Amperometric Immunosensor for Direct Detection Based upon Functional Lipid Vesicles Immobilized on Nanowell Array Electrode

An original electrochemical immunosensor has now been developed that is based upon the spontaneous immobilization of biotinylated, functional lipid vesicles (FLVs) on a polymeric resist layer. An electrode was fabricated utilizing a form of electron-beam (e-beam) that has been used to fabricate 200 nm (nanoscale) wells in the resist layer covering of the gold electrode. The stability of adhered FLVs upon the nanowell (NW) electrode was observed by atomic force microscopy (AFM). From these observations, we were able to determine that the assembled FLVs primarily adhered as individual molecules, that is, without the aggregation or fusion noted in earlier designs. Additionally, these immobilized FLVs demonstrated clearly defined redox activity in electrochemical measurements. Streptavidin, biotinylated capture antibody, and target proteins were consequently injected in order to set up the immunoassay environment. Electrochemical immunoassay experimentation was performed on the NW array electrode with model proteins, such as human serum albumin (HSA) and carbonic anhydrase from bovine (CAB). We observed a notable current decrease, following the redox path, interrupted by the target HSA, indicating the binding of the capture antibody with the target antigen. On the basis of these results, we propose a new type of immunosensor incorporating this mechanism of spontaneous immobilization of FLVs.