Synthesis, characterization and evaluation of hyaluronic acid-based polymers for nasal delivery

Epidemiological research has found that between 5 and 12 percent of the population suffers from chronic rhinosinusitis. Patients are dealing with local side effects such as nasal dryness, sporadic sneezing, and nasal pain in addition to the inflammation. The aim of this study was to synthesize a polymer based on hyaluronic acid in order to provide lubrication combined with a ligand leading to a covalent binding on the nasal mucosa. Hyaluronic acid (HA) was modified with L-cysteine ethyl ester hydrochloride (CYS) via amid bond formation. Ellman's assay, together with spectroscopic techniques like IR and ¹H NMR, confirmed that HACys had been successfully synthesized. It was demonstrated that HACys is safe for administration on the nasal mucosa. The mucoadhesive potential was determined by 3.26-fold with the rotating cylinder assay and 1.4-fold in terms of bioadhesive examination, respectively. Further, the stability of the modified polymer was improved by 7.6-fold compared to the unmodified polymer. Spraying the formulation on the nasal mucosa, the residence time of a model drug was 1.74-fold prolonged at the site of action compared to unmodified polymer. In light of these findings, modified hyaluronic acid (HACys) displayed compelling properties such as lubricity, targeted application, long-lasting effect, and safety and therefore could be an excellent candidate for nasal application.