Immunosensors based on electrical impedance spectroscopy are increasingly being used as a fast, potentially low cost method for clinical diagnostics. In this work we fabricated immunosensors by depositing layer-by-layer (LbL) films made with an antigenic peptide and lignin on interdigitated gold electrodes, which could detect anti-HIV antibodies in PBS solutions.  Adsorption of the peptide and lignin layers was probably driven by H-bonding, but electrostatic interactions between the positive amine groups from the peptide and the lignin groups with residual negative charge could not be excluded, leading to an exponential film growth. The molecular recognition interaction between the peptide and the anti-HIV antibodies yielded substantial changes in morphology, with increased roughness according to atomic force microscopy data. This interaction is behind the high sensitivity of the immunosensor. Indeed, from the electrical impedance spectra, we noted that the capacitance increased significantly with the antibody concentration, before getting close to the saturation of available peptide sites at high concentrations. The estimated sensitivity in the linear range was 7.4 10-3 nF/mmol-1. The selectivity of the immunosensor was confirmed with two types of control experiments. First, no changes in impedance were observed when the lignin/peptide LbL film was immersed into a PBS solution containing the non-specific anti-HCV (for Hepatitis B) antibody. Furthermore, for LbL films made with lignin only, the electrical response was not affected by adding antibodies into the PBS buffer. The successful immunosensing for HIV with antigenic peptides in a lignin matrix is also relevant for valorization of lignin, which is an important biomass component in the sugar and ethanol industry, and brings the prospect for all-organic, biocompatible sensors if implantation is ever required.

HIV-sensing using an antigenic peptide immobilized  in a lignin matrix in layer-by-layer films

247th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.