Carbohydrate Polymers 90 (2012) 637–643 Contents lists available at SciVerse ScienceDirect Carbohydrate Polymers jo u rn al hom epa ge: www.elsevier.com/locate/carbpol Carboxymethyl gum kondagogu: Synthesis, characterization and evaluation as mucoadhesive polymer Ashok Kumar, Munish Ahuja ∗ Drug Delivery Research Laboratory, Department of Pharmaceutical Sciences, Guru Jambheshwar University of Science and Technology, Hisar 125 001, India a r t i c l e i n f o Article history: Received 6 April 2012 Received in revised form 10 May 2012 Accepted 23 May 2012 Available online 8 June 2012 Keywords: Beads Gum kondagogu Ionic-gelation Ex vivo bioadhesion a b s t r a c t The objective of the study was to modify gum kondagogu by carboxymethylation and to evaluate it for potential pharmaceutical applications. Carboxymethylation of gum kondagogu was carried out by react- ing gum kondagogu with monochloroacetic acid under alkaline conditions. The results of characterization studies revealed that carboxymethylation of gum kondagogu increases its degree of crystallinity and sur- face roughness, reduces its viscosity and improves its mucoadhesive properties. Further, carboxymethyl gum kondagogu was explored for pharmaceutical applications by formulating ionotropically gelled beads using metformin as the model drug and calcium chloride as cross-linking agent. Ex vivo bioadhesion study conducted using isolated chick-ileum by wash-off test revealed bioadhesion of >80% over a period of 24 h. It was observed that increasing the concentration of cross-linking agent increases the % drug entrapment and reduces the release rate. The beads were found to release the drug by Fickian-diffusion mechanism and following zero-order release kinetics. © 2012 Elsevier Ltd. All rights reserved. 1. Introduction Natural gums have been used extensively in food and pharma- ceutical applications because of their easy availability, low cost, biocompatibility and biodegradability (Bhardwaj, Kanwar, Lal, & Gupta, 2000), but their applications are limited due to uncontrolled hydration, microbial contamination, pH dependent solubility and changes in viscosity during storage. Chemical modifications of nat- ural gums have been employed to improve their properties as biopolymer (Rana et al., 2011). Carboxymethylation is among one of the various strategies used for functionalization of natural poly- mers (Biswal & Singh, 2004). It is widely employed modification approach because of its ease of processing, lower cost of chemi- cals and versatility of the product. Carboxymethyl derivatives are usually polyelectrolyte with better aqueous solubility. During ear- lier studies this approach has been employed to synthesize high performance macromolecular materials (Boppana, Kulkarni, Setty, & Kalyane, 2010; Miyamoto, Tsuji, Nakamura, Tokita, & Komai, 1996). Carboxymethylation of polysaccharides is based on the William synthesis (Silva et al., 2004), in which the polysaccharide alkoxide is reacted with monochloroacetic acid and the primary and secondary alcohol groups are substituted by carboxymethyl group. Gum kondagogu (GK) is an important forest produce of Andhra Pradesh, India, which is collected by tribals by tapping from the ∗ Corresponding author. Tel.: +91 1662 263515; fax: +91 1662 276240. E-mail address: munishahuja17@yahoo.co.in (M. Ahuja). tree of Cochlospermum gossypium DC (Family: Bixaceae) (Janaki & Sashidhar, 1998). GK is an anionic polysaccharide belonging to the class of substituted rhamnogalacturonans. It comprises of rhamnose, galacturonic acid, glucuronic acid, -d-galactopyranose, -d-glucose, -d-glucose, galactose, arabinose, mannose and fruc- tose with sugar linkage of (1 → 2) -d-Gal p, (1 → 6) -d-Gal p, (1 → 4) -d-Glc p, 4-O-Me--d-Glc p, (1 → 2) -l-Rha (Vinod et al., 2008). It absorbs large amount of water forming thixotropic gels and during earlier studies it has been explored as sustained release matrix (Naidu et al., 2009), template matrix for synthesizing silver nanoparticles (Kora, Sashidhar, & Arunachalam, 2010), as emul- sifying agent (Vegi et al., 2009) and also for the preparation of mucoadhesive microspheres in combination with sodium alginate (Mankala, Nagamalli, Raprla, & Kommula, 2011). Modification of release behavior of GK matrix has been carried out by graft copoly- merization of acrylamide on GK backbone (Malik & Ahuja, 2011). In the present study, the chemical modification of GK has been carried out by carboxymethylation. Carboxymethyl gum kond- agogu (CMGK) was characterized by Fourier-transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), X- ray diffraction (XRD) and scanning electron microscopy (SEM). The degree of carboxymethyl substitution was determined by classical wet chemistry method. Rheological behavior of CMGK was stud- ied using Brookfield viscometer. The mucoadhesive performance of CMGK was assessed using texture profile analysis. CMGK was evaluated for pharmaceutical applications by formulating mucoad- hesive beads. Metformin an oral biguanide hypoglycemic agent which is ther- apeutically indicated for the management of type-2 diabetes was 0144-8617/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.carbpol.2012.05.089