State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Institute of Biochemical Engineering & Environmental Technology, Lanzhou University, Lanzhou 730000, China.
ACS Appl Mater Interfaces. 2012 Oct 24;4(10):5169-78. doi: 10.1021/am301104c. Epub 2012 Sep 28.
Superparamagnetic alginate nanospheres with diameter of 50 nm were prepared by self-assembly of alginate in the Ca(2+) solution; and then superparamagnetic alginate/chitosan nanospheres, which have positive charge and could adsorb lipase directly, were obtained with a following assembly of chitosan based on the electrostatic interaction between alginate and chitosan. Subsequently, oxidic poly (ethylene glycol) was used to functionalize the magnetic alginate/chitosan nanospheres. Thus, the magnetic nanospheres with aldehyde groups and a brushlike structure were formed. With various characterizations, it was verified that the magnetic alginate/chitosan nanospheres held small diameters (around 60 nm) and displayed superparamagnetism with high saturation magnetization. The Candida rugosa lipase (CRL), meanwhile, was immobilized onto the magnetic alginate/chitosan nanospheres by electrostatic adsorption and covalent bonding, respectively. Afterward, a layer-by-layer (LBL) assembly process was utilized to coat the immobilized CRL (ICRL) with covering layers made up of alginate and chitosan. After studying the properties of ICRL such as activity, kinetic behaviors, stability and reusability, it was proved that the ICRL prepared with two methods displayed more excellent properties than that prepared with electrostatic adsorption only. Additionally, coating ICRL with covering layers showed good effect on improving the stability of ICRL.
50nm 直径的超顺磁海藻酸钠纳米球通过海藻酸钠在 Ca(2+)溶液中的自组装来制备；然后，通过基于海藻酸钠和壳聚糖之间的静电相互作用的壳聚糖进一步组装，获得带正电荷且可直接吸附脂肪酶的超顺磁海藻酸钠/壳聚糖纳米球。随后，用氧化聚乙二醇对磁性海藻酸钠/壳聚糖纳米球进行功能化。这样，形成了具有醛基和刷状结构的磁性纳米球。通过各种表征，验证了磁性海藻酸钠/壳聚糖纳米球具有较小的直径（约 60nm）和高饱和磁化强度的超顺磁性。同时，通过静电吸附和共价键合将 Candida rugosa 脂肪酶（CRL）分别固定在磁性海藻酸钠/壳聚糖纳米球上。之后，利用层层（LBL）组装过程，用由海藻酸钠和壳聚糖组成的覆盖层对固定化 CRL（ICRL）进行涂层。研究了 ICRL 的性质，如活性、动力学行为、稳定性和可重复使用性，证明了两种方法制备的 ICRL 比仅通过静电吸附制备的 ICRL 具有更优异的性能。此外，用覆盖层对 ICRL 进行涂层处理对提高 ICRL 的稳定性具有良好的效果。
