The pervasive environmental presence of nanoplastics (NPs) and microplastics (MPs) has raised significant concerns about their potential neurotoxic effects, particularly their capacity to infiltrate and disrupt brain function. This study systematically evaluates the biodistribution, neural activation, and behavioral consequences of various sizes of NPs and MPs (26 nm, 1 μm, 20 μm, and 120 μm) following intranasal administration in mice at 10 mg/kg body weight for 7 days. Fluorescence microscopy revealed that while 20 μm and 120 μm MPs did not penetrate brain tissue, 1 μm MPs were unequivocally identified within neural structures. Whole-brain cFOS immunofluorescence mapping indicated significant activation of stress-related brain regions, including the olfactory bulb (OB), lateral septum (LS), bed nucleus of the stria terminalis (BNST), and paraventricular nucleus (PVN), in mice exposed to 26 nm NPs and 1 μm MPs. Behavioral analysis using 3D autonomic screening demonstrated spontaneous behavioral abnormalities in both groups, with further assessments revealing pronounced anxiety-like behaviors exclusively in the 1 μm MP-exposed animals. Metabolomic profiling of the hypothalamus showed distinct alterations in metabolic pathways in both the 1 μm MP and 26 nm NP groups compared to controls. These findings underscore a size-dependent neurobehavioral risk associated with NP and MP exposure, highlighting the heightened vulnerability posed by micron and sub-micron plastic particles to brain integrity and function. This study calls for deeper mechanistic investigations into the neurological impact of plastic pollutants to inform risk assessments and public health strategies.
 

microplastics and nanoplastics,brain,mental health,spontaneous behavioral abnormalities,anxiety-like behavior