Photoelectrochemical MicroRNA Sensing Based On Semiconductor Nanocomposites

MicroRNAs(miRNAs)are a class of small endogenous noncoding RNAs that play a significant role in the cell differentiation and proliferation,tumor metastasis,viral replication,and neurodegeneration.Thus,the development of new methods for the detection of miRNAs that are rapid,convenient,sensitive,selective and quantitative is urgently required.Photoelectrochemical(PEC)measurement is a newly developed analytical technique for biological assays and has received considerable attention in recent years.Due to the complete separation of the excitation source(light)and the detection signal(current),the background signal in PEC techniques is reduced,and the detection sensitivity is significantly improved.Furthermore,PEC measurement is more rapid,convenient,and sensitive and has greater accuracy than conventional optical and electrochemical methods.In this paper,on the basis of semiconductor nanocomposites,two strategies for PEC detection of miRNAs are designed.1 A universal PEC biosensing platform is developed based on DNA-CdS quantum dots(QDs)sensitized single-walled carbon nanotubes(SWCNTs)-COOH.The DNA-CdS QDs act as a probe and are synthesized by a one-pot method that represents a simpler alternative to the previously reported method.The DNA-labeled CdS QDs are used to sensitize the SWCNTs-COOH as a photoelectrochemically active species by π-π stacking and exhibit high photovoltaic conversion efficiency and good stability.MiRNAs are a class of small endogenous noncoding RNAs that play a significant role in the regulation of a variety of biological processes.Using miRNA-7f as a model to create a novel signal-off PEC biosensor;this miRNA causes a large quantity of CdS QDs to break away from the SWCNTs-COOH after hybridizing with a DNA probe,resulting in a decrease in the photocurrent.This strategy is designed to enable the direct detection of miRNA,which is less expensive,more convenient and time-saving than the indirect detection of miRNAs.Under visible light(405 nm)irradiation at low potentials(-0.05 V)combines with cyclic enzymatic amplification,the PEC biosensor for miRNA-7f exhibits a wide linear detection range from 50 fM to 100 pM with a detection limit of 34 fM a signal-to-noise ratio of 3.This work describes a novel,sensitive and selective strategy for the direct PEC detection of miRNAs,which provides a novel approach for miRNA analysis and may have applications in clinical diagnosis.2 The gold nanoparticles(Au NPs)are conjugated to the ZnSe-COOH nanocrystallines(NCs)modified electrodes through the reaction between COOH and NH2 groups for obtaining semiconductor nanocomposites as photoelectrochemically active species.With the localized surface plasmon resonance(LSPR)of Au NPs,the direct electron transfer(DET)generate hot electrons of Au NPs which inject into the ZnSe NCs semiconductor,an enhanced photocurrent is obtained.Therefore,an innovative PEC biosensing platform is developed.MiRNA-122a is chosen as a model analyte,which can hybridize to a probe molecule,forming 21 bp double stranded RNA(dsRNA).P19 protein can block the electron donor to the electrode surface.Taking advantage of the specificity and high affinity of p19 protein to 21-23 bp dsRNA which results in decreasing PEC response,a sensitive PEC biosensor for direct detection of miRNA is fabricated.The exquisite PEC biosensor can be operated with a wide linear range from 350 fM to 5 nM,and the detection limit was down to 153 fM.Moreover,the facile biosensor exhibits rapid response,ult:rahigh sensitivity and specificity towards the detection of miRNA.Au NPs are conjugated to the ZnSe-COOH NCs which generates LSPR to improve the PEC detection sensitivity,promoting the development of PEC biosensing,extending the applications of semiconductor nanocomposites and having promising perspective.