Publications by authors named "Martha E Grady"

14 Publications

  • Page 1 of 1

Nicotine induces morphological and functional changes in astrocytes via nicotinic receptor activity.

Glia 2021 Apr 14. Epub 2021 Apr 14.

Department of Chemistry, University of Kentucky, Lexington, Kentucky, USA.

Nicotine is a highly addictive compound present in tobacco, which causes the release of dopamine in different regions of the brain. Recent studies have shown that astrocytes express nicotinic acetylcholine receptors (nAChRs) and mediate calcium signaling. In this study, we examine the morphological and functional adaptations of astrocytes due to nicotine exposure. Utilizing a combination of fluorescence and atomic force microscopy, we show that nicotine-treated astrocytes exhibit time-dependent remodeling in the number and length of both proximal and fine processes. Blocking nAChR activity with an antagonist completely abolishes nicotine's influence on astrocyte morphology indicating that nicotine's action is mediated by these receptors. Functional studies show that 24-hr nicotine treatment induces higher levels of calcium activity in both the cell soma and the processes with a more substantial change observed in the processes. Nicotine does not induce reactive astrocytosis even at high concentrations (10 μM) as determined by cytokine release and glial fibrillary acidic protein expression. We designed tissue clearing experiments to test whether morphological changes occur in vivo using astrocyte specific Aldh1l1-tdTomato knock in mice. We find that nicotine induces a change in the volume of astrocytes in the prefrontal cortex, CA1 of the hippocampus, and the substantia nigra. These results indicate that nicotine directly alters the functional and morphological properties of astrocytes potentially contributing to the underlying mechanism of nicotine abuse.
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http://dx.doi.org/10.1002/glia.24011DOI Listing
April 2021

The effect of surface roughness on laser-induced stress wave propagation.

Appl Phys Lett 2020 Sep 24;117(12):121601. Epub 2020 Sep 24.

Department of Mechanical Engineering, University of Kentucky, Lexington, Kentucky 40506, USA.

We investigate laser-induced acoustic wave propagation through smooth and roughened titanium-coated glass substrates. Acoustic waves are generated in a controlled manner via the laser spallation technique. Surface displacements are measured during stress wave loading by the alignment of a Michelson-type interferometer. A reflective coverslip panel facilitates capture of surface displacements during loading of as-received smooth and roughened specimens. Through interferometric experiments, we extract the substrate stress profile at each laser fluence (energy per area). The shape and amplitude of the substrate stress profile are analyzed at each laser fluence. Peak substrate stress is averaged and compared between smooth specimens with the reflective panel and rough specimens with the reflective panel. The reflective panel is necessary because the surface roughness of the rough specimens precludes interferometry. Through these experiments, we determine that the surface roughness employed has no significant effect on substrate stress propagation and smooth substrates are an appropriate surrogate to determine stress wave loading amplitude of roughened surfaces less than 1.2 m average roughness (Ra). No significant difference was observed when comparing the average peak amplitude and loading slope in the stress wave profile for the smooth and rough configurations at each fluence.
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http://dx.doi.org/10.1063/5.0021021DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7594165PMC
September 2020

Near Simultaneous Laser Scanning Confocal and Atomic Force Microscopy (Conpokal) on Live Cells.

J Vis Exp 2020 08 11(162). Epub 2020 Aug 11.

Department of Mechanical Engineering, University of Kentucky;

Techniques available for micro- and nano-scale mechanical characterization have exploded in the last few decades. From further development of the scanning and transmission electron microscope, to the invention of atomic force microscopy, and advances in fluorescent imaging, there have been substantial gains in technologies that enable the study of small materials. Conpokal is a portmanteau that combines confocal microscopy with atomic force microscopy (AFM), where a probe "pokes" the surface. Although each technique is extremely effective for the qualitative and/or quantitative image collection on their own, Conpokal provides the capability to test with blended fluorescence imaging and mechanical characterization. Designed for near simultaneous confocal imaging and atomic force probing, Conpokal facilitates experimentation on live microbiological samples. The added insight from paired instrumentation provides co-localization of measured mechanical properties (e.g., elastic modulus, adhesion, surface roughness) by AFM with subcellular components or activity observable through confocal microscopy. This work provides a step by step protocol for the operation of laser scanning confocal and atomic force microscopy, simultaneously, to achieve same cell, same region, confocal imaging, and mechanical characterization.
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http://dx.doi.org/10.3791/61433DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7680637PMC
August 2020

Localization of Spiropyran Activation.

Langmuir 2020 Jun 17;36(21):5847-5854. Epub 2020 May 17.

Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, 1304 West Green Street, Urbana, Illinois 61801, United States.

Functionalization of planar and curved glass surfaces with spiropyran (SP) molecules and localized UV-induced activation of the mechanophore are demonstrated. Fluorescence spectra of UV-irradiated SP-functionalized surfaces reveal that increases in surface roughness or curvature produce more efficient conversion of the mechanophore to the open merocyanine (MC) form. Further, force-induced activation of the mechanophore is achieved at curved glass-polymer interfaces and not planar interfaces. Minimal fluorescence signal from UV-irradiated SP-functionalized planar glass surfaces precluded mechanical activation testing. Curved glass-polymer interfaces are prepared by SP functionalization of E-glass fibers, which are subsequently embedded in a poly(methyl methacrylate) (PMMA) matrix. Mechanical activation is induced through shear loading by a single fiber microbond testing protocol. detection of SP activation at the interface is monitored by fluorescence spectroscopy. The fluorescence increase during interfacial testing suggests that attachment of the interfacial SP molecule to both fiber surface and polymer matrix is present and able to achieve significant activation of SP at the fiber-polymer matrix interface. Unlike previous studies for bulk polymers, SP activation is detected at relatively low levels of applied shear stress. By linking SP at the glass-polymer interface and transferring load directly to that interface, a more efficient mechanism for eliciting the SP response is achieved.
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http://dx.doi.org/10.1021/acs.langmuir.0c00568DOI Listing
June 2020

Flexible Nanoparticles Reach Sterically Obscured Endothelial Targets Inaccessible to Rigid Nanoparticles.

Adv Mater 2018 Aug 28;30(32):e1802373. Epub 2018 Jun 28.

Department of Systems Pharmacology and Translational Therapeutics and Center for Translational Targeted Therapeutics and Nanomedicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA.

Molecular targeting of nanoparticle drug carriers promises maximized therapeutic impact to sites of disease or injury with minimized systemic effects. Precise targeting demands addressing to subcellular features. Caveolae, invaginations in cell membranes implicated in transcytosis and inflammatory signaling, are appealing subcellular targets. Caveolar geometry has been reported to impose a ≈50 nm size cutoff on nanocarrier access to plasmalemma vesicle associated protein (PLVAP), a marker found in caveolae in the lungs. The use of deformable nanocarriers to overcome that size cutoff is explored in this study. Lysozyme-dextran nanogels (NGs) are synthesized with ≈150 or ≈300 nm mean diameter. Atomic force microscopy indicates the NGs deform on complementary surfaces. Quartz crystal microbalance data indicate that NGs form softer monolayers (≈60 kPa) than polystyrene particles (≈8 MPa). NGs deform during flow through microfluidic channels, and modeling of NG extrusion through porous filters yields sieving diameters less than 25 nm for NGs with 150 and 300 nm hydrodynamic diameters. NGs of 150 and 300 nm diameter target PLVAP in mouse lungs while counterpart rigid polystyrene particles do not. The data in this study indicate a role for mechanical deformability in targeting large high-payload drug-delivery vehicles to sterically obscured targets like PLVAP.
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http://dx.doi.org/10.1002/adma.201802373DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6385877PMC
August 2018

Mitochondrial dynamics and respiration within cells with increased open pore cytoskeletal meshes.

Biol Open 2017 Dec 15;6(12):1831-1839. Epub 2017 Dec 15.

Department of Anesthesiology and Critical Care, Perelman School of Medicine, University of Pennsylvania, 3620 Hamilton Walk, John Morgan Building Room 27B, Philadelphia, PA 19104, USA

The cytoskeletal architecture directly affects the morphology, motility, and tensional homeostasis of the cell. In addition, the cytoskeleton is important for mitosis, intracellular traffic, organelle motility, and even cellular respiration. The organelle responsible for a majority of the energy conversion for the cell, the mitochondrion, has a dependence on the cytoskeleton for mobility and function. In previous studies, we established that cytoskeletal inhibitors altered the movement of the mitochondria, their morphology, and their respiration in human dermal fibroblasts. Here, we use this protocol to investigate applicability of power law diffusion to describe mitochondrial locomotion, assessment of rates of fission and fusion in healthy and diseased cells, and differences in mitochondria locomotion in more open networks either in response to cytoskeletal destabilizers or by cell line. We found that mitochondria within fibrosarcoma cells and within fibroblast cells treated with an actin-destabilizing toxin resulted in increased net travel, increased average velocity, and increased diffusion of mitochondria when compared to control fibroblasts. Although the mitochondria within the fibrosarcoma travel further than mitochondria within their healthy counterparts, fibroblasts, the dependence on mitochondria for respiration is much lower with higher rates ofhydrogen peroxide production and was confirmed using the OROBOROS O2K. We also found that rates of fission and fusion of the mitochondria equilibrate despite significant alteration of the cytoskeleton. Rates ranged from 15% to 25%, where the highest rates were observed within the fibrosarcoma cell line. This result is interesting because the fibrosarcoma cell line does not have increased respiration metrics including when compared to fibroblast. Mitochondria travel further, faster, and have an increase in percent mitochondria splitting or joining while not dependent on the mitochondria for a majority of its energy production. This study illustrates the complex interaction between mitochondrial movement and respiration through the disruption of the cytoskeleton.
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http://dx.doi.org/10.1242/bio.029009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5769657PMC
December 2017

The periodontal war: microbes and immunity.

Periodontol 2000 2017 10;75(1):52-115

Maintenance of periodontal health or transition to a periodontal lesion reflects the continuous and ongoing battle between the vast microbial ecology in the oral cavity and the array of resident and emigrating inflammatory/immune cells in the periodontium. This war clearly signifies many 'battlefronts' representing the interface of the mucosal-surface cells with the dynamic biofilms composed of commensal and potential pathogenic species, as well as more recent knowledge demonstrating active invasion of cells and tissues of the periodontium leading to skirmishes in connective tissue, the locality of bone and even in the local vasculature. Research in the discipline has uncovered a concerted effort of the microbiome, using an array of survival strategies, to interact with other bacteria and host cells. These strategies aid in colonization by 'ambushing, infiltrating and outflanking' host cells and molecules, responding to local environmental changes (including booby traps for host biomolecules), communicating within and between genera and species that provide MASINT (Measurement and Signature Intelligence) to enhance sustained survival, sabotage the host inflammatory and immune responses and by potentially adopting a 'Fabian strategy' with a war of attrition and resulting disease manifestations. Additionally, much has been learned regarding the ever-increasing complexity of the host-response armamentarium at both cellular and molecular levels that is addressed in this review. Knowledge regarding how these systems fully interact requires both new laboratory and clinical tools, as well as sophisticated modeling of the networks that help maintain homeostasis and are dysregulated in disease. Finally, the triggers resulting in a 'coup de main' by the microbiome (exacerbation of disease) and the characteristics of susceptible hosts that can result in 'pyrrhic victories' with collateral damage to host tissues, the hallmark of periodontitis, remains unclear. While much has been learned, substantial gaps in our understanding of the 'parameters of this war' remain elusive toward fulfilling the Sun Tzu adage: 'If you know the enemy and know yourself, you need not fear the result of a hundred battles.'
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http://dx.doi.org/10.1111/prd.12222DOI Listing
October 2017

Intracellular nanoparticle dynamics affected by cytoskeletal integrity.

Soft Matter 2017 Mar;13(9):1873-1880

Department of Anesthesiology and Critical Care, School of Medicine, University of Pennsylvania, USA.

The cell interior is a crowded chemical space, which limits the diffusion of molecules and organelles within the cytoplasm, affecting the rates of chemical reactions. We provide insight into the relationship between non-specific intracellular diffusion and cytoskeletal integrity. Quantum dots entered the cell through microinjection and their spatial coordinates were captured by tracking their fluorescence signature as they diffused within the cell cytoplasm. Particle tracking revealed significant enhancement in the mobility of biocompatible quantum dots within fibrosarcoma cells versus their healthy counterparts, fibroblasts, as well as in actin destabilized fibroblasts versus untreated fibroblasts. Analyzing the displacement distributions provided insight into how the heterogeneity of the cell cytoskeleton influences intracellular particle diffusion. We demonstrate that intracellular diffusion of non-specific nanoparticles is enhanced by disrupting the actin network, which has implications for drug delivery efficacy and trafficking.
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http://dx.doi.org/10.1039/c6sm02464eDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5333122PMC
March 2017

Cell elasticity with altered cytoskeletal architectures across multiple cell types.

J Mech Behav Biomed Mater 2016 08 1;61:197-207. Epub 2016 Feb 1.

Department of Anesthesiology and Critical Care, School of Medicine, University of Pennsylvania, 3620 Hamilton Walk, Philadelphia, PA 19104, United States. Electronic address:

The cytoskeleton is primarily responsible for providing structural support, localization and transport of organelles, and intracellular trafficking. The structural support is supplied by actin filaments, microtubules, and intermediate filaments, which contribute to overall cell elasticity to varying degrees. We evaluate cell elasticity in five different cell types with drug-induced cytoskeletal derangements to probe how actin filaments and microtubules contribute to cell elasticity and whether it is conserved across cell type. Specifically, we measure elastic stiffness in primary chondrocytes, fibroblasts, endothelial cells (HUVEC), hepatocellular carcinoma cells (HUH-7), and fibrosarcoma cells (HT 1080) subjected to two cytoskeletal destabilizers: cytochalasin D and nocodazole, which disrupt actin and microtubule polymerization, respectively. Elastic stiffness is measured by atomic force microscopy (AFM) and the disruption of the cytoskeleton is confirmed using fluorescence microscopy. The two cancer cell lines showed significantly reduced elastic moduli values (~0.5kPa) when compared to the three healthy cell lines (~2kPa). Non-cancer cells whose actin filaments were disrupted using cytochalasin D showed a decrease of 60-80% in moduli values compared to untreated cells of the same origin, whereas the nocodazole-treated cells showed no change in elasticity. Overall, we demonstrate actin filaments contribute more to elastic stiffness than microtubules but this result is cell type dependent. Cancer cells behaved differently, exhibiting increased stiffness as well as stiffness variability when subjected to nocodazole. We show that disruption of microtubule dynamics affects cancer cell elasticity, suggesting therapeutic drugs targeting microtubules be monitored for significant elastic changes.
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http://dx.doi.org/10.1016/j.jmbbm.2016.01.022DOI Listing
August 2016

Strain-rate Dependence of Elastic Modulus Reveals Silver Nanoparticle Induced Cytotoxicity.

Nanobiomedicine (Rij) 2015;2. Epub 2015 Sep 2.

Department of Materials Science Engineering, University of Pennsylvania, Pennsylvania, USA.

Force-displacement measurements are taken at different rates with an atomic force microscope to assess the correlation between cell health and cell viscoelasticity in THP-1 cells that have been treated with a novel drug carrier. A variable indentation-rate viscoelastic analysis, VIVA, is employed to identify the relaxation time of the cells that are known to exhibit a frequency dependent stiffness. The VIVA agrees with a fluorescent viability assay. This indicates that dextran-lysozyme drug carriers are biocompatible and deliver concentrated toxic material (rhodamine or silver nanoparticles) to the cytoplasm of THP-1 cells. By modelling the frequency dependence of the elastic modulus, the VIVA provides three metrics of cytoplasmic viscoelasticity: a low frequency modulus, a high frequency modulus and viscosity. The signature of cytotoxicity by rhodamine or silver exposure is a frequency independent twofold increase in the elastic modulus and cytoplasmic viscosity, while the cytoskeletal relaxation time remains unchanged. This is consistent with the known toxic mechanism of silver nanoparticles, where metabolic stress causes an increase in the rigidity of the cytoplasm. A variable indentation-rate viscoelastic analysis is presented as a straightforward method to promote the self-consistent comparison between cells. This is paramount to the development of early diagnosis and treatment of disease.
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http://dx.doi.org/10.5772/61328DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4732735PMC
September 2015

Molecular tailoring of interfacial failure.

Langmuir 2014 Sep 8;30(37):11096-102. Epub 2014 Sep 8.

Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign , 1206 W. Green Street, Urbana, Illinois 61801, United States.

Self-assembled monolayers (SAMs) provide an enabling platform for molecular tailoring of the chemical and physical properties of an interface. In this work, we systematically vary SAM end-group functionality and quantify the corresponding effect on interfacial failure between a transfer printed gold (Au) film and a fused silica substrate. SAMs with four different end groups are investigated: 11-amino-undecyltriethoxysilane (ATES), dodecyltriethoxysilane (DTES), 11-bromo-undecyltrimethoxysilane (BrUTMS), and 11-mercapto-undecyltrimethoxysilane (MUTMS). In addition to these four end groups, mixed monolayers of increasing molar ratio of MUTMS to DTES in solution are investigated. The failure of each SAM-mediated interface is initiated by a noncontact laser-induced spallation method at strain rates in excess of 10(6) s(-1). By making multiple measurements at increasing stress amplitudes (controlled by the laser fluence), we measure interface strengths of 19 ± 1.7, 20 ± 1.3, 52 ± 5.4, and 80 ± 6.5 MPa for interfaces functionalized with ATES, DTES, BrUTMS, and MUTMS, respectively. The interface strength is effectively tuned between the low strength of DTES and the high strength of MUTMS by controlling the concentration of MUTMS in solution. X-ray photoelectron spectroscopy of the failed interfaces reveals the influence of end group functionality on molecular dissociation, which significantly alters the failure process.
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http://dx.doi.org/10.1021/la502271kDOI Listing
September 2014

Shockwave loading of mechanochemically active polymer coatings.

ACS Appl Mater Interfaces 2014 Apr 1;6(8):5350-5. Epub 2014 Apr 1.

Department of Mechanical Science and Engineering University of Illinois at Urbana-Champaign 1206 W. Green Street, Urbana, Illinois 61801, United States.

Thin films of mechanochemically active polymer were subjected to laser-generated, high amplitude acoustic pulses. Stress wave propagation through the film produced large amplitude stresses (>100 MPa) in short time frames (10-20 ns), leading to very high strain rates (ca. 1 × 10(7) to 1 × 10(8) s(-1)). The polymer system, spiropyran (SP)-linked polystyrene (PS), undergoes a force-induced chemical reaction causing fluorescence and color change. Activation of SP was evident via a fluorescence signal in thin films subject to high strain-rates. In contrast, quasi-static loading of bulk SP-linked PS samples failed to result in SP activation. Mechanoresponsive coatings have potential to indicate deformation under shockwave loading conditions.
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http://dx.doi.org/10.1021/am406028qDOI Listing
April 2014

Effects of chemical bonding on heat transport across interfaces.

Nat Mater 2012 Apr 22;11(6):502-6. Epub 2012 Apr 22.

Interfaces often dictate heat flow in micro- and nanostructured systems. However, despite the growing importance of thermal management in micro- and nanoscale devices, a unified understanding of the atomic-scale structural features contributing to interfacial heat transport does not exist. Herein, we experimentally demonstrate a link between interfacial bonding character and thermal conductance at the atomic level. Our experimental system consists of a gold film transfer-printed to a self-assembled monolayer (SAM) with systematically varied termination chemistries. Using a combination of ultrafast pump-probe techniques (time-domain thermoreflectance, TDTR, and picosecond acoustics) and laser spallation experiments, we independently measure and correlate changes in bonding strength and heat flow at the gold-SAM interface. For example, we experimentally demonstrate that varying the density of covalent bonds within this single bonding layer modulates both interfacial stiffness and interfacial thermal conductance. We believe that this experimental system will enable future quantification of other interfacial phenomena and will be a critical tool to stimulate and validate new theories describing the mechanisms of interfacial heat transport. Ultimately, these findings will impact applications, including thermoelectric energy harvesting, microelectronics cooling, and spatial targeting for hyperthermal therapeutics.
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http://dx.doi.org/10.1038/nmat3303DOI Listing
April 2012

Autonomic restoration of electrical conductivity.

Adv Mater 2012 Jan 20;24(3):398-401. Epub 2011 Dec 20.

Department of Materials Science and Engineering, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, 1304 W. Green St. Urbana, IL 61801, USA.

Self-healing of an electrical circuit is demonstrated with nearly full recovery of conductance less than one millisecond after damage. Crack damage breaks a conductive pathway in a multilayer device, interrupting electron transport and simultaneously rupturing adjacent microcapsules containing gallium-indium liquid metal (top). The released liquid metal flows to the area of damage, restoring the conductive pathway (bottom).
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http://dx.doi.org/10.1002/adma.201102888DOI Listing
January 2012