Title : Multifunctional titanium surface engineering via sodium silicate-activated TiO2/HAp/Ag nanocomposites for enhanced bioactivity and antibacterial efficacy

Background: The lack of intrinsic bioactivity and antibacterial functionality in titanium implant surfaces remains a major limitation in modern orthopedic and dental applications, often leading to poor osseointegration or postoperative infections. To address these challenges, this study aims to engineer a novel, multifunctional bio-ceramic nanocomposite surface (TiO2/HAp/Ag) that enhances apatite mineralization while simultaneously inhibiting bacterial growth.

Methods: Hydroxyapatite (HAp) nanoparticles (average crystal size of 49.7 nm; Ca/P ratio of ~1.67) were green-synthesized from natural bovine bones through controlled washing, drying, calcination at 700 °C, and mechanical milling. The ceramic nanocomposites were prepared by incorporating 3 wt.% and 6 wt.% HAp with commercial titanium dioxide (TiO2, ~25 nm) and polyethylene glycol as a binder, followed by ultrasonic dispersion and axial pressing to form porous pellets sintered at 750 °C. To boost surface reactivity, the samples underwent alkaline surface activation by immersion in a 0.002 M sodium silicate (Na2SiO3) solution for 7 days at 36 °C. In vitro bioactivity was evaluated using Simulated Body Fluid (SBF) for 14 days according to the Kokubo protocol. Biological safety was assessed via hemolysis assay, and antibacterial activity against Staphylococcus aureus and Enterococcus faecalis was investigated using the zone of inhibition method.

Results: Infrared spectroscopy (FTIR) and Energy-Dispersive X-ray Spectroscopy (EDS) confirmed the formation of functional groups characteristic of calcium phosphate phases and demonstrated a significant increase in apatite layer deposition post-SBF immersion, accelerated by Na2SiO3-activated Ti-OH and silicate nucleation sites. SEM morphology confirmed dense, bio-interactive surface structures. Furthermore, the TiO2/HAp/Ag composites exhibited superior antibacterial efficacy, displaying inhibition zones ranging from 25 mm to 33 mm. Hemolysis testing proved the material's biocompatibility and safety.

Dr. Noor Sabeeh Jouda is a lecturer and biomaterials physics researcher affiliated with the General Directorate of Education in Wasit, Ministry of Education, Iraq. She holds a PhD in Materials Physics from the College of Science, Wasit University. Dr. Jouda has participated in international conferences (AIP, Materials Today) and published in peer-reviewed journals including BioNanoScience (Springer Nature) and RCMA (IIETA). Her current and recent research focuses on advanced ceramic nanocomposites, green synthesis of nanoparticles, alkaline surface modification of titanium implants, and drug delivery systems.