Reagentless fluorescent biosensors from artificial families of antigen binding proteins

Biosens Bioelectron. 2011 Jun 15;26(10):4184-90. doi: 10.1016/j.bios.2011.04.030. Epub 2011 Apr 22.


Antibodies and artificial families of antigen binding proteins (AgBP) are constituted by a connected set of hypervariable (or randomized) residue positions, supported by a constant polypeptide backbone. The residues that form the binding site for a given antigen, are selected among the hypervariable residues. We showed that it is possible to transform any AgBP of these families into a reagentless fluorescent biosensor, specific of the target antigen, simply by coupling a solvatochromic fluorophore to one of the hypervariable residues that have little or no importance for the interaction with the antigen, after changing this residue into cysteine by mutagenesis. We validated this approach with a DARPin (Designed Ankyrin Repeat Protein) and a Nanofitin (also known as Affitin) with high success rates. Reagentless fluorescent biosensors recognize their antigen in an immediate, quantitative, selective and specific way, without any manipulation of the sample to analyze or addition of reagent.

Publication types

  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Ankyrin Repeat
  • Antigens / analysis*
  • Biosensing Techniques / methods*
  • Biosensing Techniques / statistics & numerical data
  • Carrier Proteins / chemistry*
  • Carrier Proteins / genetics
  • Cysteine / chemistry
  • Cysteine / genetics
  • Fluorescent Dyes
  • Indicators and Reagents
  • Models, Molecular
  • Mutagenesis
  • Protein Engineering


  • Antigens
  • Carrier Proteins
  • Fluorescent Dyes
  • Indicators and Reagents
  • Cysteine