This work was supported by NSF/DOE Partnership in Plasma Science and Technology (NSF Grant No. CBET-0853777 and DOE Grant No. DE-SC0001169), STTR Phase I project (NSF STTR PHASE I No.1010133). The authors would like to thank the PPPL Offsite Research Program supported by the Office of Fusion Energy Sciences for supporting arc experiments.

1. Anode preparation
<ol>
 <li>Scale nickel powder (99.8%, 300 mesh) and yttrium powder (99.9%, 40 mesh) according to the molar radio of 4.2:1 as catalyst powder.</li>
 <li>Mix the catalyst powder with graphite powder (99.9995%, 200 mesh) very well. Fill the mixed powder into hollow graphite rod (5 mm outer diameter, 2.5 mm inner diameter and 75 mm length) firmly. Make sure the total molar radio of C:Ni:Y in anode rod is 94.8:4.2:1, which is optimum ratio to synthesize SWCNT 9.</li>
 <li>Install cathode rod (pure graphite, 13 mm diameter) and the stuffed anode rod inside cylindrical chamber (stainless steel, 152 mm diameter and 254 mm length). Adjust the gap distance between cathode and anode to about 3 mm.</li>
</ol>
2. Substrate setup
<ol>
 <li>Place a cuboid permanent magnet (25 mm &times; 25 mm &times; 100 mm) inside the chamber at about 25 mm distance from the interelectrode axis. The Ultra-High-Temp Alnico magnet used in experiment has the weight of 650 grams. Use the configuration when the interelectrode gap is placed at the distance of about h = 75 mm (Figure 1a) from the bottom of permanent magnet.</li>
 <li>Cut the 0.3 mm thickness molybdenum sheet (99.95%) as the 25 mm &times; 100 mm rectangular shape. Remove surface contamination by ultrasonic dismembrator in acetone and ethanol for 30 min with 50% sonicating amplitude, 150 w output power and 40 kHz frequency.</li>
 <li>Install molybdenum sheet attaching one side of permanent magnet, and turn this side towards electrodes.</li>
 <li>Measure the magnetic field in the interelectrode gap by a Gaussmeter. Keep the average magnetic field between the electrodes is about 0.06 T.</li>
</ol>
3. Ignition of arc plasma
<ol>
 <li>Pump down the cylindrical chamber to the pressure less than 10-1 Torr vacuum and then filled it with helium (99.995%) to 500 Torr.</li>
 <li>Connect arc electrodes to DC welding power supply and set up the power supply on arc current of about 75 A.</li>
 <li>Record the real-time values of arc current, arc voltage and chamber pressure for post-experiment analysis.</li>
 <li>Start the video of arcing from the right and front viewports by two digital cameras simultaneously. The snapshots after 1 second of arc starting are shown in Figure 1b (from right viewport) and Figure 1d (from front viewport).</li>
 <li>Run the arc for 15 seconds. Cool down chamber by natural convection for at least 20 minutes.</li>
</ol>
4. Post-synthesis analysis and characterization
<ol>
 <li>Use tweezers to tear off the deposition flake from the surface of molybdenum sheet where the arc plasmas jet was directed. Another sample is collected from the black collar of cathode. Observe the morphology of both sides of deposition flake under SEM (acceleration voltage of 30 KV was used).</li>
 <li>Regarding the sample preparation for TEM analysis, the thin films of sample were obtained by drop casting a suspension of methanol-dispersed SWCNT solution after sonicating for 60 minutes using ultrasonic dismembrator with 50% sonicating amplitude. Observe the morphology of the thin film under JEOL TEM with the voltage of 100 KV after the volatilization of methanol solution. For the position of interest in sample, electron diffraction pattern can be obtained with the CCD camera length of 50 cm associated with TEM.</li>
 <li>Raman spectroscopy was performed on a micro-Raman system based on a 200 mW Lexel 3000 Ar ion laser (tunable single line output), with holographic optics, a 0.5 m spectrometer and a liquid nitrogen cooled CCD detector; wavelength 514 nm which corresponds to the energy of 2.33 eV. Raman measurements covered the range of 100 cm-1 to 3100 cm-1, and were carried out on the surface of graphene flakes.</li>
</ol>
5. Representative Results
The video snapshots obtained simultaneously from right and front viewports of the chamber are shown in Figure 1b, d for h = 75 mm. These images illustrate significant perturbation of arc plasma column in presence of external magnetic field in comparison with axially symmetric arc column observed in the case without a magnetic field 10.
Figure 2a and 2b display the typical morphology of SWCNT and catalyst particles collected on the collar of cathode without magnetic field and with the magnetic field of B = 0.06 Tesla under TEM, respectively. It can be seen that SWCNT with magnetic field are close-packed into bundles with diameters ranging from 2 to 20 nm due to the van der Waals interaction between individual SWCNT. In comparison, the SWCNT without magnetic field have the larger diameter in bundles and larger individual diameter, which is consistent with the analysis of Raman spectrum. Also, the magnetic field can result in the SWCNT with higher purity shown in Figure 2a and 2b.
The most interesting influence of the magnetic field is that graphene flakes can be obtained from the surface of deposition flakes which is close to molybdenum sheet in the same process. Figure 2c and 2d show the SEM and TEM images of graphene flakes as well as few-layer graphene obtained from the sample taken at the location corresponded to arc plasmas jets. The inset of Figure 2d shows the electrons diffraction pattern associated with the graphene. The hexagonal dots pattern of electron diffraction presents the evidence of well-ordered crystal structures.
Raman spectrum is a powerful tool for characterization of graphene flakes and SWCNT. The typical peaks observed in graphene are the G and 2D peaks at ~1600 cm-1 and ~2700 cm-1 respectively, using the excitation wavelength of 514 nm. The G peak stems from in plane vibrations which can be observed in all sp2 carbon materials. The 2D peak is a second order of the D peak but is seen even in non disordered systems, due to the fourth order phonon momentum exchange double resonance process. It plays a crucial role in the characterization of graphene. The intensity I(2D)/I(G) is approximately 4 for monolayer graphene and decreases with the addition of subsequent layers, thus making it possible to estimate the thickness of graphene layers. 11 Figure 3 indicates that the value of I(2D) / I(G) is around 1, which can be the evidence of few-layer graphene. The radial breathing mode (RBM) between 120 and 350 cm-1 in Raman spectrum can be used to identify the nanotube diameter through the coherent vibration frequency of the C atoms in the radial direction. The experimental relation between the frequency and SWCNT diameter is &omega;RBM=A/dt+B, where the parameters of A and B equal to 234 and 10 cm-1, respectively, for the typical SWCNT formed in bundles. From Figure 3, the RBM frequencies of SWCNT without and with magnetic field are 163.8 and 215.2 cm-1, corresponding to the average individual SWCNT diameters of 1.52 and 1.14 nm, respectively.
<img alt="Figure 1." src="/files/ftp_upload/3455/3455fig1.jpg" /> 
Figure 1. Distribution of magnetic field simulated by FEMM 4.2 software (a), photograph of arc plasmas jet from the right viewport (b), schematic diagram of electrodes position and direction magnetic field in the gap for the case when the interelectrode gap is positioned about 75 mm above the bottom of permanent magnet (c), and photograph of arc plasmas jet from the front viewport (d).
<img alt="Figure 2." src="/files/ftp_upload/3455/3455fig2.jpg" /> 
Figure 2. Representative TEM image of as-synthesized SWCNT bundles without magnetic field (a) and SWCNT bundles with magnetic field (b), typical SEM image of graphene flakes synthesized with magnetic field (c), and TEM image of graphene with magnetic field. Inset is the selected area electron diffraction pattern showing the crystalline structure of graphene.
<img alt="Figure 3." src="/files/ftp_upload/3455/3455fig3.jpg" /> 
Figure 3. Raman spectrum of the samples with magnetic field in the range of 100 to 3100 cm-1. Inset: Raman spectrum of the samples without magnetic field around RBM frequencies.
<img alt="Figure 4." src="/files/ftp_upload/3455/3455fig4.jpg" /> 
Figure 4. Nanostructure growth region and number density of carbon and nickel for arc of 60 A. Note that the densities of carbon and nickel shown on left and right hand side of the electrodes, co-exist in the same region.

<ol>
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We have nothing to disclose.

In the video snapshots shown in Figure 1b and 1d, for the case that the interelectrode gap was placed at the distance of about h=75 mm from the bottom of permanent magnet, it should be noted that change of magnet position (we tested magnet shift along z-axis and turning the magnet over) results in deviation of arc jet flow in x-direction corresponding to direction of J&times;B force illustrated in Figure 1c. It was also observed that the geometry of arc plasma column did...

Table of specific reagents and equipment:
<table border="1">
 <tbody>
 <tr>
 <th>
 Name of the reagent</th>
 <th>
 Company</th>
 <th>
 Catalogue number</th>
 <th>
 Comments (optional)</th>
 </tr>
 <tr>
 <td>Methanol</td>
 <td>Acros Organics</td>
 <td>423950010</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Nickel powder</td>
 <td>Alfa Aesar</td>
 <td>10581</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Yttrium powder</td>
 <td>Acros Organics</td>
 <td>318060050</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Graphite powder</td>
 <td>Alfa Aesar</td>
 <td>40799</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Hollow graphite rod</td>
 <td>Saturn Industries</td>
 <td>POCO EDM 3</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Permanent magnet</td>
 <td>McMaster-Carr</td>
 <td>57315K51</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Molybdenum sheet</td>
 <td>Dingqi Sci. and Tech.</td>
 <td>080504-11</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Ultrasonic 
 dismembrator</td>
 <td>Fisher Scientific</td>
 <td>Model 150T</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Hall-effect gaussmeter</td>
 <td>AI</td>
 <td>Model 100</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Welding power supply</td>
 <td>Miller Electric</td>
 <td>Gold Star 600SS</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Vacuum pump</td>
 <td>J/B</td>
 <td>DV-85N</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>SEM</td>
 <td>Zeiss</td>
 <td>LEO 1430VP</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>TEM</td>
 <td>JEOL</td>
 <td>1200 EX</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Raman</td>
 <td>Horiba</td>
 <td>HR800</td>
 <td>&nbsp;</td>
 </tr>
 </tbody>
</table>

simultaneous synthesis of single-walled carbon nanotubes and graphene in a magnetically-enhanced arc plasma

Carbon nanostructures such as single-walled carbon nanotubes (SWCNT) and graphene attract a deluge of interest of scholars nowadays due to their very promising application for molecular sensors, field effect transistor and super thin and flexible electronic devices1-4. Anodic arc discharge supported by the erosion of the anode material is one of the most practical and efficient methods, which can provide specific non-equilibrium processes and a high influx of carbon material to the developing structures at relatively higher temperature, and consequently the as-synthesized products have few structural defects and better crystallinity.
 To further improve the controllability and flexibility of the synthesis of carbon nanostructures in arc discharge, magnetic fields can be applied during the synthesis process according to the strong magnetic responses of arc plasmas. It was demonstrated that the magnetically-enhanced arc discharge can increase the average length of SWCNT 5, narrow the diameter distribution of metallic catalyst particles and carbon nanotubes 6, and change the ratio of metallic and semiconducting carbon nanotubes 7, as well as lead to graphene synthesis 8. 
 Furthermore, it is worthwhile to remark that when we introduce a non-uniform magnetic field with the component normal to the current in arc, the Lorentz force along the J&times;B direction can generate the plasmas jet and make effective delivery of carbon ion particles and heat flux to samples. As a result, large-scale graphene flakes and high-purity single-walled carbon nanotubes were simultaneously generated by such new magnetically-enhanced anodic arc method. Arc imaging, scanning electron microscope (SEM), transmission electron microscope (TEM) and Raman spectroscopy were employed to analyze the characterization of carbon nanostructures. These findings indicate a wide spectrum of opportunities to manipulate with the properties of nanostructures produced in plasmas by means of controlling the arc conditions.

Watch this Scientific Journal Video about Simultaneous Synthesis of Single-walled Carbon Nanotubes and Graphene in a Magnetically-enhanced Arc Plasma at JoVE.com

Simultaneous Synthesis of Single-walled Carbon Nanotubes and Graphene in a Magnetically-enhanced Arc Plasma

Anodic arc discharge is one of the most practical and efficient methods to synthesize various carbon nanostructures. To increase the arc controllability and flexibility, a non-uniform magnetic field was introduced to process the one-step synthesis of large-scale graphene flakes and high-purity single-walled carbon nanotubes.

Carbon nanostructures such as single-walled carbon nanotubes (SWCNT) and graphene attract a deluge of interest of scholars nowadays due to their very ...

simultaneous-synthesis-single-walled-carbon-nanotubes-graphene

Research

JoVE Journal

Bioengineering

15.2K 조회수.  The George Washington University. 양극 아크 방전은 다양한 탄소 nanostructures를 합성하기위한 가장 실용적이고 효율적인 방법 중 하나입니다. 아크 controllability과 유연성을 향상시키기 위해 비 균일한 자기장은 대규모 graphene 프레 이크와 고순도 단일 벽의 탄소 나노튜브의 한 단계로 합성을 처리하기 위해 도입되었습니다.

비디오: Simultaneous Synthesis of Single-walled Carbon Nanotubes and Graphene in a Magnetically-enhanced Arc Plasma

Graphene Coatings for Biomedical Implants

Atomically smooth graphene as a surface coating has potential to improve implant properties. This demonstrates a method for coating nitinol alloys with nanometer thick layers of graphene for applications as a stent material. Graphene was grown on copper substrates via chemical vapor deposition and then transferred onto nitinol substrates. In order to understand how the graphene coating could change biological response, cell viability of rat aortic endothelial cells and rat aortic smooth muscle cells was investigated. Moreover, the effect of graphene-coatings on cell adhesion and morphology was examined with fluorescent confocal microscopy. Cells were stained for actin and nuclei, and there were noticeable differences between pristine nitinol samples compared to graphene-coated samples. Total actin expression from rat aortic smooth muscle cells was found using western blot. Protein adsorption characteristics, an indicator for potential thrombogenicity, were determined for serum albumin and fibrinogen with gel electrophoresis. Moreover, the transfer of charge from fibrinogen to substrate was deduced using Raman spectroscopy. It was found that graphene coating on nitinol substrates met the functional requirements for a stent material and improved the biological response compared to uncoated nitinol. Thus, graphene-coated nitinol is a viable candidate for a stent material.

Graphene offers potential as a coating material for biomedical implants. In this study we demonstrate a method for coating nitinol alloys with nanometer thick layers of graphene and determine how graphene may influence implant response.

Atomically smooth graphene as a surface coating has potential to improve implant properties. This demonstrates a method for coating nitinol alloys with ...

Localization and Relative Quantification of Carbon Nanotubes in Cells with Multispectral Imaging Flow Cytometry

Carbon-based nanomaterials, like carbon nanotubes (CNTs), belong to this type of nanoparticles which are very difficult to discriminate from carbon-rich cell structures and de facto there is still no quantitative method to assess their distribution at cell and tissue levels. What we propose here is an innovative method allowing the detection and quantification of CNTs in cells using a multispectral imaging flow cytometer (ImageStream, Amnis). This newly developed device integrates both a high-throughput of cells and high resolution imaging, providing thus images for each cell directly in flow and therefore statistically relevant image analysis. Each cell image is acquired on bright-field (BF), dark-field (DF), and fluorescent channels, giving access respectively to the level and the distribution of light absorption, light scattered and fluorescence for each cell. The analysis consists then in a pixel-by-pixel comparison of each image, of the 7,000-10,000 cells acquired for each condition of the experiment. Localization and quantification of CNTs is made possible thanks to some particular intrinsic properties of CNTs: strong light absorbance and scattering; indeed CNTs appear as strongly absorbed dark spots on BF and bright spots on DF with a precise colocalization.
This methodology could have a considerable impact on studies about interactions between nanomaterials and cells given that this protocol is applicable for a large range of nanomaterials, insofar as they are capable of absorbing (and/or scattering) strongly enough the light.

In this study, the main purpose was to monitor the cellular uptake and eventual exocytosis of carbon nanotubes (CNTs). From this perspective, we proposed here a unique method using multispectral imaging flow cytometry allowing a quantification and localization of CNTs in a statistically relevant number of cells.

Carbon-based nanomaterials, like carbon nanotubes (CNTs), belong to this type of nanoparticles which are very difficult to discriminate from carbon-rich ...

Synthesis of an Intein-mediated Artificial Protein Hydrogel

We present the synthesis of a highly stable protein hydrogel mediated by a split-intein-catalyzed protein trans-splicing reaction. The building blocks of this hydrogel are two protein block-copolymers each containing a subunit of a trimeric protein that serves as a crosslinker and one half of a split intein. A highly hydrophilic random coil is inserted into one of the block-copolymers for water retention. Mixing of the two protein block copolymers triggers an intein trans-splicing reaction, yielding a polypeptide unit with crosslinkers at either end that rapidly self-assembles into a hydrogel. This hydrogel is very stable under both acidic and basic conditions, at temperatures up to 50 &#176;C, and in organic solvents. The hydrogel rapidly reforms after shear-induced rupture. Incorporation of a &#34;docking station peptide&#34; into the hydrogel building block enables convenient incorporation of &#34;docking protein&#34;-tagged target proteins. The hydrogel is compatible with tissue culture growth media, supports the diffusion of 20 kDa molecules, and enables the immobilization of bioactive globular proteins. The application of the intein-mediated protein hydrogel as an organic-solvent-compatible biocatalyst was demonstrated by encapsulating the horseradish peroxidase enzyme and corroborating its activity.

We present the synthesis of a split-intein-mediated protein hydrogel. The building blocks of this hydrogel are two protein copolymers each containing a subunit of a trimeric protein that serves as a crosslinker and one half of a split intein. Mixing of the two protein copolymers triggers an intein trans-splicing reaction, yielding a polypeptide unit that self-assembles into a hydrogel. This hydrogel is highly pH- and temperature-stable, compatible with organic solvents, and easily incorporates functional globular proteins.

We present the synthesis of a highly stable protein hydrogel mediated by a split-intein-catalyzed protein trans-splicing reaction. The building blocks of ...

Synthesis of Keratin-based Nanofiber for Biomedical Engineering

Electrospinning, due to its versatility and potential for applications in various fields, is being frequently used to fabricate nanofibers. Production of these porous nanofibers is of great interest due to their unique physiochemical properties. Here we elaborate on the fabrication of keratin containing poly (&#949;-caprolactone) (PCL) nanofibers (i.e., PCL/keratin composite fiber). Water soluble keratin was first extracted from human hair and mixed with PCL in different ratios. The blended solution of PCL/keratin was transformed into nanofibrous membranes using a laboratory designed electrospinning set up. Fiber morphology and mechanical properties of the obtained nanofiber were observed and measured using scanning electron microscopy and tensile tester. Furthermore, degradability and chemical properties of the nanofiber were studied by FTIR. SEM images showed uniform surface morphology for PCL/keratin fibers of different compositions. These PCL/keratin fibers also showed excellent mechanical properties such as Young&#39;s modulus and failure point. Fibroblast cells were able to attach and proliferate thus proving good cell viability. Based on the characteristics discussed above, we can strongly argue that the blended nanofibers of natural and synthetic polymers can represent an excellent development of composite materials that can be used for different biomedical applications.

Electrospun nanofibers have a high surface area to weight ratio, excellent mechanical integrity, and support cell growth and proliferation. These nanofibers have a wide range of biomedical applications. Here we fabricate keratin/ PCL nanofibers, using the electrospinning technique, and characterize the fibers for possible applications in tissue engineering.

Electrospinning, due to its versatility and potential for applications in various fields, is being frequently used to fabricate nanofibers. Production of ...

Engineering Molecular Recognition with Bio-mimetic Polymers on Single Walled Carbon Nanotubes

Semiconducting single-wall carbon nanotubes (SWNTs) are a class of optically active nanomaterial that fluoresce in the near infrared, coinciding with the optical window where biological samples are most transparent. Here, we outline techniques to adsorb amphiphilic polymers and polynucleic acids onto the surface of SWNTs to engineer their corona phases and create novel molecular sensors for small molecules and proteins. These functionalized SWNT sensors are both biocompatible and stable. Polymers are adsorbed onto the nanotube surface either by direct sonication of SWNTs and polymer or by suspending SWNTs using a surfactant followed by dialysis with polymer. The fluorescence emission, stability, and response of these sensors to target analytes are confirmed using absorbance and near-infrared fluorescence spectroscopy. Furthermore, we demonstrate surface immobilization of the sensors onto glass slides to enable single-molecule fluorescence microscopy to characterize polymer adsorption and analyte binding kinetics.

We present a protocol for engineering the corona phase of near infrared fluorescent single walled carbon nanotubes (SWNTs) using amphiphilic polymers and DNA to develop sensors for molecular targets without known recognition elements.

Semiconducting single-wall carbon nanotubes (SWNTs) are a class of optically active nanomaterial that fluoresce in the near infrared, coinciding with the ...

Targeted Plasma Membrane Delivery of a Hydrophobic Cargo Encapsulated in a Liquid Crystal Nanoparticle Carrier

The controlled delivery of drug/imaging agents to cells is critical for the development of therapeutics and for the study of cellular signaling processes. Recently, nanoparticles (NPs) have shown significant promise in the development of such delivery systems. Here, a liquid crystal NP (LCNP)-based delivery system has been employed for the controlled delivery of a water-insoluble dye, 3,3&#8242;-dioctadecyloxacarbocyanine perchlorate (DiO), from within the NP core to the hydrophobic region of a plasma membrane bilayer. During the synthesis of the NPs, the dye was efficiently incorporated into the hydrophobic LCNP core, as confirmed by multiple spectroscopic analyses. Conjugation of a PEGylated cholesterol derivative to the NP surface (DiO-LCNP-PEG-Chol) enabled the binding of the dye-loaded NPs to the plasma membrane in HEK 293T/17 cells. Time-resolved laser scanning confocal microscopy and F&#246;rster resonance energy transfer (FRET) imaging confirmed the passive efflux of DiO from the LCNP core and its insertion into the plasma membrane bilayer. Finally, the delivery of DiO as a LCNP-PEG-Chol attenuated the cytotoxicity of DiO; the NP form of DiO exhibited ~30-40% less toxicity compared to DiOfree delivered from bulk solution. This approach demonstrates the utility of the LCNP platform as an efficient modality for the membrane-specific delivery and modulation of hydrophobic molecular cargos.

A liquid crystal nanoparticle (LCNP) nanocarrier is exploited as a vehicle for the controlled delivery of a hydrophobic cargo to the plasma membrane of living cells.

The controlled delivery of drug/imaging agents to cells is critical for the development of therapeutics and for the study of cellular signaling processes. ...

DNA Nanotubes as a Versatile Tool to Study Semiflexible Polymers

Mechanical properties of complex, polymer-based soft matter, such as cells or biopolymer networks, can be understood in neither the classical frame of flexible polymers nor of rigid rods. Underlying filaments remain outstretched due to their non-vanishing backbone stiffness, which is quantified via the persistence length (lp), but they are also subject to strong thermal fluctuations. Their finite bending stiffness leads to unique, non-trivial collective mechanics of bulk networks, enabling the formation of stable scaffolds at low volume fractions while providing large mesh sizes. This underlying principle is prevalent in nature (e.g., in cells or tissues), minimizing the high molecular content and thereby facilitating diffusive or active transport. Due to their biological implications and potential technological applications in biocompatible hydrogels, semiflexible polymers have been subject to considerable study. However, comprehensible investigations remained challenging since they relied on natural polymers, such as actin filaments, which are not freely tunable. Despite these limitations and due to the lack of synthetic, mechanically tunable, and semiflexible polymers, actin filaments were established as the common model system. A major limitation is that the central quantity lp cannot be freely tuned to study its impact on macroscopic bulk structures. This limitation was resolved by employing structurally programmable DNA nanotubes, enabling controlled alteration of the filament stiffness. They are formed through tile-based designs, where a discrete set of partially complementary strands hybridize in a ring structure with a discrete circumference. These rings feature sticky ends, enabling the effective polymerization into filaments several microns in length, and display similar polymerization kinetics as natural biopolymers. Due to their programmable mechanics, these tubes are versatile, novel tools to study the impact of lp on the single-molecule as well as the bulk scale. In contrast to actin filaments, they remain stable over weeks, without notable degeneration, and their handling is comparably straightforward.

Semiflexible polymers display unique mechanical properties that are extensively applied by living systems. However, systematic studies on biopolymers are limited since properties such as polymer rigidity are inaccessible. This manuscript describes how this limitation is circumvented by programmable DNA nanotubes, enabling experimental studies on the impact of filament rigidity.

Mechanical properties of complex, polymer-based soft matter, such as cells or biopolymer networks, can be understood in neither the classical frame of ...

Melt Electrospinning Writing of Three-dimensional Poly(&#949;-caprolactone) Scaffolds with Controllable Morphologies for Tissue Engineering Applications

This tutorial reflects on the fundamental principles and guidelines for electrospinning writing with polymer melts, an additive manufacturing technology with great potential for biomedical applications. The technique facilitates the direct deposition of biocompatible polymer fibers to fabricate well-ordered scaffolds in the sub-micron to micro scale range. The establishment of a stable, viscoelastic, polymer jet between a spinneret and a collector is achieved using an applied voltage and can be direct-written. A significant benefit of a typical porous scaffold is a high surface-to-volume ratio which provides increased effective adhesion sites for cell attachment and growth. Controlling the printing process by fine-tuning the system parameters enables high reproducibility in the quality of the printed scaffolds. It also provides a flexible manufacturing platform for users to tailor the morphological structures of the scaffolds to their specific requirements. For this purpose, we present a protocol to obtain different fiber diameters using melt electrospinning writing (MEW) with a guided amendment of the parameters, including flow rate, voltage and collection speed. Furthermore, we demonstrate how to optimize the jet, discuss often experienced technical challenges, explain troubleshooting techniques and showcase a wide range of printable scaffold architectures.

Melt Electrospinning Writing of Three-dimensional Poly(&amp;#949;-caprolactone) Scaffolds with Controllable Morphologies for Tissue Engineering Applications

This protocol serves as a comprehensive guideline to fabricate scaffolds via electrospinning with polymer melts in a direct writing mode. We systematically outline the process and define the appropriate parameter settings for achieving targeted scaffold architectures.

This tutorial reflects on the fundamental principles and guidelines for electrospinning writing with polymer melts, an additive manufacturing technology ...

Microhoneycomb Monoliths Prepared by the Unidirectional Freeze-drying of Cellulose Nanofiber Based Sols: Method and Extensions

Monolithic honeycomb structures have been attractive to multidisciplinary fields due to their high strength-to-weight ratio. Particularly, microhoneycomb monoliths (MHMs) with micrometer-scale channels are expected as efficient platforms for reactions and separations because of their large surface areas. Up to now, MHMs have been prepared by a unidirectional freeze-drying (UDF) method only from very limited precursors. Herein, we report a protocol from which a series of MHMs consisting of different components can be obtained. Recently, we found that cellulose nanofibers function as a distinct structure-directing agent towards the formation of MHMs through the UDF process. By mixing the cellulose nanofibers with water soluble substances which do not yield MHMs, a variety of composite MHMs can be prepared. This significantly enriches the chemical constitution of MHMs towards versatile applications.

Here, we present a general protocol to prepare a variety of microhoneycomb monoliths (MHMs) in which fluid can pass through with an extremely low pressure drop. MHMs obtained are expected to be used as filters, catalyst supports, flow-type electrodes, sensors and scaffolds for biomaterials.

Monolithic honeycomb structures have been attractive to multidisciplinary fields due to their high strength-to-weight ratio. Particularly, microhoneycomb ...

Synthesis of Multi-walled Carbon Nanotubes Modified with Silver Nanoparticles and Evaluation of Their Antibacterial Activities and Cytotoxic Properties

In this study, multi-walled carbon nanotubes (MWCNTs) were treated with an aqueous sulfuric acid solution to form an oxygen-based functional group. Silver MWCNTs were prepared by the reductive deposition of silver from an aqueous solution of AgNO3 on the oxidized MWCNTs. Given the unique color of the CNTs, it was not possible to apply them to the minimum inhibitory concentration or mitochondrial toxicity assays to evaluate the toxicity and antibacterial properties, since they would interfere with the assays. The inhibition zone and minimum bactericidal concentration for the Ag-MWCNTs were measured and Live/Dead and Trypan Blue assays were used to measure the toxicity and antibacterial properties without interfering with the color of the CNTs.

In this study, antimicrobial nanomaterials were synthesized by acidic oxidation of multiwalled carbon nanotubes and subsequent reductive deposition of silver nanoparticles. Antimicrobial activity and cytotoxicity tests were performed with the as-prepared nanomaterials.

In this study, multi-walled carbon nanotubes (MWCNTs) were treated with an aqueous sulfuric acid solution to form an oxygen-based functional group. Silver ...