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1.
Zhongguo Yi Xue Ke Xue Yuan Xue Bao ; 42(1): 73-79, 2020 Feb 28.
Artigo em Chinês | MEDLINE | ID: mdl-32131943

RESUMO

Objective To explore the value of trans-rectal shear wave elastic mode combined with elastic modulus in the diagnosis of prostate cancer and establish a new method for the evaluation of prostate with trans-rectal shear wave elastography(SWE). Methods The typical findings of trans-rectal ultrasound(US)and SWE in 79 patients with prostate cancer(n=41)and benign prostatic hyperplasia(BPH)(n=38)confirmed by surgery or US-guided biopsy were analyzed retrospectively.Their diagnostic value were evaluated with the pathological results as the golden standards. Results Three or more malignant features detected by conventional trans-rectal US(χ 2=42.5,P<0.001)and asymmetrical SWE mode(χ 2=54.2,P<0.001)showed statistically significant difference in prostate cancer and BPH groups.The elastic modulus of Emean and Emax in the prostate cancer group were(92.8±21.5)and(114.2±29.8)kPa,which were significantly higher than those in the BPH group [(56.7±14.0)(t=-8.8,P<0.001)and(68.4±17.2)kPa(t=-8.3,P<0.001)].The receiver-operating characteristic(ROC)curve with Logistic regression showed that the elastic model combined elastic modulus had the largest area under ROC curve and the highest diagnosis efficiency of prostate cancer,with the cutoff value of 0.45.The diagnosis sensitivity,specificity,positive predictive value,negative predictive value,and accuracy of the combination were 95.1%,89.5%,90.7%,94.4%,and 92.4%,respectively. Conclusion Combination of SWE mode and elastic modulus is more valuable than elastic modulus alone in the diagnosis of prostate cancer.


Assuntos
Módulo de Elasticidade , Técnicas de Imagem por Elasticidade , Neoplasias da Próstata/diagnóstico , Humanos , Masculino , Hiperplasia Prostática/diagnóstico , Reprodutibilidade dos Testes , Estudos Retrospectivos , Sensibilidade e Especificidade
2.
Ultrasonics ; 103: 106095, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32044566

RESUMO

We measured the apparent reflection coefficient of a 1-MHz ultrasound compressional wave at the interface between rough and lubricated tongue mimicking surfaces and various food gels, composed of agar or gelatin. For the smoothest mimicking surface, when a lubricating layer was present, the apparent reflection coefficient was fairly similar for the different food gels (33.6% on average). The apparent reflection coefficient was significantly larger in the following situations: (i) tongue asperities were high and dense; (ii) lubrication levels were low; and (iii) gels were less rigid (range for the different gels-45.9-84.3%). The apparent reflection coefficient conveys the ability of food gels to mold themselves to surface asperities or to form a coupling film of liquid at the interface. This study demonstrates that ultrasound methods can and should be used to explore the physical phenomena that underlie the texture perceptions resulting from tongue-palate interactions.


Assuntos
Alimentos , Língua/diagnóstico por imagem , Ultrassonografia/métodos , Ágar , Módulo de Elasticidade , Gelatina , Géis , Técnicas In Vitro , Lubrificação , Propriedades de Superfície
3.
Int J Sports Med ; 41(2): 82-88, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31902128

RESUMO

Sex differences exist in vascular responses to blood pressure perturbations, such as resistance exercise. Increases in aortic stiffness following acute resistance exercise appear different between sexes, with attenuated increases in females vs. males. Whether sex differences exist in carotid stiffness, following resistance exercise is unknown. This study sought to examine sex differences in carotid stiffness, aortic stiffness, and hemodynamics following acute resistance exercise. Thirty-five participants (18 male) completed 3 sets of 10 repetitions of maximal isokinetic knee extension/flexion. Aortic stiffness and hemodynamics were estimated using an automated oscillometric blood pressure monitor at baseline, 5- and 30-min post-exercise. Carotid stiffness was assessed by ß-stiffness index, pressure-strain elastic modulus and arterial compliance using ultrasonography. Resistance exercise increased aortic stiffness, mean and systolic pressure at 5-min (p<0.01), and pressure-strain elastic modulus at 5-min in both sexes (p<0.05). Arterial compliance decreased at 5- and 30-min post exercise in both sexes (p<0.01). No interaction effects were detected in carotid stiffness, aortic stiffness, and hemodynamics, indicating similar vascular responses between sexes. Our findings indicate that the large arteries appear to stiffen similarly following resistance exercise in males and females when presented with similar blood pressure responses.


Assuntos
Artérias Carótidas/fisiologia , Treinamento de Resistência , Rigidez Vascular/fisiologia , Adulto , Pressão Sanguínea/fisiologia , Composição Corporal , Módulo de Elasticidade/fisiologia , Feminino , Frequência Cardíaca/fisiologia , Humanos , Joelho/fisiologia , Masculino , Força Muscular/fisiologia , Fatores Sexuais , Adulto Jovem
4.
Dent Mater J ; 39(1): 148-153, 2020 Jan 31.
Artigo em Inglês | MEDLINE | ID: mdl-31666486

RESUMO

Many ß-Ti alloys have been developed for, and used in, medical devices because of the corrosion resistance, biocompatibility, and exceptionally low Young's modulus. The aim of the present study was to investigate the histomorphometric aspects of peri-implant bone around Ti-Nb-Sn alloy implants and compare them with those in the case of commercially pure Ti (Ti). Fluorescent morphological observations of ST-2 cells on the substrate were performed and bone morphogenesis around implants in rat femur was evaluated. There was no difference between the cell morphology on Ti and those on the Ti-Nb-Sn alloy during observation for 24 h. A comparison of the Ti-Nb-Sn alloy implant and the Ti implant showed no significant differences between the bone-to-implant contact ratios or the bone fractions. These results suggest that the biological adaptations with Ti-Nb-Sn implants during a healing period are similar to those with Ti. Ti-Nb-Sn is therefore suitable for use in dental implants.


Assuntos
Ligas , Titânio , Animais , Materiais Biocompatíveis , Osso e Ossos , Corrosão , Módulo de Elasticidade , Ratos
5.
Comput Methods Biomech Biomed Engin ; 23(2): 54-68, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31813291

RESUMO

Osteoporosis is an osteometabolic disease, which promotes structural degradation of bone tissue and reduction of mineral density. We reported here a mechanical resistance assay from normal, osteopenic and osteoporotic trabecular vertebral bones of human cadavers. We performed a compressed test on ninety samples, evaluating Young's modulus and X-ray microtomography to measure bone volume fraction and trabecular thickness. This experimental data are employed for computing the orthotropic macroscopic behavior of vertebral trabecular bones using known analytical formulae that were obtained by Galka et al. (Arch Mech 51: 335-355, 1999) via an asymptotic homogenization model. A geometrical model with a periodic orthogonal plate-like structure is applied. The properties of the bone-trabecular mass are considered linear, homogeneous and orthotropic. Average values for all technical or engineering elastic properties are computed for three important regions of the trabecular bones corresponding to thirty individuals classified as normal, osteopenic or osteoporotic by calcaneus ultrassometry. This study could be useful for a better understanding of the elastic behavior of trabecular bones in human vertebral bodies, allowing an estimation of bone answer under stress in different directions and the risk of fracture associated with osteoporosis.HighlightsDescribing the elastic behavior of trabecular bones in human vertebral bodies at the micro and macroscopic.Allow a better estimation of the stress in different directions and risk of fracture associated with osteoporosis.Model request a very low computational cost.Offer a better understand the global effective coefficients of samples of trabecular bone, from the model of a periodic unit cell, in the format orthogonal plate-like structure with homogeneous bone mass.


Assuntos
Osso Esponjoso/fisiopatologia , Osteoporose/fisiopatologia , Coluna Vertebral/fisiopatologia , Densidade Óssea , Osso Esponjoso/diagnóstico por imagem , Módulo de Elasticidade , Elasticidade , Humanos , Masculino , Osteoporose/diagnóstico por imagem , Coluna Vertebral/diagnóstico por imagem , Microtomografia por Raio-X
6.
Carbohydr Polym ; 227: 115347, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31590845

RESUMO

Viscosupplementation, i.e. intra-articular injection of hyaluronic acid derivatives, is considered as the most effective treatment for patients with mild to moderate osteoarthritis. Even if hyaluronic acid is still considered as the gold standard, research is now focusing on the development of new products with enhanced injectability and yet reasonable viscoelastic behavior for OA treatment. A Gellan Gum (GG) hydrogel was synthesized and coated with crosslinked polyvinyl alcohol (PVA) to protect the polysaccharide from degradation during sterilization and improve its performance for the foreseen application. Thermal analyses indicated that mixed hydrogel showed a higher degree of structuring than the bare polysaccharide core without losing its swelling properties, thanks to the hydrophylicity of both coating and cross-linking agent. The PVA coating increased elastic and viscous moduli of the polysaccharide core conferring it a higher resistance to shear and compression and better thixotropic properties. Despite the double crosslinking, hydrogel was injectable. Cytocompatibility towards chondrocytes was verified.


Assuntos
Hidrogéis/química , Polissacarídeos Bacterianos/química , Álcool de Polivinil/química , Animais , Proliferação de Células , Sobrevivência Celular , Condrócitos , Módulo de Elasticidade , Humanos , Camundongos , Células NIH 3T3 , Osteoartrite/tratamento farmacológico , Viscosidade
7.
Food Chem ; 309: 125717, 2020 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-31699559

RESUMO

The feasibility of using celery cellulose hydrogels as carriers was explored for controlled release of short-chain fatty acids (SCFAs) triggered by ultrasound. The hydrogels were prepared with the phase inversion method and further characterized using FT-IR, SEM and XRD techniques. At the optimal cellulose concentration (8.33 and 6.25 mg/mL), the hydrogels (F4 and F5) exhibited the swelling ratio of 185%, and Young's modulus of the F4 and F5 was lower than that of others. The hydrogels were loaded with SCFAs owing to its hydrophilicity and swelling properties, and the maximum loading capacity of SCFAs achieved nearly 80%. Interestingly, the loaded SCFAs within hydrogel carrier could be readily released if an ultrasound trigger is exerted. Our results indicate that the ultrasound-triggered strategy for the SCFAs delivery system could provide a promising basis to achieve on-demand, reproducible, repeated, and tunable dosing of bioactive molecules.


Assuntos
Apium/metabolismo , Celulose/química , Ácidos Graxos Voláteis/química , Hidrogéis/química , Portadores de Fármacos/química , Liberação Controlada de Fármacos , Módulo de Elasticidade , Ácidos Graxos Voláteis/metabolismo , Sonicação
8.
Mater Sci Eng C Mater Biol Appl ; 106: 110265, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31753343

RESUMO

Young's modulus is essential for the design and production of the alloys. Thus, we proposed a MGI (Materials Genome Initiative)-oriented strategy for the high-throughput development of Young's modulus databank in the single-phase alloys. In this study, 17 diffusion couples of the bcc Ti-rich Ti-Nb-Zr, Ti-Nb-Cr and Ti-Nb-Zr-Cr systems annealed at 1273 K for 25 h were experimentally prepared. Subsequently, the composition-dependent Young's moduli and hardness in the bcc Ti-rich Ti-Nb-Zr-Cr system were determined by combining the nanoindentation technique and the electron probe micro analysis (EPMA). Moreover, on the basis of the presently obtained experimental data, the Young's modulus databank in the bcc Ti-Nb-Zr-Cr system were established by means of the CALPHAD (CALculation of PHAse Diagrams) approach. Finally, the Ti-22.6 at.% Nb-30 at.% Zr-3.8 at.% Cr alloy was designed from the Young's modulus databank and verified by using the nanoindentation and cytotoxicity tests. The results reveal that the present MGI-oriented strategy with the combination of the high-throughput measurements and the CALPHAD approach is a very effective method to accelerate the design/development of novel bio-Ti alloys.


Assuntos
Ligas/química , Ligas/toxicidade , Animais , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Cromo/química , Módulo de Elasticidade , Camundongos , Nióbio/química , Titânio/química , Zircônio/química
9.
Chem Asian J ; 14(24): 4837-4846, 2019 Dec 13.
Artigo em Inglês | MEDLINE | ID: mdl-31756283

RESUMO

Three-dimensional (3D) scaffolds formed from natural biopolymers gelatin and chitosan that are chemically modified by galactose have shown improved hepatocyte adhesion, spheroid geometry and functions of the hepatocytes. Galactose specifically binds to the hepatocytes via the asialoglycoprotein receptor (ASGPR) and an increase in galactose density further improves the hepatocyte proliferation and functions. In this work, we aimed to increase the galactose density within the biopolymeric scaffold by physically blending the biopolymers chitosan and gelatin with an amphiphlic ß-galactose polypeptide (PPO-GP). PPO-GP, is a di-block copolymer with PPO and ß-galactose polypeptide, exhibits lower critical solution temperature and is entrapped within the scaffold through hydrophobic interactions. The uniform distribution of PPO-GP within the scaffold was confirmed by fluorescence microscopy. SEM and mechanical testing of the hybrid scaffolds indicated pore size, inter connectivity and compression modulus similar to the scaffolds made from 100 % biopolymer. The presence of the PPO-GP on the surface of the scaffold was tested monitoring the interaction of an analogous mannose containing PPO-GP scaffold and the mannose binding lectin Con-A. In vitro cell culture experiments with HepG2 cells were performed on GLN-GP and CTS-GP and their cellular response was compared with GLN and CTS scaffolds for a period of seven days. Within three days of culture the Hep G2 cells formed multicellular spheroids on GLN-GP and CTS-GP more efficiently than on the GLN and CTS scaffolds. The multicellular spheroids were also found to infiltrate more in GLN-GP and CTS-GP scaffolds and able to maintain their round morphology as observed by live/dead and SEM imaging.


Assuntos
Quitosana/química , Gelatina/química , Glicoproteínas/química , Hepatócitos/metabolismo , Polímeros/química , Propilenoglicóis/química , Tecidos Suporte/química , Animais , Módulo de Elasticidade , Galactosídeos/química , Células Hep G2 , Humanos , Hidrogéis/síntese química , Hidrogéis/química , Esferoides Celulares/metabolismo , Suínos , Engenharia Tecidual/métodos
10.
Nat Commun ; 10(1): 4774, 2019 10 21.
Artigo em Inglês | MEDLINE | ID: mdl-31636256

RESUMO

Constitutional dynamic networks (CDNs) attract interest as signal-triggered reconfigurable systems mimicking natural networks. The application of CDNs to control material properties is, however, a major challenge. Here we report on the design of a CDN consisting of four toehold-modified constituents, two of which act as bidentate units for chain-elongating, while the other two form a tetradentate structure acting as a crosslinking unit. Their hybridization yields a hydrogel of medium stiffness controlled by the balance between bidentate and tetradentate units. Stabilization of the tetradentate constituent by an auxiliary effector up-regulates the crosslinking unit, yielding a high-stiffness hydrogel. Conversely, stabilization of one of the bidentate constituents by an orthogonal effector enriches the chain-elongation units leading to a low-stiffness hydrogel. Using appropriate counter effectors, the hydrogels are reversibly switched across low-, medium- and high-stiffness states. The hydrogels are used to develop self-healing and controlled drug-release matrices and functional materials for operating biocatalytic cascades.


Assuntos
DNA/química , Módulo de Elasticidade , Hidrogéis/síntese química , Ciência dos Materiais , Biocatálise , Preparações de Ação Retardada , Sistemas de Liberação de Medicamentos , Elasticidade , Teste de Materiais
11.
J Orofac Orthop ; 80(6): 292-303, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31578595

RESUMO

PURPOSE: The mechanical properties of orthodontic aligners made from thermoplastic polymers decrease over time in the intraoral milieu. However, there is a lack of information on this topic in the literature. Thus, the elastic properties of polyethylene terephthalate glycol (PETG) aligner films were investigated in vitro under extreme temperature changes simulated by thermocycling, environmental temperature and water absorption. MATERIALS AND METHODS: A total of 60 specimens made from PETG aligner films (CA Clear Aligner, Scheu Dental, Iserlohn, Germany) were divided into three groups (immersed in distilled water, subjected to accelerated ageing by thermocycling, control). These groups were again divided and tensile testing was performed for all groups at 22 and at 37 °C. Young's modulus (E), 0.2% offset yield strength (Rp02) and ultimate tensile strength (UTS) were evaluated. Water absorption was determined using an analytical scale. RESULTS: All treated specimens showed water absorption, whereby specimens that were thermocycled absorbed 48% more water than the immersed ones. Young's modulus and UTS were significantly lower for all three groups at 37 °C compared to the corresponding groups tested at 22 °C. Thermocycled and immersed groups showed a significantly lower Young's modulus compared to the control group tested at the same temperature. The mean Rp02 was statistically different when comparing the control group tested at 22 °C to the one tested at 37 °C. CONCLUSIONS: The results of this study add to the understanding of the clinically well-known degradation of orthodontic aligners during wear time. Extreme alternating temperatures along with warming up to intraoral temperature and water absorption can reduce the material's Young's modulus and may therefore promote a decrease of resulting orthodontic forces.


Assuntos
Envelhecimento , Água , Módulo de Elasticidade , Alemanha , Teste de Materiais , Polietilenoglicóis , Polietilenotereftalatos , Resistência à Tração
12.
Eur Phys J E Soft Matter ; 42(10): 134, 2019 Oct 23.
Artigo em Inglês | MEDLINE | ID: mdl-31643003

RESUMO

Biofilms are self-assembling structures consisting of rigid microbial cells embedded in a soft biopolymeric extracellular matrix (ECM), and have been commonly viewed as being detrimental to health and equipment. In this work, we show that biofilms formed by a non-pathogenic fungus Neurospora discreta, are fungal bio-composites (FBCs) that can be directed to self-organize through active stresses to achieve specific properties. We induced active stresses by systematically varying the agitation rate during the growth of FBCs. By growing FBCs that are strong enough to be conventionally tensile loaded, we find that as agitation rate increases, the elongation strain at which the FBCs break, increases linearly, and their elastic modulus correspondingly decreases. Using results from microstructural imaging and thermogravimetry, we rationalize that agitation increases the production of ECM, which concomitantly increases the water content of agitated FBCs up to 250% more than un-agitated FBCs. Water held in the nanopores of the ECM acts a plasticizer and controls the ductility of FBCs in close analogy with polyelectrolyte complexes. This paradigm shift in viewing biofilms as bio-composites opens up the possibility for their use as sustainable, biodegradable, low-modulus structural materials.


Assuntos
Biofilmes , Módulo de Elasticidade , Interações Hidrofóbicas e Hidrofílicas , Neurospora/fisiologia , Biopolímeros/química , Matriz Extracelular/química , Matriz Extracelular/ultraestrutura , Nanoporos , Neurospora/química , Neurospora/ultraestrutura , Polieletrólitos/química , Resistência à Tração
13.
Sheng Wu Yi Xue Gong Cheng Xue Za Zhi ; 36(5): 827-833, 2019 Oct 25.
Artigo em Chinês | MEDLINE | ID: mdl-31631632

RESUMO

In the present study, the performance of the liquid nitrogen frozen and thinned bovine pericardium was studied and compared with the porcine pericardium. The microstructure and mechanical properties of the bovine pericardium were observed and tested by hematoxylin-eosin (HE) staining and tensile test respectively. In all conditions, porcine pericardium was selected as a control group. The results showed that there was little difference in the performance of bovine pericardium after being frozen by liquid nitrogen. The secant modulus and ultimate strength of the thinned bovine pericardium were similar to those of porcine pericardium, however, the elastic modulus was a little higher than porcine pericardium. The study suggested that the performance of the thinned bovine pericardium was similar to those of porcine pericardium. It was easy for the thinned bovine pericardium to obtain a relatively ideal thickness and expected performance, therefore, the thinned bovine pericardium can be used as the materials of transcatheter aortic valve leaflets.


Assuntos
Bioprótese , Congelamento , Próteses Valvulares Cardíacas , Pericárdio/fisiologia , Animais , Valva Aórtica , Bovinos , Módulo de Elasticidade , Nitrogênio , Suínos
14.
Dent Mater ; 35(11): e286-e297, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31551153

RESUMO

OBJECTIVE: To test the effects of addition of polyacrilonitrile (PAN) nanofibers and nanocrystal cellulose (NCC)-containing PAN nanofibers on flexural properties of experimental dental composites. METHODS: 11wt% PAN in dimethylformamide (DMF) solution was electrospun at 17.2kVA and 20cm from the collector drum. NCC was added to the solution at 3wt%. Fiber mats were produced in triplicates and tested as-spun. Strips (5cm×0.5cm) were cut from the mat in an orientation parallel and perpendicular to the rotational direction of the collector drum. Tensile tests were performed and ultimate tensile strength (UTS), elastic modulus (E) and elongation at maximum stress (%) were calculated from stress/strain plots. Fiber mats were then infiltrated by resin monomers (50/50 BisGMA/TEGDMA wt%), stacked in a mold (2×15×25) and light-cured. Beams (2×2×25mm) were cut from the slabs and tested in a universal testing machine. Data were analyzed by multiple t-test and one-way ANOVA (α=0.05). RESULTS: Addition of 3% NCC resulted in higher tensile properties of the fibers. Fibers presented anisotropic behavior with higher UTS and E when tested in perpendicular orientation. The incorporation of 3% NCC-PAN nanofibers resulted in significant increase in work of fracture and flexural strength of experimental dental composite beams. SIGNIFICANCE: NCC was found to be a suitable nanoparticle to reinforce experimental dental composites by incorporation via nanofiber. This fundamental study warrants future investigation in the use of electrospun nanofibres as a way to reinforce dental composites.


Assuntos
Nanofibras , Nanopartículas , Celulose , Resinas Compostas , Módulo de Elasticidade , Teste de Materiais , Resistência à Tração
15.
ACS Appl Mater Interfaces ; 11(39): 36100-36109, 2019 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-31502438

RESUMO

Development of stretchable devices with mechanical responses that mimic those of biological tissues/organs is of particular importance for the long-term biointegration, as the discomfort induced by the mechanical mismatch can be minimized. Recent works have established the bioinspired designs of soft network materials that can precisely reproduce the unconventional J-shaped stress-strain curves of human skin at different regions. Existing studies mostly focused on the design, fabrication, and modeling of perfect soft network materials. When utilized as the substrates of biointegrated electronics, the soft network designs, however, often need to incorporate deterministic holes, a type of imperfection, to accommodate hard, inorganic electronic components. Understanding of the effect of hole imperfections on the mechanical properties of soft network materials is thereby essential in practical applications. This paper presents a combined experimental and computational study of the stretchability and elastic modulus of imperfect soft network materials consisting of circular holes with a variety of diameters. Both the size and location of the circular-hole imperfections are shown to have profound influences on the stretchability. Based on these results, design guidelines of imperfection-insensitive network materials are introduced. For the imperfections that result in an evident reduction of stretchability, an effective reinforcement approach is presented by enlarging the width of horseshoe microstructures at strategic locations, which can enhance the stretchability considerably. A stretchable and imperfection-insensitive integrated device with a light-emitting diode embedded in the network material serves a demonstrative application.


Assuntos
Materiais Biomiméticos , Módulo de Elasticidade , Pele , Humanos , Dispositivos Eletrônicos Vestíveis
16.
Carbohydr Polym ; 225: 115189, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31521300

RESUMO

The goal of this research is to develop a functional nanocellulose and activated carbon (NAC) film and characterize its biosensing properties for smart packaging applications. The NAC film was prepared from activated carbon powder and nanocellulose gel using the casting method. The nanocellulose contents in the films were varied from 15% to 50% (w/w). Physicochemical properties of the produced films such as electrical conductivity, water absorption capacity, solubility in water and mechanical properties were measured. The electrical conductivity of the NAC film decreased when nanocellulose content increased. The tensile strength (TS), strain and Young's modulus of films increased significantly from 0.03 to 4.78 MPa, 0.13 to 1.94% and 97.64 to 247.3 MPa, respectively, when the nanocellulose contents increased. Thermal stability was also determined using thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results showed that thermal decomposition was occurred in a temperature range of 300-400 °C.


Assuntos
Celulose/química , Carvão Vegetal/química , Nanocompostos/química , Módulo de Elasticidade , Condutividade Elétrica , Embalagem de Alimentos , Permeabilidade , Solubilidade , Resistência à Tração
17.
PLoS Comput Biol ; 15(9): e1006798, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31539369

RESUMO

Cells interacting through an extracellular matrix (ECM) exhibit emergent behaviors resulting from collective intercellular interaction. In wound healing and tissue development, characteristic compaction of ECM gel is induced by multiple cells that generate tensions in the ECM fibers and coordinate their actions with other cells. Computational prediction of collective cell-ECM interaction based on first principles is highly complex especially as the number of cells increase. Here, we introduce a computationally-efficient method for predicting nonlinear behaviors of multiple cells interacting mechanically through a 3-D ECM fiber network. The key enabling technique is superposition of single cell computational models to predict multicellular behaviors. While cell-ECM interactions are highly nonlinear, they can be linearized accurately with a unique method, termed Dual-Faceted Linearization. This method recasts the original nonlinear dynamics in an augmented space where the system behaves more linearly. The independent state variables are augmented by combining auxiliary variables that inform nonlinear elements involved in the system. This computational method involves a) expressing the original nonlinear state equations with two sets of linear dynamic equations b) reducing the order of the augmented linear system via principal component analysis and c) superposing individual single cell-ECM dynamics to predict collective behaviors of multiple cells. The method is computationally efficient compared to original nonlinear dynamic simulation and accurate compared to traditional Taylor expansion linearization. Furthermore, we reproduce reported experimental results of multi-cell induced ECM compaction.


Assuntos
Fenômenos Fisiológicos Celulares/fisiologia , Matriz Extracelular/fisiologia , Modelos Biológicos , Fenômenos Biomecânicos/fisiologia , Módulo de Elasticidade/fisiologia , Dinâmica não Linear , Pseudópodes/fisiologia
18.
Mater Sci Eng C Mater Biol Appl ; 105: 110117, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31546366

RESUMO

Failure of fixation between bone and implant surface due to bacterial infection, is one of the key challenges in total hip arthroplasty. It might lead to poor implant stability and complex revision surgery. Surface modification of an acetabular cup liner for sustained drug delivery is an effective approach to reduce the biofilms associated infection. The aim of the study is to evaluate the influence of different surface modification technique on drug delivery, mechanical and tribological performances of the acetabular cup liner. Solvent-based etching and electrostatic spray deposition technique was individually used to engineer a thin microporous surface layer on ultra-high molecular weight polyethylene (UHMWPE), which is commercially used as acetabular cup liner in total hip implant. Porous surfaces were filled with drug (gentamicin) containing biodegradable polymer (chitosan) through impregnation process and their efficacy was compared in the intended application. The surfaces, modified by both techniques, have shown lower friction coefficient. The higher wear rates were noticed for electrostatic sprayed coating. Both the modified surfaces have shown slight decrease in hardness and elastic modulus, which may be attributed to improper impregnation of polymer inside porous surface. However, after the release of drug, the solvent-based etched surface regains its mechanical and tribological properties, in similar range to the unmodified UHMWPE surface. Both the modified surfaces have shown an impressive drug release profile and in vitro antibacterial efficacy. The drug release duration was more for electrostatic spray modified surface. Hence, these surfaces modified implant parts shown great promise for fighting against post-surgery bacterial infection.


Assuntos
Liberação Controlada de Fármacos , Ortopedia , Polietilenos/química , Próteses e Implantes , Eletricidade Estática , Anti-Infecciosos/farmacologia , Módulo de Elasticidade , Fricção , Gentamicinas/farmacologia , Dureza , Cinética , Porosidade , Propriedades de Superfície
19.
Mater Sci Eng C Mater Biol Appl ; 105: 110014, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31546414

RESUMO

Cuttlefish bone (CB) has been explored as biomaterial in the bone tissue-engineering field due to its unique porous structure and capacity of the aragonite mineral to be hydrothermally converted into calcium phosphates (CaPs). In the present study, undoped and ion (Sr2+, Mg2+ and/or Zn2+) doped biphasic calcium phosphate (BCP) scaffolds were prepared by hydrothermal transformation (HT, 200 °C, 24 h) of CB. The obtained scaffolds were sintered and then coated with two commercial polymers, poly(ε-caprolactone) (PCL) or poly(DL-lactide) (PDLA), and with two synthesized ones, a poly(ester amide) (PEA) or a poly(ester urea) (PEU) in order to improve their compressive strength. The scaffolds were characterized by X-ray diffraction (XRD) coupled with structural Rietveld refinement, Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). The results demonstrate that CB could be entirely transformed into BCPs in the presence or absence of doping elements. The initial CB structure was preserved and the polymeric coatings did not jeopardize the interconnected porous structure. Furthermore, the polymeric coatings enhanced the compressive strength of the scaffolds. The in vitro bio-mineralization upon immersing the scaffolds into simulated body fluid (SBF) demonstrated the formation of bone-like apatite surface layers in both uncoated and coated scaffolds. Overall, the produced scaffolds exhibit promising properties for bone tissue engineering applications.


Assuntos
Osso e Ossos/química , Fosfatos de Cálcio/farmacologia , Materiais Revestidos Biocompatíveis/farmacologia , Decapodiformes/anatomia & histologia , Polímeros/farmacologia , Tecidos Suporte/química , Animais , Osso e Ossos/ultraestrutura , Calcificação Fisiológica , Força Compressiva , Módulo de Elasticidade , Porosidade , Espectroscopia de Infravermelho com Transformada de Fourier , Propriedades de Superfície , Temperatura Ambiente , Difração de Raios X
20.
Molecules ; 24(18)2019 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-31527527

RESUMO

This study presents a comparison of two types of bifunctional structured surface that were made from the same polymer -- an antimicrobial polycation (a synthetic mimic of an antimicrobial peptide, SMAMP) and a protein-repellent polyzwitterion (poly(sulfobetaines), PSB). The first type of bifunctional surface was fabricated by a colloidal lithography (CL) based process where the two polymers were immobilized sequentially onto pre-structured surfaces with a chemical contrast (gold on silicon). This enabled site-selective covalent attachment. The CL materials had a spacing ranging from 200 nm to 2 µm. The second type of structured surface (spacing: 1 - 8.5 µm) was fabricated using a microcontact printing (µCP) process where SMAMP patches were printed onto a PSB network, so that 3D surface features were obtained. The thus obtained materials were studied by quantitative nanomechanical measurements using atomic force microscopy (QNM-AFM). The different architectures led to different local elastic moduli at the polymer-air interface, where the CL surfaces were much stiffer (Derjaguin-Muller-Toporov (DMT) modulus = 20 ± 0.8 GPa) compared to the structured 3D networks obtained by µCP (DMT modulus = 42 ± 1.1 MPa). The effects of the surface topology and stiffness on the antimicrobial activity against Escherichia coli, the protein repellency (using fibrinogen), and the compatibility with human gingival mucosal keratinocytes were investigated. The softer 3D µCP surfaces had simultaneous antimicrobial activity, protein repellency, and cell compatibility at all spacings. For the stiffer CL surfaces, quantitative simultaneous antimicrobial activity and protein repellency was not obtained. However, the cell compatibility could be maintained at all spacings. The optimum spacing for the CL materials was in the range of 500 nm-1 µm, with significantly reduced antimicrobial activity at 2 µm spacing. Thus, the soft polymer network obtained by µCP could be more easily optimized than the stiff CL surface, and had a broader topology range of optimal or near-optimal bioactivity.


Assuntos
Anti-Infecciosos/química , Anti-Infecciosos/farmacologia , Biopolímeros/química , Biopolímeros/farmacologia , Módulo de Elasticidade , Coloides/química , Humanos , Microscopia de Força Atômica , Estrutura Molecular , Relação Estrutura-Atividade , Propriedades de Superfície
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