Adjunction of Avidin to a Cysteamine Self-Assembled Monolayer for Impedimetric Immunosensor

Abstract

In this work an impedimetric immunosensor based on affinity immobilization method of a biotin labelled anti-human IgG antibody, used as a model system, was reported. The experimental procedure involves the growth of a self-assembled monolayer of a thiol (cysteamine) carrying terminal amine groups on gold electrodes. Glutarardehyde, a homobifunctional cross-linker, was used as a coupling reagent for the covalent linking of avidin to the amine groups of cysteamine. The attachment of the biotin labeled antibodies (anti-Human IgG) to the subsequent modified gold electrode was achieved by affinity interactions tacking advantage of the strong avidin-biotin bridge. The stepwise assembly process of the electrode was interrogated by means of cyclic voltammetry, electrochemical impedance spectroscopy and contact angle measurements. The response of the antibody modified electrode to their target antigens was investigated in the presence of BSA (bovin serum albumin) in order to alleviate non-specific adsorption problems. A proposed electrical model was used to analyse the experimental data. The resulting immunosensor has a linear dynamic range of 100-900 ng•ml −1 of antigen and a detection limit of 100 ng•ml −1 .

Electrochemical immunosensor for detection of Plasmodium vivax lactate dehydrogenase

“…After SAMs formation, a noticeable decrease in CA values was observed. Similar behavior has been reported by other authors 25 , 26 and can be explained by terminal amino groups in the cysteamine structure attributing greater hydrophilicity to the surface.…”

“…Besides, at pH = 7.40 the amino groups are quasi-neutral, and the cysteamine monolayer exhibits insulating characteristics. 26 Several authors have reported that behavior using SAMs formation methodologies in the development of biosensors. 23 , 26 , 27 …”

“… 26 Several authors have reported that behavior using SAMs formation methodologies in the development of biosensors. 23 , 26 , 27 …”

“…Besides, at pH = 7.40 the amino groups are quasi-neutral, and the cysteamine monolayer exhibits insulating characteristics. (26) Several authors have reported that behavior using SAMs formation methodologies in the development of biosensors. (23,26,27) After immobilisation of Ab-PvLDH was observed a decrease in current values (Ipa = 62.57 µA) compared to the previous modification step due to the large molecular size of these antibodies (~180 kDa), which blocks the transfer of charge.…”

Rational Design of High-Performance Donor–Linker–Acceptor Hybrids Using a Schiff Base for Enabling Photoinduced Electron Transfer

“…The zeta potential of Cys/NAC-AuNCs was determined to be +10 ± 1.3 mV ( n = 3, pH = 5.0). Since the p K a of NAC is as low as 3.24, the positively charged surface should originate from the protonated amino group (−NH 3 + ) of Cys (p K a = 8.27), which reveals the presence of Cys in the capping layer. The presence of Cys in the capping layer can be further confirmed by XPS and FT-IR measurements.…”