Modeling the dual oxygen-and pH-stimulated response of hemoglobin-loaded polyampholyte hydrogel for oxygen-pH coupled biosensor platform

This paper presents the dual oxygen-and pH-stimulated responsive performances of hemoglobin-loaded polyampholyte hydrogel, where a multiphysics model is formulated for the numerical characterization of the hydrogel, incorporating electrical interactions of the fixed-mobile charge groups and chemical reactions of the hemoglobin-oxygen complexes. A developed constitutive relation is integrated into the model to capture bioactivity of the immobilized hemoglobin as a function of ambient oxygen coupled with environmental pH. After examination with published experimental observations, it is concluded that the multiphysics model can accurately characterize both neonatal hemoglobin oxygen saturation and pH-driven volume transition behaviors of hemoglobin-loaded hydrogel. The results show that the swelling deformation of polyampholyte hydrogel changes in a bowl-shaped like pattern with increase of environmental pH value, whereas the rate of oxygen loaded into the hydrogel enlarges linearly with increase of physiological oxygen level from 1 to 30 mmHg. Consequently, these findings demonstrate that hemoglobin-loaded polyampholyte hydrogel could provide an innovative avenue for sensing and storing both bioactive oxygen and hydrogen solutes in biological fluids, pointing to a novel material platform for developing oxygen-pH stimuli coupled responsive biosensor, as well as oxygen- and/or pH-driven bio-actuators.