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Abstract According to the Food and Agriculture Organization (FAO), roughly one-third of the total food produced is lost globally. The major cause of this wastage is the perishability of fruits and vegetables. Therefore, researchers have endeavored to develop an effective preservation technique. Our study explored the potential application of spider silk as an odourless and edible preservative coating for fruits. The spider silk was collected from spiders reared in the laboratory, following by degumming and dissolution to formulate the silk solution. For this study, apricots were selected as the model fruit. The apricots were dip coated with the formulated silk solution and allowed to dry. In order to enhance the beta sheet content of the silk coating, the fruits were exposed to water annealing for varying intervals of time under vacuum condition. The effect of silk coating and water annealing time period on preservation of fruits was then evaluated morphologically and gravimetrically. The results showed that the fruits, which were used as control, exhibited a greater degree of water loss and suffered from fungal attack. In contrast, the silk coated fruits showed less water loss and were protected from fungal attack. Therefore, the study provides compelling evidence regarding the application of spider silk as a preservative coating.

Over the past years, so‐called water annealing of TiO2 nanotube (NT) arrays has attracted considerable attention as a tool to enhance the nanotubes' photocatalytic properties. The present work investigates the effect of different water‐annealing treatments on TiO2 nanotubes and compares it to thermally annealed tubes. We find that the most effective water annealing is water immersion of TiO2 NT arrays at 70 °C for several days. The two main effects are i) a partial crystallization of the tubes to anatase, and ii) an etching of the tube walls that leads to a roughening of the walls and, thus, to a higher surface area. Under the best conditions, water annealing is almost as effective in providing enhanced photocatalytic AO7 degradation as a classic thermal annealing of the tubes. We, however, find that water annealed tubes – due to their only partial crystallization – do not perform well when used as photoelectrodes. For photocatalysis, most efficient is a combination of water annealing, followed by thermal annealing, which provides both a larger surface area and a high crystallinity. [ABSTRACT FROM AUTHOR]

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Melatonin, a hormone produced in the pineal gland, has been investigated for bone repair, remodeling, osteoporosis, as well as osseointegration of the implants. In this study, different concentrations of melatonin (0–2000-µM) were embedded into silk films annealed by methanol or water. Then, their capacity to differentiate human mesenchymal stem cells into osteoblasts was investigated for bone tissue regeneration. While methanol-annealed silk films have ~55% crystallinity, room-temperature water-annealed silk films have ~30% crystallinity by depending upon their different β-sheet contents. Melatonin-loaded silk films exhibited an initial burst release followed by a continuous release for up to 5 days, and the β-sheet content of silk films did not affect the release behavior of melatonin, an amphiphilic molecule. Moreover, human mesenchymal stem cells exhibited an increase in osteogenic markers such as alkaline phosphatase activity, osteocalcin, and runt-related transcription factor 2 expressions on the melatonin-loaded methanol-annealed silk films in both proliferation and osteogenic media. The bioactivity of the melatonin-modified silk films was further confirmed by the enhanced mineralization compared to silk films alone. This study demonstrated the feasibility of developing melatonin-loaded silk materials and the positive effect of releasing melatonin at micromolar concentrations on osteogenic differentiation of human mesenchymal stem cells cultured especially in osteogenic medium. [ABSTRACT FROM AUTHOR]

The present work presents a strategy to stabilize amorphous anodic self-organized TiO2 nanotube layers against morphological changes and crystallization upon extensive water soaking. The growth of needle-like nanoparticles was observed on the outer and inner walls of amorphous nanotube layers after extensive water soakings, in line with the literature on water annealing. In contrary, when TiO2 nanotube layers uniformly coated by thin TiO2 using atomic layer deposition (ALD) were soaked in water, the growth rates of needle-like nanoparticles were substantially reduced. We investigated the soaking effects of ALD TiO2 coatings with different thicknesses and deposition temperatures. Sufficiently thick TiO2 coatings (≈8.4 nm) deposited at different ALD process temperatures efficiently hamper the reactions between water and F− ions, maintain the amorphous state, and preserve the original tubular morphology. This work demonstrates the possibility of having robust amorphous 1D TiO2 nanotube layers that are very stable in water. This is very practical for diverse biomedical applications that are accompanied by extensive contact with an aqueous environment.

Spider silk has attracted extensive attention in the development of high-performance tissue engineering materials because of its excellent physical properties, biocompatibility, and biodegradability. Although high-molecular-weight recombinant spider silk proteins can be obtained through metabolic engineering of host bacteria, the solubility of the recombinant protein products is always poor. Strong denaturants and organic solvents have thus had to be exploited for their dissolution, and this seriously limits the applications of recombinant spider silk protein-based composite biomaterials. Herein, through adjusting the temperature, ionic strength, and denaturation time during the refolding process, we successfully prepared water-soluble recombinant spider major ampullate spidroin 1 (sMaSp1) with different repeat modules (24mer, 48mer, 72mer, and 96mer). Then, MaSp1 was introduced into the collagen matrix for fabricating MaSp1-collagen composite films. The introduction of spider silk proteins was demonstrated to clearly alter the internal structure of the composite films and improve the mechanical properties of the collagen-based films and turn the opaque protein films into transparency ones. More interestingly, the composite film prepared with sMaSp1 exhibited better performance in mechanical strength and cell adhesion compared to that prepared with water-insoluble MaSp1 (pMaSp1), which might be attributed to the effect of the initial dissolved state of MaSp1 on the microstructure of composite films. Additionally, the molecular weight of MaSp1 was also shown to significantly influence the mechanical strength (enhanced to 1.1- to 2.3-fold) and cell adhesion of composite films, and 72mer of sMaSp1 showed the best physical properties with good bioactivity. This study provides a method to produce recombinant spider silk protein with excellent water solubility, making it possible to utilize this protein under environmentally benign, mild conditions. This paves the way for the application of recombinant spider silk proteins in the development of diverse composite biomaterials.