Industrial & Engineering Chemistry Research, Vol.58, No.46, 21056-21069, 2019
Controlled Release of Glucose from Orally Delivered Temperature-and pH-Responsive Polysaccharide Microparticle Dispersions
Dual-responsive polysaccharide microgel dispersions were synthesized by the self-assembly of a temperature-responsive water-soluble cellulose ether, hydroxypropyl cellulose (HPC), and a pH-responsive polymer, sodium alginate (NaAlg). Spontaneous temperature-induced aggregation of aqueous HPC at a temperature above the lower critical solution temperature (LCST) of the polymer, in the presence of a surfactant (soy lecithin), resulted in microparticles that could be covalently cross-linked with trisodium trimetaphosphate (TSTMP). The microgel particles were saturated with a model carbohydrate, n-glucose (dextrose), and covered by a layer of alginic acid nanoparticles to obtain a controlled-release platform for sustained oral delivery of nutrients to athletes for improving their endurance capacity and exercise performance. Diffusion-cell studies of the in vitro release kinetics showed that the microgel dispersion released the absorbed glucose at a slower rate at pH 2, corresponding to the pH of gastric fluid, than at pH 7, corresponding to the pH of intestinal fluid. Furthermore, the rate of release of glucose from the microparticles was faster at a temperature above the LCST of the polymer particles. The LCSTs of the aqueous microgel dispersions were determined using rheology and calorimetric measurements and found to be strongly affected by the presence of kosmotropic solutes. Measurements of in vivo release kinetics in human subjects demonstrated that the temperature- and pH-responsive microgel dispersions were able to sustain higher concentrations of glucose in the blood plasma for a longer time, compared with conventional sugar solutions used as controls.