Non-cytotoxic zinc/f-graphene nanocomposite for tunable degradation and superior tribo-mechanical properties: Synthesized via modified electro co-deposition route

Zinc (Zn) alloys and composites have recently been recognized as potential biodegradable materials for bone implants and vascular stents. Although new class of Zn-based materials have superior mechanical integrity than polymeric materials during biodegradation, the reinforcement of biocompatible form of graphene nanoplatelets (GNPs) in Zn matrix can be utilized to further enhance their effectiveness for loadbearing implants. In this work, pristine GNPs were functionalized with polyethelene glycol to reduce their toxicity and reinforced in Zn matrix using modified electro co-deposition (M-ECD) method. The influence of various concentrations of functionalized GNPs (f-GNPs) in ECD bath on microstructure, interface bonding of functional groups, morphology, and elemental composition, corrosion resistance, and tribo-mechanical behavior of Zn/f-GNP nanocomposite have been studied. The Zn/f-GNP nanocomposites were also screened systemically for biological responses by in-vitro cytotoxicity and antibacterial studies. The nanocomposite sample of 100 mg/L of f-GNPs concentration in ECD bath has demonstrated a uniform slow in-vitro degradation rate of 26 +/- 0.8 x 10-3 mm/year. The primary degradation products included zinc oxide [ZnO], zinc hydroxide [Zn(OH)2], and simonkolleite [Zn5(OH)8Cl2H2O] observed from x-ray diffraction of corroded nanocomposites. The microhardness, compressive yield strength and ultimate compressive strength of Zn/f-GNP (100 mg/L) nanocomposite were 108.5 HV, 284.9 MPa, and 292.6 MPa, respectively, which were significantly higher than pure Zn. In addition, the good invitro human keratinocyte cell viability and effective antibacterial activity of Zn/f-GNP nanocomposite render it a very attractive biodegradable implant material for future implication in orthopedic fixation (screw, pins, sutures, and plates) and stents (coronary and cardiovascular stents) applications.

Automated summary

Zinc alloys and composites with graphene nanoplatelets (GNPs) have potential as biodegradable materials for bone implants and vascular stents. The addition of functionalized GNPs in the zinc matrix enhances the loadbearing properties of the material. This study investigated the effects of different concentrations of functionalized GNPs on the microstructure, corrosion resistance, mechanical behavior, and biological responses of the zinc/GNP nanocomposite. The nanocomposite with a concentration of 100 mg/L of GNPs demonstrated a slow in-vitro degradation rate, high mechanical strength, good cell viability, and effective antibacterial activity.