Qiufen Tu

In Vitro Investigation of Enhanced Hemocompatibility and Endothelial Cell Proliferation Associated with Quinone-Rich Polydopamine Coating

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.

Mussel‐Inspired Coating of Polydopamine Directs Endothelial and Smooth Muscle Cell Fate for Re‐endothelialization of Vascular Devices

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 I(2) (PGI(2) ). 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.

Improved immobilization of biomolecules to quinone-rich polydopamine for efficient surface functionalization

Polydopamine (PDA), a bio-inspired polymer, has been very attractive for diverse functional applications by immobilizing biomolecules. In this work, a novel approach of using PDA for improved biomolecule immobilization was developed. A thin PDA layer was strategically coated onto 316L stainless steel and thermally treated at 150°C (PDA-Th150). Subsequently, amino-terminated polyethylene glycol (mPEG-NH2) or vascular endothelial growth factor (VEGF) was immobilized onto PDA and PDA-Th150 surface. The results of attenuated total reflection-Fourier transform-infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) showed higher coverage of quinine on PDA-Th150 surface. The functionalized PDA-Th150 significantly improved its ability of immobilizing mPEG-NH2 or VEGF, as shown by platelet adhesion test and endothelial cell proliferation experiments. This novel approach may also be used for efficient immobilization of biomolecules on different metal devices.

Mussel-inspired one-step adherent coating rich in amine groups for covalent immobilization of heparin: hemocompatibility, growth behaviors of vascular cells, and tissue response.

Heparin, an important polysaccharide, has been widely used for coatings of cardiovascular devices because of its multiple biological functions including anticoagulation and inhibition of intimal hyperplasia. In this study, surface heparinization of a commonly used 316L stainless steel (SS) was explored for preparation of a multifunctional vascular stent. Dip-coating of the stents in an aqueous solution of dopamine and hexamethylendiamine (HD) (PDAM/HD) was presented as a facile method to form an adhesive coating rich in primary amine groups, which was used for covalent heparin immobilization via active ester chemistry. A heparin grafting density of about 900 ng/cm(2) was achieved with this method. The retained bioactivity of the immobilized heparin was confirmed by a remarkable prolongation of the activated partial thromboplastin time (APTT) for about 15 s, suppression of platelet adhesion, and prevention of the denaturation of adsorbed fibrinogen. The Hep-PDAM/HD also presented a favorable microenvironment for selectively enhancing endothelial cell (EC) adhesion, proliferation, migration and release of nitric oxide (NO), and at the same time inhibiting smooth muscle cell (SMC) adhesion and proliferation. Upon subcutaneous implantation, the Hep-PDAM/HD exhibited mitigated tissue response, with thinner fibrous capsule and less granulation formation compared to the control 316L SS. This number of unique functions qualifies the heparinized coating as an attractive alternative for the design of a new generation of stents.

Direct thrombin inhibitor-bivalirudin functionalized plasma polymerized allylamine coating for improved biocompatibility of vascular devices

The direct thrombin inhibitor of bivalirudin (BVLD), a short peptide derived from hirudin, has drawn an increasing attention in clinical application because it is safer and more effective than heparin for diabetic patients with moderate- or high-risk for acute coronary syndromes (ACS). In this study, BVLD was covalently conjugated on plasma polymerized allylamine (PPAam) coated 316L stainless steel (SS) to develop an anticoagulant surface. QCM-D real time monitoring result shows that 565±20 ng/cm2 of BVLD was bound to the PPAam surface. Infrared spectroscopy (IR) and X-ray photoelectron spectroscopy (XPS) confirmed the immobilization of BVLD. The conjugation of BVLD onto the PPAam coating led to enhanced binding of thrombin, and the activity of the thrombin adsorbed on its surface was effectively inhibited. As a result, the BVLD immobilized PPAam (BVLD-PPAam) substrate prolonged the clotting times, and exhibited inhibition in adhesion and activation of platelets and fibrinogen. We also found that the BVLD-PPAam coating significantly enhanced endothelial cell adhesion, proliferation, migration and release of nitric oxide (NO) and secretion of prostaglandin I2 (PGI2). In vivo results indicate that the BVLD-PPAam surface restrained thrombus formation by rapidly growing a homogeneous and intact endothelium on its surface. These data suggest the potential of this multifunctional BVLD-PPAam coating for the application not only in general vascular devices such as catheters, tubes, oxygenator, hemodialysis membranes but also vascular grafts and stents.

Immobilization of DNA aptamers via plasma polymerized allylamine film to construct an endothelial progenitor cell-capture surface.

The endothelial progenitor cells (EPCs) capture stent has drawn increasing attentions and become one of the most promising concepts for the next generation vascular stent. In this regard, it is of great significance to immobilize a molecule with the ability to bind EPC for rapid in vivo endothelialization with high specificity. In this work, a facile two-step method aimed at constructing a coating with specific EPC capturing aptamers is reported. The processes involves as the first-step deposition of plasma polymerized allylamine (PPAam) on a substrate to introduce amine groups, followed by the electrostatic adsorption of a 34 bases single strand DNA sequence to the PPAam surface as a second step (PPAam-DNA). Grazing incidence attenuated total reflection Fourier transform infrared spectroscopy (GATR-FTIR) and X-ray photoelectron spectroscopy (XPS) confirmed the successful immobilization of the aptamers. Quartz crystal microbalance with dissipation (QCM-D) real time monitoring result shows that about 175 ng/cm(2) aptamers were conjugated onto the PPAam surface. The interactions between the modified surfaces and human umbilical vein endothelial cells (ECs), smooth muscle cells (SMCs), and murine induced EPCs derived from mesenchymal stem cells (MSCs) were also investigated. It was demonstrated that PPAam-DNA samples could capture more EPCs, and present a cellular friendly surface for the proliferation of both EPCs and ECs but no effect on the hyperplasia of SMCs. Also, the co-culture results of 3 types of cells confirmed that the aptamer could specifically bond EPCs rather than ECs and SMCs, suggesting the competitive adhesion advantage of EPCs to ECs and SMCs. These data demonstrate that the EPC aptamer has large potential for designing an EPC captured stent and other vascular grafts with targeted in situ endothelialization.

Tailoring of the titanium surface by preparing cardiovascular endothelial extracellular matrix layer on the hyaluronic acid micro-pattern for improving biocompatibility

It has been proved that high molecular weight hyaluronic acid (HMW-HA, 1×10(6) Da) micro-strips on titanium (Ti) surface can elongate the human vascular endothelial cell (EC) morphology, subsequently enhance endothelial extracellular matrix (ECM) deposition in our previous work. The HMW-HA micro-strips were anticipated to possess good hemocompatibility and EC compatibility simultaneously. However, the single HMW-HA micro-strips on Ti substrate showed bad hemocompatibility. To solve this problem, a method combining HA micro-pattern and EC decellularization was developed, and the endothelial extracellular matrix layer on the HA micro-pattern (ECM/HAP) showed excellent hemocompatibility and endothelial progenitor cells (EPCs) compatibility (cell number: 14.3±0.5×10(5) cells/cm2>2.2±0.7×10(5) cells/cm2 on ECM/TiOH, 7.5±1.3×10(5) cells/cm2 on TiOH, 3.4±0.9×10(5) cells/cm2 on TiOH/HAP and 3.6±1.2×10(5) cells/cm2 on Ti). We also found that the ECM/HAP coating could significantly inhibit the excessive proliferation of smooth muscle cells (SMCs) (cck-8 absorption: 0.25±0.06<1.18±0.09 A.U. on ECM/TiOH, 0.87±0.15 A.U. on TiOH and 1.55±0.11 A.U. on Ti) and the attachment of macrophages (cell number: 1.3±0.1×10(3)<9.2±1.5×10(3) cells/cm2 on ECM/TiOH, 8.8±0.3×10(3) cells/cm2 on TiOH, 7.3±0.7×10(3) cells/cm2 on TiOH/HAP and 9.6±0.9×10(3) cells/cm2 on Ti in 12 h). These data suggest that the multifunctional ECM/HAP coating can be used to build the bionic human endothelial ECM on the biomaterials surface, which might provide a potential and effective method for surface modification of cardiovascular devices.

Biomimetic modification of metallic cardiovascular biomaterials: from function mimicking to endothelialization in vivo.

Biosystem–surface interactions play an important role in various biological events and determine the ultimate functionality of implanted devices. Endothelialization or mimicking of endothelium on the surface of cardiovascular materials is a promising way to solve the problems of material-induced thrombosis and restenosis. Meanwhile, a multifunctional surface design is needed as antithrombotic properties should be considered in the period when the implants are not yet completely endothelialized. In this article, we summarize some successful approaches used in our laboratory for constructing multifunctional endothelium-like surfaces on metallic cardiovascular biomaterials through chemical modification of the surface or by the introduction of specific biological molecules to induce self-endothelialization in vivo. Some directions on future research in these areas are also presented.

Gallic Acid Tailoring Surface Functionalities of Plasma-Polymerized Allylamine-Coated 316L SS to Selectively Direct Vascular Endothelial and Smooth Muscle Cell Fate for Enhanced Endothelialization

The creation of a platform for enhanced vascular endothelia cell (VEC) growth while suppressing vascular smooth muscle cell (VSMC) proliferation offers possibility for advanced coatings of vascular stents. Gallic acid (GA), a chemically unique phenolic acid with important biological functions, presents benefits to the cardiovascular disease therapy because of its superior antioxidant effect and a selectivity to support the growth of ECs more than SMCs. In this study, GA was explored to tailor such a multifunctional stent surface combined with plasma polymerization technique. On the basis of the chemical coupling reaction, GA was bound to an amine-group-rich plasma-polymerized allylamine (PPAam) coating. The GA-functionalized PPAam (GA-PPAam) surface created a favorable microenvironment to obtain high ECs and SMCs selectivity. The GA-PPAam coating showed remarkable enhancement in the adhesion, viability, proliferation, migration, and release of nitric oxide (NO) of human umbilical vein endothelial cells (HUVECs). The GA-PPAam coating also resulted in remarkable inhibition effect on human umbilical artery smooth muscle cell (HUASMC) adhesion and proliferation. These striking findings may provide a guide for designing the new generation of multifunctional vascular devices.

Bioactive Plasma-Polymerized Bipolar Films for Enhanced Endothelial Cell Mobility

A facile approach to a highly bio-active interface material is reported. XPS reveals that polar entities exist at the interface between PPAam and PPAac nanolayers. They induce strong dipolar orientation polarizability and cause the redistribution of charges, which results in a remarkable increase of polar surface energy and hydrophilicity of the multistack bipolar films. In particular bipolar films with amine groups on their outermost surface show strongly enhanced cellular mobility. The attachment, adhesion, proliferation, migration, and coverage of ECs are significantly enhanced on such films. They are therefore promising as vascular implant materials, and could have applications as coating materials for tissue engineering.