Poly(D,L-lactide-co-glycolide)(PLGA) microspheres were prepared by emulsion solvent evaporation method. The influences of inner aqueous phase, organic solvent, PLGA concentration on the morphology of microspheres were studied. The results showed that addition of porogen or surfactants to the inner aqueous phase, types of organic solvents and polymer concentration affected greatly the microsphere morphology. When dichloromethane was adopted as organic solvent, microspheres with porous structure were produced. When ethyl acetate served as organic solvent, two different morphologies were obtained. One was hollow microspheres with thin porous shell under a lower PLGA concentration, another was erythrocyte-like microspheres under a higher PLGA concentration. Three types of microspheres including porous, hollow core with thin porous shell(denoted by hollow in brief) and solid structures were finally selected for in vitro drug release tests. Bovine serum albumin(BSA) was chosen as model drug and encapsulated within the microspheres. The BSA encapsulation efficiency of porous, hollow and solid microspheres was respectively 90.4%, 79.8% and 0. And the ultimate accumulative release was respectively 74.5%, 58.9% and 0. The release rate of porous microspheres was much slower than that of hollow microspheres. The experiment results indicated that microspheres with different porous structures showed great potentials in controlling drug release behavior. 相似文献
The purpose of this study was to develop a suitable formulation for gentamicin sulfate (GS) that gives a sustained release of the drug. Therefore this drug was loaded into poly(D,L-lactide-co-glycolide) (PLGA) and poly(lactic-co-hydroxymethyl glycolic acid) (PLHMGA) microspheres. The effects of various formulation parameters (ethanol, surfactant, osmotic value of the external phase, polymer type and concentration) on particle characteristics (size, loading and release) were investigated. The GS loaded microspheres were prepared using a double emulsion evaporation technique. The results demonstrate that neither ethanol nor surfactants had beneficial effects on the drug loading efficiency (around 4-10%). However, an increase in buffer concentration (and thus osmotic pressure) of the external phase resulted in a substantial increase of GS-loading (from 10 to 28%). Further, an increase of concentration of PLGA in DCM from 10% to 15/20% caused a 4-time increase of the drug loading. The best formulation identified in this study had a loading efficiency of around 70% resulting in PLGA microspheres with a 6% (w/w) loading. The particles showed a burst release of the drug depending on their porosity, followed by a phase of 35 days where hardly any release occurred. The drug was then slowly released for around 25 days likely due to degradation of the microspheres. The drug loading efficiency of GS in PLHMGA was not significantly different from PLGA microspheres (64%). The release of GS from PLHMGA microspheres was faster than that of PLGA because the degradation rate of PLHMGA is more rapid than PLGA. This study shows that prolonged release of gentamicin can be obtained by loading this drug into microspheres made of biodegradable aliphatic polyesters. 相似文献
The entrapment of a protein in porous poly(d,l ‐lactide‐co‐glycolide) (PLGA) microspheres is demonstrated through the closure of their outer surface pores for sustained delivery of the protein. The porous PLGA microspheres with less than 10 μm in size are prepared by electrospraying. Aqueous solutions containing fluorescein isothiocyanate‐dextran or bovine serum albumin (BSA) are penetrated into the inner pores as a result of vacuum treatment, and the outer surface pores of the porous PLGA microspheres are then closed using a solvent (dimethyl sulfoxide) to ensure entrapment of the macromolecules. Confocal microscopy images confirm the presence of a large amount of the macromolecules inside the porous structure. Circular dichroism spectroscopy and release analysis reveal that BSA is entrapped without denaturation and released in a sustained manner for a period of over 2 months, respectively.
In order to encapsulate and controlled-release bioactive proteins,three fibrous membranes,i.e.,poly(L-lactide-co-glycolide)(PLGA),hybrid PLGA and chitosan(H-PLGA/CS),and core/shell PLGA/CS (C-PLGA/CS),were produced by emulsion electrospinning,co-electrospinning and coaxial electrospinning,respectively.Bovine serum albumin(BSA) was selected as a model protein.The loading efficiency of BSA in the PLGA membrane was 1.56%,lower than those of H-PLGA/CS(5.98%) and C-PLGA/CS(4.80%).BSA release profiles from the th... 相似文献
Well-defined nitrogen-doped, hollow SiO2/TiO2 hybrid spheres were successfully prepared through a two-step sol-gel synthesis combined calcination process using triethylamine as the nitrogen source. In this approach, polystyrene (PS)/silica microspheres were first synthesized. Subsequently, the amine-treated PS/SiO2/TiO2 hybrid spheres were obtained by sol-gel method. Finally, the elimination of the PS core, nitrogen-doping process, and crystallization of amorphous TiO2 were simultaneously conducted in the calcination process to acquire the final products. The as-prepared hybrid spheres were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy. The results of XRD, FTIR, and XPS spectra indicated that nitrogen was really doped into the anatase TiO2 shell and confirmed that most nitrogen dopants might be present in the chemical environments of N-Ti-O and Ti-N-O. It was found that the absorption shoulder of nitrogen-doped hollow SiO2/TiO2 hybrid spheres vastly shifted to the visible region up to around 530 nm. The photoluminescence (PL) bands showed spectral lines at about 421, 472, and 529 nm, which were attributed to the self-trapped excitons, F and F+ centers. Moreover, the intensity of the PL spectra band of hollow SiO2/TiO2 hybrid spheres increased with as the amount of titanium tetrabutoxide (TBOT) precursor increased. However, the doping of nitrogen into hollow SiO2/TiO2 hybrid spheres led to the drastic quenching of photoluminescence because of the increase in the separation efficiency of the photoinduced electron and hole pairs. 相似文献
A sustained release poly(DL-lactide-co-glycolide) (PLGA) microsphere delivery system to treat prostate cancer for a luteinizing hormone-releasing hormone (LHRH) antagonists, LXT-101 was prepared and evaluated in the paper. LXT-101 microspheres were prepared from PLGA by three methods: (1) double-emulsion solvent extraction/evaporation technique, (2) single-emulsion solvent extraction/evaporation technique, and (3) S/O/O (solid-in-oil-in-oil) method. The microspheres were investigated on drug loading, particle size, surface morphology and in vitro release profiles. An accelerated release approach was also established in order to expedite the evaluation periods. The in vivo evaluation of the microspheres was made by monitoring testosterone levels after subcutaneous administration to rats. The LXT-101 PLGA microspheres showed smooth and round surfaces according to a scanning electron microscopic investigation, and average particle size of ca. 30 mum according to laser diffractometry. The drug encapsulation efficiency of microspheres was influenced by LA/GA ratio of PLGA, salt concentrations, solvent mixture and preparation methods. Moreover, LA/GA ratio of PLGA, different preparation methods and different peptide stabilizers affected in vitro release of drugs. In vivo study, the testosterone levels were suppressed to castration up to 42 d as for the 7.5 mg/kg dose. And in vivo performance of LXT-101 microspheres was dose-dependent. The weights of rat sexual organs decreased and histopathological appearance of testes had little changes after 4-month microspheres therapy. This also testified that LXT-101 sustained release microspheres could exert the efficacy to suppress the testosterone level to castration with little toxicity. In conclusion, the PLGA microspheres could be a well sustained release system for LXT-101. 相似文献
