An improved solvent evaporation method to produce poly (lactic acid) microspheres via foam-transfer

The aim of this work was to study an improved solvent evaporation method to prepare poly (lactic acid) (PLA) microspheres via foam-transfer. Since the foaming process and its transfer were critical to the improved method, they have been studied. Additionally, the delivery capability of foams was studied as a function of the oil/water ratio, the stirring rate, the concentration of polyvinyl alcohol (PVA) and ethanol (EtOH) in the aqueous phase (omega(PVA), omega(EtOH)). It was found that foaming varied during the preparation process and it influenced the properties of PLA microspheres. When the oil/water ratio (w/w) >= 3:10, stirring rate >= 600 r/min, omega(PVA) >= 1 wt%, and omega(EtOH) = 0 wt%, solvent evaporation was able to produce enough foams for foam-transfer, which helped to deliver more than 89 wt% PLA microspheres to the receiving vessel. However, omega(PVA) <= 0.3 wt% and omega(EtOH) = 20 wt% were unfavorable for maintaining the spherical shape of PLA microspheres and caused the aggregation. The methodology was further used to prepare azoxystrobin-loaded PLA microspheres successfully with a high encapsulation efficiency of 86.54%. This work is meaningful since it enables an efficient and continuous route to prepare functional biodegradable polymer microspheres. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This research aimed to prepare high encapsulation efficiency poly(lactic acid) microspheres via an improved solvent evaporation method with foam-transfer. The critical process of foam transfer was studied, and factors affecting it were investigated. Results showed that appropriate oil/water ratio, stirring rate, and concentrations of PVA and EtOH could aid in producing enough foam for effective foam-transfer, leading to enhanced delivery efficiency of microspheres.