Antonio Martinez-Richa - Hydrolytic degradation of poly(-caprolactone) with different end groups and poly(ε-caprolactone-co-γ-butyrolactone). Characterization and kinetics of hydrocortisone delivery.

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      Polymers for   Advanced Technologies, 22 4 430-436 (2011)


      Asymmetric telechelic α-hydroxyl-ω-(carboxylic   acid)-poly(ε-caprolactone) (HA-PCL), α-hydroxyl-ω-(benzylic   ester)-poly(ε-caprolactone) (HBz-PCL) and an asymmetric   telechelic copolymer α-hydroxyl-ω-(carboxylic   acid)-poly(ε-caprolactone-co-γ-butyrolactone) (HA-PCB) were   synthesized by ring-opening polymerization of ε-caprolactone   (CL). CL and CL/γ-butyrolactone mixture were used to obtain   homopolymers and copolymer respectively at 150°C and 2 h using   ammonium decamolybdate (NH4)   [Mo10O34] (Dec) as catalyst. Water (HA-PCL   and HA-PCB) or benzyl alcohol (HBz-PCL) were used as initiators.   The three polylactones reached initial molecular weights between   2000-3000 Da measured by proton nuclear magnetic resonance   (1H-NMR). Compression-molded polylactone caplets were   allowed to degrade in 0.5 M aqueous p-toluenesulfonic   acid at 37°C and monitored up to 60 days for weight loss   behavior. Data showed that the copolymer degraded faster than the   PCL homopolymers, and that there was not difference in the weight   loss behavior between HA-PCL and HBz-PCL. Caplets of the three   polylactones containing 1% (w/w) hydrocortisone were placed in   two different buffer systems, pH 5.0 with citrate buffer and pH   7.4 with phosphate buffer at 37°C, and monitored up to 50 days   for their release behavior. The release profiles of   hydrocortisone presented two stages. The introduction of a second   monomer in the polymer chain significantly increased the release   rate, being the degradation rate for HA-PCB faster than those for   HBz-PCL and HA-PCL. At the pH studied, only slight differences on   the liberation profiles were observed. SEM micrographs indicate   that hydrolytic degradation occurred mainly by a surface erosion   mechanism.

      Key words: ε-caprolactone, γ-butyrolactone,   hydrolytic degradation, hydrocortisone, drug-delivery systems

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