Impact of amino acids on the properties of nasal dry powders

Spray freeze drying is an appropriate technique for producing nasally delivered inhalable encapsulated drugs since producing microparticles with a diameter larger than 100 μm. Amino acids are commonly used to promote particle formation and increase encapsulated drugs' stability. Nasally delivered spray freeze dried powders behave differently according to the amino acids used. Leucine is the most widespread one since it increases the stability of the encapsulated compound. Other amino acids, thought, could be a valid alternative. For instance, glutamine, arginine, tyrosine, and lysine show a percentage difference between the liquid chromatography peaks of pure and encapsulated bovine serum albumin of about 24, 3, 16, and 3, respectively. Moreover, the average detachment force between microparticles containing one of these amino acids and artificial nasal mucosa is 1.7 N. Minor differences are recognized in penetration and toxicology performed on nasal cells using drug-loaded powder formulations. However, the distribution in the nasal cavity highly differs. Arginine allows the drugs to distribute homogeneously in the whole cavity, while lysine allows for targeting the olfactory region.