Preparation and applications of functional nanofibers based on the combination of electrospinning, controlled radical polymerization and 'Click Chemistry'

BaTiO3 nanoparticle-decorated hierarchical Ni nanowire assemblies for magnetoelectric applications

One dimensional multiferroic systems with spin-charge coupling at room temperature are highly useful in future multifunctional devices.

Magnetic field-directed hybrid anisotropic nanocomposites

A facile bottom-up approach is developed to grow magnetic metallic Cu/FeCo (core/shell) nanowires, where their distribution and orientation can be controlled by magnetic field. The nanocomposites consisting of a ferroelectric polymer matrix and magnetic nanowire arrays exhibit the orientation-controlled anisotropy and interfacial magnetoelectric coupling effect.

A smart core-sheath nanofiber that captures and releases red blood cells from the blood

A smart core-sheath nanofiber for non-adherent cell capture and release is demonstrated. The nanofibers are fabricated by single-spinneret electrospinning of poly(N-isopropylacrylamide) (PNIPAAm), polycaprolactone (PCL) and nattokinase (NK) solution blends. The self-assembly of PNIPAAm and PCL blends during the electrospinning generates the core-sheath PCL/PNIPAAm nanofibers with PNIPAAm as the sheath. The PNIPAAm-based core-sheath nanofibers are switchable between hydrophobicity and hydrophilicity with temperature change and enhance stability in the blood. When the nanofibers come in contact with blood, the NK is released from the nanofibers to resist platelet adhesion on the nanofiber surface, facilitating the direct capture and isolation of red blood cells (RBCs) from the blood above phase-transition temperature of PNIPAAm. Meanwhile, the captured RBCs are readily released from the nanofibers with temperature stimuli in an undamaged manner. The release efficiency of up to 100% is obtained while maintaining cellular integrity and function. This work presents promising nanofibers to effectively capture non-adherent cells and release for subsequent molecular analysis and diagnosis of single cells.

Synthesis of dense arrays of multiferroic CoFe2O4–PbZr0.52Ti0.48O3 core/shell nanocables

A major challenge in the development of efficient magnetoelectric nanocomposites is the adequate control of the interfaces, in order to avoid the formation of undesirable interphases and to ensure an optimal strain mediated coupling.

Surface modification of electrospun cellulose acetate nanofibers via RAFT polymerization for DNA adsorption

We report on a facile and robust method by which surface of electrospun cellulose acetate (CA) nanofibers can be chemically modified with cationic polymer brushes for DNA adsorption. The surface of CA nanofibers was functionalized by growing poly[(ar-vinylbenzyl)trimethylammonium chloride)] [poly(VBTAC)] brushes through a multi-step chemical sequence that ensures retention of mechanically robust nanofibers. Initially, the surface of the CA nanofibers was modified with RAFT chain transfer agent. Poly(VBTAC) brushes were then prepared via RAFT-mediated polymerization from the nanofiber surface. DNA adsorption capacity of CA nanofibrous web surface functionalized with cationic poly(VBTAC) brushes was demonstrated. The reusability of these webs was investigated by measuring the adsorption capacity for target DNA in a cyclic manner. In brief, CA nanofibers surface-modified with cationic polymer brushes can be suitable as membrane materials for filtration, purification, and/or separation processes for DNA.

Electrospun azido-PCL nanofibers for enhanced surface functionalization by click chemistry

This paper reports highly surface functionalized and "clickable" α,ω-azido-poly(ε-caprolactone) fibers (f-PCL-N(3)), obtained by classical electrospinning setup. Azide-functionalized PCL was obtained from a commercially available α,ω-poly(ε-caprolactone)-diol, PCL(2), and electrospun with a nonderivative high-molecular-weight PCL. Successful chemical modifications of PCL(2) were confirmed by NMR, FTIR and MALDI-TOF mass spectroscopy. The high content of surface azides, as a response to the high electric field applied, was characterized using a colorimetric assay. In addition, azide reduction to amines revealed a nondestructive route for highly amine-functionalized fibers. Fluorescence labeling of f-PCL-N(3) fibers with FITC-alkyne fluorophore proved that the azide groups are mainly surface-localized as well as highly available for click-chemistry coupling.

Electrospinning of nanofibers from non-polymeric systems: polymer-free nanofibers from cyclodextrin derivatives

High molecular weight polymers and high polymer concentrations are desirable for the electrospinning of nanofibers since polymer chain entanglements and overlapping are important for uniform fiber formation. Hence, the electrospinning of nanofibers from non-polymeric systems such as cyclodextrins (CDs) is quite a challenge since CDs are cyclic oligosaccharides. Nevertheless, in this study, we have successfully achieved the electrospinning of nanofibers from chemically modified CDs without using a carrier polymer matrix. Polymer-free nanofibers were electrospun from three different CD derivatives, hydroxypropyl-β-cyclodextrin (HPβCD), hydroxypropyl-γ-cyclodextrin (HPγCD) and methyl-β-cyclodextrin (MβCD) in three different solvent systems, water, dimethylformamide (DMF) and dimethylacetamide (DMAc). We observed that the electrospinning of these CDs is quite similar to polymeric systems in which the solvent type, the solution concentration and the solution conductivity are some of the key factors for obtaining uniform nanofibers. Dynamic light scattering (DLS) measurements indicated that the presence of considerable CD aggregates and the very high solution viscosity were playing a key role for attaining nanofibers from CD derivatives without the use of any polymeric carrier. The electrospinning of CD solutions containing urea yielded no fibers but only beads or splashes since urea caused a notable destruction of the self-associated CD aggregates in their concentrated solutions. The structural, thermal and mechanical characteristics of the CD nanofibers were also investigated. Although the CD derivatives are amorphous small molecules, interestingly, we observed that these electrospun CD nanofibers/nanowebs have shown some mechanical integrity by which they can be easily handled and folded as a free standing material.

High resolution quantitative piezoresponse force microscopy of BiFeO3 nanofibers with dramatically enhanced sensitivity

Piezoresponse force microscopy (PFM) has emerged as the tool of choice for characterizing piezoelectricity and ferroelectricity of low-dimensional nanostructures, yet quantitative analysis of such low-dimensional ferroelectrics is extremely challenging. In this communication, we report a dual frequency resonance tracking technique to probe nanocrystalline BiFeO(3) nanofibers with substantially enhanced piezoresponse sensitivity, while simultaneously determining its piezoelectric coefficient quantitatively and correlating quality factor mappings with dissipative domain switching processes. This technique can be applied to probe the piezoelectricity and ferroelectricity of a wide range of low-dimensional nanostructures or materials with extremely small piezoelectric effects.

Antimicrobial fibers: therapeutic possibilities and recent advances

The emergence of multi-drug-resistant bacteria such as methicillin-resistant strains of Staphylococcus aureus (MRSA), vancomycin-resistant enterococci, Pseudomonas aeruginosa, Acinetobacter baumannii and extended-spectrum β-lactamase (carbapenemase)-producing Enterobacteriaceae is becoming a serious threat. New-generation antimicrobial agents need to be developed. This includes the design of novel antimicrobial compounds and drug-delivery systems. This review provides an introduction into different classes of antimicrobial materials. The main focus is on strategies for the introduction of antimicrobial properties in polymer materials. These can be roughly divided into surface modification, inclusion of antimicrobial compounds that can leach from the polymer, and the introduction of polymer-bound moieties that provide the polymer with antimicrobial properties. One of the main challenges in the development of antimicrobial polymers for the use in contact with human tissue is the concomitant demand of non-cytotoxicity. Current research is strongly focused on the latter aspect.

Characterisation of internal morphologies in electrospun fibers by X-ray tomographic microscopy

Electrospun fabrics for use in, for example, tissue engineering, wound dressings, textiles, filters and membranes have attracted a lot of attention due to their morphological nanoscale architectures which enhance their physical properties. A thorough detailed internal morphological study has been performed on electrospun polystyrene (PS) fibers produced from dimethylformamide (DMF) solutions. Investigations by transmission electron microscopy (TEM) and thorough studies for the first time by synchrotron based X-ray tomographic microscopy (XTM) revealed that the individual electrospun PS fibers and beads have a graded density and in some cases even an internal porous structure.

Multiferroic CoFe2O4-Pb(Zr(0.52)Ti(0.48))O3 core-shell nanofibers and their magnetoelectric coupling

Multiferroic CoFe(2)O(4)-Pb(Zr(0.52)Ti(0.48))O(3) core-shell nanofibers have been synthesized by coaxial electrospinning in combination with a sol-gel process. The core-shell configuration of nanofibers has been verified by scanning electron microscopy and transmission electron microscopy, and the spinel structure of CoFe(2)O(4) and perovskite structure of Pb(Zr(0.52)Ti(0.48))O(3) have been confirmed by X-ray diffraction and selected area electron diffraction. The multiferroic properties of core-shell nanofibers have been demonstrated by magnetic hysteresis and piezoresponse force microscopy, and their magnetoelectric coupling has been confirmed by evolution of piezoresponse under an external magnetic field, showing magnetically induced ferroelectric domain switching and changes in switching characteristics. The lateral magnetoelectric coefficient is estimated to be 2.95 × 10(4) mV/cmOe, two orders of magnitude higher than multiferroic thin films of similar composition.

Controllable fabrication of soap-bubble-like structured polyacrylic acid nano-nets via electro-netting

Soap-bubble-like structured polyacrylic acid (PAA) nano-nets that comprise interlinked ultrathin nanowires with diameters of 10-35 nm are controllably prepared by a one-step electro-netting process.