Modeling and Simulation of the Ion-Binding-Mediated Swelling Dynamics of Mucin-like Polyelectrolyte Gels

Volume phase transitions in polyeletrolyte gels play important roles in many biophysical processes such as DNA packaging, nerve excitation, and cellular secretion. The swelling and deswelling of these charged polymer gels depend strongly on their ionic environment. In this paper, we present an extension to our previous two-fluid model for ion-binding-mediated gel swelling. The extended model eliminates the assumptions about the size similarity between the network and solvent particles, which makes it suitable for investigating of a large family of biologically relevant problems. The model treats the polyeletrolyte gel as a mixture of two materials, the network and the solvent. The dynamics of gel swelling is governed by the balance between the mechanical and chemical forces on each of these two materials. Simulations based on the model illustrate that the chemical forces are significantly influenced by the binding/unbinding reactions between the ions and the network, as well as the resulting distribution of charges within the gel. The dependence of the swelling rate on ionic bath concentrations is analyzed and this analysis highlights the importance of the electromigration of ions and the induced electric field in regulating gel swelling.

Cochlear implantation in osteogenesis imperfecta in India: a case report

<p class="abstract">A 25 years old male patient with osteogenesis imperfecta presented with bilateral profound hearing loss, not benefitted with hearing aid. Cochlear implantation of 12 channel intracochlear implant was done successfully, intracochlear insertion of the 12 electrodes resulted in hearing improvement of 80 dB at frequency 250 Hz to 4 KHz. The patient complained of facial twitching on first visit after switching on speech processer device, reducing the current level at the electrode 6 abolished the non-acoustic nerve excitation with preservation of acoustic performances. Osteogenesis imperfecta patient may involve a risk for non-acoustic nerve activation in cochlear implant patients possibly resulting from a decrease impedance to current spread, it happens because of abnormal bone tissue. Non acoustic nerve activation can be overcome by modification in mapping.</p>