Grafting of Poly (Acrylic Acid) onto Cassia fistula Seed Gum: Synthesis, Optimization, and Characterization

Abstract

Aim: This study aimed to synthesize a natural polysaccharide-based semisynthetic mucoadhesive and sustained-release copolymer. 
 Background: Natural polysaccharides have been preferred as drug carriers because of their abundance, easy availability, low cost, biocompatibility, biodegradability, and physiochemical compatibility. But sometimes they need to be chemically functionalized in order to impart some physiochemical properties for the customization of drug delivery.
 Objective: The objective was to graft poly (sodium acrylate) onto Cassia fistula seed gum and the characterizations of the derived copolymer.
 Method: CFSG-grafted-poly (sodium acrylate) (CFSG-g-PSA) was synthesized by microwave-assisted free-radical initiation method using ceric ammonium nitrate (CAN) as a free-radical initiator. The concentration of acrylic acid (AA), ceric ammonium nitrate (CAN), and microwave-irradiation time (MW) were taken as independent synthetic variables. Synthesis was designed by 23 full factorial designs with two levels of each variable. %grafting, % grafting efficiency and % conversion was taken as response variables. ANOVA and numerical optimization were done using Design-Expert Software (version 11.0) to obtain the optimized synthetic condition. The copolymer was characterized by elemental analysis, FTIR, NMR, viscosity, DSC, TGA-DTA, PXRD, SEM, water-uptake, and biodegradation study.
 Results: Elemental analysis, FTIR, and NMR study ratified the formation of the copolymer. The highest % of grafting was found to be 790% in this study. The combination of microwave irradiation and CAN have shown a synergistic effect on % grafting and % grafting efficiency. Software-based numerical optimization finds the S1 batch as the best synthetic batch (790%G) with 10 g AA, 0.5 g CAN, and 1 min MW. The study also exhibits the biodegradation nature of the copolymer in a simulated colonic environment.
 Conclusion: The study demonstrates the synthesis of graft-copolymer by simple, easy, rapid, and one-pot method without the use of any sophisticated instrument and nitrogen environment.