Lorraine Siperko | University of Utah (original) (raw)

Papers by Lorraine Siperko

Journal of Materials Science Letters, 1993

Applied Physics Letters, Nov 23, 1992

A method for obtaining atomic scale images of powder samples by force microscopy has been used to... more A method for obtaining atomic scale images of powder samples by force microscopy has been used to determine surface structures of hydroxyapatite and brushite. From isolated hydroxyapatite crystal clusters, two crystal planes have been identified. The 〈001〉 and 〈110〉 spacings obtained agree well with published crystallographic values. Groups of brushite platelets yielded atomic spacings which are presumed to be those of the 〈110〉 crystal plane.

Electrochimica Acta, May 1, 1987

Abstract The potential response of cupric hexacyanoferrate (CuHCF) thin films on glassy carbon su... more Abstract The potential response of cupric hexacyanoferrate (CuHCF) thin films on glassy carbon substrate was studied by cyclic voltammetry in potassium and ammonium ions. The shift in potential with ammonium ion concentration is Nernstian with a difference of +0.70 V in 1 M NH + 4 with respect to 1 M K + . Equilibrium spectroelectrochemical studies have shown that the mole fraction of CuHCF is a reflection of film activity. Kinetic studies have indicated that the redox reaction is faster in ammonium ion than in potassium ion. Similarities and differences in the equilibrium and kinetic response of the film in both electrolytes are discussed.

In August 2009, an experimental water quality monitoring kit based on Colorimetric Solid Phase Ex... more In August 2009, an experimental water quality monitoring kit based on Colorimetric Solid Phase Extraction (CSPE) technology was delivered to the International Space Station (ISS). The kit, called the Colorimetric Water Quality Monitoring Kit (CWQMK), was launched as a Station ...

Journal of Physical Chemistry C, Oct 31, 2019

Journal of vacuum science & technology, Jul 1, 1987

Electrochemical and spectroscopic studies of layered Prussian blue (PB) and analogous cupric hexa... more Electrochemical and spectroscopic studies of layered Prussian blue (PB) and analogous cupric hexacyanoferrate (CuHCF) films indicate that charge transfer occurs across the film/film interface but the electrochemical response generated by a slowly ramped potential perturbation is dependent upon the placement of the films. When a PB film is deposited upon a CuHCF film, cracks appear at the outermost surface; however, the resulting response to the perturbation is merely a superposition of the two i–E waves. No cracking occurs when the layers are reversed (CuHCF on PB) but the resulting i–E wave is distorted. Possible causes for the distortion are proposed and discussed with respect to scanning electron microscopy/energy dispersive x-ray analysis results.

Journal of Applied Physiology, Nov 1, 2003

Mechanical forces play a role in the development and evolution of extracellular matrices (ECMs) f... more Mechanical forces play a role in the development and evolution of extracellular matrices (ECMs) found in connective tissue. Gravitational forces acting on mammalian tissues increase the net muscle forces required for movement of vertebrates. As body mass increases during development, musculoskeletal tissues and other ECMs are able to adapt their size to meet the increased mechanical requirements. However, the control mechanisms that allow for rapid growth in tissue size during development are altered during maturation and aging. The purpose of this mini-review is to examine the relationship between mechanical loading and cellular events that are associated with downregulation of mechanochemical transduction, which appears to contribute to aging of connective tissue. These changes result from decreases in growth factor and hormone levels, as well as decreased activation of the phosphorelay system that controls cell division, gene expression, and protein synthesis. Studies pertaining to the interactions among mechanical forces, growth factors, hormones, and their receptors will better define the relationship between mechanochemical transduction processes and cellular behavior in aging tissues.

Journal of vacuum science & technology, May 1, 1989

Raman studies show that the chemical etching of low-density polyethylene (LDPE) films by chromium... more Raman studies show that the chemical etching of low-density polyethylene (LDPE) films by chromium trioxide in sulfuric acid at 87 °C produces carbonyl groups (acid functionalities) within the film. A complexed chromium sulfato species, alkenes, and aldehyde functionalities are present on the etched surface. Etching by chromium trioxide in water under similar conditions produces bulk alkene and –C–O– groups (alcohols, peroxides) but no carbonyls. A chromium trioxide species is present on the surface, as are alkene and alkoxy groups. A chromium oxide species detected within the sulfuric acid etched films is not present in water etched films. The depth profile of chromium species within the chromium trioxide/sulfuric acid etched films detected by laser ablation/mass spectrometry shows the maximum concentration of this species lies several micrometers beneath the LDPE film surface, but for the chromium trioxide/water etch, chromium is present only on the surface of the film.

Journal of The Electrochemical Society, Sep 1, 1990

Les effets du courant anodique sur une electrode de pyrographite sont examines par microscopie tu... more Les effets du courant anodique sur une electrode de pyrographite sont examines par microscopie tunnel a balayage et spectroscopie Raman

Journal of The Electrochemical Society, Nov 1, 1986

Critical Reviews in Biomedical Engineering, 2003

Gravity plays a central role in vertebrate development and evolution. Gravitational forces acting... more Gravity plays a central role in vertebrate development and evolution. Gravitational forces acting on mammalian tissues cause the net muscle forces required for locomotion to be higher on earth than on a body subjected to a microgravitational fi eld. As body mass increases during development, the musculoskeleton must be able to adapt by increasing the size of its functional units. Th us mechanical forces required to do the work (mechanical energy) of locomotion must be sensed by cells and converted into chemical energy (synthesis of new tissue). Extracellular matrices (ECMs) are multicomponent tissues that transduce internal and external mechanical signals into changes in tissue structure and function through a process termed mechano chemical transduction. Under the infl uence of an external gravitational fi eld, both mineralized and unmineralized vertebrate tissues exhibit internal tensile forces that serve to preserve a synthetic phenotype in the resident cell population. Application of additional external forces alters the balance between the external gravitational force and internal forces acting on resident cells leading to changes in the expression of genes and production of protein that ultimately may alter the exact structure and function of the extracellular matrix. Changes in the equilibrium between internal and external forces acting on ECMs and changes in mechanochemical transduction processes at the cellular level appear to be important mechanisms by which mammals adjust their needs to store, transmit, and dissipate energy that is required during development and for bodily movements. Mechanosensing is postulated to involve many diff erent cellular and extracellular components. Mechanical forces cause direct stretching of protein-cell surface integrin binding sites that occur on all eukaryotic cells. Stress-induced conformational changes in the extracellular matrix may alter integrin structure and lead to activation of several secondary messenger pathways within the cell. Activation of these pathways leads to altered regulation of genes that synthesize and catabolize extracellular matrix proteins as well as to alterations in cell

Journal of vacuum science & technology, May 1, 1990

Applied Spectroscopy, Feb 1, 1989

The effects of chromic/sulfuric acid etchant on thin polyethylene films are being studied by Rama... more The effects of chromic/sulfuric acid etchant on thin polyethylene films are being studied by Raman spectroscopy. The functional groups on the surface of the etched films were found to differ from those present in the bulk. Cr-O bands appeared in both the bulk and SERS spectra, and sulfate species were detected on the surface only. The ability to differentiate between the surface and bulk polymer chemistry of CrO3/H2SO4-etched polyethylene using surface-enhanced Raman spectroscopy is demonstrated.

Journal of Biomedical Materials Research Part A, Jun 1, 2006

Bone cell-substrate interactions are important to understand in the design, selection, and surfac... more Bone cell-substrate interactions are important to understand in the design, selection, and surface modification of bone implants. To gain insight into such interactions, substrates designed with surface species approximating the physiological environment of bone matrix were studied. Osteoblasts (Ob) grown on three such surfaces were used to evaluate cell-substrate effects on attachment, growth, and gene expression as compared with controls. Initial surface preparation consisted of coating glass slides with aminopropyltriethoxy silane (APTES), after which the coated slides were modified with collagen-rich extracellular matrix components obtained from normally mineralizing avian tendon: the tripeptide arginine-glycine-aspartic acid (arg-gly-asp), or a precipitate formed from a metastable solution containing inorganic ions normally found in blood (simulated body fluid). Each of the modified substrates, as well as the nonmodified (APTES) control, provided distinctly different physical (evidenced by differences in rms roughness) and chemical surfaces for seeding primary osteoblasts obtained from 14-day-old normal embryonic chickens. Cell responses to each of the substrates were evaluated over a 21-day period in terms of Ob growth and growth rate, alkaline phosphatase (ALP) activity, and gene expression of type I collagen (COL I), osteopontin (OPN), osteocalcin (OC), and bone sialoprotein (BSP). From these preliminary experiments, indications are that cell attachment and growth in this study possibly are independent processes, an assumption that compels the need for further studies. Collagen-rich matrix-modified substrates had a distinct advantage over others when cell growth rate, ALP activity, and gene expression were considered; cells on these substrates exhibited increased ALP activity and enhanced expression of BSP, OPN, and OC when compared with those of cells on APTES controls or other modified substrates. These results indicate that matrix-modified substrates such as those used in this study provide favorable templates for tissue generation, suggesting their potential in the design of surfaces for bone implants.

Orthodontics & Craniofacial Research, Nov 1, 2005

Objectives-To develop models of human phalanges and small joints by suturing different cell-polym... more Objectives-To develop models of human phalanges and small joints by suturing different cell-polymer constructs that are then implanted in athymic (nude) mice. Design-Models consisted of bovine periosteum, cartilage, and/or tendon cells seeded onto biodegradable polymer scaffolds of either polyglycolic acid (PGA) or copolymers of PGA and poly-L-lactic acid (PLLA) or poly-e-caprolactone (PCL) and PLLA. Constructs were fabricated to produce a distal phalanx, middle phalanx, or distal interphalangeal joint. Setting and Sample Population-Studies of more than 250 harvested implants were conducted at the Northeastern Ohio Universities College of Medicine. Experimental Variable-Polymer scaffold, cell type, and implantation time were examined. Outcome Measure-Tissue-engineered specimens were characterized by histology, transmission electron microscopy, in situ hybridization, laser capture microdissection and qualitative and quantitative polymerase chain reaction analysis, magnetic resonance microscopy, and X-ray microtomography. Results-Over periods to 60 weeks of implantation, constructs developed through vascularity from host mice; formed new cartilage, bone, and/or tendon; expressed characteristic genes of bovine origin, including type I, II and X collagen, osteopontin, aggrecan, biglycan, and bone sialoprotein; secreted corresponding proteins; responded to applied mechanical stimuli; and maintained shapes of human phalanges with small joints. Conclusion-Results give insight into construct processes of tissue regeneration and development and suggest more

Journal of Structural Biology, Sep 1, 2001

Structural characteristics of normally calcifying leg tendons of the domestic turkey Meleagris ga... more Structural characteristics of normally calcifying leg tendons of the domestic turkey Meleagris gallopavo have been observed for the first time by tapping mode atomic force microscopy (TMAFM), and phase as well as corresponding topographic images were acquired to gain insight into the features of mineralizing collagen fibrils and fibers. Analysis of different regions of the tendon has yielded new information concerning the structural interrelationships in vivo between collagen fibrils and fibers and mineral crystals appearing in the form of plates and plate aggregates. TMAFM images show numerous mineralized collagen structures exhibiting characteristic periodicity (54-70 nm), organized with their respective long axes parallel to each other. In some instances, mineral plates (30-40 nm thick) are found interspersed between and in intimate contact with the mineralized collagen. The edges of such plates lie parallel to the neighboring collagen. Many of these plates appear to be aligned to form larger aggregates (475-600 nm long x 75-90 nm thick) that also retain collagen periodicity along their exposed edges. Intrinsic structural properties of the mineralizing avian tendon have not previously been described on the scale reported in this study. These data provide the first visual evidence supporting the concept that larger plates form from parallel association of smaller ones, and the data fill a gap in knowledge between macromolecular- and anatomic-scale studies of the mineralization of avian tendon and connective tissues in general. The observed organization of mineralized collagen, plates, and plate aggregates maintaining a consistently parallel nature demonstrates the means by which increasing structural complexity may be achieved in a calcified tissue over greater levels of hierarchical order.

Journal of Adhesion Science and Technology, 1989

�The primary goal of surface modification of fluoropolymers is to improve adhesion to these low s... more �The primary goal of surface modification of fluoropolymers is to improve adhesion to these low surface energy materials. Both classical methods and newer processes have been used as a means to this end. Various methods of modifying fluoropolymer surfaces include wet chemical etching, electrochemical reduction, grafting, application and removal of metals, ion and electron beam techniques, and plasma modification. In addition to the modification procedure, it is necessary to evaluate the effectiveness of the chosen method by subsequent analysis of the modified surface. Physical analytical methods include contact angle and wettability measurements, lap shear and composite tensile shear strengths, peel strengths, and surface topographical determinations. Chemical analyses used include infrared, Raman, Rutherford backscattering, ultraviolet-visible, wide angle X-ray scattering, X-ray fluorescence, and X-ray photoelectron spectroscopies as well as thermal desorption mass spectrometry. Each of the modification methods, with results of the subsequent chemical or physical analysis, will be discussed.

Skin Research and Technology, Jan 20, 2003

Background/aims: The influence of mechanical forces on skin has been examined since 1861 when Lan... more Background/aims: The influence of mechanical forces on skin has been examined since 1861 when Langer first reported the existence of lines of tension in cadaver skin. Internal tension in the dermis is not only passively transferred to the epidermis but also gives rise to active cell‐extracellular matrix and cell–cell mechanical interactions that may be an important part of the homeostatic processes that are involved in normal skin metabolism. The purpose of this review is to analyse how internal and external mechanical loads are applied at the macromolecular and cellular levels in the epidermis and dermis.Methods: A review of the literature suggests that internal and external forces applied to dermal cells appear to be involved in mechanochemical transduction processes involving both cell–cell and cell–extra‐cellular matrix (ECM) interactions. Internal forces present in dermis are the result of passive tension that is incorporated into the collagen fiber network during development. Active tension generated by fibroblasts involves specific interactions between cell membrane integrins and macromolecules found in the ECM, especially collagen fibrils. Forces appear to be transduced at the cell–ECM interface via re‐arrangement of cytoskeletal elements, activation of stretch‐induced changes in ion channels, cell contraction at adherens junctions, activation of cell membrane‐associated secondary messenger pathways and through growth factor‐like activities that influence cellular proliferation and protein synthesis.Conclusions: Internal and external mechanical loading appears to affect skin biology through mechanochemical transduction processes. Further studies are needed to understand how mechanical forces, energy storage and conversion of mechanical energy into changes in chemical potential of small and large macromolecules may occur and influence the metabolism of dermal cells.