Construction Of Electrochemiluminescence System Based On Ti₃C₂T_x MXene-mediated In Situ Generation Of Gold Composite Probes

Electrochemiluminescence（ECL）method is widely used in clinical diagnosis,environmental monitoring and biochemical analysis due to its advantages of good stability,high sensitivity and wide detection range.In the research field of ECL sensing,enhancing the performance of the interface and improving the efficiency of luminophore are the core issues to be solved urgently.With the rapid development of materials science in recent years,nanomaterials have attracted much attention in ECL sensing applications.Ti₃C₂T_x MXene（Ti₃C₂T_x）not only has the excellent commonality of traditional two-dimensional nanomaterials such as good electrical conductivity,strong catalytic ability and large specific surface area,but also has unique reducibility.It has great application potential in ECL biosensing.In this work,we constructed a novel ECL system based on Ti₃C₂T_x mediated in situ generation of gold composite probes combined with nucleic acid signal amplification strategy to achieve the purpose of highly sensitive detection of miRNA-155.The main research contents are as follows:A highly efficient ECL probe（luminol-Au NPs-Ti₃C₂T_x）based on Ti₃C₂T_x mediated in situ forming Au NPs and anchoring luminol was designed,which combines with the catalytic hairpin self-assembly（CHA）reaction as a signal amplification strategy to construct ECL biosensor for sensitive detection of miRNA-155.Herein,Ti₃C₂T_x with rich Ti vacancy defects was used as reducing agent,resulting that Au NPs were generated in situ and anchored on the Ti₃C₂T_x（Au NPs-Ti₃C₂T_x）.Moreover,the Au NPs-Ti₃C₂T_x composites were used as carrier and could provide large number of sites for the efficient linking luminol through Au-N bonds to form stable luminol-Au NPs-Ti₃C₂T_x.The strategy of immobilization ECL emitters with versatility,which not only shorten the electron transmission distance between luminol and electrode,but also provide naked catalytic predominated（111）facets of Au NPs with high electrocatalytic activity,significantly improving the ECL signal of luminol.Furthermore,the catalytic hairpin assembly（CHA）reaction was used resulting in further amplification of the signal.As a result,the as-prepared ECL biosensor exhibited the range was from 0.3 f M to 1 n M with a detection limit of 0.15f M,and it has high reliability detection of miRNA-155 even in human serum samples.The construction of multifunctional ECL probe with excellent ECL emission open a new chapter to develop on the application of Ti₃C₂T_x in the bioanalysis field.Gold nanoclusters（Au NCs）are an emerging electrochemiluminescence（ECL）luminophore with excellent properties such as molecular-like properties and low toxicity,and have great potential in sensing application.However,the application of Au NCs in ECL sensing is still limited because their small size is not conducive to further separation,purification and immobilization,resulting in its low ECL efficiency.In this work,we designed a new strategy to grow Au NC_S in situ on the Ti₃C₂T_x to form luminophore Au NCs@Ti₃C₂T_x based on the unique reducibility of Ti₃C₂T_x,which resulting a great improvement in ECL intensity.Au NCs are firmly anchored on the surface of Ti₃C₂T_x through O atoms,and Au-O-Ti acts as the connection between Au NCs and Ti₃C₂T_x.On the other hand,taking Ti₃C₂T_x nano sheet as the carrier with the large specific surface area and excellent electron transport ability,the fixed load of Au NCs is increased.Skillfully combined with the catalytic hairpin assembly（CHA）and the lateral cutting characteristics of CRISPR-Cas12a,an ECL biosensor was constructed to detect miRNA-155 with good specificity and sensitivity.The linear range was from 0.1 f M to 1.0 n M with a detection limit of 35.7 a M.This research has laid a solid foundation for the development of high-efficiency Au NCs luminophores and ultra-sensitive ECL sensing platforms for clinical and biological analysis.