Influence of morphology and drug distribution on the release process of FITC-dextran-loaded microspheres prepared with different types of PLGA

Abstract

The aim of the present work was to understand the collaborative roles and the comprehensive effects of polymer nature, morphology, drug distribution and release behaviour for PLGA microspheres prepared by the double emulsion method. The morphology and drug distribution of the FITC-dextran-loaded microspheres were investigated by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM), respectively. The results show that the morphology and release profiles depend on the polymer nature. For the capped PLGA RG502, the porosity, pore size and drug distribution had no pronounced influence on the release profile beyond the initial release. No significant changes in size and morphology were found and there was negligible water uptake during the release process. PEG addition as a pore maker indicated a possible way to modify the release rate at the second release stage. However, in the case of the uncapped PLGA RG503H, release profiles were dependent upon changes in porosity, pore size and drug loading. Increases in porosity, internal pore size and loading resulted in a continuous release profile. Previous studies have shown the importance of different process parameters on morphology and drug release, but in this work it is clear that polymer nature is a determining factor.

Polymer degradation and drug delivery in PLGA‐based drug–polymer applications: A review of experiments and theories

“…For example, by increasing the porosity of the PLGA microspheres, the initial burst release of fluorescein isothiocyanate‐labeled dextran more than doubled, from 6.6% for the nonporous microspheres to 14.7% for the porous microspheres. However, the porous PLGA microspheres presented a lower release rate in the second stage; at 21 h of release, the cumulative release was around 30% for both the nonporous and porous particles . This may be due to faster neutralization of autocatalysis effect because of the presence of the pores.…”

“…It turned out that for porous microparticles, the relative lidocaine release rates were increased with decreasing particle sizes in PBS (phosphate‐buffered saline) at pH 7.4; however, for initially nonporous microparticles with identical composition, the results were exactly opposite . Porosity also affects the behavior of the initial and the second release phases from PLGA‐based systems . For example, by increasing the porosity of the PLGA microspheres, the initial burst release of fluorescein isothiocyanate‐labeled dextran more than doubled, from 6.6% for the nonporous microspheres to 14.7% for the porous microspheres.…”

Improved Drug Loading and Sustained Release of Entecavir‐loaded PLGA Microsphere Prepared by Spray Drying Technique

“…This SR pattern was also observed in other MPs prepared with different types of PLGA polymers. 35 The terminal carboxyl group may accelerate the autocatalytic hydrolysis of the ester bonds of the biodegradable polymer and the corrosion of the MPs. Moreover, the high viscosity and boiling point of solvent (acetic acid) might influence on the compactness and/or density of MPs, minimizing burst drug release.…”

Salmon calcitonin‐loaded PLGA microspheres/calcium phosphate cement composites for osteoblast proliferation

“…The addition of PLGA MS could generate the macroporosity into the CPC through erosion and contribute to the initial strength of CPC composites in the early stages . Moreover, PLGA properties including the molecular weight and end‐group functionality could exert great influences on drug release from MS and the degradation rate of CPC composites . In our preliminary research, it have been demonstrated that SCT‐PLGA MS with 20 kDa‐COOH and 40 kDa‐COOH (SCT‐PLGA‐20 COOH MS and SCT‐PLGA‐40 COOH MS) could provide high degradation rate and sustained release of SCT, which would be beneficial for macropore formation and bone ingrowth.…”