Microwave-assisted synthesis of lithium-bismuth co-doped hydroxyapatite with enhanced antimicrobial and biological performance

Hydroxyapatites (HA) co-doped with Li⁺ and Bi³⁺ ions were synthesized by a microwave-assisted wet precipitation method to improve their structural, biological, and antibacterial performances. Dual doping of Li⁺ and Bi³⁺ ions led to an increase in crystallinity and crystallite size compared to single doping, indicating successful incorporation of dopants into the HA lattice. Co-doping also resulted in minor lattice distortions without altering the phase purity of HA. Biological characterization using adipose-derived mesenchymal stromal cells revealed that Bi incorporation enhanced cell proliferation and osteogenic activity, whereas excessive Li addition caused partial cytotoxicity. Interestingly, Li/Bi co-doping balanced this effect, leading to improved cell viability and differentiation compared to single-doped samples. Moreover, Li and Bi substitutions imparted significant antimicrobial activity against E. coli, S. aureus, P. aeruginosa, E. faecalis, and C. albicans, demonstrating the dual bioactive and antimicrobial nature of the material. The combined influence of Li⁺ and Bi³⁺ ions effectively modified the crystallinity and biological response of HA, suggesting that Li-Bi co-doped HA is a promising candidate for multifunctional coatings and bone tissue engineering applications.