Purpose: The introduction of curcumin into clinics is hindered by its low water solubility and poor bioavailability. To overcome these limitations, we developed curcumin implants using poly (ε-caprolactone) as the polymeric matrix.
Methods: Implants were prepared by melt-extrusion method; in vitro drug release was optimized for effects of polymer composition, drug load, surface area and water-soluble additives. Implants were also tested under in vivo conditions for cumulative curcumin release, and liver concentration was correlated with its efficacy to modulate selected xenobiotic-metabolizing enzymes (CYP1A1 and GSTM).
Results: Drug release from implants followed biphasic release pattern with Higuchi kinetics and was proportional to the surface area of implants. Drug release increased proportionately from 2 to 10% (w/w) drug load, and incorporation of 10% (w/w) of water-soluble additives (F-68, PEG 8000 and cyclodextrin) did not significantly alter the drug release. In vivo drug release was found to be ~1.8 times higher than in vitro release. Curcumin was detected at 60 ± 20 ng/g in the liver after four days of implantation and was almost constant (8-15 ng/g) for up to 35 days. This time-dependent drop in curcumin level was found to be due to induction of CYP1A1 and GSTM (μ) enzymes which led to increased metabolism of curcumin.
Conclusion: Our data showed that these implants were able to release curcumin for long duration and to modulate liver phase I and phase II enzymes, demonstrating curcumin's biological efficacy delivered via this delivery system.