Brewster angle microscopic study of mixed lipid–protein monolayer at the air–water interface and its application in biosensing

This study investigated lipid–protein LB film formation with Brewster angle microscopy. Our experimental results show that hemoglobin (Hb) molecules can enter the lipid layer and remain for an extended time. We investigated the KCl effect on the LB monolayer of lipid–protein. The lipid–Hb monolayer was transferred from the air–water interface to a QCM gold electrode. UV–vis spectra showed that Hb retained its natural structure in the lipid layer. Cyclic voltammetric (CV) and amperometric systems were applied in this study in order to confirm the remaining bioactivity and sensitivity of Hb to hydrogen peroxide (H2O2). Lipid–Hb-modified electrodes showed well-defined redox peaks, indicating that the direct electron transfer between Hb and the electrode was enhanced by Hb incorporated in lipid layer. Based on this phenomenon, a novel biosensor for H2O2 was designed. Experimental conditions influencing the biosensor performance such as pH, and potential were optimized and assessed. The levels of the R.S.D.'s (<5%) for the entire analyses reflected the highly reproducible sensor performance. Using optimized conditions the linear range for the detection of H2O2 was observed from 1 × 10−6 to 1.00 × 10−4 mol L−1 with a detection limit of 4.00 × 10−7 mol L−1 (based on the S/N = 3).