A reformative shear precipitation procedure for the fabrication of vancomycin-loaded poly(lactide-co-glycolide) microspheres

Abstract

This study reports the encapsulation of vancomycin, as a model hydrophilic drug, into poly(lactide-co-glycolide) microspheres using a novel reformative shear precipitation procedure. In contrast to the external aqueous phase used in the conventional microencapsulation technique based on emulsion solvent evaporation/extraction, the reformative shear precipitation procedure explored in this study uses a shear medium composed of glycerol as the viscous medium and ethanol as polymer antisolvent, which is relatively immiscible with the hydrophilic drug. This limits drug diffusion and leads to rapid microsphere solidification, which allows a large proportion of the hydrophilic drug to be encapsulated within the microspheres. The influence of various processing parameters, including polymer concentration, volume ratio of ethanol to glycerol in the shear medium, volume of aqueous drug solution, initial drug loading, and injecting rate of the drug-polymer emulsion, on the encapsulation efficiency and characteristics of resulting microspheres were investigated. The morphology and release characteristics, as well as mechanical, in vitro and in vivo behaviour of vancomycin-loaded poly(lactide-co-glycolide) microspheres prepared using the novel procedure were also investigated. The results demonstrated that the reformative shear precipitation procedure could achieve the loading of hydrophilic drugs into poly(lactide-co-glycolide) microspheres with high encapsulation efficiency, and the success of the procedure was largely influenced by the volume ratio of ethanol to glycerol in the shear medium. Vancomycin-loaded poly(lactide-co-glycolide) microspheres prepared using this procedure demonstrated favourable mechanical characteristics, antibacterial activity, and in vivo degradation behaviour which suggested their suitability for use as a sustained delivery system.

In vitro drug release and antibacterial activity evaluation of silk fibroin coated vancomycin hydrochloride loaded poly (lactic-co-glycolic acid) (PLGA) sustained release microspheres

“…16–20 Some related studies have shown that encapsulating vancomycin in PLGA microspheres can prolong the release time of drug, reduce the number of drug administration, reduce systemic toxicity, etc. 21,22 However, researchers have found that drug loaded PLGA sustained release microspheres would experience drug burst release at the initial stage of drug release, which is mainly due to the porous structure on the surface of drug loaded microspheres. 23 The pore structure makes the surface of microsphere communicate with the internal structure.…”

Time-of-flight secondary ion mass spectrometry analyses of vancomycin

“…8 We have reported vancomycin-loaded PLGA microspheres and scaffolds for controlled-release drug delivery systems. 9,10 The scaffold approach is especially promising in bone regeneration as scaffold provides mechanical support for cell growth and the loaded biomolecules and antibiotics enhance tissue formation and prevent infections. 11,12 For such drugloaded polymer matrix systems, in vitro and in vivo drug release kinetics and biodegradability, as well as their applications, have been extensively explored.…”