A reusable piezoelectric immunosensor using antibody-adsorbed magnetic nanocomposite

This paper reports a simple, sensitive, and reusable piezoelectric immunosensor using magnetic hydroxyapatite (HAP)/gamma-Fe2O3/Au nanocomposite. Use of porous HAP nanocrystals embedded with gamma-Fe2O3 and colloidal gold nanoparticles resulted in a multifunctional HAP/gamma-Fe2O3/Au nanocomposite. Under optimized conditions, the biocompatible nanocomposites were exploited for direct adsorption of large quantities of rabbit anti-human immunoglobulin G antibodies (anti-hIgG) with well-preserved immunoactivity. In a homogeneous bulk solution, the hIgG analytes were captured by the anti-hIgG-derivatized immunocomposites followed by magnetic separation/enrichment onto a bovine serum albumin (BSA)-sealed QCM probe before measuring. This QCM immunosensor can quantitatively determine concentrations of hIgG ranging from similar to 20 to 800 ng/ml, with a detection limit of similar to 15 ng/ml. Moreover, regeneration of the immunosensor can be simply realized by canceling the controllable magnetic field. With the possibility of performing the analysis automatically and considering its ease of use, high sensitivity, and good reusability, this magnetic separation-assisted QCM immunosensor may have great potential to be further tailored as a general and promising alternative for a broad range of practical applications. (C) 2008 Elsevier B.V. All rights reserved.