An optical tweezers-based immunosensor for detection of femtomoles-per-liter concentrations of antigens.
We used optical tweezers--optical trapping with focused laser beams--to pull microspheres coated with antigens off of an antibody-coated surface. Using this technique, we could quantify the force required to separate antigen to antibody bonds. At very low surface density of antigen, we were able to detect the single antigen to antibody binding. The force required to break the antigen-antibody bonds and pull the microsphere off the surface was shown to increase monotonically with increasing surface density of antigens. Using the force determination as a transducer, we were able to detect concentrations of free antigens in solution as small as 10(-15) mol/L in a competitive binding assay.
Helmerson
K
K
Biotechnology Division, National/Institute of Standards and Technology, Gaithersburg, MD 20899, USA. kristian.helmerson@nist.gov
Kishore
R
R
Phillips
W D
WD
Weetall
H H
HH
D000937:Antigen-Antibody Reactions; D000941:Antigens / Q000737:chemistry*; D001667:Binding, Competitive; D004305:Dose-Response Relationship, Drug; D007834:Lasers; D055095:Optics and Photonics; D012709:Serum Albumin / Q000737:chemistry
D000941:Antigens; D012709:Serum Albumin