Interstitial doping with nitrogen and oxygen turns ordinary titanium-gold into a super-hard, bacteria-resistant implant material.
Study: Transformative Bioactive Wear Resistant Ti 3 Au:N andTi 3 Au:O Coatings for Medical Implants and Devices. Image Credit: Krezodent/Shutterstock.com
A new study in Advanced Healthcare Materials reports the creation of nitrogen- and oxygen-doped Ti3Au coatings that significantly enhance wear resistance and antibacterial activity.
Traditional Ti-6Al-4V alloys offer strength and biocompatibility but suffer from wear and metal-ion release over time. The new Ti3Au:N and Ti3Au:O films address these challenges by combining mechanical durability with bioactive function.
Titanium implants are widely used for their strength and corrosion resistance, yet surface degradation and ion leaching limit their reliability.
Ceramic coatings such as Ti-N and Ti-O have improved hardness but often struggle with adhesion and debris formation. Intermetallic Ti3Au has recently drawn attention for its high hardness and cytocompatibility.
Building on this, the researchers introduced interstitial nitrogen and oxygen to stabilize the α-Ti3Au phase and further boost performance.
Study Design
The team fabricated Ti3Au, Ti3Au:N, and Ti3Au:O coatings on Ti-6Al-4V substrates via magnetron co-sputtering of Ti and Au targets in Ar with controlled N2 or O2.
Films were deposited at 450 °C to a thickness of about 1 µm, containing roughly 14.7 at.% nitrogen, 13.3 at.% oxygen, and 21-22 at.% gold.
Characterization using XRD, HR-SEM, TEM, EDS, and AFM revealed β→α phase conversion, smaller crystallites (~27–31 nm), and fine, tapered grains.
Elemental mapping showed uniform Ti and Au distribution with limited N/O detectability and slight oxygen enrichment at the interface.
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Performance
Doped coatings achieved a hardness of ~14.7 GPa, about 2.4 times that of Ti-6Al-4V (approximately 140 % higher), without a modulus penalty. Scratch tests showed 3.5-4.5× higher critical loads and minimal spallation, indicating strong adhesion.
During wear tests in simulated body fluid, uncoated Ti-6Al-4V exhibited a friction coefficient of ~0.5, while undoped Ti3Au initially showed a value near 0.1 and subsequently increased to 0.2.
Both doped films remained stable at ~0.09-0.10 with wear rates over 20 times lower than the substrate.
Wear track widths dropped from ~300 µm on Ti-6Al-4V to nearly invisible on doped coatings, confirming superior surface integrity.
Cytocompatibility assays with L929 fibroblasts showed ≥90 % cell viability for all coatings, with doped films maintaining or exceeding baseline levels. Metal-ion leaching stayed below 0.2 ppm after 168 hours in solution, indicating strong chemical stability.
Using bioluminescent E. coli pQE-ilux, Ti3Au:N and Ti3Au:O achieved ~1-log bacterial reduction within 19-20 minutes, comparable to copper and silver controls.
The authors attribute this behavior to gold-assisted antibacterial action, which is likely to involve reactive oxygen species and surface-mediated effects.
Outlook and Future Use
The findings show that interstitial N and O incorporation stabilizes the α-Ti3Au phase, enhances hardness, and preserves flexibility while adding rapid antibacterial performance. Future work will refine dopant control and explore the mechanisms underlying Au-mediated bacterial suppression.
These doped Ti3Au coatings represent a practical step toward next-generation implant surfaces that may provide long-term wear protection and infection resistance.
Journal Reference
Lukose, C. C., et al. (2025). Transformative Bioactive Wear-Resistant Ti3Au: N and Ti3Au:O Coatings for Medical Implants and Devices. Advanced Healthcare Materials, e03441. DOI :10.1002/ADHM.202503441
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