A holistic NMR framework to understand environmental impact: Examining the impacts of superparamagnetic iron oxide nanoparticles (SPIONs) in Daphnia magna via imaging, spectroscopy, and metabolomics

Abstract

Superparamagnetic iron oxide nanoparticles (SPIONs) are a contaminant of emerging interest, often used in the medical field as an imaging contrast agent, with additional uses in wastewater treatment and as food additives. Although the use of SPIONs is increasing, little research has been conducted on the toxic impacts to living organisms beyond traditional lethal concentration endpoints. Daphnia magna are model organisms for aquatic toxicity testing with a well understood metabolome and high sensitivity to SPIONs. Thus, as environmental concentrations continue to increase, it is becoming critical to understand their sub‐lethal toxicity. Due to the paramagnetic nature of SPIONs, a range of potential nuclear magnetic resonance spectroscopy (NMR) experiments are possible, offering the potential to probe the physical location (via imaging), binding (via relaxation weighted spectroscopy), and the biochemical pathways impacted (via in vivo metabolomics). Results indicate binding to carbohydrates, likely chitin in the exoskeleton, along with a decrease in energy metabolites and specific biomarkers of oxidative stress. The holistic NMR framework used here helps provide a more comprehensive understanding of SPIONs impacts on D. magna and showcases NMR's versatility in providing physical, chemical, and biochemical insights.

13C‐depleted algae as food: Permitting background free in‐vivo nuclear magnetic resonance of Daphnia magna at natural abundance

“…From MRI and microscopy, $15% of the volume of the D. magna is from its digestive tract, leading to a very rough estimate that a D. magna could contain $30 μg of algae at any one time, or about 600-900 μg for a batch of 20-30 adults. 24 This is at least 15 times less than the 15 mg used in Figures 1 and 2. As such, it can be extrapolated that the signal remaining from the depleted algae is below detection limits (defined as 3:1 SNR) by at least a factor of 7 under invivo conditions.…”

“…Typically for in‐vivo NMR, 20–30 D. magna are used, with the dry weight of adults ~200 μg 23 leading to 4–6 mg of D. magna biomass in the coil. From MRI and microscopy, ~15% of the volume of the D. magna is from its digestive tract, leading to a very rough estimate that a D. magna could contain ~30 μg of algae at any one time, or about 600–900 μg for a batch of 20–30 adults 24 . This is at least 15 times less than the 15 mg used in Figures 1 and 2.…”

Development of a Simple Cost Effective Oxygenation System for In Vivo Solution State NMR in 10 mm NMR Tubes

“…The absence of liquid flow lines is highly beneficial to mitigate potential damage to expensive NMR probes from clogs and leaks. The internal current which is generated from the pressure differentiation induced by the rising oxygen bubbles allows for mixing and the lack of filters allows particulate food (most commonly algae) or even particulate contaminants (i.e., nanoparticles 63 or microplastics 64 ) to be included. Furthermore, as fluid is restricted to the volume of the NMR tube it should allow the use of expensive contaminants/toxins/drugs, as much smaller amounts would be required to reach the same concentration vs a larger flow system with an external reservoir and recirculating flow lines in/out the NMR spectrometer.…”