View metadata, citation and similar papers at core.ac.uk brought to you by CORE A. THAKUR et al., Sorption and Drug Release Studies from Semi-interpenetrating…, Chem. Biochem. Eng. Q., 28 (1) 105–115 (2014) 105 Sorption and Drug Release Studies from Semi-interpenetrating Polymer Networks of Chitosan and Xanthan Gum * A. Thakur, S. Monga, and R. K. Wanchoo Original scientific paper Dr. S. S. Bhatnagar University Institute of Chemical Engineering Received: April 10, 2013 & Technology, Panjab University, Chandigarh, India -160014 Accepted: October 28, 2013 Hydrogel films of Chitosan (CS) and Xanthan gum (XA) of compositions 100/0, 90/10, 80/20, 70/30, 60/40 and 50/50 (w/w) % were prepared and swollen in simulated gastric fluid (SGF) of pH 1.2 and simulated intestinal fluid (SIF) of pH 7.4. To impart stability in acidic environment, semi-interpenetrating polymer network (semi-IPNs) films were formed using glutaraldehyde (GA) as the crosslinking agent. With increase in XA concentration, equilibrium degree of swelling reduced in SGF as well as SIF indicating maximum intermolecular interactions for 50/50 CS/XA semi-IPN. The swelling data was observed to follow second order kinetics. Spectroscopic and thermal analyses of these semi-IPN films also suggest maximum intermolecular interactions for 50/50 CS/XA semi-IPN. The potential of using 50/50 semi-IPN in drug delivery was studied using amoxicillin. In-vitro drug release studies indicated higher drug release in SGF than in SIF suggesting dependence of amoxicillin release kinetics and diffusion coefficient on pH of the environment and drug loading. The results suggest that CS-based semi-IPNs with different crosslinker and XA concentration could be promising candidates for for- mulation in oral gastrointestinal delivery systems. Key words: Amoxicillin, chitosan, glutaraldehyde, hydrogels Introduction ity, biodegradability and biocompatibility. Chitosan (CS) is a linear polysaccharide composed of ran- Hydrogels are crosslinked three-dimensional domly distributed -(1–4)-linked D-glucosamine hydrophilic polymer networks capable of retaining (deacetylated unit) and N-acetyl-D-glucosamine a significant amount of water within their struc- (acetylated unit) (Fig. 1).4 It is produced commer- tures, and swell without dissolving in water.1 A hy- cially by deacetylation of chitin, the structural ele- drogel is formed when an organic polymer (natural ment in the exoskeleton of crustaceans (crabs, or synthetic) is crosslinked via covalent, ionic, or shrimp, etc.).5 CS is widely used in biomedical and hydrogen bonds to create a three-dimensional struc- pharmaceutical applications because of its unique 2 ture. Recently, much work has been carried out on chemical and biologic properties. It is a cationic the synthesis and characterization of pH- and tem- polysaccharide (pKa ~6.3) soluble at acidic pH, and perature-sensitive hydrogels by copolymerization bioadhesive, which increases retention at the site of and crosslinking. Interpenetrating polymer networks application and readily binds to negatively charged (IPNs) have also been synthesized and used in a surfaces such as mucosal membranes. Mucoadhe- wide range of applications including artificial im- sive formulations have been developed for ocular, plants, dialysis membranes, wound dressings, etc., nasal, buccal, gastrointestinal, and vaginal drug ad- suggesting their enormous potential as drug deliv- ery systems. IPNs are defined as a combination of two or more polymers, each in a network form, at least one of which is synthesized and/or crosslinked in the immediate presence of the other. Several re- views have been published describing both applica- tions and fundamental theory of IPNs.3 In the recent past, there has been considerable interest in developing controlled drug delivery sys- tems using natural polymers due to their non-toxic- Fig. 1 – Structure of Chitosan (adapted from J. H. Hamman, *Correspondence author email: [email protected]; “Chitosan based polyelectrolyte complexes as po- Tel.: +91-0172-2534930; Fax: +91-0172-2779173. tential carrier materials in drug delivery systems,”4) 106 A. THAKUR et al., Sorption and Drug Release Studies from Semi-interpenetrating…, Chem. Biochem. Eng. Q., 28 (1) 105–115 (2014) ministration. 6 Biodegradability and biocompatibili- kindly gifted by Ind-Swift Drugs Ltd, Parwanoo, ty of CS has been exploited for use in controlled India. Glutaraldehyde (25 %, w/v) and glacial acetic drug delivery systems.7 acid were purchased from Loba Chemie and hydro- Xanthan gum (XA) is another extensively investi- chloric acid (35 %, w/v) was procured from Qual- gated water-soluble heteropolysaccharide natural poly- igens. Disodium dihydrogen phosphate, sodium hy- mer (Fig. 2). It is an anionic polymer with high molec- droxide and potassium chloride were of analytical ular weight (1–2 million), produced by pure culture grade. fermentation of a carbohydrate by naturally occurring bacterium Xanthomonas compestris,8,9 and is com- Characterization of chitosan monly used as viscosity controller in food industries The degree of deacetylation (DDA) of CS was due to its high viscosity in aqueous media. XA has calculated by the method described by Alovarez12 received considerable attention in the medical field as using (1), from the carbon (C) and nitrogen content it has been found to retard drug release.10,11 (N) of CS, which were determined using a Per- kin-Elmer Elemental Analyzer: 6.861 (CN / ) DDA 100 (1) 6.861 5.145 Determination of molecular weight of chitosan Intrinsic viscosity of chitosan in 0.2 mol L–1 –1 NaCl/0.1 mol L CH3COOH was measured using an Ubbelohde capillary viscometer in a constant temperature water bath (model CT 1450, Schott Gerate, Germany) at 25 ± 0.1°C in triplicate. Solu- Fig. 2 – Structure of Xanthan gum (adapted from A. Lachke, tion concentrations were adjusted based on the vis- Xanthan – A Versatile Gum.pdf8) cosity of the samples, so that the flow time was kept in the range of 100–150 s. The intrinsic viscosity [η] was determined by the common intercept of Since CS and XA are oppositely charged, they Huggins equation (hsp/C vs C) (2) and Kraemer’s are capable of forming polyelectrolyte complexes equation (ln hr/C vs C) (3) on the ordinate at infinite through electrostatic forces of attraction. Other sec- dilution (C→0).13 ondary forces like hydrogen bonding, hydrophobic h interactions, Van der Waals forces can also play a sp h[]kC [] h2 (2) role in the formation of complexes. As polyelectro- C lyte complex hydrogel films are pH sensitive, it was ln h proposed to prepare and study these for potential r h[]kC [] h2 (3) application as a drug delivery system. The aim of C this work was to develop biopolymer hydrogel films The viscosity-average molecular weight of chi- based on CS and XA that could be used under var- tosan was calculated using the classical Mark-Hou- ied pH conditions of gastrointestinal tract. Water wink eq. (4):13 absorption capacity and pH stability are important a properties to be considered for their use as a drug [η] = Km M (4) delivery system in addition to other relevant proper- where [h] is the intrinsic viscosity of chitosan, ties. The hydrogel films were investigated for their –3 Km = 1.81· 10 and a = 0.93 are constants for a swelling behavior in SGF and SIF as a function of given solute–solvent system and temperature.12,13 XA and GA concentration. Additionally, release of model drug amoxicillin from hydrogel films was studied in simulated gastric and intestinal fluid. Synthesis of physically crosslinked hydrogel films Chitosan films were cast from 2 % (w/v) CS solution prepared in 0.3 mol L–1 acetic acid on a Experimental petri dish (F = 90 mm) and allowed to dry at 37 °C. Material used The film was further dried in vacuum oven (20 in. Hg) to remove traces of moisture for about 24 h at Chitosan (low viscous) was purchased from 40 °C and stored in a desiccator. For CS/XA blends, Fluka Biochemika. Xanthan gum (pure, food grade) 2 % (w/v) solution was prepared with CS and XA was purchased from Loba Chemie. Amoxicillin was in varying weight ratios of 100/0, 90/10, 80/20, A. THAKUR et al., Sorption and Drug Release Studies from Semi-interpenetrating…, Chem. Biochem. Eng. Q., 28 (1) 105–115 (2014) 107 70/30, 60/40 and 50/50. XA solution was made in where Ww is the weight of swollen sample at time t, distilled water, while CS solution was prepared in and Wdi is the initial dry weight of the sample. 0.3 mol L–1 acetic acid. CS solution was added to When a hydrogel sample reached its equilibrium XA solution in appropriate amounts resulting in the state under a fixed condition, its degree of swelling formation of a non-homogeneous solution contain- was referred to as equilibrium degree of swelling. ing suspended particles of the polymer. This solu- The equilibrium state was achieved in 5 h for all the tion was stirred continuously for 72 h on a magnetic samples. All measurements were replicated three stirrer to obtain a homogeneous solution and then times for each sample. cast on a petri dish. Fourier transform infrared spectroscopy Synthesis of chemically crosslinked semi-IPN hydrogel films Spectroscopic structural elucidation of semi- 25 IPN films was done by FTIR using spectrophotom- Chemically crosslinked CS and CS/XA hy- eter (Bruker, model Tensor 27). The transmission drogel films were prepared by adding 5 % (v/v) GA spectra were collected at a resolution of 4 cm–1, in solution to homogeneous polymer solution prepared the range of 4000–500 cm–1. in the above section. To study the effect of cross- linker concentration on swelling behavior, varying X-Ray diffraction amounts of crosslinker were used i.e. 0.1, 0.2, 0.3 and 0.4 mL of 5 % v/v GA.