Reduction-responsive disassemblable core-cross-linked micelles based on poly(ethylene glycol)-b-poly(N-2-hydroxypropyl methacrylamide)-lipoic acid conjugates for triggered intracellular anticancer drug release.
ABSTRACT Reduction-sensitive reversibly core-cross-linked micelles were developed based on poly(ethylene glycol)-b-poly(N-2-hydroxypropyl methacrylamide)-lipoic acid (PEG-b-PHPMA-LA) conjugates and investigated for triggered doxorubicin (DOX) release. Water-soluble PEG-b-PHPMA block copolymers were obtained with M(n,PEG) of 5.0 kg/mol and M(n,HPMA) varying from 1.7 and 4.1 to 7.0 kg/mol by reversible addition-fragmentation chain transfer (RAFT) polymerization. The esterification of the hydroxyl groups in the PEG-b-PHPMA copolymers with lipoic acid (LA) gave amphiphilic PEG-b-PHPMA-LA conjugates with degrees of substitution (DS) of 71-86%, which formed monodispersed micelles with average sizes ranging from 85.3 to 142.5 nm, depending on PHPMA molecular weights, in phosphate buffer (PB, 10 mM, pH 7.4). These micelles were readily cross-linked with a catalytic amount of dithiothreitol (DTT). Notably, PEG-b-PHPMA(7.0k)-LA micelles displayed superior DOX loading content (21.3 wt %) and loading efficiency (90%). The in vitro release studies showed that only about 23.0% of DOX was released in 12 h from cross-linked micelles at 37 °C at a low micelle concentration of 40 μg/mL, whereas about 87.0% of DOX was released in the presence of 10 mM DTT under otherwise the same conditions. MTT assays showed that DOX-loaded core-cross-linked PEG-b-PHPMA-LA micelles exhibited high antitumor activity in HeLa and HepG2 cells with low IC(50) (half inhibitory concentration) of 6.7 and 12.8 μg DOX equiv/mL, respectively, following 48 h incubation, while blank micelles were practically nontoxic up to a tested concentration of 1.0 mg/mL. Confocal laser scanning microscope (CLSM) studies showed that DOX-loaded core-cross-linked micelles released DOX into the cell nuclei of HeLa cells in 12 h. These reduction-sensitive disassemblable core-cross-linked micelles with excellent biocompatibility, superior drug loading, high extracellular stability, and triggered intracellular drug release are promising for tumor-targeted anticancer drug delivery.
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ABSTRACT: Redox and pH dual-responsive biodegradable micelles were developed based on poly(ethylene glycol)-SS-poly(2,4,6-trimethoxybenzylidene-pentaerythritol carbonate) (PEG-SS-PTMBPEC) copolymer and investigated for intracellular doxorubicin (DOX) release. PEG-SS-PTMBPEC copolymer with an M(n) of 5.0-4.1 kg/mol formed micellar particles with an average diameter of 140 nm and a low polydispersity of 0.12. DOX was loaded into PEG-SS-PTMBPEC micelles with a decent drug loading content of 11.3 wt.%. The in vitro release studies showed that under physiological conditions only ca. 24.5 % DOX was released from DOX-loaded micelles in 21 h. The release of DOX was significantly accelerated at pH 5.0 or in the presence of 10 mM glutathione (GSH) at pH 7.4, in which 62.8 % and 74.3 % of DOX was released, respectively, in 21 h. The drug release was further boosted under 10 mM GSH and pH 5.0 conditions, with 94.2 % of DOX released in 10 h. Notably, DOX release was also facilitated by 2 or 4 h incubation at pH 5.0 and then at pH 7.4 with 10 mM GSH, which mimics the intracellular pathways of endocytosed micellar drugs. Confocal microscopy observation indicated that DOX was delivered and released into the nuclei of HeLa cells following 8 h incubation with DOX-loaded PEG-SS-PTMBPEC micelles, while DOX was mainly located in the cytoplasm for reduction-insensitive PEG-PTMBPEC controls. MTT assays revealed that DOX-loaded PEG-SS-PTMBPEC micelles had higher anti-tumor activity than reduction-insensitive controls, with low IC(50) of 0.75 and 0.60 μg/mL for HeLa and RAW 264.7 cells, respectively, following 48 h incubation. PEG-SS-PTMBPEC micelles displayed low cytotoxicity up to a concentration of 1.0 mg/mL. These redox and pH dual-bioresponsive degradable micelles have appeared as a promising platform for targeted intracellular anticancer drug release.Journal of Controlled Release 01/2013; · 7.63 Impact Factor
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ABSTRACT: In this study, we designed and developed galactose-installed photo-crosslinked pH-sensitive degradable micelles (Gal-CLM) for active targeting chemotherapy of hepatocellular carcinoma in mice. Gal-CLM was readily obtained from co-self-assembly of poly(ethylene glycol)-b-poly(mono-2,4,6-trimethoxy benzylidene-pentaerythritol carbonate- co-acryloyl carbonate) (PEG-b-P(TMBPEC-co-AC) and Gal-PEG-b-poly(ε-caprolactone) (Gal-PEG-b-PCL) copolymers followed by photo-crosslinking. Notably, paclitaxel (PTX)-loaded Gal-CLM (Gal-PTX-CLM) showed a narrow distribution (PDI=0.08-0.12) with average sizes ranging from 92.1-136.3nm depending on the Gal contents. The release of PTX from Gal-CLM while inhibited at physiological pH was enhanced under endosomal pH conditions. MTT assays in asialoglycoprotein receptor (ASGP-R) over-expressing HepG2 cells demonstrated that half-maximal inhibitory concentrations (IC50) of Gal-PTX-CLM decreased from 11.7, 2.9, to 1.1μg/mL with increasing Gal contents from 10%, 20% to 30%, supporting receptor-mediated endocytosis mechanism. The in vivo biodistribution studies in human hepatoma SMMC-7721 tumor-bearing nude mice displayed that Gal20-PTX-CLM resulted in significantly enhanced drug accumulation in the tumors over non-targeting PTX-CLM counterpart. In accordance, Gal20-PTX-CLM caused much greater tumor growth inhibition than non-targeting PTX-CLM as well as non-crosslinking Gal20-PTX-NCLM controls (average tumor volume: ca. 35mm(3)versus 144mm(3) and 130mm(3), respectively). Histological analysis showed that Gal20-PTX-CLM induced more extensive apoptosis of tumor cells while less damage to normal liver and kidney as compared to Taxol. Ligand-installed photo-crosslinked pH-responsive degradable micelles have a great potential for targeted cancer chemotherapy.Journal of controlled release : official journal of the Controlled Release Society. 05/2014;
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ABSTRACT: A novel pH and redox dual-responsive prodrug nanogel was prepared by an inverse nanoprecipitation method, which is mild and surfactant free, and based on a thiol-disulfide exchange reaction and thiol-Michael addition reaction. Highly biocompatible hyperbranched polyglycerol (hPG) was cross-linked with disulfide bonds, to obtain biodegradable nanogels, which could be degraded under intracellular reductive conditions. Doxorubicin (DOX) was conjugated to the biodegradable nanogel matrix via an acid-labile hydrazone linker. This is the first dual-responsive prodrug nanogel system that shows very low unspecific drug leaching, but efficient intracellular release of the payload triggered by the intracellular conditions. Two different prodrug nanogels were prepared with a size of approximately 150 nm, which is big enough to take the advantage of the enhanced permeation and retention (EPR) effect in tumor tissue. Cell culture analysis by microscopy and flow cytometry revealed that the prodrug nanogels were efficiently internalized by tumor cells. Distinct release profiles of DOX were achieved by adjusting the nanogel architecture, and online detection of cytotoxicity showed that, unlike free DOX, the dual-responsive prodrug nanogels exhibited a delay in the onset of toxicity, indicating the different uptake mechanism and the need for prodrug activation to induce cell death.Journal of Controlled Release 11/2013; · 7.63 Impact Factor