A non-antibiotic organic coating on ZA6-1 surface releasing different concentrations of sodium dodecyl sulphate/levulinic acid for orthopaedic application

Bone implantation surgery is often accompanied by bacterial infection,resulting in infectious bone non-union,pathological fracture and other serious consequences,which will aggravate the pain of patients.A non-antibiotic coating consisting of sodium dodecyl sulphate(SDS)and levulinic acid(LA)with different concentrations was prepared by the authors on the zinc–aluminium alloy(ZA6-1)using a wet chemistry treatment for orthopaedic application.The influence of SDS/LA concentrations on the surface morphology,composition and performance of the developed coating was investigated.The results showed that as-prepared coating on a zinc alloy surface could improve the substrate's corrosion resistance and increase the degradation rate from 0.82 to 19.70μm/year upon raising the SDS/LA concentration.Furthermore,higher hydrophilicity(<14°),better cell proliferation(>100%)and morphology,as well as good cell adhesion and differentiation(ALP>95%for 7 days)were observed on coated zinc alloys.The increased SDS/LA concentration slightly weakens the biocompatibility and enhances the antibacterial performance of coated zinc alloys due to the synergistic effect of SDS/LA.Overall,the coating comprising 6 wt.%SDS and 9 wt.%LA showed excellent antibacterial action with a high level of biocompatibility,confirming its potential application for orthopaedic implants.

Tuning C-C sp2/sp3 ratio of DLC films in FCVA system for biomedical application

Diamond like carbon(DLC)films with different C-C sp2/sp3 ratios were prepared by tuning the N2 flow rate in a filtered cathodic vacuum arc(FCVA)system.The increase of N2 flow rate facilitated the increase of C-C sp2/sp3 ratio(1.09-2.66),the growth of particle size(0.78-1.58 nm)and the improvement of surface roughness.The SBF immersion results,as well as WCAs(77.57°~71.71°),hemolysis rate(0.14-1.00%)and cytotoxicity level(0)demonstrated that the as-fabricated DLC film was promising for biomedical application.As a result of surface charge effect,the apatite layers formed in the SBF increased with the increase of C-C sp2/sp3 ratio until 1.74 and then showed a tiny decrease during 1.74-2.66.A raise of hemolysis and cytotoxicity was observed when sp2/sp3 ratio was increased.Moreover,a decrease of friction coefficient of Si surface induced by increasing sp2/sp3 ratio was respectively evidenced in ambient air and SBF lubrication environments.

Improving anti-Gram-positive-bacterial performance and osteogenesis for zinc alloy via mussel mimetic polydopamine with non-antibiotic lysozyme and parathyroid hormone

In this work,a novel coating with a non-antibiotic agent for inhibiting Gram-positive bacteria and promoting osteogenesis was prepared on zinc-aluminium alloy(ZA6-1)via mussel mimetic polydopamine(PDA)containing lysozyme(LYS)and parathyroid hormone(PTH).The results indicate that as-deposited coatings can efficiently decrease the degradation rate of ZA6-1 from 0.52 to 0.16 mm/year,and the addition of LYS weakens the coating resistance,while the addition of PTH enhances the coating resis-tance.In spite that no obvious inhibition of Escherichia coli is observed,the coated zinc alloys show good in vitro antibacterial performance against Staphylococcus aureus.Compared with ZA6-1 zinc alloys,the increase of antibacterial efficacy reaches 86.9%-90.1%.Furthermore,the lower hydrophilicity(26.4°),higher osteoblast cell viability(>100%),good osteoblast cell morphology and better osteoblast cell differentiation(ALP=107.7%)for PDA-LYS/PTH coated samples support that as-prepared coating is promising for modifying biodegradable zinc implants.