Nanofiber fabrication in a temperature and humidity controlled environment for improved fibre consistency

To fabricate nanofibers with reproducible characteristics, an important demand for many applications, the effect of controlled atmospheric conditions on resulting electrospun cellulose acetate (CA) nanofibers was evaluated for temperature ranging 17.5 - 35°C and relative humidity ranging 20% - 70%. With the potential application of nanofibers in many industries, especially membrane and filter fabrication, their reproducible production must be established to ensure commercially viability.
Cellulose acetate (CA) solution (0.2 g/ml) in a solvent mixture of acetone/DMF/ethanol (2:2:1) was electrospun into nonwoven fibre mesh with the fibre diameter ranging from 150nm to 1µm.
The resulting nanofibers were observed and analyzed by scanning electron microscopy (SEM), showing a correlation of reducing average fibre diameter with increasing atmospheric temperature. A less pronounced correlation was seen with changes in relative humidity regarding fibre diameter, though it was shown that increased humidity reduced the effect of fibre beading yielding a more consistent, and therefore better quality of fibre fabrication.
Differential scanning calorimetry (DSC) studies observed lower melt enthalpies for finer CA nanofibers in the first heating cycle confirming the results gained from SEM analysis. From the conditions that were explored in this study the temperature and humidity that gave the most suitable fibre mats for a membrane purpose were 25.0°C and 50%RH due to the highest level of fibre diameter uniformity, the lowest level of beading while maintaining a low fibre diameter for increased surface area and increased pore size homogeneity. This study has highlighted the requirement to control the atmospheric conditions during the electrospinning process in order to fabricate reproducible fibre mats

Two-stage optimization process for formulation of chitosan microspheres

The objective of the present study was to optimize the concentration of a chitosan solution, stirring speed, and concentration of drug having different aqueous solubility for the formulation of chitosan microspheres. Chitosan microspheres (unloaded and drug loaded) were prepared by the chemical denaturation method and were subjected to measurement of morphology, mean particle size, particle size distribution, percentage drug entrapment (PDE), drug loading, and drug release (in vitro). Morphology of the microspheres was dependent on the level of independent process parameters. While mean particle size of unloaded microspheres was found to undergo significant change with each increase in concentration of chitosan solution, the stirring rate was found to have a significant effect only at the lower level (ie, 2000 to 3000 rpm). Of importance, spherical unloaded micropheres were also obtained with a chitosan solution of concentration less than 1 mg/mL. Segregated unloaded microspheres with particle size in the range of 7 to 15 μm and mean particle size of 12.68 μm were obtained in the batch prepared by using a chitosan solution of 2 mg/mL concentration and stirring speed of 3000 rpm. The highest drug load (μg drug/mg microspheres) was 50.63 and 13.84 for microspheres containing 5-fluorouracil and methotrexate, respectively. While the release of 5-fluorouracil followed Higuchi's square-root model, methotrexate released more showly with a combination of first-order kinetics and Higuchi's square-root model. The formation of chitosan microspheres is helped by the use of differential stirring. While an increase in the concentration of water-soluble drug may help to increase PDE and drug load over a large concentration range, the effect is limited in case of water insoluble drugs