国产精品igao视频网网址不卡日韩,亚洲综合在线电影,亚洲婷婷丁香,黄色在线网站噜噜噜

  生物體內承載組織，大多具有較強的生物力學性能，但是其弱的自修復能力導致其在發生損傷時，很難恢復到原來的結構和性能，組織工程替代物是實現承載組織功能再生的有效措施。水凝膠作為一種軟濕材料，具有良好的生物相容性，在生物組織工程領域已經得到了廣泛的應用，然而，由于其較低的力學性能（弱的抗張強度，較低的楊氏模量以及較差的韌性等），以及在水環境中不穩定的缺點，限制了其在生物承載組織中的應用。近年來，高強水凝膠獲得了廣泛而又深入的研究，并且取得了一定的成果，然而，由于高強水凝膠相對較低的模量，限制了其在跟腱、半月板等高模量生物承載組織的應用，而目前高模量水凝膠制備的復雜性、耗時性以及水環境中的不穩定性等缺點，使其作為生物組織替代物的研究更是鮮有報道。因此，設計一種簡單有效地制備高強、高模量水凝膠，并能夠在水中、PBS中保持穩定的水凝膠的方法仍然存在很大的挑戰。

  基于上述考慮，天津大學劉文廣教授團隊提出了一種力學“增強因子”的概念，通過一種全新的氫鍵單體NASC（只將已報道的NAGA側鏈兩個酰胺間的CH2換成NH，使NASC側鏈帶有一個酰胺鍵和一個脲基）的設計與合成，成功制備了PNASC超分子聚合物水凝膠。由于側鏈強的氫鍵交聯作用，溶脹平衡之后的超分子聚合物水凝膠的拉伸強度可達1.7-4.7 MPa，楊氏模量達48.4-100.3 MPa，斷裂應變達341-638%，韌性可達5.66-20.35 MJ m^-3，遠高于迄今為止報道的超分子聚合物水凝膠 （Fig. 1），該團隊對于PNASC水凝膠力學增強機制進行了探索。

Fig. 1. (a): Molecular structures of NAGA, NASC, PNAGA and PNASC. (b): Schematic illustration of reconstruction of hydrogen bonding of amide and urea in PNASC gels when DMSO is replaced with water. (c): Tensile stress-strain curves. (d): Tensile strength, Young’s modulus and yielding strength of PNASC hydrogels with different initial monomer concentrations (n=3). (e, f, g) Photos portraying the high stiffness of the PNASC-25 hydrogels. (e): 79 g of aluminum sheets can be lifted up by a length of hydrogel line (d=0.6 mm) without stretching, and nylon cord is threaded through a hole in a piece of PNASC-25 hydrogel sheet (3 cm × 1.5 cm × 0.2 cm) and lifts a bottle of water weighing 0.9 kg without occurrence of deformation of the hydrogel hole. The hydrogel sheet (3 cm × 2.5 cm × 0.2 cm) was able to bear self-weight (f) and 70 g of aluminum sheets without collapse (g).

  此外，值得注意的是，該單體可以與AAm，CBAA等代表性的單體共聚制備具有一定力學強度且在PBS中保持穩定的超分子聚合物水凝膠。為了探索PNASC基水凝膠的應用，該團隊將單體NASC與接雙鍵的肝素共聚，制備P(NASC-co-HepMAm) 共聚水凝膠微管，該水凝膠在37 ℃可以保持高的模量，并且具有良好的生物相容性和血液相容性，肝素的引入提高了其抗凝血性能，使其有望作為臨時血管用于野外突發事故導致的血管破裂而引起的肢體缺血的救治，對于緊急情況下的受傷肢體的血液快速恢復具有潛在的應用價值 (Fig. 2)。

Fig. 2. (a) Schematic illustration of the fabrication of P(NASC-co-HepMAm) hydrogel tubes and their application as the TIVS in vivo. (b) Sequential steps in placement of hydrogel tube for TIVS in a rabbit model: (1) The rabbit’s arteria carotis was clamped on both sides by the artery clamp; (2) Defective treatment of blood vessels located between two arterial clips; (3) One end of the trimmed hydrogel tube was inserted into the rabbit’s carotid artery (3-4 mm depth) through the defect; (4, 5) Another end of the hydrogel tube was trimmed and the rabbit carotid artery was amputated; immediately, this end of the trimmed hydrogel tube was inserted into rabbit carotid artery (3-4 mm); (6) The arterial clip was removed to restore the blood flow. (c) (1, 7), (2, 8), (3, 9), and (4, 10) are the photos of blood color change in the PNASC-25 and P(NASC-co-HepMAm)-25-15 hydrogel tubes after being implanted for 0, 1, 2, and 4 h. (5, 11) are the photos of the PNASC-25 and P(NASC-co-HepMAm)-25-15 hydrogel tubes removed from the end of arteria carotis. (6, 12) Stereomicroscopic images of the PNASC-25 and P(NASC-co-HepMAm)-25-15 hydrogel tube luminal surface.

  這項研究開辟了一種非常簡單且通用的制備具有特定功能的高強度、高剛度、高韌性以及溶脹穩定的超分子聚合物水凝膠的策略，對于其在承載組織的應用中具有重要的意義。

  目前上述工作已發表在《Materials Horizons》上，論文第一作者為天津大學材料學院博士生范川川，通訊作者為天津大學材料學院劉文廣教授。

  論文鏈接：https://pubs.rsc.org/en/content/articlelanding/2020/mh/c9mh01844a#!divAbstract