Ultrasensitive electrochemical microRNA-21 detection based on MXene and ATRP photocatalytic strategy.

A Ti 3 C 2 T x MXene-based biosensor has been developed and the photocatalytic atom transfer radical polymerization (photo ATRP) amplification strategy applied to detect target miRNA-21 (tRNA). Initially, Ti 3 C 2 T x MXene nanosheets were synthesized from the Ti 3 AlC 2 MAX precursor via selective aluminum etching. Then, functionalization of Ti 3 C 2 T x MXene nanosheets with 3-aminopropyl triethoxysilane (APTES) via silylation reactions to facilitate covalent bonding with hairpin DNA biomolecules specifically designed for tRNA detection. Upon binding with the tRNA, the hairpin DNA liberated the azide (N₃) group, initiating a click reaction to affix to the photo ATRP initiator. Through the ATRP photoreaction, facilitated by an organic photoredox catalyst and light, a significant amount of ferrocenyl methyl methacrylate (FMMA) monomer was immobilized on the electrode. Therefore, the electrochemical signal is amplified. The electrochemical efficacy of the biosensor was assessed using square wave voltammetry (SWV). Under optimized conditions, the biosensor demonstrated remarkable sensitivity in detecting tRNA, with a linear detection range from 0.01 fM to 10 pM and a detection limit of 2.81 aM. The findings elucidate that the developed biosensor, in conjunction with the photo ATRP strategy, offers reproducibility, stability, and increased sensitivity, underscoring its potential applications within the experimental medical sector of the biomolecular industry.