Abstract: The sandfish (Scincidae: Scincus scincus) is a lizard having outstanding skin properties. The scales show low friction behaviour and high abrasion resistance. After giving molecular support by DNA and protein analysis in Part 1 for increased glycosylation of the skins β-keratins, in this study the effect of glycans for friction reduction was investigated by (1) ammonium-based keratinolysis of skin exuviae and applying a β-keratin film on a glass surface and by (2) β-elimination based deglycosylation of β-keratins and immobilization of liberated glycans on a glass surface via silanisation. Both techniques resemble the natural model in the species investigated, the sandfish Scincus scincus and the Berber skink Eumeces schneideri. In the sandfish, a decreased friction coefficient was found by friction angle measurements, and a low adhesion force was measured by investigation with atomic force microscopy (AFM). These characteristics are possibly based by prevention of the formation of van der Waals bonds. This low adhesion force correlates with low friction and has a positive impact on abrasion resistance. A monosaccharide analysis confirmed the presence of carbohydrates.
Abstract: Lightweight, high strength fibre-reinforced polymeric composites are leading materials in many advanced applications including biomedical components. These materials offer the feasibility to incorporate multi functionalities due to their internal architecture, heterogeneity of materials and the flexibility of combining them using currently available fabrication methods. In spite of the excellent properties of these materials, their failure is still a questionable and not well predicted event. Delamination, debonding and micro-cracks are only some of the failure mechanisms that affect the matrices of polymer based composites. More complex cases exist with the combination of multiple failure mechanisms. In such cases a self-repairing mechanism that can be auto-triggered in the matrix material once the crack has been formed, would be very beneficial for all the applications of these materials, reducing maintenance costs and increasing their safety and reliability. Self-healing materials have been studied for more than a decade by now, with the specific objective of reducing the risks and costs of cracking and damage in a wide range of materials. Different approaches have been taken to create such materials, depending on the kind of material that needs to be repaired. The most popular methods developed for polymers and polymer reinforced composites are considered in this review. These methods include materials with micro-capsules containing a healing agent, and composites with matrices that can self-heal the cracks by repairing the broken molecular links upon external heating. While the first approach to healing has been widely used and studied in the past decade, in this review we focus on the second approach since less is reported in the literature and more difficult is the development of the materials based on such a method.
Abstract: In the body, osteocytes reside in lacunae, lenticular shaped cavities within mineralized bone. These cells are linked to each other and surface-residing osteoblasts via physical channels known as gap junctions. It has been suggested that osteocytes sense mechanical load applied to bone and relay that signal to osteoclasts and osteoblasts. Current in vitro and in vivo models of mechanotransduction face temporal and spatial barriers. Recent advances in polydimethylsiloxane (PDMS) based microfabrication techniques may be able to overcome some of these hurdles. However, before the bone research field can effectively utilize microsystems techniques, fundamental groundwork must be completed. This study characterized the behaviour of osteocytes on PDMS coated with collagen type I (CTI) and provides the framework for bone cell mechanotransduction studies using microsystems. The goal was to determine whether osteocytes were adversely affected by the substrate material by comparing their behaviour to a standard glass substrate. In addition, optimal culture conditions and time points for growing osteocytes on PDMS substrates were determined. Results of this study suggested that use of PDMS does not adversely affect osteocyte behaviour. Furthermore, the results demonstrated that osteocytes should be cultured for no less than 72 hours prior to experimentation to allow the establishment and maintenance of phenotypic characteristics. These results completed essential groundwork necessary for further studies regarding osteocytes in microsystems modelling utilizing PDMS.
Abstract: A new reinforcement distribution design method inspired by venation configuration is discussed in the paper. Learned from dicotyledonous venation, venation growing algorithm is proposed, minimization of strain energy and shear stress determine growth direction of the mainveins and subveins respectively. Vectorial equilibrium equation is used to calculate vein widths and adjust the orientation of vein cells slightly. Sensitivity number is used to measure the change in strain energy and shear stress when a vein cell grows, necessary equations are derived for bending Kirchhoffs plate. Several examples are design for venation-like rib distribution. The resultant rib layout by VGA is applicable and effective.
Abstract: Recently, magnesium (Mg) alloys have inspired a significant amount of attention from researchers all over the world for implant applications due to their light weight, mechanical integrity and degradation behaviour. The major concerns with Mg implants are its rapid and non-uniform degradation, which can increase the risk of leached ions and can cause premature failure. In this study, Mg based alloys/metal matrix composites (MgZnCa/HA) were mechanically and electrochemically (anodized) surface treated. In-vitro corrosion tests revealed that the addition of hydroxyapatite (HA) and anodizing, stabilizes the corrosion process and lowers hydrogen evolution. Evidence of reduced degradation was provided by the presence of a relatively smooth surface morphology after corrosion. Furthermore, exposure of leached ions on osteoblast cells indicated good cytocompatibility.
Abstract: In this study, the starch/polystyrene (PS) biopolymer blend is prepared by utilizing an in solution polymerization process. Two different ratios (50/50 and 80/20) of starch/PS were dissolved in toluene associated with mechanical mixing to maintain the homogeneity of the blend. Thereafter, the blend was exposed to γ-radiation using Cobalt 60 (Co60) at different dosing rates. The thermal and chemical properties were investigated by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), enzymatic degradation, and disclosure of starch by iodine, respectively. The deviation of glass transition temperature (Tg ( and the IR peaks indicate that a good interaction between starch and polystyrene was achieved in the blend. Exposure of the starch/PS blend to the α-amylase enzyme and to iodine demonstrated that the γ-rays have affected the amylopectin part with no distinct effect on the amylose part of the starch. Moreover, the colour has completely disappeared at 100 kGray irradiation dose since the blend becomes more responsive to enzymatic degradation at higher irradiation dose, which in turn causes in breaking down of the amylose part in the starch.
Abstract: Knee meniscal injuries account for the greatest number of surgical procedures performed by orthopaedic surgeons worldwide. Each year in excess of 400,000 operations are performed in Europe and over one million in the United States and yet no suitable replacement for the meniscus is available. Fibrocartilage tissue engineering holds great potential in the regeneration of meniscal tissue however current developments have been limited. Difficulties in imitating the anisotropic nature of the meniscus, patient specific geometry, attaining sterility assurance requirements remain as developmental challenges for meniscal scaffold devices. A novel approach was developed to rapidly form terminally sterilized pre-packaged scaffold templates into anatomically matched regenerative meniscal implants. Formed meniscal implants exhibited the structural and functional architecture of the native meniscus. Meniscal implants fabricated using this method displayed mechanical properties approaching to that of the native meniscus and imparted rotational stability. Fixation techniques influenced the biomechanical response of implants and 45S5 bioactive glass modification was found to enhance radio-opacity of the scaffold. Biocompatibility of the implant was confirmed using a fibroblast cell culture model.
Abstract: The antimicrobial efficacy of polyethylene (PE) with organic antibacterial agent and inorganic antibacterial agent were evaluated in this work. Moreover, inhibition to bacterial biofilm on their surfaces was investigated in detail. Our experimental results showed that both modified PE samples exhibited excellent antimicrobial performances against S. aureus and E. coli with low cell suspension. When cell suspension increased up to109 cell/ml, a large amount of bacteria (S. aureus and E. coli) and extracellular polysaccharide matrix adhered to the untreated PE and PE with inorganic antibacterial agent. On the other hand, adhesion, colonization and biofilm of S. aureus did not occur on PE with organic antibacterial agent, and a little E. coli survived on its surface. It was demonstrated that organic antibacterial agent had better ability to inhibit bacteria propagation than the inorganic one in initial time, and thus it prevented adherent bacteria to develop biofilm on the surface. The difference was derived from different initial effect time of them against bacteria. Therefore, it was a better approach to prevent catheter-related infections through addition of organic reagent into bulk material.