Surface engineering of artificial heart valve disks using nanostructured thin films deposited by chemical vapour deposition and sol-gel methods

Pyrolytic carbon (PyC) is widely used in manufacturing commercial artificial heart valve disks (HVD). Although PyC is commonly used in HVD, it is not the best material for this application since its blood compatibility is not ideal for prolonged clinical use. As a result thrombosis often occurs and the patients are required to take anti-coagulation drugs on a regular basis in order to minimize the formation of thrombosis. However, anti-coagulation therapy gives rise to some detrimental side effects in patients. Therefore, it is extremely urgent that newer and more technically advanced materials with better surface and bulk properties are developed. In this paper, we report the mechanical properties of PyC-HVD, i.e. strength, wear resistance and coefficient of friction. The strength of the material was assessed using Brinell indentation tests. Furthermore, wear resistance and coefficient of friction values were obtained from pin-on-disk testing. The micro-structural properties of PyC were characterized using XRD, Raman spectroscopy and SEM analysis. Also in this paper we report the preparation of freestanding nanocrystalline diamond films (FSND) using the time-modulated chemical vapour deposition (TMCVD) process. Furthermore, the sol-gel technique was used to uniformly coat PyC-HVD with dense, nanocrystalline-titanium oxide (nc-TiO2) coatings. The as-grown nc-TiO2 coatings were characterized for microstructure using SEM and XRD analysis.     

Surface characterization of biomaterials by electron spectroscopy for chemical analysis

Electron spectroscopy for chemical analysis (ESCA) is perhaps the most valuable single method available for characterizing the surfaces of biomaterials. The ESCA analytical method is rich in information, observes a relevant surface region, and has been shown to generate results that correlate with biological response. In this article, the analysis of actual ESCA data is illustrated by reviewing a study in which polymer-coated glass surfaces, prepared for use as tissue culture substrates, are examined by ESCA. The application of more advanced ESCA techniques such as angular-dependent analysis to this situation is also considered. Finally, published applications of ESCA to the study of polyurethanes, hydrogels, protein films, cell culture substrates, and dental materials are briefly reviewed.     

Initiated chemical vapor deposition of thermoresponsive poly(N-vinylcaprolactam) thin films for cell sheet engineering

Poly(N-vinylcaprolactam) (PNVCL) is a thermoresponsive polymer known to be nontoxic, water soluble and biocompatible. Here, PNVCL homopolymer was successfully synthesized for the first time by use of a one-step vapor-phase process, termed initiated chemical vapor deposition (iCVD). Fourier transform infrared spectroscopy results showed that radical polymerization took place from N-vinylcaprolactam monomers without damaging the functional caprolactam ring. A sharp lower critical solution temperature transition was observed at 31 °C from the iCVD poly(N-vinylcaprolactam) (PNVCL) film. The thermoresponsive PNVCL surface exhibited a hydrophilic/hydrophobic alteration with external temperature change, which enabled the thermally modulated attachment and detachment of cells. The conformal coverage of PNVCL film on various substrates with complex topography, including fabrics and nanopatterns, was successfully demonstrated, which can further be utilized to fabricate cell sheets with aligned cell morphology. The advantage of this system is that cells cultured on such thermoresponsive surfaces could be recovered as an intact cell sheet by simply lowering the temperature, eliminating the need for conventional enzymatic treatments.     

碱性成纤维细胞生长因子和骨髓间充质干细胞构建的组织工程心脏瓣膜赖氨酰氧化酶的表达

目的 探讨碱性成纤维细胞生长因子(bFGF)和骨髓间充质干细胞(MSC)构建组织工程心脏瓣膜(TEHV)及其赖氨酰氧化酶(LOX)的表达.方法 贴壁培养法分离、培养和纯化大鼠MSC,取第3代种植于去细胞瓣叶支架上.分别将瓣叶置于含10 μg/L bFGF的培养液(A组)、普通培养液(B组)中构建TEHV,大鼠肌成纤维细胞构建的TEHV为C组,培养14 d后,采用Amplex red荧光法检测各组中的LOX蛋白含量,RT-PCR检测LOX mRNA表达.结果 B组的LOX蛋白含量和mRNA表达[(0.137±0.003)mg/L,2.08±0.03]高于A组[(0.124±0.002)mg/L,0.87±0.01]和C组[(0.127±0.002)mg/L,0.90±0.01](P<0.05),A、C两组差异无统计学意义(P>0.05).结论 bFGF可能通过降低MSC的LOX表达,使MSC构建的TEHV达到与肌成纤维细胞构建的类似.