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1.
J Appl Oral Sci ; 27: e20180556, 2019 Sep 09.
Artigo em Inglês | MEDLINE | ID: mdl-31508791

RESUMO

OBJECTIVE: To evaluate the effect of ultrasonic and sonic activation on physicochemical properties of AH Plus, MTA Fillapex, ADSeal, GuttaFlow Bioseal, and GuttaFlow 2 sealers. METHODOLOGY: Three experimental groups were formed: no activation (NA), ultrasonic activation (UA), and sonic activation (SA). The sealers were manipulated according to the manufacturers' instructions. A 3-mL syringe was adapted to receive 1 mL of sealer. Activation was performed with a 20/.01 ultrasonic insert (20 s/1W) in the UA group. A size 35.04 sonic tip was used (20 s/10,000 cycles/min-1) in the SA group. The molds for physicochemical analysis were filled and evaluated according to ANSI/ADA specification no. 57: setting time (ST), flow (FL), dimensional change (DC), solubility (SB), and radiopacity (RD). Statistical analysis was performed by Kruskal-Wallis, one-way ANOVA, and Tukey's tests (P<0.05). RESULTS: Regarding ST, only AH Plus and GuttaFlow 2 in the NA group met the ANSI/ADA standards. All FL values were greater than 20 mm in diameter, as determined by ANSI/ADA. The tested sealers and protocols did not comply with the ANSI/ADA standards for DC. As for SB, only MTA Fillapex, regardless of the activation protocol, did not follow the ANSI/ADA standards. All of the investigated sealers, regardless of the activation protocol, presented radiographic density higher than 3 mm Al, as proposed by ANSI/ADA. CONCLUSIONS: UA and SA promoted changes in the physicochemical properties of the evaluated root canal sealers, mainly in ST and F. Thus, it is important to evaluate the physicochemical properties of endodontic sealers associated with activation techniques prior to clinical application in order to determine whether the properties follow the parameters set by ANSI/ADA, ensuring safety and quality of root canal filling.


Assuntos
Compostos de Alumínio/química , Compostos de Cálcio/química , Dimetilpolisiloxanos/química , Resinas Epóxi/química , Guta-Percha/química , Óxidos/química , Materiais Restauradores do Canal Radicular/química , Silicatos/química , Ondas Ultrassônicas , Análise de Variância , Combinação de Medicamentos , Teste de Materiais , Valores de Referência , Reprodutibilidade dos Testes , Solubilidade , Estatísticas não Paramétricas , Propriedades de Superfície , Fatores de Tempo
2.
Chem Commun (Camb) ; 55(80): 12036-12039, 2019 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-31531454

RESUMO

While commercially available suncare products are effective at absorbing ultraviolet (UV)-light, recent studies indicate systemic toxicities associated with many traditional chemical and physical UV-filters. We demonstrate the application of xanthommatin, a biochrome present in arthropods and cephalopods, as an alternative chemical UV-filter that is cytocompatible while maintaining its photostability and photoprotective properties.


Assuntos
Antioxidantes/farmacologia , Oxazinas/farmacologia , Pele/efeitos da radiação , Protetores Solares/farmacologia , Xantenos/farmacologia , Animais , Antioxidantes/química , Sobrevivência Celular/efeitos dos fármacos , Dano ao DNA , Dimetilpolisiloxanos/química , Humanos , Camundongos , Células NIH 3T3 , Oxazinas/química , Estudo de Prova de Conceito , Pele/citologia , Protetores Solares/química , Raios Ultravioleta , Xantenos/química
3.
J Chromatogr A ; 1603: 67-82, 2019 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-31272730

RESUMO

A dynamic headspace (DHS) with DVB/CAR/PDMS trapping materials was coupled to a gas chromatography-mass spectrometry for the separation and identification of volatile-flavor compounds in bos grunniens (yak) milk. The principal components analysis coupled with response surface methodology optimized the main variables of the device (10 g sample quality, 5 min desorption time, 3.0 g adding sodium chloride, 72 °C extraction temperature, 28 min pre-equilibrium time and 86 min extraction time). Total 235 volatile components were identified. The limit of detections and quantifications of volatile components were 0.01-5.35 mg kg-1 and 0.01-9.41 mg kg-1, respectively, with relative standard deviation from 0.2% to 6.4%. The method performed well during volatile-flavor components analysis from the yak milk sample, producing excellent extraction parameters for the volatile components. Eighty-two volatile components identified in yak milk belonged to a broad range of chemical classes (ketones, aldehydes, aromatics, acids, alkanes, and estes), and 73 of them were at trace levels. Meanwhile, using gas chromatography-olfactometry technique, 11 volatile components were identified as contributors to the aroma of yak milk. In conclusions, a sensitive, convenient and reliable method was developed for the accurate determination of volatile-flavor compounds in yak milk utilizing DHS-GC/MS analyses.


Assuntos
Aromatizantes/análise , Cromatografia Gasosa-Espectrometria de Massas/métodos , Leite/química , Odorantes/análise , Compostos Orgânicos Voláteis/análise , Animais , Bovinos , Dimetilpolisiloxanos/química , Polivinil/química
4.
Chemosphere ; 232: 489-495, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31174007

RESUMO

Passive sampling by deploying organic polymers for 20-30 days in soils or sediments has been used for the assessment of bioavailability and mobility of hydrophobic organic contaminants. An important step in their interpretation is the estimation of the degree of equilibration, typically through the release of performance reference compounds (PRCs). This paper develops an improved modeling tool for predicting the behaviors of PRCs and contaminant compounds in devices in cylindrical geometry, such as polydimethylsiloxane (PDMS) fibers or dialysis samplers of cylindrical cross-section. The model is solved by both a numerically inverted Laplace domain solution and an asymptotic analytical solution. The solutions are verified with the numerically simulated results. A comparison of the developed model to existing models for the calibration of uptake/release rates and the estimation of soil or sediment transport properties is performed. The result suggests that the cylindrical model provides a more accurate prediction for the transient behavior of PRC and target compounds as well as a better estimate of transport properties in the media.


Assuntos
Monitoramento Ambiental/métodos , Sedimentos Geológicos/química , Modelos Teóricos , Hidrocarbonetos Policíclicos Aromáticos/análise , Poluentes Químicos da Água/análise , Dimetilpolisiloxanos/química , Interações Hidrofóbicas e Hidrofílicas , Hidrocarbonetos Policíclicos Aromáticos/química
5.
Ecotoxicol Environ Saf ; 182: 109374, 2019 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-31254853

RESUMO

Obtaining accurate measurements of the partition coefficients between sorbent materials and water is of major importance for the analysis of the adsorption behavior and dissolved concentrations of organic compounds in the environment. In the passive-sampling approach, polydimethylsiloxane (PDMS) has a wide range of applications. Therefore, we established a poly-parameter linear-free energy relationship (pp-LFER) and a quantitative structure-activity relationship (QSAR) model to predict the log KPDMS-w values for a large dataset of 290 organic chemicals from 11 diverse classes. For the pp-LFER model, E (excess molar refractivity), A (molecular H-bond donor ability), V (McGowan volume), and B (the H-bond acceptor properties) were introduced as the main correlated variables. However, the obtained model is much limited in terms of acquiring available descriptors. For this reason, we developed a QSAR model, and CrippenLogP (Crippen octanol-water partition coefficient), RNCG (Relative negative charge-most negative charge/total negative charge), ATSC4e (Centered Broto-Moreau autocorrelation-lag4/weighted by Sanderson electronegativities) and GATS6p (Geary autocorrelation-lag6/weighted by polarizabilities) were selected as the significant parameters. The predictive power and functional reliability of the presented models were confirmed with validation methods as described in previous studies. The adjusted determination coefficients (R2adj) of 0.851 and 0.922 and leave-one-out cross-validated (Q2LOO) of 0.841 and 0.907 revealed that the models have good predictive power and generalizability. Thus, the proposed models are simple yet accurate tools for predicting the log KPDMS-w values and providing new insights to further understand the adsorption mechanism of organic compounds.


Assuntos
Dimetilpolisiloxanos/química , Modelos Químicos , Água/química , Octanóis/química , Relação Quantitativa Estrutura-Atividade , Reprodutibilidade dos Testes
6.
Nat Commun ; 10(1): 2695, 2019 06 19.
Artigo em Inglês | MEDLINE | ID: mdl-31217422

RESUMO

Soft wearable electronics for underwater applications are of interest, but depend on the development of a waterproof, long-term sustainable power source. In this work, we report a bionic stretchable nanogenerator for underwater energy harvesting that mimics the structure of ion channels on the cytomembrane of electrocyte in an electric eel. Combining the effects of triboelectrification caused by flowing liquid and principles of electrostatic induction, the bionic stretchable nanogenerator can harvest mechanical energy from human motion underwater and output an open-circuit voltage over 10 V. Underwater applications of a bionic stretchable nanogenerator have also been demonstrated, such as human body multi-position motion monitoring and an undersea rescue system. The advantages of excellent flexibility, stretchability, outstanding tensile fatigue resistance (over 50,000 times) and underwater performance make the bionic stretchable nanogenerator a promising sustainable power source for the soft wearable electronics used underwater.


Assuntos
Fontes de Energia Elétrica , Nanotecnologia/métodos , Tecnologia de Sensoriamento Remoto/instrumentação , Dispositivos Eletrônicos Vestíveis , Animais , Materiais Biomiméticos/química , Membrana Celular/química , Dimetilpolisiloxanos/química , Electrophorus , Humanos , Canais Iônicos/química , Estrutura Molecular , Movimento , Nanopartículas/química , Oceanos e Mares , Trabalho de Resgate , Resistência à Tração , Tecnologia sem Fio
7.
Artif Cells Nanomed Biotechnol ; 47(1): 1888-1897, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31072140

RESUMO

Storage lesions in red blood cells (RBCs) hinder efficient circulation and tissue oxygenation. The absence of flow mechanics and gas exchange may contribute to this problem. To test if in vitro compensation of flow mechanics and gas exchange helps RBC recovery, three-dimensional polydimethylsiloxane (PDMS) porous structures were fabricated with a sugar mould, simulating lung alveoli. RBC suspensions were passed through the porous structure cyclically, simulating in vivo blood circulation. Acid-base indices, partial gas pressures, ions, glucose and RBC indices were analyzed. An atomic force microscope was used to investigate local mechanical properties of intact RBCs. RBCs suspensions that passed through the porous structures had a higher pH and oxygen partial pressure, and a lower potassium concentration and carbon dioxide partial pressure. Meantime they had better biochemical properties relative to static samples, namely, they exhibited a more homogenous distribution of Young's Modulus. RBCs that passed through a PDMS porous structure were healthier than static ones, giving hints to prevent RBC storage lesions.


Assuntos
Preservação de Sangue , Dimetilpolisiloxanos/química , Dimetilpolisiloxanos/farmacologia , Eritrócitos/efeitos dos fármacos , Gases/metabolismo , Hemorreologia/efeitos dos fármacos , Nylons/química , Nylons/farmacologia , Animais , Fenômenos Biomecânicos/efeitos dos fármacos , Módulo de Elasticidade/efeitos dos fármacos , Eritrócitos/citologia , Eritrócitos/metabolismo , Glucose/metabolismo , Concentração de Íons de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Masculino , Porosidade , Ratos , Ratos Wistar
8.
Talanta ; 201: 335-341, 2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-31122432

RESUMO

In 2008, several synthetic cannabinoids were detected in herbal smoking blends sold on websites and in the so-called "smart shops". These compounds, as well as new psychoactive substances, flooded the market of illicit drugs and are sold at street level. Development and validation of rapid analytical methods for the detection and quantification of synthetic cannabinoids in biological matrices are essential for the investigation of pharmacokinetic, pharmacodynamic and toxicological properties. In this pilot study, the potential of direct immersion solid-phase microextraction coupled to GC/MS for the determination of synthetic and natural cannabinoids in oral fluid was proved. Validation proved the suitability of the developed method for the determination of the analytes at trace levels in oral fluid: linearity was assessed in the LOQ - 1000 ng/mL range, whereas a good precision was observed with CV below 20%. The method was then applied to more than 100 real oral fluid samples collected from a population of young students, showing a positivity rate of 3.8%.


Assuntos
Canabinoides/análise , Cromatografia Gasosa-Espectrometria de Massas/métodos , Saliva/química , Microextração em Fase Sólida/métodos , Drogas Ilícitas/análise , Detecção do Abuso de Substâncias/métodos , Resinas Acrílicas/química , Adolescente , Adulto , Dimetilpolisiloxanos/química , Feminino , Humanos , Limite de Detecção , Masculino , Projetos Piloto , Polivinil/química , Microextração em Fase Sólida/instrumentação , Adulto Jovem
9.
ACS Appl Mater Interfaces ; 11(16): 14567-14575, 2019 Apr 24.
Artigo em Inglês | MEDLINE | ID: mdl-30942999

RESUMO

Biosensor systems for wearable continuous monitoring are desired to be developed into conformal patch platforms. However, developing such patches is very challenging owing to the difficulty of imparting materials and components with both high stretchability and high performance. Herein, we report a fully stretchable microfluidics-integrated glucose sensor patch comprised of an omnidirectionally stretchable nanoporous gold (NPG) electrochemical biosensor and a stretchable passive microfluidic device. A highly electrocatalytic NPG electrode was formed on a stress-absorbing 3D micropatterned polydimethylsiloxane (PDMS) substrate to confer mechanical stretchability, high sensitivity, and durability in non-enzymatic glucose detection. A thin, stretchable, and tough microfluidic device was made by embedding stretchable cotton fabric as a capillary into a thin polyurethane nanofiber-reinforced PDMS channel, enabling collection and passive, accurate delivery of sweat from skin to the electrode surface, with excellent replacement capability. The integrated glucose sensor patch demonstrated excellent ability to continuously and accurately monitor the sweat glucose level.


Assuntos
Automonitorização da Glicemia , Glicemia/análise , Ouro/química , Dispositivos Lab-On-A-Chip , Nanoporos , Dispositivos Eletrônicos Vestíveis , Glicemia/metabolismo , Automonitorização da Glicemia/instrumentação , Automonitorização da Glicemia/métodos , Dimetilpolisiloxanos/química , Eletrodos , Humanos , Poliuretanos/química
10.
Nat Commun ; 10(1): 1877, 2019 04 23.
Artigo em Inglês | MEDLINE | ID: mdl-31015402

RESUMO

Many microorganisms have evolved chemotactic strategies to exploit the microscale heterogeneity that frequently characterizes microbial habitats. Chemotaxis has been primarily studied as an average characteristic of a population, with little regard for variability among individuals. Here, we adopt a classic tool from animal ecology - the T-maze - and implement it at the microscale by using microfluidics to expose bacteria to a sequence of decisions, each consisting of migration up or down a chemical gradient. Single-cell observations of clonal Escherichia coli in the maze, coupled with a mathematical model, reveal that strong heterogeneity in the chemotactic sensitivity coefficient exists even within clonal populations of bacteria. A comparison of different potential sources of heterogeneity reveals that heterogeneity in the T-maze originates primarily from the chemotactic sensitivity coefficient, arising from a distribution of pathway gains. This heterogeneity may have a functional role, for example in the context of migratory bet-hedging strategies.


Assuntos
Quimiotaxia/genética , Escherichia coli/fisiologia , Modelos Biológicos , Fenótipo , Dimetilpolisiloxanos/química , Microscopia Intravital/métodos , Técnicas Analíticas Microfluídicas/métodos , Microscopia de Contraste de Fase/métodos , Análise de Célula Única/métodos
11.
Biosens Bioelectron ; 133: 236-242, 2019 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-30953882

RESUMO

Optical trapping of single particles or cells with the capability of in situ bio-sensing or genetic profiling opens the possibility of rapid screening of biological specimens. However, common optical tweezers suffer from the lack of long-range forces. Consequently, their application areas are predominantly limited to target manipulation instead of biological diagnostics. To solve this problem, we herein report an all-in-one approach by combining optical forces and convective drag forces generated through localized optothermal effect for long-range target manipulation. The device consists of a 2D array of gold coated polydimethylsiloxane (PDMS) micro-wells, which are immersed by colloidal particles or cell solution. Upon excitation of a 785-nm laser, the hydrodynamic convective force and optical forces will drag the targets of interest into their designated micro-wells. Moreover, the plasmonic thermal dissipation provides a constant temperature environment for following cell analysis procedures of cell isolation, lysis and isothermal nucleic acid amplification for the detection of genetic markers. With the merits of fabrication simplicity, short sample-to-answer cycle time and the compatibility with optical microscopes, the reported technique offers an attractive and highly versatile approach for on-site single cell analysis systems.


Assuntos
Técnicas Biossensoriais , Dimetilpolisiloxanos/química , Marcadores Genéticos , Análise de Célula Única , Coloides/química , Ouro/química , Lasers , Pinças Ópticas , Temperatura Ambiente
12.
Nanotechnology ; 30(33): 335501, 2019 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-31035268

RESUMO

Strong peeling resistance and water-drainable properties on rough and wet skin surfaces are highly desirable for realizing wearable and skin-attachable electronic sensors. Here, we propose a transparent, sensitive, glue-free pressure sensor for skin electronics. To achieve a thin, light-weight, transparent, and stretchable sensor patch, we laminated a single-layer graphene film as a sensing element on a thin polymeric supporter of polydimethylsiloxane. By assembling the graphene layer with densely populated micropillars, the pressure sensor achieved 10 times the sensitivity of a similar sensor without micropillars in the low-pressure range (<6 kPa). We then employed hexagonal patterns inspired by the toe pads of a tree frog, giving the assembled patch sensor with strong peeling resistance under both dry and wet conditions on surfaces such as silicon (15.5 J cm-2 for dry and 11.6 J cm-2 for wet conditions) and pig skin (2.0 J cm-2 for dry and 1.4 J cm-2 for wet conditions) without contamination after detachment. Our layered sensor patch also demonstrated successful measurement of water-dependent skin elasticity with transparent, conformal, and residual-free attachment, suggesting a variety of cosmetic and medical applications.


Assuntos
Técnicas Biossensoriais/instrumentação , Dimetilpolisiloxanos/química , Grafite/química , Fenômenos Fisiológicos da Pele , Adesivos/química , Animais , Fenômenos Biomecânicos , Elasticidade , Desenho de Equipamento , Nanoestruturas/química , Pressão , Suínos , Dispositivos Eletrônicos Vestíveis
13.
Nat Commun ; 10(1): 1821, 2019 04 23.
Artigo em Inglês | MEDLINE | ID: mdl-31015519

RESUMO

Self-powered implantable medical electronic devices that harvest biomechanical energy from cardiac motion, respiratory movement and blood flow are part of a paradigm shift that is on the horizon. Here, we demonstrate a fully implanted symbiotic pacemaker based on an implantable triboelectric nanogenerator, which achieves energy harvesting and storage as well as cardiac pacing on a large-animal scale. The symbiotic pacemaker successfully corrects sinus arrhythmia and prevents deterioration. The open circuit voltage of an implantable triboelectric nanogenerator reaches up to 65.2 V. The energy harvested from each cardiac motion cycle is 0.495 µJ, which is higher than the required endocardial pacing threshold energy (0.377 µJ). Implantable triboelectric nanogenerators for implantable medical devices offer advantages of excellent output performance, high power density, and good durability, and are expected to find application in fields of treatment and diagnosis as in vivo symbiotic bioelectronics.


Assuntos
Arritmia Sinusal/cirurgia , Fenômenos Eletrofisiológicos , Coração/fisiologia , Nanomedicina/instrumentação , Marca-Passo Artificial , Animais , Arritmia Sinusal/etiologia , Procedimentos Cirúrgicos Cardíacos/instrumentação , Procedimentos Cirúrgicos Cardíacos/métodos , Linhagem Celular , Dimetilpolisiloxanos/química , Modelos Animais de Doenças , Desenho de Equipamento , Masculino , Camundongos , Nanomedicina/métodos , Nylons/química , Politetrafluoretileno/química , Implantação de Prótese/instrumentação , Implantação de Prótese/métodos , Sus scrofa
14.
Sensors (Basel) ; 19(7)2019 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-30925721

RESUMO

We have developed a force sensing system to continuously evaluate the mechanical elasticity of micrometer-scale (a few hundred micrometers to a millimeter) live tissues. The sensing is achieved by measuring the deflection of force sensitive cantilevers through microscopic image analysis, which does not require electrical strain gauges. Cantilevers made of biocompatible polydimethylsiloxane (PDMS) were actuated by a piezoelectric actuator and functioned as a pair of chopsticks to measure the stiffness of the specimen. The dimensions of the cantilevers were easily adjusted to match the size, range, and stiffness of the zebrafish samples. In this paper, we demonstrated the versatility of this technique by measuring the mechanical elasticity of zebrafish embryos at different stages of development. The stiffness of zebrafish embryos was measured once per hour for 9 h. From the experimental results, we successfully quantified the stiffness change of zebrafish embryos during embryonic development.


Assuntos
Materiais Biocompatíveis/química , Módulo de Elasticidade , Embrião não Mamífero/fisiologia , Peixe-Zebra/crescimento & desenvolvimento , Animais , Dimetilpolisiloxanos/química , Desenvolvimento Embrionário , Análise de Elementos Finitos , Pinças Ópticas
15.
Biotechnol Appl Biochem ; 66(3): 445-453, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30817028

RESUMO

Cell function regulation is influenced by continuous biochemical and biophysical signal exchange within the body. Substrates with nano/micro-scaled topographies that mimic the physiological niche are widely applied for tissue engineering applications. As the cartilage niche is composed of several stimulating factors, a multifunctional substrate providing topographical features while having the capability of electrical stimulation is presented. Herein, we demonstrate a biocompatible and conductive chondrocyte cell-imprinted substrate using polydimethylsiloxane (PDMS) and carbon nanotubes (CNTs) as conductive fillers. Unlike the conventional silicon wafers or structural photoresist masters used for molding, cell surface topographical replication is challenging as biological cells showed extremely sensitive to chemical solvent residues during molding. The composite showed no significant difference compared with PDMS with regard to cytotoxicity, whereas an enhanced cell adhesion was observed on the conductive composite's surface. Integration of nanomaterials into the cell seeding scaffolds can make tissue regeneration process more efficient.


Assuntos
Materiais Biocompatíveis/química , Técnicas de Cultura de Células , Condrócitos/citologia , Dimetilpolisiloxanos/química , Nanotubos de Carbono/química , Animais , Materiais Biocompatíveis/farmacologia , Adesão Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Condrócitos/efeitos dos fármacos , Dimetilpolisiloxanos/farmacologia , Condutividade Elétrica , Teste de Materiais , Tamanho da Partícula , Coelhos , Propriedades de Superfície
16.
Biomed Microdevices ; 21(1): 26, 2019 03 02.
Artigo em Inglês | MEDLINE | ID: mdl-30826983

RESUMO

Polydimethylsiloxane (PDMS) has been the pivotal materials for microfluidic technologies with tremendous amount of lab-on-a-chip devices made of PDMS microchannels. While molding-based soft-lithography approach has been extremely successful in preparing various PDMS constructs, some complex features have to been achieved through more complicated microfabrication techniques that involve dry etching of PDMS. Several recipes have been reported for reactive ion etching (RIE) of PDMS; however, the etch rates present large variations, even for the same etching recipe, which poses challenges in adopting this process for device fabrication. Through systematic characterization of the Young's modulus of PDMS films and RIE etch rate, we show that the etch rate is closely related to the polymer cross-link density in the PDMS with a higher etch rate for a lower PDMS Young's modulus. Our results could provide guidance to the fabrication of microfluidic devices involving dry etching of PDMS.


Assuntos
Dimetilpolisiloxanos/química , Módulo de Elasticidade , Dispositivos Lab-On-A-Chip
17.
Sensors (Basel) ; 19(5)2019 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-30832271

RESUMO

Minimally invasive medical devices can greatly benefit from Narrow Band Imaging (NBI) diagnostic capabilities, as different wavelengths allow penetration of distinct layers of the gastrointestinal tract mucosa, improving diagnostic accuracy and targeting different pathologies. An important performance parameter is the light intensity at a given power consumption of the medical device. A method to increase the illumination intensity in the NBI diagnostic technique was developed and applied to minimally invasive medical devices (e.g., endoscopic capsules), without increasing the size and power consumption of such instruments. Endoscopic capsules are generally equipped with light-emitting diodes (LEDs) operating in the RGB (red, green, and blue) visible light spectrum. A polydimethylsiloxane (PDMS) µ-lens was designed for a maximum light intensity at the target area of interest when placed on top of the LEDs. The PDMS µ-lens was fabricated using a low-cost hanging droplet method. Experiments reveal an increased illumination intensity by a factor of 1.21 for both the blue and green LEDs and 1.18 for the red LED. These promising results can increase the resolution of NBI in endoscopic capsules, which can contribute to early gastric lesions diagnosis.


Assuntos
Dimetilpolisiloxanos/química , Luz , Imagem de Banda Estreita
18.
Mater Sci Eng C Mater Biol Appl ; 98: 572-583, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30813060

RESUMO

Endothelial cell (EC) dysfunction contributes to atherosclerosis, which is associated with arterial stiffening and fibronectin (FN) deposition, by ECs and smooth muscle cells (SMCs). The effect of stiffness on the EC/FN interaction and fibrillar adhesion formation has been poorly studied. An in vitro model was prepared that included FN-coated polydimethylsiloxane (PDMS) films with similar hydrophobicity and roughness but distinct Young's modulus values, mimicking healthy (1.0 MPa) and atherosclerotic (2.8 MPa) arteries. Human aortic abdominal endothelial cells (HAAECs) seeded on 1.0 MPa PDMS films spread over time and reached their maximum surface area faster than on 2.8 MPa PDMS films. In addition, HAAECs appeared to organize focal adhesion more rapidly on 1.0 MPa PDMS films, despite the similar cell binding domain accessibility to adsorbed FN. Interestingly, we also observed up to a ~5-fold increase in the percentage of HAAECs that had a well-developed fibrillar adhesion on 1.0 MPa compared to 2.8 MPa PDMS films as verified by integrin α5 subunits, tensin, and FN staining. This variation did not affect EC migration. These results suggest that there are favourable conditions for FN matrix assembly by ECs in early atherosclerosis rather than at advanced stages. Our in vitro model will therefore be helpful to understand the influence of bulk stiffness on cells involved in atherosclerosis.


Assuntos
Aorta Abdominal/citologia , Células Endoteliais/metabolismo , Adesões Focais/metabolismo , Ensaios de Migração Celular , Forma Celular , Dimetilpolisiloxanos/química , Módulo de Elasticidade , Células Endoteliais/citologia , Fibronectinas/metabolismo , Humanos , Interações Hidrofóbicas e Hidrofílicas , Cinética
19.
Lab Chip ; 19(5): 864-874, 2019 02 26.
Artigo em Inglês | MEDLINE | ID: mdl-30720811

RESUMO

Microfluidic organ-on-chip devices constructed from polydimethylsiloxane (PDMS) have proven useful in studying both beneficial and adverse effects of drugs, supplements, and potential toxicants. Despite multiple advantages, one clear drawback of PDMS-based devices is binding of hydrophobic chemicals to their exposed surfaces. Chemical binding to PDMS can change the timing and extent of chemical delivery to cells in such devices, potentially altering dose-response curves. Recent efforts have quantified PDMS binding for selected chemicals. Here, we test a wider set of nineteen chemicals using UV-vis or infrared spectroscopy to characterize loss of chemical from solution in two setups with different PDMS-surface-to-solution-volume ratios. We find discernible PDMS binding for eight chemicals and show that PDMS binding is strongest for chemicals with a high octanol-water partition coefficient (log P > 1.85) and low H-bond donor number. Further, by measuring depletion and return of chemical from solution over tens to hundreds of hours and fitting these results to a first order model of binding kinetics, we characterize partitioning into PDMS in terms of binding capacities per unit surface area and both forward and reverse rate constants. These fitted parameters were used to model the impact of PDMS binding on chemical transport and bioavailability under realistic flow conditions and device geometry. The models predict that PDMS binding could alter in-device cellular exposures for both continuous and bolus dosing schemes by up to an order of magnitude compared to nominal input doses.


Assuntos
Dimetilpolisiloxanos/química , Dimetilpolisiloxanos/farmacocinética , Dispositivos Lab-On-A-Chip , Técnicas Analíticas Microfluídicas , Sítios de Ligação , Disponibilidade Biológica , Dimetilpolisiloxanos/síntese química , Cinética , Estrutura Molecular
20.
Nano Lett ; 19(4): 2280-2290, 2019 04 10.
Artigo em Inglês | MEDLINE | ID: mdl-30775927

RESUMO

Cancer cell invasion through physical barriers in the extracellular matrix (ECM) requires a complex synergy of traction force against the ECM, mechanosensitive feedback, and subsequent cytoskeletal rearrangement. PDMS microchannels were used to investigate the transition from mesenchymal to amoeboid invasion in cancer cells. Migration was faster in narrow 3 µm-wide channels than in wider 10 µm channels, even in the absence of cell-binding ECM proteins. Cells permeating narrow channels exhibited blebbing and had smooth leading edge profiles, suggesting an ECM-induced transition from mesenchymal invasion to amoeboid invasion. Live cell labeling revealed a mechanosensing period in which the cell attempts mesenchymal-based migration, reorganizes its cytoskeleton, and proceeds using an amoeboid phenotype. Rho/ROCK (amoeboid) and Rac (mesenchymal) pathway inhibition revealed that amoeboid invasion through confined environments relies on both pathways in a time- and ECM-dependent manner. This demonstrates that cancer cells can dynamically modify their invasion programming to navigate physically confining matrix conditions.


Assuntos
Citoesqueleto/efeitos dos fármacos , Mesoderma/efeitos dos fármacos , Invasividade Neoplásica/genética , Neoplasias/genética , Fenômenos Biomecânicos , Adesão Celular/genética , Linhagem Celular Tumoral , Movimento Celular/genética , Citoesqueleto/genética , Dimetilpolisiloxanos/química , Dimetilpolisiloxanos/farmacologia , Matriz Extracelular/efeitos dos fármacos , Matriz Extracelular/genética , Humanos , Mesoderma/patologia , Invasividade Neoplásica/patologia , Neoplasias/patologia , Nylons/química , Nylons/farmacologia
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