Voltammetric aptamer based detection of HepG2 tumor cells by using an indium tin oxide electrode array and multifunctional nanoprobes

The authors describe a method for the detection and determination of human liver cancer cells in blood. The cytosensing system consists of a microfabricated chip-based electrochemical aptasensor that contains multifunctional hybrid electrochemical nanoprobes and an indium tin oxide (ITO) electrode array interface functionalized with cell-targeting aptamer and gold nanoparticles (AuNPs). The thiolated cell targeting aptamer (referred to as TLS11a) was immobilized on the ITO electrode/AuNPs for specific adhesion of hepatocellular carcinoma cells (HepG2). The hybrid nanoprobe system consists of hydroquinone (HQ) as an electrochemical probe, horseradish peroxidase (HRP), and an aptamer/hemin/G-quadruplex aggregate that was immobilized on gold/palladium-functionalized ZnO nanorods (ZnO@Au-Pd). The nanoprobes are capable of amplifying the voltammetric signal and capturing the target cells. Best operated at around −90 mV (vs Ag/AgCl), the electrode has a linear response that covers the 10^2 to 10^7 HepG2 cells per mL concentration range, with a 10 cell per mL detection limit. Captured cells may be released from the electrode via electrochemical desorption to break the Au-S bonds. Schematic of an indium tin oxide (ITO) electrode array-based electrochemical aptamer cytosensor for the specific capture, sensitive detection and controlled release of HepG2 cancer cells. AuNP: gold nanoparticle; HQ: hydroquinone; HRP: horseradish peroxidase.