Construction Of Optical Nanoprobes For Detecting Silver Ion And Its Applications In Biochemical And Pharmaceutical Analysis

Silver ion plays a bactericidal role at low concentrations.It interacts with thiols,hydroxyl groups,imidazolyl groups,hydrazines,phosphates and so on,further interfering with the normal physiological processes of microorganisms.Therefore,it is also considered to be a"micro-acting bactericide".However,silver ions are also easy to combine with a series of negatively charged molecules,such as inorganic anion,proteins and nucleic acid molecules.When excessive silver ions enter human body,it would replace calcium ions and zinc ions in the bone structure,leading to a chronic silver poisoning,which has a potential threat to the function of liver and kidney.At the same time,with the widespread applications of silver-containing products,such as the silver-containing reagents from electronics,photography and imaging,and more and more drugs and medical materials are also using silver ions and nano-silver technology.Many products that have silver ions or generate silver ions by oxidation also enter to the ecosystem,which pose a potential threat to ecosystems and people who are exposed to the environment.Therefore,it is particularly important to monitor silver ions in environmental and medical materials.In recent years,the number of probes to detect silver ion is quite large.However,owing to the reasons of sensitivity and materials,Thewidespread application of using the detection probes is impeded greatly,and there are few reports about the probes that are successfully used for analysis and detection of complex antibacterial drugs.Meanwhile,there are few further explorations by using the nanoprobes to interact with silver ions.In view of the above problems,we used excellent optical nano-materials CdTe quantum dots（CdTe QDs）and gold nanoparticles（AuNPs）in this work,to achieve the high sensitivity and high selectivity for detection of silver ions in drugs by using fluorescence spectra and dark-field scattering imaging techniques,further expanding their applications in biochemistry and pharmaceutical analysis.The research contents are as follows:1.Optimized and modified optical nanoprobes for highly sensitive detection of active silver ions in antibacterial drugs.First of all,CdTe-QDs was synthesized through hydrothermal synthesis method and the photoluminescence of CdTe QDs can be quenched by silver ions,the fluorescence signal of CdTe-QDs changes significantly.Thereby,it can be used to detect silver ions.However,the fluorescence of CdTe QDs was also easily affected by the acidity and oxidation of the solution and the selectivity was poor,which was not conducive to the rapid analysis of ions.In order to solve the deficiency of stability and selectivity CdTe QDs,AuNPs with excellent LSPR properties is used as plasma light scattering nano-spectral probes.With the help of dark field light scattering imaging technology,we developed a highly sensitive single-particle dark-field light scattering imaging method based on metal-base pairs structures.The DNA sequence containing cytosine mismatched base pairs was simply modified onto AuNPs.The presence of silver ions induced the formation of metal base pair structures,resulting in a decrease the spacing between AuNPs.When plasmon resonance coupling occurred between nanoparticles,the electromagnetic field between them was significantly enhanced,resulting in a change in the intensity and peak shift of the light scattering,thereby achieving the highly sensitive and selective detection of silver ions by counting the number of coupled particles.The method was successfully applied in the detection and analysis of active silver ions in complex antibacterial drugs,and the accuracy of the method was confirmed by comparison with standard method（atomic absorption spectroscopy）.2.Based on the high sensitivity and high selectivity of AuNPs probes for the detection of silver ions,a dark-field light scattering imaging detection platform for the analysis of carcinoembryonic antigen（CEA）,aflatoxin B1（AFB₁）and Ricin B（RTB）was developed.The modified AuNPs probes can detect silver ions with high sensitivity and high selectivity,which was further constructed as an aptamer-complex probes that can specifically detect biomarkers such as carcinoembryonic antigen.Ag⁺mediated the formation,disruption and re-formation of C-Ag⁺-C bond which transformed the dark-field scattered light of AuNPs probes from‘off’to on,and highly sensitive quantitative detection of CEA,AFB₁ and Ricin B was achieved by counting the number of green spots on the dark-field image with software.In summary,the key of our work was to use the nano-spectral probes which can interact with Ag⁺to develop probes with highly sensitive and highly selective detection of Ag⁺with the combination of fluorescence and single-particle dark-field light-scattering microscopy imaging techniques The detection of active silver ions in silver-containing antibacterial drugs was realized,and a single dark-field light scattering microscopy imaging platform,which can be used for biochemical analysis of carcinoembryonic antigen,aflatoxin and ricin was further developed.It contributes to further expanding the application of dark-field light scattering microscopic imaging technology in the field of drug analysis and biomarker detection.