Papers by Roberto C Andresen Eguiluz
Time-Dependent Physicochemical Changes of Carbonate Surfaces from SmartWater (Diluted Seawater) Flooding Processes for Improved Oil Recovery, 2018
Over the past few decades, field-and laboratory-scale studies have shown enhancements in oil reco... more 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 investigated the time dependence of the physicochemical processes that occur during diluted seawater (i.e., SmartWater) waterflooding processes of specific relevance to carbonate oil reservoirs. We measured the changes to oil/water/rock wettability, surface roughness, and surface chemical composition during SmartWater flooding using 10-fold-diluted seawater under mimicked oil reservoir conditions with calcite and carbonate reservoir rocks. Distinct effects due to SmartWater flooding were observed and found to occur on two different timescales: (1) a rapid (<15 min) increase in the colloidal electrostatic double-layer repulsion between the rock and oil across the SmartWater, leading to a decreased oil/ water/rock adhesion energy and thus increased water wetness and (2) slower (>12 h to complete) physicochemical changes of the calcite and carbonate reservoir rock surfaces, including surface roughening via the dissolution of rock and the reprecipitation of dissolved carbonate species after exchanging key ions (Ca 2+ , Mg 2+ , CO 3 2− , and SO 4 2− in carbonates) with those in the flooding SmartWater. Our experiments using crude oil from a carbonate reservoir reveal that these reservoir rock surfaces are covered with organic−ionic preadsorbed films (ad-layers), which the SmartWater removes (detaches) as flakes. Removal of the organic−ionic ad-layers by SmartWater flooding enhances oil release from the surfaces, which was found to be critical to increasing the water wetness and significantly improving oil removal from carbonates. Additionally, the increase in water wetness is further enhanced by roughening of the rock surfaces, which decreases the effective contact (interaction) area between the oil and rock interfaces. Furthermore, we found that the rate of these slower physicochemical changes to the carbonate rock surfaces increases with increasing temperature (at least up to an experimental temperature of 75 °C). Our results suggest that the effectiveness of improved oil recovery from SmartWater flooding depends strongly on the formation of the organic−ionic ad-layers. In oil reservoirs where the ad-layer is fully developed and robust, injecting SmartWater would lead to significant removal of the ad-layer and improved oil recovery.
Lubricin (LUB), a major mucinous glycoprotein of mammalian synovial fluids, is believed to provid... more 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 surface protection are needed. Here, we report the characterization of a lubricating multiblock bottlebrush polymer whose architecture was inspired by LUB, and we investigate the role of fibronectin (FN), a glycoprotein found in the superficial zone of cartilage, in mediating the tribological properties of the polymer upon shear between mica surfaces. Our surface forces apparatus (SFA) normal force measurements indicate that the lubricin-mimetic (mimLUB) could be kept anchored between mica surfaces, even under high contact pressures, when an intermediate layer of FN was present. Additional SFA friction measurements show that FN would also extend the wearless friction regime of the polymer up to pressures of 3.4 MPa while ensuring stable friction coefficients (μ ≈ 0.28). These results demonstrate synergistic interactions between mimLUB and FN in assisting the lubrication and wear protection of ideal (mica) substrates upon shear. Collectively, these findings suggest that our proposed mimLUB might be a promising alternative to LUB, as similar mechanisms could potentially facilitate the interaction between the polymer and cartilage surfaces in articular joints and prosthetic implants in vivo.
The vascular endothelium is subject to diverse mechanical cues that regulate vascular endothelial... more 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 extracellular matrix rigidity and intercellular force transduction, activated by vascular endothelial cadherin, coordinate to regulate the integrity of endothelial monolayers. Studies used complementary mechanical measurements of endothelial monolayers grown on patterned substrates of variable stiffness. Specifically perturbing VE-cadherin receptors activated intercellular force transduction signals that increased integrin-dependent cell contractility and disrupted cell-cell and cell-matrix adhesions. Further investigations of the impact of substrate rigidity on force transduction signaling demonstrated how cells integrate extracellular mechanics cues and intercellular force transduction signals, to regulate endothelial integrity and global tissue mechanics. VE-cadherin specific signaling increased focal adhesion remodeling and cell contractility, while sustaining the overall mechanical equilibrium at the mesoscale. Conversely, increased substrate rigidity exacerbates the disruptive effects of intercellular force transduction signals, by increasing heterogeneity in monolayer stress distributions. The results provide new insights into how substrate stiffness and intercellular force transduction coordinate to regulate endothelial monolayer integrity.
The glycoprotein lubricin is the primary boundary lubricant of articular cartilage. Its boundary ... more 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 trap water near a surface, reducing friction and facilitating glide. Synthetic analogues were previously created to mimic lubricin using thiol-terminated polyacrylic acid-graft-polyethylene glycol (pAA-g-PEG) brush copolymers. The PEG moiety was designed to mimic the mucin-like domain of lubricin and the thiol-terminus was designed to anchor the molecules to cartilage surfaces, mimicking the binding domain. In this study, these synthetic lubricin-mimetics were bound to gold-coated surfaces to characterize the relationship between the polymers' molecular architecture and their lubricating capacity. A library of nine copolymer brushes was synthesized using different sizes of pAA and PEG. Larger molecular weight polymers created smoother, more densely covered surfaces (p < 0.05). Additionally, the hydrodynamic sizes of the polymers in solution were correlated with their lubricating abilities (p < 0.05). Friction coefficients of cartilage against polymer-treated gold surfaces were lower than cartilage against untreated surfaces (Δμeq = − 0.065 ± 0.050 to − 0.093 ± 0.045, p < 0.05).
Pre-adipocytes exposed to tumor soluble factors
derived from MDA-MB-231 breast cancer cells, an i... more 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 tumorassociated
Fn was measured to be 87% more unfolded than that
of Fn deposited by control cells and correlated to being 62%
stiffer by the Förster Resonance Energy Transfer and Surface
Forces Apparatus techniques, respectively. The initial
dysregulated ECM lead to the rapid deposition of thick type I
collagen (Col I) fibers. Our findings suggest that initial unfolded
and stiff tumor-associated Fn ECMs promote altered cell-matrix
interactions to fuel tumor progression.
Obesity and extracellular matrix (ECM) density are considered independent risk and prognostic fac... more 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 enhancing interstitial ECM stiffness. Indeed, mammary fat of both diet- and genetically induced mouse models of obesity were enriched for myofibroblasts and stiffness-promoting ECM components. These differences were related to varied adipose stromal cell (ASC) characteristics because ASCs isolated from obese mice contained more myofibroblasts and deposited denser and stiffer ECMs relative to ASCs from lean control mice. Accordingly, decellularized matrices from obese ASCs stimulated mechanosignaling and thereby the malignant potential of breast cancer cells. Finally, the clinical relevance and translational potential of our findings were supported by analysis of patient specimens and the observation that caloric restriction in a mouse model reduces myofibroblast content in mammary fat. Collectively, these findings suggest that obesity-induced interstitial fibrosis promotes breast tumorigenesis by altering mammary ECM mechanics with important potential implications for anticancer therapies.
Fibronectin (FN) is a glycoprotein found in the superficial
zone of cartilage; however, its role ... more 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 (SA), which are all believed to contribute to joint lubrication. Using a Surface Forces Apparatus, we have measured the normal (adhesion/repulsion) and lateral (friction) forces across layers of individual synovial fluid components physisorbed onto FN-coated mica substrates. Our chief findings are (i) FN strongly tethers LUB and HA to mica, as indicated by high and reversible long-range repulsive normal interactions between surfaces, and (ii) FN and LUB synergistically enhance wear protection of surfaces during shear, as suggested by the structural robustness of FN+LUB layers under pressures up to about 4 MPa. These findings provide new insights into the role of FN in the lubricating properties of synovial fluid components sheared between ideal substrates and represent a significant step forward in our understanding of cartilage damage involved in diseases such as osteoarthritis.
Fibronectin (Fn) forms a fibrillar network that controls cell behavior in both physiological and ... more 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 tumor-associated Fn networks and (ii) its effect on tumor vascularization remain unclear. Here, we first used the Surface Forces Apparatus to reveal that 3T3-L1 preadipocytes exposed to tumor-secreted factors generate a stiffer Fn matrix relative to control cells. We then show that this early matrix stiffening correlates with increased molecular unfolding in Fn fibers, as determined by Förster Resonance Energy Transfer. Finally, we assessed the resulting changes in adhesion and proangiogenic factor (VEGF) secretion of newly seeded 3T3-L1s, and we examined altered integrin specificity as a potential mechanism of modified cell–matrix interactions through integrin blockers. Our data indicate that tumor-conditioned Fn decreases adhesion while enhancing VEGF secretion by preadipocytes, and that an integrin switch is responsible for such changes. Collectively, our findings suggest that simultaneous stiffening and unfolding of initially deposited tumor-conditioned Fn alters both adhesion and proangiogenic behavior of surrounding stromal cells, likely promoting vascularization and growth of the breast tumor. This work enhances our knowledge of cell – Fn matrix interactions that may be exploited for other biomaterials-based applications, including advanced tissue engineering approaches.
Theses by Roberto C Andresen Eguiluz
Surfaces in biology are present everywhere, and how biomacromolecules and cells interact with the... more Surfaces in biology are present everywhere, and how biomacromolecules and cells interact with them to form interfaces is crucial in cell biology, biotechnology and medicine. For example, biosensors are based on the specific recognition of sugars such as glucose in the glucose-sensors used by diabetic patients. Another example is found in cancer, where breast cancer cells secrete factors that interact with peripheral stromal cells (the interface) and alter their behavior. Another interesting example can be found in diarthrodial joints, such as the knee or the hip joint, where two opposing surfaces need efficient and durable interfacing as they slide against each other over the lifespan of a healthy person.
In the first part of this thesis, I present a direct quantitative correlation between the mechanics of the fibronectin extracellular matrix at the cellular scale and the conformation of fibronectin constituting the matrix at the molecular scale. Additionally, I analyze the effects of mechanics and conformation on cell behavior (adhesion and secretion) in a model system that represents the interface with the tumor.
Next, I present a phenomenological study of the molecular interactions between fibronectin (present in the superficial zone of cartilage) and synovial fluid components. I do this by examining their synergistic performance under confinement and shear to provide efficient lubrication. These results are compared with the tribological performance of a mimetic lubricin developed by my coworkers.
Combined, these results have important implications for our understanding of (i) tumor development and vascularization (ii) cell-matrix interactions (by providing new insights into the structure-mechanics relationship of protein networks), and (iii) the molecular mechanisms of boundary lubrication and wear
protection of articular surfaces. The findings presented in this work may be applied to future treatments of diseases such as breast cancer and osteoarthritis.
The microstructural change experienced by the surfaces of ductile tribologic alloys is of special... more The microstructural change experienced by the surfaces of ductile tribologic alloys is of special interest to achieve a reduction in the friction coef ficient and limits the wear of mechanical components such as journal bearings, extending their working life and consequently diminishing energy-related as well as economic costs. The present work analyses the tribolayer formed in a SAE 783 alloy (Al-20% Sn-1% Cu-0.6% Fe,% weight), used as the functional part in the mass production of small combustion engine journal bearings.
The alloy was subjected to several load and testing time conditions, employing a coaxial tribometer without lubrication and using AISI 9840 steel (Fe-0.4% C-0.25% Si-0.8% Mn-1% Ni-0.25% Mo,% weight) as the tribological counterpart. This was done to establish the effects of the already test conditions on the mechanical and microstructural properties of the new layer. Scanning electron microscopy and instrumented microindentation were used for analysis, revealing the existence of metastable microstructures and higher hardness, as a result of the high contact pressures achieved.
Two models to obtain the friction coefficient of the tribopair are presented. The first one, an analytical model, was developed from a force analysis and can be used to perform real time monitoring of the friction coeffi cient evolution. The second one, is based on parametric Finite Element Method simulations. Both models present enough arguments to continue being explored, so that good correlation with experimental results can be achived.
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Papers by Roberto C Andresen Eguiluz
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 tumorassociated
Fn was measured to be 87% more unfolded than that
of Fn deposited by control cells and correlated to being 62%
stiffer by the Förster Resonance Energy Transfer and Surface
Forces Apparatus techniques, respectively. The initial
dysregulated ECM lead to the rapid deposition of thick type I
collagen (Col I) fibers. Our findings suggest that initial unfolded
and stiff tumor-associated Fn ECMs promote altered cell-matrix
interactions to fuel tumor progression.
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 (SA), which are all believed to contribute to joint lubrication. Using a Surface Forces Apparatus, we have measured the normal (adhesion/repulsion) and lateral (friction) forces across layers of individual synovial fluid components physisorbed onto FN-coated mica substrates. Our chief findings are (i) FN strongly tethers LUB and HA to mica, as indicated by high and reversible long-range repulsive normal interactions between surfaces, and (ii) FN and LUB synergistically enhance wear protection of surfaces during shear, as suggested by the structural robustness of FN+LUB layers under pressures up to about 4 MPa. These findings provide new insights into the role of FN in the lubricating properties of synovial fluid components sheared between ideal substrates and represent a significant step forward in our understanding of cartilage damage involved in diseases such as osteoarthritis.
Theses by Roberto C Andresen Eguiluz
In the first part of this thesis, I present a direct quantitative correlation between the mechanics of the fibronectin extracellular matrix at the cellular scale and the conformation of fibronectin constituting the matrix at the molecular scale. Additionally, I analyze the effects of mechanics and conformation on cell behavior (adhesion and secretion) in a model system that represents the interface with the tumor.
Next, I present a phenomenological study of the molecular interactions between fibronectin (present in the superficial zone of cartilage) and synovial fluid components. I do this by examining their synergistic performance under confinement and shear to provide efficient lubrication. These results are compared with the tribological performance of a mimetic lubricin developed by my coworkers.
Combined, these results have important implications for our understanding of (i) tumor development and vascularization (ii) cell-matrix interactions (by providing new insights into the structure-mechanics relationship of protein networks), and (iii) the molecular mechanisms of boundary lubrication and wear
protection of articular surfaces. The findings presented in this work may be applied to future treatments of diseases such as breast cancer and osteoarthritis.
The alloy was subjected to several load and testing time conditions, employing a coaxial tribometer without lubrication and using AISI 9840 steel (Fe-0.4% C-0.25% Si-0.8% Mn-1% Ni-0.25% Mo,% weight) as the tribological counterpart. This was done to establish the effects of the already test conditions on the mechanical and microstructural properties of the new layer. Scanning electron microscopy and instrumented microindentation were used for analysis, revealing the existence of metastable microstructures and higher hardness, as a result of the high contact pressures achieved.
Two models to obtain the friction coefficient of the tribopair are presented. The first one, an analytical model, was developed from a force analysis and can be used to perform real time monitoring of the friction coeffi cient evolution. The second one, is based on parametric Finite Element Method simulations. Both models present enough arguments to continue being explored, so that good correlation with experimental results can be achived.
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 tumorassociated
Fn was measured to be 87% more unfolded than that
of Fn deposited by control cells and correlated to being 62%
stiffer by the Förster Resonance Energy Transfer and Surface
Forces Apparatus techniques, respectively. The initial
dysregulated ECM lead to the rapid deposition of thick type I
collagen (Col I) fibers. Our findings suggest that initial unfolded
and stiff tumor-associated Fn ECMs promote altered cell-matrix
interactions to fuel tumor progression.
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 (SA), which are all believed to contribute to joint lubrication. Using a Surface Forces Apparatus, we have measured the normal (adhesion/repulsion) and lateral (friction) forces across layers of individual synovial fluid components physisorbed onto FN-coated mica substrates. Our chief findings are (i) FN strongly tethers LUB and HA to mica, as indicated by high and reversible long-range repulsive normal interactions between surfaces, and (ii) FN and LUB synergistically enhance wear protection of surfaces during shear, as suggested by the structural robustness of FN+LUB layers under pressures up to about 4 MPa. These findings provide new insights into the role of FN in the lubricating properties of synovial fluid components sheared between ideal substrates and represent a significant step forward in our understanding of cartilage damage involved in diseases such as osteoarthritis.
In the first part of this thesis, I present a direct quantitative correlation between the mechanics of the fibronectin extracellular matrix at the cellular scale and the conformation of fibronectin constituting the matrix at the molecular scale. Additionally, I analyze the effects of mechanics and conformation on cell behavior (adhesion and secretion) in a model system that represents the interface with the tumor.
Next, I present a phenomenological study of the molecular interactions between fibronectin (present in the superficial zone of cartilage) and synovial fluid components. I do this by examining their synergistic performance under confinement and shear to provide efficient lubrication. These results are compared with the tribological performance of a mimetic lubricin developed by my coworkers.
Combined, these results have important implications for our understanding of (i) tumor development and vascularization (ii) cell-matrix interactions (by providing new insights into the structure-mechanics relationship of protein networks), and (iii) the molecular mechanisms of boundary lubrication and wear
protection of articular surfaces. The findings presented in this work may be applied to future treatments of diseases such as breast cancer and osteoarthritis.
The alloy was subjected to several load and testing time conditions, employing a coaxial tribometer without lubrication and using AISI 9840 steel (Fe-0.4% C-0.25% Si-0.8% Mn-1% Ni-0.25% Mo,% weight) as the tribological counterpart. This was done to establish the effects of the already test conditions on the mechanical and microstructural properties of the new layer. Scanning electron microscopy and instrumented microindentation were used for analysis, revealing the existence of metastable microstructures and higher hardness, as a result of the high contact pressures achieved.
Two models to obtain the friction coefficient of the tribopair are presented. The first one, an analytical model, was developed from a force analysis and can be used to perform real time monitoring of the friction coeffi cient evolution. The second one, is based on parametric Finite Element Method simulations. Both models present enough arguments to continue being explored, so that good correlation with experimental results can be achived.
In this study, we use Atomic force microscopy (AFM) and the Surface Forces Apparatus (SFA) to characterize the molecular characteristics, and the normal and friction forces of a lubricin-mimetic pAA-graft-PEG copolymer (pAA-62kDa, PEG-2kDa abbreviated pAA-g-PEG) interacting with fibronectin (Fn), a structural protein found in the superficial zone of cartilage[3],[4]. The normal and the lateral (friction) forces of pAA-g-PEG polymers were recorded using the SFA, in the presence and absence of Fn coating.
Collectively, these results have allowed for molecular and microscopic characterization of the pAA-g-PEG interactions with surfaces, gaining insight inot both the lubrication mechanisms and the interactions of the biomimetic polymer with tissue through Fn, indicating that our proposed lubricin-mimetic lubricant might be a promising affordable alternative to lubricin.
Materials and Methods: Poly(acrylic acid) was synthesized by RAFT polymerization using acrylic acid (AA). The pAA-graft-PEG (pAA-g-PEG) copolymer was synthesized by polymer analogous conjugation of monoamine-functionalized PEG to the pAA backbone.
AFM measurements were performed in air using a commercial AFM. Pyramidal SiO2 probes were used for intermittent contact mode imaging.
Normal and friction forces between two mimLUB-coated mica surfaces were measured using the SFA using well-established procedures[5].
Results and Discussion: Our AFM data indicated that the pAA-g-PEG molecules had an average contour length and a diameter of 72nm and 10nm, respectively, as indicated in Figure 1.
Our SFA data showed that the pAA-PEG polymer was only weakly adsorbed onto (negatively charged) bare mica surfaces but became firmly attached when Fn was added as a polymer linker, as presented in Figure 2.
All our friction data exhibited (i) low friction coefficients (µ ≈ 0.25) up to applied pressures of 3 MPa and (ii) Amonton's like behavior, as shown in Figure 3.
Conclusion: We report the design and characterization of a biomimetic lubricant (mimLUB) whose molecular architecture was inspired by lubricin, and the role of fibronectin in mediating mimLUB lubrication of ideal mica substrates. Although poor lubrication was achieved with mimLUB alone, enhanced wearless friction and surface protection were measured up to contact pressures of 4MPa when mimLUB was combined with FN. This effect was attributed to FN-mediated stronger binding of mimLUB to mica, which facilitates the formation (and retention) of a dense, robust, and highly hydrated (through PEG) repulsive brush that prevents polymer chain interpenetration when surfaces are sheared past each other, even under high pressures. As FN is abundant in the superficial zone of articular cartilage, our findings suggest that mimLUB could be a potential effective alternative to natural lubricin for the treatment of damaged cartilage surfaces or artificial joints, such as in the knee or the hip.
NSF under award DMR-1352299; CONACYT under award 308671; NIH under award 1R01AR066667-01; NIH Award Number 1S10RR023748-01
References:
[1] Swann, D. a; Sotman, S.; Dixon, M.; Brooks, C. The Isolation and Partial Characterization of the Major Glycoprotein (LGP-I) from the Articular Lubricating Fraction from Bovine Synovial Fluid. Biochem. J. 1977, 161, 473–485.
[2] Swann, D. a; Slayter, H. S.; Silver, F. H. The Molecular Structure of Lubricating Glycoprotein-I, the Boundary Lubricant for Articular Cartilage. J. Biol. Chem. 1981, 256, 5921–5925.
[3] Balazs, E. a. The Role of Hyaluronan in the Structure and Function of the Biomatrix of Connective Tissues. Struct. Chem. 2009, 20, 233–243.
[4] Chevalier, X. Fibronectin, Cartilage, and Osteoarthritis. Semin. Arthritis Rheum. 1993, 22, 307–318.
[5] Gourdon, D.; Yasa, M.; Alig, A. R. G.; Li, Y.; Safinya, C. R.; Israelachvili, J. N. Mechanical and Structural Properties of BaCrO 4 Nanorod Films under Confinement and Shear. Adv. Funct. Mater. 2004, 14, 239–242