Corrosion Behavior and Biocompatibility of Diamond-like Carbon-Coated Zinc: An In Vitro Study

Abstract

Owing to the desirable degradation rate and good biocompatibility, zinc (Zn) and Zn alloys are promising biodegradable implant metals in orthopedic and cardiovascular applications. Surface modification, such as deposition of coatings, is frequently implemented to further enhance their biological properties. In this study, diamond-like carbon (DLC) films are deposited on Zn by magnetron sputtering. The DLC films do not change the surface morphology of Zn but alter the hydrophobic properties with a contact angle of approximately 90°. Electrochemical and in vitro immersion tests reveal that the corrosion resistances of the DLC-coated Zn decrease unexpectedly, which is possibly due to galvanic corrosion between the DLC film and Zn substrate. Furthermore, the uncoated and coated Zn samples show hemolysis ratios less than 1%. The cells cultured in the Zn extract exhibit higher viability than those cultured in the extract of the DLC-coated Zn, suggesting that the DLC films decrease the cytocompatibility of Zn. The lower corrosion resistance has little influence on the hemolysis ratio, suggesting that hemolysis is not an obstacle for the design of Zn-based biomaterials. Our results show that the traditional concept of protection with DLC films may not be applicable universally and decreased corrosion resistance and cytocompatibility are actually observed in DLC-coated Zn.

Overview on the Antimicrobial Activity and Biocompatibility of Sputtered Carbon-Based Coatings

“…Most of the researchers in the biology field are focused on the antimicrobial characteristics of DLC films regarding their mechanical, chemical, and tribological properties. To add an antimicrobial effect to DLC materials, different elements can be added (such as Ag, Zn, and Cu) [49,59,83,103,104,[141][142][143].…”

“…Peng et al [142] deposited a DLC coating on zinc substrates by magnetron sputtering using a high-purity C target. They studied the electrochemical properties after immersion in phosphate-buffered saline (PBS) for seven days and found that the corrosion resistance probably decreases due to galvanic oxidation between the DLC film and Zn substrate.…”

A review on current research status of the surface modification of Zn-based biodegradable metals

“…Magnetron sputtering has been widely applied to deposit high-quality functional coatings on the surface of diverse materials [ 217 , 218 ]. Peng et al [ 193 ] produced diamond-like carbon (DLC) film on the surface of pure Zn. They found that the DLC film accelerated the corrosion of substrate, which is possibly attributed to the galvanic corrosion between the film and Zn substrate.…”

Preliminary Investigation on Degradation Behavior and Cytocompatibility of Ca-P-Sr Coated Pure Zinc

“…The lack of zinc in the human body will cause physical dysplasia, decreased appetite, decreased immune function, and hinder the human body's absorption of vitamins [7]. More importantly, the corrosion potential of zinc (−0.763 V) is intermediate between magnesium "(−2.37 V) and iron (−0.440 V)" [8]. Bowen et al [9].…”

“…More and more researchers began to pay attention to the surface modification of zinc and its alloys. In recent years, the chemical deposition method, electrochemical method, micro-arc oxidation or anodic oxidation method, gel method, and atomic layer deposition polymer have been developed to improve the biocompatibility of zinc and its alloys [8,[15][16][17][18][19][20]. Yuan [15] used atomic layer deposition to develop a ZrO 2 nanofilm on the Zn-0.1Li alloy.…”