Kinetic Study of the Esterase-like Activity of Albumin following Condensation by Macromolecular Crowding.

The ability of bovine serum albumin (BSA) to form condensates in crowded environments has been discovered only recently. Effects of this condensed state on the secondary structure of the protein have already been unraveled as some aging aspects, but the pseudo-enzymatic behavior of condensed BSA has never been reported yet. This article investigates the kinetic profile of para-nitrophenol acetate hydrolysis by BSA in its condensed state with poly(ethylene) glycol (PEG) as the crowding agent. Furthermore, the initial BSA concentration was varied between 0.25 and 1 mM which allowed us to modify the size distribution, the volume fraction, and the partition coefficient (varying from 136 to 180). Hence, the amount of BSA originally added was a simple way to modulate the size and density of the condensates. Compared with dilute BSA, the initial velocity (vi) with condensates was dramatically reduced. From the Michaelis-Menten fits, the extracted Michaelis constant Km and the maximum velocity Vmax decreased in control samples without condensates when the BSA concentration increased, which was attributed to BSA self-oligomerization. In samples containing condensates, the observed vi was interpreted as an effect of diluted BSA remaining in the supernatants and from the condensates. In supernatants, the crowding effect of PEG increased the kcat and catalytic efficiency. Last, Vmax was proportional to the volume fraction of the condensates, which could be controlled by varying its initial concentration. Hence, the major significance of this article is the control of the size and volume fraction of albumin condensates, along with their kinetic profile using liquid-liquid phase separation.

Resolution of Inflammation after Skeletal Muscle Ischemia-Reperfusion Injury: A Focus on the Lipid Mediators Lipoxins, Resolvins, Protectins and Maresins.

Skeletal muscle ischemia reperfusion is very frequent in humans and results not only in muscle destruction but also in multi-organ failure and death via systemic effects related to inflammation and oxidative stress. In addition to overabundance of pro-inflammatory stimuli, excessive and uncontrolled inflammation can also result from defects in resolution signaling. Importantly, the resolution of inflammation is an active process also based on specific lipid mediators including lipoxins, resolvins and maresins that orchestrate the potential return to tissue homeostasis. Thus, lipid mediators have received growing attention since they dampen deleterious effects related to ischemia-reperfusion. For instance, the treatment of skeletal muscles with resolvins prior to ischemia decreases polymorphonuclear leukocyte (PMN) infiltration. Additionally, remote alterations in lungs or kidneys are reduced when enhancing lipid mediators' functions. Accordingly, lipoxins prevented oxidative-stress-mediated tissue injuries, macrophage polarization was modified and in mice lacking DRV2 receptors, ischemia/reperfusion resulted in excessive leukocyte accumulation. In this review, we first aimed to describe the inflammatory response during ischemia and reperfusion in skeletal muscle and then discuss recent discoveries in resolution pathways. We focused on the role of specialized pro-resolving mediators (SPMs) derived from polyunsaturated fatty acids (PUFAs) and their potential therapeutic applications.

Polyarginine Decorated Polydopamine Nanoparticles With Antimicrobial Properties for Functionalization of Hydrogels.

Polydopamine (PDA) nanoparticles are versatile structures that can be stabilized with proteins. In this study, we have demonstrated the feasibility of developing PDA/polypeptides complexes in the shape of nanoparticles. The polypeptide can also render the nanoparticle functional. Herein, we have developed antimicrobial nanoparticles with a narrow size distribution by decorating the polydopamine particles with a chain-length controlled antimicrobial agent Polyarginine (PAR). The obtained particles were 3.9 ± 1.7 nm in diameter and were not cytotoxic at 1:20 dilution and above. PAR-decorated nanoparticles have exhibited a strong antimicrobial activity against S. aureus, one of the most common pathogen involved in implant infections. The minimum inhibitory concentration is 5 times less than the cytotoxicity levels. Then, PAR-decorated nanoparticles have been incorporated into gelatin hydrogels used as a model of tissue engineering scaffolds. These nanoparticles have given hydrogels strong antimicrobial properties without affecting their stability and biocompatibility while improving their mechanical properties (modulus of increased storage). Decorated polydopamine nanoparticles can be a versatile tool for the functionalization of hydrogels in regenerative medicine applications by providing bioactive properties.

The Overview of Porous, Bioactive Scaffolds as Instructive Biomaterials for Tissue Regeneration and Their Clinical Translation.

Porous scaffolds have been employed for decades in the biomedical field where researchers have been seeking to produce an environment which could approach one of the extracellular matrixes supporting cells in natural tissues. Such three-dimensional systems offer many degrees of freedom to modulate cell activity, ranging from the chemistry of the structure and the architectural properties such as the porosity, the pore, and interconnection size. All these features can be exploited synergistically to tailor the cell-material interactions, and further, the tissue growth within the voids of the scaffold. Herein, an overview of the materials employed to generate porous scaffolds as well as the various techniques that are used to process them is supplied. Furthermore, scaffold parameters which modulate cell behavior are identified under distinct aspects: the architecture of inert scaffolds (i.e., pore and interconnection size, porosity, mechanical properties, etc.) alone on cell functions followed by comparison with bioactive scaffolds to grasp the most relevant features driving tissue regeneration. Finally, in vivo outcomes are highlighted comparing the accordance between in vitro and in vivo results in order to tackle the future translational challenges in tissue repair and regeneration.

Validation of Milner's visco-elastic theory of sintering for the generation of porous polymers with finely tuned morphology.

Sacrificial sphere templating has become a method of choice to generate macro-porous materials with well-defined, interconnected pores. For this purpose, the interstices of a sphere packing are filled with a solidifying matrix, from which the spheres are subsequently removed to obtain interconnected voids. In order to control the size of the interconnections, viscous sintering of the initial sphere template has proven a reliable approach. To predict how the interconnections evolve with different sintering parameters, such as time or temperature, Frenkel's model has been used with reasonable success over the last 70 years. However, numerous investigations have shown that the often complex flow behaviour of the spheres needs to be taken into account. To this end, S. Milner [arXiv:1907.05862] developed recently a theoretical model which improves on some key assumptions made in Frenkel's model, leading to a slightly different scaling. He also extended this new model to take into account the visco-elastic response of the spheres. Using an in-depth investigation of templates of paraffin spheres, we provide here the first systematic comparison with Milner's theory. Firstly, we show that his new scaling describes the experimental data slightly better than Frenkel's scaling. We then show that the visco-elastic version of his model provides a significantly improved description of the data over a wide parameter range. We finally use the obtained sphere templates to produce macro-porous polyurethanes with finely controlled pore and interconnection sizes. The general applicability of Milner's theory makes it transferable to a wide range of formulations, provided the flow properties of the sphere material can be quantified. It therefore provides a powerful tool to guide the creation of sphere packings and porous materials with finely controlled morphologies.

CO2 Adsorption Capacities in Zeolites and Layered Double Hydroxide Materials.

The development of technologies that allow us to reduce CO2 emissions is mandatory in today's society. In this regard, we present herein a comparative study of CO2 adsorption over three types of materials: zeolites, layered double hydroxides (LDH), and zeolites coated LDH composites. The influence of the zeolite Si/Al ratio on zeolites sorption capacity along with the presence of mesopores was investigated. By comparing these results with the well-known performance of LDHs, we aim to provide insights on the factors that may influence the CO2 capture capacity over zeolites, thus providing useful tools for tuning their properties upon post-treatments.