Synthesis and Characterization of Triticale Starch-Based Hydrogel for pH Responsive Controlled Diffusion

Considering the FAO perspectives for agriculture toward 2030, many natural sources will be no longer profitable for the synthesis of many biomaterials. Triticale (X Triticosecale Wittmack) is a cereal crop synthesized to withstand those marginal conditions; however, it is primarily used as fodder worldwide. We reported for the first time the synthesis of a natural anionic hydrogel with gastrointestinal pH stimulus-response as a new alternative of smart material, based on Eronga triticale starch as sustainable biomass, using citrate (pK _a ∼3.1, 4.7, and 6.4) as cross-linking agent. The scanning electron microscopy and X-ray diffraction exhibited A and B-type starch granules, and semicrystallinity A-type. The presence of the anionic sensing group (COOH) was verified by infrared spectroscopy, the interactions by hydrogen bonds between starch and glycerol and esterification between starch and citric acid were identified by ¹H NMR spectra, and through thermal analysis hydrogels exhibited four endothermic curves (179-319 °C, ∼0.711-39 kJ/mol E _a). The results showed that the slight addition of glycerol increases the thermal stability, but a higher amount of glycerol decreases the intermolecular forces affecting the thermal stability contrary, the mechanical properties could be benefited. The rheological analyses showed viscoelastic tendency (G' > G″) with high stability (Tanδ < 1) in frequency, time, and strain sweeps. Gastrointestinal pH sensitivity (∼2-7.8) was verified (α ≤ 0.01) following Fick's diffusive parameters, which resulted in a tendency to gradually release BSA with increasing pH ∼3-7 by anomalous and case-II diffusion, showing greater release at pH ∼7.8/3.5 h (80-96%). We aim to expand the biomaterials area focusing on triticale starch due to its limited reported investigations, low-cost, green modification, and its rheological performance as plastic.