Acid-cleavable polymeric core-shell particles for delivery of hydrophobic drugs

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Journal Article
Journal of Controlled Release, 2006, 115 (2), pp. 197 - 207
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Here we describe the combined use of acid-labile microgel approach and RAFT-mediated seeded despersion polymerisation technique to prepare an acid-cleavable core-shell like polymeric colloidal system for the delivery of hydrophobic drugs at slightly acidic sites. A new bisacrylate acetal crosslinker was copolymerised with n-butyl acrylate (BA) in the presence of a RAFT agent using a dispersion polymerisation technique, which yieled crosslinked spherical particles with the size ranging between 150 and 500 nm. The particles were cleaved in a pH-dependent manner similar to the acid-labile hydrolysis behaviour of the crosslinker. In order to mask the hydrophobic surface of the particles, polyethelene glycol acrylate (PEG-A) was grafted onto poly(BA) seed particles via the RAFT agent groups on the particle surface. The acidic-site selective delivery protential of the poly(BA)-g-poly(PEG-A) particles was assessed in-vitro using a lipophilic flueorescent dye as a model hydrophobic drug. Ca. 73% and 34% of the total dye loaded in the paerticles was found to be released at pH 5.0 and 7.4 in 24h, respectively. Thegrowth of human neuroblastoma cells was not affected by the incubation with the core-shell particles and their cleavage by-products upto 3 mg/ml concentration. The physiocochemical and the functional features support the potential value of the acid-cleavable poly(BA) core-poly(PEG-A) shell particles as carriers for the delivery of hydrophobic drugs at acidic sites.
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