Construction And Synergistic Anti-tumor Effects Of Targeted Gold Clusters@Polymer-Fe Nanotherapeutics System

In recent years,the incidence and mortality rates of cancer have been on the rise,posing a serious threat to public health.Although traditional chemotherapy and surgical treatment are effective,the side effects such as low drug accumulation,short circulation time and easy recurrence are far from achieving the goal of radical treatment of tumors.Therefore,designing a suitable intelligent diagnosis and treatment platform that can accurately target tumor cells and reduce toxic and side effects to normal tissues remains a challenge in medical applications.Phototherapy,including photothermal therapy(PTT)and photodynamic therapy(PDT),is emerging in recent years.Due to the sufficient heat and reactive oxygen species(ROS)can generated by photosensitizer when it irradiated under the near-infrared laser,thereby eliminating tumor cells.Phototherapy has the advantages of high selectivity and low side effects compared with traditional therapies because of its non-invasive characteristics.However,the photosensitizers commonly used in the past,such as oxides,sulfides,polymers and precious metals,only had the efficacy of a single PTT or PDT,and lack imaging function to achieve real-time monitoring of tumors,which often failed to achieve satisfactory results.Moreover,the efficacy of PDT is severely limited to the tumor hypoxic microenvironment.In addition,the tumor microenvironment(TME),including hypoxia,over-expression of H₂O₂and glutathione(GSH)levels,also seriously hinders the therapeutic effect of tumor cells.Using this TME,metal ions such as Fe can consume GSH and further produce hydroxyl radical(·OH)with H₂O₂ through Fenton or Fenton-like reaction to achieve chemistrydynamic therapy(CDT)with less side effects.However,this is still the problems and challenges to develop multifunctional photosensitizers which combined CDT and laser therapy in the above-mentioned therapy process.Based on this,in this paper,two polymercaptoaniline(POMA)or hemoglobin(Hb)nanocomposites with gold nanoclusters(AuNCs)as the core that were sensitive to laser and TME were synthesized,which not only improved the tumor microenvironment,but also had the enhanced combination therapy of PTT/PDT/CDT,and could also play the function of near-infrared thermal imaging(IR imaging)for the monitoring of tumor sites.The main research results of this paper were as follows:1.Using o-mercaptoaniline(OMA)as ligand and reducing agent,HAuCl₄ and Fe³⁺as oxidants,AuNCs/polymercaptoaniline(POMA)-Fe nanocomposites,which was sensitive to laser and tumor microenvironment,was successfully prepared in situ by a simple one-step method.Then,it was connected with the targeting molecule folic acid(FA)through amidation reaction to synthesize a uniformly distributed spherical targeted AuNCs@POMA-Fe-FA nanoplatform with a particle size of 60 nm.The research results showed that the existence of POMA not only broadened the laser absorption of the nanoplatform to the near-infrared region,but also had excellent PTT performance.The AuNCs in the system had both photothermal and photodynamic effects.On the one hand,they cooperate with POMA to exert excellent PTT performance,the temperature of the dispersion of the nanoplatform could increase by 18.8°C under 808 nm laser irradiation.On the other hand,the nanoplatform contained both Fe³⁺and Fe²⁺,among which Fe³⁺could catalyze the decomposition of H₂O₂ to produce oxygen and consume the over-expressed GSH in the tumor,thus improving the hypoxic microenvironment of the tumor,thereby enhancing the PDT performance of AuNCs.The Fe²⁺formed by the reaction and the original Fe²⁺further react with the excess H₂O₂ to produce·OH and play the role of CDT.In vitro experimental results proved that the targeted nanoplatform could be specifically recognized and taken up effectively by tumor cells.After irradiation with 808 nm laser for 10 min,the killing rate of HepG2 cells reached 72%,demonstrating an excellent synergistic antitumor ability of PTT/PDT/CDT.In vivo experimental results showed that the tumor inhibition rate of mice injected with the nanoplatform reached 84%after 12 days of laser irradiation treatment.The nanoplatform also demonstrated the function of near-infrared photothermal(IR)imaging,which realized the role of PTT/PDT/CDT mediated by the diagnosis and monitoring of the tumor site.Therefore,this kind of laser-sensitive and TME-sensitive synergistic anti-tumor nanoplatform had great application potential.2.Using biocompatible hemoglobin(Hb)as ligand and reducing agent,HAuCl₄ as oxidizing agent,AuNCs@methemoglobin(MHb)nanocomposite were prepared by a green one-step process.Fe²⁺supplied by Hb was oxidized to Fe³⁺in an alkaline environment to form MHb,and finally a new type of AuNCs@MHb-TPP nanocomposite was synthesized by modifying the mitochondrial targeting molecule triphenylphosphine(TPP).The nanocomposite was a spherical particle,and had multiple functions of mitochondrial targeting and sensitivity to laser and TME.Laser-sensitive experiments showed that AuNCs had both photothermal and photodynamic functions,the temperature of the system could increase by18.5°C under 808 nm laser irradiation,and a large amount of ¹O₂ was produced,which showed that the nanoplatform had excellent PTT,PDT and IR imaging performance.TME sensitivity experiments confirmed that Fe³⁺could be dissolved from the AuNCs@MHb-TPP in weak acidic microenvironment,and then catalyzed H₂O₂ to produce oxygen to improve the hypoxic microenvironment of tumors,thus greatly enhancing the efficacy of PDT.In addition,Fe³⁺could also consume over-expressed GSH to produce Fe²⁺and further react with excess H₂O₂ to exert CDT efficacy.In vitro experimental results showed that the nanoplatform could target the mitochondria of tumor cells,and the killing rate of HepG2 cells reached about 70%after irradiation with 808 nm laser for 10 min,showing excellent synergistic antitumor ability of PTT/PDT/CDT.In vivo experiments results demonstrated that the tumor growth inhibition rate reached 80%on the 12th day after laser irradiation of the nanoplatform,and the illuminated nanoplatform could also perform the function of IR imaging to monitor the location of solid tumors.Therefore,this was a targeted diagnosis and treatment nanoplatform that could catalyze oxygen production in situ and integrate imaging and collaborative therapy,which provided important reference value for the design of a novel multifunctional diagnosis and treatment platform for anti-tumor research.