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1.
Int J Mol Sci ; 20(13)2019 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-31277289

RESUMO

Atomic force microscopy (AFM) combined with fluorescence microscopy has been used to quantify cytomechanical modifications induced by resveratrol (at a fixed concentration of 50 µM) in a breast cancer cell line (MCF-7) upon temporal variation. Cell indentation methodology has been utilized to determine simultaneous variations of Young's modulus, the maximum adhesion force, and tether formation, thereby determining cell motility and adhesiveness. Effects of treatment were measured at several time-points (0-6 h, 24 h, and 48 h); longer exposures resulted in cell death. Our results demonstrated that AFM can be efficiently used as a diagnostic tool to monitor irreversible morpho/nano-mechanical changes in cancer cells during the early steps of drug treatment.


Assuntos
Neoplasias da Mama/fisiopatologia , Adesão Celular/efeitos dos fármacos , Movimento Celular/efeitos dos fármacos , Módulo de Elasticidade/efeitos dos fármacos , Microscopia de Força Atômica/métodos , Resveratrol/farmacologia , Neoplasias da Mama/diagnóstico , Neoplasias da Mama/tratamento farmacológico , Feminino , Humanos , Células MCF-7 , Fenômenos Mecânicos/efeitos dos fármacos , Resveratrol/uso terapêutico
2.
Soft Matter ; 15(25): 5154-5162, 2019 Jun 26.
Artigo em Inglês | MEDLINE | ID: mdl-31192342

RESUMO

In vivo cell niches are complex architectures that provide a wide range of biochemical and mechanical stimuli to control cell behavior and fate. With the aim to provide in vitro microenvironments mimicking physiological niches, microstructured substrates have been exploited to support cell adhesion and to control cell shape as well as three dimensional morphology. At variance with previous methods, we propose a simple and rapid protein subtractive soft lithographic method to obtain microstructured polydimethylsiloxane substrates for studying stem cell adhesion and growth. The shape of adult renal stem cells and nuclei is found to depend predominantly on micropatterning of elastomeric surfaces and only weakly on the substrate mechanical properties. Differently, focal adhesions in their shape and density but not in their alignment mainly depend on the elastomer stiffness almost regardless of microscale topography. Local surface topography with concave microgeometry enhancing adhesion drives stem cells in a quasi-three dimensional configuration where stiffness might significantly steer mechanosensing as highlighted by focal adhesion properties.


Assuntos
Células-Tronco Adultas/citologia , Células-Tronco Adultas/efeitos dos fármacos , Elastômeros/farmacologia , Adesões Focais/efeitos dos fármacos , Adesões Focais/metabolismo , Fenômenos Mecânicos/efeitos dos fármacos , Fenômenos Biomecânicos/efeitos dos fármacos , Dimetilpolisiloxanos/farmacologia , Humanos , Nylons/farmacologia , Propriedades de Superfície
3.
Prog Biophys Mol Biol ; 148: 4-11, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31226307

RESUMO

Osteoarthritis (OA) is a prevalent joint disorder worldwide. Recent studies suggested that macrophages play an important role in the progression of OA. However, the detailed pathology related to macrophages is still ambiguous, especially where related to mechanotransduction. In this study, polycaprolactone (PCL) and Eucommia Ulmoides Gum (EUG) composite scaffolds were first fabricated by electrospinning. The stiffness of as-fabricated scaffolds was altered by adjusting the PCL-to-EUG ratio. The mechanical properties, structural characteristics and chemical composition of the scaffolds were investigated using various materials characterization techniques. The results show that stiffness of the scaffolds was in the same range as that of cartilage tissues with OA. Confocal microscopy and reverse transcription-polymerase chain reaction (RT-PCR) were performed to investigate the macrophages cultured on the scaffolds. Significant morphological changes of cells were observed on PCL/EUG scaffolds with different stiffness. The expression of inflammatory and fibrosis-related cytokines increases as scaffold stiffness decreases, similar to the trend observed in OA progression.


Assuntos
Eucommiaceae/química , Macrófagos/efeitos dos fármacos , Macrófagos/metabolismo , Fenômenos Mecânicos/efeitos dos fármacos , Gomas Vegetais/química , Poliésteres/química , Poliésteres/farmacologia , Animais , Materiais Biocompatíveis/química , Materiais Biocompatíveis/farmacologia , Fenômenos Biomecânicos/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Macrófagos/citologia , Camundongos , Células RAW 264.7
4.
Int J Pharm ; 559: 130-137, 2019 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-30599228

RESUMO

Cracking patterns in four kinds of granules, based on the common pharmaceutical excipient microcrystalline cellulose (MCC) and subject to compressive load, were examined. The initial pore structure and the location of initial failure under uniaxial compression were assessed using X-ray micro-computed tomography, whereas contact force development and onset of cracking under more complex compressive load were examined using a triaxial testing apparatus. Smoothed particle hydrodynamics (SPH) simulations were employed for numerical analysis of the stress distributions prior to cracking. For granules subject to uniaxial compression, initial cracking always occurred along the meridian and the precise location of the crack depended on the pore structure. Likewise, for granules subject to triaxial compression, the fracture plane of the primary crack was generally parallel to the dominant loading direction. The occurrence of cracking was highly dependent on the triaxiality ratio, i.e. the ratio between the punch displacements in the secondary and dominant loading directions. Compressive stresses in the lateral directions, induced by triaxial compression, prevented crack opening and fragmentation of the granule, something that could be verified by simulations. These results provide corroboration as well as further insights into previously observed differences between confined and unconfined compression of granular media.


Assuntos
Celulose/química , Força Compressiva/efeitos dos fármacos , Fenômenos Mecânicos/efeitos dos fármacos , Estresse Mecânico , Resistência à Tração/efeitos dos fármacos , Microtomografia por Raio-X/métodos
5.
Lab Chip ; 19(3): 464-474, 2019 01 29.
Artigo em Inglês | MEDLINE | ID: mdl-30570636

RESUMO

On-chip high-throughput phenotyping of single cells has gained a lot of interest recently due to the discrimination capability of label-free biomarkers such as whole-cell deformability and refractive index. Here we present on-chip refractive index cytometry (RIC) for whole-cell deformability at a high measurement rate. We have further exploited a previously published on-chip optical characterization method which enhances cellular discrimination through the refractive index measurement of single cells. The proposed on-chip RIC can simultaneously probe the cellular refractive index, effective volume and whole-cell deformability while reaching a measurement rate up to 5000 cells per second. Additionally, the relative position of the nucleus inside the cell is reflected by the asymmetry of the measured curve. This particular finding is confirmed by our numerical simulation model and emphasized by a modified cytoskeleton HL-60 cells model. Furthermore, the proposed device discriminated HL-60 derived myeloid cells such as neutrophils, basophils and promyelocytes, which are indistinguishable using flow cytometry. To our knowledge, this is the first integrated device to simultaneously characterize the cellular refractive index and whole-cell deformability, yielding enhanced discrimination of large myeloid cell populations.


Assuntos
Citometria de Fluxo/instrumentação , Dispositivos Lab-On-A-Chip , Fenômenos Mecânicos , Refratometria/instrumentação , Análise de Célula Única/instrumentação , Fenômenos Biomecânicos/efeitos dos fármacos , Diferenciação Celular/efeitos dos fármacos , Citocalasina B/farmacologia , Células HL-60 , Humanos , Fenômenos Mecânicos/efeitos dos fármacos
6.
J Mech Behav Biomed Mater ; 89: 99-106, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30267994

RESUMO

Wrist fractures can be difficult to treat due to advanced age of the patient, medical co-morbidities, and comminution of the bone. This study examines the effectiveness of two injectable glass polyalkenoate cements (GPCs), derived from two different glasses (A and B), as minimally invasive treatments for distal radius fractures. Twenty-seven fresh cadaveric radial pairs were tested either in compressive fatigue or to quasi-static compressive failure. The radii tested to failure had one pair fixated with a GPC while the other was left intact. The radii tested under fatigue had one pair fixated with a GPC and the other with a volar locking plate. A wedge osteotomy was used to simulate a severely comminuted fracture. When loaded to failure, the radii fixated with a GPC made from glass A or B were found to be, respectively, at least 57% and 62% as strong as their intact biological pair (95% Confidence Interval, Lower). Using a paired t-test, the radii fixated with either adhesive were found to be significantly stiffer than their biological pairs fixated with a volar locking plate for all cycles of fatigue loading. The adhesives under investigation demonstrate promise as treatment for distal radius fractures. In vivo investigations are warranted to determine the effect that the adhesives have on the bone remodelling process.


Assuntos
Adesivos/farmacologia , Fenômenos Mecânicos/efeitos dos fármacos , Fraturas do Rádio/terapia , Adesivos/química , Fenômenos Biomecânicos/efeitos dos fármacos , Força Compressiva/efeitos dos fármacos , Cimentos de Ionômeros de Vidro/química , Cimentos de Ionômeros de Vidro/farmacologia , Humanos , Teste de Materiais , Fraturas do Rádio/fisiopatologia
7.
Prog Biophys Mol Biol ; 144: 77-90, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-30197289

RESUMO

The F-actin cytoskeleton and its connection to the plasma membrane provide structure and shape of epithelial cells. In this study we focus on the impact of the F-actin cytoskeleton on the morphology and mechanical behaviour of confluent epithelial cells. F-actin depolymerisation was fostered by Latrunculin A, while depolymerisation was allayed by Jasplakinolide. The impact of drug treatment on cellular mechanics was measured using atomic force microscopy based active microrheology and force-indentation curves, while morphology was monitored by AFM imaging, electric cell-substrate impedance sensing (ECIS) experiments and fluorescence microscopy. A softening and fluidisation of the cells upon dissolution of F-actin was observed, accompanied by reduction of cell-substrate and cell-cell contacts and an altered topography. The strengthening of actin filaments upon Jasplakinolide treatment was mirrored in several mechanical properties. The largest impact was on the cellular viscosity. The cells were, however, capable of restoring their initial phenotypes, e.g., amount of actin, intercellular and cell-substrate interactions.


Assuntos
Actinas/metabolismo , Citoesqueleto/metabolismo , Células Epiteliais/citologia , Fenômenos Mecânicos , Animais , Fenômenos Biomecânicos/efeitos dos fármacos , Compostos Bicíclicos Heterocíclicos com Pontes/farmacologia , Citoesqueleto/efeitos dos fármacos , Depsipeptídeos/farmacologia , Cães , Células Epiteliais/efeitos dos fármacos , Cinética , Células Madin Darby de Rim Canino , Fenômenos Mecânicos/efeitos dos fármacos , Fenótipo , Tiazolidinas/farmacologia
8.
Nat Prod Res ; 33(7): 940-942, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-28278687

RESUMO

The application of algae to the most meaningful fields of our life, such as food, environment and energy, finds a further confirmation in the extension of this application to cultural heritage protection. In this letter, we present the results of a preliminary study testing how a polysaccharide extracted from algal matrix can restore degraded paper giving back it mechanical strength and chemical structure.


Assuntos
Fenômenos Mecânicos/efeitos dos fármacos , Papel , Extratos Vegetais/química , Cultura , Recuperação e Remediação Ambiental , Humanos , Papel/normas , Extratos Vegetais/farmacologia , Polissacarídeos/química , Polissacarídeos/farmacologia , Rodófitas/química
9.
J Biomech ; 83: 315-318, 2019 01 23.
Artigo em Inglês | MEDLINE | ID: mdl-30527389

RESUMO

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 5 min throughout 60 min of experiment after treatment with LPS from E. coli (100 µg/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 20 min (77%) till 60 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 , Humanos
10.
ACS Appl Mater Interfaces ; 10(44): 37820-37828, 2018 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-30360117

RESUMO

Three-dimensional (3D) bioprinting allows the fabrication of 3D structures containing living cells whose 3D shape and architecture are matched to a patient. The feature is desirable to achieve personalized treatment of trauma or diseases. However, realization of this promising technique in the clinic is greatly hindered by inferior mechanical properties of most biocompatible bioink materials. Here, we report a novel strategy to achieve printing large constructs with high printing quality and fidelity using an extrusion-based printer. We incorporate cationic nanoparticles in an anionic polymer mixture, which significantly improves mechanical properties, printability, and printing fidelity of the polymeric bioink due to electrostatic interactions between the nanoparticles and polymers. Addition of cationic-modified silica nanoparticles to an anionic polymer mixture composed of alginate and gellan gum results in significantly increased zero-shear viscosity (1062%) as well as storage modulus (486%). As a result, it is possible to print a large (centimeter-scale) porous structure with high printing quality, whereas the use of the polymeric ink without the nanoparticles leads to collapse of the printed structure during printing. We demonstrate such a mechanical enhancement is achieved by adding nanoparticles within a certain size range (<100 nm) and depends on concentration and surface chemistry of the nanoparticles as well as the length of polymers. Furthermore, shrinkage and swelling of the printed constructs during cross-linking are significantly suppressed by addition of nanoparticles compared with the ink without nanoparticles, which leads to high printing fidelity after cross-linking. The incorporated nanoparticles do not compromise biocompatibility of the polymeric ink, where high cell viability (>90%) and extracellular matrix secretion are observed for cells printed with nanocomposite inks. The design principle demonstrated can be applied for various anionic polymer-based systems, which could lead to achievement of 3D bioprinting-based personalized treatment.


Assuntos
Materiais Biocompatíveis/química , Bioimpressão/métodos , Matriz Extracelular/efeitos dos fármacos , Nanopartículas/química , Alginatos/química , Cátions/química , Sobrevivência Celular/efeitos dos fármacos , Humanos , Fenômenos Mecânicos/efeitos dos fármacos , Impressão Tridimensional , Reologia , Dióxido de Silício/química , Tecidos Suporte/química , Viscosidade/efeitos dos fármacos
11.
Biophys J ; 115(2): 386-397, 2018 07 17.
Artigo em Inglês | MEDLINE | ID: mdl-30021113

RESUMO

Cyclic interactions between myosin II motors and actin filaments driven by ATP turnover underlie muscle contraction and have key roles in the motility of nonmuscle cells. A remaining enigma in the understanding of this interaction is the relationship between the force-generating structural change and the release of the ATP-hydrolysis product, inorganic phosphate (Pi), from the active site of myosin. Here, we use the small molecular compound blebbistatin to probe otherwise hidden states and transitions in this process. Different hypotheses for the Pi release mechanism are tested by interpreting experimental results from in vitro motility assays and isolated muscle fibers in terms of mechanokinetic actomyosin models. The data fit with ideas that actomyosin force generation is preceded by Pi release, which in turn is preceded by two serial transitions after/coincident with cross-bridge attachment. Blebbistatin changes the rate limitation of the cycle from the first to the second of these transitions, uncovering functional roles of an otherwise short-lived pre-power stroke state that has been implicated by structural data.


Assuntos
Actinas/metabolismo , Compostos Heterocíclicos de 4 ou mais Anéis/farmacologia , Fenômenos Mecânicos/efeitos dos fármacos , Miosinas/metabolismo , Actinas/química , Animais , Fenômenos Biomecânicos/efeitos dos fármacos , Modelos Moleculares , Miosinas/química , Conformação Proteica , Coelhos
13.
J Mech Behav Biomed Mater ; 84: 74-87, 2018 08.
Artigo em Inglês | MEDLINE | ID: mdl-29751274

RESUMO

Mechanical forces throughout human mesenchymal stem cell (hMSC) spheroids (mesenspheres) play a predominant role in determining cellular functions of cell growth, proliferation, and differentiation through mechanotransductional mechanisms. Here, we introduce microparticle (MP) incorporation as a mechanical intervention method to alter tensional homeostasis of the mesensphere and explore MSC differentiation in response to MP stiffness. The microparticulate mechanoregulators with different elastic modulus (34 kPa, 0.6 MPa, and 2.2 MPa) were prepared by controlled crosslinking cell-sized microdroplets of polydimethylsiloxane (PDMS). Preparation of MP-MSC composite spheroids enabled us to study the possible effects of MPs through experimental and computational assays. Our results showed that MP incorporation selectively primed MSCs toward osteogenesis, yet hindered adipogenesis. Interestingly, this behavior depended on MP mechanics, as the spheroids that contained MPs with intermediate stiffness behaved similar to control MP-free mesenspheres with more tendencies toward chondrogenesis. However, by using the soft or stiff MPs, the MP-mesenspheres significantly showed signs of osteogenesis. This could be explained by the complex of forces which acted in the cell spheroid and, totally, provided a homeostasis situation. Incorporation of cell-sized polymer MPs as mechanoregulators of cell spheroids could be utilized as a new engineering toolkit for multicellular organoids in disease modeling and tissue engineering applications.


Assuntos
Dimetilpolisiloxanos/química , Dimetilpolisiloxanos/farmacologia , Fenômenos Mecânicos/efeitos dos fármacos , Células-Tronco Mesenquimais/citologia , Microesferas , Esferoides Celulares/citologia , Engenharia Tecidual , Materiais Biocompatíveis/química , Materiais Biocompatíveis/farmacologia , Fenômenos Biomecânicos/efeitos dos fármacos , Diferenciação Celular/efeitos dos fármacos , Linhagem Celular , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Condrogênese/efeitos dos fármacos , Humanos , Espaço Intracelular/efeitos dos fármacos , Espaço Intracelular/metabolismo , Células-Tronco Mesenquimais/efeitos dos fármacos , Esferoides Celulares/efeitos dos fármacos
14.
J Mech Behav Biomed Mater ; 84: 208-216, 2018 08.
Artigo em Inglês | MEDLINE | ID: mdl-29793158

RESUMO

Botulinum toxin type A (BTX-A) effects on the mechanics of non-injected antagonistic muscles are unknown. The aim was to test the following hypotheses in a rat model: BTX-A injected into gastrocnemius medialis (GM) and lateralis (GL) (1) decreases forces of the antagonistic tibialis anterior (TA) and extensor digitorum longus (EDL), (2) reduces length range of force exertion and (3) increases passive forces of the TA, and (4) changes inter-antagonistic and inter-synergistic epimuscular myofascial force transmission (EMFT). Two groups of Wistar rats were tested: BTX (0.1 units of BTX-A were injected to the GM and GL, each) and Control (saline injected). Five-days post, TA, EDL, GM-GL, and soleus distal and EDL proximal isometric forces were measured after TA lengthening. BTX-A exposure caused forces of all muscles to decrease significantly. TA and EDL active force drops (maximally by 37.3%) show inter-compartmental spread. Length range of force exertion of the TA did not change, but its passive force increased significantly (by 25%). The percentages of intramuscular connective tissue content of the TA and EDL was higher (BTX: 20.0 ±â€¯4.9% and 19.3 ±â€¯4.1% vs. control: 13.1 ±â€¯5.4% and 14.5 ±â€¯4.0%, respectively). Calf muscles' forces were not affected by TA length changes for both groups indicating lacking inter-antagonistic EMFT. However, BTX-A altered EDL proximo-distal force differences hence, inter-synergistic EMFT. A major novel finding is that BTX-A affects mechanics of non-injected antagonistic muscles in test conditions involving only limited EMFT. The effects indicating a stiffer muscle with no length range increase contradict some treatment aims, which require clinical testing.


Assuntos
Toxinas Botulínicas Tipo A/farmacologia , Fenômenos Mecânicos/efeitos dos fármacos , Músculo Esquelético/efeitos dos fármacos , Animais , Fenômenos Biomecânicos/efeitos dos fármacos , Tecido Conjuntivo/efeitos dos fármacos , Tecido Conjuntivo/metabolismo , Masculino , Músculo Esquelético/fisiologia , Ratos , Ratos Wistar
15.
J Contemp Dent Pract ; 19(3): 283-286, 2018 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-29603699

RESUMO

INTRODUCTION: Orthodontic treatment these days is increasing in demand, and therefore, it is relatively imperative for the orthodontist to prescribe the use of fluoride-containing products, such as mouthwashes and gels, to help prevent dental caries and maintain healthy oral health. The aim of the study was to assess and evaluate the effects of fluoride prophylactic agents on mechanical properties of nickel titanium (NiTi) wires during orthodontic treatment using scanning electron microscope (SEM). MATERIALS AND METHODS: We used the commercially available round preformed NiTi orthodontic archwire (3M company) and three different mouthwash solutions, i.e., Phos-Flur gel (1.1% sodium acidulated phosphate fluoride, APF, 0.5% w/v fluoride, pH = 5.1; Colgate Oral Pharmaceuticals) and Prevident 5000 (1.1% sodium fluoride neutral agent, 0.5% w/v fluoride, pH = 7; Colgate Oral Pharmaceuticals). All the specimens were subjected to a three-point bending test on a universal testing machine. To observe the surface morphological changes, one wire from each group was randomly selected and observed under a SEM. RESULTS: It was observed that there was not much difference in the values of both modulus of elasticity and yield strength obtained after loading of stress on the wires in all the three experimental conditions. A significant difference in both modulus of elasticity and yield strength was observed during unloading of stress. Further, when the surface characteristics were observed for all the specimens using SEM images, it was observed that NiTi wires treated with Phos-Flur showed large surface defects which appeared as round, pitted areas depicting corrosion, numerous white inclusions, and overall damaged surface structure of the wire as compared with the control. CONCLUSION: Thus, fluoridated mouthwashes are essential to maintain good oral hygiene and decrease instance of caries in patients undergoing orthodontic treatment. The prophylactic usage of topical fluoride agents on NiTi wire seems to diminish the mechanical properties of the orthodontic wire that could significantly affect future treatment outcomes. CLINICAL SIGNIFICANCE: It has been proved that fluoride mouthwashes/gels do affect the structural surface qualities and strength of wires used during the orthodontic treatment irrespective of the composition of the wires. Therefore, it is the responsibility of the clinician to prescribe these prophylactic agents carefully while keeping in mind their pH so that the overall result of the treatment may not be hampered and delayed due to change in properties of the wires used.


Assuntos
Ligas/uso terapêutico , Fluoretos/uso terapêutico , Fios Ortodônticos , Antibioticoprofilaxia/efeitos adversos , Antibioticoprofilaxia/métodos , Elasticidade/efeitos dos fármacos , Fenômenos Mecânicos/efeitos dos fármacos , Microscopia Eletrônica de Varredura , Fios Ortodônticos/efeitos adversos , Estresse Mecânico
16.
J Mech Behav Biomed Mater ; 82: 310-319, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29653380

RESUMO

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 fármacos
17.
J Mech Behav Biomed Mater ; 81: 214-221, 2018 05.
Artigo em Inglês | MEDLINE | ID: mdl-29550716

RESUMO

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 (p < 0.05) did not significantly difference from P11-4 treatment associated with SB, and also presented higher values than sound dentin-(SD/SB) (p < 0.01). DD treated with P11-4 associated with CSE did not differ from DD/CSE (p > 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 (p < 0.05). P11-4 and CPP-ACP increased significantly the wettability of demineralized dentin (p < 0.05); etching acid improved wettability for all groups (p < 0.05), whilst NaF did not affect the wettability of demineralized dentin (p > 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 (p < 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/farmacologia
18.
Biochim Biophys Acta Biomembr ; 1860(5): 953-959, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29408513

RESUMO

Cholesterol induced mechanical effects on artificial lipid bilayers are well known and have been thoroughly investigated by AFM force spectroscopy. However, dynamics of cholesterol impingement into bilayers at various cholesterol concentrations and their effects have not been clearly understood. In this paper we present, the effect of cholesterol as a function of its concentration in a simple single component dioleoylphosphatidylcholine (DOPC) bilayer. The nature of measured breakthrough forces on a bilayer with the addition of cholesterol, suggested that it is not just responsible to increase the mechanical stability but also introduces irregularities across the leaflets of the bilayer. This cholesterol induced asymmetry across the (in the inner and outer leaflets) bilayer is related to the phenomena of interleaflet coupling and is a function of cholesterol concentration probed by AFM can provide an unprecedented direction on mechanical properties of lipid membrane as it can be directly correlated to biophysical properties of a cell membrane.


Assuntos
Colesterol/química , Colesterol/farmacologia , Bicamadas Lipídicas/química , Conformação Molecular/efeitos dos fármacos , Fosfatidilcolinas/química , Materiais Biomiméticos/química , Fenômenos Mecânicos/efeitos dos fármacos , Lipídeos de Membrana/química , Microscopia de Força Atômica/métodos , Análise Espectral
19.
Int J Biol Macromol ; 111: 208-218, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29309873

RESUMO

Integrin-linked kinase (ILK), a ubiquitously expressed intracellular Ser/Thr protein kinase, plays a major role in the oncogenesis and tumour progression. The conformational stability and unfolding of kinase domain of ILK (ILK193-446) was examined in the presence of increasing concentrations of urea. The stability parameters of the urea-induced denaturation were measured by monitoring changes in [θ]222 (mean residue ellipticity at 222nm), difference absorption coefficient at 292nm (Δε292) and intrinsic fluorescence emission intensity at pH7.5 and 25±0.1°C. The urea-induced denaturation was found to be reversible. The protein unfolding transition occurred in the urea concentration range 3.0-7.0M. A coincidence of normalized denaturation curves of optical properties ([θ]222, Δε292 and λmax, the wavelength of maximum emission intensity) suggested that urea-induced denaturation of kinase domain of ILK is a two-state process. We further performed molecular dynamics simulation for 100ns to see the effect of urea on structural stability of kinase domain of ILK at atomic level. Structural changes with increasing concentrations of urea were analysed, and we observed a significant increase in the root mean square deviation, root mean square fluctuations, solvent accessible surface area and radius of gyration. A correlation was observed between in vitro and in silico studies.


Assuntos
Fenômenos Mecânicos/efeitos dos fármacos , Desnaturação Proteica/efeitos dos fármacos , Proteínas Serina-Treonina Quinases/química , Ureia/farmacologia , Dicroísmo Circular , Humanos , Simulação de Dinâmica Molecular , Conformação Proteica/efeitos dos fármacos , Domínios Proteicos/efeitos dos fármacos , Dobramento de Proteína/efeitos dos fármacos , Desdobramento de Proteína/efeitos dos fármacos , Ureia/química
20.
J Biomech ; 67: 84-90, 2018 01 23.
Artigo em Inglês | MEDLINE | ID: mdl-29249455

RESUMO

Colchicine is a drug commonly used for the treatment of gout, however, patients may sometimes encounter side-effects induced by taking colchicine, such as nausea, vomiting, diarrhea and kidney failure. In this regard, it is imperative to investigate the mechanism effects of colchicine on biological cells. In this paper, we present a method for the detection of mechanical properties of nephrocytes (VERO cells), hepatocytes (HL-7702 cells) and hepatoma cells (SMCC-7721 cells) in culture by atomic force microscope (AFM) to analyze the 0.1 µg/mL colchicine-induced effects on the nanoscale for two, four and six hours. Compared to the corresponding control cells, the biomechanical properties of the VERO and SMCC-7721 cells changed significantly and the HL-7702 cells did not considerably change after the treatment when considering the same time period. Based on biomechanical property analyses, the colchicine solution made the VERO and SMCC-7721 cells harder. We conclude that it is possible to reduce the division rate of the VERO cells and inhibit the metastasis of the SMCC-7721 cells. The method described here can be applied to study biomechanics of many other types of cells with different drugs. Therefore, this work provides an accurate and rapid method for drug screening and mechanical analysis of cells in medical research.


Assuntos
Colchicina/farmacologia , Fenômenos Mecânicos/efeitos dos fármacos , Microscopia de Força Atômica , Nanotecnologia , Animais , Fenômenos Biomecânicos/efeitos dos fármacos , Linhagem Celular Tumoral , Chlorocebus aethiops , Humanos , Células Vero
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