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Objective To establish an accelerated method that has good correlations with in vivo release data for formulation optimization and quality control purposes of thymopentin-loaded poly(DL-lactide-co-glycolide)(PLGA)microspheres. Methods In vivo thymopentin release from the microspheres was studied in Sprague-Dawley rats and relevant cumulative release curves were plotted. Key factors including release medium types,ethanol concentrations,surfactant concentrations and heating temperature were investigated for the in vitro accelerated release. The conditions for accelerated release were optimized to make the accelerated release cures fit the in vivo release well. The final optimized accelerated release method was validated in other two formulations. Results The final optimized accelerated release conditions were: 20% hydro-alcoholic solutions (V/V)and 0.06% Tween 80 (W/V)as the release media,gradient heating program (0-1 h at 40 °C,1-6 h at 45 °C and 6-30 h at 50 °C)as the media heating method. After fitted with the in vivo release curves,the correlation constant r2 of (8,13 and 28)×103 PLGA microspheres was 0.9783,0.9886 and 0.9780,respectively. Conclusion By introducing alcohol into the release media and applying gradient heating program,the reported accelerated method can be used in the formulation optimization and quality control of thymopentin-loaded PLGA microspheres.
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One of the most challenging issues in the delivery of therapeutic proteins from PLGA-based microparticles is the stability and complete release of the protein in its native form. This review summarizes the methods to promote the stability and in vitro release of protein from PLGA-based microparticles. Protein stability is the precondition of complete release. One way to keep protein stability is to use stabilizer or modify protein to avoid denaturation and aggregation; another way is to avoid the pro-instability environment.
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Purpose To prepare bFGF-PLGA microspheres and to investigate the characteristics. Methods The bFGF-PLGA microspheres were prepared by W_1/O/W_2 multiple emulsion volatilizing method, the morphology was investigated using scanning electron microscope (SEM), the ELISA method was used to establish the regression equation and to detect the drug loading amount and encapsulation efficiency, as well as sustained-release profile in vitro . Results The microspheres seemed to be smooth and uniform with mean particle size of (0.75 ±0.08) μm,the the drug loading amount and encapsulation efficiency were [(59.9± 1.9) × 10~(-3)] % and (79.9±2.8)%, respectively, the accumulative release ratio was up to 80 % in the continuous period of forty-five days. Conclusion The bFGF-PLGA microspheres have better pharmaceutical properties and long-time sustained release effect in vitro.
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Growth hormone (GHRH) and pitutary adenylate cyclase activating peptide (PACAP) are the members of the PACAP/Glucagon superfamily,who are related in both sequence and function.Their stimulation of GH secretion and animal growth is concerned.A series of expression plasmid,pIRES1-GHRH-PACAP (P-G-P),plRESI-GHRH (P-G) and plRESI-PACAP(P-P),were constructed,extracted and purified,then transfected into CHO cell line with Lipofectamine.The expression was examined by RT-PCR,dot-ELISA and Western blotting.The biological activity of expression products was detected in rats.At 8 h after injection of transfection supematant,serum IGF-I concentrations in P-G-P group were significantly higher than that in other groups(P ＜ 0.05).PLGA encapsulating plasmid microspheres were prepared and injected intramuscularly into rabbit legs.Growth behavior and IGF-1 level were measured at day 0,15,30 and 45 after injection.Greater body weights gain and higher serum 1GF- [ levels were observed in three plasmid microsphere injection groups,compared with control group.At day 30,the body weight gain in P-G-P group was greater than saline group (81%,P＜ 0.01),P-G mierosphere group (15%,P＜ 0.05) and P-P microsphere group (7%,P＞ 0.05),serum IGF-I concentration in P-G-P microsphere group showed a 16.68% increase to P-G microsphere (P ＞ 0.05),a 17.14% increase to P-P microsphere(P ＞ 0.05) and a 50.46% increase to control (P ＜ 0.05).These results suggest that co-expression of GHRH and PACAP in one expression plasmid might exert an additive stimulation of GH secretion and growth when delivered into rabbit skeletal muscle with PLGA mierosphere.The results may provide a new approach to regulate animal growth.
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BACKGROUND: Although IL-12 has been widely accepted to play a central role in the control of pathogen infection, the use of recombinant IL-12 (rIL-12) as a vaccine adjuvant has been known to be ineffective because of its rapid clearance in the body. METHODS: To investigate the effect of sustained release of IL-12 in vivo in the peptide and protein vaccination models, rIL-12 was encapsulated into poly (DL-lactic-co-glycolic acid) (PLGA). RESULTS: We found that codelivery of IL-12-encapsulated microspheres (IL-12EM) could dramatically increase not only antibody responses, but also antigen-specific CD4(+) and CD8(+) T cell responses. Enhanced immune responses were shown to be correlated with protective immunity against influenza and respiratory syncytial virus (RSV) virus challenge. Interestingly, the enhancement of CD8(+) T cell response was not detectable when CD4(+) T cell knockout mice were subjected to vaccination, indicating that the enhancement of the CD8(+) T cell response by IL-12EM is dependent on CD4(+) T cell "help". CONCLUSION: Thus, IL-12EM could be applied as an adjuvant of protein and peptide vaccines to enhance protective immunity against virus infection.