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Two-photon fluorescent (TPF) Bombyx mori silk fibers were acquired for bioimaging by molecular recognition functionalization. In this context, 2,7-bis((E)-4-((E)-4-nitrostyryl)styryl)-9,9-dioctyl-9H-fluorene (NF) was adopted to functionalize silkworm silk fibers. NF exhibits a large two-photon absorption cross section, but has a low TPF quantum yield in the solid form due to the side-by-side (π–π) molecular stacking. In terms of the molecular recognition between the nitro groups of NF and the amide groups of silk fibroin, the silk fibers acquire the two-photon fluorescent emission with a significant enhancement of 350% in TPF quantum yield of NF molecules, compared with the solid state. For comparison, two other molecules, 2,7-bis((E)-4-methylstyryl)-9,9-dioctyl-9H-fluorene (MF1) and 2,7-bis((E)-4-((E)-4-methylstyryl)styryl)-9,9-dioctyl-9H-fluorene (MF2), were selected for similar experiments. These molecules show little effect due to the lack of molecular recognition. The TPF silk scaffolds were obtained, and high quality imaging of NF in cell culture was finally achieved, which has extremely relevant implications for biomedical applications.

This novel materials assembly technology endows the designated materials with additional/enhanced performance by fixing "functional components" into the materials. Such functional components are molecularly recognized and accommodated by the designated materials. In this regard, two-photon fluorescence (TPF) organic molecules and CdTe quantum dots (QDs) are adopted as functional components to functionalize silk fibers and films. TPF organic molecules, such as, 2,7-bis[2-(4-nitrophenyl) ethenyl]-9,9-dibutylfluorene (NM), exhibit TPF emission quenching because of the molecular stacking that leads to aggregation in the solid form. The specific recognition between -NO2 in the annealed fluorescent molecules and the -NH groups in the silk fibroin molecules decouples the aggregated molecules. This gives rise to a significant increase in the TPF quantum yields of the silk fibers. Similarly, as another type of functional components, CdTe quantum dots (QDs) with different sizes were also adopted in the silk functionalization method. Compared to QDs in solution the fluorescence properties of functionalized silk materials display a long stability at room temperature. As the functional materials are well dispersed at high quantum yields in the biocompatible silk a TPF microscope can be used to pursue 3D high-resolution imaging in real time of the TPF-silk scaffold.

In the biological world, numerous creatures such as butterfl ies, insects, and birds have exploited photonic structures to produce bicolor refl ections with important biofunctions in addition to unique brilliant structural coloration. Although the mimicking of bistructural color refl ection is possible, the fabrication involves a process of combined layer deposition techniques, which is complicated and less fl exible. Here, a bistructural color mimicking, based on silk fi broin, is reported using a simple and inexpensive self-assembly method. Silk-fi broin inverse opals with different spectral positions of bistructural color refl ection (i.e., ultraviolet and visible peaks, ultraviolet and near infrared peaks, and visible and near infrared peaks) are obtained by simply controlling their lattice constants. Furthermore, the inline and continuous tuning of the peak positions of bistructural color refl ection can be achieved by the humidity-induced cyclic contraction of silk fi broin. The potential applications of silk-fi broin photonic structures in eco-dying and multifunctional silk fabrics are also demonstrated.

Due to the advantage of hyperbranched polymers on controlling synthesis of nanoparticles (NPs), this paper presents a method to fabricate ZnO NPs coated cotton fabrics via in situ generation and deposition in one-step reaction with amino-terminated hyperbranched polymer (HBP-NH2) to explore its application in textile finishing. Firstly, the mechanism of this reaction was proposed in detail. The treated cotton fabrics were then characterized by field emission scanning electron microscopy (FESEM) and x-ray diffraction (XRD), and the ultraviolet (UV) protective properties and antibacterial activities of the fabrics were measured. The results indicated that ZnO NPs with a diameter around 80 nm dispersed on the surface of the cotton fabric well, the ultraviolet protection factor (UPF) value of the treated cotton fabric was 136 and the bacterial reduction rates against Staphylococcus aureus and Escherichia coli both exceeded 99%, when the concentration of HBP-NH2 and zinc nitrate were 16 g/L and 96 mM respectively.

In vitro drug testing requires long-term maintenance of hepatocyte liver specific functions. Hepatocytes cultured at a higher seeding density in a sandwich configuration exhibit an increased level of liver specific functions when compared to low density cultures due to the better cell to cell contacts that promote long term maintenance of polarity and liver specific functions. However, culturing hepatocytes at high seeding densities in a standard 24-well plate poses problems in terms of the mass transport of nutrients and oxygen to the cells. In view of this drawback, we have developed a polydimethylsiloxane (PDMS) bioreactor that was able to maintain the long-term liver specific functions of a hepatocyte sandwich culture at a high seeding density. The bioreactor was fabricated with PDMS, an oxygen permeable material, which allowed direct oxygenation and perfusion to take place simultaneously. The mass transport of oxygen and the level of shear stress acting on the cells were analyzed by computational fluid dynamics (CFD). The combination of both direct oxygenation and perfusion has a synergistic effect on the liver specific function of a high density hepatocyte sandwich culture over a period of 9 days.

This research presents a generic strategy to fabricate antibacterial textile through in situ synthesis of silver nanoparticles on the fabric with smart polymeric molecules. Silk fabric and polyamide network polymer (PNP) were chosen for this study. PNP which has numerous amino groups and three-dimensional structure was applied to entrap silver ions into silk fabric. The pretreated silk fabrics were heated by steam method to make silver nanoparticles synthesized in situ on them without any other reductant and linker to provide silk fabric with antibacterial properties. The results indicated that the treated silk fabrics had excellent antibacterial activity and laundering durability. The quantitative bacterial tests showed the bacterial reduction rates of Staphylococcus aureus and Escherichia coli were able to reach above 99 % with not more than 0.05 mmol/L of AgNO3. The whiteness of silk fabric only changed from 90.47 to 86.49. The antibacterial activity of the treated silk fabric was maintained at 98.86 % reduction even after being exposed to 30 consecutive home laundering conditions. In addition, the results of scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy confirmed that silver nanoparticles had generated and dispersed well in Ag0 form on the surface of silk fibers. The understanding acquired from this work will allow one to work with the preparation of other silver nanoparticles functional textiles with excellent antibacterial activities and laundering durability through this facile, eco-friendly in situ synthesis method.

Conventional two-dimensional cultures in monolayer and sandwich configuration have been used as a model for in vitro drug testing. However, these culture configurations do not present the actual in vivo liver cytoarchitecture for the hepatocytes cultures and thus they may compromise the cells liver-specific functions and their cuboidal morphology over longer term culture. In this study, we present a three-dimensional polydimethylsiloxane (PDMS) scaffold with interconnected spherical macropores for the culturing of rat liver cells (hepatocytes). The scaffolds were integrated into our perfusion enhanced bioreactor to improve the nutrients and gas supply for cell cultures. The liver-specific functions of the cell culture were assessed by their albumin and urea production, and the changes in the cell morphology were tracked by immunofluorescence staining over 9 days of culture period. N-Acetyl-Para-Amino-Phenol (acetaminophen) was used as drug model to investigate the response of cells to drug in our scaffold-bioreactor system. Our experimental results revealed that the perfusion enhanced PDMS-based scaffold system provides a more conducive microenvironment with better cell-to-cell contacts among the hepatocytes that maintains the culture specific enzymatic functions and their cuboidal morphology during the culturing period. The numerical simulation results further showed improved oxygen distribution within the culturing chamber with the scaffold providing an additional function of shielding the cell cultures from the potentially detrimental fluid induced shear stresses. In conclusion, this study could serve a crucial role as a platform for future preclinical hepatotoxicity testing. © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 30:418–428, 2014

In this chapter we review the properties and characterization of spider silk, particularly dragline silk, which is attracting increasing interest due to its marvelous properties. The spider's unique protein dope and natural spinning process play important roles in providing this unrivalled material with its characteristic structure that determines its strong and tough properties. In general, dragline silk is a semicrystalline material composed of crystallites embedded in an amorphous matrix. We introduce the widely applied techniques used to probe the structural characteristics of dragline silk. The inherent excellent mechanical properties of dragline silk, as well as the influence of silking conditions its mechanical properties, are reviewed. Models relating the structure to the mechanical properties are discussed, aiming to unravel the structural base for the unique mechanical properties. Supercontraction and cyclic contraction are two other interesting inherent properties of dragline silk; the former can maintain tension in a web after deformation by natural elements and the latter has the ability to perform work by subjecting the silk fibre to periodic cycling at high and low humidity. Current advances in possible applications of dragline silk in the biomedical and clinical fields using biomaterials of different forms, based on recombinant and reconstituted silk proteins, are discussed finally.

Antifreeze proteins (AFPs), occurring in some polar animals, plants, fungi, and other organisms, are capable of inhibiting ice freezing at subzero temperatures. The application of AFPs can be found in medicine and industry where low temperature storage is required and ice crystallization is damaging. This includes improved protection of blood platelets and human organs at low temperature, increasing the effectiveness of the destruction of malignant tumors in cryosurgery, and improvement of the smooth texture of frozen foods. In this review, the antifreeze mechanisms of AFPs are discussed, focusing on their inhibition effects on both ice nucleation and crystal growth. AFPs have been found to act in two stages. As a precursor to ice growth, ice nucleation is suppressed by the surface adsorption of AFPs to both ice nucleus and ice nucleators. At the second stage, in cases where inhibition of ice nucleation has had partial or no success, AFPs proceed to inhibit the growth of ice by adsorbing on specific surfaces of ice. Based on the understanding of structure–activity relationship, one is able to mimic the active domain of AFGPs and synthesize antifreeze glycoproteins by using ligation and polymerization strategies. However, further optimization of the chemistry, as well as new routes to mimic AFPs and functional analogues are needed to allow the routine production of quantities of pure material on commercially relevant scales.