Exploring the Potential of Polyelectrolyte-Aptamer Films For Use in Optical and Electrochemical Sensing

Polyelectrolyte-aptamer films have emerged as versatile and easy-to-fabricate materials for applications ranging from cargo delivery to sensing. The films comprising charged polymers and DNA aptamers exhibit changes in the permeability upon binding of the target. Herein we explore the target-controlled diffusion of ions in these films as the basis for generating sensing signals. First, we demonstrate a colorimetric sensing platform, where the polyelectrolyte-aptamer film is assembled on top of plasmonic nanoparticles. The colorimetric response arises from morphological changes of nanoparticles induced by an oxidizing etching agent, whose rate of diffusion is controlled by the polyelectrolyte-aptamer film. Second, we show the versatility of these films for electrochemical sensing by assembling polyelectrolyte-aptamer films on Indium Tin Oxide electrodes. Cyclic voltammetry was employed to monitor the diffusion-controlled electrochemical activity of a redox couple that generates the signal. We examine the concentration dependence and ionic interference effects of these two platforms, and investigate the film composition and aptamer requirements for achieving the sensing functionality. In summary, this project provides fundamental insight on a facile and low cost methodology in optical and electrochemical sensing that may be readily adapted to different analytes. Further development of these films and sensing platforms may allow portable field analysis by using consumer electronics. Our work presents new opportunities in aptamer-based sensing.