Synthesis of antibacterial silver and zinc doped nano-hydroxyapatite with potential in bone tissue engineering applications

Nano-hydroxyapatite doped with either Ag+ or Zn2+ has been synthesized using the sol-gel precipitation method at conditions of low dopant content (dopant/Ca2+ molar ratio of 0.006 and 0.012) and low temperature (around 200 degrees C). The synthesized materials show length dimensions of 10-40 nm, low crystallinity, and rod-shaped particles for the Zn2+ doped samples. Through the simulated body fluid assay, the ability of the materials to nucleate the formation of apatite on their surface was examined. The viability of human dental pulp stem cells cultured with the materials was evaluated after 3 and 7 days, and the osteogenic differentiation of cells cultured with the materials was assessed through the activity of the alkaline phosphatase. In addition, the antibacterial activity against Aggregatibacter actinomycetemcomitans, an important microorganism related to oral infections, was studied by counting bacterial colony-forming units cultured in the presence of the materials. All the ma-terials showed biocompatibility with human dental pulp stem cells, osteoinductive potential, and antibacterial activity against Aggregatibacter actinomycetemcomitans, highlighting among them the Zn2+ doped nano-hydroxyapatite samples. Considering the importance of hydroxyapatite in the field of medical and dental ap-plications of ceramic materials, and the pathologies induced by Aggregatibacter actinomycetemcomitans in oral tissues, the adequate balance between the biocidal activity and biocompatibility of these synthetic nano-hydroxyapatite materials highlights their potential for biomedical and dental applications.