Label-free Detection of Biotin Using Nanoporous TiO2/DNA Thin-film Coated Wavelength Interrogated Surface Plasmon Resonance Sensors

The sensing sensitivity of the wavelength interrogated surface plasmon resonance(WISPR) biosensor could be improved by self-assembly of nanoporous thin-film of TiO₂ nanoparticles/DNA(TiO₂/DNA)_n(n is the number of bilayer) on wavelength interrogated surface plasmon resonance(WISPR) chips. The growth behavior and surface structure of the nanoporous thin-film were investigated by UV-Vis spectroscopy and scanning electron microscopy, respectively. The home-made WISPR sensor with Krestchmann configuration consisted of a tungsten-halogen lamp as a photon source and a CCD camera as the detector. After the deposition of (DNA/TiO₂)_n thin film on WISPR chips, the resonance peak of the reflection spectra appeared in air. With the increases of n, the resonance wavelength gradually red shifted, which is consistent with the simulated results. After the optimization of the porous film, the WISPR biosensor was utilized to detect low-molecular-weight analytes, such as biotin. The result demonstrates that the sensitivity of poly(styrene sulfonate)/polyally lamine hydrochlorides]₅(PSS/PAH)₅ could be 4 times higher than that of polyelectrolyte multilayer modified WISPR sensor.