Biomedical Materials Research Research Articles

A new photocrosslinkable polycaprolactone-based ink for three-dimensional inkjet printing.

A new type of photocrosslinkable polycaprolactone (PCL) based ink that is suitable for three-dimensional (3D) inkjet printing has been developed. Photocrosslinkable Polycaprolactone dimethylacrylate (PCLDMA) was synthesized and mixed with poly(ethylene glycol) diacrylate (PEGDA) to prepare an ink with a suitable viscosity for inkjet printing. The ink performance under different printing environments, initiator concentrations, and post processes was studied. This showed that a nitrogen atmosphere during printing was beneficial for curing and material property optimization, as well as improving the quality of structures produced. A simple structure, built in the z-direction, demonstrated the potential for this material for the production of 3D printed objects. Cell tests were carried out to investigate the biocompatibility of the developed ink. © 2016 The Authors Journal of Biomedical Materials Research Part B: Applied Biomaterials Published by Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1645-1657, 2017.

Wear of composite ceramics in mixed-material combinations in total hip replacement under adverse edge loading conditions.

Ceramic composites have performed very well under adverse edge loading conditions when used in like‐on‐like configurations, where the femoral head and acetabular cup are of the same material. The aim of this study was to determine the wear of pure alumina (Al2O3), alumina toughened zirconia (ATZ) and zirconia toughened alumina (ZTA) when used in mixed bearing combinations, under edge loading conditions due to translational mal‐positioning. The head‐on‐cup configurations of three ceramic materials were ATZ‐on‐ZTA, ZTA‐on‐ATZ, Al2O3‐on‐ATZ, ATZ‐on‐Al2O3, Al2O3‐on‐ZTA, and ZTA‐on‐Al2O3. They were tested on the Leeds II hip simulator under microseparation conditions. The bedding in and steady state wear rates of ATZ‐on‐ZTA were 1.16mm3/million cycles and 0.18mm3/million, respectively, and for ATZ‐on‐Al2O3 were 0.66 mm3/million cycles and 0.20 mm3/million, respectively. The wear rates of the other bearing combinations under these adverse microseparation conditions, Al2O3‐on‐ATZ, Al2O3‐on‐ZTA, ZTA‐on‐ATZ and ZTA‐on‐Al2O3 were very low with no clear bedding in and steady state phases, and with steady state wear rates lower than 0.11 mm3/million. The mixed material combinations tested in this study have shown slightly higher wear rates when compared to ATZ in like‐on‐like configuration reported previously, but superior wear resistance when compared to alumina‐on‐alumina bearings tested previously under the same adverse microseparation conditions. © 2016 The Authors Journal of Biomedical Materials Research Part B: Applied Biomaterials Published by Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1361–1368, 2017.

Autocrine fibronectin from differentiating mesenchymal stem cells induces the neurite elongation in vitro and promotes nerve fiber regeneration in transected spinal cord injury.

Extracellular matrix (ECM) expression is temporally and spatially regulated during the development of stem cells. We reported previously that fibronectin (FN) secreted by bone marrow mesenchymal stem cells (MSCs) was deposited on the surface of gelatin sponge (GS) soon after culture. In this study, we aimed to assess the function of accumulated FN on neuronal differentiating MSCs as induced by Schwann cells (SCs) in three dimensional transwell co‐culture system. The expression pattern and amount of FN of differentiating MSCs was examined by immunofluorescence, Western blot and immunoelectron microscopy. The results showed that FN accumulated inside GS scaffold, although its mRNA expression in MSCs was progressively decreased during neural induction. MSC‐derived neuron‐like cells showed spindle‐shaped cell body and long extending processes on FN‐decorated scaffold surface. However, after blocking of FN function by application of monoclonal antibodies, neuron‐like cells showed flattened cell body with short and thick neurites, together with decreased expression of integrin β1. In vivo transplantation study revealed that autocrine FN significantly facilitated endogenous nerve fiber regeneration in spinal cord transection model. Taken together, the present results showed that FN secreted by MSCs in the early stage accumulated on the GS scaffold and promoted the neurite elongation of neuronal differentiating MSCs as well as nerve fiber regeneration after spinal cord injury. This suggests that autocrine FN has a dynamic influence on MSCs in a three dimensional culture system and its potential application for treatment of traumatic spinal cord injury. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1902–1911, 2016.

Silicon Mesostructures for Phospholipid Based Bioelectric Device and Deterministic Neuromodulation

Silicon is a widely used material in biomedical research because it is biocompatible and biodegradable, and it exhibits a spectrum of important electrical, optical, thermal and mechanical properties. However, the fundamental forms of silicon building blocks for biophysical and biomedical applications are few, and to date, researchers have focused primarily on crystalline and rigid structures. Natural biomaterials have remarkable diversity in structure and function and may guide the design of new silicon forms for subcellular interfaces and biophysical modulation. Nevertheless, reproducing heterogeneous features in silicon is difficult to achieve due to limited chemical or engineering processes. Here we introduce a multiscale, injectable, and ultra-soft silicon-based biomaterial with ‘brick-and-mortar’ mesostructures. It has an amorphous atomic structure, an ordered nanowire-based framework, and random micron-scale voids, exhibiting a high surface area and pore volume. Atom probe tomography (APT) and energy dispersive X-ray (EDX) mapping reveal an ordered and size-dependent oxygen distribution. The amorphous silicon-based mesostructures show reduced Young's moduli in air and in a buffered phosphate saline solution (2-3 orders of magnitude smaller than that of single crystalline silicon). Additionally, because the soft mesostructures exhibit a controllable photothermal effect in saline, we were able to design a remotely controlled bioelectric device by interfacing silicon particles with painted phospholipid bilayers, where the photothermal effect quickly changes the membrane capacitance, producing currents which are proportional to the time derivative of the temperature. By adding these silicon particles to dorsal root ganglion neurons we could reliably generate action potentials upon illumination with short pulses of 523 nm light. These results show that the mesostructured silicon particles permit non-genetic, fast, low power and sub-cellular optical control of electrophysiological activity. Supported by NIH: GM030376; AFOSR: FA9550-14-1-0175, FA9550-15-1-0285.

Dextran sulfate as a drug delivery platform for drug-coated balloons: Preparation, characterization, in vitro drug elution, and smooth muscle cell response.

Drug‐coated balloons (DCBs) have now emerged as a promising approach to treat peripheral artery disease. However, a significant amount of drug from the balloon surface is lost during balloon tracking and results in delivering only a subtherapeutic dose of drug at the diseased site. Hence, in this study, the use of dextran sulfate (DS) polymer was investigated as a platform to control the drug release from balloons. An antiproliferative drug, paclitaxel (PAT), was incorporated into DS films (PAT‐DS). The characterizations using SEM, FT‐IR, and DSC showed that the films prepared were smooth and homogenous with PAT molecularly dispersed in the bulk of DS matrix in amorphous form. An investigation on the interaction of smooth muscle cells (SMCs) with control‐DS and PAT‐DS films showed that both films inhibited SMC growth, with a superior inhibitory effect observed for PAT‐DS films. PAT‐DS coatings were then produced on balloon catheters. The integrity of coatings was well‐maintained when the balloons were either deflated or inflated. In this study, up to 2.2 µg/mm2 of PAT was loaded on the balloons using the DS platform. Drug elution studies showed that only 10 to 20% of the total PAT loaded was released from the PAT‐DS coated balloons during the typical time period of balloon tracking (1 min) and then ∼80% of the total PAT loaded was released during the typical time period of balloon inflation and treatment (from 1 min to 4 min). Thus, this study demonstrated the use of DS as a platform to control drug delivery from balloons. © 2015 The Authors Journal of Biomedical Materials Research Part B: Applied Biomaterials Published by Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1416–1430, 2016.

Electroassisted Assembly of Alkylphosphonic Acids Monolayers on Nitinol

Nitinol alloys have been widely studied as biomaterials for medical implants since they have very interesting mechanical properties, such as shape memory effect and superelasticity as well as a relatively good biocompatibility 1. The biocompatibility of Nitinol implants obviously depends on their surface properties, their corrosion resistance but also on the release of Ni ions after implantation, this chemical element being known to be allergenic and toxic, though essential for the human body. This problematic being of crucial importance for Nitinol biomedical applications, numerous works have been published on the study of Ni release from Nitinol 2-4 and its corrosion resistance compared to other commonly used alloys 5-11. Among the numerous ways explored to tune Nitinol surface properties and improve its corrosion resistance, the formation of alkylphosphonic acids self-assembled monolayers (SAMs) is versatile and attractive approach. SAMs are typically formed using a passive adsorption method by exposing the surface either to a surfactant solution or its vapors for relatively long periods of time. Recently, electroassisted adsorption of surfactant molecules started to be investigated. With this approach, high-quality organothiol SAMs have been generated in much shorter periods of time on gold 12-14 as well as on oxidizable metals and alloys such as nickel 15, carbon steel 16 and copper 17,18. More recently, Metoki et al. have investigated the electroassisted formation of organophosphonic SAMs on titanium alloy surfaces 19. They showed that this grafting method significantly reduces the time formation of the SAMs. This is attributed to the combined effects of oriented amphiphiles in the vicinity of the electrode, increased surface energy and underpotential oxide structure. In the present work, we investigate and compare the passive (adsorption) and active (electroassisted) grafting of alkylphosphonic acids SAMs on mechanically polished Nitinol surfaces. The effects of the applied potential and modification time on the monolayers and their properties are assessed by X-ray photoelectron spectroscopy, polarization modulation infrared reflection absorption spectroscopy, contact angle measurements, cyclic voltammetry and polarization curves measurements. It is shown that electroassisted method leads to a strong increase of the grafting kinetics compared to the passive method while preserving a low Ni surface concentration which is a key parameter for biomedical applications of Nitinol. Increasing the applied potential appears to improve the quality of the obtained SAMs while time has little influence, especially for grafting at low potential values. References T. Duerig, A. Pelton, and D. Stöckel, Materials Science and Engineering A, 273-275, 149 (1999).F.X. Gil, J.M. Manero, and J.A. Planell, Journal of Material Science: Materials in Medicine, 7, 403 (1996).S.A. Esenwein, D. Bogdanski, T. Habijan, M. Pohl, M. Epple, G. Muhr, and M. Köller, Materials Science and Engineering A, 481-482, 612 (2008).S.A. Shabalovskaya, H. Tian, J.W. Anderegg, D.U. Schryvers, W.U. Carroll, and J. Van Humbeeck, Biomaterials, 30, 468 (2009).G. Rondelli, Biomaterials, 17, 2003 (1996).M. Es-Souni, M. Es-Souni, and H. Fischer-Brandies, Biomaterials, 23, 2887 (2002).P. Rocher, L. El Medawar, J.-C. Hornez, M. Traisnel, J. Breme, and H.F. Hildebrand, Scripta Materialia, 50, 255 (2004).A. Schulte, S. Belger, M. Etienne, and W. Schuhmann, Materials Science and Engineering A, 378, 523 (2004).B. Clarke, W. Carroll, Y. Rochev, M. Hynes, D. Bradley, and D. Plumpley, Journal of Biomedical Materials Research Part A, 79A, 61 (2006).S.W. Robertson, and R.O. Ritchie, Biomaterials, 28, 700 (2007).N. Figueira, T.M. Silva, M.J. Carmezim, and J.C.S. Fernandes, Electrochimica Acta, 54, 921 (2009).D.E. Weisshaar, B.D. Lamp, and M.D. Porter, J. Am. Chem. Soc., 114, 5860 (1992).H. Ron, and I. Rubinstein, J. Am. Chem. Soc., 120, 13444 (1998).C.M.A. Brett, S. Kresak, T. Hianik, and M.O. Brett, Electroanalysis, 15, 557 (2003).S. Bengio, M. Fonticelli, G. Benitez, A.H. Creus, P. Carro, H. Ascolani, G. Zampieri, B. Blum, and R.C. Salvarezza, J. Phys. Chem. B, 109, 23450 (2005).C.R. Weber, L.F.P. Dick, G. Benitez, M.E. Vela, and R.C. Salvarezza, Electrochim. Acta, 54, 4817 (2009).Z. Petrovic, M. Metikos-Hukovic, J. Harvey, and S. Omanovic, Phys. Chem. Chem. Phys., 12, 6590 (2010).A. Maho, J. Denayer, J. Delhalle, and Z. Mekhalif, Electrochim. Acta, 56, 3954 (2011).N. Metoki, L. Liu, E. Beilis, N. Eliaz, and D. Mandler, Langmuir, 30 (23), 6791 (2014).

Improved ex vivo blood compatibility of central venous catheter with noble metal alloy coating.

Central line associated bloodstream infections (CLABSIs) are a serious cause of morbidity and mortality induced by the use of central venous catheters (CVCs). Nobel metal alloy (NMA) coating is an advanced surface modification that prevents microbial adhesion and growth on catheters and thereby reduces the risk of infection. In vitro microbiological analyses have shown up to 90% reduction in microbial adhesion on coated CVC compared to uncoated ones. This study aimed to assess the blood compatibility of NMA‐coated CVC according to ISO 10993‐4. Hemolysis, thrombin–antithrombin (TAT) complex, platelet counts, fibrin deposition, and C3a and SC5b‐9 complement activation were analyzed in human blood exposed to the NMA‐coated and control CVCs using a Chandler‐loop model. NMA‐coated CVC did not induce hemolysis and fell in the “nonhemolytic” category according to ASTM F756‐00. Significantly lower amounts of TAT were generated and less fibrin was deposited on NMA‐coated CVC than on uncoated ones. Slightly higher platelet counts and lower complement markers were observed for NMA‐coated CVC compared to uncoated ones. These data suggest that the NMA‐coated CVC has better ex vivo blood compatibility compared to uncoated CVC. © 2015 The Authors Journal of Biomedical Materials Research Part B: Applied Biomaterials Published by Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1359–1365, 2016.

A versatile x-ray microtomography station for biomedical imaging and materials research.

An x-ray microtomography station implemented at the X-ray Applied Crystallography Laboratory of the State University of Campinas is described. The station is based on a propagation based phase contrast imaging setup with a microfocus source and digital x-ray area detectors. Due to its simplicity, this setup is ideal for fast, high resolution imaging and microtomography of small biological specimens and materials research samples. It can also be coupled to gratings to use and develop new techniques as the harmonic spatial coherent imaging, which allow scattering contrast imaging. Details of the experimental setup, equipment, and software integration are described. Test microtomography for setup commissioning and characterization is shown. We conclude that phase contrast enhanced x-ray imaging and microtomography with resolution below 5 μm voxel size are possible and data sets as wide as 2000 × 2000 × 2000 voxels are obtained with this instrumentation.

Biocompatibility of calcium phosphate bone cement with optimized mechanical properties

The broad aim of this work was to investigate and optimize the properties of calcium phosphate bone cements (CPCs) for use in vertebroplasty to achieve effective primary fixation of spinal fractures. The incorporation of collagen, both bovine and from a marine sponge (Chondrosia reniformis), into a CPC was investigated. The biological properties of the CPC and collagen–CPC composites were assessed in vitro through the use of human bone marrow stromal cells. Cytotoxicity, proliferation, and osteoblastic differentiation were evaluated using lactate dehydrogenase, PicoGreen, and alkaline phosphatase activity assays, respectively. The addition of both types of collagen resulted in an increase in cytotoxicity, albeit not to a clinically relevant level. Cellular proliferation after 1, 7, and 14 days was unchanged. The osteogenic potential of the CPC was reduced through the addition of bovine collagen but remained unchanged in the case of the marine collagen. These findings, coupled with previous work showing that incorporation of marine collagen in this way can improve the physical properties of CPCs, suggest that such a composite may offer an alternative to CPCs in applications where low setting times and higher mechanical stability are important. © 2015 The Authors. Journal of Biomedical Materials Research Part B: Applied Biomaterials Published by Wiley Periodicals, Inc. 104B:308–315, 2015.

Brushite foams--the effect of Tween® 80 and Pluronic® F-127 on foam porosity and mechanical properties.

Resorbable calcium phosphate based bone void fillers should work as temporary templates for new bone formation. The incorporation of macropores with sizes of 100 −300 µm has been shown to increase the resorption rate of the implant and speed up bone ingrowth. In this work, macroporous brushite cements were fabricated through foaming of the cement paste, using two different synthetic surfactants, Tween® 80 and Pluronic® F‐127. The macropores formed in the Pluronic samples were both smaller and less homogeneously distributed compared with the pores formed in the Tween samples. The porosity and compressive strength (CS) were comparable to previously developed hydroxyapatite foams. The cement foam containing Tween, 0.5M citric acid in the liquid, 1 mass% of disodium dihydrogen pyrophosphate mixed in the powder and a liquid to powder ratio of 0.43 mL/g, showed the highest porosity values (76% total and 56% macroporosity), while the CS was >1 MPa, that is, the hardened cement could be handled without rupture of the foamed structure. The investigated brushite foams show potential for future clinical use, both as bone void fillers and as scaffolds for in vitro bone regeneration. © 2015 The Authors. Journal of Biomedical Materials Research Part B: Applied Biomaterials Published by Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 67–77, 2016.

Supramolecular self-assembly of novel thermo-responsive double-hydrophilic and hydrophobic Y-shaped [MPEO-b-PEtOx-b-(PCL)2] terpolymers

Nonlinear amphiphilic block copolymer architectures with precisely controlled structures bring new challenges to biomedical materials research.

Effect of microseparation on contact mechanics in metal-on-metal hip replacements-A finite element analysis.

Some early failures of metal‐on‐metal (MoM) hip replacements associated with elevated wear have caused concerns for the use of this bearing combination. Simulator studies have shown that microseparation and its associated rim contact and edge loading may produce the most severe wear in MoM bearings. It is generally recognized that this high wear can be attributed to the high contact stress of the head on the rim of the cup. In this study, an improved finite element contact model that incorporates an elastic‐perfectly plastic material property for cobalt‐chrome alloy of the metal bearing was developed in an attempt to provide an accurate prediction of the stress and strain for the rim contact. The effects of the microseparation displacement (0.1−2 mm), cup inclination angle (25−65°) and cup rim radius (0.5−4 mm) on the contact stress/strain were investigated. The results show that a translational displacement >0.1 mm under a load >0.5 kN can produce a highly concentrated contact stress at the surface of the cup rim which can lead to plastic deformation. This study also suggests that the magnitude of translational displacement was the major factor that determined the severity of the contact conditions and level of stress and strain under microseparation conditions. Future studies will address the effect of surgical translational and rotational malposition and component design on the magnitude of microseparation, contact stress and strain and severity of wear. © 2014 The Authors. Journal of Biomedical Materials Research Part B: Applied Biomaterials Published by Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 103B: 1312–1319, 2015.

Reticulation of low density shape memory polymer foam with an in vivo demonstration of vascular occlusion

Predominantly closed-cell low density shape memory polymer (SMP) foam was recently reported to be an effective aneurysm filling device in a porcine model (Rodriguez et al., Journal of Biomedical Materials Research Part A 2013: (http://dx.doi.org/10.1002/jbm.a.34782)). Because healing involves blood clotting and cell migration throughout the foam volume, a more open-cell structure may further enhance the healing response. This research sought to develop a non-destructive reticulation process for this SMP foam to disrupt the membranes between pore cells. Non-destructive mechanical reticulation was achieved using a gravity-driven floating nitinol pin array coupled with vibratory agitation of the foam and supplemental chemical etching. Reticulation resulted in a reduced elastic modulus and increased permeability, but did not impede the shape memory behavior. Reticulated foams were capable of achieving rapid vascular occlusion in an in vivo porcine model.

Injectable citrate‐modified Portland cement for use in vertebroplasty

The injectability of Portland cement (PC) with several citrate additives was investigated for use in clinical applications such as vertebroplasty (stabilization of a fractured vertebra with bone cement) using a syringe. A 2-wt % addition of sodium or potassium citrate with PC significantly improved cement injectability, decreased cement setting times from over 2 h to below 25 min, while increasing the compressive strength to a maximum of 125 MPa. Zeta-potential measurements indicated that the citrate anion was binding to one or more of the positively charged species causing charged repulsion between cement particles which dispersed aggregates and caused the liquefying effect of the anion. Analysis of the hydrating phases of PC indicated that the early strength producing PC phase (ettringite) developed within the first 2 h of setting following addition of the citrate anion, while this did not occur in the control cement (PC only). Within 24 h ettringite developed in PC as well as calcium–silicate–hydrate (C–S–H), the major setting phase of PC, whereas cements containing citrate did not develop this phase. The evidence suggested that in the presence of citrate the cements limited water supply appeared to be utilized for ettringite formation, producing the early strength of the citrate cements. The present study has demonstrated that it is possible to modify PC with citrate to both improve the injectability and crucially reduce the setting times of PC while improving the strength of the cement. © 2014 The Authors Journal of Biomedical Materials Research Part B: Applied Biomaterials Published by Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 102B: 1799–1808, 2014.

Interaction of micron and nano‐sized particles with cells of the dura mater

Intervertebral total disc replacements (TDR) are used in the treatment of degenerative spinal disc disease. There are, however, concerns that they may be subject to long-term failure due to wear. The adverse effects of TDR wear have the potential to manifest in the dura mater and surrounding tissues. The aim of this study was to investigate the physiological structure of the dura mater, isolate the resident dural epithelial and stromal cells and analyse the capacity of these cells to internalise model polymer particles. The porcine dura mater was a collagen-rich structure encompassing regularly arranged fibroblastic cells within an outermost epithelial cell layer. The isolated dural epithelial cells had endothelial cell characteristics (positive for von Willebrand factor, CD31, E-cadherin and desmoplakin) and barrier functionality whereas the fibroblastic cells were positive for collagen I and III, tenascin and actin. The capacity of the dural cells to take up model particles was dependent on particle size. Nanometer sized particles readily penetrated both types of cells. However, dural fibroblasts engulfed micron-sized particles at a much higher rate than dural epithelial cells. The study suggested that dural epithelial cells may offer some barrier to the penetration of micron-sized particles but not nanometer sized particles. © 2014 The Authors. Journal of Biomedical Materials Research Part B: Applied Biomaterials Published by Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 102B: 1496–1505, 2014.

Roger Eric Marchant, Ph.D.

Journal of Biomedical Materials Research Part AVolume 102, Issue 5 p. 1221-1221 Memoriam Roger Eric Marchant, Ph.D. March 8, 1951 – January 31, 2014 First published: 15 February 2014 https://doi.org/10.1002/jbm.a.35133Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume102, Issue5May 2014Pages 1221-1221 RelatedInformation

Covalently tethered TGF‐ β 1 with encapsulated chondrocytes in a PEG hydrogel system enhances extracellular matrix production

Healing articular cartilage defects remains a significant clinical challenge because of its limited capacity for self-repair. While delivery of autologous chondrocytes to cartilage defects has received growing interest, combining cell-based therapies with growth factor delivery that can locally signal cells and promote their function is often advantageous. We have previously shown that PEG thiol-ene hydrogels permit covalent attachment of growth factors. However, it is not well known if embedded chondrocytes respond to tethered signals over a long period. Here, chondrocytes were encapsulated in PEG hydrogels functionalized with transforming growth factor-beta 1 (TGF-β1) with the goal of increasing proliferation and matrix production. Tethered TGF-β1 was found to be distributed homogenously throughout the gel, and its bioactivity was confirmed with a TGF-β1 responsive reporter cell line. Relative to solubly delivered TGF-β1, chondrocytes presented with immobilized TGF-β1 showed significantly increased DNA content, and GAG and collagen production over 28 days, while maintaining markers of articular cartilage. These results indicate the potential of thiol-ene chemistry to covalently conjugate TGF-β1 to PEG to locally influence chondrocyte function over 4 weeks. Scaffolds with other or multiple tethered growth factors may prove broadly useful in the design of chondrocyte delivery vehicles for cartilage tissue engineering applications.

Moving Healthcare Forward

Moving Healthcare Forward

Oxidized alginate hydrogels as niche environments for corneal epithelial cells

Chemical and biochemical modification of hydrogels is one strategy to create physiological constructs that maintain cell function. The aim of this study was to apply oxidised alginate hydrogels as a basis for development of a biomimetic niche for limbal epithelial stem cells that may be applied to treating corneal dysfunction. The stem phenotype of bovine limbal epithelial cells (LEC) and the viability of corneal epithelial cells (CEC) were examined in oxidised alginate gels containing collagen IV over a 3-day culture period. Oxidation increased cell viability (P ≤ 0.05) and this improved further with addition of collagen IV (P ≤ 0.01). Oxidised gels presented larger internal pores (diameter: 0.2–0.8 µm) than unmodified gels (pore diameter: 0.05–0.1 µm) and were significantly less stiff (P ≤ 0.001), indicating that an increase in pore size and a decrease in stiffness contributed to improved cell viability. The diffusion of collagen IV from oxidised alginate gels was similar to that of unmodified gels suggesting that oxidation may not affect the retention of extracellular matrix proteins in alginate gels. These data demonstrate that oxidised alginate gels containing corneal extracellular matrix proteins can influence corneal epithelial cell function in a manner that may impact beneficially on corneal wound healing therapy. © 2013 The Authors. Journal of Biomedical Materials Research Part A Published byWiley Periodicals, Inc. Part A: 102A: 3393–3400, 2014.

Wear of novel ceramic‐on‐ceramic bearings under adverse and clinically relevant hip simulator conditions

Further development of ceramic materials for total hip replacement aim to increase fracture toughness and further reduce the incidence of bearing fracture. Edge loading due to translational mal positioning (microseparation) has replicated stripe wear, wear rates, and bimodal wear debris observed on retrievals. This method has replicated the fracture of early zirconia ceramic-on-ceramic bearings. This has shown the necessity of introducing microseparation conditions to the gait cycle when assessing the tribological performance of new hip replacement bearings. Two novel ceramic matrix composite materials, zirconia-toughened alumina (ZTA) and alumina-toughened zirconia (ATZ), were developed by Mathys Orthopädie GmbH. In this study, ATZ-on-ATZ and ZTA-on-ZTA bearing combinations were tested and compared with alumina-on-alumina (Al2O3-on-Al2O3) bearings under adverse microseparation and edge loading conditions using the Leeds II physiological anatomical hip joint simulator. The wear rate (±95% confidence limit) of ZTA-on-ZTA was 0.14 ± 0.10 mm(3)/million cycles and that of ATZ-on-ATZ was 0.06 ± 0.004 mm(3)/million cycles compared with a wear rate of 0.74 ± 1.73 mm(3)/million cycles for Al2O3-on-Al2O3 bearings. Stripe wear was evident on all bearing combinations; however, the stripe formed on the ATZ and ZTA femoral heads was thinner and shallower that that formed on the Al2O3 heads. Posttest phase composition measurements for both ATZ and ZTA materials showed no significant change in the monoclinic zirconia content. ATZ-on-ATZ and ZTA-on-ZTA showed superior wear resistance properties when compared with Al2O3-on-Al2O3 under adverse edge loading conditions.