Abstract：
One of the promising applications of rod-like chitin nanocrystals (ChNCs) is the use as particle emulsifier to develop Pickering emulsions. We reported a ChNC-stabilized oil-in-water emulsion system, and developed a Pickering emulsion-templated method to prepare polylactide (PLA) hollow microspheres here. The results showed that both non-modified ChNCs and acetylated ChNCs could well emulsify the dichloromethane (DCM) solution of PLA-in-aqueous mannitol solution systems, forming very stable emulsions. At the same oil-to-water ratios and ChNC loadings, the emulsion stability was improved with increasing acetylation levels of ChNCs, accompanied by reduced size of droplets. Through the solvent evaporation, the PLA hollow microspheres were templated successfully, and the surface structure was also strongly dependent on the acetylation level of ChNCs. At a low level of acetylation, the single-hole or multi-hole surface structure formed, which was attributed to the out-diffusion of DCM caused by the solvent extraction and evaporation. These surface defects decreased with increased acetylation levels of ChNCs. Moreover, the aqueous suspension with as-obtained PLA microspheres revealed shear-thinning property and good biocompatibility, thereby had promising application as injectable fillers. This work can provide useful information around tuning surface structures of the Pickering emulsion-templated polymer hollow microspheres by regulating acetylation level of ChNCs.
摘要：
棒状甲壳素纳米晶体（ChNC）的有希望的应用之一是用作颗粒乳化剂来开发Pickering乳液。我们报道了一种ChNC稳定的水包油乳液系统，并开发了Pickering乳液模板法制备聚乳酸（PLA）中空微球。结果表明，未改性的ChNCs和乙酰化的ChNCs均能很好地乳化聚乳酸在甘露醇水溶液中的二氯甲烷（DCM）溶液。形成非常稳定的乳液。在相同的油水比和ChNC负载下，乳液稳定性随着ChNCs乙酰化水平的增加而提高，伴随着液滴大小的减小。通过溶剂蒸发，PLA中空微球模板化成功，表面结构也强烈依赖于ChNC的乙酰化水平。在低水平的乙酰化下，形成的单孔或多孔表面结构，这归因于溶剂萃取和蒸发引起的DCM的外扩散。这些表面缺陷随着ChNC乙酰化水平的增加而减少。此外，所得PLA微球的水悬浮液显示出剪切稀化性质和良好的生物相容性，因此作为可注射填料具有很好的应用前景。这项工作可以通过调节ChNC的乙酰化水平来调节Pickering乳液模板化聚合物中空微球的表面结构，从而提供有用的信息。
