Bigger or Smaller? Size and Loading Effects on Nanoparticle Uptake Efficiency in the Nasal Mucosa

PLGA nanoparticles hold great promise for nasal administration, but only with careful design will efficient, effective, and safe delivery systems be developed. To better understand the size dependence of nasal epithelial uptake, PLGA nanoparticles (60 nm or 125 nm) loaded with Nile Red were prepared, and their uptake into excised sections of bovine nasal respiratory or olfactory mucosa was measured for 30 or 60 min. The epithelial layer and the submucosal tissues were separated, and the amount of Nile Red was used to calculate the number of nanoparticles in each tissue region. Both particle sizes were able to be internalized into the nasal tissues in as little as 30 min, but their total uptake represented less than 5% of the nanoparticles available. Nanoparticles were present both in the epithelial cells and in the submucosal tissues, and greater numbers of the 60-nm particles were present in the submucosa than the epithelium, while greater numbers of the 125-nm particles remained in the epithelial cell layer. The amount of Nile Red recovered from the mucosal tissues after exposure to 125-nm nanoparticles was at least 2-fold greater than from the 60-nm nanoparticles, however, due to the higher (~ 9-fold) loading capacity of the larger particles. The greater mass transfer of the Nile Red from the larger particles suggests that it may not be necessary to develop small nanoparticulate delivery systems for efficient drug delivery via the nasal mucosa. Well-designed nanoparticles with diameters > 100 nm show good uptake into the nasal epithelium and are capable of transfer to the submucosal tissues, near the location of significant populations of blood and lymphatic vessels. Graphical abstract.