Formulation Strategies to Address Physiological and Anatomical Constraints for Improved Topical Ocular Drug Delivery

Delivery of therapeutic molecules to the eye has been a complicated task owing to its anatomical and physiological barriers. This dissertation delineates several formulation strategies to circumvent dynamic and static constraints hampering the ocular drug delivery. Advanced vesicular systems, bilosomes and transfersomes, were prepared to improve the ocular pharmacotherapy of natamycin (NT). NT bilosomes and transfersomes were further loaded into in situ gel systems which transformed immediately to hydrogel, in the simulated tear fluid, with good viscoelastic and mucoadhesive properties.In vitro corneal transport studies confirmed the superior permeability characteristics of NT from the optimized bilosome and transfersome in situ gel formulations, over control marketed (5 % w/v NT) suspension. In the ocular distribution studies, considerably higher mean dose normalized drug levels in the ocular tissues from bilosome and transfersome in situ gel formulations for 6h, compared to that from the control suspension, demonstrated the effectiveness of ion-sensitive in situ hydrogels of bilosomes and transfersomes as potential carrier systems for improved and prolonged topical ocular drug delivery. The magnitude of P-glycoprotein (P-gp) and multidrug resistance protein (MRP1) were investigated by comparative ocular distribution studies in the P-gp and MRP1 gene knock out (KO) and wild type (WT) rats. The blood ocular penetration of paclitaxel (PTX), a P-gp substrate and, methotrexate (MTX), an MRP 1 substrate, were significantly higher in the KO rats compared to WT rats. These results suggested that the penetration of anticancer substrate drugs across the BOB is restricted by efflux transporter proteins. Further, the concurrent intravenous administration of specific P-gp and MRP 1 inhibitors, along with PTX or MTX, in the WT rats resulted in improved blood ocular penetration of substrate anticancer drugs by effective inhibition of efflux protein activity in the BOB. The electroretinography (ERG) studies demonstrated that the inhibitor and substrate interactions did not induce any toxic effects on retina functions. However, at higher concentration of PTX and MTX shotoxic effects on the retina functions. Feasibility of coadministration of topical ocular inserts of P-gp inhibitors and intravenous anticancer substrate drug, PTX, was investigated in rats to examine the potential of this strategy to improve blood ocular penetration of PTX. Ocular films of P-gp inhibitors were fabricated by melt cast method and the transocular membrane permeability of the P-gp inhibitors, elacridar (EQ) and tariquidar (TQ), was investigated in the isolated rabbit cornea. Both EQ and TQ shotranscorneal permeability but no penetration through Sclera-choroidal retinal pigmented epithelium (RPE) tissue. The ocular distribution studies in rats shoimproved blood ocular penetration of PTX in the rats co-administered with EQ and TQ. These results demonstrated that the topically administered P-gp inhibitor effectively inhibits the P-gp activity and thereby improves ocular chemotherapy. ERG and Ultrastructure analyses of RPE confirmed that the PTX-EQ/TQ interactions were compatible with retina. TA protransfersome gel formulations were successfully prepared with at least two-fold higher drug load, compared to the marketed topical dosage form, which allows higher, localized, concentration gradients. Microscopic studies confirmed complete drug dissolution in the lipid phase and rapid formation of transfersomes on hydration. Significantly higher trans-eyelid TA permeation with the protransfersome gel formulation – demonstrated their potential in enhancing drug delivery to the ocular surface and deeper tissues via the eyelid. Experiments in dead rabbits confirmed that TA efficiently penetrated into the eyelid and formed a depot leading to increasing concentration-time profiles in all ocular tissues tested. The overall results suggest that trans-eyelid protransferosome gel formulations can provide a platform for the sustained delivery of therapeutic agents to both the surface of the eye as well as the anterior and posterior segment ocular tissues

SELF NANO EMULSIFYING DRUG DELIVERY SYSTEM OF RAMIPRIL: FORMULATION AND IN VITRO EVALUATION

Objective: The primary goal of the present work was to formulate and evaluate self-nano emulsifying drug delivery systems (SNEDDS) of ramipril in order to improve the solubility of this highly lipophilic antihypertensive drug.Methods: SNEDDS are generally liquid form preparations obtained by homogeneously mixing drug substance with oils, surfactants and co-surfactants using cyclomixer. Based on solubility studies Capmul PG8 NF, Gelucire 44/14 and Transcutol P were selected as oil, surfactant and co-surfactant respectively in order to prepare SNEDDS. Nine different SNEDDS formulations were prepared and subjected to various evaluation tests in order to obtain optimized SNEDDS formulation.Results: The SNEDDS formulations with 16.5-24.75 % of oil, 24.75-68.75 % of surfactant and 12.375-41.25 % of co-surfactant formed thermodynamically stable emulsion with droplet size ranging from 22.6-188.8 nm. Finally, out of 9 different SNEDDS formulations, SN9 formulation was optimized containing 16.5 % of oil, 68.75 % of surfactant and 13.75 % of co-surfactant as it formed a thermodynamically stable emulsion with least globule size (22.6 nm) and without any drug precipitation or phase separation.Conclusion: Finally, stable, optimized SNEDDS formulation of ramipril was successfully prepared that showed significant improvement in the rate of dissolution of ramipril.Keywords: Self nano emulsifying drug delivery system (SNEDDS), Ramipril, Emulsification time, Ternary phase diagram, Simulated Gastric Fluid (SGF)

Melt-cast films significantly enhance triamcinolone acetonide delivery to the deeper ocular tissues

© 2019 The Author(s). Background: Gene transfer to malignant sites using human adenoviruses (hAds) has been limited because of their immunogenic nature and host specificity. Murine cells often lack some of the receptors needed for hAds attachment, thus murine cells are generally non-permissive for human adenoviral infection and replication, which limits translational studies. Methods: We have developed a gene transfer method that uses a combination of lipid-encapsulated perfluorocarbon microbubbles and ultrasound to protect and deliver hAds to a target tissue, bypassing the requirement of specific receptors. Results: In an in vitro model, we showed that murine TRAMP-C2 and human DU145 prostate cancer cells display a comparable expression pattern of receptors involved in hAds adhesion and internalization. We also demonstrated that murine and human cells showed a dose-dependent increase in the percentage of cells transduced by hAd-GFP (green fluorescent protein) after 24 h and that GFP transgene was efficiently expressed at 48 and 72 h post-transduction. To assess if our image-guided delivery system could effectively protect the hAds from the immune system in vivo, we injected healthy immunocompetent mice (C57BL/6) or mice bearing a syngeneic prostate tumor (TRAMP-C2) with hAd-GFP/MB complexes. Notably, we did not observe activation of innate (TNF-α and IL-6 cytokines), or adaptive immune response (neutralizing antibodies, INF-γ+ CD8 + T cells). Conclusions: This study brings us a step closer to demonstrating the feasibility of murine cancer models to investigate the clinical translation of image guided site-specific adenoviral gene therapy mediated by ultrasound-targeted microbubble destruction

In situ gel of triamcinolone acetonide-loaded solid lipid nanoparticles for improved topical ocular delivery: Tear kinetics and ocular disposition studies

© 2019 The Authors Objective: The purpose of this systematic review is to summarize the best available evidence on interventions that could be implemented in the college environment to increase HPV vaccination uptake in college students who were not previously vaccinated. Methods: Pubmed, CINAHL, PsycINFO, Cochrane, and EBSCO were searched in December 2017 to identify all literature meeting the following criteria: human subjects, English language, HPV, HPV vaccination, and college. PRISMA recommendations were followed. We focused only on manuscripts that reported vaccine uptake, excluding studies that only reported vaccine intentions. We identified 2989 articles; 101 relevant after screening; nine eligible for final qualitative review. Results: Vaccine uptake rates ranged from 5% to 53%. Theory-based variables (e.g., perceived susceptibility and self-efficacy)were associated with vaccine uptake in most studies. A study exposing participants to a narrative video about HPV vaccination led by a combination of peers and medical experts produced the greatest difference in HPV vaccination initiation compared to a control group (21.8% vs 11.8%)of all the studies reviewed. Conclusions: Few interventions resulted in substantial HPV vaccine uptake. A combination of peer and provider encouragement may be the most effective method to increase vaccine uptake in this population

Gellan gum based sol-to-gel transforming system of natamycin transfersomes improves topical ocular delivery

© 2019 John Wiley & Sons Ltd Aim: Mesophotic coral ecosystems (MCEs) are unique communities that support a high proportion of depth-endemic species distinct from shallow-water coral reefs. However, there is currently little consensus on the boundaries between shallow and mesophotic coral reefs and between upper versus lower MCEs because studies of these communities are often site specific. Here, we examine the ecological evidence for community breaks, defined here as species loss, in fish and benthic taxa between shallow reefs and MCEs globally. Location: Global MCEs. Time period: 1973–2017. Major taxa studied: Macrophytes, Porifera, Scleractinia, Hydrozoa, Octocorallia, Antipatharia and teleost fishes. Methods: We used random-effects models and breakpoint analyses on presence/absence data to identify regions of higher than expected species loss along a depth gradient of 1–69 m, based on a meta-analysis of 26 studies spanning diverse photoautotrophic and heterotrophic taxa. We then investigated the extent to which points of high faunal turnover can be explained by environmental factors, including light, temperature and nutrient availability. Results: We found evidence for a community break, indicated by a significant loss of shallow-water taxa, at ~ 60 m across several taxonomically and functionally diverse benthic groups and geographical regions. The breakpoint in benthic composition is best explained by decreasing light, which is correlated with the optical depths between 10 and 1% of surface irradiance. A concurrent shift in the availability of nutrients, both dissolved and particulate organic matter, and a shift from photoautotroph to heterotroph-dominated assemblages also occurs at ~ 60 m depth. Main conclusions: We found evidence for global community breaks across multiple benthic taxa at ~ 60 m depth, indicative of distinct community transitions between shallow and mesophotic coral ecosystems. Changes in the underwater light environment and the availability of trophic resources along the depth gradient are the most parsimonious explanations for the observed patterns

Enhanced Dissolution Efficiency of Zaleplon Solid Dispersions via Modified β-Cyclodextrin Molecular Inclusion Complexes

Abstract The focus of the current study is to confirm the potential of chemically modified cyclodextrins (methyl-β-cyclodextrin (MβCD/Kleptose® Crysmeb), hydroxypropyl-β-cyclodextrin (HP-β-CD/Kleptose® HPB) and sulfobutylether-β-cyclodextrin (SBE-β-CD/Captisol®)) to improve the dissolution rate of zaleplon in oral delivery. Native and modified cyclodextrins were screened via phase solubility studies in order to select the most efficient cyclodextrin in formation of stable inclusion complexes. A L -type phase solubilization resulted from phase solubility diagrams of all cyclodextrin indicated a linear proportional relation between the solubility of zaleplon versus different CD concentrations. Complexation with crysmeb and HP-β-CD resulted in greater complexation constant values and higher percentage complexation efficiency values. Therefore these two cyclodextrins were selected for formulation development. Inclusion complexes of zaleplon:cyclodextrin solid dispersions were prepared using lyophilization and spray-drying techniques. DSC and XRD performance delineates the transformation of crystalline form of zaleplon to amorphous state. 1 HNMR studies confirm the presence of drug in the hydrophobic cavity of cyclodextrins and reveal the amorphous nature of the formulations. The stability studies of inclusion complexes for 60 days at 25°C/60 % RH and 40°C/75%RH resulted in low or no variations in the percentage of complexation efficiency suggesting good stability of molecular complexes. In conclusion, in vitro dissolution studies displayed an overall two-fold improvement in the dissolution rate compared to pure drug attributed to Crysmeb and HP-β-CD as suitable complexing agents in enhancing the solubility of zaleplon

Melt-Cast Films Significantly Enhance Triamcinolone Acetonide Delivery to the Deeper Ocular Tissues

Delivering an effective drug load to the posterior section of the ocular tissues, while using a non-invasive technique, has always been a challenge. In this regard, the goal of the present study was to develop sustained release triamcinolone acetonide (TA) loaded polymeric matrix films for ocular delivery. The TA-films were prepared in two different polymer matrices, with drug loadings of 10% and 20% w/w, and they were evaluated for ocular distribution in vivo in a conscious rabbit model. A 4% w/v TA suspension (TA-C) was used as a control for in vitro and in vivo studies. The TA-films, prepared with melt-cast technology, used polyethylene oxide (PEO) and Soluplus® as the polymer matrix. The films were evaluated with respect to assay, content uniformity, excipient interaction, and permeability across isolated rabbit sclera. The distribution of TA in the ocular tissues, post topical administration, was determined in New Zealand male albino rabbits as a function of dose, and was compared against TA-C. The assay of the 10% and 20% w/w film was in the range from 70–79% and 92–94% for the Soluplus® and PEO films, respectively, and content uniformity was in the range of 95–103% for both the films. The assay of the TA from Soluplus® films was less compared with the PEO films and showed an interaction with TA, as revealed by Differential Scanning Calorimetry (DSC). Hence, Soluplus® films were not selected for further studies. No interaction was observed between the drug and PEO polymer matrix. The enhancement of trans-scleral flux and permeability of TA was about 1.16 and 1.33-folds, respectively, from the 10% w/w PEO and 3.5 and 2.12-folds, respectively, from the 20% w/w PEO films, as compared with TA-C formulations. The in vivo studies demonstrate that significantly higher TA levels were observed in the anterior and posterior segments of the eye at the end of 6h with the PEO films. Therefore, the PEO based polymeric films were able to deliver TA into the back of the eye efficiently and for prolonged periods

In Situ Gel of Triamcinolone Acetonide-Loaded Solid Lipid Nanoparticles for Improved Topical Ocular Delivery: Tear Kinetics and Ocular Disposition Studies

Triamcinolone acetonide (TA), an intermediate acting corticosteroid, is used in the treatment of posterior ocular diseases, such as inflammation, posterior uveitis, and diabetic macular edema. The objective of this investigation was to prepare TA-loaded solid lipid nanoparticles (TA-SLNs) and in situ gel (TA-SLN-IG) formulations for delivery into the deeper ocular tissues through the topical route. TA-SLNs were prepared by hot homogenization and ultrasonication method using glyceryl monostearate and Compritol® 888ATO as solid lipids and Tween®80 and Pluronic® F-68 as surfactants. TA-SLNs were optimized and converted to TA-SLN-IG by the inclusion of gellan gum and evaluated for their rheological properties. In vitro transcorneal permeability and in vivo ocular distribution of the TA-SLNs and TA-SLN-IG were studied using isolated rabbit corneas and New Zealand albino rabbits, respectively, and compared with TA suspension, used as control (TA-C). Particle size, PDI, zeta potential, assay, and entrapment efficiency of TA-SLNs were in the range of 200–350 nm, 0.3–0.45, −52.31 to −64.35 mV, 70–98%, and 97–99%, respectively. TA-SLN-IG with 0.3% gellan gum exhibited better rheological properties. The transcorneal permeability of TA-SLN and TA-SLN-IG was 10.2 and 9.3-folds higher compared to TA-C. TA-SLN-IG showed maximum tear concentration at 2 h, indicating an improved pre-corneal residence time, as well as higher concentrations in aqueous humor, vitreous humor and cornea at 6 h, suggesting sustained delivery of the drug into the anterior and posterior segment ocular tissues, when compared to TA-SLN and TA-C. The results, therefore, demonstrate that the lipid based nanoparticulate system combined with the in situ gelling agents can be a promising drug delivery platform for the deeper ocular tissues