We have developed a label-free method for estimating protein concentration by measuring the binding force between two surfaces, which were coated with the target protein (avidin) and its ligand (biotin), respectively. When the biotin-coated surface was placed in avidin solution, avidins in the solution bound with the biotins on the surface depending on the concentration of avidin. Then, the biotin-coated surface was contacted with the avidin-coated surface. It resulted in forming a specific bond between two surfaces since the avidins immobilized on the surface bound with the unattached biotins. We measured the binding force between two surfaces by a piezoresistive cantilever. We confirmed that the binding force decreased with the increase of the concentration of avidin. This indicates that our method is capable of measuring protein concentration.

References :
Kenta Kuwana, Kiyoshi Matsumoto, Isao Shimoyama, "MEASUREMENT OF PROTEIN CONCENTRATION USING THE BINDING FORCE BETWEEN TWO SURFACES," The 12th International Conference on Miniaturized Systems for Chemistry and Life Sciences (microTAS2008), pp. 982-984, San Diego, USA, October 12-16, 2008.