Lyu Qinghua, Song Hongyan, Yakovlev Nikolai L, Tan Wui Siew, Chai Christina L L
Department of Pharmacy, National University of Singapore 18 Science Drive 4 Singapore 117543
Institute of Materials Research and Engineering ASTAR, 2 Fusionopolis Way Singapore 138634
RSC Adv. 2018 Aug 3;8(49):27695-27702. doi: 10.1039/c8ra04472d. eCollection 2018 Aug 2.
The biomimetic coating polydopamine (PDA) has emerged as a promising coating material for various applications. However, the mechanism of PDA deposition onto surfaces is not fully understood, and the coating components of PDA and its relation to the putative intermediate 5,6-dihydroxyindole (DHI) are still controversial. This investigation discloses the deposition mechanisms of dopamine (DA)-based coatings and DHI-based coatings onto silicon surfaces by monitoring the nanoscale deposition of both coatings using high-precision ellipsometry. We posit that the rapid and instantaneous nano-deposition of PDA coatings onto silicon surface in the initial stages critically involves the oxidation of DHI and/or its related oligomers. Our studies also show that the slow conversion of DA to DHI in PDA solution and the coupling between DA and DHI-derived precursors could be crucial for subsequent PDA coating growth. These findings elucidate the critical role of DHI, acting as an 'initiator' and a 'cross linker', in the PDA coating formation. Overall, our study provides important information on the early stage nano-deposition behavior in the construction of PDA coatings and DHI-based coatings.
仿生涂层聚多巴胺（PDA）已成为一种适用于各种应用的有前景的涂层材料。然而，PDA在表面上的沉积机制尚未完全理解，并且PDA的涂层成分及其与假定中间体5,6-二羟基吲哚（DHI）的关系仍存在争议。本研究通过使用高精度椭偏仪监测两种涂层的纳米级沉积，揭示了多巴胺（DA）基涂层和DHI基涂层在硅表面上的沉积机制。我们认为，在初始阶段PDA涂层在硅表面上的快速且瞬时的纳米沉积关键涉及DHI和/或其相关低聚物的氧化。我们的研究还表明，PDA溶液中DA向DHI的缓慢转化以及DA与DHI衍生前体之间的偶联对于随后的PDA涂层生长可能至关重要。这些发现阐明了DHI作为“引发剂”和“交联剂”在PDA涂层形成中的关键作用。总体而言，我们的研究为PDA涂层和DHI基涂层构建中的早期纳米沉积行为提供了重要信息。
