This study evaluated the use of Pluronic F127 and Pluronic F68 as excipients for formulating in situ gelling systems for ocular drug delivery. Thermal transitions have been studied in aqueous solutions of Pluronic F127, Pluronic F68 as well as their binary mixtures using differential scanning calorimetry, rheological measurements, and dynamic light scattering. It was established that the formation of transparent gels at physiologically relevant temperatures is observed only in the case of 20 wt% of Pluronic F127. The addition of Pluronic F68 to Pluronic F127 solutions increases the gelation temperature of binary formulation to above physiological range of temperatures. The biocompatibility evaluation of these formulations using slug mucosa irritation assay and bovine corneal erosion studies revealed that these polymers and their combinations do not cause significant irritation. In vitro drug retention study on glass surfaces and freshly excised bovine cornea showed superior performance of 20 wt% Pluronic F127 compared to other formulations. In addition, in vivo studies in rabbits demonstrated better retention performance of 20 wt% Pluronic F127 compared to Pluronic F68. These results confirmed that 20 wt% Pluronic F127 offers an attractive ocular formulation that can form a transparent gel in situ under physiological conditions with minimal irritation.

Poly(acrylic acid) (PAA) and methylcellulose (MC) are able to form hydrogen-bonded interpolymer complexes (IPCs) in aqueous solutions. In this study, the complexation between PAA and MC is explored in dilute aqueous solutions under acidic conditions. The formation of stable nanoparticles is established, whose size and colloidal stability are greatly dependent on solution pH and polymers ratio in the mixture. Poly(acrylic acid) and methylcellulose are also used to prepare polymeric films by casting from aqueous solutions. It is established that uniform films can be prepared by casting from polymer mixture solutions at pH 3.4-4.5. At lower pHs (pH < 3.0) the films have inhomogeneous morphology resulting from strong interpolymer complexation and precipitation of polycomplexes, whereas at higher pHs (pH 8.3) the polymers form fully immiscible blends because of the lack of interpolymer hydrogen-bonding. The PAA/MC films cast at pH 4 are shown to be non-irritant to mucosal surfaces. These films provide a platform for ocular formulation of riboflavin, a drug used for corneal crosslinking in the treatment of keratoconus. An in vitro release of riboflavin as well as an in vivo retention of the films on corneal surfaces can be controlled by adjusting PAA/MC ratio in the formulations.

Polymeric films were prepared based on chitosan and its blends with poly(2-ethyl-2-oxazoline) by casting from aqueous solutions. These materials were characterised using a number of physicochemical techniques, including Fourier-transform infrared spectroscopy, thermal gravimetric analysis, differential scanning calorimetry, wide angle x-ray diffraction, tensile testing and scanning electron microscopy. All these studies indicate that there is a weak intermacromolecular hydrogen bonding between these polymers, which facilitates their complete miscibility in solid state. These films were formulated with sodium fluorescein as a model drug and were evaluated for their potential application in ocular drug delivery both in vitro and in vivo. It was established that the films are biocompatible and mucoadhesive; they are capable of providing a sustained drug release when administered topically on the cornea.

РефератЦель. Создание экспериментальной модели гнойной язвы роговицы у кроликов для её использования при ис-следовании глазных лекарственных форм. Методы. Формирование язвы роговицы сопровождается повышением температуры тела, которая была иссле-дована в трёх группах кроликов: (1) без нанесения травмы; (2) с нанесением травмы и формированием гнойной язвы без лечения; (3) с нанесением травмы и лечением ципрофлоксацином. Параллельно проводили забор гной-ного отделяемого для подсчёта колоний стафилококка. После выведения кроликов второй и третьей групп из эксперимента извлечённые роговицы были подвержены патоморфологическому анализу.Адрес для переписки: v.khutoryanskiy@reading.ac.uk