A reliable quantification of protein markers will undoubtedly underpin profound developments in disease surveillance, diagnostics, and improved therapy. Although there potentially exist numerous means of achieving this, electrochemical impedimetric techniques offer scale of sensitivity, cost, convenience, and a flexibility with which few alternatives can compete. Though there have been marked developments in electroanalytical protein detection, the demands associated with accessing the inherent assay sensitivity in complex biological media largely remains. We report herein the use of cysteamine-graphene oxide modified gold microelectrode arrays in underpinning the ultrasensitive and entirely label free non-faradaic quantification of Parkinson's-relevant autoantibodies in human serum.