Galactomannan crosslinking with a green plasticizer malonic acid and its biomedical applications

Abstract

Guar gum is a specialty galactomannan that serves as an abundant, renewable and sustainable feedstock. Nevertheless, its films cannot be used for sustained drug delivery due to certain drawbacks such as susceptibility towards microbial contamination, high swelling rate, non-porous structure, and brittleness. Therefore, functionalization of galactomannan has been achieved by crosslinking with malonic acid, a green, water-soluble, simple organic dicarboxylic acid with minimum chain length possessing natural plasticizer properties using a green chemistry approach. Interestingly, malonic acid also acts as an auto catalyst during acylation and subsequent crosslinking. The reaction conditions were optimized by varying the concentrations of malonic acid (0.5%, 1.5%, and 2% w/v), temperature (55 °C, 100 °C, 120 °C, and 140 °C) and time (5, 10, and 15 min) to introduce 1,3-propane dioates in the galactomannan chains resulting in flexible crosslinked films of galactomannans. Furthermore, the effect of low and high curing temperatures on crosslinking has been investigated by the analysis of the degree of crosslinking for the first time. The mechanism of crosslinking with a dicarboxylic acid has also been proposed. Detailed analysis of films has been achieved by NMR (1D & 2D), FTIR, XRD, TGA and DSC. Furthermore, curcumin has been loaded in these crosslinked films and kinetic studies via the Korsmeyer–Peppas model demonstrate that curcumin has a non-Fickian diffusion controlled release (DCR) mechanism. The antibacterial, antifungal and antioxidant studies show that the prepared formulation has potential utility in sustained drug delivery and other biomedical applications. Altogether, these studies provide a foundation to develop a sustained drug release system using crosslinked films for wound healing, anticancer therapy and many more.