Gradients of a Sandwich-structured Immunosensor Controlled Using Magnetized Masks for Determination of Human Serum Albumin Using Electrochemiluminescence

Abstract

Background: Separation of macromolecules or particles from a colloid system to from gradient structure on the surface has been employed for biosensing systems, suggesting an enhancement of the chemical and physical features of particles. Performance of an electrochemiluminescence (ECL) immunosensor was employed to improve with a particle gradient.Results: Magnetic beads with silicon dioxide coating were adopted as nanocarriers for gradient manipulation and immobilized with the primary antibody. Cadmium telluride quantum dots (CdTe QDs) were coated with a layer of protein G for conjugation and orientation of secondary antibody as signal labels. ECL immunosensor gradients upon the electrode were formed by magnetolithography with magnetized nickel masks of column and stripe arrays at various scales. The immunosensor generally aggregated as island on the substrate through a dry process of water evaporation leading to a decrease of efficiency in the characteristic signals. Stripe arrays of magnetized nickel were designed to generate cylindrical magnetic flux on the substrate to improve the particle manipulation with the gradient. Various gradients of the sandwich-structured immunosensor substantially affected the electrochemical performance. Compared to the gradient-free immunosensor, the gradient of the immunosensor generated using the 3-μm-stripe array mask of magnetolithography enhanced the ECL intensity ~2.2 times. Conclusions: The results of quantification of human serum albumin (HSA) with the gradient immunosensor showed a broad linear range (15–420 ng mL−1), a low limit of detection (8 ng mL−1) and high reliability for HSA-spiked serum samples, indicating that the immunosensor gradient substantially enhances the performance of the ECL assay.