Electrochemical immunosensor utilizing electrodeposited Au nanocrystals and dielectrophoretically trapped PS/Ag/ab-HSA nanoprobes for detection of microalbuminuria at point of care.

In this study, we have fabricated a simple disposable electrochemical immunosensor for the point of care testing of microalbuminuria, a well-known clinical biomarker for the onset of chronic kidney disease. The immunosensor is fabricated by screen-printing carbon interdigitated microelectrodes on a flexible plastic substrate and utilizes electrochemical impedance spectroscopy to enable direct and label free immunosensing by analyzing interfacial changes on the electrode surface. To improve conductivity and biocompatibility of the screen-printed electrodes, we have modified it with gold nanoparticles, which are electrodeposited using linear sweep voltammetry. To enable efficient immobilization of HSA antibodies, we have developed novel PS/Ag/ab-HSA nanoprobes (polystyrene nanoparticle core with silver nanoshells covalently conjugated to HSA antibodies), and these nanoprobes are trapped on the electrode surface using dielectrophoresis. Each immunosensor has two sensing sites corresponding to test and control to improve specificity by performing differential analysis. Immunosensing results show that the normalized impedance response is linearly dependent on albumin concentration in the clinically relevant range with good repeatability. We have also developed a portable impedance readout module that can analyze the data obtained from the immunosensor and transmit it wirelessly for cloud computing. Consequently, the developed immunosensing platform can be extended to the detection of a range of immunoreactions and shows promise for point of diagnosis and public healthcare monitoring.