Tea polyphenol-mediated catalytic coating applied in cardiovascular materials

摘要

Introduction: Epigallocatechingallate (EGCG), the major tea polyphenol, is good for cardiovascular system. EGCG has potential to form thin coating on different material substrate as multifunctional platform, because its structure resembles dopamine. NO has many functions including preventing formation of thrombosis and inhibiting vascular smooth muscle cell (VSMC) proliferation. The disulfide and diselenide materials could catalyze endogenous NO donors to decompose and release NO. Our investigation explored EGCG/cystamine and EGCG/selenocystamine crosslinking coating and their NO catalytic effects. Materials and Methods: Cystamine or selenocystamine were dissolved in EGCG-Tris solution at the concentrations of EGCG 0.2mg/L and cystamine 0.2,0.5mg/L or selenocystamine 0.1,0.2 mg/L. Stainless steel disks were immersed into solutions for 24 h at 25°C, and then vacuum-dried. The EGCG/cystamine or EGCG/selenocystamine coated samples were labeled as E_xS_y or E_xSe_y. The material characteristic of coatings were measured by XPS, ellipsometry and AFM. The NO release catalyzed by coatings was tested by a Griess method. In vitro platelet adhesion, VSMC and cyclic guanylate monophosphate (cGMP) analysis were adopted to evaluate biological behavior of coatings. Results and Discussion: It was speculated that the E_xS_y or E_xSe_y coatings were polydopamine-like coating. For certain EGCG concentration, the thickness and surface roughness of coatings increased with concentrations of cystamine or selenocystamine rising. S-S and Se-Se bonds were detected in XPS spectra for E_xS_y or E_xSe_y samples. Fig. 1 (A) XPS survey spectra, (B) the densities of -OH and -NH2, (C) AFM morphology and thickness of coatings Two typical NO generation patterns occurred for catalytic RSNO decomposition by disulfur and diselenide bond in E_xS_y or E_xSe_y. At initial catalytic reaction stage, the fast release mode of NO could observed with release rate 4.1×10~(-10) mol×cm~(-2) ×min~(-1)which was then followed by a slow release mode of NO with a release rate around 1.4×10~(-10) mol×cm~(-2) ×min~(-1). It is demonstrated that the NO release rates of E_xS_y or E_xSe_y were close to the release rates of NO produced by the healthy endothelium. Fig. 2 (A) Nitrite accumulation amount in solutions, (B) Average release rates of NO In the group without donor supplementation, most of the platelets adhered on all specimens were fully spread indicating a high degree of activation and aggregation. In contrast, the adhesion and activation of platelets were substantially reduced on the E_(0.2)S_(0.5) or E_(0.2)Se_(0.2). which expressed the resting spherical state. The E_(0.2)S_(0.5) or E_(0.2)Se_(0.2) significantly inhibited proliferation of VSMCs, when the medium was supplemented with donor. The release of NO produced by E_(0.2)S_(0.5) or E_(0.2)Se_(0.2) (in the presence of donor supplementation) resulted in a significant increase in the synthesis of cGMP of both platelets and VSMCs. The increases in the synthesis of cGMP of platelets and VSMCs, and the above results of platelet adhesion and VSMC growth confirmed the biological availability and activity of NO produced by E_(0.2)S_(0.5) or E_(0.2)Se_(0.2) coatings. Fig.3 The concentration of cGMP synthesized by (C) platelets and (D) VSMCs incubated with samples Conclusion: EGCG-mediated coatings with NO-catalytic bioactivity were developed. These coatings had a remarkable suppression of collagen-induced platelet activation and proliferation of VSMCs.