Reversible biofunctionalization of surfaces with a switchable mutant of avidin

Bioconjug Chem. 2013 Oct 16;24(10):1656-68. doi: 10.1021/bc400087e. Epub 2013 Sep 9.

Abstract

Label-free biosensors detect binding of prey molecules (″analytes″) to immobile bait molecules on the sensing surface. Numerous methods are available for immobilization of bait molecules. A convenient option is binding of biotinylated bait molecules to streptavidin-functionalized surfaces, or to biotinylated surfaces via biotin-avidin-biotin bridges. The goal of this study was to find a rapid method for reversible immobilization of biotinylated bait molecules on biotinylated sensor chips. The task was to establish a biotin-avidin-biotin bridge which was easily cleaved when desired, yet perfectly stable under a wide range of measurement conditions. The problem was solved with the avidin mutant M96H which contains extra histidine residues at the subunit-subunit interfaces. This mutant was bound to a mixed self-assembled monolayer (SAM) containing biotin residues on 20% of the oligo(ethylene glycol)-terminated SAM components. Various biotinylated bait molecules were bound on top of the immobilized avidin mutant. The biotin-avidin-biotin bridge was stable at pH ≥3, and it was insensitive to sodium dodecyl sulfate (SDS) at neutral pH. Only the combination of citric acid (2.5%, pH 2) and SDS (0.25%) caused instantaneous cleavage of the biotin-avidin-biotin bridge. As a consequence, the biotinylated bait molecules could be immobilized and removed as often as desired, the only limit being the time span for reproducible chip function when kept in buffer (2-3 weeks at 25 °C). As expected, the high isolectric pH (pI) of the avidin mutant caused nonspecific adsorption of proteins. This problem was solved by acetylation of avidin (to pI < 5), or by optimization of SAM formation and passivation with biotin-BSA and BSA.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Avidin / chemistry*
  • Avidin / genetics
  • Biosensing Techniques / instrumentation
  • Biotin / chemistry*
  • Biotinylation
  • Immobilized Proteins / chemistry*
  • Immobilized Proteins / genetics
  • Point Mutation
  • Surface Properties

Substances

  • Immobilized Proteins
  • Avidin
  • Biotin