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Species of the Ostreidae family are key ecosystem engineers and many of them - including Crassostrea gigas and Crassostreavirginica - are commercially important aquaculture species. Despite similarities in their morphology and ecology, these two species differ in their ability to defend against pathogens, potentially reflecting species-specific differential specialization of hemocytes on immune defense versus biomineralization. To test this hypothesis, we investigated the expression levels of immune- and biomineralization-related genes as well as mineralogical and mechanical properties of the shells and the calcium sequestration ability of the hemocytes of C. gigas and C. virginica The expression of biomineralization-related genes was higher in C. virginica than in C. gigas in multiple tissues including the mantle edge and hemocytes, while the expression of immune genes was higher in the hemocytes of C. gigas Hemocytes of C. virginica contained more calcium (stored intracellularly as calcium carbonate mineral) compared with those of C. gigas Analysis of the adult shells showed that the crystallinity of calcite was higher and the laths of the foliated layer of the shell were thicker in C. virginica than in C. gigas Mechanically, the shells of C. virginica were stiffer, harder and stronger than those of C. gigas Taken together, our results show that the species-specific differences in physiology (such as disease resistance and exoskeleton properties) are reflected at the cellular and molecular levels in the differential specialization of hemocytes on potentially competing functions (immunity and biomineralization) as well as different expression profiles of other tissues involved in biomineralization (such as the mantle edge).
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Exoesqueleto/fisiologia , Biomineralização/fisiologia , Crassostrea/fisiologia , Hemócitos/imunologia , Imunidade Inata/fisiologia , Transcriptoma/fisiologia , Animais , Biomineralização/imunologia , Crassostrea/genética , Crassostrea/imunologia , Especificidade da EspécieRESUMO
The fabrication of ß-CoV3O8 nanorods embedded in graphene sheets and their application as electrochemical charge storage electrodes is reported. From the surfactant treatment of raw graphite, graphene was directly prepared and its nanocomposite with ß-CoV3O8 nanorods distributed between graphene layers (ß-CoV3O8-G) was synthesized by a hydrothermal method. When applied as an anode in lithium-ion batteries, the ß-CoV3O8-G anode exhibits greatly improved charge and discharge capacities of 790 and 627 mAh · g-1, respectively, with unexpectedly high initial efficiency of 82%. The observed discharge capacity reflected that at least 3.7 mol of Li+ is selectively accumulated within the ß-CoV3O8 phase (LixCoV3O8, x > 3.7), indicative of significantly improved Li+ uptake when compared with aggregated ß-CoV3O8 nanorods. Moreover, very distinct peak plateaus and greatly advanced cycling performance are observed, showing more improved Li+ storage within the ß-CoV3O8 phase. As a supercapacitor electrode, moreover, our composite electrode exhibits very high peak pseudocapacitances of 2.71 F · cm-2 and 433.65 F · g-1 in the ß-CoV3O8 phase with extremely stable cycling performance. This remarkably enhanced performance in the individual electrochemical charge storage electrodes is attributed to the novel phase formation of ß-CoV3O8 and its optimized nanocomposite structure with graphene, which yield fast electrical conduction through graphene, easy accessibility of ions through the open multilayer nanosheet structure, and a relaxation space between the ß-CoV3O8-G.
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OBJECTIVE: Utilizing a novel histopathological scoring system and subglottic stenosis (SGS) rabbit model, we aimed to compare degrees of inflammation and severity of narrowing in the subglottis between two minimally invasive therapeutic modalities: endoscopic balloon dilation (EBD) alone versus EBD with placement of a bioabsorbable ultra-high ductility magnesium (UHD-Mg) alloy stent. METHODS: SGS was induced endoscopically via microsuspension laryngoscopy in 23 New Zealand white rabbits. The control group (n = 11) underwent EBD alone, the study arm (n = 12) underwent EBD with implantation of bioabsorbable UHD-Mg alloy stents. Rabbits were euthanized at 2-, 3-, and 6-weeks after SGS induction, coinciding with wound healing stages. Using Optical Coherence Tomography (OCT), cross-sectional areas of airways were compared to calculate the mean percentage of intraluminal area at sequential time points. A novel histopathological scoring system was used to analyze frozen sections of laryngotracheal complexes. The degree of inflammation was quantified by scoring changes in inflammatory cell infiltration, epithelial ulceration/metaplasia, subepithelial edema/fibrosis, and capillary number/dilation. Univariate analysis was utilized to analyze these markers. RESULTS: We found rabbits implanted with the bioabsorbable UHD-Mg alloy stent had statistically significantly higher scores in categories of hyperplastic change (stents vs controls: 1.48 vs 0.46 p < 0.001), squamous metaplasia (22 vs 5 p < 0.001), and neutrophils/fibrin in lumen (31 vs 8, p < 0.001). Rabbits who received EBD alone had higher scores of subepithelial edema and fibrosis (2.70 vs 3.49, p < 0.0256). The stented rabbits demonstrated significantly increased mean percent stenosis by intraluminal mean area compared to controls at 2 weeks (88.56 vs 58.98, p = 0.032), however at all other time points there was no significant difference between intraluminal subglottic stenosis by mean percent stenosis area. DISCUSSION: Rabbits with SGS treated with UHD-Mg alloy stents demonstrated histopathologic findings suggestive of lower levels of tracheal fibrosis. This could indicate a reduced tendency towards the development of stenosis when compared to EBD alone. There was not a difference in luminal size between stent and non-stented rabbits at the six-week end point. Histologically, however, overall the use of bioabsorbable UHD-Mg alloy stenting elicited a greater tissue response at the level of the superficial mucosa rather than fibrosis of the lamina propria seen in the stented rabbits. This suggests more favorable healing and less of a tendency towards fibrosis and stenosis even though there may not be a benefit from a luminal size standpoint during this early healing period. Compared to known complications of currently available non-bioabsorbable metal or silicone-based stents, this proof-of-concept investigation highlights the potential use of a novel biodegradable UHD-Mg stent as a therapeutic modality for pediatric SGS.
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Implantes Absorvíveis , Ligas , Modelos Animais de Doenças , Laringoscopia , Laringoestenose , Magnésio , Stents , Animais , Coelhos , Laringoestenose/patologia , Laringoestenose/terapia , Inflamação/patologia , Dilatação/instrumentação , Índice de Gravidade de DoençaRESUMO
Polymeric film coatings were applied by dip coating on two magnesium alloy systems, AZ31 and Mg4Y, in an attempt to slow the degradation of these alloys under in vitro conditions. Poly(lactic-co-glycolic acid) polymer in solution was explored at various concentrations, yielding coatings of varying thicknesses on the alloy substrates. Electrochemical corrosion studies indicate that the coatings initially provide some corrosion protection. Degradation studies showed reduced degradation over 3 days, but beyond this time point however, do not maintain a reduction in corrosion rate. Scanning electron microscopy indicates inhomogeneous coating durability, with gas pocket formation in the polymer coating, resulting in eventual detachment from the alloy surface. In vitro studies of cell viability utilizing mouse osteoblast cells showed improved biocompatibility of polymer coated substrates over the bare AZ31 and Mg4Y substrates. Results demonstrate that while challenges remain for long term degradation control, the developed polymeric coatings nevertheless provide short term corrosion protection and improved biocompatibility of magnesium alloys for possible use in orthopedic applications.
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Ligas , Materiais Revestidos Biocompatíveis , Magnésio/química , Ortopedia , Poliglactina 910/química , Células 3T3 , Animais , Camundongos , Microscopia Eletrônica de Varredura , Espectroscopia de Infravermelho com Transformada de FourierRESUMO
Polyelectrolyte layer-by-layer (LbL) films on pretreated Mg containing 3 wt.% Al and 1 wt.% Zn (MgAZ31) alloy surfaces were prepared under physiological conditions offering improved bioresponse and corrosive protection. Pretreatments of the model MgAZ31 substrate surfaces were performed by alkaline and fluoride coating methods. The anti-corrosion and cytocompatibility behavior of pretreated substrates were evaluated. The LbL film assembly consisted of an initial layer of polyethyleneimine (PEI), followed by alternate layers of poly (lactic-co-glycolic acid) (PLGA) and poly (allylamine hydrochloride) (PAH), which self-arrange via electrostatic interactions on the pretreated MgAZ31 alloy substrate surface. The physicochemical characterization, surface morphologies, and microstructures of the LbL films were investigated using Fourier-transformed infrared spectroscopy (FTIR), atomic force microscopy (AFM), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The in vitro stability studies related to the LbL coatings confirmed that the surface treatments are imperative to achieve the lasting stability of PLGA/PAH layers. Electrochemical impedance spectroscopy measurements demonstrated that pretreated and LbL multilayered coated substrates enhanced the corrosion resistance of the bare MgAZ31 alloy. Cytocompatibility studies using human mesenchymal stem cells seeded directly over the substrates showed that the pretreated and LbL-generated surfaces were more cytocompatible, displaying reduced cytotoxicity than the bare MgAZ31. The release of bovine serum albumin protein from the LbL films was also studied. The initial data presented cooperatively demonstrate the promise of creating LbL layers on Mg-related bioresorbable scaffolds to obtain improved surface bio-related activity.
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Three-dimensional (3D) printing is implemented for surface modification of titanium alloy substrates with multilayered biofunctional polymeric coatings. Poly(lactic-co-glycolic) acid (PLGA) and polycaprolactone (PCL) polymers were embedded with amorphous calcium phosphate (ACP) and vancomycin (VA) therapeutic agents to promote osseointegration and antibacterial activity, respectively. PCL coatings revealed a uniform deposition pattern of the ACP-laden formulation and enhanced cell adhesion on the titanium alloy substrates as compared to the PLGA coatings. Scanning electron microscopy and Fourier-transform infrared spectroscopy confirmed a nanocomposite structure of ACP particles showing strong binding with the polymers. Cell viability data showed comparable MC3T3 osteoblast proliferation on polymeric coatings as equivalent to positive controls. In vitro live/dead assessment indicated higher cell attachments for 10 layers (burst release of ACP) as compared to 20 layers (steady release) for PCL coatings. The PCL coatings loaded with the antibacterial drug VA displayed a tunable release kinetics profile based on the multilayered design and drug content of the coatings. Moreover, the concentration of active VA released from the coatings was above the minimum inhibitory concentration and minimum bactericidal concentration, demonstrating its effectiveness against Staphylococcus aureus bacterial strain. This research provides a basis for developing antibacterial biocompatible coatings to promote osseointegration of orthopedic implants.
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Mineralized tissues such as dentin and bone assemble extracellular matrices uniquely rich in a variety of acidic phosphoproteins. Although these proteins are presumed to play a role in the process of biomineralization, key questions regarding the nature of their contributions remain unanswered. First, it is not known whether highly phosphorylated proteins alone can induce matrix mineralization, or whether this activity requires the involvement of other bone/dentin non-collagenous proteins. Second, it remains to be established whether the protein kinases that phosphorylate these acidic proteins are unique to cells responsible for producing mineralized tissues. To begin to address these questions, we consider the case of phosphophoryn (PP), due to its high content of phosphate, high affinity for Ca(2+), and its potential role in hydroxyapatite nucleation. We have created a model system of biomineralization in a cellular environment by expressing PP in NIH3T3 fibroblasts (which do not produce a mineralized matrix); as a positive control, PP was expressed in MC3T3-E1 osteoblastic cells, which normally mineralize their matrices. We show that expression of PP in NIH3T3 cells is sufficient for the induction of matrix mineralization. In addition, assessment of the phosphorylation status of PP in these cells reveals that the transfected NIH3T3 cells are able to phosphorylate PP. We suggest that the phosphorylation of PP is essential for mineral formation. The principle goal of this study is to enrich the current knowledge of mineralized tissue phosphorylation events by analyzing them in the context of a complete cellular environment.
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Calcificação Fisiológica/fisiologia , Cálcio/metabolismo , Durapatita/metabolismo , Matriz Extracelular/metabolismo , Regulação da Expressão Gênica/fisiologia , Fosfoproteínas/biossíntese , Animais , Matriz Extracelular/genética , Camundongos , Células NIH 3T3 , Fosfoproteínas/genéticaRESUMO
Human pluripotent stem cells (hPSCs) have enormous potential to alleviate cell needs for regenerative medicine, however these cells require expansion in cell colonies to maintain cell-cell contact, thus limiting the scalability needed to meet the demands of cell therapy. While the use of a Rho-associated protein kinase (ROCK) inhibitor will allow for culture of single cell hPSCs, typically only 50% of cells are recovered after dissociation. When hPSCs lose cell-cell contact through E-cadherin, dissociation induced apoptosis occurs. In this study, we hypothesized that the extracellular E-cadherin domain of hPSCs will bind to synthetic E-cadherin peptides presented on a hydrogel substrate, mimicking the required cell-cell contact and thereby retaining single-cell viability and clonogenicity. Hence, the objective of this study was to functionalize alginate hydrogels with synthetic peptides mimicking E-cadherin and evaluate peptide performance in promoting cell attachment, viability, maintaining pluripotency, and differentiation potential. We observed that alginate conjugated with synthetic E-cadherin peptides not only supported initial cell attachment with high viability, but also supported hPSC propagation and high fold expansion. hPSCs propagated on the peptide modified substrates maintained the hPSC characteristic pluripotency and differentiation potential, characterized by both spontaneous and directed differentiation. STATEMENT OF SIGNIFICANCE: Human pluripotent stem cells (hPSCs) have enormous potential to alleviate cell needs for regenerative medicine and cell therapy. However, scalable culture of hPSCs is challenged by its need for maintenance of cell-cell contact, dissociation of which triggers the apoptotic pathway. Hence hPSCs are commonly maintained as colonies over Matrigel coated culture plates. Furthermore, use of xenogenic and undefined Matrigel compromises the translational potential of hPSCs. In this work we have developed a completely defined substrate to enable adherent culture of hPSCs as single cells. This substrate prevents apoptosis of the single cells and allows significant fold expansion of hPSCs while maintaining pluripotency and differentiation potential. The developed substrate is expected to be a cost-effective and translatable alternative to Matrigel.
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Técnicas de Cultura de Células , Diferenciação Celular , Peptídeos , Células-Tronco Pluripotentes , Humanos , Hidrogéis , Peptídeos/farmacologiaRESUMO
Magnesium alloys are the most widely studied biodegradable metals for biodegradable vascular stent application. Two major issues with current magnesium alloy based stents are their low ductility and fast corrosion rates. Several studies have validated that introduction of Li into the magnesium alloys will significantly improve the ductility while alloying with Al will improve the corrosion resistance and strength. In the present study, we studied the effects of alloying different amounts of Li and Al on the Mg-Li-Al-Zn (LAZ) quaternary alloy system. Rods were made from four different LAZ alloys, namely, LAZ611, LAZ631, LAZ911, and LAZ931 following melting, casting, and then extrusion. Systematic assessment of mechanical properties, in vitro corrosion, cytotoxicity, and in vivo degradation including local and systemic toxicity conducted demonstrated the beneficial effects of Li and Al on the mechanical properties. Our results specifically suggest that alloying with Li significantly improved the ductility while Al enhanced the strength of the LAZ alloys. Four of the LAZ alloys exhibited different corrosion rates in Hank's balanced salt solution depending on the chemical composition. Indirect in vitro cytotoxicity tests also showed lower cytotoxicity for the alloys exhibiting higher corrosion resistance. In vivo corrosion rates in the mouse subcutaneous model showed different corrosion rates compared to the in vitro tests. Nevertheless, all of the four LAZ alloys displayed no local and systemic toxicity based on the histology analysis. This research study, therefore, demonstrated the benefits of using Li and Al as alloying elements in LAZ alloys and the potential use of LAZ alloys for vascular stent application.
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Alumínio , Lítio , Ligas/toxicidade , Alumínio/toxicidade , Animais , Materiais Biocompatíveis/toxicidade , Teste de Materiais , Camundongos , Stents , Zinco/toxicidadeRESUMO
OBJECTIVE: Develop a clinically relevant and reproducible endoscopic animal model for subglottic stenosis amenable to testing of minimally invasive therapeutic modalities. STUDY DESIGN: Cohort study. SETTING: Division of Laboratory Animals Research, University of Pittsburgh. SUBJECTS AND METHODS: Subglottic stenosis was induced endoscopically via microsuspension laryngoscopy in 26 New Zealand white rabbits. A trimmed polypropylene brush connected to a novel electronic stenosis induction apparatus was used to create circumferential trauma to the subglottis. By using open source image analysis software, the cross-sectional areas of the stenotic and native airways were compared to calculate the percentage of stenosis and the Myer-Cotton classification grade. RESULTS: Of the 26 rabbits, 24 (92%) exhibited stenosis after the first attempt. The mean percentage of airway stenosis was 57% (range, 34%-85%; SD, 15%). Five rabbits (19.2%) died on the day of stenosis induction from procedural complications. Of the 21 rabbits, 2 demonstrated no stenosis 7 days after initial injury and so underwent reinduction of airway injury, upon which they developed stenosis. Overall, 14 of the 21 rabbits (67%) exhibited moderate to severe stenosis (grade 2 or 3). CONCLUSION: The stenosis induction apparatus reliably induced stenosis with a low mortality rate as compared with that of other methods in the literature. The device could be improved to generate a predetermined potentially reproducible grade of stenosis as desired by the operator. This method sets the stage for a clinically relevant and reproducible subglottic stenosis disease model that is amenable to testing of minimally invasive treatment modalities.
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Glote/cirurgia , Laringoscopia/métodos , Laringoestenose/cirurgia , Animais , Modelos Animais de Doenças , Glote/diagnóstico por imagem , Laringoestenose/diagnóstico , Coelhos , Reprodutibilidade dos TestesRESUMO
Pediatric laryngotracheal stenosis is a complex congenital or acquired airway injury that may manifest into a potentially life-threatening airway emergency condition. Depending on the severity of obstruction, treatment often requires a combination of endoscopic techniques, open surgical repair, intraluminal stenting, or tracheostomy. A balloon expandable biodegradable airway stent maintaining patency while safely degrading over time may address the complications and morbidity issues of existing treatments providing a less invasive and more effective management technique. Previous studies have focused on implementation of degradable polymeric scaffolds associated with potentially life-threatening pitfalls. The feasibility of an ultra-high ductility magnesium-alloy based biodegradable airway stents was demonstrated for the first time. The stents were highly corrosion resistant under in vitro flow environments, while safely degrading in vivo without affecting growth of the rabbit airway. The metallic matrix and degradation products were well tolerated by the airway tissue without exhibiting any noticeable local or systemic toxicity.
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Ligas , Materiais Biocompatíveis , Lítio , Magnésio , Stents , Zinco , Obstrução das Vias Respiratórias/diagnóstico , Obstrução das Vias Respiratórias/terapia , Animais , Biópsia , Criança , Modelos Animais de Doenças , Humanos , Imageamento Tridimensional , Imuno-Histoquímica , Nanotecnologia , Coelhos , Radiografia , Estenose Traqueal/diagnóstico , Estenose Traqueal/terapia , Resultado do Tratamento , Microtomografia por Raio-XRESUMO
Bone is the most preferred site for colonization of metastatic breast cancer cells for each subtype of the disease. The standard of therapeutic care for breast cancer patients with bone metastasis includes bisphosphonates (e.g., zoledronic acid), which have poor oral bioavailability, and a humanized antibody (denosumab). However, these therapies are palliative, and a subset of patients still develop new bone lesions and/or experience serious adverse effects. Therefore, a safe and orally bioavailable intervention for therapy of osteolytic bone resorption is still a clinically unmet need. This study demonstrates suppression of breast cancer-induced bone resorption by a small molecule (sulforaphane, SFN) that is safe clinically and orally bioavailable. In vitro osteoclast differentiation was inhibited in a dose-dependent manner upon addition of conditioned media from SFN-treated breast cancer cells representative of different subtypes. Targeted microarrays coupled with interrogation of The Cancer Genome Atlas data set revealed a novel SFN-regulated gene signature involving cross-regulation of runt-related transcription factor 2 (RUNX2) and nuclear factor-κB and their downstream effectors. Both RUNX2 and p65/p50 expression were higher in human breast cancer tissues compared with normal mammary tissues. RUNX2 was recruited at the promotor of NFKB1 Inhibition of osteoclast differentiation by SFN was augmented by doxycycline-inducible stable knockdown of RUNX2. Oral SFN administration significantly increased the percentage of bone volume/total volume of affected bones in the intracardiac MDA-MB-231-Luc model indicating in vivo suppression of osteolytic bone resorption by SFN. These results indicate that SFN is a novel inhibitor of breast cancer-induced osteolytic bone resorption in vitro and in vivo.
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Neoplasias Ósseas/secundário , Reabsorção Óssea/metabolismo , Neoplasias da Mama/tratamento farmacológico , Redes Reguladoras de Genes/genética , Isotiocianatos/uso terapêutico , Animais , Feminino , Humanos , Isotiocianatos/farmacologia , Camundongos , SulfóxidosRESUMO
Rechargeable lithium ion batteries are integral to today's information-rich, mobile society. Currently they are one of the most popular types of battery used in portable electronics because of their high energy density and flexible design. Despite their increasing use at the present time, there is great continued commercial interest in developing new and improved electrode materials for lithium ion batteries that would lead to dramatically higher energy capacity and longer cycle life. Silicon is one of the most promising anode materials because it has the highest known theoretical charge capacity and is the second most abundant element on earth. However, silicon anodes have limited applications because of the huge volume change associated with the insertion and extraction of lithium. This causes cracking and pulverization of the anode, which leads to a loss of electrical contact and eventual fading of capacity. Nanostructured silicon anodes, as compared to the previously tested silicon film anodes, can help overcome the above issues. As arrays of silicon nanowires or nanorods, which help accommodate the volume changes, or as nanoscale compliant layers, which increase the stress resilience of silicon films, nanoengineered silicon anodes show potential to enable a new generation of lithium ion batteries with significantly higher reversible charge capacity and longer cycle life.
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Fontes de Energia Elétrica , Eletrodos , Lítio/química , Nanoestruturas/química , Nanotecnologia/métodos , Silício/químicaRESUMO
Phosphophoryn (PP) is an acidic phosphoprotein belonging to the small integrin-bindingligand N-linked glycoprotein (SIBLING) protein family. PP is highly phosphorylated with approximately 200 phosphates per molecule and has a high affinity for calcium. The aim of this manuscript is to demonstrate that PP has the ability to self-assemble when it is overexpressed in a mammalian cell in the presence of calcium. Our data show that when PP is overexpressed using an adenovirus, the self-assembly occurs in the endoplasmic reticulum (ER) which contains high calcium concentration. We hypothesize that the physicochemical properties of the highly phosphorylated state and acidic nature of PP are playing an important role in its assembly in the ER. It appears that when a critical concentration of PP is reached, the assembly is then favored and facilitated. This self-assembly could be due to several factors. (1) The ER provides an ideal environment for this phenomenon to occur, since the ER environment usually promotes aggregation [Stevens and Argon: Semin Cell Dev Biol 1999;10:443-454]. (2) In addition to PP's physicochemical properties, the unfolded protein response could also be playing a role in this self-assembly [Schroder and Kaufman: Mutat Res 2005;569:29-63]. Unfolded protein response could be activated by a broad spectrum of insults that result in protein misfolding and ultimately blocking of the protein synthesis progression to the Golgi apparatus resulting in an accumulation of the protein in the ER. In summary, our data show that PP has the ability to self-assemble in a hierarchical manner.
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Materiais Biomiméticos/metabolismo , Células-Tronco Mesenquimais/citologia , Células-Tronco Mesenquimais/metabolismo , Fosfoproteínas/metabolismo , Adenoviridae/metabolismo , Sequência de Aminoácidos , Animais , Clonagem Molecular , Retículo Endoplasmático/metabolismo , Retículo Endoplasmático/ultraestrutura , Humanos , Células-Tronco Mesenquimais/ultraestrutura , Camundongos , Dados de Sequência Molecular , Fosfoproteínas/químicaRESUMO
Airway obstruction conditions are relatively rarely observed in clinical settings but nevertheless, extremely challenging to handle, especially when observed in pediatric patients. Several surgical procedures, including tracheal resection, end-to-end tracheal anastomosis, and tracheoplasty, have been developed and practised of late, to treat airway obstruction. However, the clinical outcome is typically not satisfactory due to airway restenosis conditions that develop following surgery. Various types of stents are currently available for airway stenting ranging from non-degradable silicone tubes and bio-inert metallic stents (bare or coated with polymer matrix) to hybrid silicone tubes strengthened by metallic cores, but none of the stents provides the satisfactory long-term effectiveness. Therefore, there is a significant clinical need for a biodegradable airway stent that would maintain airway patency and totally degrade over time after meeting the desired objectives. The present study aims to investigate biodegradable magnesium-aluminum-zinc-calcium-manganese (AZXM) alloy as a potential tracheal stent. The new AZXM alloy was fabricated by partially replacing aliminum in commercial AZ31 alloy with calcium. The present study demonstrates that calcium preferentially segregates along the grain boundaries as intermetallic phases (Mg2Ca) and is homogeneously distributed in the magnesium matrix. The extruded AZXM alloy showed less pitting, higher corrosion resistance in Hank's Balanced Salt Solution (HBSS) compared to the as-cast and solution-treated AZXM alloys and exhibited optimized mechanical properties. In vitro cytotoxicity evaluation using human trachea epithelial cells demonstrated excellent cyto-compatibility of AZXM alloys compared to pure Mg and commercial AZ31 validated by a very preliminary rabbit in vivo tracheal model study. Preliminary results show that the approach to use biodegradable AZXM alloys as a tracheal stent is indeed promising, although further alloy processing is required to improve the ductility needed followed by a more exhaustive in vivo study to demonstrate full viability for stent applications.
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Implantes Absorvíveis , Ligas/química , Materiais Biocompatíveis/química , Stents , Traqueia/cirurgia , Animais , Cálcio/química , Linhagem Celular , Sobrevivência Celular , Corrosão , Estudos de Viabilidade , Humanos , Manganês/química , Teste de Materiais , Coelhos , Mucosa Respiratória/citologia , Traqueia/citologiaRESUMO
Tracheal stenting currently using non-degradable stents is commonplace for treatment of trauma, prolonged intubation related adult airway obstructions, and pediatric patients-associated tracheal stenosis conditions. Degradable tracheal stent placement will avoid complications of stent removal and restenosis. Widespread reports exist on degradable magnesium alloys success for orthopedic and cardiovascular applications but none to date for intra tracheal use. This research explores the use of pure Mg, AZ31, and Mg-3Y alloys for degradable tracheal stent assessment. In vitro evaluation of magnesium, prototype stents in a bioreactor simulate the airway environment and corrosion. Micro-CT imaging and biocompatibility evaluation helped assess the 24-week degradation of intraluminal alloy stents following implantation in a rat tracheal in vivo bypass model. Histological analysis indicate tissue response of the harvested stented trachea segments after each time point. Corrosion studies for each alloy indicate significant differences between the simulated and control in vitro conditions. AZ31 exhibited the lowest volume loss of 6.8% in saline, while pure Mg displayed the lowest volume loss of 4.6% in simulated airway fluid (SAF), both at 1-week time points. Significant differences in percentage of total volume lost after 6 months were determined between the alloys over time. MgY alloy displayed the slowest corrosion losing only 15.1% volume after 24 weeks of immersion. Additionally, in vitro magnesium alloy corrosion was not significantly different from the percentage of total volume lost in vivo at 1-week time point. The study demonstrates promise of magnesium alloys for intraluminal tracheal stent application albeit viability of a clinically translatable model warrants further studies. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1844-1853, 2019.
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Implantes Absorvíveis , Ligas , Materiais Revestidos Biocompatíveis , Magnésio , Teste de Materiais , Traqueia , Animais , Criança , Feminino , Humanos , Ratos , Ratos Endogâmicos Lew , Traqueia/metabolismo , Traqueia/patologia , Traqueia/cirurgiaRESUMO
Biodegradable magnesium (Mg) alloys exhibit improved mechanical properties compared to degradable polymers while degrading in vivo circumventing the complications of permanent metals, obviating the need for surgical removal. This study investigated the safety and efficacy of Mg-Y-Zn-Zr-Ca (WZ42) alloy compared to non-degradable Ti6Al4V over a 14-week follow-up implanted as pins to fix a full osteotomy in rat femurs and as wires wrapped around the outside of the femurs as a cerclage. We used a fully load bearing model allowing implants to intentionally experience realistic loads without immobilization. To assess systemic toxicity, blood cell count and serum biochemical tests were performed. Livers and kidneys were harvested to observe any accumulation of alloying elements. Hard and soft tissues adjacent to the fracture site were also histologically examined. Degradation behavior and bone morphology were determined using micro-computed tomography scans. Corrosion occurred gradually, with degradation seen after two weeks of implantation with points of high stress observed near the fracture site ultimately resulting in WZ42 alloy pin fracture. At 14 weeks however, normal bone healing was observed in femurs fixed with the WZ42 alloy confirmed by the presence of osteoid, osteoblast activity, and new bone formation. Blood testing exhibited no significant changes arising from the WZ42 alloy compared to the two control groups. No recognizable differences in the morphology and more importantly, no accumulation of Mg, Zn, and Ca in the kidney and liver of rats were observed. These load bearing model results collectively taken, thus demonstrate the feasibility for use of the Mg-Y-Zn-Zr-Ca alloy for long bone fracture fixation applications.
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Implantes Absorvíveis , Ligas/uso terapêutico , Pinos Ortopédicos , Fraturas do Fêmur/cirurgia , Implantes Absorvíveis/efeitos adversos , Ligas/efeitos adversos , Animais , Materiais Biocompatíveis/efeitos adversos , Materiais Biocompatíveis/uso terapêutico , Pinos Ortopédicos/efeitos adversos , Cálcio/efeitos adversos , Cálcio/uso terapêutico , Corrosão , Feminino , Fraturas do Fêmur/patologia , Fraturas do Fêmur/terapia , Fêmur/patologia , Fêmur/cirurgia , Teste de Materiais , Ratos Sprague-Dawley , Titânio/efeitos adversos , Titânio/uso terapêuticoRESUMO
The present study investigates the potential use of forsterite as an orthopedic biomaterial along with the role of strontium oxide (SrO) as a dopant. The in vitro degradation behavior was measured as a function of immersion time in simulated body fluid (SBF) for up to 8 weeks and was analyzed by micro computed tomography (µ-CT) and scanning electron microscopy (SEM). All the doped samples showed higher degradation than pure sample. The in vitro cytocompatibility study showed good cytocompatibility and proliferation of MC3T3-E1 cells on Sr-doped MgS samples. The in vivo experiments were carried out by implanting the ceramics in a rabbit femur for 30 and 90 days. The 3D µ-CT and SEM images of 2 and 3 wt % Sr-doped MgS showed increased bone regeneration around the implant materials compared with pure and 1 wt % Sr-doped MgS, which was further confirmed by quantitative oxytetracycline labeling. The histological examination of three major organs of heart, kidney, and liver confirmed that the degradation product of the MgS ceramics, with or without doping, had no toxicological side effects. These results indicate that Sr-doped MgS bioceramics exhibit enhanced degradability with the potential to be used for temporary bone regeneration.
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An enzyme aggregate of alginate lyase (EC 4.2.2.3) from flavobactierium was prepared using ammonium sulfate. The resultant aggregates upon cross-linking with glutaraldehyde produced insoluble and catalytically active cross-linked enzyme aggregate (CLEA) enzyme. The catalytic activity and stability of the cross-linked enzyme aggregate of alginate lyase (CLEA-AL) was studied in the presence of various pH, temperatures and organic solvents. Reusability, storage stability and surface morphology of the CLEA-AL were also studied. The native enzyme and CLEA-AL exhibited maximum enzyme activity at pH of 6.3 and at a temperature of 40°C. The CLEA-AL has good stability in nonpolar organic solvents and is thermally stable up to 50°C over a period of 8h. By encapsulating CLEA-AL into alginate hydrogel, we demonstrate that alginate hydrogels can be enzymatically degraded in a controlled fashion. The results also showed that degradation of alginate hydrogel with CLEA-AL incorporated beads is slower than native enzyme and therefore, CLEA-AL can be used for controlled degradation and release of various biologics from the degrading gel.