Preparation and characterization of melittin-loaded poly (DL-lactic acid) or poly (DL-lactic-co-glycolic acid) microspheres made by the double emulsion method

Department of Pharmaceutics, School of Pharmaceutical Science, Shenyang Pharmaceutical University, No. 103, Wenhua Road, Shenyang 110016, China.
Journal of Controlled Release (Impact Factor: 7.71). 11/2005; 107(2):310-9. DOI: 10.1016/j.jconrel.2005.07.001
Source: PubMed


The water soluble peptide, melittin, isolated from bee venom and composed of twenty-six amino acids, was encapsulated in poly (DL-lactic acid, PLA) and poly (DL-lactic-co-glycolic acid, PLGA) microspheres prepared by a multiple emulsion [(W1/O)W2] solvent evaporation method. The aim of this work was to develop a controlled release injection that would deliver the melittin over a period of about one month. The influence of various preparation parameters, such as the type of polymer, its concentration, stabilizer PVA concentration, volume of internal water phase and level of drug loading on the characteristics of the microspheres and drug release was investigated. It was found that the microspheres of about 5 microm in size can be produced in high encapsulation (up to 90%), and the melittin content in the microspheres was up to 10% (w/w). The drug release profiles in vitro exhibited a significant burst release, followed by a lag phase of little or no release and then a phase of constant melittin release. The type of polymer used was a critical factor in controlling the release of melittin from the microspheres. In this study, the rate of peptide release from the microspheres correlated well with the rate of polymer degradation. Moreover, melittin was released completely during the study period of 30 days, which agreed well with the polymer degradation rate.

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    • "Higher PVA concentration minimized the formation of irregular and undesired microparticles, and increased the recovery of microparticles. In addition, high concentration of PVA could keep droplets dispersed and prevent agglomeration[14]. On the other hand, increasing the concentration of HPMC from 15:2 to 8:6 suppressed microparticles recovery from 71.2 to 53.7 %. "

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    • "One of the reasons for this phenomenon may be that the more of PVA molecules are absorbed on the surfaces between organic phase and aqueous phase, the lower is the interfacial tension between the oil and aqueous phase (Ito et al. 2007). Another reason may be the increase in viscosity of the outer aqueous phase with increasing concentration of PVA, which prevents the emulsion droplets from coalescence (Cui et al. 2005). Both of these resulted in smaller and more stable emulsion droplets. "
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    • "Such biodegradable and biocompatible polymers include polylactic acid (PLA), polyglycolic acid (PGA), and polylactic-co-glycolic acid (PLGA). The latter is approved for therapeutic use by the Food and Drug Administration (FDA) and is one of the most widely used polymers in nano- and microparticle production [31, 67]. "
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