Madhav Prasad Neupane

Fabrication of highly porous poly (ɛ-caprolactone) fibers for novel tissue scaffold via water-bath electrospinning

Highly porous fibers were prepared by water-bath electrospinning from pure poly(ɛ-caprolactone) (PCL), and its blends with methoxy poly(ethylene glycol) (MPEG). These fibers were further analyzed by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and gravimetric as well as contact angle measurement. SEM images showed that the fibers diameters as well as pores diameter on the fibers were affected by the weight ratio of MPEG/PCL. DSC and XRD not only revealed suppression of crystallinity of PCL but also indicated the presence of trace amount of MPEG in PCL water-bath collected fibers. The potential use of these hydrophilic porous electrospun fibrous mats as scaffolding materials was evaluated in vitro using mouse osteoblasts (MC3T3-E1) as reference cell lines. Cytotoxicity assessment of the fiber mats indicated that the porous electrospun mat containing trace amount of MPEG was nontoxic to the cell. Cell culture results showed that porous fibrous mats were good in promoting the cell attachment and proliferation. This novel electrospun matrix could be used as potential tissue scaffold material.

High-performance glucose biosensor based on chitosan-glucose oxidase immobilized polypyrrole/Nafion/functionalized multi-walled carbon nanotubes bio-nanohybrid film.

A highly electroactive bio-nanohybrid film of polypyrrole (PPy)-Nafion (Nf)-functionalized multi-walled carbon nanotubes (fMWCNTs) nanocomposite was prepared on the glassy carbon electrode (GCE) by a facile one-step electrochemical polymerization technique followed by chitosan-glucose oxidase (CH-GOx) immobilization on its surface to achieve a high-performance glucose biosensor. The as-fabricated nanohybrid composite provides high surface area for GOx immobilization and thus enhances the enzyme-loading efficiency. The structural characterization revealed that the PPy-Nf-fMWCNTs nanocomposite films were uniformly formed on GCE and after GOx immobilization, the surface porosities of the film were decreased due to enzyme encapsulation inside the bio-nanohybrid composite materials. The electrochemical behavior of the fabricated biosensor was investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and amperometry measurements. The results indicated an excellent catalytic property of bio-nanohybrid film for glucose detection with improved sensitivity of 2860.3μAmM(-1)cm(-2), the linear range up to 4.7mM (R(2)=0.9992), and a low detection limit of 5μM under a signal/noise (S/N) ratio of 3. Furthermore, the resulting biosensor presented reliable selectivity, better long-term stability, good repeatability, reproducibility, and acceptable measurement of glucose concentration in real serum samples. Thus, this fabricated biosensor provides an efficient and highly sensitive platform for glucose sensing and can open up new avenues for clinical applications.

Titania Nanotubes Supported Gelatin Stabilized Gold Nanoparticles for Medical Implants

TiO2 nanotube (TN) arrays produced by electrochemical anodization have been studied extensively in recent years as a new biomaterial for implants, drug delivery systems, immuno-isolation, biosensors, cell growth, bioartifical organs and tissue engineering. A bare TiO2 nanotube implant has many weaknesses when placed in contact with biological systems and surface modification is a possible solution for this problem. The aim of this study is to develop a very simple method for surface modification of TiO2 nanotubes to tailor new interfacial properties important in many biomedical applications. TiO2 nanotubes were fabricated by electrochemical anodization of titanium plate using 70 wt% glycerol in deionized water with 1 wt% NH4F as an electrolyte. The lyophilization method has been applied to impregnate gelatin stabilized gold nanoparticles into the TiO2 nanotubes followed by vacuum drying. This approach for tailoring different surface chemistry of TiO2 nanotubes develops a new platform for biomedical applications.

Synthesis and Morphology of TiO2 Nanotubes by Anodic Oxidation Using Surfactant Based Fluorinated Electrolyte

This study examined the effects of the anodization parameters (both surfactant in electrolyte and applied voltage) on the geometrical dimensions of nanotubes. The nanotube topography, diameter, length and wall thickness were affected by the addition of a surfactant to the electrolyte and applied voltage. As a consequence, TiO2 nanotube arrays with mean tube diameters and wall thicknesses ranging from 65 to 120 nm and 20 to 28 nm, respectively, were obtained. The mean tube diameter was decreased by adding a surfactant to the electrolyte, whereas the length of the tube was increased. The nanotube diameter and length increased linearly with increasing applied potential. At 30 V, the tube to tube spacing was increased by adding a surfactant to the electrolyte. At 40 V, the tubular surface morphology collapsed completely when the electrolyte contained the surfactant but the tube length was not affected in the electrolyte without the surfactant. The TiO2 structure was dependent on the heating conditions; an amorphous and anatase phase was observed at room temperature and 500 � C, respectively. The mean roughness (Ra) of the nanotube surface fabricated in the electrolyte with the surfactant was lower than that without the surfactant.

Influence of heat treatment on morphological changes of nano-structured titanium oxide formed by anodic oxidation of titanium in acidic fluoride solution

TiO(2) nanotube array (TN) on titanium plate was fabricated by using an electrochemical method. The crystal structure and surface morphology of TN array was examined by X-ray diffraction (XRD) and Field Emission Scanning Electronic Microscopy (FE-SEM), respectively. The stability of the nanotube structure and crystal phase transition was studied at different temperatures in dry oxygen ambient. The as-deposited films were found to be amorphous. The tubes crystallized in the anatase phase at a temperature of 450 degrees C. Anatase crystallites formed inside the tubes walls was transformed completely to rutile at 500 degrees C in dry environment. With the heating temperature increased the intensity of rutile peak increased with decrease in reflection from titanium. Intense rutile peak was observed at 600 degrees C. The average pore diameter as calculated from FE-SEM images was 50-100 nm. At higher temperature tubular structure completely collapsed leaving dense rutile crystallites. A model was proposed to explain the formation mechanism of TN fabricated on titanium plate in HF/H(2)SO(4) electrolyte.