Mechanical Force for Fabricating Nanofiber

Nanofiber has attracted increasing attention owing to its wide applications such as filtration, drug delivery, wound dressing, separator, etc. A lot of fabrication methods are developed in the last few decades, electrospinning method is the most frequently utilized method for producing nanofiber. However, electrospinning features a use of electrical field to produce nanofiber, which have obviously high production cost and a big burden on the environment. And several limitations are observed such as orientation of fibers and limited options of polymer and solvents, so many researchers try to develop more facile and more effective method for making nanofiber. In this chapter, recent developed fabrication methods, handspinning, direct writing, touch and brush spinning, are discussed and the advantages of each methods are described, respectively. They utilize a simple mechanical force instead of electrical force, which delivers great benefits to producing nanofiber such as orientation of fibers along with the force direction, reduction of every cost, availability of various options for selecting polymer and solvents, and a facility to design a pattern with high precision. Those innovative and novel methods will enable us to make functional nanofibers more effective than traditional methods; consequently, they will broaden the application of nanofibers

Handspinning Enabled Highly Concentrated Carbon Nanotubes with Controlled Orientation in Nanofibers

The novel method, handspinning (HS), was invented by mimicking commonly observed methods in our daily lives. The use of HS allows us to fabricate carbon nanotube-reinforced nanofibers (CNT-reinforced nanofibers) by addressing three significant challenges: (i) the difficulty of forming nanofibers at high concentrations of CNTs, (ii) aggregation of the CNTs, and (iii) control of the orientation of the CNTs. The handspun nanofibers showed better physical properties than fibers fabricated by conventional methods, such as electrospinning. Handspun nanofibers retain a larger amount of CNTs than electrospun nanofibers, and the CNTs are easily aligned uniaxially. We attributed these improvements provided by the HS process to simple mechanical stretching force, which allows for orienting the nanofillers along with the force direction without agglomeration, leading to increased contact area between the CNTs and the polymer matrix, thereby providing enhanced interactions. HS is a simple and straightforward method as it does not require an electric field, and, hence, any kinds of polymers and solvents can be applicable. Furthermore, it is feasible to retain a large amount of various nanofillers in the fibers to enhance their physical and chemical properties. Therefore, HS provides an effective pathway to create new types of reinforced nanofibers with outstanding properties.ArticleSCIENTIFIC REPORTS. 6:37590 (2016)journal articl

De Novo Design and Synthesis of Ultra-Short Peptidomimetic Antibiotics Having Dual Antimicrobial and Anti-Inflammatory Activities

Ravichandran N. Murugan, Mija Ahn, Eunha Hwang, Ji-Hyung Seo, Chaejoon Cheong, Jeong Kyu Bang, Division of Magnetic Resonance, Korea Basic Science Institute, Ochang, Chung-Buk, Republic of KoreaBinu Jacob, Song Yub Shin, Department of Bio-Materials, Graduate School and Department of Cellular and Molecular Medicine, School of Medicine, Chosun University, Gwangju, Republic of KoreaHoik Sohn, Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas, United States of AmericaHyo-Nam Park, Jae-Kyung Hyun, Division of Electron Microscopic Research, Korea Basic Science Institute, Daejeon, Republic of KoreaEunjung Lee, Ki-Woong Jeong, Yangmee Kim, Department of Bioscience and Biotechnology, Institute of SMART Biotechnology, Konkuk University, Seoul, Republic of KoreaKy-Youb Nam, Bioinformatics and Molecular Design Research Center, Yonsei University Research Complex, Seoul, Republic of KoreaBackground: Much attention has been focused on the design and synthesis of potent, cationic antimicrobial peptides (AMPs) that possess both antimicrobial and anti-inflammatory activities. However, their development into therapeutic agents has been limited mainly due to their large size (12 to 50 residues in length) and poor protease stability.-- Methodology/Principal Findings: In an attempt to overcome the issues described above, a set of ultra-short, His-derived antimicrobial peptides (HDAMPs) has been developed for the first time. Through systematic tuning of pendant hydrophobic alkyl tails at the N(π)- and N(τ)-positions on His, and the positive charge of Arg, much higher prokaryotic selectivity was achieved, compared to human AMP LL-37. Additionally, the most potent HDAMPs showed promising dual antimicrobial and anti-inflammatory activities, as well as anti–methicillin-resistant Staphylococcus aureus (MRSA) activity and proteolytic resistance. Our results from transmission electron microscopy, membrane depolarization, confocal laser-scanning microscopy, and calcein-dye leakage experiments propose that HDAMP-1 kills microbial cells via dissipation of the membrane potential by forming pore/ion channels on bacterial cell membranes. -- Conclusion/Significance: The combination of the ultra-short size, high-prokaryotic selectivity, potent anti-MRSA activity, anti-inflammatory activity, and proteolytic resistance of the designed HDAMP-1, -3, -5, and -6 makes these molecules promising candidates for future antimicrobial therapeutics.This work was supported in part by the Korea Basic Science Institute's research program grants T33418 (J.K.B) and T33518 (J-k.H.), and the Korea Research Foundation, funded by the Korean Government (KRF-2011-0009039 to S.Y.S.). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.ChemistryBiochemistryEmail: [email protected] (JKB)Email: [email protected] (SYS

Effective Formation of Well-Defined Polymeric Microfibers and Nanofibers with Exceptional Uniformity by Simple Mechanical Needle Spinning

The fabrication of nanofibers with a mechanical force has attracted increasing attention owing to its facile and easy fabrication. Herein, we demonstrate a novel and facile fabrication technique with the mechanical force, needle spinning, which utilizes a needle tip to draw a polymer solution to form fibrous structures. We studied the effect of the processing parameters to the nanofiber structure, namely, the pulling away speed, pulling away distances, needle size, and polymer concentration, which were systemically controlled. As the needle spinning provides an effective route to adjust those parameters, highly uniform nanofibers can be achieved. There are clear tendencies in the diameter; it was increased as the polymer concentration and needle size were increased, and was decreased as the pulling away distance and pulling away speed were increased. Needle spinning with a precise control of the processing parameter enables us to readily fabricate well-defined nanofibers, with controlled dimensions in diameter and length; plus, single nanofibers also can be easily formed. Those features cannot be realized in common spinning process such as electrospinning. Therefore, this technique will lead to further development of the use of mechanical force for nanofiber fabrication and will expand the range of nanofibers applications

Recent Advances on Nanofiber Fabrications: Unconventional State-of-the-Art Spinning Techniques

In this review, we describe recent relevant advances in the fabrication of polymeric nanofibers to address challenges in conventional approaches such as electrospinning, namely low throughput and productivity with low size uniformity, assembly with a regulated structure and even architecture, and location with desired alignments and orientations. The efforts discussed have mainly been devoted to realize novel apparatus designed to resolve individual issues that have arisen, i.e., eliminating ejection tips of spinnerets in a simple electrospinning system by effective control of an applied electric field and by using mechanical force, introducing a uniquely designed spinning apparatus including a solution ejection system and a collection system, and employing particular processes using a ferroelectric material and reactive precursors for atomic layer deposition. The impact of these advances to ultimately attain a fabrication technique to solve all the issues simultaneously is highlighted with regard to manufacturing high-quality nanofibers with high- throughput and eventually, practically implementing the nanofibers in cutting-edge applications on an industrial scale

Coloration and Chromatic Sensing Behavior of Electrospun Cellulose Fibers with Curcumin

The effective approach for coloration and chromatic sensing of electrospun cellulose fabrics with a natural colorant, curcumin, is demonstrated. To achieve high surface area, the morphology of fiber was controlled to have rough and porous surface through an electrospinning of a cellulose acetate (CA) solution under optimized electrospinning parameters and solvent system. The resulting CA fibers were treated with a curcumin dye/NaOH ethanol solution, in which deacetylation of the CA fiber and high-quality coloration with curcumin were simultaneously achieved. As a control, a cotton fiber with similar diameter and smooth surface morphology was treated by the same method, resulting in poor coloration quality. The difference can be attributed to high surface area as well as trapping of dye molecules inside of cellulose fiber during deacetylation. Both fibers were further utilized for a chromatic sensing application for specific toxic gases. The incorporated curcumin dye responded to hydrogen chloride and ammonia gases reversibly via keto-enol tautomerism, and, as a consequence, the color was reversibly changed between reddish-brown and yellow colors. The cellulose fiber fabricated by the electrospinning showed ten times higher and two times quicker responsiveness compared to curcumin-colored cotton fiber sample prepared with the same immersion method

Coloration and Chromatic Sensing Behavior of Electrospun Cellulose Fibers with Curcumin

The effective approach for coloration and chromatic sensing of electrospun cellulose fabrics with a natural colorant, curcumin, is demonstrated. To achieve high surface area, the morphology of fiber was controlled to have rough and porous surface through an electrospinning of a cellulose acetate (CA) solution under optimized electrospinning parameters and solvent system. The resulting CA fibers were treated with a curcumin dye/NaOH ethanol solution, in which deacetylation of the CA fiber and high-quality coloration with curcumin were simultaneously achieved. As a control, a cotton fiber with similar diameter and smooth surface morphology was treated by the same method, resulting in poor coloration quality. The difference can be attributed to high surface area as well as trapping of dye molecules inside of cellulose fiber during deacetylation. Both fibers were further utilized for a chromatic sensing application for specific toxic gases. The incorporated curcumin dye responded to hydrogen chloride and ammonia gases reversibly via keto-enol tautomerism, and, as a consequence, the color was reversibly changed between reddish-brown and yellow colors. The cellulose fiber fabricated by the electrospinning showed ten times higher and two times quicker responsiveness compared to curcumin-colored cotton fiber sample prepared with the same immersion method

X-ray-Based Spectroscopic Techniques for Characterization of Polymer Nanocomposite Materials at a Molecular Level

This review provides detailed fundamental principles of X-ray-based characterization methods, i.e., X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, and near-edge X-ray absorption fine structure, and the development of different techniques based on the principles to gain deeper understandings of chemical structures in polymeric materials. Qualitative and quantitative analyses enable obtaining chemical compositions including the relative and absolute concentrations of specific elements and chemical bonds near the surface of or deep inside the material of interest. More importantly, these techniques help us to access the interface of a polymer and a solid material at a molecular level in a polymer nanocomposite. The collective interpretation of all this information leads us to a better understanding of why specific material properties can be modulated in composite geometry. Finally, we will highlight the impacts of the use of these spectroscopic methods in recent advances in polymer nanocomposite materials for various nano- and bio-applications