中央研究院 原子與分子科學研究所

Silicon nanowire field-effect transistors (SiNW-FETs) have recently drawn tremen-dous attention as a promising tool in biosensor design because of their ultrasensitivity,
selectivity, and label-free and real-time detection capabilities. Here, we review the recently published literature that describes the device fabrication and biomedical applications of SiNW-FET sensors. For practical uses, SiNW-FETs can be delicately designed to be a reusable device via a reversible surface functionalizationmethod. In the fields of biological research, SiNW-FETs are employed in the detections of proteins, DNA sequences, small molecules, cancer biomarkers, and viruses. The methods by which the SiNW-FET devices were integrated with these repre-sentative examples and advanced to virus infection diagnosis or early cancer detection will be discussed. In addition, the utilization of SiNW-FETs in recording the physiological responses from cells or tissues will also be reviewed. Finally, the novel design of a three dimensional (3D) nano-FET probe with kinked SiNWs for recording intracellular signals will be highlighted in this review.

An essential issue in graphene nanoelectronics is to engineer the carrier type and density and still preserve the unique band structure of graphene. We report the realization of high-quality graphene p-n junctions by noncovalent chemical functionalization. A generic scheme for the graphene p-n junction fabrication is established by combining the resist-free approach and spatially selective chemical modification process. The effectiveness of the chemical functionalization is systematically confirmed by surface topography and potential measurements, spatially resolved Raman spectroscopic imaging, and transport/magnetotransport measurements. The transport characteristics of graphene p-n junctions are presented with observations of high carrier mobilities, Fermi energy difference, and distinct quantum Hall plateaus. The chemical functionalization of graphene p-n junctions demonstrated in this study is believed to be a feasible scheme for modulating the doping level in graphene for future graphene-based nanoelectronics.

In this study, we describe a highly sensitive and reusable silicon nanowire field-effect transistor for the detection of protein-protein interactions. This reusable device was made possible by the reversible association of glutathione S-transferase-tagged calmodulin with a glutathione modified transistor. The calmodulin-modified transistor exhibited selective electrical responses to Ca²⁺ (≥1 μM) and purified cardiac troponin I (∼7 nM); the change in conductivity displayed a linear dependence on the concentration of troponin I in a range from 10 nM to 1 μM. These results are consistent with the previously reported concentration range in which the dissociation constant for the troponin I-calmodulin complex was determined. The minimum concentration of Ca²⁺ required to activate calmodulin was determined to be 1 μM. We have also successfully demonstrated that the N-type Ca²⁺ channels, expressed by cultured 293T cells, can be recognized specifically by the calmodulin-modified nanowire transistor. This sensitive nanowire transistor can serve as a high-throughput biosensor and can also substitute for immunoprecipitation methods used in the identification of interacting proteins.