Polymeric Eye Films Based on Polyvinyl Alcohol and Arabinogalactan with Levofloxacin

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2013, Vol. 86, No. 4, pp. 605 609. Pleiades Publishing, Ltd., 2013. Original Russian Text R.Kh. Mudarisova, L.A. Badykova, G.A. Azamatova, R.M. Islamova, M.T. Aznabaev, 2013, published in Zhurnal Prikladnoi Khimii, 2013, Vol. 86, No. 4, pp.650 654. BRIEF COMMUNICATIONS Polymeric Eye Films Based on Polyvinyl Alcohol and Arabinogalactan with Levofloxacin R. Kh. Mudarisova a, L. A. Badykova a, G. A. Azamatova b, R. M. Islamova c, and M. T. Aznabaev b ainstitute of Organic Chemistry, Ural Scientific Center, Russian Academy of Sciences, Ufa, Bashkortostan, Russia bbashkir State Medical University, Ufa, Bashkortostan, Russia cbashkir State Agricultural University, Ufa, Bashkortostan, Russia e-mail: badykova@mail.ru Received January 11, 2012 Abstract Physicochemical methods were used to study the interaction of arabinogalactan from Siberian larch with the antibacterial preparation levofloxacin. Polymeric eye films with controllable output of the medicinal preparation were produced on the basis of an arabinogalactan polyvinyl alcohol formulation. A high pharmaceutical activity of the new eye films was demonstrated. DOI: 10.1134/S1070427213040289 Development and study of systems for directed transport and controlled release of medicinal substances from medicinal films is a topical area of modern pharmacochemistry. Medicated films based on polymer mixtures are rather promising in this regard. In particular, they can be regarded as polymeric matrices for fixation of medicinal preparations and prolongation of their action in development of new medicated eye films (MEFs). In ophthalmology, postoperative infection still remains a problem. Instillation of medicinal preparations is one of the most widely used methods for antibiotic prophylaxis of these complications. However, an important disadvantage of eye drops is the fast absorption of a preparation by the mucous eye membranes and its substantial loss with tears and in winking [1]. It has been confirmed that instillations fail to create in the aqueous eye chamber the antibiotic concentration necessary for suppressing the growth of microorganisms and, therefore, cannot provide the effective prophylaxis [2, 3]. Therefore, development and application of medicated eye films is a rational solution of the problem of prolongation and dosed delivery of medicinal preparations into eye tissues. The system of polyvinyl alcohol (PVA) and arabinogalactan (AG) was studied as a polymeric support in development of medicinal eye films. At present, PVA and a natural polysaccharide arabinogalactan are widely used in medicine. These supports are nontoxic and biocompatible and make substantially more prolonged the effect of medicinal preparations [4, 5]. Also, arabinogalactan exhibits a versatile biological activity. All the arabinogalactans studied exert a controlling influence on the immune system and have membranotropic properties, owing to which they can be used to enhance the absorption of other medicinal preparations characterized by low bioavailability. AG also has an antimicrobial effect on some bacteria, stimulates the reticuloendothelial system, and enhances the phagocytic activity of macrophages [6]. However, AG itself has no film-forming properties, and, therefore, it was of indubitable interest to introduce AG into a filmforming polymer widely used in medicine, polyvinyl alcohol. A system of this kind can enhance the therapeutic effect of an immobilized medicinal preparation and is biodegradable under its application conditions because the polymers are water soluble. 605

606 MUDARISOVA et al. The goal of this study was to develop and study medicated eye films (MEFs) based on arabinogalactan and PVA and characterized y controllable release of an antibacterial preparation levofloxacin (LVF). EXPERIMENTAL As object of study were chosen PVA of 16/1 brand (M = 72 000), AG sample produced from Siberian larch wood and pharmaceutical preparation, levofloxacin antibiotic [7], without additional purification. The average size R of particles and their number concentration N in 1 cm 3 in aqueous solutions were determined using the turbidity spectrum method [8, 9]. The weight-average sizes of supramolecular particles were determined in -.04% PVA and AG solutions at a solvent : precipitant ratio of 1 : 0.1. Acetone was used as the precipitating agent. The measurements were made at wavelengths λ = 350 600 nm at 25 C with a Specord M-40 instrument. The composition and the stability constant of the complex were determined by the molecular-series and molar-ratio methods [10]. IR spectra of the complexes were recorded with a Shimadzu spectrophotometer at 700 3600 cm 1 in Vaseline oil. The complexes were obtained as follows: 0.5 g of AG was dissolved in 20 ml of water and the LVF was added in an amount of 0.55 g under vigorous agitation. The reaction was performed at room temperature in the course of 3 h. After that the product was isolated, thrice washed with ethanol and then with diethyl ether, and dried in a vacuum. Film materials based on PVA and (PVA + AG) were formed by application of solutions to a glass substrate, followed by evaporation of the solvent in a vacuum over phosphorus pentaoxide. Further, the films were dried in a vacuum at a temperature of 25 C to a residual moisture content of 5 7%. Formulations for film fabrication were prepared by adding a prescribed amount of AG and levofloxacin to an aqueous solution of polyvinyl alcohol. The mixture was agitated at a temperature of 25 C or 1 h. The thickness of the films was maintained constant (0.5 mm). The optimal contents of the components per 1 cm2 of the film were 0.04 g of PVA, 0.25 mg of LVF, and 0.008 g of AG. The kinetics of LVF release from the films was studied spectrophotometrically on the basis of their optical density at λ = 290 nm. The LVF concentration in solutions was calculated using a calibration plot. The antibiotic concentration was determined as follows: MEFs were placed in 100 ml of the physiological solution at a temperature of 37 C and its samples were taken at certain intervals of time. The optical density of a solution sample was measured with the spectrophotometer and the LVF concentration in the solution was calculated from calibration data. The measurements were made until the optical density of the solution ceased to vary. Pharmacological studies of the eye films were performed on rabbits of Chinchilla breed with mass of 2.5 3.0 kg. Experimental and control groups of the animals were kept under the standard, strictly identical conditions. The animals were divided into three groups with four rabbits each. A 0.5% aqueous solution of levofloxacin was applied by dropping to the posterior fornix of conjunctiva by the ordinary procedure. MEFs based on PVA with LVF and on (PVA + AG) with LVF were placed in the conjunctival cavity of animals from the second and third groups, respectively. The biological activity of the MEFs was determined by the disk-diffusion method on a Muller Hinton agar. The aqueous humor from the anterior chamber was sampled in 1, 4, 8, and 24 h. Preliminarily, a calibration plot describing the dependence of the growth retardation zone of Staphyllococcus aureus on the prescribed LVF concentration was obtained [11]. The content of LVF in the aqueous humor from the anterior chamber of rabbit eyes was determined by comparison of the growth retardation zones. It is known that the composition of the forming solution directly affects some properties of the composites obtained in fabrication of films from polymeric mixtures. Films formed from solutions with various polymer ratios differ in, e.g., transport properties [12]. A study of the transport properties of the films revealed their direct dependence on the supramolecular structure of a polymer mixture. The starting systems have the following supramolecular particle parameters: average turbidity τ av = 1.41 cm 1, average particle size R = 6.4 μm, and number of particles in unit volume N = 7.4 108 cm 3 for a PVA solution (with acetone); τ av = 2.51 cm 1, R = 1.1 μm, and N = 27.1 1011 cm 3 for an AG solution. The results obtained for mixed PVA + AG solutions at various component ratios are presented in Fig. 1. It can be seen that the average radius and the number of particles depend on the relative amounts of arabinogalactan and PVA in a formulation. The average turbidity also depends on the AG concentration: the turbidity of the system steadily grows with increasing

POLYMERIC EYE FILMS BASED ON POLYVINYL ALCOHOL 607 AG content. The rise in the turbidity of the solutions, observed as the PVA/AG ratio is raised to n = 0.7, is indicative of a strong aggregation of macromolecules in the presence of the precipitating agent. This aggregation leads to formation of coarser particles, with the corresponding decrease in their number, and, therefore, these systems will be characterized by a reduced packing density of macromolecules. With the PVA/AG ratio raised further, R decreases with a simultaneous increase in N, which is due to the formation of a rather large number of dense globules with small sizes. At a PVA/AG ratio of 0.7, the average particle radius reaches its maximum value and the number of particles is at a minimum. Thus, by varying the ratio of the polymers in a mixture, it is possible to control the size of the particles being formed and, accordingly, the release of medicinal preparations from the polymer films. The interaction of AG with LVF was studied by means of spectrophotometry. Absorption spectra of LVF and LVF + AG mixtures in aqueous solutions in the presence of 0.1 M NaCl were studied. The electronic spectrum of LVF shows, at its concentration of 2.5 10 5 M in an aqueous solution, a single absorption peak at 285 nm. Upon addition of a comparable amount of AG into the solution, the intensity of the absorption peak becomes higher and it is slightly shifted to longer wavelengths to 290 nm. According to [13], the rise in the signal intensity and the shift of the absorption peak in UV spectra indicate that complexation occurs in the interaction of AG with LVF. To determine the composition of the resulting compound, the dependence of the absorption of (AG + LVF) solutions on the AG concentration at a constant concentration of LVF was obtained. The dependence of the optical density of LVF solutions on the arabinogalactan concentration shows that there is one LVF molecule per AG structural unit, i.e., the complex has a 1 : 1 composition. The data obtained were used to calculate the stability constant of the given complex. It was found to be 2.8 10 5 M 1, i.e., a medium-stability complex is formed in the interaction of AG with LVF. A study of the IR spectra of the complex revealed a strong broad absorption band at 3600 3200 cm 1, associated with stretching vibrations of hydroxy groups bound by hydrogen bonds. In the range 1200 1000 cm 1, there are a number of bands associated with stretching vibrations of the C O ether bond in pyranose and furanose rings. The spectra of the compounds obtained also show a shift to lower frequencies for the absorption peaks associated with stretching vibrations of OH groups and C O groups of glycoside by up to 90 cm 1 and by 10 20 cm 1, respectively. These spectral changes indicate that hydroxyl groups are involved in the interaction of AG with LVF [14]. Two MEF modifications were studied: films based on PVA and those based on PVA + AG. It can be seen in Fig. 2 that the films based on PVA + AG exhibit a more pronounced prolongation effect, compared with the PVA-based film. With the PVA/AG molar ratio increasing from 0.3 to 0.8, the release of LVF is retarded. The reason is that the supramolecular structure of the solutions changes in interaction of these two polymers. R, μm N 10 8, cm 3 LVF release, mg τ, h Fig. 1. Average size R and number N of supramolecular formations in the system vs. the PVA : Ag ratio n. The arrows point to the axis to which the curves belong. Fig. 2. Kinetics of LVF release fro medicated eye films. Films based on: (1) PVA; PVA/AG (mol/mol): (2) 1 : 0.3 and (3) 1 : 0.8. (τ) Time.

608 MUDARISOVA et al. The particles become smaller in size and, accordingly, their packing density increases, and just this circumstance determines the capacity of LVF to be retained within the film for a longer time. Compared with the PVA-based film, introduction of AG into a formulation makes the LVF prolongation duration 5 6 times longer. Higher AG concentrations in a formulation lead to brittleness of the films. An integrated study of the pharmacological activity of the films was carried out in two stages (series). In the first set of experiments, the tolerance of healthy rabbit eyes to MEFs was examined by the standard procedure. During a month, MEFs with LVF, based on PVA and PVA + AG, were introduced into rabbit eyes once a day, with the eyes examined every day by biomicroscopy. After the first set of experiments was complete, the rabbit eyes were subjected to a histological examination by the standard procedure. During the whole observation period (30 days), no indications of eye irritation and no noticeable changes in the internal eyeball structures of the animals were revealed in biomocroscopic studies. A histological analysis of denucleated rabbit eyes did not reveal any pathological changes in eyeball structures, either. In the second set of experiments, the content of LVF in the aqueous humor of the anterior eye chamber of rabbits was examined. The dynamics of variation of the LVF content of the conjunctival sac was determined after certain intervals of time upon a single introduction of eye drops and application of MEFs (see table). It can be seen in the table that the concentration of the antibiotic in the aqueous humor of the anterior chamber reached a maximum already 1 h after the instillation, and then sharply decreased. Upon application of a PVAbased MEF, the highest LVF concentration was observed during 4 8 h, with its subsequent decrease, and MEFs with arabinogalactan maintained a constant therapeutic concentration of the antibiotic in the aqueous humor of the anterior eye chamber during 24 h. Furthermore, film composites with AG favored full convalescence of eyes, whereas a reddening, residual inflammation, and purulent discharge remained in the case of eye drops and PVA-based films. Upon introductionof MEFs with AG, the concentration of levofloxacin in the aqueous humor of the anterior chamber was 14 times that upon instillation of this antibiotic. Thus, higher LVF concentrations and more prolonged preservation of the antibiotic concentration were observed in the group of animals for which medicated eye films with levofloxacin and arabinogalactan were used, compared with other groups. CONCLUSIONS (1) It was found using spectrophotometric methods that interaction of arabinogalactan with levofloxacin yields a medium-stability complex of 1 : 1 composition. (2) It was shown that the transport properties of films based on an arabinogalactan polyvinyl alcohol levofloxacin formulation depend on the supramolecular structure of the matrix. By varying the arabinogalactan concentration in the polymeric formulation, it is possible to control the macromolecular structure of the matrix and thereby affect the degree and rate of release of a medicinal preparation from films. (3) The pharmacological activity tests demonstrated that medicated eye films with levofloxacin and arabinogalactan lead to a pronounced prolongation of the effect of levofloxacin and strongly improve the penetration of the preparation into eye tissues and fluids, with the therapeutic concentration provided during the treatment. ACKNOWLEDGMENTS The study was financially supported by the Federal target program Scientific and Scientific-Pedagogical Pharmacodynamics of levofloxacin in tissues and fluids of rabbit eyes Sample Levofloxacin concentration, μg/ml, at indicated time of analysis, h 1 4 8 24 LVF (drops) 1.4 ± 0.20 0.8 ± 0.03 0.11 ± 0.02 0.1 ± 0.01 PVA + LVF 0.6 ± 0.30 1.0 ± 0.30 1.30 ± 0.20 1.0 ± 0.15 (PVA + AG) + LVF 0.7 ± 0.15 1.2 ± 0.02 1.50 ± 0.20 1.4 ± 0.10

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