Size and shape matter: investigating the cytotoxicity and cytochrome P450 inhibitory potency of ZnO nanoparticles
Publication Date
July 25, 2026
Creator
Chong Ce Lynn
Abstract
In recent years, zinc oxide nanoparticles have attracted increasing interest due to their well-demonstrated potential in various biomedical applications. However, their distinct physicochemical properties, including nanoscale dimensions, high surface area-to-volume ratio, increased surface reactivity, ion release, and photocatalytic activity, may give rise to biological and toxicological effects that differ substantially from those of bulk ZnO, raising concerns about their potential unintended risks to human health. The liver is the primary site of xenobiotic metabolism and a major target for nanoparticle accumulation, making it particularly susceptible to ZnO nanoparticle-induced hepatotoxicity. Therefore, this study aimed to determine how the physicochemical properties of ZnO nanoparticles, particularly size and shape, influence hepatic toxicity and CYP-mediated metabolic function, with specific focus on cytotoxicity, oxidative stress generation, apoptotic signaling, cytochrome p450 enzyme inhibition, and cytochrome p450 gene expression.
Accordingly, ZnO nanorods and nanodisks of comparable primary sizes were synthesized using chemical precipitation and sol–gel methods, respectively, to evaluate shape-dependent effects, while commercial ZnO particles of different size categories (<50 nm, <100 nm, and bulk) were included to assess size-dependent effects. Subsequent physicochemical characterization using field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), ultraviolet–visible (UV–Vis) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), and electrophoretic light scattering (ELS) confirmed clear differences in size and shape among the ZnO formulations, which were reflected in their biological and enzymatic effects.
ZnO nanoparticles exhibited concentration-, size-, and shape-dependent effects on hepatic cellular toxicity and CYP-mediated metabolic function (p < 0.05). In HepG2 cells, smaller ZnO nanoparticles, particularly ZnO <50 nm, exhibited the strongest size-dependent cytotoxicity, while ZnO nanorods showed greater shape-dependent cytotoxicity. These effects were accompanied by increased intracellular ROS accumulation and alterations in the expression of stress- and apoptosis-related genes, including SOD1, JNK, P53, BAX, and BCL2, suggesting that oxidative stress may contribute to ZnO nanoparticle-induced hepatic cellular toxicity. In parallel, ZnO nanoparticles significantly inhibited CYP enzyme activities, indicating potential disruption of CYP-mediated metabolic function. CYP2C9 was the most susceptible isoform, followed by CYP3A4, CYP2D6, and CYP2C19. The inhibitory potency was dependent on nanoparticle size and shape, with ZnO <50 nm showing the strongest size-dependent inhibition (IC₅₀ = 12.76–64.24 µg/mL; Kᵢ = 8.20–46.52 µg/mL), while ZnO nanodisks exhibited stronger shape-dependent inhibition than nanorods (nanodisks: IC₅₀ = 14.04–51.52 µg/mL, Kᵢ = 8.30–25.25 µg/mL; nanorods: IC₅₀ = 28.01–89.82 µg/mL, Kᵢ = 9.44–74.07 µg/mL). Kinetic analyses using Lineweaver–Burk plots revealed that ZnO nanoparticles predominantly exhibited mixed-type inhibition, suggesting that ZnO nanoparticles may interact with both free CYP enzymes and enzyme–substrate complexes in a size- and shape-dependent manner. Molecular docking analysis further supported these kinetic findings, demonstrating favourable interactions between ZnO nanoparticles and key amino acid residues within CYP binding regions. Interestingly, despite the inhibition of CYP catalytic activity, ZnO <50 nm significantly upregulated CYP2C9 and CYP3A4 gene expression in HepG2 cells (p < 0.05), suggesting that CYP transcriptional activation may represent a cellular response to nanoparticle-induced stress and CYP inhibition rather than a direct increase in enzymatic activity.
Overall, the findings highlight the complex interplay between ZnO nanoparticle physicochemical properties, particularly size and shape, and their biological interactions in shaping hepatic cellular toxicity and CYP-mediated metabolic function. This study underscores the potential risks of ZnO nanoparticle-induced hepatotoxicity and nanoparticle–drug interactions in clinical and pharmaceutical settings, providing important insights to support the safer evaluation and biomedical application of ZnO nanoparticles.
Item Type
ethesis
Thesis Type
PhD
Supervisors
University of Nottingham, Malaysia
Monash University Malaysia
Subjects (LC)
Associated Schools / Departments
Related Publication URL(s)
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