Mujibur R. Khan

Encapsulation of anticancer drugs (5-Fluorouracil and Paclitaxel) into polycaprolactone (PCL) nanofibers and in vitro testing for sustained and targeted therapy

We report a continuous nanoscale encapsulation of cancer drugs 5-Fluorouracil (FU) and Paclitaxel into biocompatible polycaprolactone (PCL) nanofibers (NFs) using core-sheath electrospinning process. A high potential electric field of 19-23.2 kV was used to draw a compound solution jet from a specialized coaxial spinneret. Using of DMF in both core and Sheath resulted in NFs within 50-160 nm along with large beaded structures. Addition of Trichloromethane (TCM) or Trifluoroethanol (TFE) in sheath turned NFs in more uniform and thin fiber structure. The diameter range for paclitaxel encapsulated fibers was 22-90 nm with encapsulation efficiency of 77.5% and the amount of drug was only 4 to 5% of sheath polymer. Addition of PVA within core resulted drug nanocrystal formation outside of sheath and poor encapsulation efficiency (52%) with rapid initial release (52-53%) in first 3 days. Drug release test of NFs in different pH exhibited increase of release rate with the decrease of media pH. In-vitro cell viability test with FU encapsulated NFs in human prostatic cancer PC3 cells exhibited 38% alive cells at 5 μM concentration while in pristine FU 43% cells were alive. Paclitaxel encapsulated NFs with breast cancer cells also exhibited increased efficacy in comparison to pristine anticancer drugs. Continuous decrease of cell density indicated the slow release of cancer drugs from the NFs. Both PCL+Paclitaxel and PCL+5FU treated conditions caused breast cancer cell death between 40% to 50%.

A study of mechanical behavior and morphology of carbon nanotube reinforced UHMWPE/Nylon 6 hybrid polymer nanocomposite fiber

We report a phenomenal increase in strength, modulus, and fracture strain of ultra high molecular weight polyethylene (UHMWPE) fiber by 103 %, 219 %, and 108 %, respectively through hybridizing this fiber with Nylon 6 as a minor phase and simultaneously reinforcing it with single-walled carbon nanotubes (SWCNTs). Loading of Nylon 6 and SWCNTs into UHMWPE was 20.0 wt% and 2.0 wt%, respectively. Hybridized fibers were processed using a solution spinning method coupled with melt mixing and extrusion. We claim that the enhancement in strain-to-failure of the nanocomposites is due to induced plasticity in the hybridized Nylon 6-UHMWPE polymers. The enhancement in strength and stiffness in the nanocomposites is attributed to the load sharing of the SWCNTs during deformation. Differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) studies showed that changes in percent crystallinity, rate of crystallization, crystallite size, alignment of nanotubes, sliding of polymer interfaces and strong adhesion of CNT/polymer blends were responsible for such enhancements.

Investigation of Synthesis and Processing of Cellulose, Cellulose Acetate and Poly(Ethylene Oxide) Nanofibers Incorporating Anti-Cancer/Tumor Drug Cis-Diammineplatinum (II) Dichloride Using Electrospinning Techniques

Abstract A model anti-cancer/tumor drug cis-diammineplatinum (II) dichloride (cisplatin) was loaded into micro- and nanofibers of cellulose, cellulose acetate (CA) and poly(ethylene oxide) (PEO), using various electrospinning techniques. Single-nozzle electrospinning was used to fabricate neat fibers of each category. Drug loading in cellulose fibers was performed using single-nozzle electrospinning. Encapsulation of cisplatin in CA and PEO-based fibers was performed using coaxial electrospinning. Morphological analysis of the fibers was performed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The various categories of fibers exhibited diverse morphological features depending on the material compositions and applied process parameters. The drug-loaded cellulose nanofibers showed attached particles on the surface. These particles were composed of both the polymer and the drug. The CA-cisplatin fibers exhibited drug encapsulation within various diverse morphological conformations: hierarchical structures such as straw-sheaf-shaped particles, dendritic branched nanofibers and swollen fibers with large beads. However, in the case of PEO fibers, drug encapsulation was observed inside repeating dumbbell-shaped structures. Morphological development of the fibers and corresponding mode of drug encapsulation were correlated with process parameters such as applied voltage, concentrations and relative feed rates of the solutions and conductivities of the solvents.

Morphological Characteristics of UHMWPE+Nylon- 6+SWCNT Solution-Spun Hybrid Nanocomposite Fibers Compatibilized with PE-g-MAH’

Hybrid nanocomposite fibers from a blend of Ultrahigh molecular weight polyethylene (UHM-WPE)+Nylon-6+single-walled carbon nanotubes (SWCNT) were produced using a solution spinning process, both with and without a compatibilizer, Polyethylene-graft-Maleic Anhydride (PEG-g-MAH). The loading of Nylon-6, PE-g-MAH and SWCNTs was 20, 3, and 2 wt% of UHMWPE. A comparative morphological study of the fibers was performed using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) analysis. SEM images of hybrid fiber cross-sections have shown polymer-coated SWCNTs aligned along the direction of extrusion inside the polymer. The blends with compatibilizer have shown rough and indistinct interfacial separation of the constituent phases, as seen in both cross-sectional and longitudinal views of fibers in SEM micrographs. Whereas, the samples without compatibilizer showed distinct minor polymer phase as droplets. DSC results indicate reduction of crystallinity, crystallization rate and lamellar size in the compatibilized blends. Comparative FTIR analysis of the fiber blends showed the presence of new absorbance peaks (at 1753.62 and 1210–990 cm–1) suggesting formation of imide linkages between the UHMWPE backbone and Nylon-6 chains in the blends with compatibilizer via reactive functional groups present in the PE-g-MAH. The appearance of these peaks were more prominent when nanotubes were present in the blend.

Experimental study of thermopower of SWCNTs and SiC nanoparticles with B–P (born–phosphorus) sol–gel dopants

Seebeck coefficients of randomly distributed single-walled carbon nanotubes (SWCNTs) combined with Silicon Carbide (SiC) nanoparticles were experimentally determined. The Seebeck coefficients of pristine SiC/SWCNT samples were compared with those of SiC/SWCNT samples doped with P-type (Boron) and N-type (Phosphorous) sol–gel dopants. Pristine SiC/SWCNT samples were prepared by depositing SiC nanoparticles and SWCNTs on a non-conductive glass substrate. Doped SiC/SWCNT samples were prepared by coating each half of the samples alternately with B and P sol–gel dopants. Thermoelectric circuits were prepared by creating hot and cold junctions on the P and N-doped ends of the SiC/SWCNT samples with conductive Silver epoxy and Alumel (Ni–Al) wire. Voltage, current and resistance were measured across the samples against temperature difference. The SWCNTs used were approximately 60% semiconducting and 40% metallic. The Seebeck coefficient for pristine SWCNTs was 0.10 ± 0.006 mV per degree Celsius. When diffused with B–P, the Seebeck coefficient increased to 0.308 mV per degree Celsius. Pristine SiC nanoparticles showed no presence of thermoelectric (TE) effect, but substantial TE effects were observed upon inclusion of SWCNTs. Although the samples with various SWCNT compositions showed similar Seebeck coefficients, the current, resistance and power factor (PF) changed accordingly. Resistance of the pristine SWCNTs slightly decreased with increase in temperature. Structure–property relations were determined using scanning electron microscopy (SEM) and Raman spectroscopy. It was revealed that fibre-like SWCNTs created randomly distributed networks with nano-contact junctions inside the SiC matrix. Diffusion of dopants into CNTs in the doped samples increased the charged carrier concentration enhancing the thermopower of SWCNTs. Analysis of the Raman spectra showed an upshift in the tangential vibrational G-band modes of SWCNTs when doped with an electron-acceptor dopant (Boron), and a downshift in the case of an electron-donor dopant (Phosphorus). Incorporation of the dopant materials in the SWCNT structure was also evidenced by the presence of disorder induced D-band peaks in the doped SWCNTs.

Nanoindentation response of Fe-10%Cr bi-crystal structures with Σ5〈001〉 and Σ3〈110〉 tilt boundaries: An atomistic study

In this research, nanoindentation responses of Fe-10%Cr bi-crystal structures containing Σ5{310}〈001〉 and Σ3{111}〈110〉 tilt grain boundaries (GBs) have been investigated using atomistic simulation technique. Deformation analyses identify the nucleation of 1/2〈111〉, 〈001〉 and 1/6〈111〉 types of dislocations within the material. The {110} slip planes are found to be more active than the {123} and {100} slip planes. Load-displacement response and corresponding changes in contact area have been recorded and used to measure material hardness and reduced modulus. The lengths of the nucleated dislocations are measured and used to estimate dislocation density within the plastic zone beneath the indenter. Dislocation motion has been found to be much easier in model with Σ3 boundary and the early interaction of the dislocation with the boundary affects the shape of the load-displacement curve, contact area on the indented surface, and the volume of the plastic zone. The hardness of the material has been found to be affected primarily by the interaction of the dislocation with the boundary, rather than by the dislocation density within the plastic zone. Both the boundaries exhibit maximum resistance to slip transmission even at the maximum indentation depth.

Synthesis and Processing of Solution Spun Cellulose Acetate Fibers Reinforced With Carbon Nanotubes

We report the fabrication of Cellulose Acetate (CA) based fibers reinforced with Multi-Walled Carbon Nanotubes (MWCNTs) using a solution spinning process. The motivation of this work is to produce high performance fibers based on sustainable natural materials as an alternative to synthetic fibers for structural applications. A 30 wt% solution of CA in a binary solvent system of N, N-dimethylacetamide (DMAc) and Acetone (3:7 v/v) was used for the solution spinning of CA fibers. Both neat and CNT-loaded CA fibers were produced. The CNT loading with respect to the polymer was at 0.5 wt%. For CA-MWCNT spinning solutions, the MWCNTs were initially dispersed in the solvent and then CA is added and mixed together. The mixing temperature kept 40–45°C. The viscosity of the CA solution was 8,000 cP. Addition of MWCNT increased the viscosity of the CA solution to 32,000 cP. A lab-scale solution spinning line consisting of a constant torque high temperature gear pump and heated extrusion channels was used to produce both neat and CA-MWCNT fibers. The solution was pumped through a spinneret at the end of the extrusion channel with an orifice as a viscous gel-like filament which was passed through a spool placed in a coagulation bath and then it formed as fiber. The fibers are collected to a takeup roll at a draw ratio of 8.0. Characterization studies of both neat and MWCNT loaded fibers were performed differential scanning calorimetry (DSC), thermo-gravimetric analysis (TGA) and scanning electron microscopy (SEM). DSC analysis of fibers showed reduction in crystallinity of CA upon inclusion of 0.5 wt% MWCNT. TGA analysis showed improvement of thermal stability in CA-MWCNT fibers compared to neat CA. Cross-sections of neat CA fibers showed smooth surfaces with no significant defects, while CA-MWCNT showed formation of micro-voids and irregular features. Longitudinal views of outer surface of both neat CA and CA-MWCNT fibers showed no indication of surface defects or protrusions.Copyright

Fabrication of Polyacrylonitrile Nanofiber Membranes Functionalized With Metal Organic Framework for CO2 Capturing

Crystalline particles known as Metal Organic Frameworks (MOF’s) are known for their large surface area and high adsorption and storage capacity for CO2 gas. Electrospun nanofibers are considered as ideal substrates for synthesizing the MOF particles on the fiber surface. In this project, Polyacrylonitrile (PAN) and a Cu-based MOF known as HKUST-1 were selected as substrate fibers and adsorbent particles respectively. A precursor solution of PAN polymer hybridized with HKUST-1 particles dissolved in Dimehtylformamide (DMF) is used as the primary component solution for electrospinning. SEM images of the electrospun fibers showed small MOF particles formation into the fiber structure. A secondary solvothermal process of MOF particles growing on the fibers was then executed to increase the amount of MOF particles for effectual gas adsorption. The secondary process consists of multiple growth cycles and SEM images showed uniform distribution of porous MOF particles of 2–3μm in size on the fiber surface. EDS report of the fiber confirmed the presence of MOF particles through identification of characteristic Copper elemental peaks of HKUST-1. Thermogravitmetric analysis (TGA) of HKUST-1 doped PAN fiber displayed 32% of total weight loss between 180°C and 350°C thus proving the as-synthesized MOF particles are thermally stable within the mentioned temperature range. A comparative IR spectroscopic result between the gas-treated and gas-untreated fiber samples showed the presence of characteristic peak in the vicinity of 2300 and 2400cm−1 which corroborates the assertion of adsorption of CO2 on the system. Further step involved is to investigate the gas adsorption capacity of the filter system in an experimental test bench. Non-dispersive Infrared (NDIR) CO2 sensors will be used at the gas inlet and outlet parts to measure the concentration of CO2 and determine the amount of gas uptake by the filter system.Copyright

Enhanced Charge Carrier Concentration of SiC/CNT with N and P Type Doping Agents

Single-walled Carbon nanotubes (SWCNTs) have been shown to have excellent conductive properties. SWCNTs were dispersed in a SiC nanoparticle matrix to form a homogeneous mixture that is both mechanically durable and conductive. The SWCNT amount has been varied. SiC/SWCNT mixtures were then doped with various N- and P-type agents, and the resulting samples were analyzed by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). Raman spectra of the samples were also measured for evidence of structural changes. Seebeck coefficients were measured for the doped samples demonstrating the change in thermoelectric properties. Shifts in the G peak (1580.6 cm-1) of the Raman spectra of the samples provides evidence of an increase in charge carrier concentration in the doped samples, correlating well with the Seebeck coefficient results.Copyright

Processing of Hybrid Nanocomposite High Performance Fibers (UHMWPE+NYLON 6+CNT+MAH) Using Solution Spinning Technique

Ultrahigh molecular weight polyethylene (UHMWPE) fiber blends with Nylon-6 and reinforced with single-walled carbon nanotubes (SWCNT) were produced using a solution spinning process. Polyethylene-graft-Maleic Anhydride (PE-g-MAH) was used as a compatibilizer to enhance the interfacial bonding between the polymer phases. The loading of Nylon-6, MAH, and SWCNTs with respect to UHMWPE was 20 wt.%, 10 wt.% and 2 wt.% respectively. The development of morphological characteristics due to the inclusion of a compatibilizer in an immiscible hybrid polymer nanocomposite fiber is hereby discussed. Characterization studies of the hybrid fibers were performed using scanning electron microscopy (SEM), Energy-dispersive X-Ray Spectroscopy (EDS) and Fourier-transform infrared spectroscopy (FTIR).Copyright