Biodegradable Thermogelling Hydrogel of P(CL-GL)-PEG-P(CL-GL) Triblock Copolymer: Degradation Drug Release Behavior

Degradation and drug release behavior of thermogelling hydrogel of poly(ε-caprolactone-co-glycolide)-poly(ethylene glycol)-poly(ε-caprolactone-co-glycolide) [P(CL-GL)-PEG-P(CL-GL) (1880-1540-1880)] triblock copolymer were investigated. The copolymer aqueous solution (25 wt%) underwent sol-gel transition at 35 °C as the temperature increased and formed a stable gel at body temperature. After incubation in PBS buffer solution (0.1 M) at 37 °C, the gel degraded completely into a viscous liquid at 14th week. Chemical microstructural analysis of the degraded samples by 1H-NMR revealed the degradation occurring mainly on the glycolyl sequences of the copolymer. The pH value of the gel buffer solution maintained neutral during the initial 8 weeks, which may be beneficial for the preservation of activity of pH-sensitive drugs. Incorporation of drugs into the gel was formulated at room temperature without the use of any organic solvent. The gel formed a controlled release depot with delivery times of 12, 32, and 25 days for isoniazid, rifampicin and bovine serum albumin, respectively. Controlled release of hydrophobic rifampicin was achieved with insignificant burst effect due to the distribution of the drug mainly in the hydrophobic polyester regions of the gel.