Biotransformation of Silver Released from Nanoparticle Coated Titanium Implants Revealed in Regenerating Bone

Antimicrobial silver nanoparticle coatings have attracted interest for reducing prosthetic joint infection. However, few studies report in vivo investigations of the biotransformation of silver nanoparticles within the regenerating tissue and its impact on bone formation. We present a longitudinal investigation of the osseointegration of silver nanoparticle-coated additive manufactured titanium implants in rat tibial defects. Correlative imaging at different time points, using nanoscale secondary ion mass spectrometry, transmission electron microscopy (TEM), histomorphometry and 3D X-ray micro-computed tomography, provided quantitative insight from the nano to macro scales. The quality and quantity of newly formed bone is comparable between the uncoated and silver coated implants. The newly formed bone demonstrates a trabecula morphology with bone being located at the implant surface as well as at a distance at 2 weeks. Nanoscale elemental mapping of the bone-implant interface showed that silver was present primarily in the osseous tissue and was co-localized with sulfur. TEM revealed silver sulfide nano-particles in the newly regenerated bone, presenting strong evidence that the previously in vitro observed biotransformation of silver to silver sulfide occurs in vivo.