Antibacterial activity and surface fractal properties of Ag/CuO-doped hardystonite nanocomposites against bacteria

The emergence of antibiotic-resistant bacteria requires the design of novel antimicrobial materials with proven efficacy and biocompatibility. However, the contribution of surface fractal characteristics to the antibacterial performance of hardystonite (Ca₂ZnSi₂O₇)-based nanocomposites remains unclear. Therefore, this work synthesizes hardystonite (Ca₂ZnSi₂O₇)-based nanocomposites doped with silver (HT/Ag; 1, 2, and 5 wt%) and copper oxide (HT/CuO). HT/Ag nanocomposites were prepared by arc discharge and HT/CuO was synthesized via an in-situ route. Materials were characterized by XRD, FTIR, TEM, and FESEM/EDX. Surface texture was quantified, and the fractal dimension of intensity line profiles was determined using power spectrum analysis. Antibacterial properties against Escherichia coli , Pseudomonas aeruginosa , and Staphylococcus aureus were determined by broth microdilution, whereas antibiofilm properties were determined by crystal violet assay (OD570). Among the formulations, HT/Ag5 demonstrated the highest antibacterial properties with MIC/MBC of 4/8 mg/mL against E. coli , 2/4 mg/mL against P. aeruginosa , and \(8/16\) mg/mL against S. aureus , while HT/CuO demonstrated moderate activity against Gram-negative bacteria and no detectable activity against S. aureus at tested concentrations. In the biofilm assay, there was a significant reduction in biofilm formation by S. aureus and P. aeruginosa (≈ 79–81% inhibition; 4 × MIC shifted S. aureus into non-biofilm form) and disruption of pre-formed biofilms by up to 56.76% ( S. aureus ) and 62.23% ( P. aeruginosa ), respectively, while the effect was minimal (≤ 8.23% disruption) against E. coli biofilms. HT/Ag5 demonstrated HFF cell viability above the ISO 10993-5 limit within 15.625–500 μg/mL. Fractal dimensions of HT/Ag surfaces were between 1.52 and 1.57, with HT/Ag5 having the highest value.