Mejia-Ariza Raquel, Huskens Jurriaan
Molecular Nanofabrication Group, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands.
J Mater Chem B. 2016 Feb 14;4(6):1108-1115. doi: 10.1039/c5tb01949d. Epub 2016 Jan 11.
The surface functionalization of MOF particles with poly(ethylene glycol) (PEG) is important for their use in biomedical applications. Here, the effect of the molecular weight of a monovalent PEG-carboxylate capping ligand (MW) was investigated in a newly developed one-step, stoichiometric procedure that aims at functionalizing MIL-88A particles and achieving size control at the same time. The bulk of the MIL-88A particles is composed of iron(iii) oxide metal clusters connected by fumaric acid as the organic ligand. The surface is functionalized with monovalent PEG-carboxylate capping ligands of different lengths. The size of the PEG-functionalized MIL-88A decreased with increasing MW, and nanoMOFs were obtained for long (≥2 kDa) PEG chains. For lower MW, higher concentrations of PEG were needed to obtain the maximum size effect, but the resulting sizes were still larger than for long PEGs. BET surface area, elemental analysis, zeta potential, and infrared spectroscopy measurements showed that the PEG chains were attached to the surface of the MOF particles and not in their interior. Moreover, it was demonstrated that longer chains occupy a larger surface area, and the PEG chains adopt the low-density brush conformation. Uptake and release experiments with sulforhodamine B dye (as a model drug) showed a higher and faster uptake and release for MIL-88A functionalized with PEG (20 kDa) than for native MIL-88A, which is attributed to a larger surface-to-volume ratio for the PEG-covered particles, and to the well-hydrated and accessible nature of the PEG layer in an aqueous medium. Complete release of the dye was achieved in phosphate buffered saline, the majority by counter ion exchange, and a smaller fraction in the salt form.
用聚乙二醇（PEG）对金属有机框架（MOF）颗粒进行表面功能化对于其在生物医学应用中的使用非常重要。在此，在一种新开发的一步法化学计量程序中研究了单价PEG - 羧酸盐封端配体的分子量（MW）的影响，该程序旨在对MIL - 88A颗粒进行功能化并同时实现尺寸控制。MIL - 88A颗粒的主体由通过富马酸作为有机配体连接的氧化铁（III）金属簇组成。表面用不同长度的单价PEG - 羧酸盐封端配体进行功能化。PEG功能化的MIL - 88A的尺寸随着MW的增加而减小，对于长（≥2 kDa）PEG链获得了纳米MOF。对于较低的MW，需要更高浓度的PEG才能获得最大尺寸效应，但所得尺寸仍比长PEG的尺寸大。比表面积、元素分析、zeta电位和红外光谱测量表明PEG链附着在MOF颗粒的表面而不是其内部。此外，证明了较长的链占据更大的表面积，并且PEG链采用低密度刷状构象。用磺基罗丹明B染料（作为模型药物）进行的摄取和释放实验表明，用PEG（20 kDa）功能化的MIL - 88A比天然MIL - 88A具有更高和更快的摄取和释放，这归因于PEG覆盖颗粒的更大的表面体积比，以及PEG层在水性介质中良好的水合性和可及性。在磷酸盐缓冲盐水中实现了染料的完全释放，大部分是通过反离子交换，较小部分是以盐的形式。
