Raney-platinum film electrodes for potentially implantable glucose fuel cells. Part 1: Nickel-free glucose oxidation anodes

We present a novel fabrication route yielding Raney-platinum film electrodes intended as glucose oxidation anodes for potentially implantable fuel cells. Fabrication roots on thermal alloying of an extractable metal with bulk platinum at 200 °C for 48 h. In contrast to earlier works using carcinogenic nickel, we employ zinc as potentially biocompatible alloying partner. Microstructure analysis indicates that after removal of extractable zinc the porous Raney-platinum film (roughness factor ∼2700) consists predominantly of the Pt₃Zn phase. Release of zinc during electrode operation can be expected to have no significant effect on physiological normal levels in blood and serum, which promises good biocompatibility. In contrast to previous anodes based on hydrogel-bound catalyst particles the novel anodes exhibit excellent resistance against hydrolytic and oxidative attack. Furthermore, they exhibit significantly lower polarization with up to approximately 100 mV more negative electrode potentials in the current density range relevant for fuel cell operation. The anodes’ amenability to surface modification with protective polymers is demonstrated by the exemplary application of an approximately 300 nm thin Nafion coating. This had only a marginal effect on the anode long-term stability and amino acid tolerance. While in physiological glucose solution after approximately 100 h of operation gradually increasing performance degradation occurs, rapid electrode polarization within 24 h is observed in artificial tissue fluid. Optimization approaches may include catalyst enhancement by adatom surface modification and the application of specifically designed protective polymers with controlled charge and mesh size.     

Biomechanics and histology of bovine claw suspensory tissue in early acute laminitis

Weakening of the suspensory tissue supporting the pedal bone is the central issue in the theory of acute bovine laminitis, but this aspect has never been tested. The objective of this study was to investigate the effect of laminitis on the suspensory tissue. The hypothesis was that clinical and histological signs of acute laminitis are associated with decreased strength of the suspensory tissue of the bovine claw. Nonpregnant dairy heifers (n = 10) received oral oligofructose overload (17 g/kg of body weight) and were killed 24 (n = 4) and 72 h (n = 6) after overload. Control heifers (n = 6) received tap water and were killed at 72 or 96 h. Clinical, orthopedic, and histological examinations were carried out to confirm the occurrence of laminitis. After euthanasia, 2 adjacent tissue samples including the horn wall, lamellar layer, dermis, and pedal bone were cut from the dorso-abaxial aspect of each claw. Tissue samples were kept on ice until mounted on a mechanical testing frame, fixed by horn and bone, and loaded to failure. A stress displacement curve was generated and measurements of physiological support (force needed to displace 1 mm beyond first resistance) and maximal support (force needed to break the tissue) were recorded. Heifers treated with oligofructose developed clinical signs consistent with ruminal and systemic acidosis after treatment as well as acute laminitis, characterized by weight shifting (35% of observations vs. 6% in controls), moderate lameness (100 vs. 17%, score of 3 out of 5 at 72 h), and reaction to hoof testing (30 and 50% at 48 and 72 h, respectively, vs. 0% in controls). Histological examination of claws from heifers killed 72 h after overload showed changes consistent with acute laminitis, including stretched lamellae, wider basal cells with low chromatin density, and a thick, wavy, and blurry appearance of the basement membrane. Biomechanical results showed no effect of oligofructose overload on physiological support of the suspensory tissue at 24 and 72 h after overload; in contrast, overload increased maximal support of the tissue 72 h after overload. Herd of origin and location of the sample had large effects on both physiological support and maximal support (herd = 547 N/cm²; location = 531 N/cm²) of claw suspensory tissue (herd = 260 N/cm²; location = 327 N/cm²). Despite clinical and histological signs of laminitis, no weakening of the suspensory tissue of the bovine claw was detected at 24 and 72 h after oligofructose overload. Herd factors appeared to be important for claw suspensory tissue strength.     

Osteogenic differentiation and mineralization in fibre-reinforced tubular scaffolds: theoretical study and experimental evidences

The development of composite scaffolds with well-organized architecture and multi-scale properties (i.e. porosity, degradation) represents a valid approach for achieving a tissue-engineered construct capable of reproducing the medium- and long-term in vitro behaviour of hierarchically complex tissues such as spongy bone. To date, the implementation of scaffold design strategies able to summarize optimal scaffold architecture as well as intrinsic mechanical, chemical and fluid transport properties still remains a challenging issue. In this study, poly ɛ-caprolactone/polylactid acid (PCL/PLA) tubular devices (fibres of PLA in a PCL matrix) obtained by phase inversion/salt leaching and filament winding techniques were proposed as cell instructive scaffold for bone osteogenesis. Continuous fibres embedded in the polymeric matrix drastically improved the mechanical response as confirmed by compression elastic moduli, which vary from 0.214 ± 0.065 to 1.174 ± 0.143 MPa depending on the relative fibre/matrix and polymer/solvent ratios. Moreover, computational fluid dynamic simulations demonstrated the ability of composite structure to transfer hydrodynamic forces during in vitro culture, thus indicating the optimal flow rate conditions that, case by case, enables specific cellular events—i.e. osteoblast differentiation from human mesenchymal stem cells (hMSCs), mineralization, etc. Hence, we demonstrate that the hMSC differentiation preferentially occurs in the case of higher perfusion rates—over 0.05 ml min^–1—as confirmed by the expression of alkaline phosphate and osteocalcin markers. In particular, the highest osteopontin values and a massive mineral phase precipitation of bone-like phases detected in the case of intermediate flow rates (i.e. 0.05 ml min^–1) allows us to identify the best condition to stimulate the bone extracellular matrix in-growth, in agreement with the hydrodynamic model prediction. All these results concur to prove the succesful use of tubular composite as temporary device for long bone treatment.     

The biological seal of the implant–soft tissue interface evaluated in a tissue-engineered oral mucosal model

For dental implants, it is vital that an initial soft tissue seal is achieved as this helps to stabilize and preserve the peri-implant tissues during the restorative stages following placement. The study of the implant–soft tissue interface is usually undertaken in animal models. We have developed an in vitro three-dimensional tissue-engineered oral mucosal model (3D OMM), which lends itself to the study of the implant–soft tissue interface as it has been shown that cells from the three-dimensional OMM attach onto titanium (Ti) surfaces forming a biological seal (BS). This study compares the quality of the BS achieved using the three-dimensional OMM for four types of Ti surfaces: polished, machined, sandblasted and anodized (TiUnite). The BS was evaluated quantitatively by permeability and cell attachment tests. Tritiated water (HTO) was used as the tracing agent for the permeability test. At the end of the permeability test, the Ti discs were removed from the three-dimensional OMM and an Alamar Blue assay was used for the measurement of residual cells attached to the Ti discs. The penetration of the HTO through the BS for the four types of Ti surfaces was not significantly different, and there was no significant difference in the viability of residual cells that attached to the Ti surfaces. The BS of the tissue-engineered oral mucosa around the four types of Ti surface topographies was not significantly different.     

Bioengineering of Dental Pulp Stem Cells in a Microporous PNIPAAm-PLGA Scaffold

In the present article a novel bio absorbable polymeric scaffold using poly(N-isopropyl acrylamide-block-poly(L-lactide-co-glycolide) (PNIPAAm-b-PLGA) copolymers is developed for in vitro culture of human dental pulp stem cells (DPSCs). The processing of porous scaffolds has been carried out by emulsion freeze-drying and salt leaching out methods. DPSCs were cultured on scaffolds for up to 14 days. The morphology of the scaffolds, cell viability and interaction between DPSCs and scaffold was characterized by using SEM. The results of cells implantation indicated that scaffold has good cell biocompatibility. Therefore PNIPAAm-PLGA scaffolds have great potential to be used as cell carrier in tissue engineering.     

L’adaptation parentale à la venue d’un nouvel enfant: Perspectives et prospectives.

Pregnancy and the birth of a child imply personal changes that require many individual, marital, and family adaptations (Mercer et al., 1988). The outcome of this transition will have implications for the welfare of the whole family. The area of research studying this type of adaptation has witnessed much theoretical and methodological progress in the last 10 years. Contemporary researchers are trying to identify the factors associated with this adaptation process (Gable et al., 1992). A more detailed conceptual model of parental and family adaptation is now starting to take form (Terry, 1991b). The recent proliferation of research on parental adjustment to the birth of a child justifies a review of recent studies in this area. What are the limits of the investigations in this area of interest? What modifications could be suggested to strengthen its empirical basis? What are the implications of a family perspective of parental transition? To answer these questions a review of the literature in this area will be presented. The theoretical, methodological, and clinical implications of a systemic perspective on parental adjustment will then be discussed. This paper will also highlight a number of methodological limits of recent studies and suggest recommendations for future research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Experiences of Using Generative Communications to Support Adaptive Mobile Applications

Attention has recently begun to focus on the use of asynchronous paradigms to support adaptive mobile applications. To investigate this issue the authors have developed an asynchronous distributed systems platform based on the tuple space paradigm [19] coupled with extensions to support operation in mobile environments. This paper presents our experiences of developing and using this platform. The benefits of the tuple space approach are highlighted and we discuss in some detail the design, implementation and performance of our platform. We subsequently focus on the critical issues of the tuple space API and the level of support for adaptation which can be provided without compromising the elegance and simplicity of the paradigm. The paper concludes with an analysis of the suitability of platforms based on the tuple space paradigm for use in mobile environments.