Assessment of impact of α‐Fe₂O₃ and γ‐Fe₂O₃ nanoparticles on phytoplankton species Selenastrum capricornutum and Nannochloropsis oculata

Abstract

In this study, the impact of alpha-iron oxide (α-Fe 2 O 3 , 20-40 nm) and gamma iron oxide (γ-Fe 2 O 3 , 20-40 nm) nanoparticles (NPs) on phytoplankton species Selenastrum capricornutum and Nannochloropsis oculata was investigated Characterizations of the NPs were systematically carried out by TEM, dynamic light scattering, zeta potential, X-ray diffraction, SEM, and Fourier transformation infrared spectroscopy. Acute toxicity was tested between 0.2 and 50 mg/L for each NP for a period of 72 hours exposure. γ-Fe 2 O 3 NP inhibited development of N oculata at the rate of 54% in 0.2 mg/L group with a high mortality rate of up to 82%. α-Fe 2 O 3 NPs were less toxic that induced 97% mortality on N oculata at 10 mg/L suspensions. In contrast, α-Fe 2 O 3 NP inhibited growth of S capricornutum strongly (73%) in 0.2 mg/L group. γ-Fe 2 O 3 NPs showed similar growth inhibition (72%) on S capricornutum in 10 mg/L suspensions.Despite the differential effects, the results indicated acute toxicity of α-Fe 2 O 3 and γ-Fe 2 O 3 NPs on N oculata and S capricornutum. K E Y W O R D S alfa-iron oxide, gamma-iron oxide, nanoparticle, phytoplankton, toxicity 1 | INTRODUCTION Iron (Fe) and iron oxide (Fe n O m ) nanoparticles (NPs) exhibit different properties, including low fusion and sintering temperature, superplastic behavior, high ductility and toughness, high thermal expansion coefficient, different thermo-physical properties, and high selfdiffusion coefficient. Iron is the most abundant transition metal in Earth's crust 1 in the form of Fe 2 O 3 or rust; there are around 16 identified Fe 2 O 3 in the nature. Due to its abundance, Fe 2 O 3 is commonly used as catalyzer, additive in durable pigments (coatings, paints, and colored concrete) and includes in hemoglobin molecules 2 besides its important roles in many biological and geological processes. The most common forms of iron oxides in the nature are magnetite (Fe 3 O 4 ), maghemite (γ-Fe 2 O 3 ), and hematite (α-Fe 2 O 3 ). These oxides are important materials in technological applications. 3 Small Fe 2 O 3 particles have been used in in-vitro examinations over 40 years. In order to synthesize magnetic NPs with appropriate surface chemistry, various physical, chemical, and biological methods have been applied. 4 Ferromagnetic NPs (smaller than 20 nm) exhibits unique magnetic properties (eg, superparamagnetism). Ferromagnetic materials cover elemental metals, alloys, oxides, and other chemical compounds magnetized by an exterior magnetic field. 5 Based on their unique mesoscopic, physical, chemical, thermal and mechanical properties, such as low toxicity, high surface area-to-volume ratio, superparamagnetic α-Fe 3 O 4 , α-Fe 2 O 3 , γ-Fe 3 O 4 , and γ-Fe 2 O 3 NPs have received much attention. They have been used in cellular therapy, cell labelling and targeting and in biomedical applications, including tissue regeneration, drug delivery and release, magnetic resonance imaging (MRI), hyperthermia, and magnetofection. 6,7

Cell size‐dependent species sensitivity to nanoparticles underlies changes in phytoplankton diversity and productivity

“…For example, thousands of metric tons of engineered nanoparticles are estimated to enter aquatic ecosystems each year (Keller et al., 2013, 2014), leading to their increasing concentration in water bodies (Sun et al., 2016), particularly in those impacted by urban run‐offs and effluents from wastewater treatment plants (Parker & Keller, 2019; Wang et al., 2020). While much effort has been devoted into understanding how nanopollution influences the environment, existing nanoecotoxicology research has largely focused on the responses of individual organisms and/or populations of the same species (Ates et al., 2020; Cheloni et al., 2016; Lodeiro et al., 2017; Zhang et al., 2016), and to a lesser extent, trophic transfer of nanoparticles along food chains/webs (Babaei et al., 2022; Khoshnamvand et al., 2020; Rajput et al., 2020). By contrast, we know little about how nanoparticles affect competitive interactions among species, which are among the most important biotic factors shaping the structure of natural ecological communities (Connell, 1983; Gurevitch et al., 1992; Schoener, 1983).…”

“…Phytoplankton are dominant primary producers of aquatic ecosystems (Cloern et al., 2014; Wang et al., 2019), where significant amounts of engineered nanoparticles have been released (Keller et al., 2013). While an increasing number of studies have addressed the toxicity of nanoparticles toward phytoplankton, these studies have mostly focussed on individual phytoplankton species (Ates et al., 2020; Bielmyer‐Fraser et al., 2014; Lodeiro et al., 2017). It is largely unknown how the presence of nanoparticles would influence phytoplankton interactions and ecosystem functions.…”

Developmental effects on Daphnia magna induced by titanium dioxide and iron oxide mixtures

“…In the aquatic environment, the accumulation of NPs of TiO 2 from discharges (e.g., nano paint, cosmetics and sunscreens, food additives) can disturb the environment and affect aquatic organisms (e.g., phytoplankton, Daphnia magna, fish, and bacteria) (Zhu et al 2010b, Fan et al 2016, Novak et al 2018, Liu et al 2019. Moreover, iron oxide NPs (Fe 2 O 3 ) are also frequently used in several sectors, such as water treatment, magnetic storage, cosmetics, and the chemical industry) (Ates et al 2020). However, occupational exposure to iron oxide nanoparticles leads to health and environmental risks (Farsi et al 2021).…”

Advanced hematite nanomaterials for newly emerging applications

“…Due to the combined advantages including rich abundance, low cost, and diverse species (metals/alloys, compounds and their composites) as well as praiseworthy physicochemical characteristics originating from the magical d electron configurations, functional materials based on transition metal elements have attracted extensive research interest. 4–10 Among them, α-Fe 2 O 3 with iron as the second most abundant metal element in the crust possesses the advantages of chemical stability, 11,12 redox activities, 13 low toxicity and cost, 14 etc. , and has been systematically studied for decades and widely applied in diverse fields including secondary batteries, 15,16 supercapacitors, 17 Fenton-like catalysts, 18 adsorbents, 19 photochemical oxidation reactions, 20,21 magnetics, 22 water–gas shift reaction, 23 and elevated-temperature CO oxidation.…”