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The recovery of injured nervous tissue, one of the main goals for regenerative therapeutic approaches, is often hindered by the limited axonal regeneration ability of the central nervous system (CNS). In this regard, the identification of scaffolds that support the reconstruction of functional neuronal tissues and guide the alignment of regenerating neurons is a major challenge in tissue engineering. Ideally, the usage of such scaffolds would promote and guide the axonal growth, a crucial phase for the restoration of neuronal connections and, consequently, the nerve function. Among the materials proposed as scaffolds for CNS regeneration, silk has been used to exploit its outstanding features as a biomaterial to promote axonal regeneration. In this study, we explore, for the first time, the possibility of using high-performance regenerated silk fibers obtained by straining flow spinning (SFS) to serve as scaffolds for inducing and guiding the axonal growth. It is shown that SFS fibers promote the spontaneous organization of dissociated cortical primary cells into highly interconnected cellular spheroid-like tissue formations. Neuronal projections (i.e., axons) from these cellular spheroids span hundreds of microns along the SFS fibers that act as guides and allow the connection of distant spheroids. In addition, it is also shown that SFS fibers serve as scaffolds for neuronal migration covering short and long distances. As a consequence, the usage of high-performance SFS fibers appears as a promising basis for the development of novel therapies, leading to directed axonal regeneration., Comunidad de Madrid (S2017/BMD-3760), Ministerio de Ciencia e Innovación (MAT2016-79832-R), Depto. de Biodiversidad, Ecología y Evolución, Centro de Vigilancia Sanitaria Veterinaria (VISAVET), TRUE, pub

The interaction between the plant lipid transfer protein Pru p 3 and phytosphingosine was assessed using an atomic force microscope. Phytosphingosine was covalently immobilized on DeepTipTM probes and Pru p 3 on MicroDeckTM functionalized substrates. Single-molecular interaction events between both molecules were retrieved and classified and the distribution for each one of the identified types was calculated. A success rate of over 70% was found by comparing the number of specific Pru p 3-phytosphingosine interaction events with the total number of recorded curves. The analysis of the distribution established among the various types of curves was further pursued to distinguish between those curves that can mainly be used for assessing the recognition between phytosphingosine (sensor molecule) and Pru p 3 (target molecule) in the context of affinity atomic force microscopy, and those that entail details of the interaction and might be employed in the context of force spectroscopy. The successful application of these functionalized probes and substrates to the characterization of the low-intensity hydrophobic interaction characteristic of this system is a clear indication of the potential of exploiting this approach with an extremely wide range of different biological molecules of interest. The possibility of characterizing molecular assembly events with single-molecule resolution offers an advantageous procedure to plough into the field of molecular biomimetics.

Age-associated changes in T-cell function play a central role in immunosenescence. The role of aging in the decreased T-cell repertoire, primarily because of thymic involution, has been extensively studied. However, increasing evidence indicates that aging also modulates the mechanical properties of cells and the internal ordering of diverse cell components. Cellular functions are generally dictated by the biophysical phenotype of cells, which itself is also tightly regulated at the molecular level. Based on previous evidence suggesting that the relative nuclear size contributes to variations of T-cell stiffness, here we examined whether age-associated changes in T-cell migration are dictated by biophysical parameters, in part through nuclear cytoskeleton organization and cell deformability. In this study, we first performed longitudinal analyses of a repertoire of 111 functional, biophysical and biomolecular features of the nucleus and cytoskeleton of mice CD4+ and CD8+ T cells, in both naive and memory state. Focusing on the pairwise correlations, we found that age-related changes in nuclear architecture and internal ordering were correlated with T-cell stiffening and declined interstitial migration. A similarity analysis confirmed that cell-to-cell variation was a direct result of the aging process and we applied regression models to identify biomarkers that can accurately estimate individuals' age. Finally, we propose a biophysical model for a comprehensive understanding of the results: aging involves an evolution of the relative nuclear size, in part through DNA-hypomethylation and nuclear lamin B1, which implies an increased cell stiffness, thus inducing a decline in cell migration., Ministerio de Economia y Competitividad, Comunidad de Madrid, Agencia Nacional de Investigación y Desarrollo (Chile), Depto. de Genética, Fisiología y Microbiología, Fac. de Ciencias Biológicas, TRUE, pub

Silk gut fibers were produced from the silkworm Samia cynthia ricini silk glands by the usual procedure of immersion in a mildly acidic solution and subsequent stretching. The morphology of the silk guts was assessed by scanning electron microscopy, and their microstructure was assessed by infrared spectroscopy and X-ray diffraction. It was found that both naturally spun and Samia silk guts share a common semicrystalline microstructure. The mechanical characterization of the silk guts revealed that these fibers show an elastomeric behavior when tested in water, and exhibit a genuine ground state to which the fiber may revert independently of its previous loading history. In spite of its large cross-sectional area compared with naturally spun silk fibers, Samia silk guts show values of work to fracture up to 160 MJ m, much larger than those of most of their natural counterparts, and establish a new record value for this parameter in silk guts.

A comparative analysis of T-lymphocyte mechanical data obtained from Micropipette Aspiration (MPA) andAtomic Force Microscopy (AFM) is presented. Results obtained byfitting the experimental data to simple Hertzand Theret models led to non-Gaussian distributions and significantly different values of the elastic moduliobtained by both techniques. The use of more refined models, taking into account thefinite size of cells (sim-plified double contact and Zhou models) reduces the differences in the values calculated for the elastic moduli.Several possible sources for the discrepancy between the techniques are considered. The analysis suggests thatthe local nature of AFM measurements compared with the more general character of MPA measurementsprobably contributed to the differences observed., Ministerio de Economía y Competitividad (MINECO), Comunidad de Madrid, Depto. de Genética, Fisiología y Microbiología, Fac. de Ciencias Biológicas, TRUE, pub

The conditions required for the emergence of supercontraction in regenerated silkworm (Bombyx mori) silk fibers are assessed through an experimental approach that combines the spinning of regenerated fibers with controlled properties and their characterization by 13C solid-state nuclear magnetic resonance (NMR). Both supercontracting and non-supercontracting regenerated fibers are produced using the straining flow spinning (SFS) technique from 13C labeled cocoons. The short-range microstructure of the fibers is assessed through 13C CP/MAS in air and 13C DD/MAS in water, and the main microstructural features are identified and quantified. The mechanical properties of the regenerated fibers and their microstructures are compared with those of natural silkworm silk. The combined analysis highlights two possible key elements as responsible for the emergence of supercontraction: (1) the existence of an upper and a lower limit of the amorphous phase compatible with supercontraction, and (2) the existence of two ordered phases, β-sheet A and B, which correspond to different packing arrangements of the protein chains.

The possibility of spinning regenerated silkworm (Bombyx mori) fibers from a range of aqueous dopes by using a biomimetic approach based on straining flow spinning is explored in this work. It is found that spinning conditions can be established that allow fibers to be produced from environmentally friendly dopes with fibroin concentrations even one order of magnitude lower than that of the natural system. However, it is also found that the spinning process is favored and that the mechanical properties of the fibers are improved when dopes with higher fibroin concentration are employed. Since highly concentrated fibroin solutions in water are unstable, a stabilizing agent is required in order to obtain a spinnable dope at such large protein concentrations. CaCl2 is found to be an adequate stabilizing agent compatible with the straining flow spinning process. The optimization of the spinning parameters leads to the production of high-performance fibers with a work to fracture comparable to that of the natural material.

The possibility of spinning regenerated silkworm (Bombyx mori) fibers from a range of aqueous dopes by using a biomimetic approach based on straining flow spinning is explored in this work. It is found that spinning conditions can be established that allow fibers to be produced from environmentally friendly dopes with fibroin concentrations even one order of magnitude lower than that of the natural system. However, it is also found that the spinning process is favored and that the mechanical properties of the fibers are improved when dopes with higher fibroin concentration are employed. Since highly concentrated fibroin solutions in water are unstable, a stabilizing agent is required in order to obtain a spinnable dope at such large protein concentrations. CaCl2 is found to be an adequate stabilizing agent compatible with the straining flow spinning process. The optimization of the spinning parameters leads to the production of high-performance fibers with a work to fracture comparable to that of the natural material.

The possibility of spinning regenerated silkworm (Bombyx mori) fibers from a range of aqueous dopes by using a biomimetic approach based on straining flow spinning is explored in this work. It is found that spinning conditions can be established that allow fibers to be produced from environmentally friendly dopes with fibroin concentrations even one order of magnitude lower than that of the natural system. However, it is also found that the spinning process is favored and that the mechanical properties of the fibers are improved when dopes with higher fibroin concentration are employed. Since highly concentrated fibroin solutions in water are unstable, a stabilizing agent is required in order to obtain a spinnable dope at such large protein concentrations. CaCl2 is found to be an adequate stabilizing agent compatible with the straining flow spinning process. The optimization of the spinning parameters leads to the production of high-performance fibers with a work to fracture comparable to that of the natural material.

The possibility of spinning regenerated silkworm (Bombyx mori) fibers from a range of aqueous dopes by using a biomimetic approach based on straining flow spinning is explored in this work. It is found that spinning conditions can be established that allow fibers to be produced from environmentally friendly dopes with fibroin concentrations even one order of magnitude lower than that of the natural system. However, it is also found that the spinning process is favored and that the mechanical properties of the fibers are improved when dopes with higher fibroin concentration are employed. Since highly concentrated fibroin solutions in water are unstable, a stabilizing agent is required in order to obtain a spinnable dope at such large protein concentrations. CaCl2 is found to be an adequate stabilizing agent compatible with the straining flow spinning process. The optimization of the spinning parameters leads to the production of high-performance fibers with a work to fracture comparable to that of the natural material.

The possibility of spinning regenerated silkworm (Bombyx mori) fibers from a range of aqueous dopes by using a biomimetic approach based on straining flow spinning is explored in this work. It is found that spinning conditions can be established that allow fibers to be produced from environmentally friendly dopes with fibroin concentrations even one order of magnitude lower than that of the natural system. However, it is also found that the spinning process is favored and that the mechanical properties of the fibers are improved when dopes with higher fibroin concentration are employed. Since highly concentrated fibroin solutions in water are unstable, a stabilizing agent is required in order to obtain a spinnable dope at such large protein concentrations. CaCl2 is found to be an adequate stabilizing agent compatible with the straining flow spinning process. The optimization of the spinning parameters leads to the production of high-performance fibers with a work to fracture comparable to that of the natural material.

This work summarizes the main principles and some of the most significant results of straining flow spinning (SFS), a technology developed originally by the authors of this work. The principles on which the technology is based, inspired by the natural spinning system of silkworms and spiders, are presented, as well as some of the main achievements of the technique. Among these achievements, spinning under environmentally friendly conditions, obtaining high-performance fibers, and imparting the fibers with emerging properties such as supercontraction are discussed. Consequently, SFS appears as an efficient process that may represent one of the first realizations of a biomimetic technology with a significant impact at the production level.

This work summarizes the main principles and some of the most significant results of straining flow spinning (SFS), a technology developed originally by the authors of this work. The principles on which the technology is based, inspired by the natural spinning system of silkworms and spiders, are presented, as well as some of the main achievements of the technique. Among these achievements, spinning under environmentally friendly conditions, obtaining high-performance fibers, and imparting the fibers with emerging properties such as supercontraction are discussed. Consequently, SFS appears as an efficient process that may represent one of the first realizations of a biomimetic technology with a significant impact at the production level.

This work summarizes the main principles and some of the most significant results of straining flow spinning (SFS), a technology developed originally by the authors of this work. The principles on which the technology is based, inspired by the natural spinning system of silkworms and spiders, are presented, as well as some of the main achievements of the technique. Among these achievements, spinning under environmentally friendly conditions, obtaining high-performance fibers, and imparting the fibers with emerging properties such as supercontraction are discussed. Consequently, SFS appears as an efficient process that may represent one of the first realizations of a biomimetic technology with a significant impact at the production level.

This work summarizes the main principles and some of the most significant results of straining flow spinning (SFS), a technology developed originally by the authors of this work. The principles on which the technology is based, inspired by the natural spinning system of silkworms and spiders, are presented, as well as some of the main achievements of the technique. Among these achievements, spinning under environmentally friendly conditions, obtaining high-performance fibers, and imparting the fibers with emerging properties such as supercontraction are discussed. Consequently, SFS appears as an efficient process that may represent one of the first realizations of a biomimetic technology with a significant impact at the production level.

This work summarizes the main principles and some of the most significant results of straining flow spinning (SFS), a technology developed originally by the authors of this work. The principles on which the technology is based, inspired by the natural spinning system of silkworms and spiders, are presented, as well as some of the main achievements of the technique. Among these achievements, spinning under environmentally friendly conditions, obtaining high-performance fibers, and imparting the fibers with emerging properties such as supercontraction are discussed. Consequently, SFS appears as an efficient process that may represent one of the first realizations of a biomimetic technology with a significant impact at the production level.

Mechanical deformability of cells is an important property for their function and development, as well as a useful marker of cell state. The classical technique of micropipette aspiration allows single-cell studies and we provide here a method to measure the two basic mechanical parameters, elastic modulus and Poisson’s ratio. The proposed method, developed from finite-element analysis of micropipette aspiration experiments, may be implemented in future technologies for the automated measurement of mechanical properties of cells, based on the micropipette aspiration technique or on the cell transit through flow constrictions. We applied this method to measure the elastic parameters of lymphocytes, in which the mechanical properties depend on their activation state. Additionally, we discuss in this work the accuracy of previous models to estimate the elastic modulus of cells, in particular the analytical model by Theret et al., widely used in the field. We show the necessity of using an improved model, taking into account the finite size of the cells, to obtain new insights that may remain hidden otherwise., Ministerio de Economía y Competitividad (MINECO), Depto. de Genética, Fisiología y Microbiología, Fac. de Ciencias Biológicas, TRUE, pub

As spun silkworm (Bombyx mori) silk fibers were compared in terms of their tensile behavior and microstructure with fibers subjected to different degumming treatments. Fibers were initially retrieved by forced silking directly from the worms and, either characterized in the as spun condition, or subjected to one of the following treatments: immersion in water, conventional degumming or degumming under longitudinally constrained conditions. Microstructure was assessed by X-ray diffraction and Raman spectroscopy. In addition, polyacrylamide gel electrophoresis was used to determine the influence of degumming on silk at a molecular level. Our study not only shows that degumming represents a major contribution to the accepted idea of silkworm silk as a highly variable material, but also provides new insights in the relationship between microstructure and tensile behavior in these fibers. In particular, it is shown that the arrangement of the hydrogen bond network in fibers subjected to different treatments plays a critical role in determining the mechanical behavior of silkworm silk.

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En este artículo se calcula la vida en fatiga de un recipiente a presión bajo cargas cíclicas de origen térmico. Se ofrece así un procedimiento general para calcular la vida en fatiga de cualquier estructura laminar sometida a cualquier clase de carga cíclica. El cálculo se realizó mediante integración de la Ley de Paris con una formulación biparamétrica , para incluir así la evolución de la forma de fisura. Se escribió un programa de ordenador para calcular numéricamente los caminos de integración mediante un esquema de Runge-Kutta, y también los lugares de iniciación y fractura y el valor de la integral, utilizando un criterio de fractura basado en el CTOD. Los resultados demuestran que la vida en fatiga de estos depósitos es suficientemente larga. Más aún, las trayectorias de fisuración correspondientes a las vidas en servicio más cortas son aquellas que conducen a fugas previas a la rotura., Peer Reviewed

El desarrollo de los sistemas de cálculo gráficos e interactivos ha permitido la aplicación de las tCcnicas de Mecánica de Fractura en r6girnen lineal y no lineal para el estudio de la propagación discreta de fisuras en estructuras de hormigón. En este artículo se presentan los modelos teóricos utilizados en Mecánica de Fractura para el estudio de la propagación de una grieta en un medio bidimensional así como las características del código utilizado en el análisis. Se incluyen dos ejemplos como muestra de la versatilidad y potencia de los sistemas de cálculo desarrollados., Discrete crack propagation in concrete structures is now feasible by using an interactive-graphics computer system. This paper presents a theoretical model, suitable for two-dimensional crack propagation in concrete, as well as a description of the computer code. Analysis of two practical situations exemplifies the versatility and power of the developed system., Peer Reviewed