PubMed · 11838817
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Deepak Agrawal. 2002. Vasospasm.. https://pubmed.ncbi.nlm.nih.gov/11838817/
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Human serum albumin (HSA) was encapsulated as a model protein in microspheres of biodegradable and biocompatible polymers by the water-in-oil-in-water (w/o/w) emulsion solvent extraction/evaporation (double emulsion) technique for purpose of controlled release. To improve the properties and control the rate of drug release of the delivery vehicle, materials with different hydrophobicity from that of their conventional counterparts, such as poly(lactide-co-ethylene glycol) (PELA) in place of poly(lactide-co-glycolide) (PLGA) as the polymer matrix, ethyl acetate/acetone in place of dichloride methane (DCM) as the (co)solvent and d-alpha tocopheryl polyethylene glycol 1000 succinate (vitamin E TPGS) as the additive, were used to prepare the microspheres. It has been found that PELA microspheres, compared with PLGA ones, were slightly smaller in size if prepared at identical emulsification strength. They had more porous surface and internal structure, higher encapsulation efficiency (EE) and more rapid in vitro release rate. Furthermore, the physical properties of the microspheres were also affected by the presence of solvents and additives and their properties. Our results suggest that these materials could have interesting potential applications in preparation of polymeric microspheres for controlled protein release.
In this work we evaluate poly(lactic/glycolic) acid (PLGA) film-implants as potential biodegradable devices for controlled release of two different drugs: 5-Fluorouridine (5-FUR), a conventional low molecular weight water-soluble compound and SPf66 malaria vaccine, a therapeutic synthetic polypeptide. Three types of devices were prepared by solvent-casting techniques alone or combined with compression method: simple monolithic discs (SMD), multilayer discs with a central monolithic layer (MLDM), and multilayer discs with a central drug-reservoir (MLDR). For the highly water-soluble drug, 5-FUR, in vitro release from SMD showed an initial burst (24% in 2 h) followed by prolonged release over 20 days. In contrast, from a MLDM (two drug-free PLGA discs were added to the SMD) showed an initial lag-time of 12 days followed by a very fast second release phase. Finally, when the load of this system was increased from 3 to 9%, an extended release over 20 days with a low burst effect was obtained. For SPf66, the central reservoir containing the synthetic polypeptide MLDR reduces the possibility of degradation due to peptide contact with polymer solution. When four layers were added, 10 days sustained-release was obtained without any burst effect. With six layers a moderate pulse was obtained, 18-22 days from the beginning of the release. The results show the suitability of the proposed devices to control release and avoid the burst effect with highly water-soluble drugs; as well as modulate in vitro peptide release.
The influence of hydroxyapatite (OHAp) and gentamicin sulphate (GEN) contents on the release kinetics of GEN, in samples composed of OHAp, poly(methyl methacrylate) (PMMA) and poly(ethyl methacrylate) (PEMA) has been studied. For this purpose, samples with 30 and 40% of OHAp and 5 and 9% of GEN were prepared. The in vitro release study was carried out soaking the samples in simulated body fluid (SBF) at 37 degrees C for 70 days. The release profiles showed a faster release during the first 10 h, diminishing progressively until the end of the study. It was noticed that the percentage of released GEN increased with the OHAp content. For samples with 40% of OHAp, GEN release is nearly independent of the initial amount of such drug (in the range 5-9%), whereas for samples with 30% of OHAp, the release process is favoured by higher contents of GEN, which would favour a higher SBF uptake. GEN release is related to SBF uptake, which is in turn related, on the one hand, to the OHAp content (increase of the porosity and the hydrophilic character of the samples) and on the other hand, to content of GEN.