Nanosized dendritic polyguanidilyated translocators for enhanced solubility, permeability, and delivery of gatifloxacin

Dendrimeric polyguanidilyated translocators (DPTs) are nanosized novel dendrimers that efficiently translocate molecules across biological barriers. The purpose of this study was to develop a DPT that could serve as an ophthalmic delivery vehicle for gatifloxacin and to evaluate its in vitro and in vivo delivery after topical application. The gatifloxacin (GFX) solubility-enhancing property of a six-guanidine group-containing dendrimer (g6 DPT) was investigated as a function of pH and dendrimer concentration. Mechanisms of drug interaction with the dendrimer were investigated by using isothermal titration calorimetry (ITC), Fourier-transformed infrared spectroscopy (FTIR), and nuclear magnetic resonance spectroscopy (NMR). Permeability of the dendrimer was assessed in human corneal epithelial cells (HCECs) and across isolated bovine sclera-choroid-RPE (SCRPE). In vitro efficacy of the dendrimer formulation was evaluated with a time-to-kill assay for methicillin resistant Staphylococcus aureus (MRSA). In vivo delivery of GFX in a dendrimer eye drop formulation was studied in New Zealand White rabbits after a single dose or multiple doses over 3 weeks. Drug levels in various ocular tissues were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). An optimized DPT-GFX formulation (final pH 5.9, no preservative) increased GFX solubility by fourfold. The dendrimer formed isotonically stable, nanosized (346-nm) complexes with GFX via ionic bond, hydrogen bond, and hydrophobic interactions. The dendrimer gained rapid entry into the HCECs (within 5 minutes) and increased the transport of GFX by 40% across the SCRPE in 6 hours. DPT-GFX exhibited a three times faster killing rate for MRSA when compared with GFX alone. In vivo administration of DPT-GFX (1.2% wt/vol) resulted in ∼13-fold, and ∼2-fold higher areas under the curve (AUCs) for tissue concentrations in conjunctiva and cornea, respectively, when compared with GFX (0.3%) after a single dose. Further, a single dose of DPT-GFX sustained aqueous humor and vitreous humor drug levels during the 24-hour study, with a t(1/2) of 9 and 32 hours, respectively. After multiple doses, similar advantages were seen with DPT-GFX. The DPT forms stable complexes with GFX and enhances its solubility, permeability, anti-MRSA activity, and in vivo delivery, potentially allowing a once-daily dose regimen.