Construction Of MXenes Nanoprobes And Their Application In Noncoding RNA Imaging

MXenes are a novel type of two-dimensional material composed of transition metal carbides,and either nitrides or carbonitrides.They share a general formula of M_n+1X_n(n=1-3),where M is an early transition metal(e.g.Sc,Ti,Zr,Hf,V,Nb,Ta,Cr,Mo),and X is a carbon or nitrogen.Since its initial discovery in 2011,MXenes have attracted a great deal of research interest in various fields,such as physics,energy evolution,environmental science,and nanomedicine.Particularly,the ultrathin Ti₃C₂nanosheets show a forceful and broad absorption from 400 to 1200 nm,as well as the high photothermal conversion efficiency.Combined with its excellent biocompatibility and biodegradability,Ti₃C₂MXenes have great potential in constructing biosensors.In this paper,Ti₃C₂MXenes were functionalized and applied to construct biosensors.The details are as follows:(1)Preparation and functionalization of Ti₃C₂MXenes.Using Ti₃Al C₂MAX powder as the raw material,single layer Ti₃C₂MXenes were prepared by simple one-step ultrasonic etching in Li F-HCl(9 M)solution.After that,the surface of Ti₃C₂MXenes were functionalized by carboxyrich(PAA)based on the strong coordination between carboxyl group and titanium atom(Ti₃C₂-PAA),which made its biocompatibility greatly improved.Then,Ti₃C₂-PAA were proved to have a good light-to-heat conversion ability,laying a foundation for its subsequent use in biosensing.(2)Functional Ti₃C₂MXenes-loaded entropy-driven RNA explorer(EDRE)for long noncoding RNA PCA3 imaging in live cells.Based on the work above,cystamine(Cys)and the TAT peptide were stepwise coupled on the surface of Ti₃C₂-PAA via EDC/NHS coupling to construct the TAT peptide-functionalized Ti₃C₂MXenes(Ti₃C₂-TAT).The negatively charged EDRE was loaded on the Ti₃C₂-TAT by electrostatic interaction to construct the Ti₃C₂-TAT@EDRE probe.EDRE has high sensitivity and specificity for detection of PCA3 in vitro,with a detection limit of 2.6p M.The Ti₃C₂-TAT@EDRE was further used for imaging of lnc RNA PCA3 in the nucleus of living cells.When incubated with cells,the complexes(Ti₃C₂-TAT@EDRE)entered the cytoplasm,in which the high concentrations of glutathione(GSH)broke the disulfide bonds in Ti₃C₂-TAT by thiol-disulfide exchange,causing the efficient release of TAT peptides and EDRE.The released EDRE was delivered into the nucleus via the TAT peptide.The fluorescence signal was achieved by the reaction of the target lnc RNA PCA3 with EDRE.Consequently,fluorescence analysis of lnc RNA PCA3 at low-picomolar concentrations in vitro as well as sensitive live cell imaging of lnc RNA PCA3 in the nucleus of androgen receptor-positive LNCa P prostate cancer cells were achieved,thereby promoting the applications potential of functionalized Ti₃C₂MXenes to a deeper level in biosensing and biomedicine.(3)Functional Ti₃C₂MXenes-loaded NIR-triggered EDRE(NEDRE)for the therapeutic diagnosis of tumors.On the basis of work 1 and 2,we covalently connected the signal reporter(SR)to Ti₃C₂-PAA(Ti₃C₂-SR)through EDC/NHS coupling.Subsequently,the PEI functionalization of Ti₃C₂-SR made the surface of the material positively charged,which not only enhanced the material-cell binding ability,but also adsorbed the fuel chain P5 on the surface of the material through electrostatic interactions(Ti₃C₂-NEDRE).NEDRE has shown extremely high sensitivity and specificity in detecting mi RNA-21 in vitro.We further used the Ti₃C₂-NEDRE probe for the imaging of mi RNA-21 in living cells.After the material entered the cell,the surface temperature of the material was increased by NIR irradiation,and the amino anchor chain P1 in NEDRE was separated.In the presence of mi RNA-21,the chain replacement reaction was triggered to achieve fluorescence recovery and amplification.This method realized the ultra-sensitive detection of mi RNA-21 and the spatiotemporal controllable cell imaging of mi RNA-21 in living cells,and achieved photothermal destruction of cancer cells.At the same time,owing to the good penetrating of near-infrared light,this method has good application potential in the photothermal therapy of living body.