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Resveratrol (Res) has been widely used in personal-care and pharmaceutical products due to its anti-oxidant, anti-inflammatory, cardioprotective and anti-cancer properties. However, the direct application of Res as functional additives have been limited due to its insolubility and instability. In this work, Res is loaded on the biodegradable ethyl cellulose (EC) carrier to prepare highly porous EC/Res microspheres via a foam-transfer method to understand the sustained release and the degradation property. The experimental results show that when the PVA concentration = 2.5 wt%, the stirring rate = 600 rpm, the oil/water (O/W) ratio = 1:2, the polymer concentration = 1:25, the heating rate = 0.33 °C/min, and the viscosity of EC = 90 ~ 110 mpa.s, the EC/Res microspheres are obtained with a yield up to 80.70 wt% and an encapsulation efficiency of 73.89% via the batch-process; the EC/Res microspheres are further produced continuously with a higher encapsulation efficiency of 90.63% with a yield of 85.58 wt%. The EC/Res microsphere reaches a cumulative release rate up to 91.97 wt% in the phosphate buffer solution (PBS) at pH = 5.0 under 45 °C for 120 h. After the EC/Res microspheres degraded in PBS (pH = 7.4) for 45 days, the hardness decreased from 12.01 ± 0.56 MPa to 4.02 ± 0.45 MPa. This work thus provides a practical solution for Res's application as sustained release functional additives. [ABSTRACT FROM AUTHOR]

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 (ω PVA, ω 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, ω PVA ≥ 1 wt%, and ω 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, ω PVA ≤ 0.3 wt% and ω 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. [ABSTRACT FROM AUTHOR]

This study has developed a method to produce porous polymeric microspheres in a foam phase. And, the foam phase was a mixture of polymer, organic solvent, porogen and emulsion stabilizer. The process was comprised of a series of constant steps homogenization of the materials, growth of the foam phase and collection of the products. The growth of the foam phase was the key which combined mechanical agitation, solvent evaporation and oil droplets development under increasing temperature. The method has been seen time-saving, high yield and continuous process and it could be useful for industrial production of porous polymer microspheres in a continuous process. [ABSTRACT FROM AUTHOR]

Polymeric microspheres with different internal structures have been widely used because of their characteristics in the structures. This paper reports a method of controlling the internal structures of polymeric microspheres via the introduction of a water-soluble organic solvent to the continuous phase in the foam phase preparation of porous polymeric microspheres. The introduction of a water-soluble organic solvent enables the control of polymeric microspheres’ internal structures, from porous to hollow. Because a water-soluble organic solvent is introduced, the organic solvent may be diffused toward the interface because of the affinity between the organic solvent and the oil droplets, resulting an accumulation of organic solvent molecules at the interface to form an organic solvent layer. The presence of this layer may decrease the evaporation rate of the internal organic solvent in an oil droplet, which extends the time for the mingling of porogen droplets to form a few large pores or even an extremely large single pore inside. This method is also capable of altering the thickness of hollow microspheres’ shells in a desired way, with improved efficiency, yield and the capacity for continuous use on an industrial scale. [ABSTRACT FROM AUTHOR]

• Biodegradable PBAT microspheres were prepared by via foam-transfer method. • Degradation behavior indicated by the change on the hardness of PBAT microsphere was investigated. • The degradation of PBAT microspheres was influenced by the environmental conditions, particle size and structure. Degradable polymer microspheres hold considerable significance for their application in everyday consumer products. In this study, poly (butylene adipate-co-butylene terephthalate) (PBAT) microspheres were synthesized using an improved solvent evaporation method via foam-transfer, and their degradation behavior was subsequently comprehensively examined. Experimental outcomes revealed that optimal conditions, including a PVA concentration of 2.0 wt %, a stirring rate of 600 rpm, a polymer/solvent ratio of 1:16, and a temperature of 45°C, yielded PBAT microspheres through the foam-transfer method with an impressive yield of up to 90 wt %. The degradation of PBAT microspheres was influenced by various factors, including environmental conditions, particle size, and structure. Specifically, PBAT microspheres exhibited heightened degradation when immersed in an acidic environment, possessing smaller particle sizes and a more intricate structure. In a water environment with a pH of 4, PBAT microspheres displayed a degradation rate of 36.16 wt % over a 90-day period. Furthermore, PBAT microspheres with particle sizes ranging from 20 to 30 μm showcased a degradation rate of 49.54 wt % after a 90-day immersion in water at 25°C. Notably, microspheres characterized by substantial porosity, with a porogen to polymer ratio of 180 wt %, exhibited a remarkable degradation rate of 61.66 wt % under the same conditions. As a result, this study offers a promising solution to address the issue of microplastic pollution in everyday consumer products. [ABSTRACT FROM AUTHOR]

[Display omitted] • A method to prepare porous polymer microspheres via foaming-transfer was developed. • Foaming-transfer enabled a continuous production of porous polymer microspheres. • Introducing EtOH and acetone enabled versatility on porous polymer microspheres. A solvent evaporation self-motivated synthetic methodology based on foaming-transfer has been developed to fabricate porous polymer microspheres. The novel method is a technical improvement for the traditional solvent evaporation method, in which solvent evaporation enables foam formation and foaming-transfer. Foaming-transfer helps deliver oil droplets from the aqueous phase to the receiving vessel, while phase separation takes place in oil droplets between polymer and porogen to produce porous polymer microspheres. Because of foaming-transfer, the novel method enables a continuous production of polymer microspheres via continuous feeding. Additionally, high efficiency has been observed since solvent evaporation in foams is much quicker than that in the aqueous phase. The methodology was further developed to prepare versatile porous polymer microspheres by introducing extra organic solvents, including ethanol (EtOH), acetone and ethyl acetate. Solvents like EtOH and acetone that have relatively poor compatibilities with oil phase were able to control structure, surface morphology and particle size of polymer microspheres when varying the concentration of solvents; while introducing solvents like ethyl acetate having good miscibility with oil phase hardly changed these properties. It was mainly because the difference on the compatibilities led to different distributions of solvent molecules in the system, which altered the evaporation process of solvent and the surface tension of the system, leading to the variation on structure, particle size and surface roughness. This work is meaningful since it developed an efficient, continuous and versatile method for the production of porous polymer microspheres. [ABSTRACT FROM AUTHOR]