Dual-grating waveguide coupler biosensor for the real-time determination of human immunoglobulin M (IgM) antibodies

Abstract

A dual-grating waveguide coupler biosensor was developed to detect human immunoglobulin M (IgM) antibodies with modification procedures using (3-aminopropyl)triethoxysilane (APTES) as the self-assembled monolayer were optimized. The average bulk sensitivity and optimal resolution were 43.84 ± 1.15 RIU−1 and 6.18 × 10−6 RIU, respectively. Due to the photocatalytic property of TiO2, ultraviolet treatment for 7.5 min was used to form the hydroxyl groups on TiO2 surface. APTES immobilized the biomolecules via chemical bonding; the optimal APTES modified parameters were 2% (v/v) for 0.5 h at 80 °C. Glutaraldehyde (GA) immobilized the protein A without activating carboxyl groups of protein A. The optimal GA modified conditions were 2.5% (v/v) for 48 min. Protein A immobilized the capture antibody directionally, the fragment antigen binding (Fab) region of the capture antibody was more completely exposed to improve the detection effect. Using the optimal modification conditions, the limit of detection for human IgM immunoassay was 2.67 × 10−8 ± 1.18 × 10−8 g/mL. Furthermore, this biosensor was demonstrated to determine the concentration of human IgM within 1 h and has potential for commercialization.