Preparation Of Multifunctional Nano-probe Based On Ag₂S And Its Application In Tumor Diagnosis And Treatment

The rising incidence and high fatality rate have made malignant tumors to be one of the major disease that seriously endangers human life.With the development of nanotechnology,more and more nanomaterials have been widely used in the early diagnosis and non-invasive treatment of diseases,especially tumors.Silver sulfide（Ag₂S）has attracted more and more attention in the research of tumor diagnosis because of its near-infrared two region fluorescence.However,a single diagnosis mode often has some limitations.At the same time,the multi-functional nano platform under the guidance of imaging has a good application prospect in the early diagnosis and treatment of tumors.Therefore,the integration of diagnosis and treatment based on Ag₂S and the further optimization of tumor treatment effect are worthy of further exploration.In this aticle,multifunctional nanoprobe based on Ag₂S was designed and synthesized.The application of Ag₂S in tumor diagnosis and treatments were explored and optimized by modifying targeting molecules on the surface of Ag₂S and using other functional nanomaterials to interact with Ag₂S,the main research contents are as follows:（1）Polyethylene glycol phospholipid(DSPE-PEG₂₀₀₀)which modified folic acid（FA）was used to encapsulate hydrophobic nano Ag₂S to synthesize Ag₂S@DSPE-PEG₂₀₀₀-FA（Ag₂S@DP-FA）probe.The hydrated particle size of Ag₂S@DP-FA is about 200 nm,which has a good dispersibility and stability.When the concentration of probe up to 50μg/m L（Ag concentration）,it still had low cytotoxicity.In vitro and in vivo cross-contrast imaging proved the multi-mode imaging of Ag₂S@DP-FA probe and its active targeting ability to tumors with high folate receptor expression.The targeting of the probe can make the probe more and faster enriched at the tumor site,thereby improving the therapeutic efficacy of the probe and reducing the amount of probe.In vivo and in vitro photothermal therapy experiments confirmed that the probe has good photothermal treatment capabilities.In general,the Ag₂S@DP-FA probe has good targeted dual-mode imaging and photothermal therapy capabilities,and its targeting ability improves the enrichment efficiency of the probe at the tumor site and optimizes its effect in tumor diagnosis and treatments.（2）Ag₂S/Au@DSPE-PEG₂₀₀₀（ASAuDP）composite probe with good stability and dispersibility was synthesized by encapsulated hydrophobic nano Ag₂S and ultra-small nano Au particles（particle size 3～5 nm）with phospholipid.The hydrated particle size of the ASAuDP probe is about 150 nm,and it has the properties and functions of Ag₂S and ultra-small nano-Au particles.The m Au in the ASAuDP probe can significantly inhibit the fluorescence（FL）of Ag₂S,thereby reducing the phototoxicity of probe when circulating in the body.When the ASAuDP probe was phagocytosed by tumor cell,Ag₂S and m Au are separated with the rupture of the probe,thereby restoring the ability of FL imaging and ROS production.MTT test,blood analysis and organ pathology test prove that ASAuDP is a safe probe.In vitro and in vivo imaging experiments prove that the ASAuDP probe has good FL,CT and photoacoustic（PA）imaging capabilities.In vitro and in vivo treatment prove that the ASAuDP probe has both photothermal and sonodynamic therapeutic abilities,and the synergy between them has the best therapeutic effect.Therefore,ASAuDP probe is a kind of integrated diagnostic and therapeutic probe with good safety,and it has a good application prospect in the treatment of tumors.In summary,ultra-small nano-Au particles solves the phototoxicity problem of Ag₂S during systemic circulation;CT imaging of Au makes up the limited penetration depth of fluorescence imaging;the synergy of sonodynamic therapy and photothermal therapy optimizes the treatment.（3）A hollow Ag₂S/Ag nanocomposite shell containing both elemental silver（Ag）and compound silver sulfide（Ag₂S）was synthesized by a template method,after loading the sonosensitizer chlorin e6（Ce6）and the CT contrast agent iohexol（I）,a multifunctional hollow Ag₂S/Ag@I/Ce6（HASAIC）nanocomposite probe was obtained by wrapping it with a temperature-sensitive phospholipid.At the same time,the hollow Ag₂S/Ag nanocomposite shell structure avoids the major drawbacks of the gradual dissolution of the pure silver shell during the catalytic process and the loss of photothermal treatment and photoacoustic imaging performance.This enables the probe to use stable silver sulfide to achieve photothermal therapy and photoacoustic imaging while solving the problem of hypoxia.The particle size of the probe is about 70 nm,and has a good stability.The probe’s cytotoxicity experiment,mouse biochemical index detection and tissue section experiment proved its high biocompatibility.The probe’s in vitro and in vivo experiments proved that it has good CT and PAI imaging capabilities and good tumor killing capabilities.The tumor-bearing mice injected with the probe were still alive on the 40th day after laser and ultrasound irradiation,while Ag₂S/@I/Ce6 control probe group without elemental silver had only a 40%survival rate.It proved that the elemental Ag in the composite probe significantly improves the therapeutic effect.In this chapter,the composite shell probe designed based on the special tumor microenvironment improves the hypoxic environment at the tumor site,optimizes the effect of sonodynamic therapy and provides a new idea for the design and synthesis of integrated probes for tumor diagnosis and treatment.In summary,this thesis takes Ag₂S as the cornerstone,designs and synthesizes multifunctional nanoprobe according to the limitations of the probe itself and the microenvironment of the tumor site.The modified targeting molecules and synergy between multiple materials optimize the application of a single material in the integration of tumor diagnosis and treatment,provide new ideas for the design of new nanoprobes and improve their diagnosis and treatment effect.