Spray-dried mucoadhesive microspheres: preparation and transport through nasal cell monolayer

The purpose of this research was to prepare spray-dried mucoadhesive microspheres for nasal delivery. Microspheres composed of hydroxypropyl methylcellulose (H), chitosan (CS), carbopol 934P (CP) and various combinations of these mucoadhesive polymers, and maltodextrin (M), colloidal silicon dioxide (A), and propylene glycol (P) as filler and shaper, were prepared by spray-drying technique. Using propranolol HCl as a model drug, microspheres were prepared at loadings exceeding 80% and yields between 24% and 74%. Bulky, free flowing microspheres that had median particle size between 15 and 23 mum were obtained. Their zeta potential was according to the charge of polymer. Adhesion time of mucoadhesive microspheres on isolated pig intestine was ranked, CS > CP:H > CP > H, while the rank order of swelling was CP > CS > H. Increasing the amount of CP in CP:H formulations increased the percentage of swelling. Infrared (IR) spectra showed no interaction between excipients used except CS with acetic acid. The release of drug from CP and CP:H microspheres was slower than the release from H and CS microspheres, correlated to their viscosity and swelling. Long lag time from the CP microspheres could be shortened when combined with H. The permeation of drug through nasal cell monolayer corresponded to their release profiles. These microspheres affected the integrity of tight junctions, relative to their swelling and charge of polymer. Cell viability was not affected except from CS microspheres, but recovery could be obtained. In conclusion, spray-dried microspheres of H, CS, CP, and CP:H could be prepared to deliver drug through nasal cell monolayer via the opening of tight junction without cell damaging.