Skirt Material Research Articles

Biomimetic bone-like composites as osteo-odonto-keratoprosthesis skirt substitutes.

Osteo-odonto-keratoprostheses, incorporating dental laminate material as an anchoring skirt around a central poly(methyl methacrylate) (PMMA) optic, have been used to replace the cornea for many years. However, there are many intricacies associated with the use of autologous dental laminate material, surgical complexity and skirt erosion. Tissue engineering approaches to bone replacement may offer suitable alternatives in osteo-odonto-keratoprosthesis (OOKP) surgery. In this study, a hydrogel polymer composite was investigated as a synthetic substitute for the OOKP skirt. A novel high strength interpenetrating network (IPN) hydrogel composite with nano-crystalline hydroxyapatite (nHAp) coated poly (lactic-co-glycolic acid) PLGA microspheres was created to mimic the alveo-dental lamina by employing agarose and poly(ethylene glycol) diacrylate (PEGDA) polymers. The incorporation of nHAp coated PLGA microspheres into the hybrid IPN network provide a micro-environment similar to that of skeletal tissues and improve cellular response. Agarose was used as a first network to encapsulate keratocytes/3T3 fibroblasts and PEGDA (6000 Da) was used as a second network with varying concentrations (20 and 40 wt %) to produce a strong and biocompatible scaffold. An increased concentration of either agarose or PEG-DA and incorporation of nHAp coated PLGA microspheres led to an increase in the elastic modulus. The IPN hydrogel combinations supported the adhesion and proliferation of both fibroblast and ocular human keratocyte cell types during in in-vitro testing. The cells endured the encapsulation process into the IPN and remained viable at 1 week post-encapsulation in the presence of nHAp coated microspheres. The material did not induce significant production of inflammatory cytokine IL-6 in comparison to a positive control (p < 0.05) indicating non-inflammatory potential. The nHAp encapsulated composite IPN hydrogels are mechanically strong, cell supportive, non-inflammatory materials supporting their development as OOKP skirt substitutes using a new approach to dental laminate biomimicry in the OOKP skirt material.

Analysis of pulse-launched nanosatellite stability in the atmosphere

The article shows the effects of various aerodynamic parameters, the possibilities of their change are determined.The increase in the length of the lightweight stern, the diameter of the skirt and the thinning of the tube and skirt material improve the stability, but adversely affect the strength or aerodynamic properties of the product in question. The uniform distribution of mass over the nanosatellite volume is preferable in the process of acceleration with high-speed throw and exit from the railgun, but it negatively affects the stability in flight.

Electro-spun polyethylene terephthalate (PET) mat as a keratoprosthesis skirt and its cellular study

Artificial keratoprostheses are indispensable for visual rehabilitation in patients with end-stage corneal blindness. This study aimed to assess the biocompatibility of polyethylene terephthalate nanofibrous mats and its potential as a novel synthetic keratoprosthesis skirt material for corneal tissue engineering. Nanofibrous mats were prepared by an electrospinning method and were first treated with the CO2 plasma to yield carboxylic groups on the surface; finally, the modified PET mat was cross linked with collagen using water-soluble carbodiimide as a coupling agent. The samples were evaluated by ATR-FTIR, scanning electron microscope (SEM), contact angle, and cell culture. The cross-linking of collagen on PET surface was confirmed by ATR-FTIR spectroscopy and SEM images The 79° difference was obtained in the contact angle analysis, obtained for the collagen-cross-linked nanofibrous mat than the non-modified nanofibrous mat. Cellular investigation showed limbal epithelial progenitor cells (LEPCs) has been better adhesion, cell growth, and proliferation of collagen-crosslinked nanofibrous samples than other samples. The bioavailability of PET fibers with covalently attached collagen was found to be identical to that of PET fibers with covalent attachment is a suitable method for enhancing the biocompatibility of scaffolds special as a good skirt in keratoprosthesis designs.

Application of Graphene as Candidate Biomaterial for Synthetic Keratoprosthesis Skirt.

Synthetic keratoprostheses are required for visual rehabilitation in patients with end-stage corneal blindness. This study aimed to assess the biocompatibility of graphene material and its potential as a novel synthetic keratoprosthesis skirt material for corneal tissue engineering. Human corneal stromal fibroblasts were cultured on material surfaces including pristine graphene film, graphene foam, pristine titanium (Ti) discs, and tissue culture plastic surface (TCPS). Cell attachment was assayed by immunostaining of paxillin and vinculin. Cell viability and proliferation were assessed by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) and Click iT 5-ethynyl-2'-deoxyuridine (EdU) assays. The growth of fibroblasts on three-dimensional graphene foam was examined by scanning electron microscopy, and cytokine release was analyzed by enzyme-linked immunosorbent assay. Graphene films were implanted into rabbit corneal stromal pockets and examined by slit-lamp biomicroscopy, anterior segment optical coherence tomography, in vivo confocal microscopy, and histology. Pristine graphene demonstrated good biocompatibility with human stromal fibroblasts in terms of cell adhesion, viability, and proliferation. Cells on graphene films showed higher number than on TCPS control. Cells grown on graphene had 10% more proliferation than on Ti. The expression levels of IL-6 and IL-8 were reduced when cells were seeded on graphene foam as compared to Ti and graphene film. Implantation of graphene film into rabbit stroma (n = 6) did not show any signs of infection, neovascularization, or inflammation. Graphene displayed excellent short-term biocompatibility with corneal cells and tissue. This demonstrates that graphene can be developed as a tissue engineering material for use in cornea.

Surface Modification of PMMA to Improve Adhesion to Corneal Substitutes in a Synthetic Core-Skirt Keratoprosthesis.

Patients with advanced corneal disease do poorly with conventional corneal transplantation and require a keratoprosthesis (KPro) for visual rehabilitation. The most widely used KPro is constructed using poly(methyl methacrylate) (PMMA) in the central optical core and a donor cornea as skirt material. In many cases, poor adherence between the PMMA and the soft corneal tissue is responsible for device "extrusion" and bacterial infiltration. The interfacial adhesion between the tissue and the PMMA was therefore critical to successful implantation and device longevity. In our approach, we modified the PMMA surface using oxygen plasma (plasma group); plasma followed by calcium phosphate (CaP) coating (p-CaP); dopamine followed by CaP coating (d-CaP); or plasma followed by coating with (3-aminopropyl)triethoxysilane (3-APTES). To create a synthetic KPro model, we constructed and attached 500 μm thick collagen type I hydrogel on the modified PMMA surfaces. Surface modifications produced significantly improved interfacial adhesion strength compared to untreated PMMA (p < 0.001). The p-CaP group yielded the best interfacial adhesion with the hydrogel (177 ± 27 mN/cm(2)) followed by d-CaP (168 ± 31 mN/cm(2)), 3-APTES (145 ± 12 mN/cm(2)), and plasma (119 ± 10 mN/cm(2)). Longer-term stability of the adhesion was achieved by d-CaP, which, after 14 and 28 days of incubation in phosphate buffered saline, yielded 164 ± 25 mN/cm(2) (p = 0.906 compared to adhesion at day 1) and 131 ± 20 mN/cm(2) (p = 0.053), respectively. In contrast, significant reduction of adhesion strength was observed in p-CaP group over time (p < 0.001). All surface coatings were biocompatible to human corneal stromal fibroblasts, except for the 3-APTES group, which showed no live cells at 72 h of culture. In contrast, cells on d-CaP surface showed good anchorage, evidenced by the expression of focal adhesion complex (paxillin and vinculin), and prominent filopodia protrusions. In conclusion, d-CaP can not only enhance and provide stability to the adhesion of collagen hydrogel on the PMMA surface but also promote biointegration.

Biomechanical evaluation of different hydroxyapatite coatings on titanium for keratoprosthesis

Stable tissue integration is important to keratoprosthesis (KPro). The aim of this study was to evaluate the tissue bonding ability of hydroxyapatite (HAp)-coated titanium KPro. The samples were divided into three groups: test groups (IBAD group and AD group) and Ti control. The coated samples had a HAp layer created by ion beam assisted deposition (IBAD) or aerosol deposition (AD). The surface characteristics were analyzed with SEM, AFM, and XRD. The samples were surgically inserted into the muscles of rabbits. Eight weeks after healing, the attachment to the tissue was tested with a universal test device. The three samples exhibited distinctive surface morphology. The force to remove the HAp implants from the muscles was significantly greater than that of Ti group (P < 0.01), with the AD samples requiring the greatest force (P < 0.01). After removal, SEM showed that the tissue was firmly attached to the surface of AD samples. Photomicrographs of the peri-implant muscles showed a layer of aligned fibrous tissue without severe inflammation. The AD samples had more fibroblasts. Results indicate that because of enhanced mechanical adhesion of soft tissue to the implants, HAp-coated Ti by AD is a suitable KPro skirt material.

The Attenuation of Galvanic Corrosion Between Mechanically-Coupled Aluminum and Polymer Matrix Composites (PMCs) Using Hydrophobic, Insulative Skirt Materials

OBJECTIVE The objective of this research is to study the effect of hydrophobic, insulative skirt materials on the galvanic corrosion of mechanically-coupled aluminum and polymer matrix composites (PMCs)to develop effective corrosion mitigation solutions. INTRODUCTION Metal-PMC structures are being used more and more in military and civilian applications. PMCs, for example, are being used with greater frequency in defense, aerospace, automotive and civil-infrastructure industries. In the quest to reduce weight and increase performance, more and more advanced structures, systems and machines are being developed using a combination of alloys, composites, polymers, and ceramics. A system of dissimilar materials, however, may induce significant corrosion problems. Metal alloys coupled to composites may lead to crevice and galvanic corrosion problems. Corrosion control strategies need to be incorporated into the design of mechanically coupled metal-PMC joints to improve corrosion resistance and decrease maintenance and repair time. BACKGROUND Electrically conductive PMCs such as carbon fiber reinforced (CFR) PMC can accelerate the corrosion at PMC-Al interfaces by galvanic action and crevice corrosion. A typical method used to mitigate galvanic corrosion when bolting aluminum to CFR PMCs is to insert an insulating skirt between the members (Figure 1) to eliminate direct contact. However, aluminum and CFR PMCs are still galvanically coupled through the fastener; hence, galvanic corrosion can occur if the electrolyte bridges over the insulating skirt. To attenuate the galvanic effect, the insulating skirt can be extended beyond the CFR PMC coupon to various lengths (Figure 1). APPROACH The galvanic corrosion rate is a function of Ohmic loss (IR loss) between Al (anode) and PMC (cathode), and the polarization behavior of the anode and cathode. The Ohmic loss depends on the ionic conductivity of the electrolyte film that forms on the insulating skirt. The parameters that affect the ionic conductivity of the electrolyte film are salt loading (m’) (e.g., various Cl- concentrations), length of the insulating skirt (ls ), and humidity. A relationship between galvanic corrosion rate and skirt length-to-salt loading ratio (ls /m’) was established.Another parameter that affects the effective skirt length to attenuate galvanic corrosion is the continuity of the electrolyte layer on the skirt. Hence, hydrophobicity of the skirt material is an important parameter in determining the effective skirt length. The insulating skirts of various lengths were coated with different coatings (Figure 2) and the hydrophobicity was determined using contact angle measurements.The galvanic corrosion rate of 6061-T6 Al alloy coupled to CFR PMC were monitored over a 3-day period inside of a humidity chamber at 90% relative humidity (RH) and 30oC using the zero resistance ammeter (ZRA) technique with different skirt lengths which were coated and uncoated. The samples were sprayed with various concentrations of salt solutions. The galvanic corrosion rates were monitored for different types of coatings on the insulating skirt (hydrophobicity), electrolyte type, humidity, and various skirt lengths. Measurements were also be taken in the field. ACKNOWLEDGEMENTS The authors are grateful for the support from the Office of the Under Secretary of Defense for the project entitled “Corrosion and Corrosion Control Studies of Aluminum Alloys that are Mechanically-Coupled or Adhesively-Bonded to Polymer-Matrix Composites in Diverse Micro-Climates” (U.S. Air Force Academy, USAFA–BAA-2009-1). The authors are particularly grateful to Mr. Daniel Dunmire, Director, Corrosion Policy and Oversight, Office of the Under Secretary of Defense. The authors are also grateful to other members of the Department of Defense Technical Corrosion Collaboration: Mr. Richard Kinzie, Mr. Larry Lee, Dr. William Abbott, Dr. David Robertson, Mr. Richard Hays, and Dr. Christopher Scurlock.

Biomimetic developments to improve the OOKP

AbstractWhile the alveo‐dental tissue provides an excellent source for the Osteo‐odonto‐keratoprosthesis (OOKP) skirt with highest biointegrability anteriorly and inertness posteriorly, it brings with itself a number of disadvantages like oral trauma, laminar resorption, complex surgical technique and multiple stages of the procedure. Additionally, edentulous patients and those with unsuitable teeth are left with the options of less successful allografts and tibial bone carriers for the KPro. Therefore, a synthetic skirt material which, could avoid the problems of tooth extraction, complications of allografts and immunosuppression will be advantageous. A lamina available off the shelf can drastically minimise the surgical procedure duration and stages, and has the potential for replacements. A number of materials have been proposed using Dacron skirts (Pintucci), ceramics, corals, bioactive glass and titanium. These materials have advantages and disadvantages. However, a synthetic material that mimics the alveo‐dental tissue in porosity, mineral composition and biostability may prove suitable as a substrate for synthetic lamina.

Examining porous bio-active glass as a potential osteo-odonto-keratoprosthetic skirt material

Bio-active glass has been developed for use as a bone substitute with strong osteo-inductive capacity and the ability to form strong bonds with soft and hard tissue. The ability of this material to enhance tissue in-growth suggests its potential use as a substitute for the dental laminate of an osteo-odonto-keratoprosthesis. A preliminary in vitro investigation of porous bio-active glass as an OOKP skirt material was carried out. Porous glass structures were manufactured from bio-active glasses 1-98 and 28-04 containing varying oxide formulation (1-98, 28-04) and particle size range (250-315μm for 1-98 and 28-04a, 315-500μm for 28-04b). Dissolution of the porous glass structure and its effect on pH was measured. Structural 2D and 3D analysis of porous structures were performed. Cell culture experiments were carried out to study keratocyte adhesion and the inflammatory response induced by the porous glass materials. The dissolution results suggested that the porous structure made out of 1-98 dissolves faster than the structures made from glass 28-04. pH experiments showed that the dissolution of the porous glass increased the pH of the surrounding solution. The cell culture results showed that keratocytes adhered onto the surface of each of the porous glass structures, but cell adhesion and spreading was greatest for the 98a bio-glass. Cytokine production by all porous glass samples was similar to that of the negative control indicating that the glasses do not induce a cytokine driven inflammatory response. Cell culture results support the potential use of synthetic porous bio-glass as an OOKP skirt material in terms of limited inflammatory potential and capacity to induce and support tissue ingrowth.

Turnover Stability of Shuttlecocks - Transient Angular Response and Impact Deformation of Feather and Synthetic Shuttlecocks

This paper looks at the impact deformation and turnover stability of both feather and synthetic shuttlecocks using a racket based launcher. Flight of a shuttlecock can be described by steady state and unsteady state. Previous works were mainly focused on the steady state flight. While bulk of flight is in the steady state, the transient unsteady state is critical because it determines the initial condition of stabilized flight. The whole phase of rapid angular change during the unsteady state is the turnover process. Impact deformation and turnover response were studied with a racket-based launcher. Angles of attack with respect to time were recorded using high speed capturing. While the resultant plot showed significant variations between shuttles, most completed turnover process within 0.05s to 0.06s. Despite inherent disadvantage in density of the skirt material, turnover stability of synthetic shuttlecock was not compromised. All shuttles exhibited under damped behaviour in angular response and a 2nd order approximation was identified for the mean response of each. Feather shuttles have higher damping factor and smaller natural period. Higher-grade feather shuttle was observed to maintain skirt structural integrity better than lower tier shuttle in the impact deformation testing. Skirt stiffness is desirable to prevent deformation upon impact at higher racket speed. The practice grade feather shuttle displayed deformation pattern akin to a blooming flower, while the top grade shuttle was able to resist impact deformation at same racket speed. In conclusion, higher-grade shuttles could resist skirt deformation from racket-shuttle impact and attain steady state flight within a shorter time.

Comparison of Candidate Materials for a Synthetic Osteo-Odonto Keratoprosthesis Device

Osteo-odonto keratoprosthesis is one of the most successful forms of keratoprosthesis surgery for end-stage corneal and ocular surface disease. There is a lack of detailed comparison studies on the biocompatibilities of different materials used in keratoprosthesis. The aim of this investigation was to compare synthetic bioinert materials used for keratoprosthesis surgery with hydroxyapatite (HA) as a reference. Test materials were sintered titanium oxide (TiO(2)), aluminum oxide (Al(2)O(3)), and yttria-stabilized zirconia (YSZ) with density >95%. Bacterial adhesion on the substrates was evaluated using scanning electron microscopy and the spread plate method. Surface properties of the implant discs were scanned using optical microscopy. Human keratocyte attachment and proliferation rates were assessed by cell counting and MTT assay at different time points. Morphologic analysis and immunoblotting were used to evaluate focal adhesion formation, whereas cell adhesion force was measured with a multimode atomic force microscope. The authors found that bacterial adhesion on the TiO(2), Al(2)O(3), and YSZ surfaces were lower than that on HA substrates. TiO(2) significantly promoted keratocyte proliferation and viability compared with HA, Al(2)O(3,) and YSZ. Immunofluorescent imaging analyses, immunoblotting, and atomic force microscope measurement revealed that TiO(2) surfaces enhanced cell spreading and cell adhesion compared with HA and Al(2)O(3). TiO(2) is the most suitable replacement candidate for use as skirt material because it enhanced cell functions and reduced bacterial adhesion. This would, in turn, enhance tissue integration and reduce device failure rates during keratoprosthesis surgery.

Cell proliferation studies of novel biomaterials to be used as synthetic keratoprosthesis skirts

Abstract Purpose In vitro studies of human cornea stroma keratocyte proliferation and cytokine secretion on the various kerato‐prosthesis skirt material. In the development of an artificial cornea, an appropriate skirt material which encourages keratocytes proliferation is important to help wound healing and integration. Epidermal growth factor (EGF), insulin growth factor (IGF‐1) and hepatocyte growth factor (HGF) stimulate corneal keratocytes proliferation. IGF‐1 and EGF have an anti‐apoptotic effect of keratocytes. Conclusion: Methods Three materials were studied: Hydroxyappatite (HA), titanium substate (TiO2) and aluminium oxide substrate (Al2O3). Corneal stromal were seeded on top of these materials for EDU image assay and real time PCR analysing. Conditioned cell culture medium was collected for cytokine array. Results Cytokine array showed the levels of EGF, IGF‐1 and HGF were no statistical significance among the HA, TiO2 and Al2O3. RT‐PCR, showed that the expression level of EGF, IGF‐1 and HGF were highest with TiO2 substrates and lowest with HA substrates with statistical significance. Edu assay showed a comparable number of proliferating cells on the HA and TiO2 with significantly more cells on the Al2O3 dics. Conclusion TiO2 is a comparable material to HA at promoting corneal keratocytes proliferation, hence is a possible alternative material to generate synthetic keratoprosthetic skirts.

Apatite Deposition on NaOH‐Treated PEEK and UHMWPE Films for Sclera Materials in Artificial Cornea Implants

AbstractCornea implants consist of a clear optic portion with a surrounding ring known as the skirt, which needs to integrate with the sclera. However, currently used skirt materials lead to poor tissue integration. Improvements in this respect may be achieved by using a bioactive skirt material that adapts to the metabolic activity of the cornea. Polyether etherketone (PEEK) and ultra‐high molecular weight polyethylene (UHMWPE) might provide interesting alternatives, if they can be rendered bioactive. We, therefore, investigated the potential of surface‐modifying PEEK and UHMWPE films through the use of a two‐step treatment. This process involved a suitable chemical surface modification (via immersion in NaOH), with subsequent formation of apatite layers on the polymers' surfaces through exposure to supersaturated simulated body fluid (1.5 SBF). In the present work the effect of 5 and 10 M NaOH on formation of the apatite layer has been investigated with regard to wettability and topography features. In addition, the chemical stability of the apatite layer formed has been analyzed. Our data demonstrate that with an increase in NaOH concentration the wettability of the polymer increased, whilst some changes to the polymer film topography (increase/decrease in roughness) were observed. Most beneficially, the apatite layer that subsequently was grown on pre‐treated PEEK and UHMWPE films through immersion in 1.5 SBF contained phosphate and carbonate ions, in similar ratios to those found in the apatite in dentine, thus, promising good in vivo bioactivity of these polymer films—a necessity if they are to be integrated into artificial cornea.

The Effects of Surface Roughness and Coatings on the Tribological Behavior of the Surfaces of a Piston Skirt

Two methods are proposed to reduce friction losses and the amount of wear in a piston assembly. One is the modification of the surface roughness of the skirt. Surface coating is another method to protect the sliding surfaces. In order to study the roughness of the skirt surfaces, the surfaces were ground to have three different roughness values. Graphite and diamond-like carbon (DLC) were also used to coat the surfaces of the piston skirts, while the specimens used in the test were the skirt and the cylinder bores from a low-friction diesel engine. These were tested with a reciprocating wear tester that used a piece of cylinder block as the reciprocating specimen and a segment of the piston skirt material as the fixed pin. SAE5W40 engine oil was used in the boundary lubrication regime. The friction coefficient of the graphite coating was lower than the DLC coating, but the graphite coating was not effective in protecting the wearing of the surfaces. The DLC coating provided much better tribological performance than the graphite coating.

Synergeyes Versus Soft Toric Lenses: Vision-Related Quality of Life

The purpose of this study is to contrast the clinical and vision-related quality of life outcomes between Synergeyes, a hybrid contact lens, and Bausch & Lomb Soflens 66 Toric contact lenses in a cross-over design. Also, to determine subject preference of one mode of lens wear over the other. The Synergeyes lens has a central rigid gas permeable portion made of Paragon HDS100 material (paflufocon D) bonded to the nonionic hydrophilic skirt material of 27% water (PolyHEMA hem-iberfilcon A). The Soflens 66 Toric lens is made of a nonionic hydrophilic 66% water (alphafilcon A) material. Subjects age 18 years and older with spherical refractive error between -0.50 and -8.00 D and astigmatism correction of -0.75 to -3.50 D were randomly assigned to wear one mode of contact lens for 1 month then wear the alternate mode for 1 month. Follow-up visits were done at 1 and 4 weeks. Data gathered at these visits included high-contrast log MAR distance visual acuity, average wearing time, comfortable wearing time, over-refraction, and slit lamp observations for corneal edema, conjunctival hyperemia, and corneal staining. At each visit, subjects were asked to rate overall comfort, dryness, and comfortable wearing time. Subjects were asked to complete the NEI-RQL-42 questionnaire at the end of each lens wearing period. Upon completion of both lens wearing modes, subjects were asked to choose their preferred mode. Fifty subjects completed the study; 22 (44%) preferred the Synergeyes lenses, and 28 (56%) preferred the Soflens 66 Toric soft lenses. Measured visual acuity was significantly better with the Synergeyes lenses. Of the 13 attributes analyzed in the RQL-42, a statistically significant difference between the two modes was found in only one category, "symptoms." In that category, subjects indicated fewer symptoms when wearing soft lenses. The subjects' ratings also showed significantly more comfort while wearing the soft toric lenses. Bausch & Lomb Soflens 66 Toric lenses were more comfortable and were perceived to produce less symptoms of dryness, itchiness, and lens awareness than Synergeyes lenses. Synergeyes lenses gave better visual acuity than the soft toric lenses.

Design and fabrication of an artificial cornea based on a photolithographically patterned hydrogel construct

We describe the design and fabrication of an artificial cornea based on a photolithographically patterned hydrogel construct, and demonstrate the adhesion of corneal epithelial and fibroblast cells to its central and peripheral components, respectively. The design consists of a central "core" optical component and a peripheral tissue-integrable "skirt." The core is composed of a poly(ethylene glycol)/poly(acrylic acid) (PEG/PAA) double-network with high strength, high water content, and collagen type I tethered to its surface. Interpenetrating the periphery of the core is a microperforated, but resilient poly(hydroxyethyl acrylate) (PHEA) hydrogel skirt that is also surface-modified with collagen type I. The well-defined microperforations in the peripheral component were created by photolithography using a mask with radially arranged chrome discs. Surface modification of both the core and skirt elements was accomplished through the use of a photoreactive, heterobifunctional crosslinker. Primary corneal epithelial cells were cultured onto modified and unmodified PEG/PAA hydrogels to evaluate whether the central optic material could support epithelialization. Primary corneal fibroblasts were seeded onto the PHEA hydrogels to evaluate whether the peripheral skirt material could support the adhesion of corneal stromal cells. Cell growth in both cases was shown to be contingent on the covalent tethering of collagen. Successful demonstration of cell growth on the two engineered components was followed by fabrication of core-skirt constructs in which the central optic and peripheral skirt were synthesized in sequence and joined by an interpenetrating diffusion zone.

The importance of grasstrees (Xanthorrhoea preissii) as habitat for mardo (Antechinus flavipes leucogaster) during post-fire recovery

Grasstrees (Xanthorrhoea) are an important structural component of many Australian ecosystems and also an important resource for many fauna species. Grasstrees have distinctive morphologies, with a crown of long thin leaves and skirts, the latter of which are accumulated dead leaves; both are incinerated by fire. This study determined the morphological features of Xanthorrhoea preissii, which change in response to fire from 6 months to 21 years post-burn. In addition, using radio-telemetry and spool-tracking, we determined that grasstrees are utilised as foraging and nesting resources for mardos (Antechinus flavipes leucogaster (Gray, 1841), Marsupialia: Dasyuridae). Recently burnt grasstrees (6 months post-burn) appeared not to be used by mardos at all. We found few mardos in these recently burnt sites, and the one individual we managed to track for 126 m utilised only a single grasstree: a 2-m-tall multiple-crowned grasstree that had escaped the fire was used as a nest site. For sites 5 years post-burn, mardos selectively utilised grasstrees with larger crown areas and those with a greater number of crowns compared with a random sample of available trees. At the 14-year post-burn sites, mardos still demonstrated some selection for grasstrees, although no specific single feature could be determined as most significant. We recorded humidity and temperature buffering effects in association with post-burn accumulation of grasstree skirt material and found that even dead grasstree ‘logs’ were an important resource for nests. We conclude that mardos utilise both live and dead grasstrees for foraging and nest sites, possibly owing to the availability of dense cover, a buffered microclimate, and potentially also food resources. Fire-management policies that promote habitat heterogeneity and retain several intact-skirted grasstrees within the landscape are likely to benefit mardos.

Novel materials to enhance keratoprosthesis integration

BACKGROUNDThe successful integration of keratoprostheses (KPros) within the cornea depends in part on peripheral host keratocyte adhesion to anchor the implant in place and prevent epithelial downgrowth. The following study...

Cell viability and inflammatory response in hydrogel sponges implanted in the rabbit cornea

In the quest for the development of a functional keratoprosthesis, the biocompatibility of the porous skirt material in the Chirila keratoprosthesis (KPro) was investigated. The population of live and dead cells within, and the inflammatory response to, a tissue-integrating poly(2-hydroxyethyl methacrylate) (PHEMA) sponge were studied. Samples of the hydrogel sponge were implanted in rabbit corneas and explanted at predetermined time points up to 12 weeks. The explanted sponges were subjected to cell viability assay using two types of fluoroprobes, 5-chloromethylfluorescein diacetate and ethidium homodimer-1. A semiquantitative analysis was performed to assess the number of dead cells within the sponge and in the area of corneal stroma proximal to the sponge. Five rabbits were used for each end point (2, 4 and 12 weeks). To investigate the inflammatory response to the sponge, immunocytochemistry, using specific antibodies to rabbit macrophages, enzyme histochemistry of chloroacetate esterase (to detect neutrophils) and transmission electron microscopy (TEM) were also employed at 24 h, 2, 4 and 12 weeks after implantation. Four weeks after implantation, fewer viable cells were observed in the sponge when compared to the 2-week implant. However, the proportion of viable cells increased dramatically by 12 weeks. The proportion of nonviable cells decreased gradually with time; central sponge contained 34±11% dead cells after 2 weeks, and 15±4.3% after 12 weeks. The staining of inflammatory cells demonstrated the presence of macrophages and neutrophils up to 12 weeks after implantation. TEM confirmed the presence of these cell types and others, including eosinophils and myofibroblasts, as well as blood capillaries. The presence of a significant number of viable cells at each time point and the uniform reduction of the nonviable cell proportion with time suggests that the sponge is a conducive environment supporting a prolific, viable cellular colonization. Dead cells observed in the first instance indicate a normal injury pattern. However, the presence of a small but significant proportion of invading inflammatory cells 12 weeks after implantation confirms a characteristic pattern of wound healing within the sponges.

Winnie the Weaver

Winnie the Weaver Wilma P. Elkins Winnie Day Spring, summer, fall, or winter, no matter what the season, Winnie Day could be found at her loom weaving beautiful cloth for towels, coverlets, baby bibs, aprons, pillow tops, drapes, skirt material ... the list goes on. For more than seventy years, the rhythmic movement ofthe treadles to form the pattern, the sound of the shuttle as it pressed the threads together to form the cloth, could be heard from her home on Sam's Branch, a narrow valley in the beautiful hills of Knott County in southeastern Kentucky, where Winnie and her family have lived since 1921. Winnie Pigman was born on October 20, 1901, at Ivis, Kentucky, the seventh of ten children of Wilburn and Mary Belle Smith Pigman. Wilburn was a farmer and a teacher, Mary Belle a homemaker and weaver. She was taught how to weave by her mother, Susannah Hamilton. Allen H. Eaton, in Handicrafts ofthe Southern Highlands, lists Mary Pigman of Ivis, Kentucky, as one of the native weavers who gave indispensable help in the early days of the revival of handicrafts. The author, a Bereagraduate, is a retired teacher/educator now living in Lexington, Kentucky. She is a niece of Winnie Day. 39 Winnie followed in the footsteps ofher grandmother and mother and became a true artist in weaving. She was a quiet child who could often be found watching her mother work at her loom. Her formal education was at Jones Chapel and at Mallie, both small schools in Knott County. She enjoyed her school work and playing with her friends at school. At the end of the school day she helped with the chores, of which there were many for a large family living on a small farm. Also, she spent time at the loom learning to weave. By age ten, she had begun to help in the making of the woven products which were used at home as needed and were also sold to supplement the family income. Her loom was built for her by her brother, Dewitt Pigman. When Winnie was seventeen she went to Berea to develop more skills. Berea was then and remains today a center for handicrafts with emphasis on woven cloth products. At Berea she did weaving at Fireside Industries . (Years later, daughter Pauline attended Berea College and wove at Fireside Industries.) Her teacher was Anna Ernberg, a Swedish lady who was brought to Berea to revive the art of weaving and crafts at Berea College. Mrs. Ernberg marveled at the skill and talent Winnie displayed in her work. Not only was she an expert weaver, but she was adept at the preparation process: the carding of wool, the spinning, the dyeing (she often used natural products such as walnut hulls and sumac for making dyes), dressing the loom, and making the bobbins. She admits that she wasn't especially fond of the preparation process; her interest was in making the cloth. Later, the thread—woolen, cotton, or linen— could be bought commercially. Winnie could look at an object or a picture, then make a pattern to use in the designs. While at Berea, she came upon a picture of a pine tree which she thought would make a pretty design on her towels and scarves. She developed the pattern which became her signature on many pieces of her work. During her stay at Berea, the weaving was done at the Log Palace, later officially named the Log House, which Berea College still uses as sales rooms for Berea arts and crafts. Following her stay in Berea, Winnie Pigman returned to her home in Knott County, where she continued weaving along with her mother and her sister, Una, who later taught weaving for many years at the Hindman Settlement School. Lester Day and Winnie Pigman were married on April 9, 1921, and moved to the house on Sam's Branch; her loom moved with them. Along with the usual duties of a housewife and later the mother of four children—two sons, Astor and Sam, and two daughters, Pauline and Mary—she continued her weaving and marketed from her home, from 40 Hindman Settlement School, Caney Junior College...