RESUMEN

Tacrolimus (FK506) was used to prevent corneal allograft rejection in patients who were resistant to steroids and cyclosporine. However, the formulation for FK506 ocular delivery remained a challenge due to the drug's high hydrophobicity, high molecular weight, and eye's physiological and anatomical constraints. The aim of this project is to develop an ocular delivery system for FK506 based on a combined strategy of niosomes and mucoadhesive hyaluronic acid (HA), i.e., FK506HA-coated niosomes, which exploits virtues of both niosomes and HA to synergistically improve ophthalmic bioavailability. The FK506HA-coated niosomes were characterized with particle size, zeta potential, and rheology behavior. Mucoadhesion of FK506HA-coated niosomes to mucin was investigated through surface plasmon resonance in comparison with non-coated niosomes and HA solution. The results showed that niosomes possessed adhesion to mucin, and HA coating enhanced the adhesion. The in vivo precorneal retention was evaluated in rabbit, and the results showed that HA-coated niosomes prolonged the residence of FK506 significantly in comparison with non-coated niosomes or suspension. Aqueous humor pharmacokinetics test showed that area under curve of HA-coated niosomes was 2.3-fold and 1.2-fold as that of suspension and non-coated niosomes, respectively. Moreover, the synergetic corneal permeability enhancement of the hybrid delivery system on FK506 was visualized and confirmed by confocal laser scanning microscope. Overall, the results indicated that the hybrid system facilitated FK506 ocular delivery on mucoadhesion, precorneal retention, aqueous humor pharmacokinetics and transcorneal permeability. Therefore, HA-coated niosomes may be a promising approach for ocular targeting delivery of FK506.

Asunto(s)

Humor Acuoso/metabolismo , Córnea/metabolismo , Ácido Hialurónico/química , Liposomas/química , Soluciones Oftálmicas/farmacocinética , Tacrolimus/farmacocinética , Adsorción , Animales , Disponibilidad Biológica , Portadores de Fármacos/química , Inmunosupresores/administración & dosificación , Inmunosupresores/química , Inmunosupresores/farmacocinética , Microscopía Confocal , Soluciones Oftálmicas/administración & dosificación , Soluciones Oftálmicas/química , Permeabilidad , Conejos , Reología , Tacrolimus/administración & dosificación , Tacrolimus/química

RESUMEN

The aim of the study is to prepare flurbiprofen axetil nanoemulsion-in situ gel system (FBA/NE- ISG) and observe its ocular pharmacokinetics, rheological behavior, TEM images, irritation and cornea retention. Production of nanoemulsion was based on high-speed shear and homogenization process, and then mixed with gellan gum to prepare FBA/NE-ISG. Rheological study showed that FBA/NE-ISG possesses strong gelation capacity and its viscosity and elastic modulus increases by 2 Pa?s and 5 Pa respectively when mixed with artificial tear at the ratio of 40∶7. TEM images suggested no significant changes in particle morphology of the pre and post gelation. Good ocular compatibility of FBA/NE-ISG was testified by the irritation test based on histological examination. In vivo fluorescence imaging system was applied to investigate the characteristics of cornea retention, and the results indicated that the nanoemulsion-in situ gel (NE-ISG) prolonged the cornea retention time significantly since KNE-ISG (0.008 5 min-1) was much lower compared with flurbiprofen sodium eye drops (FB-Na, 0.03% w/v) of which the KEye drops was 0.105 2 min-1, indicated that the cornea retention time of NE-ISG was prolonged significantly. Pharmacokinetics of FBA/NE-ISG in rabbit aqueous humor was studied by cornea puncture, the MRT (12.3 h) and AUC0→12 h (126.8 ?g?min?mL-1) of FBA/NE-ISG was 2.7 and 2.9 times higher than that of the flrubiprofen sodium eye drops respectively, which meant that the ocular bioavailabilitywas improved greatly by the novel preparation. Therefore, FBA/NE-ISG can enhance the ocular bioavailability by prolonging drug corneal retention significantly. What’s more, encapsulated by emulsion droplets prodrug flurbiprofen (FBA) instead of flurbiprofen (FB) can reduce the ocular irritation.