Surface acoustic wave immunosensor based on Au-nanoparticles-decorated graphene fluidic channel for CA125 detection

Abstract

A delay line configuration Rayleigh SAW immunosensor with an Au-nanoparticles-decorated graphene (AuNPs-Gr) fluidic channel is proposed for the detection of CA125. The tube composed of Gr sheets is prepared by chemical vapor deposition (CVD) and Au-nanoparticles are decorated on the inner wall of the Gr tube by electrodeposition method. The AuNPs-Gr tube with a volume of 4.8 μL is placed on the bus bar of the SAW device and acts as sensing element as well as a micro-fluidic chamber. To estimate the sensing performances of the immunosensor comprehensively, besides the amplitude-frequency characteristics of the insert loss (S21), the phase-frequency characteristics of S21, the equivalent conductance-frequency and susceptance-frequency characteristics are also analyzed. The deposition time of the Gr tubes, antibody concentration, antibody incubation time, and antigen incubation time are optimized to enhance the response of the SAW biosensor. Although the response sensitivity extracted from the amplitude-frequency curves (8.57 Hz/log(mU/mL)) is a bit lower than that from phase-frequency data (11.88 Hz/log(mU/mL)) and that from susceptance-frequency data (12.14 Hz/log(mU/mL)), a wider linear response range of 0.01–300 mU/mL is obtained from the amplitude-frequency curves and the limit of detection is calculated to be 0.00371 mU/mL. In addition, the proposed AuNPs-Gr fluidic channel SAW immunosensor exhibits good specificity and long-time stability and can be used to detect the CA125 in human serum.