title: Nanosized dendritic polyguanidilyated translocators for enhanced solubility, permeability, and delivery of gatifloxacin.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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).
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Pharmaceutical Sciences, University of Colorado Denver, Aurora, Colorado 80045, USA.
authors.forename: Chandrasekar
authors.initials: C
authors.lastname: Durairaj
authors.forename: Rajendra S
authors.initials: RS
authors.lastname: Kadam
authors.forename: John W
authors.initials: JW
authors.lastname: Chandler
authors.forename: Stephen L
authors.initials: SL
authors.lastname: Hutcherson
authors.forename: Uday B
authors.initials: UB
authors.lastname: Kompella
mesh_terms: D000287:Administration, Topical; D000818:Animals; D000890:Anti-Infective Agents / Q000008:administration & dosage* / Q000493:pharmacokinetics; D019540:Area Under Curve; D002151:Calorimetry; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D050091:Dendrimers / Q000737:chemistry*; D016503:Drug Delivery Systems; D004347:Drug Interactions; D019573:Epithelium, Corneal / Q000378:metabolism; D016650:Fluorescein-5-isothiocyanate; D024841:Fluoroquinolones / Q000008:administration & dosage* / Q000493:pharmacokinetics; D000077734:Gatifloxacin; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects; D008826:Microbial Sensitivity Tests; D018613:Microscopy, Confocal; D053758:Nanoparticles; D009883:Ophthalmic Solutions / Q000008:administration & dosage* / Q000493:pharmacokinetics; D010539:Permeability; D011068:Poly G / Q000737:chemistry*; D011817:Rabbits; D012995:Solubility; D017550:Spectroscopy, Fourier Transform Infrared; D053719:Tandem Mass Spectrometry; D014018:Tissue Distribution
chemical_list: D000890:Anti-Infective Agents; D050091:Dendrimers; D024841:Fluoroquinolones; D009883:Ophthalmic Solutions; D011068:Poly G; D016650:Fluorescein-5-isothiocyanate; D000077734:Gatifloxacin