Novel immunoassay for carcinoembryonic antigen based on protein A-conjugated immunosensor chip by surface plasmon resonance and cyclic voltammetry.

In this study, an immunosensor chip utilizing surface plasmon resonance (SPR) and cyclic voltammetry (CV) was fabricated for detecting carcinoembryonic antigen (CEA). Specifically, we applied in parallel an SPR instrument and a CV device to monitor the assembly of carcinoembryonic antibody (anti-CEA) on a protein A-conjugated surface and the subsequent ligand reaction. The immunosensor chips were constructed by various concentrations of protein A. To determine the surface characteristics of different self-assembly monolayers (SAMs), several quantitative and kinetic measurements were carried out. The extent of immobilization of anti-CEA and the immune response of anti-CEA antibody against CEA were measured using the SPR instrument and CV device. The terminal functional groups of protein A have different effects on the adsorption and covalent binding of immunoprotein depending on the steric hindrance. Through the parallel measurements, we demonstrate that SPR and CV are sensitive to measure the antigen-antibody binding capacity.

Electrochemical characteristics of a platinum electrode modified with a matrix of polyvinyl butyral and colloidal Ag containing immobilized horseradish peroxidase.

A new hydrogen peroxide biosensor was constructed, which consisted of a platinum electrode modified by a matrix of polyvinyl butyral (PVB) and nanometer-sized Ag colloid containing immobilized horseradish peroxidase (HRP), and using Co(bpy)3(3+) as mediator in the hydrogen peroxide solution. The electrochemical characteristics of the biosensor were studied by cyclic voltammetry and chronoamperometry. The modified process was characterized by electrochemical impedance spectroscopy and cyclic voltammetry. The HRP immobilized on colloidal Ag was stable and retained its biological activity. The sensor displays excellent electrocatalytic response to the reduction of H2O2. Analytical parameters such as pH and temperature were also studied. Linear calibration for H2O2 was obtained in the range of 1x10(-5) to 1x10(-2) M under optimized conditions. The sensor was highly sensitive to H2O2, with a detection limit of 2x10(-6) M, and the sensor achieved 95% of steady-state current within 10 s. The sensor exhibited high sensitivity, selectivity and stability.

Construction of a novel immunoassay for the relationship between anxiety and the development of a primary immune response to adrenal cortical hormone.

A novel potentiometric immunosensor for the detection of adrenal cortical hormones (ACH) has been developed by means of self-assembling immobilization of adrenal cortical hormone antibody (anti-ACH) on a gold electrode-modified gold nanoparticle (Au) and a thiol-containing sol-gel network. A cleaned gold electrode was first immersed in a (3-mercaptopropyl)-trimethoxysilane (MPS) sol-gel solution to assemble a silica sol-gel monolayer, then the silane units were polymerized into a 2D sol-gel network (2D network) by dipping into aqueous NaOH. The second silane layer was formed by immersion back into the MPS solution overnight, and then the gold nanoparticles (nanogold) were chemisorbed onto the thiol groups of the second silane layer. Finally, anti-ACH was adsorbed onto the surface of the gold nanoparticles. The modified process was characterized by electrochemical impedance spectroscopy (EIS). The detection is based on the change in the potentiometric response before and after the antigen-antibody reaction. Using nanogold and 3-MPS as substrates, potentiometric detection at room temperature resulted in a pseudolinear detection range of about 22-1,000 ng mL(-1) with a detection limit of 5.2 ng mL(-1). Subsequently, several serum samples obtained from medical students with different anxiety extents were analyzed comparing with the ELISA method, and the results demonstrated that the immunoassay meets the demands of psychological analyses.