Diffusion-driven instabilities in the BT-GN oscillatory carbonylation reaction network

\ua9 2024 Author(s).This study explores the role of diffusion in creating instabilities in the Bruk Temkin-Gorodsky Novakovic (BT-GN) oscillatory carbonylation reaction network. Stoichiometric network analysis and numerical methods revealed the presence of two destabilizing feedback cycles responsible for these instabilities. Analysis of a spatially uniform system showed that the saddle-node bifurcation can be simulated within the reaction network. The introduction of diffusion results in two types of instabilities: one occurs when a spatially uniform system is already unstable, leading to a reaction-diffusion front; and another involves diffusion-driven instabilities where introducing diffusion destabilizes a stable spatially uniform system. Slower PdI2 diffusion plays a key role in inducing these instabilities. Equations describing conditions for the emergence of the instabilities in both cases were derived

A reversible water-based electrostatic adhesive

\ua9 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH. Commercial adhesives typically fall into two categories: structural or pressure sensitive. Structural glues rely on covalent bonds formed during curing and provide high tensile strength whilst pressure-sensitive adhesives use physical bonding to provide weaker adhesion, but with considerable convenience for the user. Here, a new class of adhesive is presented that is also reversible, with a bond strength intermediate between those of pressure-sensitive and structural adhesives. Complementary water-based formulations incorporating oppositely charged polyelectrolytes form electrostatic bonds that may be reversed through immersion in a low or high pH aqueous environment. This electrostatic adhesive has the advantageous property that it exhibits good adhesion to low-energy surfaces such as polypropylene. Furthermore, it is produced by the emulsion copolymerization of commodity materials, styrene and butyl acrylate, which makes it inexpensive and opens the possibility of industrial production. Bio-based materials have been also integrated into the formulations to further increase sustainability. Moreover, unlike other water-based glues, adhesion does not significantly degrade in humid environments. Because such electrostatic adhesives do not require mechanical detachment, they are appropriate for the large-scale recycling of, e.g., bottle labels or food packaging. The adhesive is also suitable for dismantling components in areas as varied as automotive parts and electronics

Biofabrication Enables Efficient Interrogation and Optimization of Sequential Culture of Endothelial Cells, Fibroblasts, and Cardiomyocytes for Formation of Vascular Cords in Cardiac Tissue Engineering

Biofabrication of living structures with desired topology and functionality requires the interdisciplinary effort of practitioners of the physical, life and engineering sciences. Such efforts are being undertaken in many laboratories around the world. Numerous approaches are pursued, such as those based on the use of natural or artificial scaffolds, decellularized cadaveric extracellular matrices and, most lately, bioprinting. To be successful in this endeavor, it is crucial to provide in vitro micro-environmental clues for the cells resembling those in the organism. Therefore, scaffolds, populated with differentiated cells or stem cells, of increasing complexity and sophistication are being fabricated. However, no matter how sophisticated scaffolds are, they can cause problems stemming from their degradation, eliciting immunogenic reactions and other a priori unforeseen complications. It is also being realized that ultimately the best approach might be to rely on the self-assembly and self-organizing properties of cells and tissues and the innate regenerative capability of the organism itself, not just simply prepare tissue and organ structures in vitro followed by their implantation. Here we briefly review the different strategies for the fabrication of three-dimensional biological structures, in particular bioprinting. We detail a fully biological, scaffoldless, print-based engineering approach that uses self-assembling multicellular units as bio-ink particles and employs early developmental morphogenetic principles, such as cell sorting and tissue fusion

Vascular Endothelial Growth Factor Secretion by Nonmyocytes Modulates Connexin-43 Levels in Cardiac Organoids

We previously showed that the sequential, but not simultaneous, culture of endothelial cells (ECs), fibroblasts (FBs), and cardiomyocytes (CMs) resulted in elongated, beating cardiac organoids. We hypothesized that the expression of Cx43 and contractile function are mediated by vascular endothelial growth factor (VEGF) released by nonmyocytes during the preculture period. Cardiac organoids (200 μm diameter) were cultivated in microchannels to enable rapid screening. Three experimental groups were formed: (i) Simultaneous Preculture (ECs+FBs for 48 h, followed by CMs), (ii) Sequential Preculture (ECs for 24 h, FBs for 24 h, followed by CMs), and (iii) Simultaneous Triculture (ECs+FBs+CMs). Controls included CMs only, FBs only, and ECs only groups, and preculture with ECs only or FBs only. The highest VEGF levels were found in the Preculture groups [Simultaneous Preculture, 8.9 plus or minus 2.7 ng/(mL times h−1); Sequential Preculture, 16.6 plus or minus 3.4 ng/(mL times h−1)], as compared with Simultaneous Triculture where VEGF was not detectable, as shown by enzyme-linked immunosorbent assay. Analytical flow cytometry showed that VEGFR2 was expressed by ECs (86% plus or minus 2 VEGFR2+), FBs (44% plus or minus 1 VEGFR2+), and CMs (49% plus or minus 2 VEGFR2+), showing that all three cell types were capable of responding to changes in VEGF. Addition of anti-VEGF neutralizing IgG (0.4 μg/mL) to Simultaneous Preculture resulted in 3-fold decrease in Cx43 mRNA and 1.5-fold decrease in Cx43 protein, while Simultaneous Triculture supplemented with VEGF ligand (30 ng/mL) had a threefold increase in Cx43 mRNA and a twofold increase in Cx43 protein. Addition of a small molecule inhibitor of the VEGFR2 receptor (19.4 nM) to Sequential Preculture caused a 1.4-fold decrease in Cx43 mRNA and a 4.1-fold decrease in Cx43 protein. Cx43 was localized within CMs, and not within FBs or ECs. Enriched CM organoids and Sequential Preculture organoids grown in the presence of VEGFR2 inhibitor displayed low levels of Cx43 and poor functional properties. Taken together, these results suggest that endogenous VEGF-VEGFR2 signaling enhanced Cx43 expression and cardiac function in engineered cardiac organoids

Vac-and-fill: A micromoulding technique for fabricating microneedle arrays with vacuum-activated, hands-free mould-filling

We report a simple and reproducible micromoulding technique that dynamically fills microneedle moulds with a liquid formulation, using a plastic syringe, triggered by the application of vacuum (‘vac-and-fill’). As pressure around the syringe drops, air inside the syringe pushes the plunger to uncover an opening in the syringe and fill the microneedle mould without manual intervention, therefore removing inter-operator variability. The technique was validated by monitoring the plunger movement and pressure at which the mould would be filled over 10 vacuum cycles for various liquid formulation of varying viscosity (water, glycerol, 20% polyvinylpyrrolidone (PVP) solution or 40% PVP solution). Additionally, the impact of re-using the disposable syringes on plunger movement, and thus the fill pressure, was investigated using a 20% PVP solution. The fill pressure was consistent at 300–450 mbar. It produced well-formed and mechanically robust PVP, poly(methylvinylether/maleic anhydride) and hydroxyethylcellulose microneedles from liquid formulations. This simple and inexpensive technique of micromoulding eliminated the air entrapment and bubble formation, which prevent reproducible microneedle formation, in the resultant microneedle arrays. It provides a cost-effective alternative to the conventional micromoulding techniques, where the application of vacuum (‘fill-and-vac’) or centrifugation following mould-filling may be unsuitable, ineffective or have poor reproducibility

Bacteriological contamination of egg products after thermal preservation processes

Research was carried out to define the hygienic propriety of thermally treated eggs, i.e. eggs treated at pasteurization temperatures and those stored frozen. The average values of the number of the bacteria in the pasteurized yolk and egg white were log 4.9 and 5.1, respectively, those in the frozen-pasteurized yolk and egg white were log 5.5 and 4.8 and in the frozen yolk and white were log 7.0 and 5.9. The contaminants Salmonella spp., Proteus spp., Staphylococcus aureus, Escherichia coli, Clostridium spp., Clostridium perfringens, Pseudomonas spp., Campylobacter jejuni and Yersinia enterocolitica were tested for 306 samples of pasteurized, frozen and pasteurized and frozen products of eggs, egg-yolks and egg-whites. Presence of Salmonella spp. in the pasteurized yolk was 12%, Clostridium spp. 16%, E. coli 16% and Proteus spp. 14%, but in the pasteurized egg white those bacteria were present in 10.8%, 15.3%, 13.8% and 10.0%. Staphylococcus aureus was isolated in yolk at 4.6 and in white 4.0% and Clostridium perfringens 4.0 and 1.5%, respectively. The bacteriological flora indicated that the degree of contamination of egg-products depends directly on the degree of initial contamination and correlates with the technological egg-treatment processes applied

Некоторые особенности концентрационных колебаний в реакции окислительного карбонилирования фенилацетилена

Some modes of concentration oscillations in the homogeneous system KI-PdI2-CO-O2-CH3OH are described in this paper. Described modes of phenylacetylene oxidative carbonylation reaction in this system have some distinctive features. The further studies would reveal the reasons of these special modes and help one to understand in more details the mechanism of concentration oscillations of unsaturated compounds occurring in the carbonylation reactions.В данной статье описаны некоторые режимы концентрационных колебаний в гомогенной системе KI-PdI2-CO-O2-CH3OH. Описываемые режимы реакции окислительного карбонилирования фенилацетилена в этой системе имеют некоторые характерные особенности. Дальнейшие исследования должны выявить причины возникновения этих особых режимов, а также помочь глубже понять механизм возникновения концентрационных колебаний в реакциях карбонилирования непредельных соединений