Piezoelectric immunoassay for complement C4 based on a Nafion-modified interface for antibody immobilization

A piezoelectric immunosensor based on a Nafion membrane interface with a simple immobilization procedure has been developed for the determination of complement C4 in human serum. The polyanionic perfluorosulfonated Nafion polymer was used to modify the electrode surface of quartz-crystal microbalance (QCM) as a platform for the immobilization of complement C4 antibodies. The surface morphology of QCM modified with Nafion membrane was investigated using scanning electron microscopy. The system was optimized with regard to the parameters involved in the preparation of the immunosensor and the assay process. The proposed immunosensor responds well to C4 in the range of 0.08-1.6 μg/ml with a relative standard deviation of <5.3%. Moreover, the proposed immunosensor has advantages in terms of the speed and simplicity of the immobilization procedure as well as the simple and advantageous regeneration process. The experimental results obtained with regard to nonspecific adsorption and recovery indicate that the proposed immunosensor offers a promising alternative tool for the clinical diagnosis of complement C4.