Branch Bioanalytics and Bioprocesses (Fraunhofer IZI-BB), Fraunhofer Institute for Cell Therapy and Immunology , Am Muehlenberg 13, 14476 Potsdam-Golm, Germany.
School of Science and Technology, Nottingham Trent University , Clifton Lane, NG11 8NS Nottingham, U.K.
ACS Appl Mater Interfaces. 2017 Nov 8;9(44):38908-38918. doi: 10.1021/acsami.7b12449. Epub 2017 Oct 24.
Biopolymer-based multilayers become more and more attractive due to the vast span of biological application they can be used for, e.g., implant coatings, cell culture supports, scaffolds. Multilayers have demonstrated superior capability to store enormous amounts of small charged molecules, such as drugs, and release them in a controlled manner; however, the binding mechanism for drug loading into the multilayers is still poorly understood. Here we focus on this mechanism using model hyaluronan/polylysine (HA/PLL) multilayers and a model charged dye, carboxyfluorescein (CF). We found that CF reaches a concentration of 13 mM in the multilayers that by far exceeds its solubility in water. The high loading is not related to the aggregation of CF in the multilayers. In the multilayers, CF molecules bind to free amino groups of PLL; however, intermolecular CF-CF interactions also play a role and (i) endow the binding with a cooperative nature and (ii) result in polyadsorption of CF molecules, as proven by fitting of the adsorption isotherm using the BET model. Analysis of CF mobility in the multilayers by fluorescence recovery after photobleaching has revealed that CF diffusion in the multilayers is likely a result of both jumping of CF molecules from one amino group to another and movement, together with a PLL chain being bound to it. We believe that this study may help in the design of tailor-made multilayers that act as advanced drug delivery platforms for a variety of bioapplications where high loading and controlled release are strongly desired.
由于其在生物应用方面的广泛应用前景，基于生物聚合物的多层膜变得越来越有吸引力，例如，植入物涂层、细胞培养支持物、支架。多层膜具有存储大量小电荷分子（如药物）的卓越能力，并以可控的方式释放它们；然而，药物加载到多层膜中的结合机制仍不清楚。在这里，我们使用模型透明质酸/聚赖氨酸（HA/PLL）多层膜和模型带电荷的染料羧基荧光素（CF）来关注这种机制。我们发现 CF 在多层膜中的浓度达到 13mM，远远超过其在水中的溶解度。高负载与 CF 在多层膜中的聚集无关。在多层膜中，CF 分子与 PLL 的游离氨基结合；然而，分子间 CF-CF 相互作用也起作用，（i）赋予结合协同性质，（ii）导致 CF 分子的多吸附，如通过 BET 模型拟合吸附等温线证明。通过光漂白后荧光恢复分析 CF 在多层膜中的迁移性表明，CF 在多层膜中的扩散可能是 CF 分子从一个氨基跳跃到另一个氨基的结果，以及与结合的 PLL 链一起移动的结果。我们相信，这项研究可能有助于设计定制的多层膜，作为各种生物应用的先进药物输送平台，这些应用强烈需要高负载和可控释放。
