Esthetized using an intraperitoneal injection of a mixture of 80 mg/kg ketamine and 10 mg/kg xylazine. Using a 10 ml Hamilton glass syringe (Hamilton company, NV) fitted with a 34 gauge needle (1/2 inch long; with a 45o taper), 5 ml phosphate buffer saline (PBS; pH 7.4) containing 100 mg/ml NaF was injected into the suprachoroidal space, posterior subconjunctival region, or vitreous humor of the right eye of the rat.Histology of Rat Eye after Suprachoroidal InjectionTo confirm the accuracy of suprachoroidal injection in vivo in rat eyes, histological examination of rat eye after suprachoroidal injection of India ink dispersion was performed. Rats were anaesthetized and 5 ml of 5 India ink dispersion was injected in the suprachoroidal space using a 10 ml Hamilton glass syringe fitted with a 34 gauge needle (1/2 inch long; with a 45o taper). Rats were immediately euthanized and eyes enucleated. Eyes were further fixed in 4 formalin solution for 2 days. Paraffin MedChemExpress Entospletinib sections (5 um thick) were obtained and stained with haematoxylin and eosin. Sections were observed under a light microscope (Olympus BX41 laboratory microscope) fitted with a camera (Diagnostics instruments Inc.).Ocular FluorophotometryThe disposition of NaF was studied using Fluorotron MasterTM, an ocular fluorophotometer (OcuMetrics Inc., Mountain View, CA) fitted with a small animal adapter. The Fluorotron scans report NaF concentrations in ocular tissues at 0.25 mm intervals along an optical axis used by the instrument. Prior to acquiring Fluorotron scans, a single drop 1313429 of 1 tropicamide (Mydriacyl, Alcon laboratories, Inc., TX) solution was instilled in the eyes. Baseline fluorescence was measured prior to NaF injections. After NaF injections, Fluorotron scans were acquired up to six hours, with repeated application of tropicamide drops every 2 hours. The maximum pupil diameter size (pupillary dilation) with 1 tropicamide solution eye drops is attained within , 40 minutes [24] and persists up to , 70 minutes, requiring repeatedSuprachoroidal Drug DeliveryFigure 1. Suprachoroidal injection of India ink between sclera and choroid-retina in SD rats. Eyes were injected with 5 ml of 5 India ink dispersion in suprachoroidal space. The eyes were fixed in 4 formalin and embedded in paraffin blocks. H E stained sections were examined. (A) A 46 magnification image showing a cross section of a blank eye; (B) Eye administered with suprachoroidal injection; (C) 106 magnification of a blank eye; and (D) A 106 magnification of the site of suprachoroidal injection showing the presence of India ink in the suprachoroidal space. doi:10.1371/journal.pone.0048188.ginstillation. Saline solution eye drops were applied to the eyes periodically, to prevent dehydration of the corneas. The raw data from the fluorophotometer was transferred to a spreadsheet (Excel; MedChemExpress GSK0660 Microsoft Corporation, WA) and plotted.ANOVA followed by Tukey’s post hoc analysis (SPSS, ver.11.5; SPSS, Chicago, IL). The results were considered statistically significant at p,0.05.Results Pharmacokinetic and Statistical AnalysisNon-compartmental pharmacokinetic analysis for the three routes of injection was performed using WinNonlin software (Version 1.5, Scientific Consulting, Inc.). AUC0?60 min is the area under the curve obtained by plotting the concentration-time data, where`t’ is the last time point at which NaF levels were measured. The “t” value was 360 minutes for the three routes of administration. The 0-time point conce.Esthetized using an intraperitoneal injection of a mixture of 80 mg/kg ketamine and 10 mg/kg xylazine. Using a 10 ml Hamilton glass syringe (Hamilton company, NV) fitted with a 34 gauge needle (1/2 inch long; with a 45o taper), 5 ml phosphate buffer saline (PBS; pH 7.4) containing 100 mg/ml NaF was injected into the suprachoroidal space, posterior subconjunctival region, or vitreous humor of the right eye of the rat.Histology of Rat Eye after Suprachoroidal InjectionTo confirm the accuracy of suprachoroidal injection in vivo in rat eyes, histological examination of rat eye after suprachoroidal injection of India ink dispersion was performed. Rats were anaesthetized and 5 ml of 5 India ink dispersion was injected in the suprachoroidal space using a 10 ml Hamilton glass syringe fitted with a 34 gauge needle (1/2 inch long; with a 45o taper). Rats were immediately euthanized and eyes enucleated. Eyes were further fixed in 4 formalin solution for 2 days. Paraffin sections (5 um thick) were obtained and stained with haematoxylin and eosin. Sections were observed under a light microscope (Olympus BX41 laboratory microscope) fitted with a camera (Diagnostics instruments Inc.).Ocular FluorophotometryThe disposition of NaF was studied using Fluorotron MasterTM, an ocular fluorophotometer (OcuMetrics Inc., Mountain View, CA) fitted with a small animal adapter. The Fluorotron scans report NaF concentrations in ocular tissues at 0.25 mm intervals along an optical axis used by the instrument. Prior to acquiring Fluorotron scans, a single drop 1313429 of 1 tropicamide (Mydriacyl, Alcon laboratories, Inc., TX) solution was instilled in the eyes. Baseline fluorescence was measured prior to NaF injections. After NaF injections, Fluorotron scans were acquired up to six hours, with repeated application of tropicamide drops every 2 hours. The maximum pupil diameter size (pupillary dilation) with 1 tropicamide solution eye drops is attained within , 40 minutes [24] and persists up to , 70 minutes, requiring repeatedSuprachoroidal Drug DeliveryFigure 1. Suprachoroidal injection of India ink between sclera and choroid-retina in SD rats. Eyes were injected with 5 ml of 5 India ink dispersion in suprachoroidal space. The eyes were fixed in 4 formalin and embedded in paraffin blocks. H E stained sections were examined. (A) A 46 magnification image showing a cross section of a blank eye; (B) Eye administered with suprachoroidal injection; (C) 106 magnification of a blank eye; and (D) A 106 magnification of the site of suprachoroidal injection showing the presence of India ink in the suprachoroidal space. doi:10.1371/journal.pone.0048188.ginstillation. Saline solution eye drops were applied to the eyes periodically, to prevent dehydration of the corneas. The raw data from the fluorophotometer was transferred to a spreadsheet (Excel; Microsoft Corporation, WA) and plotted.ANOVA followed by Tukey’s post hoc analysis (SPSS, ver.11.5; SPSS, Chicago, IL). The results were considered statistically significant at p,0.05.Results Pharmacokinetic and Statistical AnalysisNon-compartmental pharmacokinetic analysis for the three routes of injection was performed using WinNonlin software (Version 1.5, Scientific Consulting, Inc.). AUC0?60 min is the area under the curve obtained by plotting the concentration-time data, where`t’ is the last time point at which NaF levels were measured. The “t” value was 360 minutes for the three routes of administration. The 0-time point conce.