Optical Stimuiation Type Signal Amplification Strategy Is Used Precise Imaging Detection Of Biomolecules

Deoxyribozyme（DNAzyme）probes have great potential for accurate molecular imaging due to their flexible programmability and easy synthesis.However,the"always active"sensing mode adopted by traditional DNAzyme probes will generate passive signal response when they encounter targets at incorrect time points and positions,which will inevitably lead to false positive signals.Secondly,the fluorescent dye molecules labeled with DNAzyme are easily photobleached,which inevitably reduces the detection sensitivity.Near infrared light activation technology can selectively activate the target at the required time and location,so as to control the reaction start-up and effectively avoid false positive signals.The plasma enhanced fluorescence（PEF）technology can greatly improve the fluorescence intensity of dye molecules,and improve the stability and sensitivity of fluorescence signal.Therefore,in this paper,an intelligent DNAzyme platform for controllable ultra-sensitive molecular imaging was designed by combining near-infrared light activation technology with plasma enhanced fluorescence,which realized highly sensitive detection of important tumor markers miRNA and spatiotemporal controllable accurate imaging.The main work carried out in this paper is as follows:（1）a DNA computation mediated DNAzyme platform that can be activated by 808 nm NIR light and target c-MYC was designed for spatiotemporally controlled ultrasensitive AND-gated molecular imaging.Particularly,the sensing and recognition function of the traditional DNAzyme platform was inhibited by introducing a blocking sequence containing a photo-cleavable linker（PC-linker）that can be indirectly cleaved by 808 nm NIR light and thus enables the AND-gated molecular imaging.According to the responses toward three designed SDz,n PC-SDz,and m-SDz DNAzyme probes,the fluorescence recovery in diverse cell lines（MCF-7,He La,and L02）and inhibitor-treated cells was investigated to confirm the AND-gated sensing mechanism.It is worth noting that thanks to the strand displacement amplification and the ability of gold nanopyramids（Au NBPs）to enhance fluorescence,the fluorescence intensity increased by～7.9 times and the detection limit decreased by nearly 40.5 times.Moreover,false positive signals can be also excluded due to such AND-gated design.Furthermore,such a designed“AND-gate”sensing manner can also be applied to spatiotemporally controlled ultrasensitive in vivo molecular imaging,indicating its promising potential in precise biological molecular imaging.（2）The plasma enhanced fluorescence technology and spatiotemporal control technology are introduced into the DNAzyme Walker sensor with protective functional domain.A DNAzyme Walker system activated by 808 nm near-infrared light based on gold nanostar@silica（Au NSTs@Si O₂）was constructed to achieve highly sensitive and accurate detection and imaging of tumor marker miRNA-21 in living cells.By introducing a protective functional domain in the middle of the catalytic core of DNAzyme,self-protective DNAzyme walker is generated,effectively avoiding the impact of RNA cleavage site caused by endogenous nuclease cleavage.At the same time,because the gold nanostar has good plasma enhanced fluorescence performance,compared with the DNAzyme Walker system without plasma enhanced materials,the detection signal is enhanced 19.8 times,significantly improving the detection sensitivity.In this paper,the detection limit of DNAzyme Walker system activated by 808 nm near-infrared light is as low as 0.26 p M.The excellent performance and scalability of this DNAzyme Walker system holds great promise for cancer diagnosis and related biomedical applications.