Methods for reducing nonspecific interaction in antibody-antigen assay via atomic force microscopy.
We developed a method to measure the rupture forces between antibody and antigen by atomic force microscopy (AFM). Previous studies have reported that in the measurement of antibody-antigen interaction using AFM, the specific intermolecular forces are often obscured by nonspecific adhesive binding forces between antibody immobilized cantilever and substrate surfaces on which antigen or nonantigen are fixed. Here, we examined whether detergent and nonreactive protein, which have been widely used to reduce nonspecific background signals in ordinary immunoassay and immunoblotting, could reduce the nonspecific forces in the AFM measurement. The results showed that, in the presence of both nonreactive protein and detergent, the rupture forces between anti-ferritin antibodies immobilized on a tip of cantilever and ferritin (antigen) on the substrate could be successfully measured, distinguishing from nonspecific adhesive forces. In addition, we found that approach/retraction velocity of the AFM cantilever was also important in the reduction of nonspecific adhesion. These insights will contribute to the detection of specific molecules at nanometer scale region and the investigation of intermolecular interaction by the use of AFM.
Nano-Biotechnology Laboratory, Food Engineering Division, National Food Research Institute, National Agriculture and Food Research Organization, 2-1-12 Kannondai, Tsukuba, Ibaraki 305-8642, Japan.
Jun'ichi
J
Wakayama
Hiroshi
H
Sekiguchi
Satoshi
S
Akanuma
Toshio
T
Ohtani
Shigeru
S
Sugiyama
D000818:Animals; D000906:Antibodies / Q000276:immunology* / Q000378:metabolism*; D002417:Cattle; D003902:Detergents / Q000494:pharmacology; D005293:Ferritins / Q000276:immunology* / Q000378:metabolism*; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D018625:Microscopy, Atomic Force / Q000379:methods*; D011485:Protein Binding / Q000187:drug effects; D013379:Substrate Specificity; D013438:Sulfhydryl Compounds / Q000378:metabolism; D013499:Surface Properties
D000906:Antibodies; D003902:Detergents; D013438:Sulfhydryl Compounds; D005293:Ferritins