Evaluation of the biological activities of Bacillus cereus-synthesized titanium dioxide nanoparticles

TL;DR

This study shows that titanium dioxide nanoparticles made using Bacillus cereus have strong antimicrobial, antibiofilm, anticancer, and antiviral properties.

Contribution

The novel contribution is the green synthesis of highly crystalline anatase TiO₂ NPs using B. cereus with multifunctional biological activities.

Findings

TiO₂ NPs showed broad-spectrum antimicrobial activity with MICs ranging from 78 to 2500 μg/mL.

The nanoparticles exhibited strong antiviral activity against HSV-1 with 74.74% inhibition at 60 µg/mL.

Cytotoxicity tests revealed selective anticancer activity with IC₅₀ values of 212.15 μg/mL (Caco-2) and 342.96 μg/mL (Vero cells).

Abstract

The emergence of multidrug-resistant pathogens and the growing burden of cancer worldwide demand novel therapeutic approaches. This study evaluated the biological activities of green-synthesized titanium dioxide nanoparticles (TiO₂ NPs) using Bacillus cereus cell-free supernatant and titanium tetra-isopropoxide precursor. Nanoparticles were analyzed and standard methods were employed to evaluate the antimicrobial, antibiofilm, and cell cytotoxicity. UV–Vis spectroscopy confirmed the synthesis of TiO₂ NPs with a characteristic peak at 360 nm. Transmission electron microscopy (TEM) revealed roughly spherical particles (8.8 ± 3 nm diameter). A Z-average hydrodynamic diameter of 328.1 nm (PDI, 0.439) was revealed by dynamic light scattering (DLS). According to the energy-dispersive X-ray spectroscopy (EDX) results, oxygen was 42.39% and titanium was 45.93%. The X-ray diffraction (XRD) measurement confirmed a crystalline anatase structure, with a prominent peak at 25.3° 2θ. Fourier transform infrared (FTIR) detected the characteristic Ti–O-Ti and vibrational band at 403.31 cm⁻1. The nanoparticles demonstrated broad-spectrum antimicrobial activity with MICs of 78 μg/mL (E. coli), 156 μg/mL (C. albicans), 625 μg/mL (E. faecalis), and 2500 μg/mL (S. aureus and P. aeruginosa). At sub-MIC concentrations, TiO₂ NPs reduced biofilm formation in S. aureus by roughly 65.72% ± 0.01, in E. faecalis by 50.91% ± 0.02, and in P. aeruginosa by 38.4% ± 0.1. Cytotoxicity investigations revealed IC₅₀ values of 212.15 μg/mL (Caco-2) and 342.96 μg/mL (Vero cells), with a selectivity index of 1.62. Strong antiviral activity against HSV-1 was observed (74.74% inhibition at 60 µg/mL, EC₅₀ = 17.41 µg/mL, selectivity index = 19.7). Biogenic synthesis using B. cereus successfully produced highly crystalline, small-sized anatase TiO₂ nanoparticles demonstrating multifunctional biological activities including antimicrobial, antibiofilm, anticancer selectivity, and antiviral properties.

• Green synthesis via B. cereus yielded crystalline anatase TiO₂ NPs with nanoscale dimensions.

• TiO₂ NPs demonstrated broad antimicrobial/antibiofilm effects and selective anticancer activity.

• Strong antiviral potency against HSV-1 with excellent selectivity was observed

The online version contains supplementary material available at 10.1007/s00253-026-13771-8.

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