Preparation and evaluation of drug-loaded gelatin nanoparticles for topical ophthalmic use.

Gelatin nanoparticles encapsulating pilocarpine HCl or hydrocortisone as model drugs were produced using a desolvation method. The influence of a number of preparation parameters on the particle properties was investigated. For the pilocarpine HCl-loaded spheres, an influence of the pH during particle preparation on the size was observed. Slightly negative zeta potential values were measured for all samples. In the case of pilocarpine HCl-loaded spheres, no influence of the gelatin type or the pH level was observed, which could be attributed to the shielding effect of ions present in the dispersion medium. When hydrocortisone was entrapped, a difference in zeta potential value between gelatin type A and gelatin type B particles was measured. A high pilocarpine HCl entrapment was established. Hydrocortisone was complexed with cyclodextrins in order to increase its aqueous solubility. The drug encapsulation was lower than in the case of pilocarpine HCl, but still amounted to approximately 30-40%. Compared to the aqueous drug solutions, a sustained release for both drugs was observed. The release kinetics of pilocarpine HCl are close to zero order, and no significant differences were measured between the various preparations. In the case of hydrocortisone, the release data suggests a difference in release rate depending on the type of cyclodextrin employed.