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.
- SourceAvailable from: Magdalena Maksymiak[show abstract] [hide abstract]
ABSTRACT: RATIONALE: Currently, most of the antioxidants and free radical neutralizers used in cosmetic compositions are absorbed quickly into deeper layers of skin, and then carried away by the blood stream. It would be beneficial to delay the penetration of antioxidants to the deeper layers of skin to control their delivery and release. METHODS: Recently, growing attention has been paid to the attachment of cosmetics to specific polymer carriers. Biodegradable and biocompatible conjugates of oligo-3-hydroxybutyrate with lipoic acid were obtained via the anionic ring-opening oligomerization of (R,S)-β-butyrolactone initiated by lipoic acid potassium salt. The structure of the resulting conjugates as well as their water-soluble hydrolytic degradation products were established at the molecular level by electrospray ionization mass spectrometry (ESI-MS(n) ) supported by (1) H NMR analyses. RESULTS: The structural studies, performed with the aid of ESI-MS(n) , confirmed that the lipoic acid was covalently bound to oligo-3-hydroxybutyrate chains through hydrolyzable ester bonds. Furthermore, hydrolytic degradation studies of the bioconjugates provided detailed insight into the hydrolysis process, allowing the identification of the degradation products and confirming the release of α-lipoic acid. Cytotoxicity tests demonstrated that the conjugates were non-toxic. CONCLUSIONS: Detailed molecular structural studies of new polymeric delivery systems of lipoic acid were performed by ESI-MS. ESI-MS proved to be an excellent technique for the evaluation of hydrolytic degradation products of the conjugates and for monitoring the release of lipoic acid. The results obtained contribute significantly to the characterization of biocompatible LA-OHB conjugates with potential applications in cosmetology. Copyright © 2013 John Wiley & Sons, Ltd.Rapid Communications in Mass Spectrometry 04/2013; 27(7):773-783. · 2.51 Impact Factor