Enzymatic Hydrolysis of a Layer-by-Layer Assembly Prepared from Chitosan and Dextran Sulfate
Enzymatic Hydrolysis of a Layer-by-Layer Assembly Prepared from Chitosan and Dextran Sulfate
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DOI：
10.1021/ma012153s
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发表时间：
2002-10
期刊：
影响因子：
5.5
通讯作者：
T. Serizawa;M. Yamaguchi;M. Akashi
中科院分区：
文献类型：
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作者：
T. Serizawa;M. Yamaguchi;M. Akashi
层-层（LbL）组装1允许形成具有分子层状纳米结构和表面上的纳米级厚度的聚合物膜。该方法基于通过静电、1货车德瓦耳斯、2氢键、3和电荷转移4相互作用从其溶液中顺序沉积相互作用聚合物。LbL组装在生物医学领域的应用是有吸引力的，因为它有助于创建独特的功能材料表面。哈贝尔等人，例如，利用LbL组装来产生生物惰性表面。然而，先前尚未证明源自LbL组装体的最外表面的交替生物活性，尽管已经实现了人全血对壳聚糖和硫酸葡聚糖（Dex）之间的LbL组装体的交替抗凝血活性与促凝血活性。[6]当聚合物由含有1 M NaCl的水溶液组装时，产生这种交替活性。由于向LbL组装过程中添加盐促进了较厚膜的形成，因此显然保持了每种聚合物的完整特性。因此，预期在合适的条件下制备的LbL组装体的生物活性的进一步改变。LbL组装体的解构不仅对于分析组装体的稳定性，而且对于组装体的技术和生物医学应用具有吸引力。通过改变pH值7和静电相互作用在高盐环境中7 c，8在LbL组件中氢键的消失已经解构了LbL组件。生物降解性是生物医用高分子材料的重要要求之一。在本研究中，我们证明了交替酶水解的LBL组装形成的壳聚糖和地塞米松。壳聚糖酶是一种水解壳聚糖的酶，应用于该工艺中。聚合物的化学结构如图1所示。为了实现交替酶解，（分子量1 200 000）（和子，日本），具有20%几丁质单元和Dex（分子量500 000）（和子，日本）在25%HCOOH的水溶液中进行（溶液pH值）1）和水（溶液pH值）6），分别含有1 M NaCl，在环境温度下，遵循我们之前研究中概述的程序。6为了制备壳聚糖和Dex表面，使用了以壳聚糖引发的五步或六步组装。尽管组装开始于壳聚糖，但起始聚合物不影响随后的交替生物活性。使用具有银电极的石英晶体微天平（QCM）作为主要基底，用于定量分析所得LbL组装体及其亚基。
Layer-by-layer (LbL) assembly1 permits the formation of ultrathin polymer films with a molecularly layered nanostructure and a nanometer-order thickness on surfaces. This process is based on the sequential deposition of interactive polymers from their solutions by electrostatic, 1 van der Waals, 2 hydrogen bonding, 3 and charge transfer4 interactions. LbL assembly is attractive for applications in biomedical fields since it facilitates the creation of uniquely functional material surfaces. Hubbell et al., for example, utilized LbL assembly to produce bioinert surfaces. 5 Alternating bioactivity, derived from the outermost surface of the LbL assembly, has not, however, been previously demonstrated, although alternate anti-vs pro-coagulant activity of human whole blood on a LbL assembly between chitosan and dextran sulfate (Dex) has been achieved. 6 This alternating activity was produced when the polymers were assembled from an aqueous solution containing 1 M NaCl. Since the addition of salt to the LbL assembly process facilitated formation of a thicker film, the intact characteristics of each polymer were apparently maintained. Accordingly, further alternation of bioactivity of LbL assemblies prepared under suitable conditions is expected. Deconstruction of LbL assemblies is attractive not only for analyzing stability of the assemblies but also for technological and biomedical applications of the assemblies. Disappearance of hydrogen bonds by changing pHs7 and of electrostatic interactions in high salt environments7c, 8 in LbL assemblies has deconstructed LbL assemblies. The biodegradability of ultrathin polymer films coated on material surfaces is one of the most important requirements for biomedical applications of these polymers. In the present study, we demonstrate the alternating enzymatic hydrolysis of an LbL assembly formed from chitosan and Dex. Chitosanase, an enzyme which hydrolyzes chitosan, was applied in this process. The chemical structures of the polymers are shown in Scheme 1.To realize alternating enzymatic hydrolysis, the LbL assembly between chitosan (Mw 1 200 000)(Wako, Japan) with 20% chitin units and Dex (Mw 500 000)(Wako, Japan) was carried out in aqueous solutions of 25% HCOOH (pH of solution) 1) and water (pH of solution) 6), respectively, containing 1 M NaCl at ambient temperature, following procedures outlined in our previous study. 6 To prepare the chitosan and Dex surfaces, the five-or six-step assembly, which was initiated with chitosan, was utilized. Although the assembly started with chitosan, the starting polymer did not affect the following alternating bioactivity. A quartz crystal microbalance (QCM) with a silver electrode was used as the main substrate for quantitative analysis of the resulting LbL assembly and its subse-