Luminescent nanocrystals and quantum dots have great potential for use as fluorescent markers in biology and medicine. However, their first generations were based on the heavy-metal core, which was unstable and shed heavy-metal ions into biological media. This, coupled with a lack of information on their biodistribution and pharmacokinetics, rendered them unusable for purposes outside research. The recently developed nonheavy metal nanocrystals are a promising material for future medical use. Yet, the controversies over their application, absorption and biodistribution remain. Various recent papers present different results on the uptake of nanocrystals and on their intracellular and organ distribution. In our study, we focused on the question of how the size and shape of nanocrystals affect their duodenal absorption after intragastric gavage (IG) and distribution to the liver. Commercial bulk nanoparticles and hydrothermal nanoparticles produced at the Institute of Physics PAS were the same in composition and excitation-emission range, but significantly different in shape and size. Adult mice (n = 24) aged 3-6 months were kept in standard living conditions (12 h day-night cycle), fed ad libitum with unobstructed access to water. Following a 1-week adaptation period, an RO water suspension of nanoparticles (50 µg/ml) was administered by IG. No changes in the behaviour of the mice or pathophysiological changes in their organs were observed following IG. The control group received an identical volume of RO water by IG. Cross-sections of the organs were examined both qualitatively and quantitatively by confocal microscopy and scanning cytometry. Following IG, both types of nanoparticles entered the duodenum in a similar time, but only the smaller, elongated hydrothermal nanoparticles were absorbed through the intestinal epithelium and distributed throughout internal organs (p ≤ 0.001). In conclusion, we found that the size and shape of nanocrystals is crucial for their bioavailability.
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