Nanoparticle-based topical ophthalmic formulation for sustained release of stereoisomeric dipeptide prodrugs of ganciclovir.

Poly(d,l-lactic-co-glycolic acid) (PLGA) nanoparticles (NP) of Val-Val dipeptide monoester prodrugs of ganciclovir (GCV) including L-Val-L-Val-GCV (LLGCV), L-Val-D-Val-GCV (LDGCV) and D-Val-L-Val-GCV (DLGCV) were formulated and dispersed in thermosensitive PLGA-PEG-PLGA polymer gel for the treatment of herpes simplex virus type 1 (HSV-1)-induced viral corneal keratitis. Nanoparticles containing prodrugs of GCV were prepared by a double-emulsion solvent evaporation technique using various PLGA polymers with different drug/polymer ratios. Nanoparticles were characterized with respect to particle size, entrapment efficiency, polydispersity, drug loading, surface morphology, zeta potential and crystallinity. Prodrugs-loaded NP were incorporated into in situ gelling system. These formulations were examined for in vitro release and cytotoxicity. The results of optimized entrapment efficiencies of LLGCV-, LDGCV- and DLGCV-loaded NP are of 38.7 +/- 2.0%, 41.8 +/- 1.9%, and 45.3 +/- 2.2%; drug loadings 3.87 +/- 0.20%, 2.79 +/- 0.13% and 3.02 +/- 0.15%; yield 85.2 +/- 3.0%, 86.9 +/- 4.6% and 76.9 +/- 2.1%; particle sizes 116.6 +/- 4.5, 143.0 +/- 3.8 and 134.1 +/- 5.2nm; and zeta potential -15.0 +/- 4.96, -13.8 +/- 5.26 and -13.9 +/- 5.14mV, respectively. Cytotoxicity studies suggested that all the formulations are non-toxic. In vitro release of prodrugs from NP showed a biphasic release pattern with an initial burst phase followed by a sustained phase. Such burst effect was completely eliminated when NP were suspended in thermosensitive gels with near zero-order release kinetics. Prodrugs-loaded PLGA NP dispersed in thermosensitive gels can thus serve as a promising drug delivery system for the treatment of anterior eye diseases.