Rational enhancement of nanobiotechnological device functions illustrated by partial optimization of a protein-sensing field effect transistor

Semiconductor field effect transistors(FETs) are widely used as biosensors, although a potentially powerful application of FET sensing technology (planar immunoFETs sensing proteins at physiological salt concentrations) has long been argued to be intrinsically infeasible. The infeasibility assessment has come under increasing scrutiny of late, and has been found to be lacking on conceptual and empirical grounds. This paper summarizes some, but, by no means all, of the strategies that have been pursued to render the use of immunoFETs, and analogous FET sensors that detect the electrical fields of proteins bound to affinity elements on FET sensing channels (protein-sensing bioFETs), practical in high-salt biological buffers. This paper provides original characterization of oxidized AlGaN surfaces and interfacial polymer/protein films of protein-sensing AlGaN/GaN HFETs. It shows those films to influence significantly FET sensitivity/signal accumulation. The data indicate that re-assessment of the classical assertion of immunoFET infeasibility is long overdue. Beyond substantiating the feasibility of immunoFET operation under solution conditions as found in vivo, data presented here also suggest that transition away from costly AlGaN/GaN HFETs to inexpensive silicon-based immunoMOSFETs may be possible. If so, immunoFETs, dismissed as infeasible 20 years ago, may yet become powerful clinical tools.