Electro-engineered polymeric films for the development of sensitive aptasensors for prostate cancer marker detection

We report the development of a simple surface chemistry strategy for the construction of sensitive aptasensors on a polypyrrole (PPy) – polyethylene glycol (PEG) platform in order to provide enhanced anti-fouling properties. We report the covalent modification of a PPy film formed on a gold electrode by PEG molecules, without prior chemical functionalization of the pyrrole monomer. This process was mediated by electro-oxidation of amine groups present on the one of the PEG's end chains. Poly-histidine modified aptamers were immobilized to this surface via a Nα,Nα-Bis(carboxymethyl)-L-lysine ANTA/Cu²⁺ redox complex covalently attached to the PPy-PEG adduct. The fabricated aptasensor was then utilized for the detection of α-methylacyl-CoA racemase (AMACR; P504S), an emerging biomarker for prostate cancer. Protein/aptamer interactions were monitored through variation of the copper redox signal, using the square wave voltammetry (SWV) technique. We demonstrate that the PPy-PEG-ANTA/Cu²⁺ hybrid material is characterized by enhanced anti-fouling properties and sensitivity. The aptasensor was able to detect AMACR down to 5 fM both in buffer and spiked human plasma with a limit of detection (LOD) of 0.15 fM and 1.4 fM, respectively. The developed aptasensor can be generalized for use with any type of aptamer-based sensor.