Improved antibody loading on self-assembled graphene oxide films for using in surface plasmon resonance immunosensors

Abstract Immunoassays are important for the diagnosis of many diseases. Efficient methods for the immobilization of the biorecognition elements is a relevant subject because the antibody loading is directly related to the detection range and sensitivity. Here different self-assembled films were explored to take advantage of polar oxygenated groups from graphene oxide (GO) structure. Surface plasmon resonance (SPR) sensors were modified with different GO self-assembled films and compared to the well-established thiol-functionalization with 11-MUA (11- mercaptoundecanoic acid). Self-assembled cysteamine/GO functionalized sensor (Cys-GOSA) provided the highest protein loading (7.66 × 10−12 mol cm−2 against 1.29 × 10−11 mol cm−2 for the traditional thiol-functionalization). The Langmuir-Blodgett (LB) films of GO were composed of aggregates and empty spaces, which hindered the antibody anchoring (around 6.38 × 10−12 to 3.45 × 10−12 mol cm−2). The SPR response of the Cys-GOSA-modified sensor to the 4.0 ng mL−1 PSA was 125% higher than the thiol-functionalized sensor at the same concentration. This result indicates a simple and promising surface modification strategy for many important applications, not limited to SPR sensors, but for all immunoreaction-based assays as enzyme-linked immunosorbent assay (ELISA), electrochemical (e.g. amperometric and impedimetric) and quartz crystal microbalance (QCM) based sensors.