Biology subjects

Andresen Eguiluz, R. C.

Publications and source records attributed to Andresen Eguiluz, R. C..

3 recordsLinked to original sources

bioRxiv2023

Facile determination of the Poisson's ratio and Young's modulus of polyacrylamide gels and polydimethylsiloxane

Polyacrylamide hydrogels (PAH) and polydimethylsiloxane (PDMS) are two soft materials often used in cell mechanics and mechanobiology, in manufacturing lab-on-a chip applications, among others. This is partly due to the ability to tune their elasticity with ease, in addition to various chemical modifications. For affine polymeric networks, two (of three) elastic constants - the Youngs modulus (E), the shear modulus (G), and the Poissons ratio ({nu}) - describe the purely elastic response to external forces. However, the literature addressing the experimental determination of {nu} for PAH (also sometimes referred to as PAA gels in the literature) and PDMS is surprisingly limited when compared to the literature reporting values of E and G. Here, we present a facile method to obtain the Poisons ratio and Youngs modulus for PAH and PDMS based on static tensile tests, and cross-correlate these values with those obtained via a second independent method, shear rheology. We show that: i) the Poissons ratio may vary significantly from the value for incompressible materials ({nu} = 0.5), and ii) find a high degree of agreement between shear rheology and macroscopic static tension tests for PAH but not PDMS. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=121 SRC="FIGDIR/small/540222v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@120116forg.highwire.dtl.DTLVardef@58acbcorg.highwire.dtl.DTLVardef@1b48683org.highwire.dtl.DTLVardef@eb3fda_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2023

Natural and engineered isoforms of the inflammasome adaptor ASC form non-covalent, pH-responsive hydrogels

The protein ASC polymerizes into intricate filament networks to assemble the inflammasome, a filamentous multiprotein complex that triggers the inflammatory response. ASC carries two Death Domains integrally involved in protein self-association for filament assembly. We have leveraged this behavior to create non-covalent, pH-responsive hydrogels of full-length, folded ASC by carefully controlling the pH as a critical factor in the polymerization process. We show that natural variants of ASC (ASC isoforms) involved in inflammasome regulation also undergo hydrogelation. To further demonstrate this general capability, we engineered proteins inspired in the ASC structure that successfully form hydrogels. We analyzed the structural network of the natural and engineered protein hydrogels using transmission and scanning electron microscopy, and studied their viscoelastic behavior by shear rheology. Our results reveal one of the very few examples of hydrogels created by the self-assembly of globular proteins and domains in their native conformation and show that Death Domains can be used alone or as building blocks to engineer bioinspired hydrogels.

bioengineering↗

bioRxiv2021

Glycosaminoglycans and glycoproteins influence the elastic response of synovial fluid nanofilms on model oxide surfaces

Synovial fluid (SF) is the natural lubricant found in articulated joints, providing unique cartilage surface protecting films under confinement and relative motion. While it is known that the synergistic interactions of the macromolecular constituents provide its unique load-bearing and tribological performance, it is not fully understood how two of the main constituents, glycosaminoglycans (GAGs) and glycoproteins, regulate the formation and mechanics of robust load-bearing films. Here, we present evidence that the load-bearing capabilities, rather than the tribological performance, of the formed SF films depend strongly on its components integrity. For this purpose, we used a combination of enzymatic treatments, quartz crystal microbalance with dissipation (QCM-D) and the surface forces apparatus (SFA) to characterize the formation and load-bearing capabilities of SF films on model oxide (i.e., silicates) surfaces. We find that, upon cleavage of proteins, the elasticity of the films is reduced and that cleaving GAGs results in irreversible (plastic) molecular re-arrangements of the film constituents when subjected to confinement. Understanding thin film mechanics of SF can provide insight into the progression of diseases, such as arthritis, but may also be applicable to the development of new implant surface treatments or new biomimetic lubricants.

biophysics↗