally applied to detect low concentrations of MC-LR [12,13]. Recently, electrochemical immunosensors and label-free fluorescent probes for MC-LR detection have been developed as an alternative to traditional techniques, offering low detection limits, no need for sample pretreatment and easy manipulation [14][15][16][17][18][19][20].…”