Polyacrylonitrile Nanofibers: Formation Mechanism and Applications as a Photoluminescent Material and Carbon-Nanofiber Precursor

Jang, J.,Bae, J.,Park, E. WILEY-VCH Verlag 2006 Advanced Functional Materials Vol.16 No.11

<P>The facile synthesis of polyacrylonitrile (PAN) nanofibers is achieved using a microemulsion polymerization. The detailed formation mechanism of polymer nanofibers is examined using electron microscopy and UV-vis and Fourier transform infrared spectroscopies, and the optoelectronic properties are studied by confocal laser scanning microscopy. The effects of surfactant properties, such as concentration, chain length, and ionic character, as well as monomer structure and polymerization temperature, on the structure of the resulting polymer nanofibers are also investigated extensively. Importantly, PAN nanofibers exhibited novel photoluminescence (PL), which is observed for the first time. The PL of PAN nanofibers is significantly different from that of PAN nanoparticles. The PAN nanofibers are also used as a precursor for carbon nanofibers. The carbonization temperature has a dominant effect on the degree of crystallinity of the resulting carbon nanofibers. This study is the first demonstration of the fabrication of polymer and carbon nanofibers using a convenient polymerization technique.</P> <B>Graphic Abstract</B> <P>Polymer nanofibers with tunable diameters (see figure) are fabricated by microemulsion polymerization. Sphere-to-cylinder micelle transformation due to the addition of ferric chloride is crucial for nanofiber formation. The diameter of the polymer nanofibers depends on the surfactant properties, the monomer type, and the polymerization temperature. This is the first demonstration of the convenient synthesis of polymer nanofibers using a simple polymerization strategy. <img src='wiley_img/1616301X-2006-16-11-ADFM200500598-content.gif' alt='wiley_img/1616301X-2006-16-11-ADFM200500598-content'> </P>

Radially patterned polycaprolactone nanofibers as an active wound dressing agent

Dongwoo Shin,Min Sup Kim,양채은,이원재,노태석,백우열 대한성형외과학회 2019 Archives of Plastic Surgery Vol.46 No.5

Background The objectives of this study were to design polycaprolactone nanofibers with a radial pattern using a modified electrospinning method and to evaluate the effect of radial nanofiber deposition on mechanical and biological properties compared to non-patterned samples. Methods Radially patterned polycaprolactone nanofibers were prepared with a modified electrospinning method and compared with randomly deposited nanofibers. The surface morphology of samples was observed under scanning electron microscopy (SEM). The tensile properties of nanofibrous mats were measured using a tabletop uniaxial testing machine. Fluorescence-stained human bone marrow stem cells were placed along the perimeter of the radially patterned and randomly deposited. Their migration toward the center was observed on days 1, 4, and 7, and quantitatively measured using ImageJ software. Results Overall, there were no statistically significant differences in mechanical properties between the two types of polycaprolactone nanofibrous mats. SEM images of the obtained samples suggested that the directionality of the nanofibers was toward the central area, regardless of where the nanofibers were located throughout the entire sample. Florescence images showed stronger fluorescence inside the circle in radially aligned nanofibers, with significant differences on days 4 and 7, indicating that migration was quicker along radially aligned nanofibers than along randomly deposited nanofibers. Conclusions In this study, we successfully used modified electrospinning to fabricate radially aligned nanofibers with similar mechanical properties to those of conventional randomly aligned nanofibers. In addition, we observed faster migration along radially aligned nanofibers than along randomly deposited nanofibers. Collectively, the radially aligned nanofibers may have the potential for tissue regeneration in combination with stem cells.

Radially patterned polycaprolactone nanofibers as an active wound dressing agent

Shin, Dongwoo,Kim, Min Sup,Yang, Chae Eun,Lee, Won Jai,Roh, Tai Suk,Baek, Wooyeol Korean Society of Plastic and Reconstructive Surge 2019 Archives of Plastic Surgery Vol.46 No.5

Background The objectives of this study were to design polycaprolactone nanofibers with a radial pattern using a modified electrospinning method and to evaluate the effect of radial nanofiber deposition on mechanical and biological properties compared to non-patterned samples. Methods Radially patterned polycaprolactone nanofibers were prepared with a modified electrospinning method and compared with randomly deposited nanofibers. The surface morphology of samples was observed under scanning electron microscopy (SEM). The tensile properties of nanofibrous mats were measured using a tabletop uniaxial testing machine. Fluorescence-stained human bone marrow stem cells were placed along the perimeter of the radially patterned and randomly deposited. Their migration toward the center was observed on days 1, 4, and 7, and quantitatively measured using ImageJ software. Results Overall, there were no statistically significant differences in mechanical properties between the two types of polycaprolactone nanofibrous mats. SEM images of the obtained samples suggested that the directionality of the nanofibers was toward the central area, regardless of where the nanofibers were located throughout the entire sample. Florescence images showed stronger fluorescence inside the circle in radially aligned nanofibers, with significant differences on days 4 and 7, indicating that migration was quicker along radially aligned nanofibers than along randomly deposited nanofibers. Conclusions In this study, we successfully used modified electrospinning to fabricate radially aligned nanofibers with similar mechanical properties to those of conventional randomly aligned nanofibers. In addition, we observed faster migration along radially aligned nanofibers than along randomly deposited nanofibers. Collectively, the radially aligned nanofibers may have the potential for tissue regeneration in combination with stem cells.

Fabrication and characterization of the magnetic ferrite nanofibers by electrospinning process

Na, Kyeong-Han,Kim, Wan-Tae,Park, Dong-Cheol,Shin, Hyun-Gyoo,Lee, Sea-Hyun,Park, Jisun,Song, Tae-Hyeob,Choi, Won-Youl Elsevier 2018 THIN SOLID FILMS - Vol.660 No.-

<P><B>Abstract</B></P> <P>Since the magnetic properties of materials are greatly affected by their microstructure, nanostructuring of magnetic materials is attempted in various directions. Various processes have been used to synthesis one dimensional nanomaterials: template, hydrothermal, anodizing, and electrospinning. Among these processes, nanofibers fabricated by the electrospinning method are excellent for reproducibility and have a large aspect ratio. In addition, there have been many attempts to fabricate ceramic nanofibers with a more intricate shape using a sol-gel reaction. In this study, the electrospinning conditions for synthesizing ferrite (α-Fe<SUB>2</SUB>O<SUB>3</SUB>) nanofiber were optimized by the preliminary results of polyvinyl alcohol (PVA) nanofiber. As-spun composite nanofibers of PVA/Fe(NO<SUB>3</SUB>)<SUB>3</SUB>·9H<SUB>2</SUB>O were transformed to an α-Fe<SUB>2</SUB>O<SUB>3</SUB> phase by heat treatment at 550 °C. After heat treatment, the diameters ranged from 105 nm to 124 nm in as-spun composite nanofibers, and with a decrease in PVA content after heat treatment, the diameters ranged from 59 nm to 96 nm. We investigated the magnetization properties with the microstructure of α-Fe<SUB>2</SUB>O<SUB>3</SUB> nanofiber by a vibrating sample magnetometer. The saturation magnetization increased with an increasing diameter of the α-Fe<SUB>2</SUB>O<SUB>3</SUB> nanofiber, and highest value of 26.2 A·m<SUP>2</SUP>/kg was measured in the α-Fe<SUB>2</SUB>O<SUB>3</SUB> nanofibers with the largest diameter with a PVA content of 0.12 g/ml. The microstructure and magnetic properties of the α-Fe<SUB>2</SUB>O<SUB>3</SUB> nanofibers were controlled by an electrospinning process, and we were able to optimize the α-Fe<SUB>2</SUB>O<SUB>3</SUB> nanofibers for various application fields, such as electromagnetic interference and electromagnetic pulse absorbers.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Electrospinning process to control the microstructure of nanofibers </LI> <LI> Synthesis of α-Fe2O3 nanofibers using ferric nitrate and heat treatment. </LI> <LI> Magnetization behavior of α-Fe2O3 nanofibers with change of average diameter. </LI> <LI> Increased diameter of α-Fe<SUB>2</SUB>O<SUB>3</SUB> nanofibers resulted in higher saturation magnetization. </LI> </UL> </P>

A novel approach to fabricate silk nanofibers containing hydroxyapatite nanoparticles using a three-way stopcock connector

Sheikh, Faheem A,Ju, Hyung Woo,Moon, Bo Mi,Park, Hyun Jung,Kim, Jung Ho,Lee, Ok Joo,Park, Chan Hum Springer 2013 Nanoscale research letters Vol.8 No.1

<P>Electrospinning technique is commonly used to produce micro- and/or nanofibers, which utilizes electrical forces to produce polymeric fibers with diameters ranging from several micrometers down to few nanometers. Desirably, electrospun materials provide highly porous structure and appropriate pore size for initial cell attachment and proliferation and thereby enable the exchange of nutrients. Composite nanofibers consisting of silk and hydroxyapatite nanoparticles (HAp) (NPs) had been considered as an excellent choice due to their efficient biocompatibility and bone-mimicking properties. To prepare these nanofiber composites, it requires the use of acidic solutions which have serious consequences on the nature of both silk and HAp NPs. It is ideal to create these nanofibers using aqueous solutions in which the physicochemical nature of both materials can be retained. However, to create those nanofibers is often difficult to obtain because of the fact that aqueous solutions of silk and HAp NPs can precipitate before they can be ejected into fibers during the electrospinning process. In this work, we had successfully used a three-way stopcock connector to mix the two different solutions, and very shortly, this solution is ejected out to form nanofibers due to electric fields. Different blend ratios consisting HAp NPs had been electrospun into nanofibers. The physicochemical aspects of fabricated nanofiber had been characterized by different state of techniques like that of FE-SEM, EDS, TEM, TEM-EDS, TGA, FT-IR, and XRD. These characterization techniques revealed that HAp NPs can be easily introduced in silk nanofibers using a stopcock connector, and this method favorably preserves the intact nature of silk fibroin and HAp NPs. Moreover, nanofibers obtained by this strategy were tested for cell toxicity and cell attachment studies using NIH 3 T3 fibroblasts which indicated non-toxic behavior and good attachment of cells upon incubation in the presence of nanofibers.</P>

Self synthesize of silver nanoparticles in/on polyurethane nanofibers: Nano-biotechnological approach

Sheikh, Faheem A.,Barakat, Nasser A. M.,Kanjwal, Muzafar A.,Jeon, Seol-Hee,Kang, Hyung-Sub,Kim, Hak-Yong Wiley Subscription Services, Inc., A Wiley Company 2010 Journal of applied polymer science Vol.115 No.6

<P>In this study, we are introducing a new class of Polyurethane (PU) nanofibers containing silver nanoparticles (NPs) by electrospinning. A simple method not depending on the addition of foreign chemicals has been used to self-synthesize of silver NPs in/on PU nanofibers. Typically, a sol−gel consisting of AgNO<SUB>3</SUB>/PU/N,N-dimethylformamide (DMF) has been electrospun and aged for a week, so silver NPs have been created in/on PU nanofibers. Syntheses of silver NPs were carried out by exploiting the reduction ability of the DMF solvent which is the main constituent to obtain PU electrospun nanofibers in decomposition of silver nitrate precursor into silver NPs. Physiochemical characterizations confirmed well oriented nanofibers and good dispersing of pure silver NPs. Various parameters affecting utilizing of the prepared nanofibers on various nano-biotechnological fields have been studied. For instance, the obtained nanofiber mats were checked for mechanical properties which showed the improvement of the tensile strength upon increase in silver NPs content. Moreover, the nanofibers were subjected to 10 times successive washing experiments with using solid to liquid ratio of 3 : 5000 for 25 h, UV spectroscopy analysis reveals no losses of silver NPs from the PU nanofibers. 3T3-L1 fibroblasts were cultured in presence of the designed nanofibers. The morphological features of the cells attached on nanofibers were examined by BIO-SEM, which showed well attachment of cells to fibrous mats. The cytotoxicity results indicated absence of toxic effect on the 3T3-L1 cells after cell culturing. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010</P>

Fabrication of Nanofiber Microarchitectures Localized within Hydrogel Microparticles and Their Application to Protein Delivery and Cell Encapsulation

Lee, Hyun Jong,Park, Young Ha,Koh, Won‐,Gun WILEY‐VCH Verlag 2013 Advanced functional materials Vol.23 No.5

<P><B>Abstract</B></P><P>A simple method to generate well‐defined microscopic architectures composed of electrospun nanofibers is reported and their potential application to biomedical fields are described. The photopatterning of polyethylene glycol (PEG) hydrogel on electrospun polycarprolactone (PCL) nanofibers leads to the formation of two different microdomains in nanofibrous mats: a bare nanofiber region and a hydrogel‐entrapped nanofiber region. The selective dissolution of bare nanofibers with an organic solvent that cannot penetrate the PEG hydrogel enables the localization of PCL nanofibers within the hydrogel microstructures, thus generating microarchitectured nanofibers. The resultant microarchitectures are easily detached from the substrate by the water‐induced swelling of the PEG hydrogel. Microparticles are ultimately obtained, the size and shape of which can be easily controlled with proper photomask designs. In proof of concept experiments, bovine serum albumin(BSA)‐loaded PCL nanofibers that are entrapped within the hydrogel microparticles are prepared and the sustained release of BSA from micropatterned nanofibers is successfully demonstrated, indicating the potential application of the proposed microarchitectured nanofibers to drug delivery systems. For another possible application, the capability of the nanofiber‐incorporated hydrogel to encapsulate mammalian cells is investigated and the incorporation of nanofibers within the PEG hydrogel promoted cell adhesion and spreading when compared with bare PEG hydrogel is confirmed.</P>

Thermal Characteristics of Polyethylene Oxide and Functionalized Bacterial Cellulose Whisker Nanoparticle Composite Nanofibers

윤옥자 한국고분자학회 2016 Macromolecular Research Vol.24 No.11

Composite nanofibers of polyethylene oxide (PEO)/bacterial cellulose whisker nanoparticles (BCW NPs) and PEO/functionalized bacterial cellulose whisker nanoparticles (f-BCW NPs) were fabricated by an electrospinning process. BCW NPs were prepared using a blender in order to increase the filler density in composite nanofibers. Nitrogen functionalization of the f-BCW NPs was performed by plasma treatment using a microwave oven. The chemical bonding between the nitrogen functional groups of f-BCW NPs and the hydroxyl groups of the polymer chains in the PEO matrix was enhanced by the nitrogen functionalization. The average diameter of the PEO/f-BCW NP composite nanofibers was slightly larger than that of PEO nanofibers and PEO/BCW NP composite nanofibers at the same concentration. The melting temperature (Tm), crystallization temperature (Tc), and weight loss of PEO/f- BCW NP composite nanofibers decreased compared to those of the PEO nanofibers and PEO/BCW NP composite nanofibers. This was a result of the f-BCW NPs hindering the crystallization of the PEO nanofiber structures. The strong interfacial interactions between the f-BCW NP nanofillers and the polymer matrix increased the glass transition temperature (Tg) compared to PEO nanofibers and PEO/BCW NP composite nanofibers. These results demonstrated that N2 plasma treatment of BCW NPs embedded in PEO nanofiber was a useful tool for improving their thermal characteristics for biological applications.

Cellulose Monoacetate/Tetraethyl Orthosilicate Hybrid Nanofibers for Electrochemical DNA Biosensors

Sinem Civan,Seval Aydin,Nilay Aladag Tanik,Yakup Aykut 한국섬유공학회 2021 Fibers and polymers Vol.22 No.4

Cellulose monoacetate/tetraethyl orthosilicate (CMA/TEOS) hybrid nanofibers were produced with differentratios via electrospinning and used for guanine oxidation analysis in the single strand deoxyribonucleic acid (ssDNA)molecules by electrochemical method. Nanofiber (NF) diameters for pure CMA dramatically decreased from between 2.4 μ-306 nm to between 958-42 nm with addition of hydrochloric acid (HCl) catalyzer into the electrospinning solution. UniformCMA nanofibers morphologies transform to more defect structures containing particular structures with the addition andincrease of TEOS content in CMA electrospinning solution. Also, nanofibers' diameters range became more fluctuated formand ultrafine nanofibers (diameters below 100 nm) existed more in the nanofiber mat. Even though the melting point wasseen at CMA nanofibers, melting points were not detectable in CMA/TEOS NFs since TEOS addition does not allow anappropriate crystallization. Thermal analysis results revealed that residual contents after TGA measurement in nitrogenatmosphere were gradually increased by increasing TEOS ratio in CMA/TEOS nanofibers. ssDNA molecules were immobilizedon the as-spun nanofibers and differential pulse voltammetry (DPV) measurements were carried out to investigate theguanine oxidation in ssDNA. Guanine oxidation signal intensities decreased with the initial addition of TEOS to CMAnanofibers and increases again by increasing TEOS content in CMA/TEOS hybrid nanofibers and then gradually decreasesagain with increasing TEOS content. The prepared CMA/TEOS hybrid nanofibers could be a promising candidate as anelectrode interface for genetic molecule detection via electrochemical methods.

Modulation of Osteogenic Differentiation of Human Mesenchymal Stem Cells by Poly[(L-lactide)-co-(ϵ-caprolactone)]/Gelatin Nanofibers

Rim, Nae Gyune,Lee, Ji Hye,Jeong, Sung In,Lee, Bu Kyu,Kim, Chun Ho,Shin, Heungsoo WILEY-VCH Verlag 2009 Macromolecular bioscience Vol.9 No.8

<P>Developing biomaterial scaffolds to elicit specific cell responses is important in many tissue engineering applications. We hypothesized that the chemical composition of the scaffold may be a key determinant for the effective induction of differentiation in human mesenchymal stem cells (hMSCs). In this study, electrospun nanofibers with different chemical compositions were fabricated using poly[(L-lactide)-co-(ϵ-caprolactone)] (PLCL) and gelatin. Scanning electron microscopy (SEM) images showed a randomly arranged structure of nanofibers with diameters ranging from 400 nm to 600 nm. The incorporation of gelatin in the nanofibers stimulated the adhesion and osteogenic differentiation of hMSCs. For example, the well-stretched and polygonal morphology of hMSCs was observed on the gelatin-containing nanofibers, while the cells cultured on the PLCL nanofibers were contracted. The DNA content and alkaline phosphatase activity were significantly increased on the PLCL/gelatin blended nanofibers. Expression of osteogenic genes including alkaline phosphatase (ALP), osteocalcin (OCN), and collagen type I-α2 (Col I-α2) were also upregulated in cells cultured on nanofibers with gelatin. Mineralization of hMSCs was analyzed by von Kossa staining and the amount of calcium was significantly enhanced on the gelatin-incorporated nanofibers. These results suggest that the chemical composition of the underlying scaffolds play a key role in regulating the osteogenic differentiation of hMSCs.</P><P> <img src='wiley_img/16165187-2009-9-8-MABI200800358-gra001.gif' alt='wiley_img/16165187-2009-9-8-MABI200800358-gra001'> </P> <B>Graphic Abstract</B> <P>Incorporation of gelatin into poly[(L-lactide)-co-(ϵ-carprolactone)] (PLCL) nanofibers enhanced adhesion of human mesenchymal stem cells (hMSCs). Alkaline phosphatase activity and expression of osteogenic genes were increased in hMSCs cultured on gelatin-containing nanofibers and the hMSCs also showed enhanced calcium deposition. Chemical composition of scaffolds plays an important role in modulation of the osteogenic differentiation of hMSCs. <img src='wiley_img/16165187-2009-9-8-MABI200800358-content.gif' alt='wiley_img/16165187-2009-9-8-MABI200800358-content'> </P>