Determination of C-reactive protein by PAMAM decorated ITO based disposable biosensing system: A new immunosensor design from an old molecule.

This paper demonstrates a new and sensitive electrochemical immunosensor for the analysis of C-reactive protein, an important marker of inflammation. Indium Tin Oxide (ITO) disposable sheets were modified by using 11-cyanoundecyltrimethoxysilane (CUTMS) and PAMAM dendrimers (G:1 amino surfaces) for the first time to immobilize the anti-CRP antibody via covalent interactions. Cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS), as well as square wave voltammetry (SWV) methods, were applied to characterize the immobilization stages of anti-CRP and to determine the CRP concentrations. Charge transfer resistance changes were highly linear and sensitive to CRP concentration in the range 21-6148 fg mL-1 and were associated with a limit of detection of 0.34 fg mL-1. The system had acceptable repeatability (6.45%, n = 18) and good storage stability (4.5% loss after 6 weeks). Moreover, the binding characterization of CRP to anti-CRP was monitored by a single frequency impedance technique. The amount of CRP in human serum samples was analyzed with a fabricated biosensor to determine the feasibility of the biosensing system for medical purposes. We suggest that 11-CUTMS, a new silanization agent, is ideal for biosensor applications.