Screening and determinations of tissue polypeptide antigen by label-free optical immunosensing method

Based on the specificity of the immunoreaction of anti-body and antigen, and the resulting localized surface plasmon resonance extinction response of functionalized nano-Au monolayer on glass chip, a novel label-free optical immunosensor with amplified sensitivity has been developed for the detection of tissue polypeptide antigen (TPA). The nano-Au monolayer on glass chip was controllably prepared using 3-mercaptopropyltrimethoxysilane (MPTMOS) as linker by a solution self-assembly method. To analyze its quality, the nano-Au monolayer was characterized by UV-visible spectrum and atomic force microscopy (AFM). The resulting chip was modified by tissue polypeptide antigen antibody (anti-TPA), and then bovine serum albumin (BSA) was employed to block the possible remaining active sites of the nano-Au monolayer. An immunosensor was constructed with biocompatible monolayer nano-Au membrane and the desirable TPA antibody/BSA composite membrane, and it showed good selectivity, high sensitivity and a wide linear response to TPA in the range of 1-1000 ng L(-1) with a detection limit of 1.2 x 10(-3) ng L(-1), as well as good stability and long-term life. Owing to its ease of operation, low detection limit and low cost, it is expected that the proposed procedure may hold great promise in both research-based and clinical assays.