Preparation of titania sol–gel matrix for the immunoassay by SPR biosensor with magnetic beads

The immunoassay of heat shock protein 70 (Hsp 70) by surface plasmon resonance (SPR) biosensor with magnetic beads immobilized on the Au film was performed. A facile vapor deposition method has been developed for the preparation of sol–gel matrix on the Au film, which could protect the Au film from the deposition of magnetic beads on it. The sol–gel-derived titania-modified Au film retained the bioactivity and provided for long-term stability of the biomaterials in storage. The vapor deposition method simplified the traditional sol–gel process and prevented the cracking of conventional sol–gel-derived glasses. In the presence of titania sol–gel matrix as the safeguard, the SPR biosensor with magnetic beads exhibited a satisfactory response concentration range of Hsp 70 from 0.20 to 30.00 μg ml−1. Compared to the measurement without modification of titania sol–gel matrix, larger resonant wavelength shift and sensitivity enhancement of the biosensor were obtained simultaneously. Effects of the vapor deposition time and operating potential for obtaining the titania sol–gel matrix were explored for optimum analytical performance and the stability of the biosensor was also evaluated.