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OBJECTIVE@#The purpose of this study is to investigate the effects of different drying methods on the physical properties and drug delivery of chitosan microspheres.@*METHODS@#Three types of drying methods were utilized, including air drying and freeze drying after freezing at -20 ℃ (slow cooling) and at -80 ℃ (fast cooling). The physical properties of microspheres were characterized. Utilizing bovine serum albumin (BSA) as the model drug, the in-vitro release behaviors of drug-loaded beads were investigated.@*RESULTS@#By comparing the physical properties of the different drying methods, the microspheres' diameters, porosities, and surface area were observed to increase successively from air drying and slow cooling to fast cooling, whereas the pore size and the swelling and degradation rates varied. The drug-loading experiments revealed that the loading capacity of air-dried microspheres was the lowest and the release rate was the slowest. Although the loading capacity of fast cooling microspheres was high, an obvious burst release was observed. The loading capacity of slow cooling microspheres was similar to that of the fast cooling microspheres and the loaded BSA can be released continuously.@*CONCLUSIONS@#The results indicate that different drying methods can affect the physical properties of chitosan microspheres, which further influence drug loading and release.
Assuntos
Quitosana , Portadores de Fármacos , Composição de Medicamentos , Microesferas , Tamanho da PartículaRESUMO
In order to promote the growth of chondrocyte ATDC-5 in collagen type II-hyaluronic acid-chondroitin sulfate composite scaffolds constructed previously in vitro, the sustained-releasing chitosan microspheres loading TGF-β1 were prepared by emulsification and cross-linking. In addition, ATDC-5 was inoculated into the scaffolds incorporating the chitosan microspheres with TGF-β1. Results show that the morphology of microsphere was round and uniform, mean diameter was about 100 nm, absorption rate was up to 983.7%±4.38%.When the microsphere was incubated under the condition of 10⁷ U/L lysozyme, the degradation rate was only 51.0%±1.8% on day 28. Moreover, to compare the effect of TGF-β1, the growth of ATDC-5 in different scaffolds was observed by MTT assay and fluorescence staining test. According to the cumulative release curve, TGF-β1 was released quickly at initial 24 h, then gradually decelerated, finally reached the plateau after 120 h. MTT assay and fluorescence staining test demonstrated that the scaffolds were suitable for ATDC-5 growth and proliferation, as well as, suggested that the sustained-releasing chitosan microspheres loading TGF-β1 could significantly promote the growth of ATDC-5.
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Objective To investigate the influence of HAp-CS composite microsphere scaffold on the in vitro cell behaviors of mesenchymal cells and evaluate its potential application for bone tissue engineering.Methods Nano-hydroxyap-atite (HAp)and chitosan (CS)composites solution were assembled into microsphere scaffold through microfluidic and observed by inverted microscope.Rat bone marrow mesenchymal stem cells were co-cultured in vitro with the microspheres for calculating the adhesion rate for the first 6h.Proliferation rate was measured by cell counting in the next 1,3,6,9 d,respectively,and GraphPad Prism 6 software was used for statistical analysis.The morphology of BMSCs on the surface of HAp-CS composite microsphere was observed by scanning electron micros-copy (SEM)and confocal scanning microscopy.The cells and HAp-CS microspheres were filled into a disc mold and co-cultured for 14 ~21 d to observe the morphology.Results HAp-CS microspheres were observed to be round and with uniform size by microscope.The adhesion rate of BMSCs reached 80% after cultured for 6 h,and proliferation rate reached the highest value when cultured for 6 d.SEM observations showed that BMSCs adhered compactly to the surface of the microspheres,and the microspheres could be connected together through BMSCs.Af-ter co-culturing BMSCs with microspheres for 14 ~21 d,a complete tissue constructs could be formed.Conclusion HAp-CS microspheres are proved to be good scaffolds for promoting BMSCs adhesion and proliferation.Large a-mount of extracellular matrix can be formed to connect microspheres after co-cultured for a certain time,which paves the way for HAp-CS microspheres to be applied for bone regeneration in animal experiments.
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This study was carried out on 32 New Zealand white rabbits, each weighing 3-3.5kg. Eight rabbits were allocated into each of four groups. The groups were a control group(I), hyaluronic acid group(II), chitosan microsphere encapsulating growth hormone group(III), calcium sulfate-chitosan powder group(IV). After a 1cm sized ostectomy was made on the tibial body with the periosteum preserved, artificial bone substitutes were implanted. Except group I, 1ml of hyaluronic acid were implanted in group II, 1ml of chitosan microsphere encapsulating growth hormone in group III, 1ml of manufactured calcium sulfate-chitosan complex powder in group IV. Results were evaluated using radiographic study every week, bone mineral density test and histologic examination at 2, 4, 6 weeks and three point bending test at 6 weeks after implantation. In the radiographic study, the formation and corticalization of callus were seen similarly in group III, IV and much more and earlier than group I, II. In the bone mineral density test and three point bending test to contralateral normal tibia in 6 weeks, the values in groups III and IV were statistically significantly higher than in group I and II(p<0.05). In histologic examination, group III and IV have more abundant and faster new boner formation than group I and II. In conclusion, calcium sulfate-chitosan complex powder and chitosan microsphere encapsulating growth hormone facilitates the formation of new bone. They will be used effectively as a bone substitute on defected bone in clinical situations.