Minseo Kim, Yeonah Jang, Maya Stolbova, Ki Youb Park*
(Supervised by Ki Youb Park, collaborators from St. Odulphuslyceum in Netherlands)
Korea Science Academy of KAIST
*Email:
Introduction
Microplastics, plastic particles smaller than 5 mm, pose significant environmental and health risks. Originating from the breakdown of larger plastics or industrial production, these particles contaminate ecosystems, affecting plants, animals, and humans. This study examines their impact on three biological models: aquatic organisms (Daphnia spp.), plants (Lolium perenne L. and Hordeum vulgare L.), and human intestinal cells (Caco-2 cells).
By integrating findings across plant, aquatic, insect, and human cellular systems, this study sheds light on the pervasive risks of microplastic pollution while exploring innovative solutions for plastic degradation. It highlights the urgent need for interdisciplinary approaches to mitigate plastic pollution’s far-reaching consequences and safeguard ecosystem and human health.
Methods
Plant Research: Barley and ryegrass seeds were soaked for germination and then exposed to Polystyrene microplastics beads of different sizes (100 nm, 1000 nm, 2000 nm) and surface charge (positive, negative). Seeds were grown on gauze for 12 days under controlled conditions. Growth parameters such as stem length and biomass were recorded, and root samples were analyzed for microplastic presence using ethanol washing and microscopy.
Daphnia Research: To assess microplastic toxicity in aquatic environments, Daphnia were exposed to microplastic beads of various sizes and concentrations (10 µL/mL, 15 µL/mL, 20 µL/mL microplastic/water), and surface charge. Each test group received different microplastic doses, and survival rates were monitored over two days to evaluate potential ecological risks.
Mealworm Research: Mealworms were divided into two groups—one fed a standard diet and another fed styrofoam—to study plastic biodegradation. Their excreta were collected and analyzed for chemical composition, with potential implications for plastic breakdown and environmental impact.
Caco-2 Cell Research: Excreta from mealworms fed with different diets (bran/cucumber vs. styrofoam) were processed into solutions using DMSO and ethanol. These solutions were applied to human intestinal (Caco-2) cells cultured in 96-well plates. Cell viability was measured using a WST-8 colorimetric assay to determine potential cytotoxic effects.
This research integrates findings across different biological systems to understand the risks of microplastics and explore potential biodegradation solutions.
Results
The figure’s blue bars and the gray line are each total weight and stem length of barleys (left panel) and ryegrass (right panel) 12 days after treating microplastic. For each condition, two wells which 5 seeds are contained are used. They don’t show any significant relationship.
The figure shows barley roots under the fluorescence microscopy. The bright dots on the roots are microplastic. When plants are treated with microplastics, the plastic is not only on the outside of the plant’s roots, but also on the inside. However, microplastics did not inhibit plant growth.
The figure shows microplastics entered to the daphnia’s gut. Especially for dead Daphnia a lot of microplastics attached to its body compared to live Daphnia.
To ensure the reliability of the experiment, this value represents the average of three experiments under the same conditions. The survival rate was not highly dependent on the size of the microplastics. However, positively charged microplastic and high concentrations of microplastic tend to lower Daphnia’s survival rate.
To ensure the reliability of the experiment, this value represents the average of three experiments under the same conditions. Even when excretions are treated, they are not as toxic as those treated with (high) EtOH.
Summary
- Plant Experiment: Microplastics were detected both externally and internally in root tissues. Growth rate was inversely related to particle size and negative surface charge.
- Daphnia Experiment: Microplastics accumulated in the digestive tract, especially in deceased specimens. Survival rates decreased with positively charged microplastics at high concentrations, regardless of particle size.
- Caco-2 Cell Experiment: Cell viability remained largely unaffected by microplastic exposure through tested excretion methods. Potential for future use of IR spectroscopy to analyze fecal components.
This study demonstrates that microplastics can penetrate plant root tissues and negatively affect plant growth, particularly when particles are larger and negatively charged. In Daphnia, microplastics were observed within the gut, and exposure to positively charged and highly concentrated microplastics reduced their survival. For Caco-2 cells, no significant reduction in viability was observed across tested excretion types. We may also be able to use instruments such as infrared (IR) spectroscopy to determine the composition of the feces to identify specific substances that affect the growth of cells in the presence and absence of styrofoam. For plant experiment, other types of plants can be used and also not only the roots, but the stems can be examined for microplastics. For Daphnia experiment, concentration and type of microplastics can be changed.
References
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