PH-responsive PEG-b-PDPA Complex Micelles For Reversal Of Drug Resistance

Breast cancer is one of major diseases which are harmful to female’s health so far.Chemotherapy is the important means for successful therapy of breast cancer,but facing the challenge of multidrug resistance(MDR),which leading to clinical treatment failure.In order to enhance the chemotherapy efficacy,the researchers have developed several strategies.For example,they combined drugs with biologically active ingredients like anti-resistance gene or combined chemotherapy with other therapy methods.Among of them,the functional drug delivery systems which could reverse MDR of cancer had been focused on,especially.In this study,we synthetized a pH-sensitive conjugate,PEG-block-poly(di-iso-propyl-amine-ethyl-methacrylate)(PEG-b-PDPA)and then prepared DOX-loaded TPGS/PEG-b-PDPA complex micelles(DOX@TPPMs).Its ability of reversing MDR of breast cancer was evaluated in vitro and in vivo.We combined with the photothermal materials to prepare Pluronic123-DOX/PEG-b-PDPA-Cypate complex micelles(P-DOX/P-Cypate),and its application in the therapy of breast MDR cancer in vitro and in vivo was also investigated.The main results were as follows:(1)The pH-sensitive PEG-b-PDPA conjugate was synthetized by the atom transfer radical polymerization reaction.The 1H NMR spectrum of PEG-b-PDPA proved that the structure was PEG114-b-PDPA10.DOX-loaded complex micelles(DOX@TPPMs)were prepared by combining PEG114-b-PDPA10 with TPGS,and the resulting micelles had pH sensitivity.The pH sensitivity was decreased by the addition of TPGS.The size of TPPMs was uniform at pH=7.4,but disintegrated at pH=6.0.The faster and effective release behavior of DOX@TPPMs was observed in the acidic environment which was mimic to tumor microenvironment.(2)The cellular uptake,the intracellular distribution and the cytotoxicity of DOX@TPPMs were investigated in human breast cancer MCF7 cells and MCF7/ADR resistant cells.The mechanism of reversing MDR of breast cancer was further investigated by evaluating the apoptosis and cell cycle of MCF7/ADR resistant cells under the treatment of DOX@ TPPMs.The cellular experimental results showed that DOX@TPPMs could increase the distribution of DOX in MCF7/ADR resistant cells,especially induce more DOX into nuclei.The enhanced apoptosis and cell cycle arrest were observed in MCF7/ADR cells.This phenomenon resulted in more cytotoxicity.In MCF7/ADR bearing mice,we evaluated the anti-cancer efficacy of DOX@TPPMs and the mechanism of reversing MDR.The in vivo pharmacokinetics results showed that DOX@TPPMs had long circulation time in blood and were accumulation in tumor.The anti-tumor efficacy in nude mice bearing MCF7/ADR tumor showed DOX@TPPMs was more effective while leading to less toxicity to heart than DOX.(3)To increase the cytotoxicity of DOX to MCF7/ADR resistant cells,the pH-and light-responsive PEG-b-PDPA-Cypate conjugate(P-Cypate)was first synthetized by conjugating Cypate to pH-sensitive PEG-b-PDPA conjugate.Dual-functional complex micelles(P-DOX/P-Cypate)consisting of P-Cypate and Pluronic123-DOX(P-DOX)were then prepared.The P-DOX/P-Cypate micelles can generate heat at 808 nm laser,which resulting in the increase of temperature.The increase of temperature had the positive correlation with the concentration of micelles or the power of laser.(4)The in vitro experimental results showed that the cellular uptake of DOX was increased by addition of P-DOX/P-Cypate,resulting in the enhancement of cytotoxicity.The P-DOX/P-Cypate produced significant photothermal effect at 808 nm laser after ingested into MCF7/ADR cells.The in vivo experimental results showed that the P-DOX/P-Cypate had the long circulation time in blood,and effectively accumulated in tumor.The in vivo anti-tumor efficacy on nude mice bearing MCF7/ADR tumor showed that P-DOX/P-Cypate was more effective than DOX by combining with the photothermal therapy.P-DOX/P-Cypate reduced the toxicity to heart and had non-toxicity to the other organs.As a result,the dual-functional complex micelles based on pH-sensitive PEG-b-PDPA conjugate could be an effective and safe candidate for therapy of breast MDR cancer,which can provide a new insight for reversing MDR of breast cancer.