Evolution of Surface Nanopores in Pressurised Gyrospun Polymeric Microfibers.

The selection of a solvent or solvent system and the ensuing polymer⁻solvent interactions are crucial factors affecting the preparation of fibers with multiple morphologies. A range of poly(methylmethacrylate) fibers were prepared by pressurised gyration using acetone, chloroform, N,N-dimethylformamide (DMF), ethyl acetate and dichloromethane as solvents. It was found that microscale fibers with surface nanopores were formed when using chloroform, ethyl acetate and dichloromethane and poreless fibers were formed when using acetone and DMF as the solvent. These observations are explained on the basis of the physical properties of the solvents and mechanisms of pore formation. The formation of porous fibers is caused by many solvent properties such as volatility, solubility parameters, vapour pressure and surface tension. Cross-sectional images show that the nanopores are only on the surface of the fibers and they were not inter-connected. Further, the results show that fibers with desired nanopores (40⁻400 nm) can be prepared by carefully selecting the solvent and applied pressure in the gyration process.

5-Fluorouracil loaded Eudragit fibers prepared by electrospinning.

A series of 5-fluorouracil (5-FU) loaded core/shell electrospun fibers is reported. The fibers have shells made of Eudragit S100 (ES-100), and drug-loaded cores comprising poly(vinylpyrrolidone), ethyl cellulose, ES-100, or drug alone. Monolithic 5-FU loaded ES-100 fibers were also prepared for comparison. Electron microscopy showed all the fibers to have smooth cylindrical shapes, and clear core-shell structures were visible for all samples except the monolithic fibers. 5-FU was present in the amorphous physical form in all the materials prepared. Dissolution studies showed that the ES-100 shell was not able to prevent drug release at pH 1.0, even though the polymer is completely insoluble at this pH: around 30-80% of the maximum drug release was reached after 2h immersion at pH 1.0. These observations are ascribed to the low molecular weight of 5-FU permitting it to diffuse through pores in the ES-100 coating, and the relatively high acid solubility of the drug providing a thermodynamic impetus for this to happen. In addition, the fibers were observed to be broken or merged following 2h at pH 1.0, giving additional escape routes for the 5-FU.

Fast dissolving paracetamol/caffeine nanofibers prepared by electrospinning.

A series of polyvinylpyrrolidone fibers loaded with paracetamol (PCM) and caffeine (CAF) was fabricated by electrospinning and explored as potential oral fast-dissolving films. The fibers take the form of uniform cylinders with smooth surfaces, and contain the drugs in the amorphous form. Drug-polymer intermolecular interactions were evidenced by infrared spectroscopy and molecular modeling. The properties of the fiber mats were found to be highly appropriate for the preparation of oral fast dissolving films: their thickness is around 120-130 µm, and the pH after dissolution in deionized water lies in the range of 6.7-7.2. Except at the highest drug loading, the folding endurance of the fibers was found to be >20 times. A flavoring agent can easily be incorporated into the formulation. The fiber mats are all seen to disintegrate completely within 0.5s when added to simulated saliva solution. They release their drug cargo within around 150s in a dissolution test, and to undergo much more rapid dissolution than is seen for the pure drugs. The data reported herein clearly demonstrate that electrospun PCM/CAF fibers comprise excellent candidates for oral fast-dissolving films, which could be particularly useful for children and patients with swallowing difficulties.