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Surface-adherent polydopamine (PDA) films as multifunctional coatings can be easily deposited onto a wide range of materials through dopamine self-polymerization. However, a lack of in-depth understanding of PDA aggregation and deposition processes and definite structure elucidation of PDA make it challenging to tailor the surface characteristic and functionality of the PDA films. Herein, we demonstrate that the surface characteristics of the PDA films can be readily tuned by controlling the competitive interplay between PDA aggregation in solution and deposition on the substrate. Moreover, a structural investigation of the PDA films using analytical tools such as X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) allows us to propose a new structure model for the PDA building block. The (DHI)2/PCA trimer complex, which consists of two 5,6-dihydroxyindole (DHI) units and one pyrrolecarboxylic acid (PCA) moiety, is definitely identified as a primary building block of PDA, and its formation is steered by covalent interactions in the initial stages of polymerization. In latter stages, the (DHI)2/PCA trimer complexes are further linked primarily through noncovalent interactions to build up the supramolecular structure of PDA. This study provides new insights into the mechanisms of PDA buildup.

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Recent investigations have demonstrated that polydopamine (PDA)-modified surfaces were beneficial to the proliferation of endothelial cells (ECs). In this work, PDA coated 316L stainless steels (316L SS) were thermally treated at 50, 100, and 150 °C respectively (hereafter designated as Th50, Th100, and Th150) and consequently produced diverse surface chemical components. In vitro hemocompatibility and vascular cell-material interactions with ECs and smooth muscle cells (SMCs) affected by surface characteristics have been investigated. The Th150, rich in quinone, showed the best hemocompatibility and could effectively inhibit platelet adhesion, activation, and fibrinogen conformation transition. The polydopamine-modified surfaces were found to induce dramatic cell-material interaction with enhanced ECs proliferation, viability and migration, release of nitric oxide (NO), and reduced SMCs proliferation. The inhibitory effect of SMCs proliferation might be associated with the surface catechol content. The coating on Th150 showed a good resistance to the deformation of compression and expansion of vascular stents. These results effectively suggested that the Th150 coating might be promising when served as a stent coating platform.

A one-step method to deposit a functional amine-rich coating in dopamine and hexamethylendiamine mixed solution through simple dip-coating of objects.

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Polydopamine (PDAM), a mussel adhesive protein inspired coating that can be easily deposited onto a wide range of metallic, inorganic, and organic materials, gains interest also in the field of biomaterials. In this work, PDAM is applied as coating on 316L stainless steel (SS) stents and the response of cells of the blood vessel wall, human umbilical vein endothelial cell (HUVEC), and human umbilical artery smooth muscle cell (HUASMC) as predictors for re‐endothelialization is tested. It is found that the PDAM‐modified surface significantly enhances HUVEC adhesion, proliferation, and migration, release of nitric oxide (NO), and secretion of prostaglandin I2 (PGI2). Additionally, the PDAM‐modified surface shows a remarkable ability to decrease the adhesion and proliferation of HUASMCs. As a blood‐contacting material, the PDAM tends to improve the hemocompatibility compared with the substrate 316L SS. It is noteworthy that the PDAM coating shows good resistance to the deformation behavior of compression and expansion of a stent. These data suggest the potential of PDAM as a blood‐contacting material for the application in vascular stents or grafts.