The effect of pH and DNA concentration on organic thin-film transistor biosensors

Hadayat Ullah Khan, Mark E. Roberts, Olasupo B. Johnson, Wolfgang Knoll, Zhenan Bao

Research output: Contribution to journalArticlepeer-review

29 Scopus citations


Organic electronics are beginning to attract more interest for biosensor technology as they provide an amenable interface between biology and electronics. Stable biosensor based on electronic detection platform would represent a significant advancement in technology as costs and analysis time would decrease immensely. Organic materials provide a route toward that goal due to their compatibility with electronic applications and biological molecules. In this report, we detail the effects of experimental parameters, such as pH and concentration, toward the selective detection of DNA via surface-bound peptide nucleic acid (PNA) sequences on organic transistor biosensors. The OTFT biosensors are fabricated with thin-films of the organic semiconductor, 5,5′-bis-(7-dodecyl-9H-fluoren-2-yl)-2,2′-bithiophene (DDFTTF), in which they exhibit a stable mobility of 0.2 cm 2 V -1 s -1 in buffer solutions (phosphate-buffer saline, pH 7.4 or sodium acetate, pH 7). Device performance were optimized to minimize the deleterious effects of pH on gate-bias stress such that the sensitivity toward DNA detection can be improved. In titration experiments, the surface-bound PNA probes were saturated with 50 nM of complementary target DNA, which required a 10-fold increase in concentration of single-base mismatched target DNA to achieve a similar surface saturation. The binding constant of DNA on the surface-bound PNA probes was determined from the concentration-dependent response (titration measurements) of our organic transistor biosensors. © 2011 Elsevier B.V. All rights reserved.
Original languageEnglish (US)
Pages (from-to)519-524
Number of pages6
JournalOrganic Electronics
Issue number3
StatePublished - Mar 2012

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: H.U.K. acknowledges the financial support from IRTG/1404 (funded by the DFG) and Max Planck Society (Germany). This project was funded by the National Science Foundation Materials Research Science and Engineering Center of Polymer and Macromolecular Assemblies (DMR0 213618), National Science foundation (ECCS0730710) and the Office of Naval Research (N000140810654). M.E.R. acknowledges partial support from the NASA GSRP fellowship; O.J. acknowledges partial support from a Hewlett Packard graduate fellowship. (Supplementary information is available online from Wiley InterScience or from the author).

ASJC Scopus subject areas

  • Materials Chemistry
  • Biomaterials
  • General Chemistry
  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering
  • Condensed Matter Physics


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