Simultaneous electrochemical immunosensing of alpha-fetoprotein and prostate specific antigen using a glassy carbon electrode modified with gold nanoparticle-coated silica nanospheres and decorated with Azure A or ferrocenecarboxylic acid

Abstract

We describe an electrochemical immunosensor for the simultaneous determination of alpha-fetoprotein (AFP) and prostate specific antigen (PSA) via a modified glassy carbon electrode. Silica nanoparticles (200-300 nm i.d.) with good monodispersity and uniform shape were synthesized, and the following species were then consecutively immobilized on their surface: gold nanoparticles (AuNPs; 5-15 nm i.d.), secondary antibody (Ab 2 ) and the redox-probes Azure A or ferrocenecarboxy acid (Fc). In parallel, two types of primary antibodies (Ab 1 ) were co-immobilized on the surface of the dissolved reduced graphene oxide sheets (rGO) that were also decorated with AuNPs. In the presence of antigens (AFP or PSA), the Ab 2 /Si@AuNPs carrying Azure A and Fc are attached to the AuNP/rGO conjugate via a sandwich type immunoreaction. Differential pulse voltammetry (DPV) was employed to measure the resulting changes in the signal of Fc or Azure A. Two well-resolved oxidation peaks, one at −0.48 V (corresponding to Azure A) and other at+0.12 V (corresponding to Fc; both vs. SCE) can be observed in the DPV curves. Under optimal conditions, AFP and PSA can be simultaneously determined in the range from 0.01 to 25 ng mL‾ 1 for AFP, and from 0.012 to 25 ng mL‾ 1 for PSA. The detection limits are 3.3 pg mL‾ 1 for AFP and 4.0 pg mL‾ 1 for PSA (at a signal-to-noise ratio of 3). The method was applied to (spiked) real sample analysis, and the recoveries are within 96.0 and 107.2 % for PSA, and within 100.9 and 105.8 % for AFP, indicating that this dual immunosensor matches the requirements of clinical analysis.

Ultrasensitive Multiplexed Immunoassay for Tumor Biomarkers Based on DNA Hybridization Chain Reaction Amplifying Signal

“…For AFP, the linear regression equation was I (μA) = 2.53 + 0.714 C (ng mL –1 ) ( R = 0.9933). Compared with other multiplexed electrochemical immunoassay, , the immunoassay exhibited a wider linear range and lower detection limit.…”

“…Protein activity and electrochemical signal of signal molecules are related to pH, from Figure A, it could be observed that pH 7.0 PBS was suitable. Incubation time between Ab 1 and Ag was selected 45 min according to our previous work and literature . The incubation time between Ag and Ab 2 -S conjugates was investigated.…”

Fluorescence and Scattering Light Cross Correlation Spectroscopy and Its Applications in Homogeneous Immunoassay

“…The composition of serum samples is complex, and its autofluorescence will interfere with immunoassay. The dilution is a very commonly used strategy to reduce the interference of the serum autofluorescence. − In this assay, serum samples are 200 times diluted with PBS. Recovery results of homogeneous sandwich immunoassay by FSCCS are over 90%, as shown in Table S2.…”

Nanomaterial-based biosensors for detection of prostate specific antigen

“…Initial efforts in construction of electrochemical PSA biosensors offered LOD, which are typical for ELISA using either antibodies or aptamers. Antibodies were immobilized on a nanoporous gold surface coated by self-assembled monolayer (SAM) [26], a nanocomposite containing gold nanoparticles (AuNPs) and functionalized multi-walled carbon nanotubes (MWCNTs) [27, 28], AuNPs for a real-time electrochemical profiling on a lab-on-chip device [29], reduced graphene oxide (rGO) modified by silk peptide [30], AuNPs deposited on silica nanospheres together with a redox dye [31] and on an ordered and hierarchically organized interfacial supramolecular architecture [32]. Aptamers were immobilized on a nanocomposite consisting of AuNPs and mesoporous carbon [33].…”