Cellulose fibrils with widths in the nanometer range are nature-based materials with unique and potentially useful features. Most importantly, these novel nanocelluloses open up the strongly expanding fields of sustainable materials and nanocomposites, as well as medical and life-science devices, to the natural polymer cellulose. The nanodimensions of the structural elements result in a high surface area and hence the powerful interaction of these celluloses with surrounding species, such as water, organic and polymeric compounds, nanoparticles, and living cells. This Review assembles the current knowledge on the isolation of microfibrillated cellulose from wood and its application in nanocomposites; the preparation of nanocrystalline cellulose and its use as a reinforcing agent; and the biofabrication of bacterial nanocellulose, as well as its evaluation as a biomaterial for medical implants.

Nanocelluloses: A New Family of Nature-Based Materials

Recent achievements in the construction of surfaces with special wettabilities, such as superhydrophobicity, superhydrophilicity, superoleophobicity, superoleophilicity, superamphiphilicity, superamphiphobicity, superhydrophobicity/superoleophilicity, and reversible switching between superhydrophobicity and superhydrophilicity, are presented. Particular attention is paid to superhydrophobic surfaces created via various methods and surfaces with reversible superhydrophobicity and superhydrophilicity that are driven by various kinds of external stimuli. The control of the surface micro-/nanostructure and the chemical composition is critical for these special properties. These surfaces with controllable wettability are of great importance for both fundamental research and practical applications.

Design and Creation of Superwetting/Antiwetting Surfaces

In recent years, zwitterionic materials such as poly(carboxybetaine) (pCB) and poly(sulfobetaine) (pSB) have been applied to a broad range of biomedical and engineering materials. Due to electrostatically induced hydration, surfaces coated with zwitterionic groups are highly resistant to nonspecific protein adsorption, bacterial adhesion, and biofilm formation. Among zwitterionic materials, pCB is unique due to its abundant functional groups for the convenient immobilization of biomolecules. pCB can also be prepared in a hydrolyzable form as cationic pCB esters, which can kill bacteria or condense DNA. The hydrolysis of cationic pCB esters into nonfouling zwitterionic groups will lead to the release of killed microbes or the irreversible unpackaging of DNA. Furthermore, mixed-charge materials have been shown to be equivalent to zwitterionic materials in resisting nonspecific protein adsorption when they are uniformly mixed at the molecular scale.

Ultralow-Fouling, Functionalizable, and Hydrolyzable Zwitterionic Materials and Their Derivatives for Biological Applications

We report on the epitaxial growth of a group-IV ferromagnetic semiconductor, Mn(x)Ge(1-x), in which the Curie temperature is found to increase linearly with manganese (Mn) concentration from 25 to 116 kelvin. The p-type semiconducting character and hole-mediated exchange permit control of ferromagnetic order through application of a +/-0.5-volt gate voltage, a value compatible with present microelectronic technology. Total-energy calculations within density-functional theory show that the magnetically ordered phase arises from a long-range ferromagnetic interaction that dominates a short-range antiferromagnetic interaction. Calculated spin interactions and percolation theory predict transition temperatures larger than measured, consistent with the observed suppression of magnetically active Mn atoms and hole concentration.

http://science.sciencemag.org/content/sci/295/5555/651.full.pdf

A Group-IV Ferromagnetic Semiconductor: MnxGe1−x

Each individual is provided with a unique gut microbiota profile that plays many specific functions in host nutrient metabolism, maintenance of structural integrity of the gut mucosal barrier, immunomodulation, and protection against pathogens. Gut microbiota are composed of different bacteria species taxonomically classified by genus, family, order, and phyla. Each human’s gut microbiota are shaped in early life as their composition depends on infant transitions (birth gestational date, type of delivery, methods of milk feeding, weaning period) and external factors such as antibiotic use. These personal and healthy core native microbiota remain relatively stable in adulthood but differ between individuals due to enterotypes, body mass index (BMI) level, exercise frequency, lifestyle, and cultural and dietary habits. Accordingly, there is not a unique optimal gut microbiota composition since it is different for each individual. However, a healthy host–microorganism balance must be respected in order to optimally perform metabolic and immune functions and prevent disease development. This review will provide an overview of the studies that focus on gut microbiota balances in the same individual and between individuals and highlight the close mutualistic relationship between gut microbiota variations and diseases. Indeed, dysbiosis of gut microbiota is associated not only with intestinal disorders but also with numerous extra-intestinal diseases such as metabolic and neurological disorders. Understanding the cause or consequence of these gut microbiota balances in health and disease and how to maintain or restore a healthy gut microbiota composition should be useful in developing promising therapeutic interventions.

https://www.mdpi.com/2076-2607/7/1/14/pdf/1

What is the Healthy Gut Microbiota Composition? A Changing Ecosystem across Age, Environment, Diet, and Diseases

The absorption process of bisphenol A (BPA) in a number of poly(acrylate) thin films, such as poly(2-methoxyethyl acrylate) (PMEA), poly(ethyl acrylate) (PEA), poly(n-butyl methacrylate) (PBMA), and poly(methyl methacrylate) (PMMA), has been investigated by quartz crystal microbalance (QCM) and infrared reflection absorption spectroscopy (IRRAS) measurements. Both QCM and IRRAS measurements show that the BPA molecules absorb in PMEA, PEA, and PBMA thin films but not in PMMA thin film. The differences in the BPA absorption behavior are mainly attributed to the difference in the glass transition temperature (Tg) between these polymers. This absorption behavior also depends on the BPA concentration and polymer film thickness. Furthermore, IRRAS characterization demonstrates that the hydrogen bonding is formed between the hydroxyl group in BPA and the carbonyl group in the poly(acrylate) thin films. BPA molecule absorbed in these polymer thin films can be removed by ethanol rinse treatment. By optimizing expe...

Quartz crystal microbalance and infrared reflection absorption spectroscopy characterization of bisphenol A absorption in the poly(acrylate) thin films

Sourdough, a traditional fermented dough, is made via natural fermentation by lactic acid bacteria (LAB). Its pH changes from near neutral to acid during the subculture process. However, the product quality of subcultured sourdough depends on the unpredictable succession of LAB communities, the influential factors of which are still unclear. To elucidate one end of the LAB community succession mechanism, we evaluated the effect of pH by designing four subculture experiments using a model medium adjusted to pH 6.7, 5.5, and 4.5, as well as a natural sourdough subculture. All experiments began by inoculating a sourdough LAB mixture, and both bacterial successions and fermentative properties were monitored until ten subculture steps. In media subcultures, lactic acid production was higher in higher pH media. Three LAB genera, Weissella, Pediococcus, and Lactobacillus, each represented by one operational taxonomic unit (OTU), were successively detected in all subcultures. In later steps with lower pH media, an OTU closely related to Lactobacillus brevis dominated, replacing an OTU closely related to the Weissella cibaria-confusa group that was more dominant than the L. brevis OTU in the near-neutral pH medium. In the sourdough subculture, the three genera were also detected, while Lactobacillus was dominant in earlier steps due to the emergence of an OTU closely related to Lactobacillus sanfranciscensis. These results suggest that a lower pH is favorable for the sequence of sourdough bacterial community evolution finalizing with Lactobacillus domination. Further research is needed to elucidate additional factors other than pH that influence the pattern of LAB community shift.

Impact of pH on succession of sourdough lactic acid bacteria communities and their fermentation properties.

Chiral crystal formation of octadecylcytosine monolayer by complementary base paring

We have previously reported the hydration structure of a poly(2-methoxyethyl acrylate) (PMEA) antithrombogenic material. In the present study, the hydration structure of a 2-methoxyethyl acetate (MEAc) model monomer for PMEA was explored by means of attenuated total reflection infrared (ATR-IR) spectroscopy and differential scanning calorimetry (DSC). Water in MEAc does not show an evidence for cold crystallization by DSC, while it was found by ATR-IR spectroscopy that MEAc has a hydration structure similar to that of PMEA at a functional group level. Three different types of hydrated water, tightly bound water, loosely bound water and scarcely bound water, were identified in MEAc, as well as PMEA. It was suggested from the present study that the localized and concentrated water cluster having the three types of hydration structure on the surface of PMEA plays an important role in the biocompatibility.

Hydration Structure of Poly(2-methoxyethyl acrylate): Comparison with a 2-Methoxyethyl Acetate Model Monomer

The chain dynamics of well-defined poly(2-methoxyethyl acrylate) (PMEA), which has been used in practice as a bioinert coating for heart-lung machines, was examined as a function of water content by dielectric relaxation spectroscopy (DRS). Two relaxation processes observed in both dried and hydrated films were assigned to the segmental motion (α-process) and the relatively smaller scale motion such as the hindered rotation of side chains (β-process). Water molecules adsorbed on PMEA made the α-process faster, meaning that water molecules in PMEA played the role of a plasticizer. Combining the above knowledge with the depth dependence of water content in the PMEA film previously obtained by neutron reflectivity, the segmental dynamics of PMEA at the water interface, which should be crucial to bio-inertness, is discussed. We found that the segmental motion was markedly faster than that in the bulk and almost comparable to the side chain motion.

Masaru Tanaka

Papers

Quartz crystal microbalance and infrared reflection absorption spectroscopy characterization of bisphenol A absorption in the poly(acrylate) thin films

Impact of pH on succession of sourdough lactic acid bacteria communities and their fermentation properties.

Chiral crystal formation of octadecylcytosine monolayer by complementary base paring

Hydration Structure of Poly(2-methoxyethyl acrylate): Comparison with a 2-Methoxyethyl Acetate Model Monomer

Dynamics of a bioinert polymer in hydrated states by dielectric relaxation spectroscopy