Photolithography-Mediated Area-Selective Immobilization of Biomolecules on Polydopamine Coating.

Functional microdomains consisting of multiple molecules have widespread applications. However, most of available methods reported so far have a common limitation for widespread practical use. Herein, we reported a facile method based on material-independent polydopamine surface chemistry to realize the area-selective immobilization of dual amine-/thiol-terminal bioactive molecules assisted by photolithography. We transferred the photoresist pattern to the polydopamine coating surface, and specific molecules were respectively covalently immobilized in the microdomain. The results demonstrated that molecular anchoring is area-selective and quantitatively controllable. Thus, this versatile method provides a new insight into the creation of regionally chemical multicomponent surfaces and could build a potential platform for promising application in sensors, molecular biology, and genetic diagnosis.

Metal-catechol-(amine) networks for surface synergistic catalytic modification: Therapeutic gas generation and biomolecule grafting.

Regarding the high requirement of cardiac and vascular implants in tissue engineering, a novel concept of surface chemistry strategy featuring multiple functions is proposed in this study, which provides glutathione peroxidase (GPx)-like catalytic activity and allows secondary reactions for grafting functional biomolecules. The suggested strategy is the fabrication of a metal-catechol-(amine) network (MCAN) containing copper ions with GPx-like activity, amine-bearing hexamethylenediamine (HD) and wet adhesive catechol dopamine (DA). With a simple one-step molecular/ion co-assembly, the developed copper-DA-HD (CuII-DA/HD) network can be used to catalyze the generation of therapeutic nitric oxide (NO) gas in a durable and dose-controllable manner. The primary amine groups in the CuII-DA/HD network facilitate the secondary immobilization of bivalirudin (BVLD) to further provide an antithrombotic activity as supplement to the functions of NO. The CuII-DA/HD + BVLD coating functionalized on cardiovascular stents successfully improved thromboresistance, anti-restenosis, and promotes re-endothelialization in vivo. With regard to the ease of operation and low cost, the synergetic modification using MCAN strategy is of great potential for developing multifunctional blood-contacting materials/devices.

A facile dopamine-mediated metal-catecholamine coating for therapeutic nitric oxide gas interface-catalytic engineering of vascular devices.

Developing a facile and versatile strategy to endow blood-contacting devices with surface in situ nitric oxide (NO) generation properties by catalytically decomposing endogenously existing S-nitrosothiols (RSNO) from blood is of immense scientific and engineering interest. However, most available strategies involve drawbacks of low efficiency, complex processes, and toxic chemicals. In this work, we report a facile method to deposit a NO-generating coating on a 316L stainless steel (SS) substrate through dopamine-mediated one-step assembly of CuII-dopamine (CuII-DA) coordination complexes. The chelation of CuII in the CuII-DA network endowed the coating with high in situ NO catalytic capacity by decomposing RSNO endogenously existing in blood. Of special importance is that this dopamine-mediated method possesses the merits of a simple preparation process, friendliness to the environment, high controllability of the CuII-DA surface chemistry, highly effective surface coating formation, and long-term and durable catalytic activity of NO. The continuous release of NO from the CuII-DA-coated 316L SS impressively improved its antithrombogenicity and selectively enhanced endothelial cell (EC) growth while inhibiting smooth muscle cell (SMC) proliferation.

Mussel-inspired catalytic selenocystamine-dopamine coatings for long-term generation of therapeutic gas on cardiovascular stents.

The development of a nitric oxide (NO)-generating surface with long-term, stable and controllable NO release improves the therapeutic efficacy of cardiovascular stents. In this work, we developed a "one-pot" method inspired by mussel adhesive proteins for copolymerization of selenocystamine (SeCA) and dopamine (Dopa) to form a NO-generating coating on a 316 L stainless steel (SS) stent. This "one-pot" method is environmentally friendly and easy to popularize, with many advantages including simple manufacturing procedure, high stability and no involvement of organic solvents. Such SeCA/Dopa coatings also enabled us to develop a catalytic surface for local NO-generation by reaction of endogenously existing S-nitrothiol species from fresh blood. We found that the developed SeCA/Dopa coatings could release NO in a controllable and stable manner for more than 60 days. Additionally, the released NO significantly inhibited smooth muscle cell (SMC) proliferation and migration, as well as platelet activation and aggregation through the up-regulation of cyclic guanosine monophosphate synthesis. Moreover, such NO generation enhanced the adhesion, proliferation and migration of endothelial cells (ECs), and achieved rapid in vivo re-endothelialization, effectively reducing in-stent restenosis and neointimal hyperplasia. We envision that the SeCA/Dopa-coated 316 L SS stent could be a promising platform for treatment of cardiovascular diseases.

Assembly of Metal-Phenolic/Catecholamine Networks for Synergistically Anti-Inflammatory, Antimicrobial, and Anticoagulant Coatings.

The development of a facile and versatile strategy to endow surfaces with synergistically anti-inflammatory, antimicrobial, and anticoagulant functions is of particular significance for blood-contacting biomaterials and medical devices. In this work, we report a simple and environmentally friendly "one-pot" method inspired by byssal cuticle chemistry, namely, [Fe(dopa)3] coordination chemistry for assembly of copper ions (Cu2+) and plant polyphenol (tannic acid)/catecholamine (dopamine or norepinephrine) to form metal-phenolic/catecholamine network-based coatings. This one-pot method enabled us to easily develop a multifunctional surface based on the combination of the characteristic functions of metal ions and plant polyphenol or catecholamine. The residual phenolic hydroxyl groups on the coatings imparted the modified surface with excellent antioxidant and anti-inflammatory functions. The robust chelation of copper ions to the metal-phenolic/catecholamine networks provided not only durable antibacterial property but also glutathione peroxidase like catalytic capability to continuously and controllably produce antithrombotic nitric oxide by catalyzing endogenous S-nitrothiol. The biological functions of such coatings could be well regulated by adjusting the ratios of the feed concentration of Cu2+ ions to plant polyphenol or catecholamine. We envision that our simple, multifunctional, and bioinspired coating strategy can hold great application promise for bioengineering blood-contacting devices.

Nitric oxide producing coating mimicking endothelium function for multifunctional vascular stents.

The continuous release of nitric oxide (NO) by the native endothelium of blood vessels plays a substantial role in the cardiovascular physiology, as it influences important pathways of cardiovascular homeostasis, inhibits vascular smooth muscle cell (VSMC) proliferation, inhibits platelet activation and aggregation, and prevents atherosclerosis. In this study, a NO-catalytic bioactive coating that mimics this endothelium functionality was presented as a hemocompatible coating with potential to improve the biocompatibility of vascular stents. The NO-catalytic bioactive coating was obtained by covalent conjugation of 3,3-diselenodipropionic acid (SeDPA) with glutathione peroxidase (GPx)-like catalytic activity to generate NO from S-nitrosothiols (RSNOs) via specific catalytic reaction. The SeDPA was immobilized to an amine bearing plasma polymerized allylamine (PPAam) surface (SeDPA-PPAam). It showed long-term and continuous ability to catalytically decompose endogenous RSNO and generate NO. The generated NO remarkably increased the cGMP synthesis both in platelets and human umbilical artery smooth muscle cells (HUASMCs). The surface exhibited a remarkable suppression of collagen-induced platelet activation and aggregation. It suppressed the adhesion, proliferation and migration of HUASMCs. Additionally, it was found that the NO catalytic surface significantly enhanced human umbilical vein endothelial cell (HUVEC) adhesion, proliferation and migration. The in vivo results indicated that the NO catalytic surface created a favorable microenvironment of competitive growth of HUVECs over HUASMCs for promoting re-endothelialization and reducing restenosis of stents in vivo.

A simple one-step modification of various materials for introducing effective multi-functional groups.

Covalent immobilization of various biomolecules is a desired strategy for bio-multifunctional surface modification. Multi-functionalization of a material surface is considered to be the premise of immobilizing a variety of biomolecules. However, currently adopted methods, used to introduce proper reactive functional groups on material surfaces, mostly are hard to be carried out and frequently can only introduce insufficient functional groups. In this work, we successfully develop the films (GAHD films) prepared via the simple copolymerization of gallic acid (GA) and hexamethylenediamine (HD), which can be deposited on different kinds of material surfaces including metals, ceramics and polymers by a one-step dip-coating method. Moreover, these copolymerized GAHD films possess high concentration of multi-functional groups like carboxyl (COOH), primary amine (-NH2) and quinone groups on the surfaces. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) results prove either the occurrence of Michael addition reaction, Schiff base reaction in the film-forming process, or the existence of COOH, NH2 and quinone groups on the surfaces. The maximum contents of carboxyl and amine on the GAHD film are 24.9 nmol/cm(2) and 31.7 nmol/cm(2) respectively. After dynamical immersion for 30 days, slight swellings can be observed, which reveals that the GAHD films possess good stability. Moreover, Heparin (Hep), fibronectin (Fn) and laminin (Ln) are successfully immobilized on the GAHD film surfaces. The results of cell counting kit-8 (CCK-8) and rhodamine fluorescence photograph indicate that the 1:1.62 GAHD film has good cytocompatibility.

A surface-eroding poly(1,3-trimethylene carbonate) coating for fully biodegradable magnesium-based stent applications: toward better biofunction, biodegradation and biocompatibility.

Biodegradable magnesium-based materials have a high potential for cardiovascular stent applications; however, there exist concerns on corrosion control and biocompatibility. A surface-eroding coating of poly(1,3-trimethylene carbonate) (PTMC) on magnesium (Mg) alloy was studied, and its dynamic degradation behavior, electrochemical corrosion, hemocompatibility and histocompatibility were investigated. The PTMC coating effectively protected the corrosion of the Mg alloy in the dynamic degradation test. The corrosion current density of the PTMC-coated alloy reduced by three orders and one order of magnitude compared to bare and poly(ε-caprolactone) (PCL)-coated Mg alloy, respectively. Static and dynamic blood tests in vitro indicated that significantly fewer platelets were adherent and activated, and fewer erythrocytes attached on the PTMC-coated surface and showed less hemolysis than on the controls. The PTMC coating after 16 weeks' subcutaneous implantation in rats maintained ~55% of its original thickness and presented a homogeneously flat surface demonstrating surface erosion, in contrast to the PCL coated control, which exhibited non-uniform bulk erosion. The Mg alloy coated with PTMC showed less volume reduction and fewer corrosion products as compared to the controls after 52 weeks in vivo. Excessive inflammation, necrosis and hydrogen gas accumulation were not observed. The homogeneous surface erosion of the PTMC coating from exterior to interior (surface-eroding behavior) and its charge neutral degradation products contribute to its excellent protective performance. It is concluded that PTMC is a promising candidate for a surface-eroding coating applied to Mg-based implants.

Biofunctionalization of titanium with PEG and anti-CD34 for hemocompatibility and stimulated endothelialization.

Thrombosis and restenosis are the main causes of failure of cardiovascular and other blood-contacting biomedical devices. It is recognized that rapid endothelialization is a promising method for preventing these complications. Convincing evidence in vivo has further emerged that the vascular homing of endothelial progenitor cells (EPCs) contributes to rapid endothelial regeneration. This study deals with improving the hemocompatibility and enhancing EPC colonization of titanium by covalently bonding PEG(600) or PEG(4000), then end-grafting of an anti-CD34 antibody. For this, a chemically hydroxylated titanium surface was aminosilanized, which was further used for covalent grafting of polyethylene glycol and the antibody. The grafting efficiency was verified in each step. In vitro platelet adhesion analysis confirmed superior hemocompatibility of the modified surface over the control. Affinity of EPC to the surface and inhibition of smooth muscle cell adhesion, two prerequisites for endothelialization, are demonstrated in in vitro cell culture. While the coating selectively stimulates EPC adhesion, its antifouling properties prevent formation of an extracellular matrix and proliferation of the cells. Additional affinity for matrix proteins in the coating is considered for further studies. Potent inhibitory effect on macrophage activation and the relative stability of the coating render this technique applicable.

Oriented immobilization of anti-CD34 antibody on titanium surface for self-endothelialization induction.

Inducing spontaneous endothelialization of synthetic cardiovascular implant in vivo is thought to be a promising approach to solve the surface-induced thrombosis and restenosis problem. In the present study, anti-CD34 antibody, a kind of special marker of EPC, was oriented immobilized on titanium surface by means of a layer-by-layer self-assembly coating technique. The multilayer coating was prepared by first depositing one layer of avidin on the NaOH-treated titanium substrate, then depositing a layer of biotinylated protein A binding to the avidin, and finally anti-CD34 antibody was oriented immobilized by protein A binding to the Fc fragment (COOH-terminal of a antibody molecule, which has no antigen binding sites) of the anti-CD34 antibody with its antigen binding fragment (Fab) away from the titanium surface. The coated titanium was exposed to EPC derived from mouse bone marrow in vitro, and implanted into dog femoral arteries. The results suggested that the anti-CD34 antibody immobilized surfaces could increase EPC attachment and capture, and induce rapid complete endothelialization of the lumenal surface of the implant in vivo. It suggests that the approach described here may be used for fabrication of titanium-based vascular implant surfaces for inducing endothelialization in vivo.