Christian Doppler Laboratory for Advanced Polymers for Biomaterials and 3D Printing, TU Wien, Vienna 1060, Austria.
Institute of Applied Synthetic Chemistry, Division of Macromolecular Chemistry, TU Wien, Vienna 1060, Austria.
Langmuir. 2020 Nov 10;36(44):13292-13300. doi: 10.1021/acs.langmuir.0c02325. Epub 2020 Oct 29.
Achieving strong adhesion in wet environments remains a technological challenge in biomedical applications demanding biocompatibility. Attention for adhesive motifs meeting such demands has largely been focused on marine organisms. However, bioadhesion to inorganic surfaces is also present in the human body, in the hard tissues of teeth and bones, and is mediated through serines (S). The specific amino acid sequence DpSpSEEKC has been previously suggested to be responsible for the strong binding abilities of the protein statherin to hydroxyapatite, where pS denotes phosphorylated serine. Notably, similar sequences are present in the non-collagenous bone protein osteopontin (OPN) and the mussel foot protein 5 (Mefp5). OPN has previously been shown to promote fracture toughness and physiological damage formation. Here, we investigated the adhesion strength of the motif D(pS)(pS)EEKC on substrates of hydroxyapatite, TiO, and mica using atomic force microscopy (AFM) single-molecule force spectroscopy (SMFS). Specifically, we investigated the dependence of adhesion force on phosphorylation of serines by comparing findings with the unphosphorylated variant DSSEEKC. Our results show that high adhesion forces of over 1 nN on hydroxyapatite and on TiO are only present for the phosphorylated variant D(pS)(pS)EEKC. This warrants further exploitation of this motif or similar residues in technological applications. Further, the dependence of adhesion force on phosphorylation suggests that biological systems potentially employ an adhesion-by-demand mechanism via expression of enzymes that up- or down-regulate phosphorylation, to increase or decrease adhesion forces, respectively.
在需要生物相容性的生物医学应用中，实现在潮湿环境中的强附着力仍然是一项技术挑战。满足这些要求的粘附基序引起了广泛关注，主要集中在海洋生物上。然而，人体的无机表面也存在生物粘附，在牙齿和骨骼的硬组织中，这种粘附是通过丝氨酸（S）介导的。以前已经提出，DpSpSEEKC 特定氨基酸序列负责蛋白质牙本质蛋白与羟基磷灰石的强结合能力，其中 pS 表示磷酸化丝氨酸。值得注意的是，类似的序列存在于非胶原蛋白骨蛋白骨桥蛋白（OPN）和贻贝足蛋白 5（Mefp5）中。OPN 先前已被证明可促进骨折韧性和生理损伤形成。在这里，我们使用原子力显微镜（AFM）单分子力谱（SMFS）研究了 motif D(pS)(pS)EEKC 在羟基磷灰石、TiO 和云母基质上的粘附强度。具体来说，我们通过将结果与未磷酸化的变体 DSSEEKC 进行比较，研究了丝氨酸磷酸化对粘附力的依赖性。我们的结果表明，只有在磷酸化变体 D(pS)(pS)EEKC 上，才能在羟基磷灰石和 TiO 上产生超过 1 nN 的高粘附力。这为在技术应用中进一步开发这种基序或类似残基提供了依据。此外，粘附力对磷酸化的依赖性表明，生物系统可能通过表达上调或下调磷酸化的酶来采用按需粘附机制，以分别增加或减少粘附力。
