Reimagining Hydroxyapatite: Silver Doping for Antibacterial Precision

Abstract

Silver-doped hydroxyapatite (Ag-HA) has emerged as a promising biomaterial for antibacterial applications and bone regeneration. The incorporation of silver ions (Ag⁺) into the hydroxyapatite (HA) lattice enhances its antimicrobial properties while maintaining biocompatibility. This study aims to synthesize and characterize Ag-HA composites using the ion exchange method and evaluate their structural, morphological, and antibacterial properties. Ag-HA was synthesized by replacing calcium ions in HA with silver ions through an ion exchange process. A reaction mixture of 0.5 M calcium nitrate and 0.3 M diammonium phosphate was maintained at pH 10 with ammonia, followed by the addition of silver nitrate. The mixture was stirred at room temperature for 24 hours. Characterization was conducted using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) to determine the chemical structure, crystallinity, and morphology. Antibacterial activity was assessed using inhibition zone assays against Escherichia coli and Staphylococcus aureus, while hemolysis studies evaluated biocompatibility. XRD analysis confirmed the hexagonal crystalline structure of HA, with characteristic peaks at 2θ = 25.9°, 31.8°, 32.9°, and 34.1°. SEM images revealed a highly porous, clustered morphology at a 1 µm scale, characteristic of nanoparticle-based materials. Ag-HA demonstrated enhanced antibacterial activity, with inhibition zone diameters of 2.9 cm for E. coli and 1.2 cm for S. aureus, surpassing pure HA. Hemolysis tests showed 2.25% hemolysis, indicating good biocompatibility below the 5% threshold. The synthesized Ag-HA composite exhibited enhanced antibacterial activity and a porous morphology suitable for bone regeneration. With its low hemolysis rate, Ag-HA holds great potential as a biocompatible and antimicrobial biomaterial for biomedical applications.