Ecotoxicity assessment of mixed metal oxide nanomaterials and MOFs

WU, Lisi (2026). Ecotoxicity assessment of mixed metal oxide nanomaterials and MOFs. University of Birmingham. Ph.D.

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Abstract

Nanomaterials (NMs) and metal-organic framework (MOFs) materials provide high surface-area-to-volume ratios and tunable chemistry that enable agricultural uses such as targeted nutrient and pesticide delivery. Because field application can lead to direct exposure of crop plants and soil biota and indirect exposure of aquatic organisms through run-off, a balanced assessment of agronomic benefit and hazard is essential. We investigated two representative molecular organic framework (MOFs) - Fe-BTC and HKUST-1 (Cu-BTC) - and two metal oxide nanomaterials-iron oxide (Fe\(_2\)O\(_3\)) and zirconium dioxide (ZrO\(_2\))-selected from EU-funded projects and chosen for their relevant constituent metals (Fe, Cu, Zr) for comparison. Materials were characterized by size, zeta potential and electron microscopy.

Direct plant effects were evaluated in cucumber (Cucumis sativus L.) using (i) soil exposure from seedling stage through 10 weeks, followed by biomass measurements and multi-element profiling (macronutrients and micronutrients, including constituent metals), and (ii) a seed priming protocols with early post-emergence monitoring and elemental analysis. Mechanistic responses were probed by assessing protein expression and antioxidant enzyme activities. To address off-target risks, zebrafish embryo cells (ZF4) were exposed in vitro, cytotoxicity and modes of cell death were quantified by flow cytometry, and cellular uptake of the NMs was measured by ICP-OES and impacts on plants were compared under both exposure scenarios.

HKUST-1 significantly promoted cucumber growth, increasing fruit, leaf and stem biomass. In contrast, Fe-BTC suppressed cucumber growth at higher concentrations. In ZF4 cells, both ZrO\(_2\) and Fe\(_2\)O\(_3\) produced time-dependent cytotoxicity with apoptosis and cell death at high concentrations.

These results indicate that nano-enabled agriculture can deliver measurable growth benefits (especially with HKUST-1) but that composition-dependent and dose-dependent risks exist, particularly for non-target aquatic cells with NMs of similar compositions to the selected MOFs at high concentrations. The findings support the need for establishing material-specific safe-use windows and exposure-minimization strategies for sustainable development.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):