Laser ablative TiO2 and tremella-like CuInS2 nanocomposites for robust and ultrasensitive photoelectrochemical sensing of let-7a

A photoelectrochemical (PEC) biosensor based on a multiple signal amplification strategy was established for highly sensitive detection of microRNA (miRNA). TiO2 was prepared on the surface of titanium sheet by laser etching to improve its stability and photoelectrical properties, and CuInS2-sensitized TiO2 was used to form a superior photoelectrical layer, which realized the initial signal amplification. The electron donor dopamine (DA) was modified to H2 as a signal regulator, which effectively increased the photocurrent signal. To further amplify the signal, an enzyme-free hybridization reaction was implemented. When target let-7a and fuel-DNA (F-DNA) were present, the base of H1 specifically recognized let-7a and forced dopamine@AuNPs-H2 away from the electrode surface. Subsequently, the end base of H1 specifically recognized F-DNA, and let-7a was replaced and recycled to participate in the next cycle. Enzyme-free circulation, as a multifunctional amplification method, ensured the recycling of target molecules. This PEC sensor for let-7a detection showed an excellent linear response from 0.5 to 1000 pM with a detection limit of 0.12 pM. The intra-batch RSD was 3.8% and the recovery was 87.74-108.1%. The sensor was further used for clinical biomolecular monitoring of miRNA, showing excellent quantitative detection capability.

Automated summary

A photoelectrochemical biosensor based on a multiple signal amplification strategy was developed for highly sensitive detection of microRNA. The sensor utilized TiO2 and CuInS2-sensitized TiO2 layers to enhance photoelectrical properties and achieve initial signal amplification. Signal amplification was further carried out through an enzyme-free hybridization reaction. The sensor exhibited excellent linear response, with a wide detection range and low detection limit. Clinical biomolecular monitoring of miRNA using this sensor demonstrated excellent quantitative detection capability.