Green Synthesis of Multi-Walled Carbon Nanotube-Reinforced Hydroxyapatite Doped with Silver and Silver-Core Selenium-Shell Nanoparticles: Synthesis, Characterization, and Biological Activity

Hydroxyapatite (HAp) is widely used in biomedical applications due to its biocompatibility, osteoconductivity, and bioactivity. However, its low mechanical strength, tendency toward rapid corrosion, and lack of bactericidal properties present significant limitations in applications. This study aimed to improve the properties of HAp by reinforcing it with multi-walled carbon nanotubes (MWCNTs) and doping it with silver nanoparticles (AgNPs) and silver-core selenium-shell nanoparticles (Ag@SeNPs). Ocimum basilicum extract was used as both a reducing and stabilizing agent in the synthesis of nanoparticles using an environmentally friendly and non-toxic method as an alternative to traditional methods. The synthesized HAp, HAp/MWCNT, Ag-HAp/MWCNT, and Ag@Se-HAp/MWCNT nanocomposites were characterized by TEM, SEM, XRD, Raman spectroscopy, and BET analysis. BET analysis showed a reduction in surface area from 109.4 m2/g for pure HAp to 71.4 m2/g, 47.5 m2/g, and 35.3 m2/g for HAp/MWCNTs, Ag- HAp/MWCNTs, and Ag@Se-HAp/MWCNTs, respectively. Antimicrobial activities against P. aeruginosa, E. coli, S. aureus, E. faecalis, and C. albicans were evaluated. HAp and HAp/MWCNT did not show any antimicrobial activity, while Ag-HAp/MWCNTs showed inhibition zones of 14 mm for Escherichia coli and 18 mm for Pseudomonas aeruginosa at 5 mg/mL. Ag@Se-MWCNTs/HAp exhibited superior efficacy with inhibition zones of 18 mm, 12 mm, and 20 mm for S. aureus, E. faecalis, and Candida albicans, respectively. The incorporation of Ag@SeNPs enhanced HAp’s antibacterial and antifungal properties through a synergistic mechanism.