NIR-guided Dendritic Nanoplatform For Reducing The Recurrence Of Tumors By Combining Chemo-Phototherapy

Phototherapy has increasingly attracted much attention on cancer treatment for its simple and efficient,high selectivity for tumor tissue,and minimal trauma to normal tissues.Phototherapy contains two major species,photodynamic therapy（PDT）and photothermal therapy（PTT）.PDT is a phototoxic therapy wherein the photosensitizer is excited with light of a specific wavelength to generate singlet oxygen（¹O₂）and other reactive oxygen species（ROS）that can produce light toxic effects.PTT takes advantage of photothermic agents to absorb certain wavelengths of light,and then transform it to heat at the tumor site,thereby killing cancer cells via hyperthermia or thermal ablation.However,single phototherapy often causes tumor recurrence thus hindered its clinical application.Therefore,a single agent-based multifunctional theranostic nanoplatform（RCPD）was developed for combinatorial phototherapy containing dual PDT and PTT therapeutic mechanisms with chemotherapy.In this study,a triplet modality dendritic nanoplatform（RCP）combined a hydrophobic cyanine dye cypate with dendrimer（PAMAM）,modified with a tumor penetration peptide iRGD was prepared to improve the hydrophility,and reduced the self-aggregation of cypate.Besides,to reduce the tumor recurrence of phototherapy,a broad-spectrum chemotherapeutic drug Docetaxel（DTX）was encapsulated into the inner space of RCP to prepare multifunctional theranostic nanoplatform（RCPD）.We mainly focused on the reactive oxygen species and heat generation of RCP to investigate its PDT and PTT effects.The generation of reactive oxygen species of RCPD（photodynamic effect）at different power densities,times and drug concentrations was measured by SOSG reagent under 808 nm near-infrared light irradiation and the temperature change（photothermal effect）was measured by thermocouple thermometer.Cytotoxicity of RCPD-mediated combination treatment of PTT/PDT and chemotherapy were assessed in HepG2 cells and DTX resistant human liver cancer cells by the MTT assay.The cellular uptake of RCPD in HepG2 tumor cells was investigated by confocal microscopy.The distribution of the RCPD in HepG2 cells was investigated by fluorescence labeling.The synergistic chemo-photo therapeutic efficacy of RCPD on HepG2 cells under 808nm NIR light was investigated by confocal microscopy and flow cytometry.At last,the synergistic chemo-photo therapeutic efficacy of RCPD was investigated in HepG2 tumor-bearing mice.The results showed that RCPD could generate enhanced singlet oxygen species compared with free cypate,as well as maintain its fluorescence intensity and heat generation ability in response to NIR laser irradiation.Furthermore,RCPD generated much stronger（².85-fold）SOSG fluorescence intensity compared with free cypate under NIR irradiation.The temperature of RCPD can rapidly reach tumor ablation temperature（42°C-45°C）within 2 mins and remain stable within 5 mins.MTT results showed the cell viability of DTX-resistant HepG2 cells incubated with RCPD（250μg/ml）was only6.61%under NIR irradiation,which indicating that RCPD has the potential to overcome multidrug resistance.In vitro lysosomal escape results indicated that RCPD can be taken up by HepG2 cells and escaped from lysosomes to exerte anti-tumor effect.In vivo anti-tumor studies showed that the anti-tumor rate of RCPD-mediated phototherapy-chemotherapy was 95.1%,which was significantly higher than that of phototherapy alone（57.2%）,and there was no obvious recurrence within 20 days.In conclusion,the combinatorial chemo-photo treatment of RCPD with the local exposure of NIR light can significantly reduce the risk of recurrence of tumors and enhance anti-tumor efficiency.This multifunctional theranostic platform can be potentially applied for NIR fluorescence image-guided combinatorial treatment of tumor cancers.