Preparation of silicon nitride biochips for reflectometric interference spectroscopic (RIfS) analysis of biological toxins and E. coli O157:H7 strain

Abstract The surface of a commercially available silicon nitride (SiN) substrate was modified with gold (Au) nanoparticle and then with either lactosyl derivative or monoclonal antibody. Each of the derived SiN chips carrying Au-lactose or Au-antibody was evaluated in the reflectometric interference spectroscopic (RIfS) analyses of Ricinus communis lectin (RCA 120 ) and toxin (RCA 60 ). The RIfS analysis using the Au-lactose/SiN chip enabled us to detect the plant lectin at concentrations less than 5–10 ng/mL as well as the toxin (ricin) sealed carefully in a test sample at concentration about 1 μg/mL. The RIfS analysis using the Au-antibody/SiN chip was useful for the facile and direct screening of enterohemorrhagic Escherichia coli (EHEC) O157:H7 strain in the presence of possible interfering materials. The overall detection was completed within 2.5 h-cultivation time without any purification process for the pathogenic bacterium.