SAW sensor for anti-human-immuno-globulin G molecule detection

We developed SAW sensors to detect human-immuno-globulin G (HigG) molecules by applying a particular antibody thin film on the delay line of transverse SAW devices. The mass loading effect was given by the antibody-antigen bonding of the target molecules on the delay line. The sensor consists of twin SAW delay lines operating at 100 MHz fabricated on 36° rotated Y-cut X-propagation LiTaO₃ piezoelectric single crystals. The sensitive channel of the SAW sensor was coated with a gold film on which an antibody layer was immobilized. Protein A molecules were coupled with the HigG molecules to work as an immobilizer layer to hold the antigens (anti-HigG). For proper immobilization of the detection molecules, bovine serum albumin worked as a blocking layer to prevent the adhesion of any other molecules different from the anti-HigG. The relative change in the frequency of the two oscillators was monitored to measure the anti-HigG concentration in the protein solution. The sensor showed linear response to the mass loading effects of the anti-HigG molecules with a sensitivity up to 10.7 ng/ml/Hz.