Detection of proteins on membranes and in microchannels using copper staining combined with scanning electrochemical microscopy

Scanning electrochemical microscopy (SECM) and copper staining are combined to achieve visualisation of proteins on surfaces. Proteins are adsorbed on a polyvinylidene fluoride (PVDF) membrane or on a polyethylene terephthalate (PET) surface and stained using a standard protocol involving copper salts. Salts are then reduced to copper and detected by SECM with ferrocene methanol as a redox mediator in aqueous solution. During the SECM scan, the potential is held at a value at which the oxidation of the redox mediator occurs and a positive feedback current is detected when scanning over copper clusters. A negative feedback is observed elsewhere. This method enables unspecific protein adsorption mapping on polymeric membranes and into microchannels without any requirement of enzymatic activity or affinity to a labelled secondary reporter.