ICMCTF2019 Session D1-1-MoM: Surface Coating and Modification for Use in Biological Environments I

The goal of this study is to develop a novel biomedical material, where gold thin film is deposited on collagen fabrics for skin tissue engineering. Type I Collagen had been used in many products for its biocompatibility and critical role in skin recovery. Gold, in the form of nanoparticles (AuNPs), had been proven to improve biomaterial properties, such as mechanical strength, elasticity, degradation resistance, cell attachment, cell proliferation and wound healing. Unlike chemically prepared AuNPs in most of present literature, very thin gold films deposited by high-power impulse magnetron sputtering (HIPIMS) on collagen fibers reveal the advantage of green synthesis process and free from chemical ligand of gold particles.

Scanning electron microscopy (SEM) and X-ray diffraction (XRD) are used to observe the surface morphology and microscopic characteristics of the composites. Fourier transform infrared spectroscopy (FTIR) and circular dichroism spectroscopy (CD) are used to evaluate functional groups and secondary structure of collagen, respectively. Process of biomedical fabrics with collagen and gold thin film in different thickness is established.

Keywords: gold thin films, HIPIMS, collagen fabric, skin cell recovery

Hard coatings such as diamond like carbon (DLC) on articulating joints can result in desired surface properties showing extremely low wear. However, an interlayer material or a single row of contamination atoms at the coating/substrate interface can result in altered corrosion behavior and possible adhesion instability. A method to determine the chemical composition of the few atomic rows of altered material at an interface, buried under several microns of coatings, will be shown by low angle polishing down to less than 0.06 degrees (less than 1/1000 steepness). Corrosion effects such as crevice corrosion, which can cause coating delamination after some years in vivo, cannot be accelerated in simulator testing since it evolves only as a function of time in media. A new setup for accelerated crevice corrosion testing in body fluid, as well as preliminary results, will be presented. Furthermore, stress corrosion cracking and corrosion-fatigue can damage the few rows of reacted atoms present at an interface. By simulating in vivo conditions, we are developing an accelerated test to asses these deteriorating effects at the interface. First results of coating adhesion lifetime expectations, including the influence of small detrimental contaminations, will be shown.

The adhesion of platelet cells is viewed as a first step in thrombus formation, and cancer cell attachment can lead to cancer seeding. The amorphous structure of metallic glasses (MGs) is a new group of coating materials exhibiting excellent hydrophobicity and resistance to bacterial colonization, as well as relatively low coefficient of friction. In this presentation, we will report a study which has been published in Surface and Coatings Technology, Vol. 344, p. 312-321 (2018), describing the feasibility of utilizing Zr₅₃Cu₃₃Al₉Ta₅ thin film metallic glass (TFMG) to minimize the adhesion of various human cancer cells (breast cancer cell, colon cancer cell, and esophageal cancer cell), human and animal platelets. TFMG was respectively grown on glass substrates to a thickness of 200 nm using magnetron sputtering. TFMG was shown to reduce surface roughness of glass. The concentrations of all major ions released from the TFMG were well below toxic levels. TFMG surfaces were effective in increasing the contact angle of water, phosphate buffer saline and blood from different animal species. The application of TFMG to bare surfaces was shown to reduce the attachment area of human platelets by 77 % and that of pig platelets by 63%. TFMG also reduced the attachment of cancer cells by up to ~87%. These characteristics can be attributed to a low surface free energy of TFMG-coated surfaces (31.89 mN/m), which is far below that of bare glass (47.80 mN/m). These findings demonstrate the considerable potential of TFMG coatings in the fabrication of medical instruments aimed at preventing the adhesion of platelet and cancer cells.

The electrodeposited coatings were characterized by Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), X-Ray diffraction, Raman spectroscopy and Potentiodynamic polarization technique. Raman spectroscopy showed the presence of graphene & 2-D graphitic phase. Finally, a post deposition treatment was done to evaluate in-vitro bioactivity by Simulated Body Fluid (SBF) immersion test. The results showed that graphene coating onto Nitinol substrate improved anti-corrosion rate and anti-bacterial properties while reducing friction as compared to bare Nitinol wires.

Hence, this bioactive coating exhibited better mechanical strength, enhanced wear and corrosion resistance indicating high potential for biomedical applications.