RESUMO
BACKGROUND: The conventional approaches to assess the potential cytotoxic effects of nanomaterials (NMs) mainly rely on in vitro biochemical assays. These assays are strongly dependent on the properties of the nanomaterials, for example; specific surface area (SSA), size, surface defects, and surface charge, and the host response. The NMs properties can also interfere with the reagents of the biochemical and optical assays leading to skewed interpretations and ambiguous results related to the NMs toxicity. Here, we proposed a structured approach for cytotoxicity assessment complemented with cells' mechanical responses represented as the variations of elastic Young's modulus in conjunction with conventional biochemical tests. Monitoring the mechanical properties responses at various times allowed understanding the effects of NMs to the filamentous actin cytoskeleton. The elastic Young's modulus was estimated from the force volume maps using an atomic force microscope (AFM). RESULTS: Our results show a significant decrease on Young's modulus, ~ 20%, in cells exposed to low concentrations of graphene flakes (GF), ~ 10% decrease for cells exposed to low concentrations of multiwalled carbon nanotubes (MWCNTs) than the control cells. These considerable changes were directly correlated to the disruption of the cytoskeleton actin fibers. The length of the actin fibers in cells exposed to GF was 50% shorter than the fibers of the cells exposed to MWCNT. Applying both conventional biochemical approach and cells mechanics, we were able to detect differences in the actin networks induced by MWCNT inside the cells and GF outside the cell's membrane. These results contrast with the conventional live/dead assay where we obtained viabilities greater than 80% after 24 h; while the elasticity dramatically decreased suggesting a fast-metabolic stress generation. CONCLUSIONS: We confirmed the production of radical oxygen species (ROS) on cells exposed to CBNs, which is related to the disruption of the cytoskeleton. Altogether, the changes in mechanical properties and the length of F-actin fibers confirmed that disruption of the F-actin cytoskeleton is a major consequence of cellular toxicity. We evidenced the importance of not just nanomaterials properties but also the effect of the location to assess the cytotoxic effects of nanomaterials.
Assuntos
Módulo de Elasticidade/efeitos dos fármacos , Grafite/toxicidade , Nanotubos de Carbono/toxicidade , Células 3T3 , Citoesqueleto de Actina/metabolismo , Actinas/metabolismo , Adsorção , Animais , Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Sobrevivência Celular/efeitos dos fármacos , Fibroblastos/citologia , Camundongos , Tamanho da Partícula , Propriedades de SuperfícieRESUMO
PURPOSE: In this study, we characterized rabbit corneas subjected to corneal cross-linking (CXL) with açaí extract compared with a riboflavin photo-stimulated procedure. MATERIALS AND METHODS: The corneas of the slaughterhouse rabbits were divided into three groups: control, consisting of untreated corneal samples; riboflavin/UVA, where corneas were treated with 0.1% riboflavin photo-stimulated at 365 nm as the standard protocol; and açaí, where the samples were subjected to 4% açaí extract for 0.5-2 h. After the CXL procedure, corneas of the three groups were characterized by analyzing their elastic modulus and thermal denaturation profile. RESULTS: The elastic modulus at 3% strain showed an approximately threefold increase in the riboflavin/UVA group and 10.5 times in the corneas treated with 4% açaí extract for 2 h, compared with the control group (p < 0.01). The denaturation temperature values of the two groups of crosslinked corneas increased significantly (p < 0.05) and were more pronounced in the açaí group. CONCLUSIONS: The açaí extract was effective in promoting CXL in rabbit corneas as characterized by the different techniques.
Assuntos
Colágeno/metabolismo , Substância Própria/metabolismo , Reagentes de Ligações Cruzadas , Euterpe/química , Fitoterapia , Extratos Vegetais/farmacologia , Animais , Córnea/efeitos dos fármacos , Córnea/metabolismo , Módulo de Elasticidade/efeitos dos fármacos , Fotoquimioterapia , Fármacos Fotossensibilizantes/farmacologia , Coelhos , Riboflavina/farmacologia , Raios UltravioletaRESUMO
Interactions between cells and microenvironments are essential to cellular functions such as survival, exocytosis and differentiation. Cell adhesion to the extracellular matrix (ECM) evokes a variety of biophysical changes in cellular organization, including modification of the cytoskeleton and plasma membrane. In fact, the cytoskeleton and plasma membrane are structures that mediate adherent contacts with the ECM; therefore, they are closely correlated. Considering that the mechanical properties of the cell could be affected by cell adhesion-induced changes in the cytoskeleton, the purpose of this study was to investigate the influence of the ECM on the elastic properties of fixed macrophage cells using atomic force microscopy. The results showed that there was an increase (~50%) in the Young's modulus of macrophages adhered to an ECM-coated substrate as compared with an uncoated glass substrate. In addition, cytochalasin D-treated cells had a 1.8-fold reduction of the Young's modulus of the cells, indicating the contribution of the actin cytoskeleton to the elastic properties of the cell. Our findings show that cell adhesion influences the mechanical properties of the plasma membrane, providing new information toward understanding the influence of the ECM on elastic alterations of macrophage cell membranes.
Assuntos
Membrana Celular/efeitos dos fármacos , Citoesqueleto/efeitos dos fármacos , Módulo de Elasticidade/efeitos dos fármacos , Fibronectinas/farmacologia , Macrófagos/citologia , Macrófagos/efeitos dos fármacos , Microscopia de Força Atômica , Animais , Adesão Celular/efeitos dos fármacos , Membrana Celular/ultraestrutura , Citoesqueleto/ultraestrutura , Macrófagos/ultraestrutura , Camundongos , Fatores de TempoRESUMO
We reported herein the study and characterization of films obtained by casting of chitosan solutions in perfluorinated acids, trifluoroacetic (TFA), perfluoropropionic (PFPA), and perfluorooctanoic (PFOA). The films were characterized by FTIR, solid state (13)C NMR, X-ray, AFM, contact angle, thermogravimetric effluent analysis by mass spectrometry, and rheology. The results showed a marked influence of chain length of the perfluorinated acids on the hydrophobic/hydrophilic ratio of the modified chitosan films which was evidenced by the different characteristics observed. The material that showed greater surface stability was chitosan-PFOA. Chitosan film with the addition of PFOA modifier became more hydrophobic, thus water vapor permeability diminished compared to chitosan films alone, this new material also depicted bacterial adhesion which, together with the features already described, proves its potential in applications for bioreactor coating.
Assuntos
Ácidos/farmacologia , Aderência Bacteriana/efeitos dos fármacos , Quitosana/farmacologia , Fluorocarbonos/farmacologia , Pseudomonas aeruginosa/fisiologia , Caprilatos/farmacologia , Linhagem Celular Tumoral , Contagem de Colônia Microbiana , Módulo de Elasticidade/efeitos dos fármacos , Humanos , Espectroscopia de Ressonância Magnética , Viabilidade Microbiana/efeitos dos fármacos , Microscopia de Força Atômica , Peso Molecular , Pseudomonas aeruginosa/efeitos dos fármacos , Pseudomonas aeruginosa/crescimento & desenvolvimento , Reologia/efeitos dos fármacos , Termodinâmica , Termogravimetria , Ácido Trifluoracético/farmacologia , Difração de Raios XRESUMO
New titanium alloys have been developed with the aim of utilizing materials with better properties for application as biomaterials, and Ti-Zr system alloys are among the more promising of these. In this paper, the influence of zirconium concentrations on the structure, microstructure, and selected mechanical properties of Ti-Zr alloys is analyzed. After melting and swaging, the samples were characterized through chemical analysis, density measurements, X-ray diffraction, optical microscopy, Vickers microhardness, and elasticity modulus. In-vitro cytotoxicity tests were performed on cultured osteogenic cells. The results showed the formation essentially of the α' phase (with hcp structure) and microhardness values greater than cp-Ti. The elasticity modulus of the alloys was sensitive to the zirconium concentrations while remaining within the range of values of conventional titanium alloys. The alloys presented no cytotoxic effects on osteoblastic cells in the studied conditions.
Assuntos
Materiais Biocompatíveis/farmacologia , Ligas Dentárias/farmacologia , Teste de Materiais , Titânio/farmacologia , Zircônio/farmacologia , Animais , Morte Celular/efeitos dos fármacos , Linhagem Celular , Proliferação de Células/efeitos dos fármacos , Módulo de Elasticidade/efeitos dos fármacos , Dureza/efeitos dos fármacos , Camundongos , Difração de Raios X , Zircônio/análiseAssuntos
Anemia Falciforme/sangue , Anemia Falciforme/tratamento farmacológico , Viscosidade Sanguínea/efeitos dos fármacos , Tetrazóis/administração & dosagem , Adulto , Cilostazol , Relação Dose-Resposta a Droga , Módulo de Elasticidade/efeitos dos fármacos , Feminino , Fibrinolíticos/administração & dosagem , Humanos , Masculino , Resultado do TratamentoRESUMO
INTRODUCTION: Propranolol (P) treatment exerts a preventive effect against the detrimental consequences to bone status in mildly chronically food-restricted growing rats (NGR) by an increment in cortical bone and by improving its spatial distribution. OBJECTIVE: To study the effect of beta-blocker on operational mechanism of bone mechanostat in an animal model of nutritional stress. MATERIAL AND METHODS: Weanling male Wistar rats were randomly assigned to four groups: control (C), C + P (CP), NGR and NGR + P (NGRP). C and CP rats were fed freely with the standard diet. NGR and NGRP rats received, for 4 weeks, 80% of the amount of food consumed by C and CP respectively, the previous day, corrected by body weight. Propranolol (7 mg/kg/day) was injected ip 5 days per week, for four weeks in CP and NGRP rats. C and NGR received saline injections at an identical dosage regimen. Body weight and length were determined during the experimental period. Dietary intake was registered daily. Animals were sacrificed after 4 weeks of food restriction. Immediately, cuadriceps, femur and tibiae from each animal were dissected and weighed, and histomorphometric and mechanical studies were performed. Serum a-CTX, osteocalcin, intact PTH, calcium and phosphorous were determined. Body protein (% prot) was measured in all groups. RESULTS: Food restriction induced detrimental effects on body and femoral growth, load-bearing capacity (Wf), % prot and cuadriceps weight in NGR us. C (p < 0.01). beta-blocker did not modify anthropometric and bone morphometric parameters in NGRP and CP us. NGR and C, respectively (p > 0.05). However, Wf NGRP vs. NGR was significantly higher (p < 0.01). alpha-CTX was significantly higher in NGR vs. C (p < 0.01). No significant differences were observed in alpha-CTX levels between CP, NGRP and C (p > 0.05). Serum osteocalcin, intact PTH, calcium and phospho- rous showed no significant difference between groups (p > 0.05). CONCLUSION: These results suggest that modeling increase in bone mass and strength in NGRP rats could be due to an anticatabolic interaction of the beta-blocker propranolol on operational mechanism of bone mechanostat in an animal model of nutritional stress.
Assuntos
Antagonistas Adrenérgicos beta/uso terapêutico , Doenças do Desenvolvimento Ósseo/prevenção & controle , Privação de Alimentos/fisiologia , Transtornos do Crescimento/prevenção & controle , Desnutrição/fisiopatologia , Propranolol/uso terapêutico , Antagonistas Adrenérgicos beta/farmacologia , Animais , Biomarcadores , Peso Corporal/efeitos dos fármacos , Doenças do Desenvolvimento Ósseo/sangue , Doenças do Desenvolvimento Ósseo/etiologia , Doenças do Desenvolvimento Ósseo/patologia , Remodelação Óssea/efeitos dos fármacos , Colágeno Tipo I/sangue , Módulo de Elasticidade/efeitos dos fármacos , Fêmur/efeitos dos fármacos , Fêmur/patologia , Transtornos do Crescimento/sangue , Transtornos do Crescimento/etiologia , Transtornos do Crescimento/patologia , Masculino , Desnutrição/tratamento farmacológico , Minerais/sangue , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/patologia , Tamanho do Órgão/efeitos dos fármacos , Hormônio Paratireóideo/sangue , Peptídeos/sangue , Propranolol/farmacologia , Proteínas/análise , Distribuição Aleatória , Ratos , Ratos Wistar , Suporte de CargaRESUMO
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
OBJECTIVE: The purpose of this study was to evaluate the effect of the bleaching agents on the elastic modulus of bovine demineralized dentin matrix (EMDM). MATERIALS AND METHODS: Eighty-five slices were obtained from 17 bovine teeth. The slices were divided randomly into five experimental groups (n = 17): unbleached control group (CG), 4% hydrogen peroxide (HP4), 4% hydrogen peroxide + 0.05% Ca (HP4 + Ca), 7.5% hydrogen peroxide + ACP (HP7.5) and 10% carbamide peroxide (CP10). The HP4, HP4 + Ca and CP10 groups were treated with the bleaching agents for 8 h/day (14 days), while the samples of HP7.5 group were exposed to bleaching agent for 30 min twice a day (14 days). The CG was kept in 100% humidity. After bleaching treatments, the enamel of the samples was removed and 85 dentin beams (0.5 × 1.7 × 7.0 mm) were prepared. Afterwards, the beams were immersed in 10% phosphoric acid solution (5 h) and rinsed with water (10 min). The beams were tested after 24 h, 7 and 14 days of storage in distilled water, using three-point bend method. Data were statistically analyzed using ANOVA and Fisher's test. RESULTS: All bleaching treatments reduced the EMDM. After 14 days post-bleaching, the EMDM increased for HP4 and HP4+Ca groups. CONCLUSIONS: The use of bleaching agents promoted a decrease in EMDM, which indicates that the bleaching treatment interacts with the dentin organic matrix. The EMDM measurement for the specimens of the 7.5% hydrogen peroxide group that were immersed in water at 14 days post-bleaching did not recover the EMDM values when compared to the control group.
Assuntos
Dentina/efeitos dos fármacos , Clareadores Dentários/toxicidade , Clareamento Dental/efeitos adversos , Análise de Variância , Animais , Peróxido de Carbamida , Bovinos , Distribuição de Qui-Quadrado , Módulo de Elasticidade/efeitos dos fármacos , Dureza/efeitos dos fármacos , Peróxido de Hidrogênio/administração & dosagem , Peróxido de Hidrogênio/toxicidade , Teste de Materiais , Peróxidos/administração & dosagem , Peróxidos/toxicidade , Maleabilidade/efeitos dos fármacos , Distribuição Aleatória , Ureia/administração & dosagem , Ureia/análogos & derivados , Ureia/toxicidadeRESUMO
The effect of dobutamine on carotid and brachial arteries compliance and the association of L-arginine as a potential nitric oxide pathway restorer were evaluated in patients with heart failure. Twenty-seven outpatients participated. Drugs used for the treatment of heart failure were withheld at least 24 hours before the study. The carotid and brachial artery diameters and hemodynamic variables were evaluated by ultrasonography and Doppler in baseline conditions, with dobutamine, with flow-mediated dilatation (FMD), and with placebo or L-arginine alone and associated with dobutamine. There was a significant increase in carotid peak blood flow with dobutamine when compared with that at baseline (P = 0.0001) or with L-arginine or placebo (P = 0.0001 and P = 0.0001, respectively), with increase of the cardiac index (P = 0.0001). Dobutamine did not increase carotid arterial compliance. FMD significantly increased the brachial peak blood flow (P = 0.0022) and the artery diameter (P = 0.0001). Dobutamine did not change the brachial artery diameter. Brachial peak blood flow was increased with dobutamine alone or associated with placebo or L-arginine comparing with L-arginine or placebo alone (P = 0.0168 and P = 0.0140, respectively), but was not increased compared with that at baseline. L-arginine infusion was not associated with changes in carotid, brachial, or in the cardiac index. We concluded that dobutamine increased carotid peak blood flow in patients with heart failure, although without changing the arterial compliance. The FMD of brachial artery was maintained, while brachial artery response to dobutamine infusion was less reliable. The carotid artery may be under the direct influence of the heart, while the brachial artery may be under predominant local control.