Li Tianjie, Hao Lijing, Li Jiangyu, Du Chang, Wang Yingjun
Department of Biomedical Engineering, School of Materials Science and Engineering, South China University of Technology, Guangzhou, 510641, PR China.
National Engineering Research Center for Tissue Restoration and Reconstruction, PR China.
Bioact Mater. 2020 Jul 11;5(4):1044-1052. doi: 10.1016/j.bioactmat.2020.06.021. eCollection 2020 Dec.
Biomaterial surface chemistry engenders profound consequences on cell adhesion and the ultimate tissue response by adsorbing proteins from extracellular matrix, where vitronectin (Vn) is involved as one of the crucial mediator proteins. Deciphering the adsorption behaviors of Vn in molecular scale provides a useful account of how to design biomaterial surfaces. But the details of structural dynamics and consequential biological effect remain elusive. Herein, both experimental and computational approaches were applied to delineate the conformational and orientational evolution of Vn during adsorption onto self-assembled monolayers (SAMs) terminating with -COOH, -NH, -CH and -OH. To unravel the interplay between cell binding and the charge and wettability of material surface, somatomedin-B (SMB) domain of Vn holding the RGD cell-binding motif was employed in molecular dynamics (MD) simulations, with orientation initialized by Monte Carlo (MC) method. Experimental evidences including protein adsorption, cell adhesion and integrin gene expressions were thoroughly investigated. The adsorption of Vn on different surface chemistries showed very complex profiles. Cell adhesion was enabled on all Vn-adsorbed surfaces but with distinct mechanisms mostly determined by conformational change induced reorientation. Higher amount of Vn was observed on negatively charged surface (COOH) and hydrophobic surface (CH). However, advantageous orientations defined by RGD loop conditions were only obtained on the charged surfaces (COOH and NH). Specifically, COOH surface straightened up the Vn molecules and accumulated them into a higher density, whereas CH surface squashed Vn and stacked them into higher density multilayer by tracking adsorption but with the RGD loops restrained. These findings may have a broad implication on the understanding of Vn functionality and would help develop new strategies for designing advanced biomaterials.
生物材料表面化学通过吸附细胞外基质中的蛋白质，对细胞黏附以及最终的组织反应产生深远影响，其中玻连蛋白（Vn）是关键的介导蛋白之一。在分子尺度上解析Vn的吸附行为有助于了解如何设计生物材料表面。但其结构动力学细节及相应的生物学效应仍不清楚。在此，采用实验和计算方法来描述Vn在吸附到以 -COOH、-NH、-CH 和 -OH 终止的自组装单分子层（SAMs）上时的构象和取向演变。为了揭示细胞结合与材料表面电荷和润湿性之间的相互作用，在分子动力学（MD）模拟中使用了具有RGD细胞结合基序的Vn的生长调节素-B（SMB）结构域，其取向由蒙特卡罗（MC）方法初始化。对包括蛋白质吸附、细胞黏附及整合素基因表达在内的实验证据进行了深入研究。Vn在不同表面化学性质上的吸附呈现出非常复杂的情况。在所有Vn吸附的表面上都能实现细胞黏附，但机制不同，主要由构象变化诱导的重新取向决定。在带负电荷的表面（COOH）和疏水表面（CH）上观察到较高量的Vn。然而，仅在带电表面（COOH和NH）上获得了由RGD环条件定义的有利取向。具体而言，COOH表面使Vn分子伸直并将它们聚集到更高密度，而CH表面挤压Vn并通过跟踪吸附将它们堆叠成更高密度的多层，但RGD环受到限制。这些发现可能对理解Vn的功能具有广泛意义，并有助于开发设计先进生物材料的新策略。
