Electrochemical aptasensor of cellular prion protein based on modified polypyrrole with redox dendrimers

• Electrochemical aptamer-based sensor for in vitro detection of prion protein (PrPC).
• Development of polypyrrole covalently attached to redox dendrimer (PAMAM) as a transducer.
• Study of kinetic of the electrochemical process during detection of prion protein following the measurement of heterogeneous electron transfer and coefficient of diffusion.
• Selectivity of the biosensor due to the structure of polypyrrole.

This work consists of the development of an electrochemical aptasensor based on polyprrole modified with redox dendrimers, able to detect human cellular prions PrPC with high sensitivity. The gold surface was modified by conductive polypyrrole film coupled to polyamidoamine dendrimers of fourth generation (PAMAM G4) and ferrocenyl group as redox marker. The aptamers were immobilized on the surface via biotin/streptavidin chemistry. Electrochemical signal was detected by ferrocenyl group incorporated between dendrimers and aptamers layers. We demonstrated that the interaction between aptamer and prion protein led to variation in electrochemical signal of the ferrocenyl group. The kinetics parameters (diffusion coefficient D and heterogeneous constant transfer ket) calculated from electrochemical signals demonstrate that the variation in redox signal results from the lower diffusion process of ions during redox reaction after prion interaction due to bulk effect of larger protein. The association of redox dendrimers with conducting polypyrrole leads to high sensitivity of PrPC determination with detection limit of 0.8 pM, which is three orders of magnitude lower, compared to flat ferrocene-functionalized polypyrrole. Detection of PrPC in spiked blood plasma has been achieved and demonstrated a recovery up to 90%.