Abstract

Nanoparticles (NPs) have attracted considerable attention in biomedical research due to their unique physicochemical properties and potential applications. Cerium oxide (CeO₂) nanoparticles, in particular, have shown promise for their antioxidant and neuroprotective properties. However, concerns remain regarding their safety and potential neurotoxicity, especially with long-term or high-dose exposure. Although research into their biomedical use is expanding, limited in vivo evidence exists on how cerium oxide nanoparticles affect brain tissue at the histological level. This study aimed to examine the histopathological impact of intraperitoneally administered cerium oxide nanoparticles in Mus musculus mice over four weeks. Mice were divided into two groups: one received 1 mL of physiological saline (control), and the other received 1 mL of a solution containing 3.75 µL of cerium oxide daily. After treatment, brain tissues were analyzed histologically. The treated group showed notable alterations in white matter, neurofibers, and glial cells, including glial cell aggregation, necrosis, and degeneration of white matter. These findings provide direct in vivo evidence of potential neurotoxic effects caused by cerium oxide nanoparticles. The study highlights the importance of careful dose regulation and calls for more research into their mechanisms of toxicity and long-term effects to ensure safe biomedical application.

Highlight:

• Cerium oxide nanoparticles caused brain tissue damage in mice.

• Key effects included glial cell necrosis and white matter degeneration.

• Highlights need for safe dosing and long-term toxicity studies.

Keyword: Rabbits, Nanoparticles, Brain, Tissue, Damage

Introduction

Nanoparticles are elemental molecules that range in size from 1 nm to 100 nm and have a variety of morphologies, including amorphous, crystalline, and spherical [1]. In the natural world, biological, geological, climatic, and cosmological processes may all create nanoparticles [2, 3]. Cerium is a rare earth metal with an atomic number of 58 that is a member of the lanthanide class. It exists in two oxidation states, +3 and +4, and is the most prevalent rare earth metal. [4]. The finest antioxidants are nanoceria, according to in vitro studies. [5], in addition to in vivo To learn more about the effects on organs such the liver, spleen, kidneys, lungs, and brain, several in vivo experiments were conducted on rats and mice. [6]. Nanoceria retained the expressed neuronal function and increased the longevity of brain cell cultures, according to another research. According to one study, the fluorite crystalline lattice structure of cerium oxide aids in ROS neutralisation. [7].

Materials and Techniques

A. Materials

This study utilized BALB/C strain Mus musculus L. white laboratory mice as experimental subjects. The mice were housed in standard plastic cages under controlled environmental conditions, including a regulated temperature of 20–25°C and a 12-hour light/dark cycle. The animals were provided with a specific, standardized diet throughout the experimental period. The primary substance used in the treatment was cerium oxide, which was prepared in a concentration of 750 μL for experimental use.

B. Techniques

The mice were divided into eight groups for the purpose of treatment comparison. Intraperitoneal (IP) injections were administered into the lip region. The control group received daily injections of 1 mL normal saline solution for four weeks. The treatment group, on the other hand, received 1 mL of a cerium dioxide solution daily, consisting of 3.75 μL of raw cerium oxide material diluted in 996.25 μL of physiological solution. Upon completion of the four-week treatment period, all mice were euthanized. Subsequently, the brains were carefully extracted by Prof. Dr. Ali Abid-Allateef and immersed in a 10% formalin solution for histological processing and analysis, which was conducted in a specialized laboratory facility.

Results and discussion

A. Result

Some studies on nanomaterials show negative effects, while others indicate positive protective results and pointed that it spreads into the bloodstream or even into the central nervous system.(8).

The present study in showed that administration of nanoparticles (cerium oxide ) for thirty days Figure (2) induce histopathological several Alterations in brain tissue, particularly in the white matter, neurofibers, and glial cells, may correlate with the administered dosage or duration of exposure as compared to normal brain tissue (see Figure 2).

Figure 1.Mice brain with normal tissue structure

Figure 2.

Figure 3.

B. Discussion

The cross-section of brain tissue in the current study (Figure 3) demonstrated that a four-week administration of cerium oxide induced histopathological alterations in brain tissue, particularly in the white matter, neurofibers, and Glial cells. The time of administration and the injection dosage of cerium oxide nanoparticles (3.75 µL) might be the cause of this.Research indicates that the synthetic materials employed in cerium compounds influence control mechanisms, protein absorption, and translational toxicity [9,10]. A research conducted by Semahir in 2021 found that cerium oxide causes histological changes in the liver, kidney, and lung tissues of mice given the injection for 15 and 30 days. Additionally, cerium oxide resulted in elevated levels of AST and ALT, indicating adverse histological changes in liver tissue. The recovery procedure of some components will assist in assessing the toxicity of the compounds. Certain cells harbour rapidly diversifying ceria particles. For instance, following 24 hours of exposure to air-filtered differential ceria particles, 80% of the differential independence inside A549 mission cells was established, with the recording rate and variability constrained by the transmission mass[13,16]. Heidari et al. (2019) found that TiO2, depending on the dosage administered to mice, led to neuronal damage and subsequently heightened the likelihood of Parkinson's disease. [14,17]. Cerium oxide nanoparticles are presently under investigation for their usefulness in several neurodegenerative conditions and have demonstrated potential neuroprotective effects.

Conlcusion

The study concludes that intraperitoneal administration of cerium oxide (CeO₂) nanoparticles over a four-week period induces significant histopathological alterations in the brain tissue of Mus musculus mice. These alterations include degeneration of white matter, aggregation of glial cells, and glial cell necrosis. The observed effects are likely associated with the dosage and duration of nanoparticle exposure. While some prior studies highlight the neuroprotective potential of cerium oxide nanoparticles, the findings of this research underscore their possible neurotoxic effects, particularly when used without careful dose regulation. These results emphasize the need for further investigation into the mechanisms of toxicity and the therapeutic potential of cerium oxide nanoparticles in neurodegenerative contexts, ensuring their safe and effective application in biomedical fields.

Acknowledgments

I express my profound gratitude to Prof. Dr. Ali Abid of Allateef College of Education for Pure Sciences at the University of Basrah for the preparation of histoslids.

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