RESUMO
A general, rapid, and undemanding method to generate at will functional oil-filled nanocapsules through nanoprecipitation is reported. On the basis of polymer and hexadecane/water/acetone phase diagrams, the composition can be set so that polymer chains preferentially stick at the interface of the oil droplets to create nanocapsules. The nanocapsules can be decorated with biorelevant molecules (biotin, fluorescent tags, metal nanoparticles) within the shell and loaded with hydrophobic molecules in a simple one-pot procedure.
Assuntos
Nanocápsulas/química , Acetona/química , Alcanos/química , Interações Hidrofóbicas e Hidrofílicas , Nanopartículas Metálicas/química , Polímeros/química , Água/químicaRESUMO
Cell migration is a highly coordinated process that occurs through the translation of biochemical signals into specific biomechanical events. The biochemical and structural properties of the proteins involved in cell motility, as well as their subcellular localization, have been studied extensively. However, how these proteins work in concert to generate the mechanical properties required to produce global motility is not well understood. Using intracellular microrheology and a fibroblast scratch-wound assay, we show that cytoskeleton reorganization produced by motility results in mechanical stiffening of both the leading lamella and the perinuclear region of motile cells. This effect is significantly more pronounced in the leading edge, suggesting that the mechanical properties of migrating fibroblasts are spatially coordinated. Disruption of the microtubule network by nocodazole treatment results in the arrest of cell migration and a loss of subcellular mechanical polarization; however, the overall mechanical properties of the cell remain mostly unchanged. Furthermore, we find that activation of Rac and Cdc42 in quiescent fibroblasts elicits mechanical behavior similar to that of migrating cells. We conclude that a polarized mechanics of the cytoskeleton is essential for directed cell migration and is coordinated through microtubules.
Assuntos
Movimento Celular , Fibroblastos/citologia , Fibroblastos/metabolismo , Células 3T3 , Animais , Bradicinina/metabolismo , Citoesqueleto/metabolismo , Análise de Fourier , Cinética , Camundongos , Microscopia de Fluorescência , Microscopia de Contraste de Fase , Microtúbulos/metabolismo , Nocodazol/farmacologia , Fator de Crescimento Derivado de Plaquetas/metabolismo , Fatores de Tempo , Cicatrização , Proteína cdc42 de Ligação ao GTP/metabolismo , Proteínas rac de Ligação ao GTP/metabolismo , Proteínas rho de Ligação ao GTP/metabolismoRESUMO
Local sol-gel transitions of the cytoskeleton modulate cell shape changes, which are required for essential cellular functions, including motility and adhesion. In vitro studies using purified cytoskeletal proteins have suggested molecular mechanisms of regulation of cytoskeleton mechanics; however, the mechanical behavior of living cells and the signaling pathways by which it is regulated remains largely unknown. To address this issue, we used a nanoscale sensing method, intracellular microrheology, to examine the mechanical response of the cell to activation of the small GTPase Rho. We observe that the cytoplasmic stiffness and viscosity of serum-starved Swiss 3T3 cells transiently and locally enhances upon treatment with lysophosphatidic acid, and this mechanical behavior follows a trend similar to Rho activity. Furthermore, the time-dependent activation of Rho decreases the degree of microheterogeneity of the cytoplasm. Our results reveal fundamental differences between intracellular elasticity and cellular tension and suggest a critical role for Rho kinase in the regulation of intracellular mechanics.
Assuntos
Citoesqueleto/metabolismo , Proteínas Serina-Treonina Quinases/fisiologia , Proteínas rho de Ligação ao GTP/metabolismo , Actinas/análise , Actinas/metabolismo , Animais , Fenômenos Biomecânicos , Técnicas Biossensoriais , Adesão Celular , Citoplasma/química , Citoplasma/ultraestrutura , Citoesqueleto/efeitos dos fármacos , Ativação Enzimática/efeitos dos fármacos , Peptídeos e Proteínas de Sinalização Intracelular , Lisofosfolipídeos/farmacologia , Camundongos , Nanotecnologia , Reologia/métodos , Células Swiss 3T3 , Quinases Associadas a rhoRESUMO
The preparation of polymeric particles and capsules by means of spontaneous droplet formation and subsequent polymer precipitation or synthesis is well-known. However, spontaneous emulsification is a phenomenon that has often been erroneously interpreted. This Minireview provides new insights into the preparation of metastable liquid dispersions by homogeneous liquid-liquid nucleation, and is based primarily on a recent study by Vitale and Katz (Langmuir, 2003, 19, 4105-4110). This spontaneous emulsification, which they named the Ouzo effect, occurs upon pouring, into water, a mixture of a totally water-miscible solvent and a hydrophobic oil--and optionally some water--thus generating long-lived small droplets, which are formed even though no surfactant is present. Herein, we review and reinterpret the most relevant publications on the synthesis of a variety of dispersions (pseudolatexes, silicone emulsions, biodegradable polymeric nanocapsules, etc.), which we believe have actually been synthesized using the Ouzo effect. The Ouzo effect may also become a substitute for high-shear techniques, which, to date have only been of limited utility on industrial scales.