Interfacial Adsorption and Corrosion Inhibition Behavior of Environmentally Friendly Imidazole Derivatives for Copper in the Marine Environment.

Copper and copper alloys are commonly used in industry due to their excellent mechanical properties, making research on the corrosion resistance of copper of great significance. The corrosion inhibition properties of 2-imidazolidinone and allantoin for copper in 3.5 wt % NaCl were studied by weight loss and electrochemical tests. Changes in the density of the copper corrosion current and the impedance module indicated that 2-imidazolidinone and allantoin exhibited cathodic corrosion inhibitors and a valid protective effect. Meanwhile, the weight loss tests showed that the inhibition efficiency of 2-imidazolidinone and allantoin at 3 mM reached 98.94% and 97.82%, respectively. The surface physiochemical properties were qualitatively and quantitatively studied by using SEM-EDS, XPS, white light interferometry, and contact angle analysis. The interfacial adsorption behavior revealed by QCM, synchrotron radiation micro-infrared, and adsorption isotherm analysis indicated that both imidazole derivatives formed an effective and rigid physical adsorption film and obeyed the Langmuir adsorption model on copper, while both the mass and thickness of the adsorption film formed by 2-imidazolidinone were higher than those of allantoin. This study contributed to an in-depth understanding of the interfacial adsorption behavior and corrosion inhibition ability of 2-imidazolidinone and allantoin and provided guidelines for the design and development of novel heterocycles as potential corrosion inhibitors for copper in marine environments. In particular, copper was used as a corrosion inhibitor in seawater storage and transport equipment.

Simultaneous band-gap narrowing and carrier-lifetime prolongation of organic-inorganic trihalide perovskites.

The organic-inorganic hybrid lead trihalide perovskites have been emerging as the most attractive photovoltaic materials. As regulated by Shockley-Queisser theory, a formidable materials science challenge for improvement to the next level requires further band-gap narrowing for broader absorption in solar spectrum, while retaining or even synergistically prolonging the carrier lifetime, a critical factor responsible for attaining the near-band-gap photovoltage. Herein, by applying controllable hydrostatic pressure, we have achieved unprecedented simultaneous enhancement in both band-gap narrowing and carrier-lifetime prolongation (up to 70% to ∼100% increase) under mild pressures at ∼0.3 GPa. The pressure-induced modulation on pure hybrid perovskites without introducing any adverse chemical or thermal effect clearly demonstrates the importance of band edges on the photon-electron interaction and maps a pioneering route toward a further increase in their photovoltaic performance.

Synchrotron FTIR microspectroscopy reveals early adipogenic differentiation of human mesenchymal stem cells at single-cell level.

Human mesenchymal stem cells (hMSCs) have been used as an ideal in vitro model to study human adipogenesis. However, little knowledge of the early stage differentiation greatly hinders our understanding on the mechanism of the adipogenesis processes. In this study, synchrotron radiation-based Fourier transform infrared (SR-FTIR) microspectroscopy was applied to track the global structural and compositional changes of lipids, proteins and nucleic acids inside individual hMSCs along the time course. The multivariate analysis of the SR-FTIR spectra distinguished the dynamic and significant changes of the lipids and nucleic acid at early differentiation stage. Importantly, changes of lipid structure during early days (Day 1-3) of differentiation might serve as a potential biomarker in identifying the state in early differentiation at single cell level. These results proved that SR-FTIR is a powerful tool to study the stem cell fate determination and early lipogenesis events.

Study on nanobubble generation: saline solution/water exchange method.

In a recently introduced method for nanobubble generation, water is replaced with NaCl solution. It has the same mechanism as alcohol/water exchange: a liquid of higher gas solubility is used to replace one of lower gas solubility. Herein, the opposite process is realized by replacement of saline solutions with water. Interestingly, nanobubbles are also observed by AFM when different concentrations and valences of saline liquids are employed.

Investigation on the temperature difference method for producing nanobubbles and their physical properties.

In recent years, the possibility of nanobubbles at the solid-liquid interface has drawn wide attention in the scientific community and industry. Thus the search for evidences for the existence of nanobubbles became a scientific hotspot. To produce interfacial nanobubbles, a systematic experiment, called the temperature difference method, is carried out by replacing low temperature water (LTW) with high temperature water (HTW) at the highly-oriented pyrolytic graphite (HOPG)-water interface. When LTW (4 °C) is mixed with HTW (25-40 °C), nanobubbles are observed by atomic force microscopy (AFM), and their size, density and total volume per square micrometer are measured. Furthermore, pancake-like gas layers and the coexistence of nanobubbles on top of the pancake layers are also observed.

Synchrotron radiation-based Fourier transform infrared microspectroscopy investigation of WRL68 cells treated with doxorubicin.

Doxorubicin is an effective chemotherapeutic agent applied in a wide variety of cancers. Despite its potent anticancer activity towards cancer cells, doxorubicin is also toxic to noncancerous cells. Therefore, doxorubicin can cause serious side effects in various organs, especially when dose escalation is required for patients with advanced disease. The liver is the major detoxification organ that metabolizes drugs, and hepatotoxicity is one of the most common adverse effects of doxorubicin administration. However, the exact mechanisms of doxorubicin-induced hepatotoxicity have not been clearly identified, and how doxorubicin treatment affects the biomolecular contents of normal human hepatocytes has rarely been studied. Synchrotron radiation-based Fourier transform infrared (SR-FTIR) microspectroscopy is a state-of-the-art analytical technique for characterizing the biomolecules present in cells. In this research, the biomolecular alterations of doxorubicin-treated normal human hepatocytes compared to untreated control cells were investigated at the single-cell level by combining SR-FTIR microspectroscopy with the Cell Counting Kit-8 (CCK-8) assay and flow cytometry. WRL68 human normal embryonic liver cells, which have been shown to be very promising for assessing the cytotoxicity of toxic compounds and investigating hepato-toxicology, were used in this research. Principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA) were used to further analyse the biomolecular contents of WRL68 cells. The order of lipid acyl chains and protein α-helix structures in doxorubicin-treated WRL68 cells was found to be distinctly changed, while the nucleic acids were altered relatively less. No alteration in the carbohydrate content was distinguishable after doxorubicin treatment. These results provide more comprehensive information about the biomolecular changes in hepatocytes induced by doxorubicin treatment and help to elucidate the mechanism of doxorubicin-induced hepatotoxicity. This research also proves that SR-FTIR microspectroscopy, combined with PCA and OPLS-DA, is a promising approach for investigating drug-cell interaction systems.

Synchrotron Radiation FTIR Microspectroscopy Study of Biomolecular Alterations in Vincristine-Treated WRL68 Cells at the Single-Cell Level.

The toxic effect of vincristine on hepatocytes has rarely been studied. Synchrotron radiation-based Fourier transform infrared (SR-FTIR) microspectroscopy is a novel technique for investigating drug-cell interaction systems. In this research, the biomolecular alterations in WRL68 cells induced by vincristine treatment were investigated by SR-FTIR microspectroscopy and were further analyzed by multivariate statistical analysis and semiquantitative methods, including principal component analysis (PCA), orthogonal partial least square-discriminant analysis (OPLS-DA), and the peak area ratios of several characteristic IR bands. In vincristine-treated WRL68 cells, alterations in lipid structures and the presence of more long-chain fatty acids were found. A decrease in protein α-helical content relative to ß-sheet structures in vincristine-treated WRL68 cells was identified. The nucleic acid content was decreased relative to that of lipids and proteins in WRL68 cells treated with vincristine. These results provide important information about the toxic effect of vincristine on normal liver cells. This research also provides a new approach to reveal the biomolecular alterations in drug-treated hepatocytes by combining SR-FTIR with multivariate statistical analysis and semiquantitative methods.

Biomolecular characterization of placental tissues in gestational diabetes mellitus using Fourier transform infrared microspectroscopy.

Gestational diabetes mellitus (GDM) is a common complication during pregnancy. It could cause severe side-effect on the mother's and newborn's heath in the short- and long-term. Prevalence has been increasing over time, likely due to increases in mean maternal age and body weight. However, how GDM affects the placenta structure and function are still unclear. Fourier transform infrared microspectroscopy is well suited to study biological samples, such as tissues and cells. Biomolecules of human tissues have characteristic absorptions in mid-infrared range. In this study, Fourier transform infrared microspectroscopy was used to measure unfixed placental tissue sections from women with GDM and matched controls. The molecular composition of different type of placental tissue sections were further analyzed with principle component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA). The major spectral characteristic of biomolecules in GDM placental tissue and control group were compared. The conformational change of lipid chains and higher level of lipid oxidation were found for placental tissues from GDM pregnancies. The increase of proteins ß-sheet structures relative to the α-helix structures in the GDM placental tissues were also found. The fingerprint region showed the variances of carbohydrates, nucleic acids and phospholipids between GDM and control group placental tissues. These findings are helpful for understanding how GDM affects placenta's biochemical composition and how GDM causes maternal and fetal metabolism changes. This study also provides a new approach to investigating biomolecular composition of samples from GDM pregnancy through spectroscopic method.

Using FTIR Imaging to Investigate Silk Fibroin-Based Materials.

The secondary structures of silk fibroin (SF) are critical in the determination of the mechanical properties of the animal silks. Different characterization techniques, such as X-ray diffraction, nuclear magnetic resonance, Raman spectroscopy, and Fourier transform infrared (FTIR) technique, have been applied to study the secondary structure of animal silks. Among these techniques, FTIR is most widely used as it is sensitive to all secondary structures of proteins. Especially with the development of FTIR imaging, it is now possible to image the secondary structures of proteins at the micrometer scale, so as to understand the spatial distribution of proteins and the interaction of proteins with other materials at specific locations of interest. In this chapter, we present the methods and protocols of FTIR imaging to silk protein-based materials. We primarily introduce how to set up the instruments and accessories, as well as how to choose the appropriate imaging methods and sample preparation methods according to sample morphologies. The critical protocols for data analysis are also introduced in the last section.

Synchrotron Radiation-Based FTIR Microspectroscopic Imaging of Traumatically Injured Mouse Brain Tissue Slices.

Traumatic brain injury (TBI) is a health problem of global concern because of its serious adverse effects on public health and social economy. A technique that can be used to precisely detect TBI is highly demanded. Here, we report on a synchrotron radiation-based Fourier transform infrared (SR-FTIR) microspectroscopic imaging technique that can be exploited to identify TBI-induced injury by examining model mouse brain tissue slices. The samples were first examined by conventional histopathological techniques including hematoxylin and eosin (H&E) staining and 2,3,5-triphenyltetrazolium chloride staining and then spectroscopically imaged by SR-FTIR. SR-FTIR results show that the contents of protein and nucleic acid in the injured region are lower than their counterparts in the normal region. The injured and normal regions can be unambiguously distinguished from each other by the principle component analysis of the SR-FTIR spectral data corresponding to protein or nucleic acid. The images built from the spectral data of protein or nucleic acid clearly present the injured region of the brain tissue, which is in good agreement with the H&E staining image and optical image of the sample. Given the label-free and fingerprint features, the demonstrated method suggests potential application of SR-FTIR spectroscopic mapping for the digital and intelligent diagnosis of TBI by providing spatial and chemical information of the sample simultaneously.

Peptide diffusion and self-assembly in ambient water nanofilm on mica surface.

Ambient water nanofilms confined on solid surfaces usually show properties not seen in bulk and play unique roles in many important processes. Here we report diffusion and self-assembly of peptides in ambient water nanofilms on mica, based on "drying microcontact printing" and ex situ atomic force microscopy imaging. We found that diffusion and self-assembly of several peptides in the water nanofilms on mica resulted in one-dimensional "epitaxial" nanofilaments. The peptide self-assembly process is sensitive to the amount of water on the surface, and different peptides with varied molecular structures show different humidity-dependent behaviors. In addition, some peptides that cannot form nanofilaments on substrates in bulk water can be successfully self-assembled into nanofilaments in the water nanofilm.

Understanding Secondary Structures of Silk Materials via Micro- and Nano-Infrared Spectroscopies.

The secondary structures (also termed conformations) of silk fibroin (SF) in animal silk fibers and regenerated SF materials are critical in determining mechanical performance and function of the materials. In order to understand the structure-mechanics-function relationships of silk materials, a variety of advanced infrared spectroscopic techniques, such as micro-infrared spectroscopies (micro-IR spectroscopies for short), synchrotron micro-IR spectroscopy, and nano-infrared spectroscopies (nano-IR spectroscopies for short), have been used to determine the conformations of SF in silk materials. These IR spectroscopic methods provide a useful toolkit to understand conformations and conformational transitions of SF in various silk materials with spatial resolution from the nano-scale to the micro-scale. In this Review, we first summarize progress in understanding the structure and structure-mechanics relationships of silk materials. We then discuss the state-of-the-art micro- and nano-IR spectroscopic techniques used for silk materials characterization. We also provide a systematic discussion of the strategies to collect high-quality spectra and the methods to analyze these spectra. Finally, we demonstrate the challenges and directions for future exploration of silk-based materials with IR spectroscopies.

Tensan Silk-Inspired Hierarchical Fibers for Smart Textile Applications.

Tensan silk, a natural fiber produced by the Japanese oak silk moth ( Antherea yamamai, abbreviated to A. yamamai), features superior characteristics, such as compressive elasticity and chemical resistance, when compared to the more common silk produced from the domesticated silkworm, Bombyx mori ( B. mori). In this study, the "structure-property" relationships within A. yamamai silk are disclosed from the different structural hierarchies, confirming the outstanding toughness as dominated by the distinct mesoscale fibrillar architectures. Inspired by this hierarchical construction, we fabricated A. yamamai silk-like regenerated B. mori silk fibers (RBSFs) with mechanical properties (extensibility and modulus) comparable to natural A. yamamai silk. These RBSFs were further functionalized to form conductive RBSFs that were sensitive to force and temperature stimuli for applications in smart textiles. This study provides a blueprint in exploiting rational designs from A. yamanmai, which is rare and expensive in comparison to the common and cost-effective B. mori silk to empower enhanced material properties.

Precise correlation of macroscopic mechanical properties and microscopic structures of animal silks-using Antheraea pernyi silkworm silk as an example.

Animal silks, as one type of high performance natural material, display a unique combination of modulus, tensile strength, and extensibility that gives rise to a greater toughness than any other natural or synthetic fibers. Many previous researchers have already suggested that such excellent comprehensive mechanical properties should be closely related to their special molecular structures. In this paper, we provide more direct evidence to such an assumption by using Antheraea pernyi silkworm silk (tussah silk) as an example with synchrotron radiation FTIR microspectroscopy as a major characterization tool. Being a silkworm silk, A. pernyi silk has the same function as other silkworm silks (like common Bombyx mori silk), but on the other hand, its amino acid residue sequence is similar to that of spider dragline silk. Thus, A. pernyi silk can be a bridge between silkworm silk and spider silk that is worth investigating. Hence, in this research we designed different forcibly reeled A. pernyi silk samples by controlling the reeling rate, and subsequently tested their mechanical properties and then correlated them with their molecular structures and orientation degrees. Results show that the Young's modulus and breaking stress of forcibly reeled A. pernyi silks increased with the reeling rate, whereas the breaking strain was reduced. In the meantime, structure characterization revealed that the ß-sheet content and molecular chain orientation in A. pernyi silk all increased significantly with an increase in reeling rate. In addition, the mechanical performance of A. pernyi silk can be altered from close to that of spider dragline silk to that of B. mori silkworm silk, with just a change of the reeling rate. All these phenomena clearly indicate that structural changes in A. pernyi silks contrived and controlled by reeling rate have a great effect upon their final mechanical properties. These observations further confirm that the mechanical properties of animal silks are able to be tuned by structure control during harvest time. Furthermore, the results obtained in this study may provide useful guidance when designing and producing high performance regenerated silk fibers for different applications.

Insights into Silk Formation Process: Correlation of Mechanical Properties and Structural Evolution during Artificial Spinning of Silk Fibers.

The extraordinary comprehensive mechanical properties of animal silk (especially spider and silkworm silk) have led to extensive research on the underlying mechanisms involved. Herein, we selected various regenerated silk fibroin (RSF) fibers by choosing different postdraw conditions in a wet-spinning process developed in this laboratory to study their structure-property relationship. We use synchrotron radiation infrared and X-ray diffraction techniques to monitor the structural differences in these RSF fibers and correlate them with their mechanical properties. The results show that with the increase of post draw-down ratio, the ß-sheet content, crystallinity, and molecular orientation in these RSF fibers increase while the crystalline size decreases. The relationship between structural changes and the draw-down ratio reflects the corresponding variation in mechanical properties, namely, an increase in breaking stress with a decline in breaking strain in relation to increases in draw-down ratio. Therefore, these results provide solid and direct evidence on the evolution of structure during the artificial spinning process and on how structure determines the final mechanical performance of silk fibers. We believe this study provides a good background on the relationship between microscopic structure and macroscopic properties in polymer science and may prove useful in the production of high performance materials, not only for silk fibers but also for other natural and synthetic polymeric materials.

Tough protein-carbon nanotube hybrid fibers comparable to natural spider silks.

Animal silks, especially spider dragline silks, have an excellent portfolio of mechanical properties, but it is still a challenge to obtain artificial silk fibers with similar properties to the natural ones. In this paper, we show how to extrude tough regenerated silk fibers by adding a small amount of commercially available functionalized multiwalled carbon nanotubes (less than 1%) through an environmentally friendly wet-spinning process reported by this laboratory previously. Most of the resulting regenerated silk fibers exhibited a breaking energy beyond 130 MJ m-3, which is comparable to spider dragline silks (∼160 MJ m-3). The best of these fibers in terms of performance show a breaking stress of 0.42 GPa, breaking strain of 59%, and breaking energy of 186 MJ m-3. In addition, we used several advanced characterization techniques, such as synchrotron radiation FTIR microspectroscopy and synchrotron radiation X-ray diffraction, to reveal the toughening mechanism in such a protein-inorganic hybrid system. We believe our attempt to produce such tough protein-based hybrid fibers by using cheap, abundant and sustainable regenerated silkworm protein and commercially available functionalized carbon nanotubes, with simplified industrial wet-spinning apparatus, may open up a practical way for the industrial production of super-tough fiber materials.

A convenient and adjustable surface-modified complex containing poly-L-glutamic acid conjugates as a vector for gene delivery.

In order to quantify the amount of ligands or poly(ethylene glycol) (PEG) on each vector, here we developed a system in which poly-L-glutamic acid (PLG) was used as surface modification loading backbone, to which one PEG (MW 5000, 10000, 20000) or epidermal growth factor (EGF) was linked. The PLG conjugates can electro-statically adsorb upon DNA/ polycation complex with positive charge, and, the amount of EGF or PEG on the surface of complexes could be varied. We have made a series of complexes containing the various PLG conjugates and examined their physicochemical properties, and made a comparison of properties and transfection efficiency between these complexes. EGF- and PEG-modified complexes showed 10-25-folds higher cell transfection efficiency than unmodified complexes in medium with or without serum.