On the biocompatibility and teat retention of in situ gelling intramammary formulations: Cattle mastitis prevention and treatment

Treatment and prevention of cattle mastitis remains a formidable challenge due to the anatomical and physiological constraints of the cow udder. In this study, we investigated polymeric excipients and solvents that can form, (when combined) novel, non-toxic and biocompatible in situ gelling formulations in the mammary gland of bovine cattle. We also report on a new approach to screen intramammary formulations using fresh excised cow teats. Fourteen hydrophilic polymers and six solvents were evaluated for in vitro cytotoxicity and biocompatibility towards cultured bovine mammary epithelial cells (MAC-T), microscopic and macroscopic examination upon contact with excised cow teats. No significant cytotoxicity (p > 0.05) was observed with polyethylene oxides, hydroxypropyl methylcellulose, carboxymethyl cellulose, sodium alginate and xanthan gum. Polycarbophil and carbopol polymers showed significantly higher cytotoxicity (p < 0.05). Concentration-dependent cytotoxicity was observed for glycerin, propylene glycol, polyethylene glycol 400, ethanol, N-methyl-2-pyrrolidone and 2-pyrrolidone, with the 2-pyrrolidone solvents showing higher cytotoxic effects (p < 0.05). In situ gelling formulations comprising hydroxypropyl methylcellulose or carboxymethyl cellulose and solvents in specific ratios were biocompatible at higher concentrations with MAC-T cells compared to alginates. All investigated formulations could undergo in situ sol-to-gel phase transformation, forming non-toxic gels with good biocompatibility in excised cow teats hence, showing potential for use as intramammary carriers for sustained drug delivery

Water Solubilization Using Nonionic Surfactants from Renewable Sources in Microemulsion Systems

In this study the effect of temperature, NaCl and oils (hydrocarbons: C8–C16) on the formation and solubilization capacity of the systems of oil/monoacylglycerols (MAG):ethoxylated fatty alcohols (CEO20)/propylene glycol (PG)/water was investigated. The effects of the surfactant mixture on the phase behavior and the concentration of water or oil in the systems were studied at three temperatures (50, 55, 60 °C) and with varied NaCl solutions (0.5; 2; 11%). Electrical conductivity measurement, FTIR spectroscopy and the DSC method were applied to determine the structure and type of the microemulsions formed. The dimension of the microemulsion droplets was characterized by dynamic light scattering. It has been stated that the concentration of CEO20 has a strong influence on the shape and extent of the microemulsion areas. Addition of a nonionic surfactant to the mixture with MAG promotes an increase in the area of microemulsion formation in the phase diagrams, and these areas of isotropic region did not change considerably depending on the temperature, NaCl solution and oil type. It was found that, depending on the concentration of the surfactant mixture, it was possible to obtain U-type microemulsions with dispersed particles size distribution ranging from 25 to 50 nm and consisting of about 30–32% of the water phase in the systems. The conditions under which the microemulsion region was found (electrolyte and temperature—insensitive, comparatively low oil and surfactant concentration) could be highly useful in detergency

Phytosome-hyaluronic acid systems for ocular delivery of L-carnosine

Hamdy Abdelkader,1,2 Michael R Longman,1 Raid G Alany,1,3 Barbara Pierscionek4 1Drug Discovery, Delivery and Patient Care (DDDPC) Theme, School of Life Sciences, Pharmacy and Chemistry, Kingston University London, Kingston Upon Thames, London, UK; 2Department of Pharmaceutics, Faculty of Pharmacy, Minia University, Mina, Egypt; 3School of Pharmacy, The University of Auckland, Auckland, New Zealand; 4Vision Cognition and Neuroscience Theme, Faculty of Science, Engineering and Computing, Kingston University London, Kingston Upon Thames, London, UK Abstract: This study reports on L-carnosine phytosomes as an alternative for the prodrug N-acetyl-L-carnosine as a novel delivery system to the lens. L-carnosine was loaded into lipid-based phytosomes and hyaluronic acid (HA)-dispersed phytosomes. L-carnosine-phospholipid complexes (PC) of different molar ratios, 1:1 and 1:2, were prepared by the solvent evaporation method. These complexes were characterized with thermal and spectral analyses. PC were dispersed in either phosphate buffered saline pH 7.4 or HA (0.1% w/v) in phosphate buffered saline to form phytosomes PC1:1, PC1:2, and PC1:2 HA, respectively. These phytosomal formulations were studied for size, zeta potential, morphology, contact angle, spreading coefficient, viscosity, ex vivo transcorneal permeation, and cytotoxicity using primary human corneal cells. L-carnosine-phospholipid formed a complex at a 1:2 molar ratio and phytosomes were in the size range of 380&ndash;450 nm, polydispersity index of 0.12&ndash;0.2. The viscosity of PC1:2 HA increased by 2.4 to 5-fold compared with HA solution and PC 1:2, respectively; significantly lower surface tension, contact angle, and greater spreading ability for phytosomes were also recorded. Ex&nbsp;vivo transcorneal permeation parameters showed significantly controlled corneal permeation of L-carnosine with the novel carrier systems without any significant impact on primary human corneal cell viability. Ex vivo porcine lenses incubated in high sugar media without and with L-carnosine showed concentration-dependent marked inhibition of lens brunescence indicative of the potential for delaying changes that underlie cataractogenesis that may be linked to diabetic processes. Keywords: lipoid S 75, phytosomes, L-carnosine, cataract, hyaluronate sodium, ocular deliver

Characterizing colloidal structures of pseudoternary phase diagrams formed by oil/water/amphiphile systems

Two pseudoternary phase diagrams were constructed using ethyl oleate, water and a surfactant blend containing poly (oxyethylene 20) sorbitan monooleate and sorbitan monolaurate with or without the cosurfactant 1-butanol. Two colloidal regions were identified in the cosurfactant;free phase diagram; a microemulsion (ME) and a region containing lamellar liquid crystals (LC). The addition of 1-butanol increased the area in which systems formed microemulsions and eliminated the formation of any liquid crystalline phases. Samples that form the colloidal regions of both systems were investigated by freeze-fracture transmission electron microscopy and by viscosity and conductivity measurements. The three techniques were compared and evaluated as characterisation tools for such colloidal systems and also to identify transitions between the colloidal systems formed A droplet ME was present at a low water volume fraction (phi (w)) in both systems (phi (w) < 0.15) as revealed by electron microscopy. At higher (w) values, LC structures were Observed in micrographs of samples taken from the cosurfactant-free system while the structure of samples from the cosurfactant-containing system was that of a bicontinuous ME. The viscosity of both systems increased with increasing phi (w) to 0.15 and flow was Newtonian. However; formation of LC in the cosurfactant-free system resulted in a dramatic increase in viscosity that was dependent on phi (w) and a change to pseudoplastic flow. In contrast, the viscosity of the bicontinuous ME was independent of phi (w). Three different methods were used to estimate the percolation threshold from the conductivity data far the cosurfactant-containing system. The use of nonlinear curve fitting was found to be most useful yielding a value close to 0.15 for the phi (w)

Phytosome-hyaluronic acid systems for ocular delivery of L-carnosine

This study reports on L-carnosine phytosomes as an alternative for the prodrug N-acetyl-L-carnosine as a novel delivery system to the lens. L-carnosine was loaded into lipid-based phytosomes and hyaluronic acid (HA)-dispersed phytosomes. L-carnosine-phospholipid complexes (PC) of different molar ratios, 1:1 and 1:2, were prepared by the solvent evaporation method. These complexes were characterized with thermal and spectral analyses. PC were dispersed in either phosphate buffered saline pH 7.4 or HA (0.1% w/v) in phosphate buffered saline to form phytosomes PC1:1, PC1:2, and PC1:2 HA, respectively. These phytosomal formulations were studied for size, zeta potential, morphology, contact angle, spreading coefficient, viscosity, ex vivo transcorneal permeation, and cytotoxicity using primary human corneal cells. L-carnosine-phospholipid formed a complex at a 1:2 molar ratio and phytosomes were in the size range of 380-450 nm, polydispersity index of 0.12-0.2. The viscosity of PC1:2 HA increased by 2.4 to 5-fold compared with HA solution and PC 1:2, respectively; significantly lower surface tension, contact angle, and greater spreading ability for phytosomes were also recorded. Ex vivo transcorneal permeation parameters showed significantly controlled corneal permeation of L-carnosine with the novel carrier systems without any significant impact on primary human corneal cell viability. Ex vivo porcine lenses incubated in high sugar media without and with L-carnosine showed concentration-dependent marked inhibition of lens brunescence indicative of the potential for delaying changes that underlie cataractogenesis that may be linked to diabetic processes

On the anticataractogenic effects of L-carnosine: is it best described as an antioxidant, metal-chelating agent or glycation inhibitor?

Purpose. L-Carnosine is a naturally occurring dipeptide which recently gained popularity as an anticataractogenic agent due to its purported antioxidant activities. There is a paucity of research and conclusive evidence to support such claims. This work offers compelling data that help clarify the mechanism(s) behind the anticataract properties of L-carnosine. Methods. Direct in vitro antioxidant free radical scavenging properties were assayed using three different antioxidant (TEAC, CUPRAC, and DPPH) assays. Indirect in vitro and ex vivo antioxidant assays were studied by measuring glutathione bleaching capacity and total sulfhydryl (SH) capacity of bovine lens homogenates as well as hydrogen-peroxide-stress assay using human lens epithelial cells. Whole porcine lenses were incubated in high galactose media to study the anticataract effects of L-carnosine. MTT cytotoxicity assays were conducted on human lens epithelial cells. Results. The results showed that L-carnosine is a highly potent antiglycating agent but with weak metal chelating and antioxidant properties. There were no significant decreases in lens epithelial cell viability compared to negative controls. Whole porcine lenses incubated in high galactose media and treated with 20 mM L-carnosine showed a dramatic inhibition of advanced glycation end product formation as evidenced by NBT and boronate affinity chromatography assays. Conclusion. L-Carnosine offers prospects for investigating new methods of treatment for diabetic cataract and any diseases that are caused by glycation

W/O microemulsions for ocular delivery: Evaluation of ocular irritation and precorneal retention

Water-in-oil microemulsions (w/o ME) capable of undergoing a phase-transition to lamellar liquid crystals (LC) or bicontinuous ME upon aqueous dilution were formulated using Crodarnol EO, Crill 1 and Crillet 4, an alkanol or alkanediol as cosurfactant and water. The hypothesis that phase-transition of ME to LC may be induced by tears and serve to prolong precomeal retention was tested. The ocular irritation potential of components and formulations was assessed using a modified hen's egg chorioallantoic membrane test (HET-CAM) and the preocular retention of selected formulations was investigated in rabbit eye using gamma scintigraphy. Results showed that Crill 1, Crillet 4 and Crodamol EO were non-irritant. However, all other cosurfactants investigated were irritant and their irritation was dependent on their carbon chain length. A w/o ME formulated without cosurfactant showed a protective effect when a strong irritant (0.1 M NaOH) was used as the aqueous phase. Precorneal clearance studies revealed that the retention of colloidal and coarse dispersed systems was significantly greater than an aqueous solution with no significant difference between ME systems (containing 5% and 10% water) as well as o/w emulsion containing 85% water. Conversely, a LC system formulated without cosurfactant displayed a significantly greater retention compared to other formulations. (c) 2005 Elsevier B.V. All rights reserved

The suprachoroidal pathway: a new drug delivery route to the back of the eye

The development of safe and convenient drug delivery strategies for treatment of posterior segment eye diseases is challenging. Although intravitreal injection has wide acceptance amongst clinicians, its use is associated with serious side-effects. Recently, the suprachoroidal space (SCS) has attracted the attention of ophthalmologists and pharmaceutical formulators as a potential site for drug administration and delivery to the posterior segment of the eye. This review highlights the major constraints of drug delivery to the posterior eye segment, key anatomical and physiological features of the SCS and drug delivery applications of this route with emphasis on microneedles along with future perspectives

Study of isopropyl myristate microemulsion systems containing cyclodextrins to improve the solubility of 2 model hydrophobic drugs

The objectives of this project were to evaluate the effect of alkanols and cyclodextrins on the phase behavior of an isopropyl myristate microemulsion system and to examine the solubility of model drugs. Triangular phase diagrams were developed for the microemulsion systems using the water titration method, and the solubility values of progesterone and indomethacin were determined using a conventional shake-flask method. The water assimilation capacities were determined to evaluate the effective microemulsion formation in different systems. The alkanols showed higher microemulsion formation rates at higher concentrations. A correlation between the carbon numbers of the alkanol and water assimilation capacity in the microemulsions studied was observed; isobutanol and isopentanol produced the best results. The addition of cyclodextrins showed no effect or had a negative effect on the microemulsion formation based on the type of cyclodextrin used. Isopropyl myristate-based microemulsion systems alone could increase the solubility values of progesterone and indomethacin up to 3300-fold and 500-fold, respectively, compared to those in water. However, the addition of cyclodextrins to the microemulsion systems did not show a synergistic effect in increasing the solubility values of the model drugs. In conclusion, microemulsion systems improve the solubility of progesterone and indomethacin. But the two types of cyclodextrins studied affected isopropyl myristatebased microemulsion systems negatively and did not improve the solubilization of 2 model drugs