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After an injury, the limited regenerative capacity of the central nervous system makes the reconnection and functional recovery of the affected nervous tissue almost impossible. To address this problem, biomaterials appear as a promising option for the design of scaffolds that promote and guide this regenerative process. Based on previous seminal works on the ability of regenerated silk fibroin fibers spun through the straining flow spinning (SFS) technique, this study is intended to show that the usage of functionalized SFS fibers allows an enhancement of the guidance ability of the material when compared with the control (nonfunctionalized) fibers. It is shown that the axons of the neurons not only tend to follow the path marked by the fibers, in contrast to the isotropic growth observed on conventional culture plates, but also that this guidance can be further modulated through the biofunctionalization of the material with adhesion peptides. Establishing the guidance ability of these fibers opens the possibility of their use as implants for spinal cord injuries, so that they may represent the core of a therapy that would allow the reconnection of the injured ends of the spinal cord. [ABSTRACT FROM AUTHOR]

At present, effective therapies to repair the central nervous system do not exist. Biomaterials might represent a new frontier for the development of neurorestorative therapies after brain injury and degeneration. In this study, an in situ gelling silk fibroin hydrogel was developed via the sonication-induced gelation of regenerated silk fibroin solutions. An adequate timeframe for the integration of the biomaterial into the brain tissue was obtained by controlling the intensity and time of sonication. After the intrastriatal injection of silk fibroin the inflammation and cell death in the implantation area were transient. We did not detect considerable cognitive or sensorimotor deficits, either as examined by different behavioral tests or an electrophysiological analysis. The sleep and wakefulness states studied by chronic electroencephalogram recordings and the fitness of thalamocortical projections and the somatosensory cortex explored by evoked potentials were in the range of normality. The methodology used in this study might serve to assess the biological safety of other biomaterials implanted into the rodent brain. Our study highlights the biocompatibility of native silk with brain tissue and extends the current dogma of the innocuousness of this biomaterial for therapeutic applications, which has repercussion in regenerative neuroscience. Statement of Significance The increasingly use of sophisticated biomaterials to encapsulate stem cells has changed the comprehensive overview of potential strategies for repairing the nervous system. Silk fibroin (SF) meets with most of the standards of a biomaterial suitable to enhance stem cell survival and function. However, a proof-of-principle of the in vivo safety and tolerability of SF implanted into the brain tissue is needed. In this study we have examined the tissue bioresponse and brain function after implantation of SF hydrogels. We have demonstrated the benign coexistence of silk with the complex neuronal circuitry that governs sensorimotor coordination and mechanisms such as learning and memory. Our results have repercussion in the development of advances strategies using this biomaterial in regenerative neuroscience. [ABSTRACT FROM AUTHOR]

True stress-true strain curves of naturally spun viscid line fibres retrieved directly from the spiral of orb-webs built by Argiope trifasciata spiders were measured using a novel methodology. This new procedure combines a method for removing the aqueous coating of the fibres and a technique that allows the accurate measurement of their cross-sectional area. Comparison of the tensile behaviour of different samples indicated that naturally spun viscid lines show a large variability, comparable to that of other silks, such as major ampullate gland silk and silkworm silk. Nevertheless, application of a statistical analysis allowed the identification of two independent parameters that underlie the variability and characterize the observed range of true stress-true strain curves. The combination of this result with previous mechanical and microstructural data suggested the assignment of these two independent effects to the degree of alignment of the protein chains and to the local relative humidity, which, in turn, depends on the composition of the viscous coating and on the external environmental conditions. [ABSTRACT FROM AUTHOR]

Spider silk is a natural material with unique properties and a great potential for engineering and biomedical applications. In spite of its simple composition and highly conserved and stereotypical production, spider silks show a wide range of variability in their mechanical properties which, for long, have defied their classification and standardization. Here we propose to launch the Spider Silk Standardization Initiative (S3I), a methodology based on the definition of the α* parameter, in an attempt to define a systematic procedure to classify the tensile properties exhibited by major ampullate gland silk (MAS) spun by Entelegynae spiders. The α* parameter is calculated from the comparison of the true stress-true strain curve of any MAS fiber after being subjected to maximum supercontraction, with the true stress-true strain curve of the species Argiope aurantia , which is set as a reference curve. This work presents the details of the S3I methodology and, as an example, shows its application to an assemblage of Entelegynae spiders from different families collected at the Pantanos de Villa wetlands (Lima, Peru). The systematic and objective classification of the tensile properties of MAS fibers allowed by the S3I will offer insights into key aspects of the biological evolution of the material, and address questions such as how history and adaptation contributed to shape those properties. In addition, it will surely have far reaching consequences in fields such as Materials Science, and Molecular and Evolutionary Biology, by organizing the range of tensile properties exhibited by spider silk fibers. Image 1 • The variability of MA spider silk fibers can be classified with a single parameter. • The Spider Silk Standardization Initiative (S3I) is set out to classify MA silk. • S3I is based on a simple methodology applicable by laboratories worldwide. [ABSTRACT FROM AUTHOR]

The adhesion forces of cells to peptide-coated functionalized materials were assessed through the Single Cell Force Spectroscopy (SCFS) technique in order to develop a methodology that allows the fast selection of peptide motifs that favor the interaction between cells and the biomaterial. Borosilicate glasses were functionalized using the activated vapor silanization process (AVS) and subsequently decorated with an RGD- containing peptide using the EDC/NHS crosslinking chemistry. It is shown that the RGD-coated glass induces larger attachment forces on mesenchymal stem cell cultures (MSCs), compared to the bare glass substrates. These higher forces correlate well with the enhanced adhesion of the MSCs observed on RGD-coated substrates through conventional adhesion cell cultures and inverse centrifugation tests. The methodology based on the SCFS technique presented in this work constitutes a fast procedure for the screening of new peptides or their combinations to select candidates that may enhance the response of the organism to the implant of the functionalized biomaterials. [ABSTRACT FROM AUTHOR]