Saurer Eric M, Flessner Ryan M, Buck Maren E, Lynn David M
Department of Chemical and Biological Engineering, University of Wisconsin - Madison, 1415 Engineering Drive, Madison, WI 53706, USA.
J Mater Chem. 2011 Feb 14;21(6):1736-1745. doi: 10.1039/C0JM02633F.
We report on the fabrication of covalently crosslinked and amine-reactive hollow microcapsules using 'reactive' layer-by-layer assembly to deposit thin polymer films on sacrificial microparticle templates. Our approach is based on the alternating deposition of layers of a synthetic polyamine and a polymer containing reactive azlactone functionality. Multilayered films composed of branched poly(ethylene imine) (BPEI) and poly(2-vinyl-4,4-dimethylazlactone) (PVDMA) were fabricated layer-by-layer on the surfaces of calcium carbonate and glass microparticle templates. After fabrication, these films contained residual azlactone functionality that was accessible for reaction with amine-containing molecules. Dissolution of the calcium carbonate or glass cores using aqueous ethylenediamine tetraacetic acid (EDTA) or hydrofluoric acid (HF), respectively, led to the formation of hollow polymer microcapsules. These microcapsules were robust enough to encapsulate and retain a model macromolecule (FITC-dextran) and were stable for at least 22 hours in high ionic strength environments, in low and high pH solutions, and in several common organic solvents. Significant differences in the behaviors of capsules fabricated on CaCO(3) and glass cores were observed and characterized using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Whereas capsules fabricated on CaCO(3) templates collapsed upon drying, capsules fabricated on glass templates remained rigid and spherical. Characterization using EDS suggested that this latter behavior results, at least in part, from the presence of insoluble metal fluoride salts that are trapped or precipitate within the walls of capsules after etching of the glass cores using HF. Our results demonstrate that the assembly of BPEI/PVDMA films on sacrificial templates can be used to fabricate reactive microcapsules of potential use in a wide range of fields, including catalysis, drug and gene delivery, imaging, and biomedical research.
我们报道了使用“反应性”逐层组装法在牺牲性微粒模板上沉积聚合物薄膜来制备共价交联且具有胺反应性的中空微胶囊。我们的方法基于合成多胺层和含有反应性氮杂内酯官能团的聚合物层的交替沉积。由支化聚（乙烯亚胺）（BPEI）和聚（2-乙烯基-4,4-二甲基氮杂内酯）（PVDMA）组成的多层膜在碳酸钙和玻璃微粒模板表面逐层制备。制备后，这些薄膜含有可与含胺分子反应的残留氮杂内酯官能团。分别使用乙二胺四乙酸（EDTA）水溶液或氢氟酸（HF）溶解碳酸钙或玻璃核，导致形成中空聚合物微胶囊。这些微胶囊足够坚固，能够包封并保留模型大分子（异硫氰酸荧光素-葡聚糖），并且在高离子强度环境、低pH和高pH溶液以及几种常见有机溶剂中至少稳定22小时。使用扫描电子显微镜（SEM）和能量色散X射线光谱（EDS）观察并表征了在碳酸钙和玻璃核上制备的胶囊行为的显著差异。在碳酸钙模板上制备的胶囊在干燥时会塌陷，而在玻璃模板上制备的胶囊则保持刚性和球形。EDS表征表明，后一种行为至少部分是由于使用HF蚀刻玻璃核后，不溶性金属氟化物盐被困或沉淀在胶囊壁内所致。我们的结果表明，在牺牲性模板上组装BPEI/PVDMA膜可用于制备在广泛领域具有潜在用途的反应性微胶囊，包括催化、药物和基因递送、成像以及生物医学研究。
