官能化奈米纖維作為交聯劑製備殼聚醣自癒合水凝膠與形狀記憶冷凍凝膠

Abstract

水凝膠是能夠吸收和保留大量水的聚合物網絡。冷凍凝膠是由單體或聚合物前體在適度冷凍的溶液中化學或物理交聯製成的大孔結構，具有高吸水性、結構耐久性和可壓縮性。關於形狀記憶冷凍凝膠的研究很少，也沒有冷凍凝膠基於纖維素交聯劑的研究。在這裡我們合成了具有醛基作為交聯劑的多功能奈米纖維 (MCNF)，以生產殼聚醣水凝膠和冷凍凝膠。水凝膠（固含量 < 2%）具有自癒合+（損傷後約 100% 癒合）和剪切稀化特性，已通過流變學驗證。通過動態力學分析，冷凍凝膠顯示出高吸水率 (> 4300%) 和良好的可壓縮性。水凝膠和冷凍凝膠都是可注射的（分別通過 27 號和 18 號針頭）。特別是，冷凍凝膠（奈米纖維素：殼聚醣 1:6）揭示了熱誘導的形狀記憶，其機制通過原位小角 X 射線散射 (SAXS) 和廣角 X 射線散射 (WAXS) 闡明在形狀記憶程序期間冷凍凝膠的誘導晶體結構的取向變化解釋了其形狀記憶特性。形狀記憶允許大尺寸（15 mm × 10 mm × 1.1 mm）的冷凍凝膠片材通過 16G 針頭注射，並在 37°C 水中恢復其原始形狀。奈米纖維素殼聚醣形狀記憶冷凍凝膠顯示出細胞相容性和促進細胞生長的能力。奈米纖維素-殼聚醣水凝膠和冷凍凝膠是可注射和可降解的生物材料，具備可調節的機械性能，未來有應用於精準醫療及微創手術之潛力。

Hydrogels are polymeric networks capable of absorbing and retaining large amounts of water. Cryogels are macroporous structures made of monomers or polymeric precursors chemically or physically crosslinked in moderately frozen solutions, and have high water absorption, structural durability, and compressibility. There are few studies on shape memory cryogel, and none is based on cellulose crosslinker. Here we synthesized multifunctional cellulose nanofibers (MCNFs) with aldehyde group as crosslinker to produce chitosan hydrogel and cryogel. The hydrogel (solid content < 2%) had self-healing (~100% healing after injury) and shear thinning properties, verified by rheology. The cryogel showed high water absorption (> 4300%) and good compressibility through dynamic mechanical analyses. The hydrogel and cryogel were both injectable (via 27-gauge and 18-gauge needles, respectively). In particular, the cryogel (nanocellulose:chitosan 1:6) revealed thermally-induced shape memory, of which the mechanism was elucidated by in situ small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS). Changes in the orientation of the induced crystalline structure of the cryogel during the shape memory program accounted for its shape memory property. The shape memory allowed the cryogel sheet with a large size (15 mm × 10 mm × 1.1 mm) to be injected through a 16G needle and return to its original shape in 37 °C water. The nanocellulose-chitosan shape memory cryogel showed cytocompatibility and the ability to promote cell growth. The nanocellulose-chitosan hydrogel and cryogel are injectable and degradable biomaterials with adjustable mechanical properties for precision medicine and minimally invasive surgery.