Visual/quantitative SERS biosensing chip based on Au-decorated polystyrene sphere microcavity arrays

A microfluidic chip was designed and fabricated to achieve visual and quantitative sensing for the biomarker of Epstein-barr virus antibody (EBV IgG) based on TMB chromogenic unit and Raman detection unit. The biosensor was composed of polystyrene/Au nanoparticles (PS/AuNPs) microsphere arrays on a quartz substrate, where the initial SERS signal was amplified ten times than pure AuNPs through synergetic coupling between the optical field of PS whispering gallery microcavity and plasmon of AuNPs. Meanwhile, we introduced a signal probe by assembling horseradish peroxidase with high catalytic activity to TMB and Raman reporter rhodamine 6 G, in which TMB turned from colorless to blue and gradually deepened with increasing amount of EBV IgG being captured while the unique fingerprint information of rhodamine 6 G provided the accurate Raman signal for point-of-care testing of target. In sum, an integrated microchip that allows visual prediction under the assistance of TMB color as well as SERS responses with a wide dynamic linear range of 10−1∼105 pg·mL−1 and detection limit as low as 0.045 pg·mL−1 were obtained simultaneously, this lab-on-a-chip design offers a powerful model system for the early diagnosis of various cancer markers in peripheral blood.