Immunoassay of interferon gamma by quartz crystal microbalance biosensor

Interferon gamma (IFN gamma) is a cytokine and an immunochemical marker that can be used for revealing of infectious diseases and especially for distinguishing of viral and some types of bacterial infections. Blood tests for IFN gamma are typically based on immunoassays like Enzyme-Linked Immunosorbent Assay (ELISA). In this paper, a biosensor working on the principle of quartz crystal microbalance (QCM) was developed as an alternative to the standard analytical methods for IFN gamma. The biosensor contained antibodies against IFN gamma immobilized on QCM and also on gold nanoparticles. A sandwich containing QCM, gold nanoparticles and IFN gamma was formed and formation of the sandwich caused decrease of oscillation frequency. The assay exerted limit of detection 5.7 pg/ml for a sample sized 50 mu l and one measuring cycle was finished within 90 min. The assay by biosensor fully correlated to standard ELISA. In a conclusion, the biosensor appears to be a fully applicable analytical tool for a simple assay of IFN gamma. Overall simplicity and no special requirement on staff and equipment are the major advantages of the here presented assay.