Enhancement of the sensitivity of surface plasmon resonance (SPR) immunosensor for the detection of anti-GAD antibody by changing the pH for streptavidin immobilization

Sue Hyung Choi, Jung Wook Lee, Sang Jun Sim

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16 Citations (Scopus)


Surface plasmon resonance (SPR) immunobiosensor was developed for the detection of anti-glutamic acid decarboxylase (GAD) antibody. In this study, carboxylic terminated self-assembled monolayer, which was prepared by mixing of 3-mercaptopropionic acid (3-MPA) and 11-mercaptoundecanoic acid (11-MUA) (10:1 ratio), was used to evaluate the effect of external pH on the affinity between streptavidin and sensor surface. At pH values ranging from 4.0 to 5.5, it was found that streptavidin could more easily access onto the sensor surface at higher pH, and the enhanced binding of streptavidin at high pH allowed more extensive immobilization of biotin-GAD, which serves as the epitope for anti-GAD antibody. Consequently, the increase of RU caused by immuno-response between GAD and anti-GAD antibody was remarkably higher when streptavidin was bound on to the sensor surface at pH 5.5 than at pH 4.5. Therefore, we could conclude that the pH of coupling buffer greatly influences the sensitivity of immunosensor.

Original languageEnglish
Pages (from-to)683-687
Number of pages5
JournalEnzyme and Microbial Technology
Issue number6-7
Publication statusPublished - 2004 Dec 1
Externally publishedYes



  • Carboxylic terminated SAMs
  • Glutamic acid decarboxylase
  • Immunosensor
  • Streptavidin
  • Surface plasmon resonance

ASJC Scopus subject areas

  • Biochemistry
  • Biotechnology
  • Applied Microbiology and Biotechnology

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