Glycerol-crosslinked guar gum monoaldehyde based superabsorbent hydrogels for vitamin B6 (pyridoxine hydrochloride) delivery

A simple reaction was carried out to oxidize the plant polysaccharide, guar gum (GG) using a mixture of nitric acid and sodium nitrite. Superabsorbent hydrogels (SAH) were obtained by reacting the synthesized guar gum monoaldehyde with glycerol used as a crosslinker. The oxidation and crosslinking reactions were followed by spectroscopic methods, and the SAH were characterized by swelling studies, thermal analysis, scanning electron microscopy and porosity measurements. The hydrogels were able to absorb and retain a large quantity of water and artificial biological fluids without undergoing degradation and loss of their physical stability; the equilibrium degree of swelling was measured to be > 1500. The SAH were responsive toward pH and temperature changes, possessed thermal stability and good mechanical strength and were suitable for use in the delivery system for vitamin B6 (VB6). The stability of VB6-loaded gels was checked in simulated body fluids at lower pH, and the in vitro release of VB6 was studied in water and the acidic intestinal and gastric fluids. The release depended on the pH of the medium and the crosslinking density of the SAH; the concentration of released vitamin was measured to be 79.2%, 69.1% and 51.7% at pH 7.0, 4.5 and 1.5, respectively, from GEL-3, the lowest crosslinked polymer. The release kinetics study revealed that it followed a non-Fickian diffusion mechanism. The results indicate that the functionalized and crosslinked GG-based SAH could function as a delivery vehicle for food nutrients.Graphical abstract