Utilizing fab fragment-conjugated surface plasmon resonance-based biosensor for detection of Salmonella Enteritidis

Although antibodies, a key element of biorecognition, are frequently used as biosensor probes, the use of these large molecules can lead to adverse effects. Fab fragments can be reduced to allow proper antigen-binding orientation via thiol groups containing Fab sites that can directly penetrate Au sites chemically. In this study, the ability of the surface plasmon resonance (SPR) sensor to detect Salmonella was studied. Tris(2-carboxyethyl)phosphine was used as a reducing agent to obtain half antibody fragments. Sensor surface was immobilized with antibody, and bacteria suspensions were injected from low to high concentrations. Response units were changed by binding first reduced antibody fragments, then bacteria. The biosensor was able to determine the bacterial concentrations between 10³ and 10⁸ CFU/mL. Based on these results, the half antibody fragmentation method can be generalized for faster, label-free, sensitive, and selective detection of other bacteria species.