Effects of amphiphilic chitosan-g-poly(ε-caprolactone) polymer additives on paclitaxel release from drug eluting implants

• The improvement of bulk hydrophilicity better accelerated drug release.
• The higher weight ratio of CP implants had, the faster the drug released.
• The shorter PCL chain in CP graft coploymers, the faster the drug released.
• The optimum additive amount was 25% with CP9.
• Drug release profile conformed to controllable Fick diffusional release mechanism.

Bioresorbable polymer stents have been proposed as promising medical implants to avoid long-term safety concerns and other potential issues caused by traditional materials. As an important member, poly(ε-caprolactone) (PCL) was used as the implant matrix with different drug loadings. To better regulate drug release rate, the hydrophilicity of PCL was adjusted by addition of amphiphilic graft copolymers, chitosan-g-poly(ε-caprolactone) (CP). The in vitro release results indicated that the improvement of bulk hydrophilicity could accelerate drug release better than that of surface coating. The optimum additive amount was 25% with CP9. Further study showed that the effect of aspirin molecules displayed no obvious difference to that of CP macromolecules on drug release rate. Moreover, these release profiles were fitted with mathematical models. The similarities were evaluated with similarity factors. Scanning electron microscopy (SEM) images displayed surface/cross-section morphologies of pure PCL and modified implants before and after release.

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