Platelet-derived growth factor (PDGF) is a potential cancer marker, which will play an important role in early detection of cancers. Due to its trace amounts in contrast to abundant proteins and other interfering species in blood sample, it is difficult to be detected. Electrochemical Proximity Assay (ECPA) is an extremely flexible and sensitive technique with high potential for quantitation of a variety of proteins in clinical laboratory settings or at the point-of-care systems. In this study, we applied ECPA strategy on the PDGF recognition to achieve high sensitivity and specificity. Different with previous ECPA approach in which signals are only read out by electrochemical measurement, three characterization techniques including surface plasmon resonance, electrochemistry and fluorescence spectroscopy are combined together here so that these techniques are capable of cross-validating and complementing each other.

With the combined advantages of these techniques, the limit of detection of PDGF quantification reaches as low as picomolar level. More importantly, the cross-validation of signals contributes to identification of the interference from non-specific binding, and further improvement of the detection accuracy. In this research, the influence factors such as concentration of biosensor’s components, injection time and flow rate were studies, the response linear range, sensitivity and selectivity of PDGF detection were obtained. Furthermore, the mechanisms of action and dynamics of sensing and protein recognition in the process of PDGF recognition was investigated. This work not only provides an accurate quantitation information for biomarker PDGF, but allows a fundamental understanding of the biosensor formation with an unprecedented level, which can overcome several key limitations of current, widely-used surface characterization technologies.