Nakahama Masashi, Reboul Julien, Yoshida Kenji, Furukawa Shuhei, Kitagawa Susumu
Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
J Mater Chem B. 2015 May 28;3(20):4205-4212. doi: 10.1039/c5tb00346f. Epub 2015 Apr 29.
We investigated the encapsulation of bioactive molecules such as l-glutamic acid (Glu) into a series of porous coordination polymers (PCPs) based on aluminum hydroxy dicarboxylates [Al(OH)(L)] (L = dicarboxylate ligand) and the molecular release therefrom. The use of 2,6-naphthalene dicarboxylate (2,6-ndc), 1,4-benzene dicarboxylate (1,4-bdc) and 1,4-naphthalene dicarboxylate (1,4-ndc) as ligands allows us to systematically tune the pore size and the flexibility of frameworks while keeping the same topology and thus to investigate the effect of those parameters upon both adsorption and release of Glu. We revealed the impact of zwitterionic nature of Glu upon loading efficiency; optimal loading pH was shown to be that for which Glu bears both positive and negative charges. Whereas the loading capacity of PCPs is governed by the pore size ([Al(OH)(2,6-ndc)] > [Al(OH)(1,4-bdc)] > [Al(OH)(1,4-ndc)]), the adsorption isotherm clearly revealed that small or flexible pores induce the stronger Glu-PCP interaction. The release experiments of Glu from PCPs in a physiological media (pH = 7.4, 37 °C) demonstrated the exceptional stabilization of Glu within [Al(OH)(1,4-bdc)], compared to those within the other frameworks; whereas the rigid frameworks of [Al(OH)(2,6-ndc)] and [Al(OH)(1,4-ndc)] spontaneously released almost the entire Glu contents within 10 h, 70% of Glu loaded within [Al(OH)(1,4-bdc)] still remained therein over 24 h. Interestingly, the burst release of Glu was triggered by increasing temperature up to 80 °C, at which the framework changed its structure from a closed phase to the open phase.
我们研究了将生物活性分子（如L-谷氨酸（Glu））封装到一系列基于羟基二羧酸铝[Al(OH)(L)]（L = 二羧酸配体）的多孔配位聚合物（PCP）中以及分子从其中释放的情况。使用2,6-萘二甲酸（2,6-ndc）、1,4-苯二甲酸（1,4-bdc）和1,4-萘二甲酸（1,4-ndc）作为配体，使我们能够在保持相同拓扑结构的同时系统地调节孔径和框架的柔韧性，从而研究这些参数对Glu吸附和释放的影响。我们揭示了Glu的两性离子性质对负载效率的影响；最佳负载pH值显示为Glu同时带有正电荷和负电荷的pH值。虽然PCP的负载能力受孔径控制（[Al(OH)(2,6-ndc)] > [Al(OH)(1,4-bdc)] > [Al(OH)(1,4-ndc)]），但吸附等温线清楚地表明，小的或柔性的孔会诱导更强的Glu-PCP相互作用。在生理介质（pH = 7.4，37 °C）中Glu从PCP的释放实验表明，与其他框架中的情况相比，Glu在[Al(OH)(1,4-bdc)]中具有异常的稳定性；而[Al(OH)(2,6-ndc)]和[Al(OH)(1,4-ndc)]的刚性框架在10小时内几乎自发释放了全部的Glu含量，负载在[Al(OH)(1,4-bdc)]中的70%的Glu在24小时内仍保留在其中。有趣的是，将温度升高到80 °C会引发Glu的突发释放，此时框架结构从封闭相转变为开放相。
