Modeling and simulation of chemo-electro-mechanical behavior of pH-electric-sensitive hydrogel

A chemo-electro-mechanical multi-field model, termed the multi-effect-coupling pH-electric-stimuli (MECpHe) model, has been developed to simulate the response behavior of smart hydrogels subject to pH and electric voltage coupled stimuli when the hydrogels are immersed in a pH buffer solution subject to an externally applied electric field. The MECpHe model developed considers multiphysics effects and formulates the fixed charge density with the coupled buffer solution pH and electric voltage effects, expressed by a set of nonlinear partial differential governing equations. The model can be used to predict the hydrogel displacement and the distributive profiles of the concentrations of diffusive ionic species and the electric potential and the fixed charge density in both the hydrogels and surrounding solution. After validation of the model by comparison of current numerical results with experiment data extracted from the literature, one-dimensional steady-state simulations were carried out for equilibrium of the smart hydrogels subject to pH and electric coupled stimuli. The effects of several important physical conditions, including the externally applied electric voltage, on the distributions of the concentrations of diffusive ionic species, the electric potential, the fixed charge density, and the displacement of the hydrogel strip were studied in detail. The effects of the ionic strength on the bending deformation of the hydrogels under the solution pH and electric voltage coupled stimuli are also discussed.     

pH and reduction dual‐stimuli‐responsive PEGDA/PAMAM injectable network hydrogels via aza‐michael addition for anticancer drug delivery

A pH and reduction dual‐stimuli‐responsive PEGDA/PAMAM injectable network hydrogel containing “acetals” as pH‐sensitive groups and “disulfides” as reducible linkages was designed and synthesized via aza‐Michael addition reaction between PAMAM and PEGDA diacrylates. The pore size and swelling ratio of hydrogels was varied from 14 ± 3 to 19 ± 4 μm and 214 ± 13 to 300 ± 19 μm, respectively, with varying ethylene glycol repeating units in diacrylates. The swelling ratio of PEGDA/PAMAM network hydrogel increased with increase in the molecular weight of PEG and with decrease in pH. The presence of different cationizable amino‐functionalities in PEGDA/PAMAM network hydrogel helped to enhance the swelling ability of hydrogel under the acidic conditions. The continuous increase in metabolically active live HeLa cells with time in MTT assay implied biocompatibility/noncytotoxicity of the synthesized PEGDA/PAMAM injectable network hydrogel. Furthermore, the prepared PEGDA/PAMAM hydrogel showed higher degradation at lower pH and at higher concentration of DTT. The burst release of doxorubicin from PEGDA/PAMAM hydrogel under the environment of the lower pH and in presence of DTT compared to the release at normal physiological pH and in absence of DTT suggested the potential ability of this model hydrogel system for targeted and selective anticancer drug release at tumor tissues. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2080–2095