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BACKGROUND:Cycloserine with low hepatotoxicity exhibits no cross-resistance with the existing anti-tuberculosis drugs,and has been commonly used for the treatment of drug-resistant tuberculosis.However,its oral administration or injection leads to a certain degree of neurotoxicity.OBJECTIVE:To prepare poly(lactic-co-glycolic acid) (PLGA)-cycloserine sustained-release microspheres which are expected to reduce the neurotoxicity and adverse reactions,and maintain the drug concentration in the bone tuberculosis region for a long time,and to observe the in vitro drug release of the microspheresMETHODS:Double emulsion solvent evaporation method was used to prepare PLGA-cycloserine microspheres that were bonded into sponge implant by Bletilla striata polysaccharide extract.Then,morphology,particle size,encapsulation efficiency and in vitro performance of the microspheres were observed.The drug loading,burst release,appearance and dispersion of the microspheres were observed at 0,1,2 months after the microspheres were placed in room temperature (25 ℃),high temperature (60 ℃) and high humidity (93％),respectively.RESULTS AND CONCLUSION:The PLGA-cycloserine microspheres that were round and spherical presented with the mean particle size of (143±38) μm,the drug loading of 38.38％ and the encapsulation efficiency of 67.54％.No burst release occurred,and the cumulative release of drug within 50 days was 65.62％ After being stored at room temperature,high temperature and high humidity for 1 and 2 months,the microspheres were intact in the appearance and morphology,and showed insignificant changes in drug loading and burst release.To conclude,the time of degradation and the release of drug accord with the biological requirements of bone restoration.
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BACKGROUND: The technology of biodegradable materials covering growth factors can be used to make sustained-release microspheres, which provides the feasibility for the efficient utilization of growth factors. OBJECTIVE: To prepare nano/micron-sized spheres using recombinant human bone morphogenetic protein 2/poly(lactic-co-glycolic acid) (rhBMP-2/PLGA)copolymer and to compare their release behaviors by in vivo and in vitro release experiments. METHODS: The rhBMP-2/PLGA nano/micron-sized spheres were prepared by emulsion solvent evaporation method to control the rate of pulp mixing.(1)In vitro release experiment:Prepared nano/micron-sized spheres were dissolved in PBS for 70 days,and then ELISA method was used to detect the rhBMP-2 concentration in the supernatant at different time.(2)In vivo release experiment:Forty-four New Zealand rabbits were divided into two groups, and rhBMP-2/PLGA nano/micron-sized spheres were respectively implanted into trochanteric defects. The concentration of rhBMP-2 in the defect site was detected by ELISA within 70 days after implantation. RESULTS AND CONCLUSION:In vitro sustained release experiment:There was a sudden release of nanospheres in the former 3 days,and the cumulative release nearly reached 41%, followed by a steady and slow release, and then the cumulative release was up to approximately 83% at 70 days. The initial release of micron-sized spheres was less than that of nanospheres, and the cumulative release was about 20% within the former 3 days and reached to 70% at 70 days.In vivo sustained release test:There was a sudden release of the nanospheres,the cumulative release was nearly 35%, followed by a steady and slow release, and then the cumulative release was up to approximately 72% at 70 days. The initial release of micron-sized spheres was less than that of nanospheres, and the cumulative release was about 21% in the former 3 days and increased to about 63% at 70 days.In both in vivo and in vitro release experiments,the release duration of micron-sized spheres was longer than that of nanospheres in the former 3 days. To conclude, the release time of rhBMP-2/PLGA micron-sized spheres fulfills the need of bone growth cycle, therefore, rhBMP-2/PLGA micron-sized spheres are more favorable than rhBMP-2/PLGA nanospheres for bone defect repair in clinical practice.
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BACKGROUND: Compared with traditional biological materials, self-assembling peptide RADA16 has gained much attention in biomedical fields such as three-dimensional cell culture, tissue repair, hemostasis and drug/protein release for its high water content, structural stability, good biocompatibility and nontoxic degradation products. OBJECTIVE: To review the basic structure and properties of self-assembling peptide RADA16 and the latest progress in biomedical research. METHODS: CNKI, Medline and PubMed databases were retrieved by using computer to search relevant articles about self-assembling peptide RADA16 published from 2005 to 2017. The key words were "self-assembling peptide hydrogel;RADA16; scaffold; tissue repair; hemostasis; drug/protein release" in Chinese and English, respectively. RESULTS AND CONCLUSION: Self-assembling peptide molecules can spontaneously form unique β-strand structures and self-assembly into nanofibers under physiological media or salt solution. As a new scaffold material for tissue engineering, it not only solves the problem of incompatibility between cells and material interface, but also has the advantages of simulating the extracellular matrix effectively, enhancing cell biological activity and maintaining three-dimensional environment. The self-assembling peptide RADA16 and its derivatives not only show good prospects for development and application in three-dimensional cell culture, tissue repair, hemostasis, and drug/protein release, but also face many challenges, such as how to integrate the self-assembling peptide with bio-macromolecular material, and how to control the damage to a target.