Characterization of poly(2-ethylacrylic acid) for use in drug delivery

Abstract

The pH-dependent conformational transition of poly(2-ethylacrylic acid) [PEAA] and its interaction with phosphotidylcholine bilayer membranes were investigated. The conformational transition was monitored with fluorescence spectroscopy using pyrene as a probe; the location and breadth of the conformational transition was shown to be dependent on the molecular weight and polydispersity of the sample, respectively. The pH-dependent destabilization and fusion of extruded large unilamellar vesicles (LWs) by PEAA was characterized by optical density measurements, transmission electron microscopy, and lipid mixing and contents release assays. Reduction of either the chain length or the polymer concentration caused the fusion and contents release events to shift to lower pH values. Release of entrapped calcein was observed at pH values ca. 1 unit higher than those found to cause membrane fusion. Decreased levels of fusion were observed when the concentration of PEAA was lower than that of the lipid; however, quantitative release of encapsulated calcein could be effected at very low polymer concentrations (-3% wlw PEAA/lipid).

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