Detection of thrombin-specific oligonucleotides using quartz crystal microbalances coated with silica sol–gel glass thin films

A silica sol–gel glass containing thrombin was spin-coated on a quartz crystal and used to measure the binding of thrombin with thrombin-specific aptamers. The porous structures of the silica thin films were optimized to facilitate binding of the aptamers with thrombin by varying the solution pH and the concentration of polyethylene glycol. The hydrophilic silica sol–gel glass prevented aptamers from adsorbing nonspecifically and the absence of covalent bonding allowed the entrapped thrombin molecules to retain their reactivity. Further, the mass sensitivity of the quartz crystal microbalance was enhanced by encapsulating more thrombin molecules inside the porous sol–gel glasses.