Detection of an uncharged steroid with a silicon nanowire field-effect transistor

Ko Shing Chang, Chen Chia Chen, Jeng-Tzong Sheu, Yaw-Kuen Li*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

33 Scopus citations


Among biosensors of various types, the silicon nanowire field-effect transistor (SiNW-FET) is believed to be the most sensitive and powerful device for bio-applications. The principle of sensing is based on the variation of conductivity resulting from a disturbance of charge on the surface of the SiNW-FET, but this detection is feasible predominantly for charged analytes, such as a protein, DNA, antibody, virus etc. The objective of our work was to overcome this intrinsic weakness of a SiNW-FET and to develop a platform to detect steroids. For this purpose, we designed an engineered protein, Δ5-3-ketosteroid isomerase, to function as a steroid acceptor that was chemically modified with a carbon chain-linked 1,5-EDANS moiety, and further immobilized on the surface of a silicon nanowire. In the presence of a steroid, the negatively charged 1,5-EDANS moiety, which presumably occupies the steroid-binding site, is expelled and exposes to the nanowire surface. The electrical response produced from the 1,5-EDANS moiety is measured and the concentration is calculated accordingly. The sensitivity of this novel nano-bio-device can attain a femtomolar level.

Original languageAmerican English
Pages (from-to)148-153
Number of pages6
JournalSensors and Actuators, B: Chemical
Issue number1
StatePublished - 24 Apr 2009


  • Δ-3-Ketosteroid isomerase
  • Biosensor
  • Silicon nanowire field-effect transistor
  • Steroid


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