Kinetics parameter estimation for the binding process of salicylic acid to human serum albumin (HSA) with capacitive sensing technique

A novel method for real-time investigating the binding interaction between human serum albumin (HSA) and salicylic acid with capacitive sensing technique was successfully proposed. HSA was immobilized on the surface of a gold electrode modified with an insulating poly (o-phenylenediamine) (o-PD) film and colloid Au nanoparticles layers. The bioactivity of HSA was remained and major binding sites were available because of the excellent biocompatibility of gold nanoparticles. The capacitance and interfacial electron resistance of the sensor were altered, owing to the binding of HSA to salicylic acid. The time courses of the capacitance change were acquired with capacitive sensing technique during the binding process. Based on the capacitance response curves with time, the response model for the binding was derived in theory and the corresponding regression parameters were determined by fitting the real-time experimental data to the model. The binding and the dissociation rate constants (k(1) and k(-1)) were estimated to be 54.8 (mol l(-1))(-1) s(-1) and 2.9 x 10(-3) s(-1), respectively. And the binding equilibrium constant (K(a)) was calculated to be 1.89 x 10(4) (mol l(-1))(-1).