Fine Structural Analysis of Degummed Fibroin Fibers Reveals Its Superior Mechanical Capabilities.

Bombyx mori silk fibroin fibers constitute a class of protein building blocks capable of functionalization and reprocessing into various material formats. The properties of these fibers are typically affected by the intense thermal treatments needed to remove the sericin gum coating layer. Additionally, their mechanical characteristics are often misinterpreted by assuming the asymmetrical cross-sectional area (CSA) as a perfect circle. The thermal treatments impact not only the mechanics of the degummed fibroin fibers, but also the structural configuration of the resolubilized protein, thereby limiting the performance of the resulting silk-based materials. To mitigate these limitations, we explored varying alkali conditions at low temperatures for surface treatment, effectively removing the sericin gum layer while preserving the molecular structure of the fibroin protein, thus, maintaining the hierarchical integrity of the exposed fibroin microfiber core. The precise determination of the initial CSA of the asymmetrical silk fibers led to a comprehensive analysis of their mechanical properties. Our findings indicate that the alkali surface treatment raised the Young's modulus and tensile strength, by increasing the extent of the fibers' crystallinity, by approximately 40 % and 50 %, respectively, without compromising their strain. Furthermore, we have shown that this treatment facilitated further production of high-purity soluble silk protein with rheological and self-assembly characteristics comparable to those of native silk feedstock, initially stored in the animal's silk gland. The developed approaches benefits both the development of silk-based materials with tailored properties and the proper mechanical characterization of asymmetrical fibrous biological materials made of natural building blocks.

Keratins and lipids in ethnic hair.

Human hair has an important and undeniable relevance in society due to its important role in visual appearance and social communication. Hair is mainly composed of structural proteins, mainly keratin and keratin associated proteins and lipids. Herein, we report a comprehensive study of the content and distribution of the lipids among ethnic hair, African, Asian and Caucasian hair. More interestingly, we also report the study of the interaction between those two main components of hair, specifically, the influence of the hair internal lipids in the structure of the hair keratin. This was achieved by the use of a complete set of analytical tools, such as thin layer chromatography-flame ionization detector, X-ray analysis, molecular dynamics simulation and confocal microscopy. The experimental results indicated different amounts of lipids on ethnic hair compositions and higher percentage of hair internal lipids in African hair. In this type of hair, the axial diffraction of keratin was not observed in X-ray analysis, but after hair lipids removal, the keratin returned to its typical packing arrangement. In molecular dynamic simulation, lipids were shown to intercalate dimers of keratin, changing its structure. From those results, we assume that keratin structure may be influenced by higher concentration of lipids in African hair.

Micro and nano-scale compartments guide the structural transition of silk protein monomers into silk fibers.

Silk is a unique, remarkably strong biomaterial made of simple protein building blocks. To date, no synthetic method has come close to reproducing the properties of natural silk, due to the complexity and insufficient understanding of the mechanism of the silk fiber formation. Here, we use a combination of bulk analytical techniques and nanoscale analytical methods, including nano-infrared spectroscopy coupled with atomic force microscopy, to probe the structural characteristics directly, transitions, and evolution of the associated mechanical properties of silk protein species corresponding to the supramolecular phase states inside the silkworm's silk gland. We found that the key step in silk-fiber production is the formation of nanoscale compartments that guide the structural transition of proteins from their native fold into crystalline ß-sheets. Remarkably, this process is reversible. Such reversibility enables the remodeling of the final mechanical characteristics of silk materials. These results open a new route for tailoring silk processing for a wide range of new material formats by controlling the structural transitions and self-assembly of the silk protein's supramolecular phases.

Nanotechnology solutions to restore antibiotic activity.

This review focuses on the development of nanoparticle systems that enables to enhance and restore the antibiotic activity for drug-resistant organisms. New and more aggressive antibiotic resistant bacteria and parasites calls for the development of new therapeutic strategies to overcome the inefficiency of conventional antibiotics and bypass treatment limitations related to these pathologies. Nanostructured biomaterials, nanoparticles in particular, have unique physicochemical properties such as ultra-small and controllable size, large surface area to mass ratio, high reactivity, and functionalizable structure. These properties can be applied to facilitate the administration of antimicrobial drugs, thereby overcoming some of the limitations in traditional antimicrobial therapeutics. Here the current progress and challenges in synthesizing nanoparticle platforms for restoring activity of various antimicrobial drugs are reviewed with an emphasis on antibiotics. We also call attention to the need to unite the shared interest between nanoengineers and microbiologists in developing nanotechnology for the treatment of microbial diseases.