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1.
Biofabrication ; 12(2): 025016, 2020 Feb 26.
Artigo em Inglês | MEDLINE | ID: mdl-31974317

RESUMO

Microwell arrays have emerged as three-dimensional substrates for cell culture due to their simplicity of fabrication and promise for high-throughput applications such as 3D cell-based assays for drug screening. To date, most microwells have had cylindrical geometries. Motivated by our previous findings that cells display 3D physiological characteristics when grown in the spherical micropores of monodisperse foam scaffolds (Lee et al 2013 Integr. Biol. 5 1447-55 and Lin et al 2011 Soft Matter 7 10010-6), here we engineered novel microwells shaped as spherical caps with obtuse polar angles, yielding narrow apertures. When used as bare substrates, these microwells were suitable for culturing cell spheroids; the narrow apertures sterically hindered unattached cultured cells from rolling out of microwells under agitation. When only the walls of the microwell were conjugated with extracellular matrix proteins, cells remained confined in the microwells. Epithelial cells proliferated and burst out of the aperture, and cell polarity was oriented based on the distribution of extracellular matrix proteins in the microwells. Surprisingly, single fibroblast cells in spherical wells of various diameters (40-100 µm) underwent cell-cycle arrest, while cells in circular cylindrical microwells continued to proliferate. Spatial confinement was not sufficient to cause cell-cycle arrest; however, confinement in a constant negative-curvature microenvironment led to cell-cycle arrest. Overall, these investigations demonstrate that this spherical microwell substrate constitutes a novel basic research tool for elucidating how cells respond to dimensionality and microenvironment with radii of curvature at the cellular length scale.

2.
iScience ; 14: 164-170, 2019 Apr 26.
Artigo em Inglês | MEDLINE | ID: mdl-30978667

RESUMO

Recently, many super-resolution technologies have been demonstrated, significantly affecting biological studies by observation of cellular structures down to nanometer precision. However, current super-resolution techniques mostly rely on wavefront engineering or wide-field imaging of signal blinking or fluctuation, and thus imaging depths are limited due to tissue scattering or aberration. Here we present a technique that is capable of imaging through an intact Drosophila brain with 20-nm lateral resolution at ∼200 µm depth. The spatial resolution is provided by molecular localization of a photoconvertible fluorescent protein Kaede, whose red form is found to exhibit blinking state. The deep-tissue observation is enabled by optical sectioning of spinning disk microscopy, as well as reduced scattering from optical clearing. Together these techniques are readily available for many biologists, providing three-dimensional resolution of densely entangled dendritic fibers in a complete Drosophila brain. The method paves the way toward whole-brain neural network studies and is applicable to other high-resolution bioimaging.

3.
Soft Matter ; 15(8): 1776-1784, 2019 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-30720830

RESUMO

Atomic force microscopy (AFM) is becoming an increasingly popular method for studying cell mechanics, however the existing analysis tools for determining the elastic modulus from indentation experiments are unable to quantitatively account for mechanical heterogeneity commonly found in biological samples. In this work, we numerically calculated force-indentation curves onto two-layered elastic materials using an analytic model. We found that the effect of the underlying substrate can be quantitatively predicted by the mismatch in elastic moduli and the homogeneous-case contact radius relative to the layer height for all tested probe geometries. The effect is analogous to one-dimensional Hookean springs in series and was phenomenologically modeled to obtain an approximate closed-form equation for the indentation force onto a two-layered elastic material which is accurate for up to two orders of magnitude mismatch in Young's modulus when the contact radius is less than the layer height. We performed finite element analysis simulations to verify the model and AFM microindentation experiments and macroindentation experiments to demonstrate its ability to deconvolute the Young's modulus of each layer. The model can be broadly used to quantify and serve as a guideline for designing and interpreting indentation experiments into mechanically heterogeneous samples.


Assuntos
Módulo de Elasticidade , Teste de Materiais , Dimetilpolisiloxanos , Análise de Elementos Finitos
4.
Biochem Biophys Res Commun ; 497(3): 869-875, 2018 03 11.
Artigo em Inglês | MEDLINE | ID: mdl-29470990

RESUMO

Cell migration is a critical process during development, tissue repair, and cancer metastasis. It requires complex processes of cell adhesion, cytoskeletal dynamics, and force generation. Lis1 plays an important role in the migration of neurons, fibroblasts and other cell types, and is essential for normal development of the cerebral cortex. Mutations in human LIS1 gene cause classical lissencephaly (smooth brain), resulting from defects in neuronal migration. However, how Lis1 may affect force generation in migrating cells is still not fully understood. Using traction force microscopy (TFM) with live cell imaging to measure cellular traction force in migrating NIH3T3 cells, we showed that Lis1 knockdown (KD) by RNA interference (RNAi) caused reductions in cell migration and traction force against the extracellular matrix (ECM). Immunostaining of cytoskeletal components in Lis1 KD cells showed disorganization of microtubules and actin filaments. Interestingly, focal adhesions at the cell periphery were significantly reduced. These results suggest that Lis1 is important for cellular traction force generation through the regulation of cytoskeleton organization and focal adhesion formation in migrating cells.


Assuntos
1-Alquil-2-acetilglicerofosfocolina Esterase/metabolismo , Movimento Celular , Citoesqueleto/metabolismo , Fibroblastos/citologia , Proteínas Associadas aos Microtúbulos/metabolismo , 1-Alquil-2-acetilglicerofosfocolina Esterase/genética , Animais , Fenômenos Biomecânicos , Fibroblastos/metabolismo , Adesões Focais/metabolismo , Camundongos , Proteínas Associadas aos Microtúbulos/genética , Células NIH 3T3 , Interferência de RNA
5.
J Phys Condens Matter ; 29(45): 455101, 2017 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-28920917

RESUMO

Matrix nanotopography plays an important role in regulating cell behaviors by providing spatial as well as mechanical cues for cells to sense. It has been proposed that nanoscale topography is possible to modulate the tensions which direct the formation of cytoskeleton and the organization of the membrane receptor within the cell, which in turn regulate intracellular mechanical and biochemical signaling. With current studies on this topic being performed mainly in 2D platforms, the question on how nanotopography can influence cell bahaviors in 3D environments has yet to be addressed. In this paper, we explored this question by placing cells in 3D hollow spherical polydimethylsiloxane scaffolds. After culturing rat embryonic fibroblast cells in two kinds of scaffold, one with smooth surface and the other with numerous nano-spikes, we observed that cells in the smooth scaffold have more anchoring sites and more focal adhesions than in the etched scaffold. Moreover, we found the presence of correlation between cortical actin, the important component for supporting cell attachment, and local cell geometry.


Assuntos
Actinas/química , Adesões Focais , Nanoestruturas , Adesão Celular/fisiologia , Córtex Cerebral , Citoesqueleto , Humanos , Propriedades de Superfície
6.
Tissue Eng Part A ; 22(11-12): 873-84, 2016 06.
Artigo em Inglês | MEDLINE | ID: mdl-27193498

RESUMO

One of the major limitations of tissue-engineered cartilage is poor integration of chondrocytes and scaffold structures with recipient tissue. To overcome this limitation, an expandable scaffold with a honeycomb-like structure has been developed using microfluidic technology. In this study, we evaluated the performance of this expandable gelatin scaffold seeded with rabbit chondrocytes in vivo. The chondrocyte/scaffold constructs were implanted into regions of surgically introduced cylindrical osteochondral defects in rabbit femoral condyles. At 2, 4, and 6 months postsurgery, the implanted constructs were evaluated by gross and histological examinations. As expected, the osteochondral defects, which were untreated or transplanted with blank scaffolds, showed no signs of repair, whereas the defects transplanted with chondrocyte/scaffold constructs showed significant cartilage regeneration. Furthermore, the expandable scaffolds seeded with chondrocytes had more regenerated cartilage tissue and better integration with the recipient tissue than autologous chondrocyte implantation. Biomechanical tests revealed that the chondrocyte/scaffold group had the highest compressive strength among all groups at all three time points and endured a similar compressive force to normal cartilage after 6 months of implantation. Histological examinations revealed that the chondrocytes were distributed uniformly within the scaffolds, maintained a normal phenotype, and secreted functional components of the extracellular matrix. Histomorphometric assessment showed a remarkable total interface of up to 87% integration of the expandable scaffolds with the host tissue at 6 months postoperation. In conclusion, the expandable scaffolds improved chondrocyte/scaffold construct integration with the host tissue and were beneficial for cartilage repair.


Assuntos
Cartilagem Articular/fisiologia , Engenharia Tecidual/métodos , Tecidos Suporte/química , Animais , Força Compressiva , Microbolhas , Modelos Animais , Coelhos , Regeneração , Cicatrização
7.
Sci Rep ; 6: 21253, 2016 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-26884253

RESUMO

The spatial boundary condition (SBC) arising from the surrounding microenvironment imposes specific geometry and spatial constraints that affect organogenesis and tissue homeostasis. Mesenchymal stromal cells (MSCs) sensitively respond to alterations of mechanical cues generated from the SBC. However, mechanical cues provided by a three-dimensional (3D) environment are deprived in a reductionist 2D culture system. This study investigates how SBC affects osteogenic differentiation of MSCs using 3D scaffolds with monodispersed pores and homogenous spherical geometries. MSCs cultured under SBCs with diameters of 100 and 150 µm possessed the greatest capability of osteogenic differentiation. This phenomenon was strongly correlated with MSC morphology, organization of actin cytoskeleton, and distribution of focal adhesion involving α2 and α5 integrins. Further silencing either α2 or α5 integrin significantly reduced the above mentioned mechanosensitivity, indicating that the α2 and α5 integrins as mechano-sensitive molecules mediate MSCs' ability to provide enhanced osteogenic differentiation in response to different spherical SBCs. Taken together, the findings provide new insights regarding how MSCs respond to mechanical cues from the surrounding microenvironment in a spherical SBC, and such biophysical stimuli should be taken into consideration in tissue engineering and regenerative medicine in conjunction with biochemical cues.


Assuntos
Diferenciação Celular , Células-Tronco Mesenquimais/citologia , Osteogênese , Nicho de Células-Tronco , Actinas/metabolismo , Adesão Celular , Técnicas de Cultura de Células , Sobrevivência Celular , Adesões Focais , Humanos , Integrina alfa2/metabolismo , Integrina alfa5/metabolismo , Esferoides Celulares , Tecidos Suporte
8.
Acta Biomater ; 32: 210-222, 2016 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-26790775

RESUMO

UNLABELLED: Osteogenic potential of mesenchymal stromal cells (MSCs) is mechanosensitive. It's affected by the mechanical properties of the cellular microenvironment, particularly its mechanical modulus. To explore the effect of mechanical modulus on osteogenesis in the third dimension (3D), this study used a novel polyacrylamide (PA) scaffold whose pores are monodisperse and spherical, the mechanical moduli of which can be tuned across a wide range. It was found that MSCs have similar proliferation rates in PA scaffolds independent of the matrix stiffness. The contractile force exerted by MSCs inside PA scaffolds was strong enough to deform the pores of scaffolds made of more compliant PAs (whose shear modulus, G'scaffold<4 kPa). Only scaffolds of the highest stiffness (G'scaffold=12 kPa) can withhold the contraction from MSCs. After osteogenic induction for 21 days, the expression profiles of marker genes showed that PA scaffolds of G'scaffold=12 kPa promoted osteogenesis of MSCs. Confocal image analysis demonstrated that there are more F-actin cytoskeletons and bundled stress fibers at higher matrix moduli in 2D and 3D. Moreover, the 3D porous structure promotes osteogenesis of MSCs more than 2D flat substrates. Together, the differences of cellular behaviors when cultured in 2D and 3D systems are evident. The PA scaffolds developed in the present study can be used for further investigation into the mechanism of MSC mechanosensing in the 3D context. STATEMENT OF SIGNIFICANCE: Mechanical properties of the microenvironment affect cellular behaviors, such as matrix stiffness. Traditionally, cell biological investigations have mostly employed cells growing on 2D substrates. The 3D porous PA scaffolds with the same topological conformation and pore sizes but different stiffness generated in this study showed that the differences of cellular behaviors in 2D and 3D systems are evident. Our 3D scaffolds provide insights into tissue engineering when stem cells incorporated with 3D scaffolds and support the future studies of cellular mechanobiology as well as the elucidation the role mechanical factor plays on the physiology and fate determination of MSCs in the 3D context.


Assuntos
Matriz Extracelular/metabolismo , Células-Tronco Mesenquimais/citologia , Osteogênese , Resinas Acrílicas/farmacologia , Actinas/metabolismo , Diferenciação Celular/efeitos dos fármacos , Diferenciação Celular/genética , Proliferação de Células/efeitos dos fármacos , Forma Celular/efeitos dos fármacos , Perfilação da Expressão Gênica , Regulação da Expressão Gênica/efeitos dos fármacos , Humanos , Hidrogéis/química , Células-Tronco Mesenquimais/efeitos dos fármacos , Células-Tronco Mesenquimais/metabolismo , Microfluídica , Osteogênese/efeitos dos fármacos , Osteogênese/genética , Porosidade , Tecidos Suporte/química
9.
Biomicrofluidics ; 8(5): 052109, 2014 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-25332736

RESUMO

We developed a microfluidic device to culture cellular spheroids of controlled sizes and suitable for live cell imaging by selective plane illumination microscopy (SPIM). We cocultured human umbilical vein endothelial cells (HUVECs) within the spheroids formed by hepatocellular carcinoma cells, and studied the distributions of the HUVECs over time. We observed that the migration of HUVECs depended on the size of spheroids. In the spheroids of ∼200 µm diameters, HUVECs migrated outwards to the edges within 48 h; while in the spheroids of ∼250 µm diameters, there was no outward migration of the HUVECs up to 72 h. In addition, we studied the effects of pro-angiogenic factors, namely, vascular endothelial growth factor (VEGF) and fibroblast growth factor (ß-FGF), on the migration of HUVECs in the carcinoma cell spheroid. The outward migration of HUVECs in 200 µm spheroids was hindered by the treatment with VEGF and ß-FGF. Moreover, some of the HUVECs formed hollow lumen within 72 h under VEGF and ß-FGF treatment. The combination of SPIM and microfluidic devices gives high resolution in both spatial and temporal domains. The observation of HUVECs in spheroids provides us insight on tumor vascularization, an ideal disease model for drug screening and fundamental studies.

10.
Biotechnol Bioeng ; 111(11): 2338-48, 2014 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-24895237

RESUMO

A tissue engineering chondrocytes/scaffold construct provides a promise to cartilage regeneration. The architecture of a scaffold such as interconnections, porosities, and pore sizes influences the fates of seeding cells including gene expression, survival, migration, proliferation, and differentiation thus may determine the success of this approach. Scaffolds of highly ordered and uniform structures are desirable to control cellular behaviors. In this study, a newly designed microfluidic device based on flow-focusing geometry was developed to fabricate gelatin scaffolds of ordered pores. In comparison with random foam scaffolds made by the conventional freeze-dried method, honeycomb-like scaffolds exhibit higher swelling ratio, porosity, and comparable compressive strength. In addition, chondrocytes grown in the honeycomb-like scaffolds had good cell viability, survival rate, glycosaminoglycans production, and a better proliferation than ones in freeze-dried scaffolds. Real-time PCR analysis showed that the mRNA expressions of aggrecan and collagen type II were up-regulated when chondrocytes cultured in honeycomb-like scaffolds rather than cells cultured as monolayer fashion. Oppositely, chondrocytes expressed collagen type II as monolayer culture when seeded in freeze-dried scaffolds. Histologic examinations revealed that cells produced proteoglycan and distributed uniformly in honeycomb-like scaffolds. Immunostaining showed protein expression of S-100 and collagen type II but negative for collagen type I and X, which represents the chondrocytes maintained normal phenotype. In conclusion, a highly ordered and honeycomb-like scaffold shows superior performance in cartilage tissue engineering. Biotechnol. Bioeng. 2014;111: 2338-2348. © 2014 Wiley Periodicals, Inc.


Assuntos
Biomimética , Cartilagem/crescimento & desenvolvimento , Regeneração Tecidual Guiada/métodos , Microfluídica/instrumentação , Microfluídica/métodos , Tecidos Suporte/química , Agrecanas/biossíntese , Animais , Proliferação de Células , Sobrevivência Celular , Condrócitos/fisiologia , Colágeno Tipo II/biossíntese , Perfilação da Expressão Gênica , Glicosaminoglicanos/metabolismo , Imuno-Histoquímica , Suínos
11.
Biomaterials ; 35(22): 5660-9, 2014 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-24746968

RESUMO

The inability to adequately vascularize tissues in vitro or in vivo is a major challenge in lung tissue engineering. A method that integrates stem cell research with 3D-scaffold engineering may provide a solution. We have successfully isolated mouse pulmonary stem/progenitor cells (mPSCs) by a two-step procedure and fabricated mPSC-compatible gelatin/microbubble-scaffolds using a 2-channel fluid jacket microfluidic device. We then integrated the cells and the scaffold to construct alveoli-like structures. The mPSCs expressed pro-angiogenic factors (e.g., b-FGF and VEGF) and induced angiogenesis in vitro in an endothelial cell tube formation assay. In addition, the mPSCs were able to proliferate along the inside of the scaffolds and differentiate into type-II and type-I pneumocytes The mPSC-seeded microbubble-scaffolds showed the potential for blood vessel formation in both a chick chorioallantoic membrane (CAM) assay and in experiments for subcutaneous implantation in severe combined immunodeficient (SCID) mice. Our results demonstrate that lung stem/progenitor cells together with gelatin microbubble-scaffolds promote angiogenesis as well as the differentiation of alveolar pneumocytes, resulting in an alveoli-like structure. These findings may help advance lung tissue engineering.


Assuntos
Células Epiteliais Alveolares/citologia , Gelatina/química , Pulmão/citologia , Neovascularização Fisiológica , Células-Tronco/citologia , Engenharia Tecidual/métodos , Tecidos Suporte/química , Animais , Diferenciação Celular , Células Cultivadas , Embrião de Galinha , Camundongos , Camundongos SCID , Microbolhas
12.
Integr Biol (Camb) ; 5(12): 1447-55, 2013 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-24132182

RESUMO

Traditionally, cell biological investigations have mostly employed cells growing on flat, two-dimensional, hard substrates, which are of questionable utility in mimicking microenvironments in vivo. We engineered a novel scaffold to achieve cell culture in the third dimension (3D), where fibroblasts lose the strong dorsal-ventral asymmetry in the distribution of cytoskeletal and adhesion components that is induced by growth on flat substrates. The design principle of our new 3D substrate was inspired by recent advances in engineering cellular microenvironments in which rigidity and the patterning of adhesion ligands were tuned on two-dimensional substrates; the engineered substrates enable independent control over biochemical and mechanical factors to elucidate how mechanical cues affect cellular behaviours. The 3D substrates consisted of polyacrylamide scaffolds of highly ordered, uniform pores coated with extracellular matrix proteins. We characterized important parameters for fabrication and the mechanical properties of polyacrylamide scaffolds. We then grew individual fibroblasts in the identical pores of the polyacrylamide scaffolds, examining cellular morphological, actin cytoskeletal, and adhesion properties. We found that fibroblasts sense the local rigidity of the scaffold, and exhibit a 3D distribution of actin cytoskeleton and adhesions that became more pronounced as the pore size was reduced. In small pores, we observed that elongated adhesions can exist without attachment to any solid support. Taken together, our results show that the use of negatively curved surfaces is a simple method to induce cell adhesions in 3D, opening up new degrees of freedom to explore cellular behaviours.


Assuntos
Resinas Acrílicas/química , Fibroblastos/citologia , Fibronectinas/metabolismo , Tecidos Suporte/química , Animais , Adesão Celular/fisiologia , Técnicas de Cultura de Células/métodos , Fibroblastos/metabolismo , Processamento de Imagem Assistida por Computador , Camundongos , Microfluídica/instrumentação , Microfluídica/métodos , Microscopia Confocal , Células NIH 3T3
13.
Biomicrofluidics ; 6(1): 14102-1410214, 2012 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-22288000

RESUMO

In this paper, we report a new method to incorporate 3D scaffold with electrotaxis measurement in the microfluidic device. The electrotactic response of lung cancer cells in the 3D foam scaffolds which resemble the in vivo pulmonary alveoli may give more insight on cellular behaviors in vivo. The 3D scaffold consists of ordered arrays of uniform spherical pores in gelatin. We found that cell morphology in the 3D scaffold was different from that in 2D substrate. Next, we applied a direct current electric field (EF) of 338 mV/mm through the scaffold for the study of cells' migration within. We measured the migration directedness and speed of different lung cancer cell lines, CL1-0, CL1-5, and A549, and compared with those examined in 2D gelatin-coated and bare substrates. The migration direction is the same for all conditions but there are clear differences in cell morphology, directedness, and migration speed under EF. Our results demonstrate cell migration under EF is different in 2D and 3D environments and possibly due to different cell morphology and/or substrate stiffness.

14.
Biomaterials ; 33(1): 120-7, 2012 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-21982587

RESUMO

Tissue engineering for cartilage regeneration provides an alternative to surgery for degenerative osteoarthritis. Recently, a highly organized three-dimensional (3D) alginate scaffold was prepared using a microfluidic device; this scaffold is effective for chondrocyte culture in vitro. The performance of this scaffold was further demonstrated; an alginate scaffold seeded with porcine chondrocytes was implanted in the dorsal subcutaneous site of SCID mice. The recipients were sacrificed at 2, 4, and 6 weeks after transplantation. The grafted implants retrieved from the subcutaneous site were analyzed with histologic examinations. Real-time PCR was used to identify the gene expression patterns of the chondrocytes. The hematoxylin and eosin staining showed that the chondrocytes survived normally in SCID mice; cartilage-like structures were formed after 4 weeks implantation. Immunohistochemical staining revealed cells secreted type II collagen, produced glycosaminoglycans (proved by alcian blue stain), and maintained the expression of S-100. On the other hand, the cells were negative for type I and type X collagen staining. PCR showed that the mRNA expressions of aggrecan and type II collagen were up-regulated at weeks two and four, while type I and type X collagen were down-regulated during the study period. In summary, this highly organized 3D alginate scaffold provided a suitable environment and maintained functional phenotypes for chondrocytes in this animal study.


Assuntos
Alginatos/química , Cartilagem/citologia , Engenharia Tecidual/métodos , Tecidos Suporte/química , Agrecanas/genética , Animais , Cartilagem/metabolismo , Condrócitos/citologia , Condrócitos/metabolismo , Colágeno Tipo II/genética , Ácido Glucurônico/química , Ácidos Hexurônicos/química , Imuno-Histoquímica , Camundongos , Camundongos SCID , Reação em Cadeia da Polimerase em Tempo Real
15.
Biomaterials ; 32(29): 7118-26, 2011 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-21724248

RESUMO

Osteoarthritis is a degenerative disease and frequently involves the knee, hip and phalangeal joints. Current treatments used in small cartilage defects including multiple drilling, abrasion arthroplasty, mosaicplasty, and autogenous chondrocyte transplantation, however, there are problems needed to be solved. The standard treatment for severe osteoarthritis is total joint arthroplasty. The disadvantages of this surgery are the possibility of implant loosening. Therefore, tissue engineering for cartilage regeneration has become a promising topic. We have developed a new method to produce a highly organized single polymer (alginate) scaffold using microfluidic device. Scanning electron microscope and confocal fluoroscope examinations showed that the scaffold has a regular interconnected porous structure in the scale of 250 µm and high porosity. The scaffold is effective in chondrocyte culture; the cell viability test (WST-1 assay), cell toxicity (lactate dehydrogenase assay), cell survival rate, extracellular matrix production (glycosaminoglycans contents), cell proliferation (DNA quantification), and gene expression (real-time PCR) all revealed good results for chondrocyte culture. The chondrocytes can maintain normal phenotypes, highly express aggrecan and type II collagen, and secrete a great deal of extracellular matrix when seeded in the alginate scaffold. This study demonstrated that a highly organized alginate scaffold can be prepared with an economical microfluidic device, and this scaffold is effective in cartilage tissue engineering.


Assuntos
Alginatos/química , Cartilagem/citologia , Microfluídica/métodos , Engenharia Tecidual/métodos , Tecidos Suporte/química , Agrecanas/metabolismo , Animais , Materiais Biocompatíveis/química , Células Cultivadas , Condrócitos/citologia , Condrócitos/fisiologia , Colágeno Tipo II/metabolismo , Força Compressiva , Expressão Gênica , Humanos , Teste de Materiais , Porosidade , Suínos
16.
ACS Appl Mater Interfaces ; 3(2): 204-8, 2011 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-21218787

RESUMO

A new type of polymer-assisted self-assembly of nanospheres at a water-air interface was uncovered. By adding merely 1-3 ppm of polyethylene oxide in the water, the polystyrene nanospheres, applicable to diameters ranging from 100 nm to 1 µm, were found to gradually move closer to each other and eventually form a close-packed structure confirmed from its diffraction pattern. As it turns out, polyethylene oxides are adsorbed onto the surface of polystyrene nanospheres, giving rise to the effective screening of coulomb repulsive force between nanospheres followed by the onset of polymer-bridging effect as demonstrated from the strong suppression of Brownian motion. The resulting monolayer of close-packed polymer/nanospheres hybrid at the water-air interface with area size more than 1 cm(2) are robust and can be transferred to a substrate of any kind without serious breaking due to surface tension tearing. Our finding may provide a further extension to the scope of nanosphere lithography technique.

17.
Biomicrofluidics ; 3(2): 22403, 2009 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-19693338

RESUMO

In this paper, we demonstrate for the first time the technique to using microfluidics to fabricate tissue engineering scaffolds with uniform pore sizes. We investigate both the bubble generation of the microfluidic device and the application of foam as a tissue engineering scaffold. Our microfluidic device consists of two concentric tapered channels, which are made by micropipettes. Nitrogen gas and aqueous alginate solution with Pluronic((R)) F127 surfactant are pumped through the inner and the outer channels, respectively. We observe rich dynamic patterns of bubbles encapsulated in the liquid droplets. The size of the bubble depends linearly on the gas pressure and inversely on the liquid flow rate. In addition, monodisperse bubbles self-assemble into crystalline structures. The liquid crystalline foams are further processed into open-cell solid foams. The novel foam gel was used as a scaffold to culture chondrocytes.

18.
Phys Rev E Stat Nonlin Soft Matter Phys ; 78(4 Pt 1): 041408, 2008 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-18999428

RESUMO

We study the packing of colloidal microspheres mixed with polymers in oil-in-water emulsion droplets by evaporation. The addition of polymers produces non-unique configurations of final clusters when the number of particles N inside the droplet is larger than 4. The cluster configurations are classified into three categories based on symmetry. Stablized colloidal clusters of spherical packings are observed. Our observations on packing process suggest the mechanisms which cause different and nonunique structures. The osmotic pressure and the interparticle interaction due to polymers changes the force balance between microspheres and result in different structures.

19.
Proc Natl Acad Sci U S A ; 102(9): 3208-12, 2005 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-15716362

RESUMO

Development of miniaturized devices that enable rapid and direct analysis of the specific binding of small molecules to proteins could be of substantial importance to the discovery of and screening for new drug molecules. Here, we report highly sensitive and label-free direct electrical detection of small-molecule inhibitors of ATP binding to Abl by using silicon nanowire field-effect transistor devices. Abl, which is a protein tyrosine kinase whose constitutive activity is responsible for chronic myelogenous leukemia, was covalently linked to the surfaces of silicon nanowires within microfluidic channels to create active electrical devices. Concentration-dependent binding of ATP and concentration-dependent inhibition of ATP binding by the competitive small-molecule antagonist STI-571 (Gleevec) were assessed by monitoring the nanowire conductance. In addition, concentration-dependent inhibition of ATP binding was examined for four additional small molecules, including reported and previously unreported inhibitors. These studies demonstrate that the silicon nanowire devices can readily and rapidly distinguish the affinities of distinct small-molecule inhibitors and, thus, could serve as a technology platform for drug discovery.


Assuntos
Proteínas/metabolismo , Trifosfato de Adenosina/metabolismo , Benzamidas , Mesilato de Imatinib , Nanotecnologia , Ressonância Magnética Nuclear Biomolecular , Piperazinas/metabolismo , Pirimidinas/metabolismo , Propriedades de Superfície
20.
Phys Rev E Stat Nonlin Soft Matter Phys ; 66(2 Pt 1): 020401, 2002 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-12241139

RESUMO

We compute the entropic interactions between two colloidal spheres immersed in a dilute suspension of semiflexible rods. Our model treats the semiflexible rod as a bent rod at fixed angle, set by the rod contour and persistence lengths. The entropic forces arising from this additional rotational degree of freedom are captured quantitatively by the model, and account for observations at short range in a recent experiment. Global fits to the interaction potential data suggest the persistence length of the fd virus is about two to three times smaller than the commonly used value of 2.2 microm.


Assuntos
Química Física/métodos , Entropia , Modelos Teóricos , Termodinâmica
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