Lian J.,Leather and Shoe Research Association of New Zealand |
Lian J.,Massey University |
Mansel B.W.,Massey University |
Ingham B.,MacDiarmid Institute for Advanced Materials and Nanotechnology |
And 5 more authors.
Soft Materials | Year: 2017
The structure, mechanical properties, and optical density of gels prepared from collagen in a manner that induces the dynamical arrest of the constituent polymers before substantial fibrillogenesis can take place have been investigated. Small angle X-ray scattering and confocal laser scanning fluorescence microscopy reveal that these gels exhibit substantially different network structures, over length scales ranging from a few nanometers to many microns, when compared with traditional collagen networks in which fibrillogenesis is intentionally induced. The highly associated arrangements of the more flexible structural components found in the arrested network yield a considerably lower optical density and higher viscoelastic storage modulus when compared to a “conventional” collagen gel; while the small amount of fibrils that do manage to form still yield strain stiffening and account for the fact that at high strains, moduli from both systems fall onto the same master curve. © 2017 Taylor & Francis
Prabakar S.,Leather and Shoe Research Association of New Zealand |
Whitby C.P.,Massey University |
Henning A.M.,Boutiq Science Ltd. |
Holmes G.,Leather and Shoe Research Association of New Zealand
Journal of the American Leather Chemists Association | Year: 2016
Looseness describes a structural fault in leather, which leads to the development of wrinkles on the surface when the leather is bent inwards. It causes up to 7% of hides processed to finished leather to be downgraded or rejected at final inspection, requiring replacement and causing delay in meeting orders. Fillers can fill the interstitial spaces in loose leathers and make the looseness less pronounced. Here, the effect of Cloisite®Na+, a nanoclay filler, on loose cattle hides is investigated by electron microscopy and mechanical characterization. Whilst SEM studies show an apparent filling effect in the grain-corium boundary at increasing concentrations of filler, TEM images show that at an optimum concentration of 3% uniform dispersion of the filler along with good handle can be obtained. A gradual increase in tensile and tear strength is observed with increasing concentration of Cloisite® Na+, however softness measurements correlated with microscopic observations in that only at optimum concentrations can both good handle and mechanical strength be achieved. We discuss a possible mechanism for the change in mechanical properties and handle of the loose leather after treating with Cloisite®Na+. The mechanistic study of such treatments on low quality hides will result in the production of leathers with more uniform cutting area and added functionality. © 2016, American Leather Chemists Association. All rights reserved.
Harland D.P.,Agresearch Ltd. |
Caldwell J.P.,Environment Waikato |
Woods J.L.,Agresearch Ltd. |
Walls R.J.,Agresearch Ltd. |
Bryson W.G.,Leather and Shoe Research Association of New Zealand
Journal of Structural Biology | Year: 2011
Tomograms of transverse sections of Merino wool fibers obtained from fleeces differing in fiber curvature were reconstructed from image series collected using a 300. kV transmission electron microscope. Trichokeratin intermediate filaments (IFs) from the ortho-, para- and mesocortices were modeled from the tomograms. IFs were predominantly arranged in left-handed concentric helices with the relative angle of IFs increasing progressively from the center to the periphery of orthocortex macrofibrils. The median increase in IF angle between adjacent IFs between the center and periphery was 2.5°. The length of one turn of the helical path of an IF was calculated to be approximately 1μm for an IF tilted at 30° and positioned 100. nm from the macrofibril center. With the exception of one paracortex macrofibril that weakly resembled an orthocortex macrofibril, all para- and mesocortex macrofibrils modeled had a parallel arrangement of the IFs, with a more ordered arrangement found in the mesocortex. Within the limited sample set, there appeared to be no significant relationship between IF angle and fiber curvature. We examined the matrix/IF ratio (in the form of proportion of matrix to one IF, calculated from IF center-to-center distance and IF diameter) for 28 macrofibrils used for modeling. The proportion of matrix was significantly different in the different cortex cell types, with paracortex having the most (0.61), orthocortex having the least (0.42), and mesocortex being intermediate (0.54). Fibers of different crimp type (high, medium or low crimp) were not significantly different from each other with respect to matrix proportion. © 2010 Elsevier Inc.
Lian J.,Leather and Shoe Research Association of New Zealand |
Lian J.,Massey University |
Lian J.,MacDiarmid Institute for Advanced Materials and Nanotechnology |
Agban Y.,University of Auckland |
And 13 more authors.
European Polymer Journal | Year: 2016
Collagen based hydrogels have similar properties to native cornea and play an important role in ocular drug delivery. Here we report the preparation of zinc oxide nanoparticle/collagen hydrogels (collagen ZnO/PVP) without the need of an external cross-linking agent. The resulting hydrogels had sufficient mechanical strength to be manipulated and transferred without damaging its structure. Differential scanning calorimetry showed an increase in the denaturation temperature on increasing the ZnO/PVP NPs ratio. Whilst rheological measurements of the collagen hydrogels suggest that strong hydrogels were formed, at high concentration of ZnO/PVP NPs a decrease in G′ can be observed. The responses of retinal epithelial cells (ARPE-19) to the collagen ZnO/PVP hydrogels were examined by cell viability assays and exhibited minimal cytotoxicity. The collagen ZnO/PVP hydrogel might be an excellent candidate for ocular drug delivery applications. © 2016 Elsevier Ltd. All rights reserved.
Sizeland K.H.,Massey University |
Basil-Jones M.M.,Massey University |
Edmonds R.L.,Leather and Shoe Research Association of New Zealand |
Cooper S.M.,Leather and Shoe Research Association of New Zealand |
And 3 more authors.
Journal of Agricultural and Food Chemistry | Year: 2013
Collagen is the main structural component of leather, skin, and some other applications such as medical scaffolds. All of these materials have a mechanical function, so the manner in which collagen provides them with their strength is of fundamental importance and was investigated here. This study shows that the tear strength of leather across seven species of mammals depends on the degree to which collagen fibrils are aligned in the plane of the tissue. Tear-resistant material has the fibrils contained within parallel planes with little crossover between the top and bottom surfaces. The fibril orientation is observed using small-angle X-ray scattering in leather, produced from skin, with tear strengths (normalized for thickness) of 20-110 N/mm. The orientation index, 0.420-0.633, is linearly related to tear strength such that greater alignment within the plane of the tissue results in stronger material. The statistical confidence and diversity of animals suggest that this is a fundamental determinant of strength in tissue. This insight is valuable in understanding the performance of leather and skin in biological and industrial applications. © 2013 American Chemical Society.
PubMed | National Synchrotron Radiation Research Center, Massey University, Leather and Shoe Research Association of New Zealand and Australian Synchrotron
Type: | Journal: Journal of the science of food and agriculture | Year: 2016
Some bovine hides produce poor quality leather, termed loose leather. The structural characteristics of hides and the intermediate processed stages that lead to loose leather are not well understood. In the present study, synchrotron-based small angle X-ray scattering (SAXS) is used to investigate collagen fibril orientation at the different stages of processing (i.e. from hide through to leather) that result in both tight and loose leathers.Tight leather of a relatively isotropic texture has a lower orientation index (OI) than loose leather of a more pronounced stratified texture; conversely, tight pickled hide and wet blue have a higher OI than loose pickled hide and wet blue. There is a greater increase in OI on processing from pickled hide to dry crust (leather) for loose material. This is largely the result of a greater increase in hide thickness prior to pickling for loose hide than tight hide, followed by a greater decrease at the dry crust stage. The collagen fibrils in loose leather and wet blue more readily orient under stress than do those in tight leather. Loose leather has a more pronounced layered structure than tight leather, although this difference is not apparent from SAXS measurements of hide prior to the dry crust stage; it develops during processing.The greater swelling of the loose hide during processing disrupts the structure and leads to a more layered collagen arrangement on shrinking at the final dry crust stage. 2016 Society of Chemical Industry.
PubMed | Massey University, Leather and Shoe Research Association of New Zealand and Australian Synchrotron
Type: | Journal: Journal of the science of food and agriculture | Year: 2017
Deer leather has a characteristic pattern, referred to as pebble, that is accorded such importance that a lack of it renders a leather defective. Synchrotron-based small angle X-ray scattering (SAXS), ultrasonic imaging, scanning electron microscopy, and tear tests are used to investigate the structural characteristics of well pebbled and poorly pebbled cervine leathers.Poorly pebbled leather has a less open structure in the upper grain region than well pebbled leather. The orientation index (OI) of leather with a poor pebble is less than that of the well pebbled leather, particularly in the corium. The tear strength is also less for the poorly pebble leather.The differences in structure between well and poorly pebbled cervine leathers are not the same as the structural differences between tight and loose bovine leathers, to which they are sometimes compared. On the contrary, good pebble may reflect an internal structure similar to that of looseness. It is hoped that methods to prevent a reduction in pebbling during the processing of cervine leather may be developed by applying this knowledge of cervine leathers structural characteristics.
PubMed | University of Auckland and Leather and Shoe Research Association of New Zealand
Type: Journal Article | Journal: International journal of pharmaceutics | Year: 2016
Glaucoma is a common progressive eye disorder which remains the second leading cause of blindness worldwide. Current therapy involves frequent administration of eye drops which often results in poor patient adherence and therapeutic outcomes. The aim of this study was to overcome these limitations by developing a novel nanoparticle cross-linked collagen shield for sustained delivery of pilocarpine hydrochloride (PHCl). Three metal oxide nanoparticles (NPs); titanium dioxide (TiO2), zinc oxide (ZnO) and polyvinylpyrrolidone (PVP) capped zinc oxide (ZnO/PVP), were evaluated for their cytotoxicity as well as shield transparency before selecting ZnO/PVP NPs as the ideal candidate. Cross-linked collagen shields were then characterized for their mechanical strength, swelling capacity and bioadhesive properties, with ZnO/PVP NP cross-linked shields showing the most favorable characteristics compared to plain films. The shield with the best properties was then loaded with PHCl and in vitro release of zinc ions as well as PHCl was measured without and with further cross-linking by ultraviolet irradiation. The concentration of zinc ions released was well below the IC50 rendering them safe for ocular use. Moreover, collagen shields cross-linked with ZnO/PVP NPs released PHCl over a period of 14 days offering a promising sustained release treatment option for glaucoma.
PubMed | Massey University and Leather and Shoe Research Association of New Zealand
Type: Journal Article | Journal: Journal of the science of food and agriculture | Year: 2016
A substantial proportion of bovine leather production may be of poor quality, with the leather suffering from a characteristic known as looseness. This defect results in a poor visual appearance and greatly reduced value. The structural mechanism of looseness is not well understood.Samples of loose and tight bovine leather are characterized using small-angle X-ray scattering, ultrasonic imaging, and electron microscopy. The density of fibre packing and orientation of the fibrils are analysed. Tensile strength is also measured. Loose leather is characterized by more highly aligned collagen fibrils. This results in a weaker connection between the layers. There is a looser packing of the fibres in loose leather than in tight leather, with more gaps between fibre bundles, particularly in a region in the lower grain. This region is visible with in situ ultrasonic imaging. Loose leather has a higher tensile strength than tight leather.While a high degree of collagen fibril alignment is normally associated with strong leather, it has been shown that too much alignment results in loose leather. Understanding the physical basis of looseness is the first step in identifying looseness in hides and learning how to prevent looseness from developing during leather manufacture. 2015 Society of Chemical Industry.