Olfactory transport efficiency of the amorphous and crystalline manganese oxide nanoparticles

The ability to deliver particulated xenobiotics and therapeutic drugs directly from the nasal cavity to the central nervous system, bypassing the hemato-encephalic barrier, determines a high importance of investigation of factors influencing this process. It was shown that the bioavailability of solid particles is influenced by their size and surface charge. At the same time, the impact of a crystal structure (crystalline/amorphous) has been poorly investigated. In this study, using sexually mature male C57BL/6J mice, we analyzed the efficiency of the nose-to-brain transport of crystalline and amorphous manganese oxide nanoparticles. T1-weighted magnetic resonance imaging (MRI) was used to evaluate the accumulation of manganese nanoparticles in olfactory bulb (OB) and olfactory epithelium (OE). So, it has been established that amorphous particles have higher accumulation rate in OE and OB in comparison with crystalline particles after their intranasal administration. The unequal ability of amorphous and crystalline particles to overcome the mucosal layer covering the OE may be one of the possible reasons for the different nose-to-brain transport efficiency of particulated matter. Indeed, the introduction of mucolytic (dithiothreitol) 20 minutes prior to intranasal particle application did not influence the accumulation of amorphous particles in OE and OB, but enhanced the efficiency of crystalline nanoparticle entry. Data on the different intake of amorphous and crystalline nanoparticles from the nasal cavity to the brain, as well as the evidence for the key role of the mucosal layer in differentiating the penetrating power of these particles will be useful in developing approaches to assessing air pollution and optimizing the methods of inhalation therapy.