Design of PEG-based hydrogels as soft ionic conductors.

Conductive hydrogels have gained interest in biomedical applications and soft electronics. To tackle the challenge of ionic hydrogels falling short of desired mechanical properties in previous studies, our investigation aimed to understand the pivotal structural factors that impact the conductivity and mechanical behavior of polyethylene glycol (PEG)-based hydrogels with ionic conductivity. Polyether urethane diacrylamide (PEUDAm), a functionalized long-chain macromer based on PEG, was used to synthesize hydrogels with ionic conductivity conferred by incorporating ions into the liquid phase of hydrogel. The impact of salt concentration, water content, temperature, and gel formation on both mechanical properties and conductivity was characterized to establish parameters for tuning hydrogel properties. To further expand the range of conductivity available in these ionic hydrogels, 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) was incorporated as a single copolymer network or double network configuration. As expected, conductivity in these ionic gels was primarily driven by ion diffusivity and charge density, which was dependent on hydrogel network formation and swelling. Copolymer network structure had minimal effect on the conductivity which was primarily driven by counter-ion equilibrium; however, the mechanical properties and equilibrium swelling was strongly dependent on network structure. The structure-property relationships elucidated here enables the rationale design of this new double network hydrogel to achieve target properties for a broad range of applications.

Injectable hydrogel electrodes as conduction highways to restore native pacing.

There is an urgent clinical need for a treatment regimen that addresses the underlying pathophysiology of ventricular arrhythmias, the leading cause of sudden cardiac death. The current report describes the design of an injectable hydrogel electrode and successful deployment in a pig model with access far more refined than any current pacing modalities allow. In addition to successful cardiac capture and pacing, analysis of surface ECG tracings and three-dimensional electroanatomic mapping revealed a QRS morphology comparable to native sinus rhythm, strongly suggesting the hydrogel electrode captures the deep septal bundle branches and Purkinje fibers. In an ablation model, electroanatomic mapping data demonstrated that the activation wavefront from the hydrogel reaches the mid-myocardium and endocardium much earlier than current single-point pacing modalities. Such uniform activation of broad swaths of tissue enables an opportunity to minimize the delayed myocardial conduction of heterogeneous tissue that underpins re-entry. Collectively, these studies demonstrate the feasibility of a new pacing modality that most closely resembles native conduction with the potential to eliminate lethal re-entrant arrhythmias and provide painless defibrillation.

A user's guide to degradation testing of polyethylene glycol-based hydrogels: From in vitro to in vivo studies.

Poly(ethylene glycol) (PEG)-based hydrogels have gained significant attention in the field of biomedical applications due to their versatility and antifouling properties. Acrylate-derivatized PEG hydrogels (PEGDA) are some of the most widely studied hydrogels; however, there has been debate around the degradation mechanism and predicting resorption rates. Several factors influence the degradation rate of PEG hydrogels, including backbone and endgroup chemistry, macromer molecular weight, and polymer concentration. In addition to hydrogel parameters, it is necessary to understand the influence of biological and environmental conditions (e.g., pH and temperature) on hydrogel degradation. Rigorous methods for monitoring degradation in both in vitro and in vivo settings are also critical to hydrogel design and development. Herein, we provide guidance on tailoring PEG hydrogel chemistry to achieve target hydrolytic degradation kinetics for both resorbable and biostable applications. A detailed overview of accelerated testing methods and hydrogel degradation characterization is provided to aid researchers in experimental design and interpreting in vitro-in vivo correlations necessary for predicting hydrogel device performance.

Hydrogenation of benzene using aqueous solution of polyoxometalates reduced by CO over gold catalysts.

Aqueous polyoxometalate (H3PMo12O40) solution reduced by CO with liquid water using gold nanoparticle catalysts at room temperature, which contains protons in liquid water and electrons associated with the reduced polyoxometalate, can produce gaseous H2 or can hydrogenate benzene over an electrochemical cell consisting of a simple carbon anode, a proton-exchange membrane, and a Pt- or Rh-based cathode. In the present cell, H2 can be produced from the reduced H3PMo12O40 solution at voltages that are lower by about 1.15 V compared to water electrolysis.