Light-harvesting iridium (III) complex-sensitized NiO photocathode for photoelectrochemical bioanalysis.

Abstract

Anovel iridium (III) complex bearing boron dipyrromethene (Bodipy) as the light-harvesting antenna has been synthesized and is firstly employed as photosensitizer to assemble adye-sensitized NiO photocathode. The assembled photocathode exhibits significantly improved photoelectrochemical (PEC) performance. Integrating the prepared photocathode with hybridization chain reaction (HCR)--based signal amplification strategy, a cathodic PEC biosensor is proposed for the detection of microRNA-133a (miRNA-133a). In the presence of thetarget, HCR is triggered to form long duplex concatamers on the photocathode, which allows numerous manganese porphyrins (MnPP) to bind in the dsDNA groove. With the help of H2O2, MnPP with peroxidase-like activity catalyzes 4--chloro-1-naphthol (4-CN) to produce benzo--4--chlorohexadienone (4-CD) precipitate on the electrode, leading to a significant decrease of photocurrent signal. The decreased photocurrent correlates linearly with the target concentration from 0.1 fM to 1nM with a detection limit of 66.2 aM (S/N = 3). Theproposed PEC strategy exhibits delightful selectivity, reproducibility and stability.