High loading of gentamicin in bioadhesive PVM/MA nanostructured microparticles using compressed carbon-dioxide.

To investigate, for the first time, the viability of compressed antisolvent methodologies for the preparation of drug-loaded particles of the biodegradable and bioadhesive polymer poly (methyl vinyl ether-co-maleic anhydride) (PVM/MA), utilizing gentamicin (Gm) as a model drug. Precipitation with a Compressed Antisolvent (PCA) method was used for the preparation of PVM/MA particles loaded with gentamicin. Before encapsulation, gentamicin was modified into a hydrophobic complex, GmAOT, by exchanging its sulphate ions with an anionic surfactant. GmAOT:PVM/MA composites were fully characterized in terms of size, morphology, composition, drug distribution, phase composition, in vitro activity and drug release. Homogeneous nanostructured microparticles of PVM/MA loaded with high and uniformly distributed quantities of GmAOT were obtained by PCA. The drug loading factors could be tuned at will, improving up to ten times the loadings obtained by other precipitation techniques. Gentamicin retained its bioactivity after being processed, and, according to its release profiles, after an initial burst it experienced a sustained release over 30 days. Compressed antisolvent methods are suitable technologies for the one-step preparation of highly loaded nanostructured PVM/MA matrices with promising application in the delivery of low bioavailable drugs.