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Hydrogels have become the material of choice in bioelectronic devices because their high‐water content leads to efficient ion transport and a conformal interface with biological tissue. While the morphology of hydrogels has been thoroughly studied, systematical studies on their ionic conductivity are less common. Here, an easy‐to‐implement strategy is presented to characterize the ionic conductivity of a series of polyelectrolyte hydrogels with different amounts of monomer and crosslinker and correlate their ionic conductivity with microstructure. Higher monomer increases the ionic conductivity of the polyelectrolyte hydrogel due to the increased charge carrier density, but also leads to excessive swelling that may cause device failure upon integration with bioelectronic devices. Increasing the amount of crosslinker can reduce the swelling ratio by increasing the crosslinking density and reducing the mesh size of the hydrogel, which cuts down the ionic conductivity. Further investigation on the porosity and tortuosity of the swollen hydrogels correlates the microstructure with the ionic conductivity. These results are generalizable for various polyelectrolyte hydrogel systems with other ions as the charge carrier and provide facile guidance to design polyelectrolyte hydrogel with desired ionic conductivity and microstructure for applications in bioelectronic devices. [ABSTRACT FROM AUTHOR]

Bioelectronic ion pumps deliver ions and biomolecules from a source to a target biological system with high spatiotemporal control for bioengineering and regenerative medicine applications. A voltage between a working electrode and a reference/counter electrode delivers the charged ions and biomolecules from a source to the desired target. The source and the target are separated by an ion exchange membrane so that only the charged molecules of interest are delivered. Future wearable and implantable applications require high efficiency of delivery to minimize power consumption. The majority of recent efforts on improving ion pump efficiency have focused on optimizing the ion exchange membrane. However, the contribution of the working electrode material to the ion pump efficiency has been mostly overlooked. This work identifies how changing the working electrode material greatly affects the efficiency of delivery in ion pumps. With an electrical circuit model analysis, voltammetry studies on silver, platinum, and palladium hydride working electrodes, and implementation of the Butler–Volmer equation, results show that the material‐dependent equilibrium potential at the working electrode surface has a large impact on ion pump efficiency. With this knowledge, a simple predictive model to optimize the working electrode material for delivering each specific ion or molecule of interest is designed. [ABSTRACT FROM AUTHOR]

The synthesis of a positively charged and water soluble chitosan derivative from chitosan is presented. [ABSTRACT FROM AUTHOR]

In article number 2100687 by Marco Rolandi and co-workers, the ionic conductivity and microstructure of a series of polyelectrolyte hydrogels are investigated to provide simple guidance for hydrogel design. B Front Cover b : Polyelectrolyte hydrogels have received increasing attention in bioelectronics because they allow ion transport and form a conformal interface with biological tissue. [Extracted from the article]

The top working electrode (WE) interfaces with the source solution, while the bottom reference/counter electrode (RE/CE) interfaces with the target solution. Bioelectronics, electrode materials, ion delivery, ion pumps, ions and biomolecules Keywords: bioelectronics; electrode materials; ion delivery; ion pumps; ions and biomolecules EN bioelectronics electrode materials ion delivery ion pumps ions and biomolecules 1 1 1 07/14/23 20230710 NES 230710 B Bioelectronic Ion Pumps b An example of an ion pump for delivering therapeutic ions and biomolecules is demonstrated in article 2201996, by Marco Rolandi and co-workers. [Extracted from the article]

Racemates often have lower solubility than enantiopure compounds, and the mixing of enantiomers can enhance the aggregation propensity of peptides. Amyloid beta (Aβ) 42 is an aggregation-prone peptide that is believed to play a key role in Alzheimer's disease. Soluble Aβ42 aggregation intermediates (oligomers) have emerged as being particularly neurotoxic. We hypothesized that the addition of mirror-image d-Aβ42 should reduce the concentration of toxic oligomers formed from natural l-Aβ42. We synthesized l- and D-Aβ42 and found their equimolar mixing to lead to accelerated fibril formation. Confocal microscopy with fluorescently labeled analogues of the enantiomers showed their colocalization in racemic fibrils. Owing to the enhanced fibril formation propensity, racemic Aβ42 was less prone to form soluble oligomers. This resulted in the protection of cells from the toxicity of l-Aβ42 at concentrations up to 50 μ m. The mixing of Aβ42 enantiomers thus accelerates the formation of non-toxic fibrils. [ABSTRACT FROM AUTHOR]

Racemates often have lower solubility than enantiopure compounds, and the mixing of enantiomers can enhance the aggregation propensity of peptides. Amyloid beta (Aβ) 42 is an aggregation-prone peptide that is believed to play a key role in Alzheimer's disease. Soluble Aβ42 aggregation intermediates (oligomers) have emerged as being particularly neurotoxic. We hypothesized that the addition of mirror-image d-Aβ42 should reduce the concentration of toxic oligomers formed from natural l-Aβ42. We synthesized l- and D-Aβ42 and found their equimolar mixing to lead to accelerated fibril formation. Confocal microscopy with fluorescently labeled analogues of the enantiomers showed their colocalization in racemic fibrils. Owing to the enhanced fibril formation propensity, racemic Aβ42 was less prone to form soluble oligomers. This resulted in the protection of cells from the toxicity of l-Aβ42 at concentrations up to 50 μ m. The mixing of Aβ42 enantiomers thus accelerates the formation of non-toxic fibrils. [ABSTRACT FROM AUTHOR]

Bioelectronic devices that modulate pH can affect critical biological processes including enzymatic activity, oxidative phosphorylation, and neuronal excitability. A major challenge in controlling pH is the high buffering capacity of many biological media. To overcome this challenge, devices need to be able to store and deliver a large number of protons on demand. Here, a bioelectronic modulator that controls pH using palladium nanoparticles contacts with high surface area as a proton storage medium is developed. Reversible electronically triggered acidosis (low pH) and alkalosis (high pH) in physiologically relevant buffer conditions are achieved. As a proof of principle, this new platform is used to control the degradation and fluorescence of acid sensitive polymeric microparticles loaded with a pH sensitive fluorescent dye. A bioelectronic modulator controls pH using palladium nanoparticle contacts as a proton storage medium. This powerful tool achieves reversible electronically triggered acidosis and alkalosis in physiologically relevant buffer conditions. [ABSTRACT FROM AUTHOR]

In article number 1800935, Marco Rolandi and co‐workers present a bioelectronic proton pump based on palladium hydride that changes pH in physiological conditions. [ABSTRACT FROM AUTHOR]

Bioelectronic devices that modulate pH can affect critical biological processes including enzymatic activity, oxidative phosphorylation, and neuronal excitability. A major challenge in controlling pH is the high buffering capacity of many biological media. To overcome this challenge, devices need to be able to store and deliver a large number of protons on demand. Here, a bioelectronic modulator that controls pH using palladium nanoparticles contacts with high surface area as a proton storage medium is developed. Reversible electronically triggered acidosis (low pH) and alkalosis (high pH) in physiologically relevant buffer conditions are achieved. As a proof of principle, this new platform is used to control the degradation and fluorescence of acid sensitive polymeric microparticles loaded with a pH sensitive fluorescent dye. [ABSTRACT FROM AUTHOR]