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Updated: Jun 10, 2026
Multi-Scale Modification of Metallic Implants With Pore Gradients, Polyelectrolytes and Their Indirect Monitoring In vivo
Published on: July 1, 2013
Preparation, characterization and in vivo pharmacodynamic evaluation of thymopentin loaded poly(lactide
Gang Wei1, Liang Jin, Lingjie Xu
1School of Pharmacy, Fudan University, Shanghai 201203, PR China.
To avoid the clinical inconvenience of repeated injection of the immune modulator thymopentin (TP5), biodegradable implants comprising a mixed polymer matrix of poly(lactide acid) (PLA) and poly(lactide-co-glycolide acid) (PLGA) were produced using a simple extrusion method. Drug release from these TP5-loaded implants was characterized both in vitro and in vivo. Pharmacodynamic studies were carried out in immunosuppressed rats using the ratio of CD4(+)/CD8(+) cells, determined by flow cytometry, as an index of immunity. The results indicated that the entrapment efficiency of the implants was greater than 98%, but the release rate of TP5 depended on the drug loading. Implants containing less than 10% TP5 showed consistent release over 30 days, with low burst-release both in vitro and in vivo. Improved immunity and survival rates were observed in rats treated by TP5 injection and in rats given middle-to-high dose implants. When the release of TP5 exceeded 0.1 mg/kg body weight/day the CD4(+)/CD8(+) ratios increased in the 3 weeks after implantation, reaching a maximum (91.6% of the normal level) by the end of the third week. The TP5-loaded implants presented here provide a promising alternative to injections and the results support the further development of controlled-release TP5 formulations.
To avoid the clinical inconvenience of repeated injection of the immune modulator thymopentin (TP5), biodegradable implants comprising a mixed polymer matrix of poly(lactide acid) (PLA) and poly(lactide-co-glycolide acid) (PLGA) were produced using a simple extrusion method. Drug release from these TP5-loaded implants was characterized both in vitro and in vivo. Pharmacodynamic studies were carried out in immunosuppressed rats using the ratio of CD4(+)/CD8(+) cells, determined by flow cytometry, as an index of immunity. The results indicated that the entrapment efficiency of the implants was greater than 98%, but the release rate of TP5 depended on the drug loading. Implants containing less than 10% TP5 showed consistent release over 30 days, with low burst-release both in vitro and in vivo. Improved immunity and survival rates were observed in rats treated by TP5 injection and in rats given middle-to-high dose implants. When the release of TP5 exceeded 0.1 mg/kg body weight/day the CD4(+)/CD8(+) ratios increased in the 3 weeks after implantation, reaching a maximum (91.6% of the normal level) by the end of the third week. The TP5-loaded implants presented here provide a promising alternative to injections and the results support the further development of controlled-release TP5 formulations.
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