Electrospun Poly(N-isopropylacrylamide)/Ethyl Cellulose Nanofibers as Thermoresponsive Drug Delivery Systems

Fibers of poly(N-isopropylacrylamide) (PNIPAAm), ethyl cellulose (EC), and a blend of both were successfully fabricated by electrospinning. Analogous drug-loaded fibers were prepared loaded with ketoprofen (KET). Scanning and transmission electron microscopy showed that the fibers were largely smooth and cylindrical, with no phase separation observed. The addition of KET to the spinning solutions did not affect the morphology of resultant fibers, and no drug particles could be observed to separate from the polymer matrix. X-ray diffraction demonstrated that the drug was present in the amorphous physical form in the fiber matrix. There are significant intermolecular interactions between KET and polymers, as evidenced by IR spectroscopy and molecular modeling. Water contact angle measurements proved that the PNIPAAm and PNIPAAm/EC fibers switched from being hydrophilic to hydrophobic when the temperature was increased through the lower critical solution temperature of 32°C. In vitro drug release studies found that the PNIPAAm/EC blend nanofibers were able to synergistically combine the properties of the 2 polymers, giving temperature-sensitive systems with sustained release properties. In addition, they were established to be nontoxic and suitable for cell growth. This study demonstrates that electrospun-blend PNIPAAm/EC fibers comprise effective and biocompatible materials for drug delivery systems and tissue engineering.