(291f) Anodic Stripping Voltammetry Detection of Conjugated Silver Nanoparticles As Electrochemical Probes

Microbial pathogens in water pose a significant health risk. There is a need for rapid, cost-effective detection of toxins in water. Polymerase chain reaction (PCR) and enzyme immunoassay techniques are the gold standard for pathogen detection. However, these methods require several complicated processing steps and expensive instrumentation, which makes them unsuitable for use in point-of-use systems. By comparison, electrochemical biosensors are a practical solution because they can quickly, inexpensively, and sensitively detect pathogens. Silver nanoparticles (AgNPs) have been used for electrochemically detecting DNA, protein, and viruses as an alternative for enzyme immunoassay and in situ PCR. Anodic stripping voltammetry (ASV) is an electroanalytical method that uses a potential sweeping technique by stripping the electrode of the deposited metal ions present in solution at concentrations below parts per billion (ppb). Analytical responses from ASV are obtained in seconds, and the technique can be deployed in the field by eliminating the need for bulky instrumentation and elaborate sample preparation. This study will focus on a novel electrochemical biosensing method that utilizes AgNPs as electrochemical tags and readily available platinum (Pt) electrodes for detecting antibody-conjugated AgNPs for pathogen detection.

Methods and Results

A three-electrode system consisting of a platinum (Pt) working electrode, a Pt counter electrode, and an Ag/AgCl reference electrode was used for detection. Dissolved AgNPs were first deposited on the working electrode and stripped by a linear sweep voltammetry scan. Similarly, AgNPs coated with human IgG antibodies (HIgG) were stripped to determine the stripping peak of AgNPs-conjugated antibodies. Based on the experimental results, the stripping peak potential of HIgG-coated AgNPs is between 0.19 V and 0.22 V, whereas the stripping potential of AgNPs is ~ 0.14 V. Both these peaks correspond to the stripping peak observed for Ag(I) metal (0.12-0.2 V). This suggests that AgNPs' electrochemical peak would appear at a voltage similar to Ag metal and supports the use of AgNPs as electrochemical probes for use in a biosensor. The experiments were then reproduced for different antibody-AgNPs solution concentrations to validate the response's linearity over the AgNPs concentration range (0.1-10 ng/ml).

Significance

To our knowledge, no directly comparable electrochemical detection of AgNPs as probes using unmodified Pt electrodes for ASV was found in the literature. The results from this study will lay the groundwork for detecting toxin antibodies in water. The results obtained in this study have bridged the gap between ASV's use as an alternative analytical method for detecting biological components and its application as a low-cost sensing platform that can be applied in areas that otherwise require tedious sample preparation and detection approaches. We demonstrate the novel use of ASV for biosensing and establish an analytical approach that uses electrode materials that are commercially available and easily scalable for multiplexed analysis.