(96c) Computer Evaluation Of Hydrogel-Based Systems For The Closed Loop Treatment Of Type I Diabetes Mellitus

The recovery of diminished or lost regulatory functions of physiological systems drives important research efforts in biomaterials and modeling and control engineering. Hydrogels provide the multifunctionality of smart materials and the applicability to medical regulatory systems. The polymeric matrix of a hydrogel experiences reversible changes in volume in response to the pH of the environment, which depends on the presence of key metabolites in a physiological medium. The hydrogel swells due to internal repulsive electrostatic forces opening the matrix and releasing a preloaded drug. The contracted state of the hydrogel hinders the diffusion of the drug out of the polymer. In this paper, hydrogel membranes that incorporate glucose oxidase for the closed loop treatment of type I diabetes mellitus are characterized and modeled. The Sorensen compartmental model is extended to represent the treatment system of a diabetic patient. Physical parameters of the hydrogel material are obtained from experimental characterization. The performance of the system closed by a hydrogel-based device is explored and compared to the dynamic behavior of a conventional scheme with an explicit controller element. Anionic and cationic hydrogels are discussed for insulin delivery application. Simulations demonstrate limitations in the range of swelling and contraction of hydrogels in a physiological environment due to the Donnan equilibrium effect. Results show that insulin loading efficiency is critical for the long term service of a hydrogel-based device, while delivery by a diffusion mechanism is convenient since it allows a basal insulin supply. The evaluation of hydrogel macrosystems prompts the consideration of the detected pros and contras in hydrogel microsystems.