Abstract
In this study, polyelectrolyte multilayers were fabricated on a polystyrene (PS) plate using a Layer-by-Layer (LbL) self-assembly technique. The resulting functional platform showed improved performance compared with conventional enzyme-linked immunosorbent assay (ELISA) systems. Poly(diallyldimethylammonium chloride) (PDDA) and poly(acrylic acid) (PAA) were used as cationic and anionic polyelectrolytes. On the negatively-charged (PDDA/PAA)3 polyelectrolyte multilayers the hydrophilic PAA surface could efficiently decrease the magnitude of the noise signal, by inhibiting nonspecific adsorption even without blocking reagent adsorption. Moreover, the (PDDA/PAA)3 substrate covalently immobilized the primary antibody, greatly increasing the amount of primary antibody adsorption and enhancing the specific detection signal compared with a conventional PS plate. The calibration curve of the (PDDA/PAA)3 substrate showed a wide linear range, for concentrations from 0.033 to 33 nM, a large specific signal change, and a detection limit of 33 pM, even though the conventional blocking reagent adsorption step was omitted. The (PDDA/PAA)3 substrate provided a high-performance ELISA system with a simple fabrication process and high sensitivity; the system presented here shows potential for a variety of immunosensor applications.
Highlights
The enzyme-linked immunosorbent assay (ELISA) system is extensively applied to perform immunoassays
As a result of these experiments, we considered that Polyelectrolyte multilayers (PEMs) could be used to control the protein adsorption in each step of the ELISA
PEMs can be deposited on a substrate of any morphology using a simple alternating dip-coating process, and PEMs hold significant advantages for the effective control of protein adsorption and cell adhesion [21]
Summary
The enzyme-linked immunosorbent assay (ELISA) system is extensively applied to perform immunoassays. The ELISA system combines specific antibodies with sensitive and simple enzyme assays, by using antibodies or antigens coupled to an -assayed enzyme [1]. The conventional ELISA system on a PS plate suffers from relatively poor sensitivity, a low surface-to-volume ratio, and random orientation of the adsorbed antibody or antigen, which is not optimal for subsequent antibody–antigen recognition and binding [6]. It is, crucial to develop new methods with a higher sensitivity and a lower limit of detection (LOD) for routine diagnosis [7,8]
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