Amity Institute of Click Chemistry Research & Studies, Amity University Uttar Pradesh, Noida 201313, India.
Stem Cells Facility, DBT-Centre of Excellence, All India Institute of Medical Sciences, New Delhi 110029, India.
Biomed Mater. 2022 Sep 15;17(6). doi: 10.1088/1748-605X/ac8e43.
Nanoconfinement within flexible interfaces is a key step towards exploiting confinement effects in several biological and technological systems wherein flexible 2D materials are frequently utilized but are arduous to prepare. Hitherto unreported, the synthesis of 2D hydrogel nanosheets (HNSs) using a template- and catalyst-free process is developed representing a fertile ground for fundamental structure-property investigations. In due course of time, nucleating folds propagating along the edges trigger co-operative deformations of HNS generating regions of nanoconfinement within trapped water islands. These severely constricting surfaces force water molecules to pack within the nanoscale regime of HNS almost parallel to the surface bringing about phase transition into puckered rhombic ice with AA and AB Bernal stacking pattern, which was mostly restricted to molecular dynamics studies so far. Interestingly, under high lateral pressure and spatial inhomogeneity within nanoscale confinement, bilayer rhombic ice structures were formed with an in-plane lattice spacing of 0.31 nm. In this work, a systematic exploration of rhombic ice formation within HNS has been delineated using high-resolution transmission electron microscopy, and its ultrathin morphology was examined using atomic force microscopy. Scanning electron microscopy images revealed high porosity while mechanical testing presented young's modulus of 155 kPa with ∼84% deformation, whereas contact angle suggested high hydrophilicity. The combinations of nanosheets, porosity, nanoconfinement, hydrophilicity, and mechanical strength, motivated us to explore their application as a scaffold for cartilage regeneration, by inducing chondrogenesis of human Wharton Jelly derived mesenchymal stem cells. HNS promoted the formation of cell aggregates giving higher number of spheroid formation and a marked expression of chondrogenic markers (ColI, ColII, ColX, ACAN and S-100), thereby providing some cues for guiding chondrogenic differentiation.
在柔性界面内的纳米限域是利用若干生物和技术系统中限域效应的关键步骤，其中经常使用柔性 2D 材料，但难以制备。迄今为止，尚未有报道使用无模板和无催化剂的方法合成 2D 水凝胶纳米片（HNS），这为基础结构-性能研究提供了肥沃的土壤。随着时间的推移，沿着边缘传播的成核褶皱引发 HNS 的协同变形，在被困水岛内产生纳米限域区域。这些严重的约束表面迫使水分子在 HNS 的纳米范围内几乎与表面平行排列，从而导致相变为 AA 和 AB Bernal 堆积模式的褶皱菱形冰，迄今为止，这种相转变主要局限于分子动力学研究。有趣的是，在纳米限域内的高侧向压力和空间非均质性下，形成了具有 0.31nm 面内晶格间距的双层菱形冰结构。在这项工作中，使用高分辨率透射电子显微镜系统地研究了 HNS 内菱形冰的形成，并使用原子力显微镜研究了其超薄形貌。扫描电子显微镜图像显示出高孔隙率，而机械测试显示杨氏模量为 155kPa，变形率约为 84%，而接触角表明高亲水性。纳米片、孔隙率、纳米限域、亲水性和机械强度的结合促使我们探索它们在软骨再生支架中的应用，通过诱导人 Wharton 果冻来源间充质干细胞的软骨生成。HNS 促进了细胞聚集体的形成，形成了更高数量的球体形成和明显的软骨生成标志物（ColI、ColII、ColX、ACAN 和 S-100）的表达，从而为指导软骨分化提供了一些线索。
