Using silver nanoparticle and thiol graphene quantum dots nanocomposite as a substratum to load antibody for detection of hepatitis C virus core antigen: Electrochemical oxidation of riboflavin was used as redox probe.

In this study a facile green approach to employ silver nanoparticle (AgNPs) and thiol graphene quantum dots (GQD-SH) as the nanomaterial for ultrasensitive and selective detection of hepatitis C virus core antigen (HCV) have been investigated. AgNPs/GQD-SH was utilized as a substratum to load antibody for detection of hepatitis C virus core antigen. AgNPs have been immobilized on SH groups of GQDs via bonding formation of Ag-S and anti-HCV have been loaded on the electrode surface via the interaction between -NH2 group of antibody and AgNPs. Using the proposed nanocomposite provides a specific platform with increased surface which is capable of loading more antibodies to entrap the antigen. The decreasing of the electrochemical signal can be achieved after the specific recognition between antibodies and antigens. Riboflavin was used as a biological molecule with inherent properties, for the first time, as the redox probe in the development of HCV core antigen electrochemical immunosensor. Compared to the other redox probes, riboflavin is superior in its oxidization in negative potential range, where the number of interfering species for riboflavin is much fewer. The proposed immunosensor showed wide linear range from 0.05pgmL-1 to 60ngmL-1 with limit of detection of 3fgmL-1. This novel immunosensor was used to analyze the serum sample. The immunosensor provides a convenient, low-cost and simple method for HCV core antigen detection and proposes new horizons for quantitative detection of antigen in the clinical diagnosis.

Layer-by-layer assembly of gold nanoparticles and cysteamine on gold electrode for immunosensing of human chorionic gonadotropin at picogram levels.

The development of an electrochemical immunosensor for the detection of human chorionic gonadotropin (hCG) is described with a limit of detection as low as 0.3 pg mL(-1) in phosphate buffer. In this immunosensor, cysteamine (Cys) and gold nanoparticles (AuNPs) were used to immobilize an anti-hCG monoclonal antibody onto a gold electrode (GE). The structure of AuNPs has been confirmed by EDS, SEM, and TEM analysis. Due to the large specific surface area and excellent electrical conductivity of AuNPs, electron transfer was promoted and the amount of hCG antibody was enhanced significantly. A systematic study on the effects of experimental parameters such as pH, incubation time in the hCG solution and urea solution used for experiments on the binding between the immobilized antibody and hCG has been carried out. Under optimal experimental parameters, differential pulse voltammetry (DPV) signal changes of the [Fe(CN)6](3-/4-) are used to detect hCG with two broad linear ranges: 0.001 to 0.2 and 0.2 to 60.7 ng mL(-1). The LOD value proves more sensitive in comparison with previously reported methods. The prepared immunosensor showed high sensitivity and stability. In addition, the immunosensor was successfully used for the determination of hCG in human serum.

Determination of buprenorphine by differential pulse voltammetry on carbon paste electrode using SDS as an enhancement factor.

In the present study, a facile electrochemical approach is proposed for the determination of buprenorphine (BPR) in the presence of sodium dodecyl sulfate (SDS). SDS was applied for amplification of oxidation signal. Carbon paste electrode (CPE) used as working electrode and cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) were carried out in phosphate buffer solution (pH3.0). Under optimal experimental conditions, the oxidation current increased with the addition of BPR in the sample and two dynamic ranges obtained from 4.00 nM to 0.126 µM and from 0.126 to 0.317 µM by DPV and exhibited a low detection limit (LOD) of 1.33 nM (S/N=3). This offered method has been used for the determination of BPR in the real samples and has validated with the recovery test for BPR spiked urine samples. The result demonstrated that this method is a simple, sensitive, rapid, low-cost, and stable method for BPR detection.