Catálogo de publicaciones - revistas

<jats:p>Valued for their innovation potential, biomaterials efforts in China prosper.</jats:p>

<jats:p>Nanoparticle-based drug delivery systems have been developed to improve the efficacy and reduce the systemic toxicity of a wide range of drugs. Although clinically approved nanoparticles have consistently shown value in reducing drug toxicity, their use has not always translated into improved clinical outcomes. This has led to the development of “multifunctional” nanoparticles, where additional capabilities like targeting and image contrast enhancement are added to the nanoparticles. However, additional functionality means additional synthetic steps and costs, more convoluted behavior and effects in vivo, and also greater regulatory hurdles. The trade-off between additional functionality and complexity is the subject of ongoing debate and the focus of this Review.</jats:p>

<jats:p>Analogies with inert soft condensed matter—such as viscoelastic liquids, pastes, foams, emulsions, colloids, and polymers—can be used to investigate the mechanical response of soft biological tissues to forces. A variety of experimental techniques and biophysical models have exploited these analogies allowing the quantitative characterization of the mechanical properties of model tissues, such as surface tension, elasticity, and viscosity. The framework of soft matter has been successful in explaining a number of dynamical tissue behaviors observed in physiology and development, such as cell sorting, tissue spreading, or the escape of individual cells from a tumor. However, living tissues also exhibit active responses, such as rigidity sensing or cell pulsation, that are absent in inert soft materials. The soft matter models reviewed here have provided valuable insight in understanding morphogenesis and cancer invasion and have set bases for using tissue engineering within medicine.</jats:p>

<jats:p>Articular cartilage was predicted to be one of the first tissues to successfully be regenerated, but this proved incorrect. In contrast, bone (but also vasculature and cardiac tissues) has seen numerous successful reparative approaches, despite consisting of multiple cell and tissue types and, thus, possessing more complex design requirements. Here, we use bone-regeneration successes to highlight cartilage-regeneration challenges: such as selecting appropriate cell sources and scaffolds, creating biomechanically suitable tissues, and integrating to native tissue. We also discuss technologies that can address the hurdles of engineering a tissue possessing mechanical properties that are unmatched in human-made materials and functioning in environments unfavorable to neotissue growth.</jats:p>

<jats:p>New manufacturing technologies under the banner of rapid prototyping enable the fabrication of structures close in architecture to biological tissue. In their simplest form, these technologies allow the manufacture of scaffolds upon which cells can grow for later implantation into the body. A more exciting prospect is the printing and patterning in three dimensions of all the components that make up a tissue (cells and matrix materials) to generate structures analogous to tissues; this has been termed bioprinting. Such techniques have opened new areas of research in tissue engineering and regenerative medicine.</jats:p>

<jats:title>Nanotube Yarn Actuators</jats:title> <jats:p> Actuators are used to convert heat, light, or electricity into a twisting or tensile motion, and are often described as artificial muscles. Most materials that show actuation either provide larger forces with small-amplitude motions, such as the alloy NiTi, or provide larger motions with much less force, such as polymeric materials. Other problems with such actuators can include slow response times and short lifetimes. <jats:bold> Lima <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="928" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1226762">928</jats:related-article> , see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6109" page="893" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1230428">Schulz</jats:related-article> </jats:bold> ) show that a range of guest-filled, twist-spun carbon nanotube yarns can be used for linear or torsional actuation, can solve the problems of speed and lifetime, and do not require electrolytes for operation. </jats:p>

<jats:title>Channels from DNA</jats:title> <jats:p> Artificial transmembrane channels are of interest for applications, such as sensing and modifying cell signaling. <jats:bold> Langecker <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="932" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1225624">932</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6109" page="890" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1231024">Strano</jats:related-article> </jats:bold> ) used α-hemolysin as a model for creating a nanostructure with DNA origami that, when inserted into a lipid bilayer membrane, acted as a membrane channel. Ion channel responses were similar to those measured for natural ion channels, and channels that protruded further into the membrane exhibited greater gating responses. The channels were used to detect single-DNA molecules. </jats:p>

<jats:title>Coherent Heat Flow</jats:title> <jats:p> Typically, heat in solids is transported incoherently because phonons scatter at interfaces and defects. <jats:bold> Luckyanova <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="936" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1225549">936</jats:related-article> ) grew super-lattice films made from one to nine repeats of layers of GaAs and AlAs, each 12-nm thick. Thermal conductivity through this sandwich structure increased linearly with the number of superlattice repeats, which is consistent with theoretical simulations of coherent heat transport. </jats:p>

<jats:title>Magnetic Pallasites</jats:title> <jats:p> The origin of pallasite meteorites seems to defy explanation because their main constituents—iron and olivine—should have segregated into layers inside their parent body. The generally accepted model suggests that they formed at the coremantle boundary of an asteroid. <jats:bold> Tarduno <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="939" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1223932">939</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6109" page="897" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1230532">Weiss</jats:related-article> </jats:bold> ) measured a remnant magnetization in olivine crystals of two pallasite meteorites and conclude that a dynamo must have operated in their parent body, providing further evidence that some asteroids were capable of dynamo generation. The data, together with thermal modeling, suggest that some pallasites could have formed when liquid FeNi from the core of an impacting asteroid was injected into the mantle of a large protoplanet. </jats:p>