Roberto Carlos Andresen Eguiluz

University of California, Merced | UCM · Materials Science and Engineering

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...

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...

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 o...

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 o...

In our previous paper (SPE-190281-MS), we presented results from a suite of multiscale experiments to understand interactions occurring across crude oil/brine/carbonate rock interfaces with different brine compositions. A new atomic to molecular scale mechanism was proposed based on changes in adhesion energies at different length- and time-scales...

The specific detection in clinical samples of analytes with dimensions in the tens to hundreds of nanometers, such as viruses and large proteins, would improve disease diagnosis. Detection of these “mesoscale” analytes (as opposed to their nanoscale components), however, is challenging as it requires the simultaneous binding of multiple recognition...

Significance Pathologic fibrosis is associated with altered collagen microarchitecture, but the functional impact of these changes on myofibroblast differentiation remains poorly understood. We experimentally and computationally analyzed the effect of collagen microstructure on matrix mechanics and determined its functional consequences on adipose-...

Marine mussels secrete proteins rich in residues containing catechols and cationic amines that displace hydration layers and adhere to charged surfaces under water via a cooperative binding effect known as catechol-cation synergy. Mussel-inspired adhesives containing paired catechol and cationic functionalities are a promising class of materials fo...

Using a surface forces apparatus (SFA), we quantitatively study the influence of surface damage on the contact mechanics of self-mated glassy polystyrene (PS) films. We use the SFA to measure contact radius, surface profile, and normal force between the films, including the adhesion force. The molecular weight (MW) of the polymer influences the rep...

The adhesion force between individual human hair fibers in a crosshair geometry was measured by observing their natural bending and adhesive jumps out of contact, using optical video microscopy. The hair fibers’ natural elastic responses, calibrated by measuring their natural resonant frequencies, were used to measure the forces. Using a custom-des...

Over the past few decades, field and laboratory scale studies have shown enhancements in oil recovery when reservoirs, which contain high-salinity formation water (FW), are waterflooded with modified-salinity salt water (widely referred to as the “low-salinity”, “dilution”, or “SmartWater” effect for improved oil recovery). In this study, we invest...

Waterflooding via injection of chemistry-optimized low-salinity – also, low ionic strength/concentration – waters, such as SmartWater, is becoming increasingly attractive for improved oil recovery, especially in carbonate reservoirs. In this manuscript, we describe the results from a series of experiments and theoretical modeling to determine the m...

Lubricin (LUB), a major mucinous glycoprotein of mammalian synovial fluids, is believed to provide excellent lubrication to cartilage surfaces. Consequently, when joint disease or replacement leads to increased friction and surface damage in the joint, robust synthetic LUB alternatives that could be used therapeutically to improve lubrication and s...

The vascular endothelium is subject to diverse mechanical cues that regulate vascular endothelial barrier function. In addition to rigidity sensing through integrin adhesions, mechanical perturbations such as changes in fluid shear stress can also activate force transduction signals at intercellular junctions. This study investigated how extracellu...

The glycoprotein lubricin is the primary boundary lubricant of articular cartilage. Its boundary lubricating abilities arise from two key structural features: i) a dense mucin-like domain consisting of hydrophilic oligosaccharides and ii) an end terminus that anchors the molecule to articulating surfaces. When bound, lubricin molecules attract and...

Introduction: Synthetic biolubricants have been widely investigated as coatings for implants and the treatment of diseases, such as osteoarthritis. However, particularly for osteoarthritis, there have been few effective lubricants. A mucin known as lubricin, found in the synovial fluid, is one compound responsible for the low friction and is known...

Obesity and extracellular matrix (ECM) density are considered independent risk and prognostic factors for breast cancer. Whether they are functionally linked is uncertain. We investigated the hypothesis that obesity enhances local myofibroblast content in mammary adipose tissue and that these stromal changes increase malignant potential by enhancin...

Fibronectin (FN) is a glycoprotein found in the superficial zone of cartilage, however, its role in the lubrication and the wear protection of articular joints is unknown. In this work, we have investigated the molecular interactions between FN and various components of the synovial fluid such as lubricin (LUB), hyaluronan (HA), and serum albumin (...

Fibronectin (Fn) forms a fibrillar network that controls cell behavior in both physiological and diseased conditions including cancer. Indeed, breast cancer-associated stromal cells not only increase the quantity of deposited Fn but also modify its conformation. However, (i) the interplay between mechanical and conformational properties of early tu...

Fibronectin (Fn) forms a fibrillar network that controls cell behavior in both physiological and diseased conditions including cancer. Indeed, breast cancer-associated stromal cells not only increase the quantity of deposited Fn but also modify its conformation. However, (i) the interplay between mechanical and conformational properties of early tu...

Pre-adipocytes exposed to tumor soluble factors derived from MDA-MB-231 breast cancer cells, an in vitro model of cancer-activated fibroblasts, deposited an initial extracellular matrix comprised primarily of fibronectin (Fn). This tumor-associated Fn was measured to be 87% more unfolded than that of Fn deposited by control cells and correlated to...

Multipotent adipose-derived stem cells (ASCs) are increasingly used for regenerative purposes such as soft tissue reconstruction following mastectomy; however, the ability of tumors to commandeer ASC functions to advance tumor progression is not well understood. Through the integration of physical sciences and oncology approaches we investigated th...

Although thick polymer brush layers are currently thought to be the best biomimetic lubricants, we have found that subnanometer-thick monolayers of of an algae polysaccharide can exhibit stable low friction and good wear protection, up to 11MPa and over a 1000-fold range of sliding velocities. Such remarkable tribological behavior is attributed to...

The microstructural change experienced by the surfaces of ductile tribologic alloys is of special interest to achieve a reduction in the friction coefficient and limit the wear of components such as journal bearings. The parameters mentioned above determine the performance and operating life of mechanical elements in relative motion. It can be seen...

Whether mechanically unfolded fibronectin (Fn) is present within native extracellular matrix fibrils is controversial. Fn extensibility under the influence of cell traction forces has been proposed to originate either from the force-induced lengthening of an initially compact, folded quaternary structure as is found in solution (quaternary structur...

Impact of Noise Variance on Measurements of Fn-DA (A) To determine the impact of PMT background variability on IA/ID, all IA/ID pixel measurements for a representative field of view within a denuded culture of cys/cys Fn-DA–containing fibrils were plotted versus donor intensity (filled circles). Standard deviations were calculated for all data poin...

The Impact of Photobleaching and Intermolecular FRET on Measurements of Fn-DA in Fibrils (A) Fn-u and Fn-DA were run on SDS-PAGE gels and stained with Coomassie blue. Lane contents from left to right are as follows: Fn-u, amine/cys Fn-DA, empty, molecular weight ladder, Fn-u reduced in 50 mM DTT, and amine/cys Fn-DA reduced in 50 mM DTT. (B) IA/ID...

Cys/cys Fn-DA in Matrix Fibrils (A–C) Cys/cys Fn-DA and excess Fn-u were added to culture medium of fibroblasts for 24 h. Color-coded IA/ID ratiometric images are shown for control cells (A), extracted cell-free matrix (B), and fibroblast cells after 60 min of exposure to the ROCK inhibitor Y-27632 (C). Scale bars = 50 μm. (D) Histograms were gener...

Strain Device Calibration To calibrate the degree of transverse compression relative to the magnitude of stretch applied to the PDMS membrane in the strain device, donor-labeled Fn was covalently linked to the PDMS substrate and photobleached into rectangular shapes. A 46 × 400 μm photobleached rectangle is shown before (A) and after (B) applicatio...

Schematic Diagram of the Strain Device The fully assembled strain device, shown upside down as a three-dimensional schematic for clarity (A), is composed of the main body (B) and end clamp pieces (C). All measurements are in millimeters. PDMS strips, 1.7 by 6 cm, were cut into rectangular or dog-bone shapes from 0.25-mm-thick sheets for surface mod...

Fibronectin Isolation, Measurement Noise, and Strain Device Calibration and Usage (72 KB DOC)

Z-Stack Overlay of the IA/ID and DIC Images of Fibronectin Matrix in Fibroblast Culture Amine/cys Fn-DA and excess Fn-u were added to culture medium of fibroblasts for 24 h. Color-coded IA/ID ratiometric images (A), transmitted DIC images (B), IA/ID images overlaid on DIC images (C), and the histogram for all pixels within each IA/ID image (D) are...