Protein imprinted TiO2-coated quantum dots for fluorescent protein sensing prepared by liquid phase deposition

Protein-imprinted TiO2 layers were prepared on carboxylated quantum dots (QDots) by liquid phase deposition (LPD) using ribonuclease A (RNase) as a template protein that was non-covalently or covalently immobilized on the QDots during the molecular imprinting process. Fluorescence spectra of the RNase-imprinted TiO2/QDots nanoparticles at pH 7.0 were measured with various concentrations of RNase, and fluorescence intensity at 530 nm (ex: 350 nm) was found to decrease with increasing the concentration of RNase added. The degree of quenching depended on proteins, and RNase showed the strongest quenching compared to other tested proteins including insulin, lysozyme, cytochrome c, albumin, and IgG. In contrast, the fluorescence change of the non-imprinted TiO2/QDots was only little. These results suggest that the RNase binding cavities are constructed by the proposed LPD-based molecular imprinting process, and the readout of specific RNase binding events can be achieved by measuring the fluorescence change.