Immobilization of aptamers onto unmodified glass surfaces for affordable biosensors

Silicon dioxide surfaces are commonly used in photonic microsensors for bioreceptor attachment. Functionalization of sensor surface with aptamer receptors provides the opportunity to develop low cost, robust, field deployable sensors. Most aptamer sensors are constructed by covalently linking modified aptamers to a derivatized surface. There have been reports of using UV crosslinking to directly immobilize DNA with sequences that end with poly(T)10-poly(C)10 on an unmodified glass surface for hybridization. We have expanded this strategy using thrombin-binding aptamers (TBAs) with three different tail modifications. TBA with PolyT20 tail showed the best performance in terms of sensitivity and dynamic range. PolyTC tailed aptamers did not bind thrombin well, which may be due to that the interactions between the C bases and G-quadruplex affect their target binding capability. When compared to biotinylated aptamer immobilized on a streptavidin surface, polyT aptamer printed directly on plain glass showed comparable affinity. Direct immobilization of TBA on nonfunctionalized silicon dioxide wafer and its binding towards thrombin has also been demonstrated. Our results showed that using polyT-tagged aptamer probes directly immobilized on unmodified glass and SiO 2 surface is a robust, very straightforward, and inexpensive method for preparing biosensors.