RESUMEN
Many species have cuticular striations that play a range of roles, from pollinator attraction to surface wettability. In Hibiscus trionum, the striations span multiple cells at the base of the petal to form a pattern that produces a type of iridescence. It is postulated, using theoretical models, that the pattern of striations could result from mechanical instabilities. By combining the application of mechanical stress with high-resolution imaging, we demonstrate that the cuticle buckles to create a striated pattern. Through mechanical modeling and cryo-SEM fractures, we show that the cuticle behaves like a bilayer system with a stiff film on a compliant substrate. The pattern of buckling aligns with the direction of the stress to create a larger-scale pattern. Our findings contribute to the understanding of the formation of tissue-wide patterns in living organisms.
Asunto(s)
Hibiscus/química , Luz , Fenómenos Mecánicos/efectos de la radiación , Fuerza Compresiva , Microscopía por Crioelectrón , Flores/química , Flores/efectos de la radiación , Flores/ultraestructura , Hibiscus/crecimiento & desarrollo , Hibiscus/efectos de la radiación , Modelos Teóricos , Semillas/química , Semillas/crecimiento & desarrollo , Estrés MecánicoRESUMEN
Few studies performed a microstructural analysis of dental restorations to evaluate fatigue impact under various tensions, because of a lack of analytical equipment. In this study, the fatigue of restorative materials was evaluated using the force tester's fatigue method at 0.30, 0.3, 0.40, and 0.45 N. The fatigue effect analysis of tooth restorations was performed with each sample by randomly dividing the sequence into grades 0-4 and the evaluators were blinded to the test results. The evaluation methods involved visual and stereoscopic approaches, and used synchrotron radiation (SR). The evaluation facilitated the observation of microscopic cracks in the material using SR. The initiation of cracks was attributed to air bubbles, invisible to the naked eye or under the microscope. The fatigue effect analysis using SR enabled closer observations compared with other types of evaluation. We expect that this strategy will provide a basis for the study of physical and mechanical properties of dental materials.
Asunto(s)
Materiales Dentales/efectos de la radiación , Restauración Dental Permanente/métodos , Fenómenos Mecánicos/efectos de la radiación , Sincrotrones , Materiales Dentales/análisis , Ensayo de Materiales , MicroscopíaRESUMEN
Development of bio-microactuators combining microdevices and cellular mechanical functions has been an active research field owing to their desirable properties including high mechanical integrity and biocompatibility. Although various types of devices were reported, the use of as-is natural muscle tissue should be more effective. An earthworm muscle-driven valve has been created. Long-time (more than 2 min) and repeatable displacement was observed by chemical (acetylcholine) stimulation. The generated force of the muscle (1 cm × 3 cm) was 1.57 mN on average for 2 min by the acetylcholine solution (100 mM) stimulation. We demonstrated an on-chip valve that stopped the constant pressure flow by the muscle contraction. For electrical control, short pulse stimulation was used for the continuous and repeatable muscle contraction. The response time was 3 s, and the pressure resistance was 3.0 kPa. Chemical stimulation was then used for continuous muscle contraction. The response time was 42 s, and the pressure resistance was 1.5 kPa. The ON (closed) state was kept for at least 2 min. An on-chip valve was demonstrated that stopped the constant pressure flow by the muscle contraction. This is the first demonstration of the muscle-based valve that is 100% chemically actuated and controlled.
Asunto(s)
Acetilcolina/química , Estimulación Eléctrica , Oligoquetos/fisiología , Animales , Electricidad , Fenómenos Mecánicos/efectos de la radiación , Contracción Muscular/efectos de los fármacos , Contracción Muscular/efectos de la radiación , Músculo Liso/química , Músculos/química , Oligoquetos/química , Tráquea/química , Tráquea/efectos de los fármacosRESUMEN
We report an ultrasound-driven gold-nanoshell-functionalized polymer multilayer tubular nanoswimmer that can photomechanically perforate the membrane of a cancer cell by assistance of near-infrared (NIR) light. The nanoswimmers were constructed by a template-assisted layer-by-layer technique and subsequent functionalization of Au nanoshells inside the big opening. The nanoswimmers exhibit efficient and controllable movement toward target cells through the manipulation of the acoustic field. Next, the nanoswimmers with end-on attachment onto the HeLa cells achieve the poration of the cell membrane within 0.1 s under the irradiation of NIR light. The experimental and theoretical results suggest that the instantaneous photothermal effect provides enough photomechanical force to open the cell membrane. Such NIR-light-assisted nanoswimmers-enabled cell membrane poration possesses various advantages including active targeting, short time, and precision in single cells that conventional chemical and physical cell poration techniques could not achieve and, thus, provides considerable promise in a variety of biomedical applications such as gene delivery and artificial insemination.
Asunto(s)
Membrana Celular/metabolismo , Oro/química , Rayos Infrarrojos , Fenómenos Mecánicos/efectos de la radiación , Nanoestructuras/química , Polímeros/química , Polímeros/metabolismo , Fenómenos Biomecánicos/efectos de la radiación , Membrana Celular/efectos de la radiación , Células HeLa , Humanos , Análisis de la Célula IndividualRESUMEN
An increase in non-enzymatic collagen matrix cross-links, such as advanced glycation end-products (AGEs), is known to be a major complication in human mineralized tissues, often causing abnormal fractures. However, degradation of mechanical properties in relation to AGEs has not been fully elucidated at the material level. Here, we report nanoscale time-dependent deformation and dimensional recovery of human tooth dentin that has undergone glycation induced by x-ray irradiation. The reduction in enzymatic collagen cross-linking and the increased level of AGEs with concomitant growth of disordered collagen matrix diminished creep deformation recovery in the lower mineralized target region. However, the elevated AGEs level alone did not cause a reduction in time-dependent deformation and its recovery in the higher mineralized target region. In addition to the elevated AGEs level, the degradation of the mechanical properties of mineralized tissues should be assessed with care in respect to multiple parameters in the collagen matrix at the molecular level.
Asunto(s)
Dentina/metabolismo , Dentina/efectos de la radiación , Fenómenos Mecánicos/efectos de la radiación , Nanotecnología , Adolescente , Adulto , Fenómenos Biomecánicos/efectos de la radiación , Colágeno/metabolismo , Glicosilación/efectos de la radiación , Humanos , Cinética , Ensayo de Materiales , Adulto JovenRESUMEN
The use of synchrotron radiation micro-computed tomography (SR-microCT) is becoming increasingly popular for studying the relationship between microstructure and bone mechanics subjected to in situ mechanical testing. However, it is well known that the effect of SR X-ray radiation can considerably alter the mechanical properties of bone tissue. Digital volume correlation (DVC) has been extensively used to compute full-field strain distributions in bone specimens subjected to step-wise mechanical loading, but tissue damage from sequential SR-microCT scans has not been previously addressed. Therefore, the aim of this study is to examine the influence of SR irradiation-induced microdamage on the apparent elastic properties of trabecular bone using DVC applied to in situ SR-microCT tomograms obtained with different exposure times. Results showed how DVC was able to identify high local strain levels (>â¯10,000⯵ε) corresponding to visible microcracks at high irradiation doses (~â¯230â¯kGy), despite the apparent elastic properties remained unaltered. Microcracks were not detected and bone plasticity was preserved for low irradiation doses (~â¯33â¯kGy), although image quality and consequently, DVC performance were reduced. DVC results suggested some local deterioration of tissue that might have resulted from mechanical strain concentration further enhanced by some level of local irradiation even for low accumulated dose.
Asunto(s)
Hueso Esponjoso/diagnóstico por imagen , Hueso Esponjoso/efectos de la radiación , Ensayo de Materiales , Fenómenos Mecánicos/efectos de la radiación , Sincrotrones , Microtomografía por Rayos X/efectos adversos , Animales , Fenómenos Biomecánicos/efectos de la radiación , OvinosRESUMEN
Radiation therapy has been widely utilized as an effective method to eliminate malignant tumors and cancerous cells. However, subjection of healthy tissues and the related networks of blood vessels adjacent to the tumor area to irradiation is inevitable. The aim of this study was to investigate the consequent effects of fractionation radiotherapy on the mechanical characteristics of human umbilical vein endothelial cells (HUVECs) through alterations in cytoskeleton organization and cell and nucleus morphology. In order to simulate the clinical condition of radiotherapy, the HUVECs were exposed to the specific dose of 2â¯Gy for 1-4â¯times among four groups with incremental total dose from 2â¯Gy up to 8â¯Gy. Fluorescence staining was performed to label F-actin filaments and nuclei. Micropipette aspiration and standard linear solid model were employed to evaluate the elastic and viscoelastic characteristics of the HUVECs. Radiotherapy significantly increased cell elastic moduli. Due to irradiation, instantaneous and equilibrium Young's modulus were also increased. Radiotherapy diminished HUVECs viscoelastic behavior and shifted their creep compliance curves downward. Furthermore, gamma irradiation elevated the nuclei sizes and to a lesser extent the cells sizes resulting in the accumulation of F-actin filaments within the rest of cell body. Endothelial stiffening correlates with endothelial dysfunction, hence the results may be helpful when the consequent effects of radiotherapy are the focus of concern.
Asunto(s)
Células Endoteliales de la Vena Umbilical Humana/citología , Células Endoteliales de la Vena Umbilical Humana/efectos de la radiación , Fenómenos Mecánicos/efectos de la radiación , Radioterapia/efectos adversos , Fenómenos Biomecánicos/efectos de la radiación , Núcleo Celular/efectos de la radiación , Tamaño de la Célula/efectos de la radiación , Citoesqueleto/metabolismo , Citoesqueleto/efectos de la radiación , Fraccionamiento de la Dosis de Radiación , Elasticidad/efectos de la radiación , Humanos , Viscosidad/efectos de la radiaciónRESUMEN
The aim of the present study was to evaluate the radioprotective effects of melatonin on the biomechanical properties of bone in comparison to amifostine (WR-2721). Forty Sprague Dawley rats were divided equally into 5 groups namely; control (C), irradiation (R; single dose of 50 Gy), irradiation + WR-2721 (R + WR-2721; irradiation + 200 mg/kg WR-2721) radiation + melatonin 25 mg/kg (R + M25; irradiation + 25 mg/kg melatonin), and radiation + melatonin 50 mg/kg (R + M50; irradiation + 50 mg/kg melatonin). In order to measure extrinsic (organ-level mechanical properties of bone; the ultimate strength, deformation, stiffness, energy absorption capacity) and intrinsic (tissue-level mechanical properties of bone; ultimate stress, ultimate strain, elastic modulus, toughness) features of the bone, a three-point bending (TPB) test was performed for biomechanical evaluation. In addition, a bone mineral density (BMD) test was carried out. The BMD and extrinsic properties of the diaphyseal femur were found to be significantly higher in the R + M25 group than in group R (p < 0.05). A significant increase was observed in R + M50 (p < 0.05) in comparison to group R in the cross-sectional area of the femoral shaft and elastic modulus parameter. The protective effect of melatonin was similar to that of WR-2721. Thus, biomechanical quality of irradiated bone can be ameliorated by free radical scavenger melatonin.
Asunto(s)
Huesos/fisiopatología , Inflamación/complicaciones , Melatonina/farmacología , Estrés Oxidativo/efectos de los fármacos , Animales , Densidad Ósea/efectos de los fármacos , Huesos/efectos de los fármacos , Diáfisis/efectos de los fármacos , Relación Dosis-Respuesta en la Radiación , Fémur/efectos de los fármacos , Fémur/fisiopatología , Rayos gamma/efectos adversos , Fenómenos Mecánicos/efectos de los fármacos , Fenómenos Mecánicos/efectos de la radiación , Estrés Oxidativo/efectos de la radiación , Ratas , Ratas Sprague-DawleyRESUMEN
Biomechanical forces are central in tumor progression and response to treatment. This becomes more important in brain cancers where tumors are surrounded by tissues with different mechanical properties. Existing mathematical models ignore direct mechanical interactions of the tumor with the normal brain. Here, we developed a clinically relevant model, which predicts tumor growth accounting directly for mechanical interactions. A three-dimensional model of the gray and white matter and the cerebrospinal fluid was constructed from magnetic resonance images of a normal brain. Subsequently, a biphasic tissue growth theory for an initial tumor seed was employed, incorporating the effects of radiotherapy. Additionally, three different sets of brain tissue properties taken from the literature were used to investigate their effect on tumor growth. Results show the evolution of solid stress and interstitial fluid pressure within the tumor and the normal brain. Heterogeneous distribution of the solid stress exerted on the tumor resulted in a 35% spatial variation in cancer cell proliferation. Interestingly, the model predicted that distant from the tumor, normal tissues still undergo significant deformations while it was found that intratumoral fluid pressure is elevated. Our predictions relate to clinical symptoms of brain cancers and present useful tools for therapy planning.
Asunto(s)
Neoplasias Encefálicas/radioterapia , Fenómenos Mecánicos/efectos de la radiación , Modelos Biológicos , Fenómenos Biomecánicos/efectos de la radiación , Neoplasias Encefálicas/patología , Proliferación Celular/efectos de la radiación , Líquido Extracelular/efectos de la radiación , Humanos , Presión , Resultado del TratamientoRESUMEN
BACKGROUND: The effective porosity is an important quantitative parameter for food products that has a significant effect on taste and quality. It is challenging to quantify the apparent porosity of fried potato crisps as they have a thin irregularly shaped cross section containing oil and water. This study uses a novel micro-CT technique to determine the solid volume fraction and hence the effective porosity of three types of potato crisps: standard continuously fried crisps, microwaved crisps, and continuously fried 'kettle' crisps. RESULTS: It was found that continuously fried kettle crisps had the lowest effective porosity at 0.54, providing the desired crunchy taste and lower oil contents. Crisps produced using a microwave process designed to mimic the dehydration process of standard continuous fried crisps had an effective porosity of 0.65, which was very similar to the effective porosity of 0.63 for standard continuously fried crisps. The results were supported by the findings of a forced preference consumer test. CONCLUSION: The effective porosity affects the product taste and is therefore a critical parameter. This study shows that micro-CT analysis can be used to characterise the change in effective porosity of a thin irregularly shaped food product, caused by a change of cooking procedure. © 2016 Society of Chemical Industry.
Asunto(s)
Culinaria , Comida Rápida/análisis , Inspección de Alimentos/métodos , Calidad de los Alimentos , Tubérculos de la Planta/química , Solanum tuberosum/química , Algoritmos , Comportamiento del Consumidor , Grasas Insaturadas en la Dieta/análisis , Inglaterra , Comida Rápida/efectos de la radiación , Preferencias Alimentarias , Humanos , Fenómenos Mecánicos/efectos de la radiación , Microtecnología , Microondas/efectos adversos , Aceites de Plantas/análisis , Aceites de Plantas/química , Tubérculos de la Planta/efectos de la radiación , Porosidad/efectos de la radiación , Sensación , Solanum tuberosum/efectos de la radiación , Gusto , Tomografía Computarizada por Rayos XRESUMEN
OBJECTIVES: This study investigated the curing efficiency, the extent of atmospheric oxygen inhibition to the polymerization reaction and the mechanical properties of a new resin-infiltration system for caries treatment. METHODS: The curing efficiency was estimated by measuring the percentage degree of cure (%DC) of thin resin films (h: 150µm, Ø: 5mm, n=3), 10min after 40s exposure to a quartz halogen bulb (750mW/cm2) light curing unit (Optilux 501, Demetron/Kerr, USA), in the absence of O2, by micro ATR-FTIR spectroscopy. The extent of O2 inhibition on resin film setting (width in µm) was assessed by transmission optical microscopy on thin films (h: 150µm, Ø: â¼7mm, n=5) placed between two transparent cover slips and exposed to air from lateral sites. For each sample the extent of inhibition was measured at 5 different locations. The mechanical properties were tested employing Instrumented Indentation Testing according to ISO 14577:2002. Resin specimens (h: 2mm, Ø: 10mm, n=5) were prepared employing cylindrical teflon moulds enclosed in transparent matrix strips and glass slides as before. The measurements were performed employing a Vickers indenter attached to a universal hardness testing machine (ZHU2.5/Z2.5 plus test Xpert software, Zwick/Roell, Ulm, Germany). The parameters tested were Martens Hardness (MH), Vickers Hardness (VHN), Indentation Elastic Modulus (EIT) and elastic to total ratio of indentation work (ηIT). For all these tests, specimens of a conventional light-curing bonding resin (HB-Heliobond, Ivoclar-Vivadent, FL) prepared as above were used as control. Student t-test was used to identify statistically significant differences between the two materials in the parameters tested (a: 0.05). RESULTS: The results of the materials tested were: (a) [% DC]; IC: 57.4±1.5, HB: 59.8±2.4, (b) [Width of O2 inhibition/µm]; IC: 33.1±6.5, HB: 23.6±4.4, (c) [MH/N/mm(2)] IC; 116±16, HB: 261±35, (d) [VHN]; IC; 15.4±2.5, HB: 22.1±1.8, (e) [EIT/(GPa)]; IC; 2.3±0.4, HB: 7.5±0.5, and (g) [ηIT (%)] IC; 50.3±3.4, HB: 35.1±1.9. The IC presented no significant difference in terms of % DC, higher thickness of the inhibited layer, lower MH, VHN, EIT and greater ηIT values than HB. CONCLUSIONS AND CLINICAL SIGNIFICANT: The resin-infiltrating system for incipient caries treatment demonstrated the same curing efficiency with a conventional unfilled bonding resin, but exhibited higher extent of oxygen inhibition, lower hardness, lower elastic modulus and higher plastic to elastic indentation energy.
Asunto(s)
Caries Dental/terapia , Materiales Dentales/química , Materiales Dentales/efectos de la radiación , Curación por Luz de Adhesivos Dentales/métodos , Resinas Compuestas/química , Resinas Compuestas/efectos de la radiación , Luces de Curación Dental , Porcelana Dental/química , Dureza , Curación por Luz de Adhesivos Dentales/instrumentación , Fenómenos Mecánicos/efectos de la radiaciónRESUMEN
PURPOSE: The aim of this study was to investigate the effect of accelerated light aging on bond strength of a silicone elastomer to three types of denture resin. MATERIALS AND METHODS: A total of 60 single lap joint specimens were fabricated with auto-, heat-, and photopolymerized (n = 20) resins. An addition-type silicone elastomer (Episil-E) was bonded to resins treated with the same primer (A330-G). Thirty specimens served as controls and were tested after 24 hours, and the remaining were aged under accelerated exposure to daylight for 546 hours (irradiance 765 W/m(2) ). Lap shear joint tests were performed to evaluate bond strength at 50 mm/min crosshead speed. Two-way ANOVA and Tukey's test were carried out to detect statistical significance (p < 0.05). RESULTS: ANOVA showed that the main effect of light aging was the most important factor determining the shear bond strength. The mean bond strength values ranged from 0.096 to 0.136 MPa. The highest values were recorded for auto- (0.131 MPa) and photopolymerized (0.136 MPa) resins after aging. CONCLUSIONS: Accelerated light aging for 546 hours affects the bond strength of an addition-type silicone elastomer to three different denture resins. The bond strength significantly increased after aging for photo- and autopolymerized resins. All the bonds failed adhesively.
Asunto(s)
Resinas Acrílicas/efectos de la radiación , Adhesivos/efectos de la radiación , Fenómenos Mecánicos/efectos de la radiación , Procesos Fotoquímicos/efectos de la radiación , Resistencia al Corte/efectos de la radiación , Elastómeros de Silicona/efectos de la radiación , Resinas Acrílicas/química , Recubrimiento Dental Adhesivo/métodos , Luz , Ensayo de Materiales , Prótesis Maxilofacial , Elastómeros de Silicona/química , Luz SolarRESUMEN
Hydrogels are promising materials for cartilage repair, but the properties required for optimal functional outcomes are not yet known. In this study, we functionalized four materials that are commonly used in cartilage tissue engineering and evaluated them using in vitro cultures. Gelatin, hyaluronic acid, polyethylene glycol, and alginate were functionalized with methacrylic anhydride to make them photocrosslinkable. We found that the responses of encapsulated human chondrocytes were highly dependent on hydrogel type. Gelatin hydrogels supported cell proliferation and the deposition of a glycosaminoglycan rich matrix with significant mechanical functionality. However, cells had a dedifferentiated phenotype, with high expression of collagen type I. Chondrocytes showed the best redifferentiation in hyaluronic acid hydrogels, but the newly formed matrix was highly localized to the pericellular regions, and these gels degraded rapidly. Polyethylene glycol hydrogels, as a bioinert control, did not promote any strong responses. Alginate hydrogels did not support the deposition of new matrix, and the stiffness decreased during culture. The markedly different response of chondrocytes to these four photocrosslinkable hydrogels demonstrates the importance of material properties for chondrogenesis and extracellular matrix production, which are critical for effective cartilage repair.
Asunto(s)
Diferenciación Celular/efectos de los fármacos , Condrocitos/citología , Reactivos de Enlaces Cruzados/farmacología , Hidrogeles/farmacología , Luz , Fenómenos Mecánicos/efectos de los fármacos , Andamios del Tejido/química , Anciano , Diferenciación Celular/efectos de la radiación , Proliferación Celular/efectos de los fármacos , Proliferación Celular/efectos de la radiación , Forma de la Célula/efectos de los fármacos , Forma de la Célula/efectos de la radiación , Células Inmovilizadas/citología , Células Inmovilizadas/efectos de los fármacos , Células Inmovilizadas/metabolismo , Condrocitos/efectos de los fármacos , Condrocitos/metabolismo , Condrocitos/efectos de la radiación , Fuerza Compresiva/efectos de los fármacos , Fuerza Compresiva/efectos de la radiación , Matriz Extracelular/metabolismo , Matriz Extracelular/efectos de la radiación , Femenino , Técnica del Anticuerpo Fluorescente , Perfilación de la Expresión Génica , Glicosaminoglicanos/metabolismo , Humanos , Fenómenos Mecánicos/efectos de la radiación , Microtomografía por Rayos XRESUMEN
Photopolymerized hydrogels are extensively investigated for various tissue engineering applications, primarily due to their ability to form hydrogels in a minimally invasive manner. Although photocrosslinkable hydrogels provide necessary biological and chemical characteristics to mimic cellular microenvironments, they often lack sufficient mechanical properties. Recently, nanocomposite approaches have demonstrated potential to overcome these deficits by reinforcing the hydrogel network with. In this study, we investigate some physical, chemical, and biological properties of photocrosslinked poly(ethylene glycol) (PEG)-silica hydrogels. The addition of silica nanospheres significantly suppresses the hydration degree of the PEG hydrogels, indicating surface interactions between the silica nanospheres and the polymer chains. No significant change in hydrogel microstructure or average pore size due to the addition of silica nanospheres was observed. However, addition of silica nanospheres significantly increases both the mechanical strength and the toughness of the hydrogel networks. The biological properties of these nanocomposite hydrogels were evaluated by seeding fibroblast cells on the hydrogel surface. While the PEG hydrogels showed minimum cell adhesion, spreading and proliferation, the addition of silica nanospheres enhanced initial cell adhesion, promoted cell spreading and increased the metabolic activity of the cells. Overall, results indicate that the addition of silica nanospheres improves the mechanical stiffness and cell adhesion properties of PEG hydrogels and can be used for biomedical applications that required controlled cell adhesion.
Asunto(s)
Hidrogeles/farmacología , Luz , Fenómenos Mecánicos/efectos de los fármacos , Nanocompuestos/química , Nanosferas/química , Polietilenglicoles/farmacología , Dióxido de Silicio/farmacología , Animales , Adhesión Celular/efectos de los fármacos , Movimiento Celular/efectos de los fármacos , Movimiento Celular/efectos de la radiación , Proliferación Celular/efectos de los fármacos , Proliferación Celular/efectos de la radiación , Fuerza Compresiva/efectos de los fármacos , Fuerza Compresiva/efectos de la radiación , Reactivos de Enlaces Cruzados/farmacología , Fibroblastos/citología , Fibroblastos/efectos de los fármacos , Fibroblastos/efectos de la radiación , Cinética , Fenómenos Mecánicos/efectos de la radiación , Ratones , Células 3T3 NIH , Nanocompuestos/ultraestructura , Nanosferas/ultraestructura , Resistencia a la Tracción/efectos de los fármacos , Resistencia a la Tracción/efectos de la radiación , AguaRESUMEN
The purpose of this primer is to provide the clinical surgeon with a survey overview of the basic biochemistry of collagen and the methods and rationale of collagen cross-linking in the processing and preparation of bioprosthetics for surgical implantation. The author highlights the critical biologic factors, such as strength over time, integration, and rate, and type of remodeling, that are to an extent controllable by the cross-linking of collagen tissues so that clinicians may be better capable of understanding differences among the devices, which may be more applicable to their clinical indications.
Asunto(s)
Dermis Acelular , Colágeno/química , Reactivos de Enlaces Cruzados/farmacología , Procedimientos de Cirugía Plástica/métodos , Pared Abdominal/cirugía , Dermis Acelular/efectos de los fármacos , Dermis Acelular/efectos de la radiación , Animales , Colágeno/efectos de los fármacos , Colágeno/efectos de la radiación , Reacción a Cuerpo Extraño/etiología , Formaldehído/farmacología , Glutaral/farmacología , Rechazo de Injerto , Prótesis Valvulares Cardíacas , Humanos , Inflamación , Fenómenos Mecánicos/efectos de los fármacos , Fenómenos Mecánicos/efectos de la radiación , Microondas , Fotoquímica , Prótesis e Implantes , Conformación Proteica/efectos de los fármacos , Conformación Proteica/efectos de la radiación , Traumatismos de los Tejidos Blandos/cirugía , Resultado del Tratamiento , Rayos UltravioletaRESUMEN
Most cross-linking methods utilize chemistry or physical processes that are detrimental to cells and tissue development. Those that are not as harmful often do not provide a level of strength that ultimately meets the required application. The purpose of this work was to investigate the use of a ruthenium-sodium persulfate cross-linking system to form dityrosine in fibrin-based engineered tissue. By utilizing the tyrosine residues inherent to fibrin and cell-deposited proteins, at least 3-fold mechanical strength increases and 10-fold stiffness increases were achieved after cross-linking. This strengthening and stiffening effect was found to increase with culture duration prior to cross-linking such that physiologically relevant properties were obtained. Fibrin was not required for this effect as demonstrated by testing with collagen-based engineered tissue. Cross-linked tissues were implanted subcutaneously and shown to have minimal inflammation after 30 days, similar to non-cross-linked controls. Overall, the method employed is rapid, non-toxic, minimally inflammatory, and is capable of increasing strength and stiffness of engineered tissues to physiological levels.
Asunto(s)
Reactivos de Enlaces Cruzados/farmacología , Fibrina/farmacología , Luz , Rutenio/farmacología , Ingeniería de Tejidos/métodos , Animales , Catálisis/efectos de los fármacos , Catálisis/efectos de la radiación , Recuento de Células , Colágeno/farmacología , Matriz Extracelular/efectos de los fármacos , Matriz Extracelular/metabolismo , Fibrinógeno/metabolismo , Fibroblastos/citología , Fibroblastos/efectos de los fármacos , Humanos , Inmunohistoquímica , Implantes Experimentales , Fenómenos Mecánicos/efectos de los fármacos , Fenómenos Mecánicos/efectos de la radiación , Microscopía Electrónica de Rastreo , Ratas , Tejido Subcutáneo/efectos de los fármacos , Factores de Tiempo , Andamios del Tejido/química , Tripsina/metabolismoRESUMEN
Two series of poly(ether-ester)-based bis-functional macromers terminated with acrylate groups and a well-defined number of ester bonds were synthesized. One series had a chain of 1, 3 or 5 ester bonds at both ends of the central poly(ethylene glycol) block (molecular weight, about 1000), while the other had an alternating structure of oligo(ethylene glycol) each of them linked to two ester bonds, in which 6 or 10 ester bonds were incorporated equally in the macromer molecules and the total molecular weight was adjusted by about 1000. Irradiation of all poly(ether-ester) macromers mixed with camphorquinone resulted in the formation of gels. Gel yield increased and hydrophilic properties of the gels produced decreased with irradiation time. The elastic modulus of the gels decreased with the number of ester bonds. Upon incubation in a PBS solution (pH 8.04), all gels were gradually degraded with time. At 3 weeks of incubation, the degradation ratio increased linearly with the number of ester bonds per unit of molecular weight of the macromers. The order of in vivo degradation rates determined from weight loss was similar to that of the in vitro study. Thus, these poly(ether-ester) macromers may be useful for biodegradable biomaterials or tissue engineering scaffolds.
Asunto(s)
Geles/química , Luz , Poliésteres/síntesis química , Animales , Biodegradación Ambiental/efectos de la radiación , Hidrogeles/química , Concentración de Iones de Hidrógeno/efectos de la radiación , Hidrólisis/efectos de la radiación , Implantes Experimentales , Masculino , Fenómenos Mecánicos/efectos de la radiación , Poliésteres/química , Ratas , Ratas WistarRESUMEN
Biodegradable elastomeric poly(trimethylene carbonate) (PTMC) networks were efficiently formed by gamma irradiating the linear polymer in the presence of pentaerythritol triacrylate (PETA). The properties of networks formed upon irradiation of PTMC films containing (0, 1, 5 wt %) PETA as a cross-linking aid were evaluated. The gel contents and network densities increased with increasing PETA contents, irradiation dose, and initial polymer molecular weights. At a dose of 25 kGy, networks with gel fractions up to 0.96 could be obtained. The networks were noncytotoxic, had elastic moduli below 10.7 MPa and high tensile strengths of up to 37.7 MPa. The incorporation of PETA also improved the resistance to creep and to tear propagation significantly, resulting in permanent set values that were as low as 0.9% strain and tear strengths up to 9.3 ± 2.0 N/mm. Furthermore, the enzymatic erosion rates of the networks could be decreased from 12.0 ± 2.9 to 3.0 ± 1.6 µm/day. These biodegradable elastomeric PTMC networks may be utilized in a broad range of medical applications.
Asunto(s)
Acrilatos/química , Materiales Biocompatibles/síntesis química , Reactivos de Enlaces Cruzados/química , Dioxanos/química , Elastómeros/síntesis química , Rayos gamma , Polímeros/química , Glicoles de Propileno/química , Animales , Materiales Biocompatibles/química , Materiales Biocompatibles/toxicidad , Supervivencia Celular/efectos de los fármacos , Reactivos de Enlaces Cruzados/efectos de la radiación , Dioxanos/efectos de la radiación , Elastómeros/química , Elastómeros/toxicidad , Fenómenos Mecánicos/efectos de la radiación , Ratones , Peso Molecular , Células 3T3 NIH , Polímeros/efectos de la radiación , Dosis de Radiación , TemperaturaRESUMEN
The marine diazotrophic cyanobacterium Trichodesmium responds to elevated atmospheric CO(2) partial pressure (pCO(2)) with higher N(2) fixation and growth rates. To unveil the underlying mechanisms, we examined the combined influence of pCO(2) (150 and 900 microatm) and light (50 and 200 micromol photons m(-2) s(-1)) on Trichodesmium IMS101. We expand on a complementary study that demonstrated that while elevated pCO(2) enhanced N(2) fixation and growth, oxygen evolution and carbon fixation increased mainly as a response to high light. Here, we investigated changes in the photosynthetic fluorescence parameters of photosystem II, in ratios of the photosynthetic units (photosystem I:photosystem II), and in the pool sizes of key proteins involved in the fixation of carbon and nitrogen as well as their subsequent assimilation. We show that the combined elevation in pCO(2) and light controlled the operation of the CO(2)-concentrating mechanism and enhanced protein activity without increasing their pool size. Moreover, elevated pCO(2) and high light decreased the amounts of several key proteins (NifH, PsbA, and PsaC), while amounts of AtpB and RbcL did not significantly change. Reduced investment in protein biosynthesis, without notably changing photosynthetic fluxes, could free up energy that can be reallocated to increase N(2) fixation and growth at elevated pCO(2) and light. We suggest that changes in the redox state of the photosynthetic electron transport chain and posttranslational regulation of key proteins mediate the high flexibility in resources and energy allocation in Trichodesmium. This strategy should enable Trichodesmium to flourish in future surface oceans characterized by elevated pCO(2), higher temperatures, and high light.
Asunto(s)
Dióxido de Carbono/farmacología , Cianobacterias/efectos de los fármacos , Cianobacterias/efectos de la radiación , Luz , Fenómenos Mecánicos , Fijación del Nitrógeno/efectos de los fármacos , Fijación del Nitrógeno/efectos de la radiación , Aclimatación/efectos de los fármacos , Aclimatación/efectos de la radiación , Proteínas Bacterianas/metabolismo , Dióxido de Carbono/metabolismo , Clorofila/metabolismo , Cianobacterias/enzimología , Transporte de Electrón/efectos de los fármacos , Transporte de Electrón/efectos de la radiación , Metabolismo Energético/efectos de los fármacos , Fluorescencia , Fenómenos Mecánicos/efectos de los fármacos , Fenómenos Mecánicos/efectos de la radiación , Nitrogenasa/metabolismo , Fotosíntesis/efectos de los fármacos , Fotosíntesis/efectos de la radiación , Complejo de Proteína del Fotosistema II , Subunidades de Proteína/metabolismoRESUMEN
Collagen-based vascular substitutes represent in VTE a valid alternative for the replacement of diseased small-calibre blood vessels. In this study, collagen gel-based scaffolds were crosslinked combining modulation of pH and UV-C radiation. The effects on the mechanical properties, on the molecular structure and on cell viability and morphology were investigated. The mechanical response increased as a function of pH or UV-C dose and strongly depended on the test speed. Collagen molecular conformation resulted only slightly modified. While cell adhesion was not significantly altered, cell proliferation partially decreased in function of pH and UV-C. These findings suggest that UV-C treated collagen gels can represent an adequate substrate for VTE applications.