CdSe quantum dot-functionalized TiO2 nanohybrids as a visible light induced photoelectrochemical platform for the detection of proprotein convertase subtilisin/kexin type 6

Proprotein convertase subtilisin/kexin type 6 (PCSK6) plays a major role in promoting the progression of rheumatoid arthritis to a higher aggressive status. A novel highly sensitive photoelectrochemical platform was developed for the detection of PCSK6 by using CdSe quantum dots (QDs)-functionalized TiO2 nanoparticles (NPs) nanohybrids (TiO2@CdSe) as the photo-to-electron conversion medium. TiO2@CdSe showed excellent visible-light absorbency, and much higher photoelectrochemical activity than both CdSe QDs and TiO2 NPs. The 5′ and 3′ primers of PCSK6 ssDNA acted as capture probes to realize the detection of PCSK6 ssDNA by the specific recognition. The capture probes can be fixed by poly-l-lysine (PLL) through positively strong electrostatic attraction and the carboxyl group of TiO2@CdSe nanohybrids. PLL was electropolymerized on ITO electrode by cyclic voltammetry (CV). Simultaneously, the amino group of PLL can interact with the carboxyl group of TiO2@CdSe nanohybrids to enhance the stability of the photoelectrochemical signal. The fabricated aptsensor exhibited excellent performance towards PCSK6 with a wide linear range (0.5 pg/mL to 80.0 ng/mL) and a detection limit of 0.1 fg/mL. This work opens up a new detection platform for PCSK6 with good sensitivity, reproducibility and stability.