Multifunctional drug-loaded micelles encapsulated in thermo-sensitive hydrogel for in vivo local cancer treatment: Synergistic effects of anti-vascular and immuno-chemotherapy

Localized cancer therapy with combination of drugs is an effective treatment modality which increase inhibition of tumor growth and reoccurrence. Recently, hydrogels that can encapsulate more than one drug for local sustain releases have been emerging as a compelling choice. In this study, DOX-loaded DMXAA conjugated mPEG-PLGA micelle (DOX-mPPD) was encapsulated in thermosensitive hydrogel prepared by blending carboxylic and amine terminal PDLLA-PEG-PDLLA copolymers and locally injected into tumor-bearing mice to assess the synergistic anti-vascular and immuno-chemotheraputic effects of DMXAA and DOX. The successful synthesis of the copolymers was confirmed by 1HNMR, APC, DOSY and UV spectroscopies. DOX loading capacity of mPPD micelle was relatively higher (6.79%) than mPEG-PLGA (mPP) micelle (6.09%). The cumulative releases of DOX and DMXAA from mPPD micelle at pH 5.5 were 77.34 ± 2.23% and 23.12 ± 0.9%, respectively upon 120 h. The release of DOX and DMXAA from the hydrogel was occurred in a sustained and sequential fashion with a cumulative release of 60.27 ± 87% and 44.55 ± 0.23%, respectively for 40 days. The in vitro cytotoxicity test against MDCK and HeLa cells verified the biocompatibilities of the copolymers for in vivo applications. More importantly, after a single intratumoral injection of various drug formulations into tumor bearing nude mice, hydrogel loaded with DOX-mPPD displayed the highest tumor suppression efficacy, lowest tumoral micro vessel density and increased serum TNF-α and IFN-β upon five weeks. Furthermore, histological analysis of major organs and body weight changes indicated that hydrogel based localized treatments didn't cause significant systemic toxicities. Therefore, localized co-delivery of DOX and DMXAA with sequential release using hydrogels may be a promising approach for synergistic tumor suppression with minimal adverse effects.