Physical Chemistry I, Department of Chemistry and Biology & Research Center of Micro and Nanochemistry and Engineering (Cμ), University of Siegen, 57076 Siegen, Germany.
Nanotechnology Research Center, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran 13169-43551, Iran.
ACS Appl Mater Interfaces. 2021 Mar 24;13(11):12928-12940. doi: 10.1021/acsami.1c00136. Epub 2021 Mar 12.
The fabrication of covalently cross-linked high-surface-area biopolymeric nanogel fibers by nanopore extrusion is reported for the first time. The biopolymer pullulan was functionalized with -butyl acetoacetate via a transesterification reaction to synthesize the water-soluble ketone-rich precursor pullulan acetoacetate (PUAA). PUAA and carbonic dihydrazide (CDH) as cross-linker were extruded through anodic aluminum oxide (AAO) nanoporous membranes, which possessed an average pore diameter of 61 ± 2 nm. By changing the concentration of PUAA, the flow rate, and extrusion time, the step polymerization cross-linking reaction was controlled so that the polymer can be extruded gradually during cross-linking through the membrane, avoiding the formation of macroscopic bulk hydrogels and rupture of the AAO membrane. Fibers with diameters on the order of 250 nm were obtained. This approach was also expanded to functionalized PUAA derivatives together with the fluorogenic substrate 4-methylumbelliferyl-β-d-glucuronide MUGlcU in (PUAA-MUGlcU), which exhibited a mean equilibrium swelling ratio of 5.7 and 9.0 in Milli-Q water and in phosphate-buffered saline, respectively. β-Glucuronidase was sensitively detected via fluorescence of 4-methylumbelliferone, which was liberated in the enzymatic hydrolysis reaction of PUAA-MUGlcU. Compared to hydrogel slabs, the rate of the hydrolysis was >20% higher in the nanogel fibers, facilitating the rapid detection of β-glucuronidase-producing ( Mach1-T1). Nanopore extruded nanogel fibers are therefore considered a viable approach to enhance the functionality of hydrogels in surface-dominated processes.
首次报道了通过纳米孔挤压制备共价交联的高表面积生物聚合物纳米凝胶纤维。通过酯交换反应，将生物聚合物普鲁兰用 - 丁基乙酰乙酸酯化，合成水溶性酮丰富的前体普鲁兰乙酰乙酸酯（PUAA）。PUAA 和作为交联剂的碳二酰肼（CDH）通过阳极氧化铝（AAO）纳米多孔膜挤出，其平均孔径为 61 ± 2nm。通过改变 PUAA 的浓度、流速和挤出时间，可以控制逐步聚合交联反应，使聚合物在通过膜交联时可以逐渐挤出，从而避免形成宏观块状水凝胶和 AAO 膜破裂。获得了直径约为 250nm 的纤维。这种方法还扩展到了功能化的 PUAA 衍生物以及荧光底物 4-甲基伞形酮-β-d-葡萄糖醛酸苷 MUGlcU 在（PUAA-MUGlcU）中，在 Milli-Q 水和磷酸盐缓冲盐水中的平衡溶胀比分别为 5.7 和 9.0。通过释放的 4-甲基伞形酮的荧光可以灵敏地检测到β-葡萄糖醛酸酶，这是在 PUAA-MUGlcU 的酶水解反应中释放出来的。与水凝胶板相比，纳米凝胶纤维中的水解速率提高了>20%，有利于快速检测β-葡萄糖醛酸酶产生的（Mach1-T1）。因此，纳米孔挤压纳米凝胶纤维被认为是增强水凝胶在表面主导过程中的功能的可行方法。
