Developing a Multifunctional Silk Fabric with Dual-Driven Heating and Rapid Photothermal Antibacterial Abilities Using High-Yield MXene Dispersions.

Two-dimensional material titanium carbide (Ti3C2Tx MXene) has been widely used for building diverse functional materials; however, the disadvantages of unsatisfactory yield and low concentration during the preparation process generally limit its large-scale promotion. In the present work, an MXene dispersion with enhanced yield (90%), high concentration (45 mg/mL), and excellent dispersibility was successfully prepared. Subsequently, the active MXene nanosheets were effectively in situ deposition onto the silk fiber by means of dip-coating, relying on van der Waals forces and hydrogen bonds. The obtained MXene-decorated silk fabric (MXene@silk) exhibits satisfactory electrical conductivity (170 mS/cm), excellent photothermal and electrothermal conversion properties, especially dual-drive energy conversion, rapid thermal responses, and long-term functional stability. Furthermore, UV protection factor of the fabric, and its antibacterial efficiency against Gram-negative Escherichia coli (E. coli) within 20 min of contact reach over 110 and 99%, respectively, demonstrating remarkable UV resistance and rapid photothermal antibacterial ability. Meanwhile, the fabric of MXene@silk still retains the original characteristics of breathability, softness, and skin-friendly properties compared to the untreated. The multifunctional fabric constructed through a facile and high-yield strategy shows a noticeable potential applying to smart textiles to meet people's multipurpose needs in the future.

Facile and Effective Fabrication of Highly UV-Resistant Silk Fabrics with Excellent Laundering Durability and Thermal and Chemical Stabilities.

As the most favored high-quality biopolymer, silk fiber is widely used in the textile and medical industries owing to its impressive mechanical properties, wear comfort properties, and biocompatibility. However, its photoinstability, chemical instability, and thermal instability seriously hinder its utilization in luxurious fashionable apparels. Therefore, we herein report the preparation of an ultrathin and uniform TiO2-Al2O3 cloth with a thickness of just six in a thousand of fiber on silkworm silk fiber via atomic layer deposition. In this ultrathin composite cloth, the outer TiO2 layer acts as a sacrificial ultraviolet (UV) absorbent to dissipate large amounts of UV energy. Free radicals and electrons generated by the TiO2 layer are effectively blocked outside the surface of the bulk silk fiber by the inner insulating Al2O3 layer. The excellent UV-resistance of the modified silk fiber was confirmed by a lack of fade in the silk fabric after exposure to UV light for 60 min (equal to continuous exposure to strong sunlight for 3285 days). Compared with silk fiber, the tenacity of the prepared SF-200Al2O3-800TiO2 increased by 18.9% even after sunlight exposure. In addition, both the chemical and thermal stabilities of the modified silk fiber were improved. This technology is expected to have potential applications in various fields, such as high-end fabric development and smart materials, and will further guide material design for future innovations in functional fibers and devices.

Commercial Silk-Based Electronic Yarns Fabricated Using Microwave Irradiation.

Electronic textiles (e-textiles) are being developed because of their potential applications in wearable and flexible electronics. However, complex procedures and chemical agents are required to synthesize carbon-based e-textiles. Pyroprotein-based e-textiles, obtained by the pyrolysis of silk proteins, consume large amounts of time and energy due to the high-temperature process (from 800 to 2800 °C). In this study, we report a novel method of fabricating pyroprotein-based electronic yarns (e-yarns) using microwave irradiation. Microwaves were applied to pyroprotein treated at 650 °C to remove numerous heteroatoms in a short time without the high-temperature process and chemical agents. The structural modulation was confirmed by Raman spectroscopy and X-ray photoelectron spectroscopy. We found a reduction in heteroatoms and enlargement of the carbon region. The temperature-dependent resistance was well explained by the fluctuation-induced tunneling model, which also showed structural modification. The electrical conductivity of the fabricated e-yarns was comparable to that of pyroprotein-based e-textiles heat-treated at 1000 °C (order of 102 S/cm) and showed electrical stability under bending.

Anderson light localization in biological nanostructures of native silk.

Light in biological media is known as freely diffusing because interference is negligible. Here, we show Anderson light localization in quasi-two-dimensional protein nanostructures produced by silkworms (Bombyx mori). For transmission channels in native silk, the light flux is governed by a few localized modes. Relative spatial fluctuations in transmission quantities are proximal to the Anderson regime. The sizes of passive cavities (smaller than a single fibre) and the statistics of modes (decomposed from excitation at the gain-loss equilibrium) differentiate silk from other diffusive structures sharing microscopic morphological similarity. Because the strong reflectivity from Anderson localization is combined with the high emissivity of the biomolecules in infra-red radiation, silk radiates heat more than it absorbs for passive cooling. This collective evidence explains how a silkworm designs a nanoarchitectured optical window of resonant tunnelling in the physically closed structures, while suppressing most of transmission in the visible spectrum and emitting thermal radiation.

Unexpected behavior of irradiated spider silk links conformational freedom to mechanical performance.

Silk fibers from Argiope trifasciata and Nephila inaurata orb-web weaving spiders were UV irradiated to modify the molecular weight of the constituent proteins. Fibers were characterized either as forcibly silked or after being subjected to maximum supercontraction. The effect of irradiation on supercontraction was also studied, both in terms of the percentage of supercontraction and the tensile properties exhibited by irradiated and subsequently supercontracted fibers. The effects of UV exposure at the molecular level were assessed by polyacrylamide gel electrophoresis and mass spectrometry. It is shown that UV-irradiated fibers show a steady decrease in their main tensile parameters, most notably, tensile strength and strain. The combination of the mechanical and biochemical data suggests that the restricted conformational freedom of the proteins after UV irradiation is critical in the reduction of these properties. Consequently, an adequate topological organization of the protein chains emerges as a critical design principle in the performance of spider silk.

Analytical markers for silk degradation: comparing historic silk and silk artificially aged in different environments.

Suitable analytical markers to assess the degree of degradation of historic silk textiles at molecular and macroscopic levels have been identified and compared with silk textiles aged artificially in different environments, namely (i) ultraviolet (UV) exposure, (ii) thermo-oxidation, (iii) controlled humidity and (iv) pH. The changes at the molecular level in the amino acid composition, the formation of oxidative moieties, crystallinity and molecular weight correlate well with the changes in the macroscopic properties such as brightness, pH and mechanical properties. These analytical markers are useful to understand the degradation mechanisms that silk textiles undergo under different degradation environments, involving oxidation processes, hydrolysis, chain scission and physical arrangements. Thermo-oxidation at high temperatures proves to be the accelerated ageing procedure producing silk samples that most resembled the degree of degradation of early seventeenth-century silk. These analytical markers will be valuable to support the textile conservation tasks currently being performed in museums to preserve our heritage.

Assessing the impact of synchrotron X-ray irradiation on proteinaceous specimens at macro and molecular levels.

Synchrotron radiation (SR) has become a preferred technique for the analysis of a wide range of archeological samples, artwork, and museum specimens. While SR is called a nondestructive technique, its effect on proteinaceous specimens has not been fully investigated at the molecular level. To investigate the molecular level effects of synchrotron X-ray on proteinaceous specimens, we propose a methodology where four variables are considered: (1) type of specimen: samples ranging from amino acids to proteinaceous objects such as silk, wool, parchment, and rabbit skin glue were irradiated; (2) synchrotron X-ray energy; (3) beam intensity; (4) irradiation time. Irradiated specimens were examined for both macroscopic and molecular effects. At macroscopic levels, color change, brittleness, and solubility enhancement were observed for several samples within 100 s of irradiation. At molecular levels, the method allowed one to quantify significant amino acid modifications. Aspartic acid (Asp), wool, parchment, and rabbit skin glue showed a significant increase in Asp racemization upon increasing irradiation time with rabbit skin glue showing the greatest increase in d-Asp formation. In contrast, Asp in silk, pure cystine (dimer of cysteine), and asparagine (Asn) did not show signs of racemization at the irradiation times studied; however, the latter two compounds showed significant signs of decomposition. Parchment and rabbit skin glue exhibited racemization of Asp, as well as racemization of isoleucine (Ile) and phenylalanine (Phe) after 100 s of irradiation with a focused beam. Under the experimental conditions and sample type and dimensions used here, more change was observed for focused and low energy (8 keV) beams than unfocused or higher energy (22 keV) beams. These results allow quantification of the change induced at the molecular level on proteinaceous specimens by synchrotron X-ray radiation and help to define accurate thresholds to minimize the probability of damage occurring to cultural heritage specimens. For most samples, damage was usually observed in the 1-10 s time scale, which is about an order of magnitude longer than SR studies of cultural heritage under X-ray fluorescence (XRF) mode; however, it is consistent with the duration of X-ray absorption spectroscopy (XAS) and microcomputed tomography (µCT) measurements.

The effect of sterilization methods on the physical properties of silk sericin scaffolds.

Protein-based biomaterials respond differently to sterilization methods. Since protein is a complex structure, heat, or irradiation may result in the loss of its physical or biological properties. Recent investigations have shown that sericin, a degumming silk protein, can be successfully formed into a 3-D scaffolds after mixing with other polymers which can be applied in skin tissue engineering. The objective of this study was to investigate the effectiveness of ethanol, ethylene oxide (EtO) and gamma irradiation on the sterilization of sericin scaffolds. The influence of these sterilization methods on the physical properties such as pore size, scaffold dimensions, swelling and mechanical properties, as well as the amount of sericin released from sericin/polyvinyl alcohol/glycerin scaffolds, were also investigated. Ethanol treatment was ineffective for sericin scaffold sterilization whereas gamma irradiation was the most effective technique for scaffold sterilization. Moreover, ethanol also caused significant changes in pore size resulting from shrinkage of the scaffold. Gamma-irradiated samples exhibited the highest swelling property, but they also lost the greatest amount of weight after immersion for 24 h compared with scaffolds obtained from other sterilization methods. The results of the maximum stress test and Young's modulus showed that gamma-irradiated and ethanol-treated scaffolds are more flexible than the EtO-treated and untreated scaffolds. The amount of sericin released, which was related to its collagen promoting effect, was highest from the gamma-irradiated scaffold. The results of this study indicate that gamma irradiation should have the greatest potential for sterilizing sericin scaffolds for skin tissue engineering.

Transmission X-ray microscopy of spider dragline silk.

We have investigated the structure of spider silk fibers from two different Nephila species and three different Araneus species by transmission X-ray microscopy (TXM). Single fibers and double fibers have been imaged. All images are in agreement with a homogenous density on length scales between the fiber diameter and the resolution of the instrument, which is about 25 nm.