RESUMO
The lipid bilayer is the basis of the structure and function of the cell membrane. The study of the molecular phenomena that affect biological membranes has a great impact on the understanding of cellular physiology. To understand these phenomena, it has become increasingly necessary to develop simple synthetic models that allow the most basic details of such processes to be reproduced. In this short communication, we took advantage of the properties of two well-established lipid model systems, GUVs and SLBs, with compositions mimicking the cell membrane present in mammals and bacteria, to study the thermotropic phase behavior of lipids as well as the effect of daptomycin, a cyclic lipopeptide used as an antibiotic. The study of mechanical and thermodynamical properties of these model systems could contribute to establish a theoretical framework to develop more efficient strategies for biological control.
Assuntos
Antibacterianos/farmacologia , Membrana Celular/química , Membrana Celular/efeitos dos fármacos , Daptomicina/farmacologia , Fenômenos Mecânicos/efeitos dos fármacos , Modelos Moleculares , Lipossomas Unilamelares/química , Fenômenos Biomecânicos/efeitos dos fármacos , Conformação MolecularRESUMO
PURPOSE: To investigate the mechanical performance and fracture reliability of new generation, bulk-fill resin composites of different viscosities. METHODS: Forty sound maxillary premolars were prepared into Class I cavities comprised of 5â¯mm widthâ¯×â¯5â¯mm lengthâ¯×â¯5â¯mm thickness. The teeth were randomly allocated into four groups (nâ¯=â¯10) according to the restorative material: Negative control - without restoration; Positive control - conventional resin composite (Opallis; FGM) was applied using increments of up to 2.0â¯mm-thick; Bulk-Regular - bulk-fill resin composite of regular viscosity (Opus Bulk Fill; FGM) was applied using a single increment of 5â¯mm-thick; and Bulk-Flow - a low-viscosity bulk-fill resin composite (Opus Bulk Fill Flow; FGM) was applied as the first increment with â¼3.5â¯mm-thick, followed by two final increments of Opallis (â¼1.5â¯mm-thick). The teeth were stored at 37⯰C, for 24â¯h, and submitted to a mechanical testing machine (DL500; EMIC) under a compressive loading. Work of fracture (Wf) was also obtained. All data were analyzed using ANOVA and Tukey (αâ¯=â¯5%). Reliability of restorations and probability of failure were analyzed by Weibull analysis. RESULTS: The non-restored teeth showed the weakest behavior of the study. All the restored groups demonstrated similar mechanical properties to each other (pâ¯≥â¯0.242). The positive and negative controls failed exclusively within the cohesiveness of enamel/dentin, whereas the bulk-fill-based restorations showed a mixture of cohesive and mixed failures. The restored groups showed an overall similar reliability, although the Bulk-Regular group demonstrated greater characteristic strength than the positive control. CONCLUSION: The novel bulk-fill resin composites of low and regular viscosities show promising application in the restoration of Class I cavities in premolars, demonstrating similar mechanical performance and reliability as compared with restorations prepared using conventional resin composites. From the bulk-fill materials, the version with regular viscosity presented the greatest compliant behavior of the study.
Assuntos
Dente Pré-Molar/efeitos dos fármacos , Fenômenos Mecânicos/efeitos dos fármacos , Cimentos de Resina/farmacologia , Fenômenos Biomecânicos/efeitos dos fármacos , Humanos , Teste de Materiais , Viscosidade/efeitos dos fármacosRESUMO
INTRODUCTION: Application of lipopolysaccharide (LPS) is a widely employed model to mimic acute respiratory distress syndrome (ARDS). Available data regarding LPS-induced biomechanical changes on pulmonary epithelial cells are limited only to P. aeruginosa LPS. Considering that LPS from different bacteria could promote a specific mechanical response in epithelial cells, we aim to assess the effect of E. coli LPS, widely employed as a model of ARDS, in the biomechanics of alveolar epithelial cells. METHODS: Young's modulus (E) of alveolar epithelial cells (A549) was measured by atomic force microscopy every 5â¯min throughout 60â¯min of experiment after treatment with LPS from E. coli (100⯵g/mL). The percentage of cells presenting actin stress fibers (F-actin staining) was also evaluated. Control cells were treated with culture medium and the values obtained were compared with LPS-treated cells for each time-point. RESULTS: Application of LPS induced significant increase in E after 20â¯min (77%) till 60â¯min (104%) in comparison to controls. Increase in lung epithelial cell stiffness induced by LPS was associated with a higher number of cells presenting cytoskeletal remodeling. CONCLUSIONS: The observed effects of E. coli LPS on alveolar epithelial cells suggest that this widely-used LPS is able to promote a quick formation of actin stress fibers and stiffening cells, thereby facilitating the disruption of the pulmonary epithelial barrier.
Assuntos
Células Epiteliais Alveolares/efeitos dos fármacos , Escherichia coli/química , Lipopolissacarídeos/farmacologia , Fenômenos Mecânicos/efeitos dos fármacos , Células A549 , Células Epiteliais Alveolares/metabolismo , Fenômenos Biomecânicos/efeitos dos fármacos , HumanosRESUMO
Fibrin and hyaluronic acid are important components of the provisional wound matrix. Through interactions with fibroblasts, they provide biophysical cues that regulate the viscoelastic properties of the extracellular matrix. To understand the roles of fibrin and hyaluronic acid in a collagenous environment, we used fibroblast populated collagen lattices (collagen, collagen-fibrin, and collagen-hyaluronic acid). Compared with collagen and collagen-hyaluronic acid cultures, collagen-fibrin cultures showed less contraction, which is correlated with increased elastic (G') and complex (|G*|) moduli, and reduced proportions of dendritic fibroblasts, despite increased αv integrin expression. Stiffness decreased during culture in collagen-fibrin environment, meanwhile phase shift (δ) values increased, clearly associated with the rise in fibrinolytic and gelatinolytic activities. These processes changed the viscoelastic properties of the system toward G' and |G*| values observed on day 5 in collagen cultures. Although less collagen turnover was observed in collagen-fibrin cultures than in collagen and collagen-hyaluronic acid cultures, collagen neosynthesis was apparently insufficient to contribute to the overall viscoelastic properties of the system. Collagen-hyaluronic acid cultures showed very limited changes during time. Firstly, they exhibited the highest δ values, suggesting an increase in the viscous behavior due to the hygroscopic properties of hyaluronic acid. These results showed that fibrin and hyaluronic acid not only affect differently the viscoelastic properties of the culture, they can tune fibroblastic activity by regulating cell attachment and extracellular matrix remodeling.
Assuntos
Colágeno/metabolismo , Fibrina/farmacologia , Fibroblastos/efeitos dos fármacos , Fibroblastos/metabolismo , Ácido Hialurônico/farmacologia , Fenômenos Mecânicos/efeitos dos fármacos , Fenômenos Biomecânicos/efeitos dos fármacos , Elasticidade/efeitos dos fármacos , Matriz Extracelular/efeitos dos fármacos , Matriz Extracelular/metabolismo , Fibroblastos/citologia , Humanos , Viscosidade/efeitos dos fármacosRESUMO
Bonding to demineralized dentin of a diseased tooth has shown to be a significant clinical issue. This study evaluated the effect of 0.2% NaF-(NaF), MI Paste™-(CPP-ACP) and the self-assembling peptide 'P11-4' (Ace-QQRFEWEFEQQ-NH2) contained in Curodont™ Repair, have on microtensile bond strength-(µTBS) of two different adhesive systems (Adper™ Single Bond-(SB) or Clearfil™ SE Bond (CSE)) and wettability of demineralized dentin slices after remineralising agents were applied. The highest µTBS were found for the demineralized dentin-(DD) treated with CPP-ACP; both adhesives systems (pâ¯<â¯0.05) did not significantly difference from P11-4 treatment associated with SB, and also presented higher values than sound dentin-(SD/SB) (pâ¯<â¯0.01). DD treated with P11-4 associated with CSE did not differ from DD/CSE (pâ¯>â¯0.05). The NaF treatment associated with CSE recovered the bond strength values of SD/CSE and associated with CSE demonstrated lower µTBS than other groups, although significantly higher than DD (pâ¯<â¯0.05). P11-4 and CPP-ACP increased significantly the wettability of demineralized dentin (pâ¯<â¯0.05); etching acid improved wettability for all groups (pâ¯<â¯0.05), whilst NaF did not affect the wettability of demineralized dentin (pâ¯>â¯0.05). Morphological analysis of the dentin surface and dentin-resin interface revealed unique features of the applied remineralizing agent. The results indicated that self-assembling peptide P11-4 associated with SB and CPP-ACP associated with SB or CSE significantly enhanced the bond strength to demineralized dentin (pâ¯<â¯0.05). We conclude that by modifying the dentine surface and restoring conditions found on sound dentin, this can enhance the interfacial bonding.
Assuntos
Dentina/efeitos dos fármacos , Dentina/metabolismo , Fenômenos Mecânicos/efeitos dos fármacos , Minerais/metabolismo , Sequência de Aminoácidos , Fenômenos Biomecânicos/efeitos dos fármacos , Fosfatos de Cálcio/farmacologia , Humanos , Oligopeptídeos/química , Oligopeptídeos/farmacologia , Fluoreto de Sódio/farmacologiaRESUMO
This study aimed to evaluate the effects of different synthetic and natural-derived root canal irrigants (6% sodium hypochlorite [NaOCl], 6% calcium hypochlorite [Ca(OCl)2] and 6.5% grape seed extract [GSE]) on dentin mechanical properties (flexural strength, ultimate tensile strength [UTS] and fracture resistance). Rectangular-shaped beams and hourglass-shaped sections obtained from mid-coronal and root dentin were treated with 6% NaOCl, 6% Ca(OCl)2 or 6.5% GSE for 30 min. The irrigant solutions were replaced every 5 min. Then, the dentin specimens were rinsed with distilled water (DW) followed by incubation with 17% EDTA for 1 min, and thoroughly rinsed with DW again. Specimens from the control group were tested without prior irrigation. After treatment with the irrigants, dentin beams were used to assess the flexural strength (n = 10) while UTS was evaluated using the root dentin hourglass-shaped sections (n = 10). Similarly, roots with 1 mm of dentinal wall thickness were obtained from human teeth and treated with the same irrigant solutions (n = 10). A compressive loading was applied to the coronal surfaces of roots until fracture. The values of each mechanical test were statistically analyzed individually by one-way ANOVA followed by Tukey HSD test (P < 0.05). NaOCl significantly reduced the mechanical properties of dentin in all mechanical tests (P < 0.05) and no statistical difference was found among Ca(OCl)2, GSE and control group (P > 0.05). It can be concluded that Ca(OCl)2 and GSE may be alternative irrigant solutions, since they do not negatively affect the dentin mechanical properties.
Assuntos
Compostos de Cálcio/farmacologia , Dentina/efeitos dos fármacos , Extrato de Sementes de Uva/farmacologia , Irrigantes do Canal Radicular/farmacologia , Hipoclorito de Sódio/farmacologia , Análise do Estresse Dentário/métodos , Humanos , Teste de Materiais , Fenômenos Mecânicos/efeitos dos fármacos , Estresse Mecânico , Resistência à Tração/efeitos dos fármacos , Dente/efeitos dos fármacos , Dente/fisiologia , Fraturas dos Dentes/prevenção & controleRESUMO
Objetivo: o objetivo do presente estudo foi avaliar in vitro a microin ltraçaÌo coronaÌria em cavidades complexas seladas com materiais restauradores temporaÌrios (MRT). MeÌtodos: as cavidades foram preparadas em 60 preÌ-molares superiores extraiÌdos de humanos, e os espeÌcimes foram divididos em treÌs grupos, de acordo com o MRT utilizado: G1 = IRM; G2 = Coltosol; G3 = Fill Magic Tempo. TreÌs dentes serviram como controle negativo e naÌo tiveram cavidades preparadas. Antes do selamento das cavidades com o MRT, uma esponja de colaÌgeno foi deixada dentro da caÌmara pulpar, para avaliaçaÌo binaÌria da penetraçaÌo do corante. Dez dentes de cada grupo naÌo foram submetidos aÌ açaÌo de termociclagem e força mecaÌnica oclusal, enquanto outros dez foram submetidos a essas açoÌes. A amostra foi imersa em corante Rodamina B a 0,5% a 37°C, por 7 dias. Resultados: todos os dentes examinados (100%), exceto os controles negativos, apresentaram in ltraçaÌo pelo corante. Todos os dentes selados com Coltosol (100%) fraturaram apoÌs ensaio mecaÌnico, enquanto aqueles com IRM e Fill Magic Tempo mantiveram-se intactos macroscopicamente. A açaÌo ou naÌo das intempeÌries teÌrmicas e mecaÌnicas naÌo interferiu na penetraçaÌo do corante nas amostras no presente estudo. ConclusaÌo: nenhum dos materiais testados impediu a in ltraçaÌo do corante. No entanto, o Coltosol naÌo deve ser indicado para utilizaçaÌo em cavidades complexas onde haÌ incideÌncia de forças mastigatoÌrias, devido ao seu alto iÌndice de fratura.
Assuntos
Humanos , Corantes , Infiltração Dentária/diagnóstico , Materiais Dentários/uso terapêutico , Fenômenos Mecânicos/efeitos dos fármacosRESUMO
The present study investigates the potential use of non-catalyzed water-soluble blocked polyurethane prepolymer (PUP) as a bifunctional cross-linker for collagenous scaffolds. The effect of concentration (5, 10, 15 and 20%), time (4, 6, 12 and 24 h), medium volume (50, 100, 200 and 300%) and pH (7.4, 8.2, 9 and 10) over stability, microstructure and tensile mechanical behavior of acellular pericardial matrix was studied. The cross-linking index increased up to 81% while the denaturation temperature increased up to 12 °C after PUP crosslinking. PUP-treated scaffold resisted the collagenase degradation (0.167±0.14 mmol/g of liberated amine groups vs. 598±60 mmol/g for non-cross-linked matrix). The collagen fiber network was coated with PUP while viscoelastic properties were altered after cross-linking. The treatment of the pericardial scaffold with PUP allows (i) different densities of cross-linking depending of the process parameters and (ii) tensile properties similar to glutaraldehyde method.
Assuntos
Reagentes de Ligações Cruzadas/farmacologia , Teste de Materiais , Fenômenos Mecânicos/efeitos dos fármacos , Pericárdio/efeitos dos fármacos , Poliuretanos/farmacologia , Água/química , Animais , Cálcio/metabolismo , Varredura Diferencial de Calorimetria , Bovinos , Módulo de Elasticidade/efeitos dos fármacos , Matriz Extracelular/efeitos dos fármacos , Matriz Extracelular/ultraestrutura , Glutaral/farmacologia , Concentração de Íons de Hidrogênio/efeitos dos fármacos , Pericárdio/ultraestrutura , Fósforo/metabolismo , Estresse Mecânico , Temperatura , Resistência à Tração/efeitos dos fármacos , Fatores de TempoRESUMO
Hydroxyapatite (HAP)-containing poly-ε-caprolactone (PCL)-polydiisopropyl fumarate (PDIPF) composite (Blend) was developed as an alternative for bone tissue engineering. The physicochemical, mechanical and biocompatibility properties of these composites were evaluated using two osteoblast-like cell lines (UMR106 and MC3T3E1) and compared with the blend without HAP and PCL/HAP films. The increment in the elastic modulus and the decrease in the elongation-at-break of Blend-HAP suggest that the mechanical properties of the HAP scaffolds have improved significantly. The addition of HAP to both PCL and Blend significantly improves the cell biocompatibility and osteogenicity of the scaffolds. Evidence for this notion is based in several observations: (a) HAP-polymer increases proliferation of osteoblastic cells; (b) HAP included in the blend increases the ALP expression in UMR106 cells; (c) HAP-Blend increases the type-I collagen production in both cell lines, and d) higher levels of the osteogenic transcription factor Runx-2 were detected when MC3T3E1 osteoblasts were induced to differentiate and mineralize on HAP-polymer scaffolds. In conclusion, a novel biocompatible HAP-Blend composite with uniform dispersion of semi-nano HAP particles and good interphase compatibility has been prepared successfully. The development of HAP-Blend composite, with improved physical, mechanical and osteoinductive properties, may potentially be used in bone tissue-engineering applications.
Assuntos
Regeneração Óssea/efeitos dos fármacos , Osso e Ossos/fisiologia , Durapatita/farmacologia , Fumaratos/farmacologia , Poliésteres/farmacologia , Polímeros/farmacologia , Engenharia Tecidual/métodos , Alicerces Teciduais/química , Animais , Materiais Biocompatíveis/farmacologia , Biomarcadores/metabolismo , Osso e Ossos/efeitos dos fármacos , Linhagem Celular , Proliferação de Células/efeitos dos fármacos , Subunidade alfa 1 de Fator de Ligação ao Core/metabolismo , Teste de Materiais , Fenômenos Mecânicos/efeitos dos fármacos , Camundongos , Microscopia Eletrônica de Varredura , Osteoblastos/citologia , Osteoblastos/efeitos dos fármacos , Osteoblastos/metabolismo , Ratos , Espectroscopia de Infravermelho com Transformada de FourierRESUMO
The possibility of producing valued devices from low cost natural resources is a subject of broad interest. The present study explores the preparation and characterization of silk fibroin dense membranes using waste silk fibers from textile processing. Morphology, crystallinity, thermal resistance and cytotoxicity of membranes as well as the changes on the secondary structure of silk fibroin were analyzed after undergoing treatment with ethanol. Membranes presented amorphous patterns as determined via X-ray diffraction. The secondary structure of silk fibroin on dense membranes was either random coil (silk I) or beta-sheet (silk II), before and after ethanol treatment, respectively. The sterilized membranes presented no cytotoxicity to endothelial cells during in vitro assays. This fact stresses the material potential to be used in the fabrication of biomaterials, as coatings of cardiovascular devices and as membranes for wound dressing or drug delivery systems.
Assuntos
Materiais Biocompatíveis/síntese química , Biotecnologia/métodos , Etanol/farmacologia , Fibroínas/química , Membranas Artificiais , Resíduos/análise , Animais , Células CHO , Varredura Diferencial de Calorimetria , Proliferação de Células/efeitos dos fármacos , Cricetinae , Cricetulus , Células Endoteliais/citologia , Células Endoteliais/efeitos dos fármacos , Fibroínas/ultraestrutura , Humanos , Fenômenos Mecânicos/efeitos dos fármacos , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura , Resistência à Tração/efeitos dos fármacos , Termogravimetria , Difração de Raios XRESUMO
OBJECTIVES: The aim of this study was to carry out a review on the effect of sodium hypochlorite (NaOCl) on the mechanical properties of root dentine. DATA/SOURCES: The authors searched the Cochrane Library, Embase, PubMed and the Web of Science for papers published from 1984 to 2008. The main search terms used were: dentine, root canal dentine, sodium hypochlorite, mechanical analysis, elastic modulus, hardness, roughness, flexural strength, compressive strength. STUDY SELECTION: The inclusion criteria were studies that evaluated the effect of NaOCl solution, used as an irrigant in endodontics, on the mechanical properties of root dentine. Those studies that were considered to be unrelated to the question addressed, that had investigated NaOCl as a deproteinizing agent, had not evaluated the effect of NaOCl on the mechanical properties of dentine, and that indirectly verified the effect of NaOCl on endodontically treated teeth were excluded. The selected papers were assigned to a score (A-C), according to predetermined criteria. A total of 16 papers were selected, and nine papers were included in the critical appraisal. Five papers were classified as grade A, 4 as grade B, and no paper was classified as grade C. CONCLUSIONS: Based on this review, the authors suggest that there is strong evidence showing that sodium hypochlorite adversely alters the mechanical properties of root dentine, when used as an endodontic irrigant.