A new emulsification-crosslinking method was developed for the preparation of chitosan microspheres. The new method uses an aqueous alkali–urea solution, instead of the commonly used acidic solvents, to dissolve chitosan. After emulsification, the water-in-oil droplets are solidified by heating, taking advantage of the unique in situ thermal gelling behavior of the alkaline chitosan solution, instead of by crosslinking with a usually toxic crosslinker. The size of the microspheres can be controlled by the concentration of chitosan solution, stirring speed, emulsifier concentration, and the curing temperature. The resulting microspheres are physically crosslinked, instead of chemically crosslinked, and they are ready to dissolve in dilute acetic acid. The resulting chitosan microspheres are non-toxic and can be degraded by lysozyme. Bovine serum albumin, a model protein, can be facilely loaded into the microspheres by adsorption, and then released from the microspheres.

中文翻译：

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一种制备物理交联壳聚糖微球的乳化交联新工艺

开发了一种新的乳化交联法制备壳聚糖微球。新方法使用碱性尿素水溶液而不是常用的酸性溶剂来溶解壳聚糖。乳化后，油包水液滴通过加热固化，利用碱性壳聚糖溶液独特的原位热凝胶行为，而不是通过通常有毒的交联剂进行交联。微球的大小可以通过壳聚糖溶液的浓度、搅拌速度、乳化剂浓度和固化温度来控制。得到的微球是物理交联的，而不是化学交联的，并且它们可以溶解在稀乙酸中。所得壳聚糖微球无毒，可被溶菌酶降解。