Construction Of DNA Fluorescence Sensing Systems Based On Two-dimensional Nanomaterials And Their Applications In Water Environment Analysis And Molecular Information Security

The water environment is an important part of the earth biosphere and is closely related to the survival and reproduction of life.Currently,the water environment faces complex ecosystem sustainability issues and severe pollution problems.For example,the proliferation of pathogens in aquaculture（such as Aeromonas hydrophila and Edwardsiella tarda）not only causes huge economic losses,but also harms the health of food fish and indirectly affects human health.In addition,the emission of toxic metal ions produced by human activities not only has an irreparable impact on the ecological environment,but also causes serious harm to the human body.However,the existing analysis methods have problems such as time consuming,high cost,low sensitivity,single function,inability to distinguish valence states,and difficulty in achieving adjustable range detection.In this paper,two-dimensional nanomaterials were used as the platform to construct DNA nanosensors by using the excellent fluorescence quenching ability and the difference in binding ability of different conformational DNA of graphene oxide（GO）nanosheets and oxyhydroxide（CoOOH）nanosheets.Molecular recognition,sequence variable and information coding ability of DNA probes combined with fluorescent dyes（such as aptamers and DNA with variable base sequences）.The DNA fluorescence sensing system was constructed for the highly sensitive detection of fish pathogens,the valence discrimination and dynamic tunable analysis of metal ions,finally,the living imaging diagnosis of fish pathogens infected with carp was realized.In addition,due to the bottom-up self-assembly ability of molecular-scale systems,research on the use of molecular execution logic calculation and information processing has been in the ascendant in recent years.In order to expand the application range of molecular information processing systems,we also use the above molecular systems for logic computing and information hiding and encryption,providing new ways and opportunities for the development of multifunctional molecular systems for sensing and molecular information technology in the future.（1）In this study,we have constructed a simple fluorescent enhanced aptasensor based on GO nanosheets for rapid detection and in vivo imaging for fish pathogens.We used 6-carboxy-fluorescein（FAM）-labeled aptamers as fluorescent probes and GO as a quencher to detect A.hydrophila and E.tarda by monitoring changes in fluorescent signals.The results showed that our method has a wide detection range,demonstrated A.hydrophila and E.tarda could be detected in the concentration range of 0.1 to 1.3×10⁵ CFU/mL and 1.3 to 1.3×10⁴CFU/mL,and detection limit of A.hydrophila and E.tarda were 1.5CFU/mL and 6.7×10¹ CFU/mL,respectively.The results of other non-target bacteria were negative,indicating that the method has good specificity.In addition,the method was successfully applied to the fluorescence detection and imaging of fish pathogens in living organisms.This study provides a new idea and new method for the detection of fish pathogens in the future.（2）In addition,we extend the fluorescence aptasensing system constructed in the previous study to build a GO-based steganographically aptasensing system for information computing,encryption and hiding,which relies on the specific recognition and information coding capabilities of the nucleic acid aptamers as well as the selective adsorption and fluorescence quenching capabilities of GO.Due to its large specific surface area and good quenching ability,GO can adsorb and“hide”FAM-labeled DNA aptamers and their fluorescent signals.Only when the target bacteria are present,the hidden aptamers on GO will appear and restore fluorescence.The system can be used to create physical logic circuits and complex fluorescent logic circuits by utilizing the exchange and change of matter,energy and information.It also acts as a universal dual encryption and steganography system,bypassing the use of electronic communication systems to improve information security.（3）This study combines the base and length variability of DNA,and constructs a DNA-adjustable fluorescence sensing platform based on CoOOH quencher.The dynamic tunable detection of metal ions such as Fe³⁺,Hg²⁺,Cr³⁺and the valence of Fe³⁺and Fe²⁺were successfully realized.The results showed that the binding ability of different base sequence DNA to CoOOH nanosheets was different,the order of precedence was G>C>A>T,and the short chain was better than the long chain.Selective analysis showed that some specific metal ions(such as Fe³⁺,Hg²⁺,Cr³⁺,etc.)have strong specific quenching effect on DNA-CoOOH complexes,and the fluorescence response of DNA-CoOOH complexes with different base sequences to the same metal ions has a big difference,there were different linear ranges of response.Absorption spectroscopy demonstrates that DNA,CoOOH,and metal ions may form a ternary complex through interaction,resulting in significant metal ion-dependent fluorescence quenching.This study provides a basis and basis for the future development of multi-functional,multi-target dynamically adjustable and multi-parameter differentiation detection systems based on DNA sequence and length variability,combined with new functional nanomaterials.