Well-Defined Morphology Enables Tuning of the Antimicrobial Activity of ZnO Nanoparticles

High Resolution Image Download MS PowerPoint Slide The antimicrobial activity of zinc oxide nanoparticles (ZnO-NPs) is intimately linked to their physicochemical properties, yet the specific contribution of morphology remains insufficiently understood due to current Zn 2+ leaching and reactive oxygen species (ROS) generation. This work investigates the key role of ZnO-NPs morphology in governing the biological performance. Spherical (ZnO-S, 60–70 nm diameter) and needle-like (ZnO-N, ∼800 nm length) nanostructures were synthesized via a Metal–Organic Framework template-approach and hydrothermal synthesis, respectively, achieving precise morphological control. SEM characterization confirmed the distinct architectures produced, while XRD and Raman spectroscopy verified a wurtzite crystalline phase with minimal oxygen vacancies, preventing Zn 2 + leaching. Antibacterial assays revealed that needle-like morphology displayed superior inhibition against Escherichia coli and Staphylococcus aureus, showing an inhibition of 90% and 80%, respectively, at a ZnO concentration of 1.2 mg mL –1 . In contrast, spheric particles showed a concentration-dependent effects with a maximum inhibition of 50% under the same particle concentration. Antifungal activity of the ZnO-NPs was evaluated through the radial growth of Aspergillus niger and Penicillium citrinum using the Gompertz model. A needle-like loading of 0.055 mg cm –2 was sufficient to rapidly reduce the specific growth rate of A. niger from 0.049 h –1 to 0.013 h –1, while P. citrinum showed higher resistance irrespective of the morphology. Although both particles inhibited fungal growth, distinct morphology-driven mechanisms were observed: ZnO-S interfered with conidiation in A. niger, whereas ZnO-N rapidly suppressed colony expansion. Against P. citrinum, ZnO-N minimally altered the radial growth but strongly reduced spore production. Finally, ROS quantification revealed higher ROS generation in ZnO-S (74.8 ± 4.9 μg H 2 O 2 eq/mg NP) compared to ZnO-N (60.4 ± 4.4 μg H 2 O 2 eq/mg NP), highlighting morphology as a key determinant of antimicrobial activity. By directly linking nanoscale morphology with an antimicrobial mode of action, this study establishes morphology as a design principle for ZnO-based nanomaterials targeting specific pathogens.