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Pharm Res. 2013 Aug;30(8):2077-86. doi: 10.1007/s11095-013-1060-1. Epub 2013 May 2.

Brushed block copolymer micelles with pH-sensitive pendant groups for controlled drug delivery.

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Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, 789 South Limestone, Lexington, Kentucky 40536-0596, USA.



To investigate the effects of small aliphatic pendent groups conjugated through an acid-sensitive linker to the core of brushed block copolymer micelles on particle properties.


The brushed block copolymers were synthesized by conjugating five types of 2-alkanone (2-butanone, 2-hexanone, 2-octanone, 2-decanone, and 2-dodecanone) through an acid-labile hydrazone linker to poly(ethylene glycol)-poly(aspartate hydrazide) block copolymers.


Only block copolymers with 2-hexanone and 2-octanone (PEG-HEX and PEG-OCT) formed micelles with a clinically relevant size (< 50 nm in diameter), low critical micelle concentration (CMC, < 20 μM), and drug entrapment yields (approximately 5 wt.%). Both micelles degraded in aqueous solutions in a pH-dependent manner, while the degradation was accelerated in an acidic condition (pH 5.0) in comparison to pH 7.4. Despite these similar properties, PEG-OCT micelles controlled the entrapment and pH-dependent release of a hydrophobic drug most efficiently, without altering particle size, shape, and stability. The molecular weight of PEG (12 kDa vs 5 kDa) induced no change in pH-controlled drug release rates of PEG-OCT micelles.


Acid-labile small aliphatic pendant groups are useful to control the entrapment and release of a hydrophobic drug physically entrapped in the core of brushed block copolymer micelles.

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