Multimodal Micelles For Treatment Of Resistant Tumor

Objective: Chemotherapy is one of the most commonly used methods in the clinical treatment of tumors. However, chemotherapeutic drugs frequently encounter multiple drug resistance, resulting in poor therapeutic efficacy. Cisplatin is frequently applied chemotherapeutic drug with broad-spectrum anticancer properties, but often leads to drug resistance. Photothermal therapy(PTT) as an emerging strategy can achieve efficient local tumor ablation through cell necrosis triggered by photoirradiating exogenous photo-absorbing agents such as near-infrared(NIR) cyanine dyes(e.g. indocyanine green and its derivate Cypate). More importantly, hyperthermia generated by PTT is probably able to reduce the resistance of tumor cells via inducing intracellular protein denaturation, DNA repair inhibition, and disturbance of intracellular signaling pathways. Therefore, the rationally designed multi-mode micelles loaded with cisplatin prodrug and Cypate were constructed in this study. The micelles could accumulate in the tumors via enhanced permeation and retention(EPR) effect, and achieve synergistic photothermal/chemotherapeutic efficacy to overcome cisplatin resistance for efficient ablation of cisplatin-resistant tumor.Methods:(1) The prodrug of cisplatin,(c,t,c-[Pt(NH3)2(CO2CH2CH2CH2CH2CH3)2 Cl2], Pt(IV)) was synthesized using c,t,c-[Pt(NH3)2Cl2(OH)2] and hexanoic anhydride.(2) The Pt(IV)/Cypate-loaded micelles(P/C-Micelles) were prepared using the block copolymers of polyethylene glycol-polyaspartic acid(PEG-PAsp) through an optimized rotary evaporation method. The morphology was characterized using scanning electron microscopy and transmission electron microscopy. The drug loading capacity and encapsulation efficiency were measured using UV-vis spectrophotometry.(3) MTT Assay was used to evaluate the photothermal cytotoxicity of P/C-Micelles against both A549 cells and A549 R cells.(4) In vitro cellular uptakes of P/C-Micelles were measured using a UV-vis spectrometer and ICP-MS.(5) 1, 3-diphenylisobenzofuran(DPBF), Acridine Orange(AO), and Dihydroethidium(DHE) were used to monitor the generation of singlet oxygen from Cyapte in P/C-Micelles under NIR light irradiation.(6) IVIS Lumina II imaging system was used to evaluate the targeting capability of P/C-Micelles on the mice bearing A549 and A549 R tumor.(7) The in vivo anti-tumor synergistic efficacy of P/C-Micelles was evaluated in mice bearing A549 and A549 R tumor.Results: The prodrug of cisplatin, Pt(IV) was synthesized at a high yield of 85%, and exhibited the increased hydrophobility and stability. P/C-Micelles had the spherical morphology, and average diameter of 81.6 ± 5.1 nm. and drug loading efficiency of 20.3 ± 3.1%. P/C-Micelles could achieve efficient photothermal effect under NIR photoirradiating(785 nm, 1.5 W/cm2) at the concentration of 2.0 μg/m L Cypate, and the temperature was increased by 23 oC during 300 s irradiation. The in vitro experiments showed that singlet oxygen was generated from Cypate within P/C-Micelles at a low Cypate concentration under irradiation, and further disrupted the lysosomal membranes and triggered subsequent intracellular drug translocation. Under NIR irradiation, P/C-Micelles generated remarkable synergistic effect between photothermal damage and chemotherapeutic cytotoxicity against A549 and A549 R cells. Moreover, P/C-Micelles exhibited significant inhibition effect on the A549 and A549 R tumors under NIR irradiation(785 nm, 1.5 W/cm2), leading to efficient tumor ablation through synergistic chemotherapy and photothermal therapy.Conclusions: In this study, we prepared the Pt(IV)/Cypate-loaded micelles(P/C-Micelles), which were found to possess good photostability and photothermal effect, resulting in the enhanced cytotoxicity against both A549 and A549 R tumor cells uder NIR irradiation. P/C-Micelles exhibited efficient tumor accumulation via EPR effect, and further achieved remarkable tumor ablation of A549 and A549 R tumors through synergistic chemotherapy and photothermal therapy. Our strategy provides a synergistic strategy to overcome the resistance of tumor cells to cisplatin, which has a great potential for the treatment of resistant tumors in the field of cancer therapy.