Synergistic Treatment Of Squamous Cell Carcinoma With Polydopamine And MnO₂-modified Paclitaxel Carbon Dots

BACKGROUND:Oral squamous cell carcinoma（OSCC）is one of the most common type of head and neck cancer reported worldwide,and is known as"oral cancer".Chemotherapy is one of the three major treatments for malignant tumors,but most chemotherapeutic drugs have poor targeting,serious adverse effects,and low therapeutic index,etc.The use of nanocarrier technology to improve the delivery of antitumor drugs is an effective strategy to enhance the efficacy of chemotherapy.Paclitaxel（PTX）,one of the most common drugs for the treatment of head and neck cancer,often uses polyoxyethylene castor oil（Cremophor EL）and ethanol as excipients to overcome the problem of low solubility when used parenterally due to its extremely low water solubility and poor bioavailability.However,polyoxyethylene castor oil is not harmless and is often associated with severe allergy-like hypersensitivity reactions,hyperlipidemia,lipoprotein abnormalities,erythrocyte aggregation,and peripheral neuropathy.Therefore,the design of new carbon-based nanomaterials based on PTX to improve their water solubility,bioavailability and targeting is of great clinical significance and practical value.OBJECTIVES:In this study,PTX was used as the core carbon source to synthesize PTX-derived carbon dots（Paclitaxel carbon dots,PCDs）by a one-step hydrothermal method.The synthesized PCDs not only retain some of the tumor-killing properties,but also have excellent water solubility and biosafety,which eliminates the need to add surfactants such as polyoxyethylene castor oil during antitumor application.This greatly improves the safety and reduces the burden on patients.By modifying PCDs with polydopamine and Mn O₂,the PCDs nanocomplexes obtained the photothermal properties of polydopamine and the controlled release properties of tumor microenvironment.The synthesized novel nanoparticles possess the advantages of high biocompatibility,high targeting,low side effects and combination of multiple tumor treatment strategies at the same time,addressing the shortcomings of existing clinical paclitaxel formulations.METHODS:PCDs were synthesized by one-step hydrothermal method,and the physical properties of PCDs were characterized by transmission electron microscope（TEM）,zeta potential and particle size analyzer,UV-Vis spectrophotometer and fluorescence spectrophotometer,and placed in different p H solutions and under sunlight irradiation for a long time,respectively.The p H stability and long-term storage stability of PCDs were observed,and the biocompatibility and anti-tumor properties of PCDs were examined by CCK8 method using L929 cells and Cal-27cells,respectively.The PCDs were modified by polymerizing dopamine under alkaline conditions and synthesizing Mn O₂on the surface of PCDs by ultrasonic reduction.The morphology and size of the PCDs nanocomplexes were observed by TEM,and their release in response to the tumor microenvironment was studied by simulating the tumor microenvironment with high glutathione（GSH）and low p H.The photothermal properties were studied by measuring their temperature by infrared observer under the irradiation of 808 nm laser.Finally,Cal-27 cells were used as a model to study the tumor killing effect of different concentrations of PCDs,PCDs@PDA@Mn O₂and PCDs@PDA@Mn O₂+NIR,respectively.RESULTS:TEM showed that the PCDs were uniformly dispersed in anhydrous ethanol solution without obvious agglomeration,and the size distribution was relatively consistent with an average particle size of 2.25 nm.The zeta potential analyzer showed that the zeta potential of PCDs was+27.21 m V,and the characteristic absorption peak of PCDs was 353 nm,while PCDs could obtain the best excitation at 360 nm laser,and their excitation light was PCDs maintain a strong luminescence stability in the range of p H=3 to p H=9,and the luminescence efficiency does not change significantly when they are subjected to natural light irradiation for a long time.When larger concentrations of PCDs were applied（100μg/m L）,mouse epithelial-like fibroblasts L929 still possessed strong cellular activity（more than 80%）;when different concentrations of PTX and PCDs were applied to human tongue squamous carcinoma cells Cal-27,respectively,PCDs could achieve 55%-60%of the antitumor effect of PTX.PCDs@PDA@MnO₂was synthesized based on PCDs,and the morphology of PCDs@PDA@Mn O₂was observed by TEM.PCDs@PDA@Mn O₂showed a uniform spherical shape,and an obvious bilayer shell structure could be observed,the first inner shell layer was PDA,and the second outer shell layer was Mn O₂.The warming efficiency of PCDs@PDA aqueous solution under 808 nm laser irradiation increased with the increase of PCDs@PDA concentration,and the highest warming efficiency was achieved at 0.5 mg/m L of PCDs@PDA aqueous solution;multiple cycles of cyclic warming experiments demonstrated the good photothermal stability of PCDs@PDA.The irradiated environment responded multiply to release the PCDs@PDA within the shell layer for the next photothermal treatment.The anti-tumor activity of the PCDs@PDA@Mn O₂group was significantly enhanced compared to the PCDs group,and the tumor-killing effect of the PCDs@PDA@Mn O₂+NIR group was further enhanced under 808 nm laser irradiation.CONCLUSION:In this study,paclitaxel-derived PCDs were synthesized by a one-step hydrothermal method using PTX as the core carbon source,which possesses extremely good water solubility and biosafety,and retains some anti-tumor activity.The PCDs@PDA@Mn O₂synthesized based on PCDs can respond to the tumor microenvironment and NIR laser irradiation in multiple ways,thus targeting the release of PCDs@PDA within the shell layer in the tumor region,and the PCDs@PDA within the shell layer can kill the tumor with photothermal therapy under808 nm laser excitation,while releasing PCDs with antitumor activity.this study demonstrated that combining PTX,a traditional antitumor drug with pharmacological activity,with nanoscience and technology,and combining chemotherapy with photothermal therapy is an effective therapeutic strategy that can significantly increase the killing effect on tongue squamous cancer cells,enhance targeting and reduce side effects,with important clinical significance and practical value.