Preparation And Application Study Of The Temperature Sensitive Composite Nanofibers Based On PNIPAAm

Drugs of pharmaceutical sustained controlled release agents can be released in accordance with the design of dose in a specified period of time with a desired drug concentration in human body. Traditional pharmaceutical agents have many disadvantages, such as frequent drug administration, high side effects and low drug utilization. Sustained controlled drug release agent overcomes the disadvantages of conventional pharmaceutical formulations, and it reduces the side effects and the frequency of dosing, and also increases the availability of drugs. Nanofibers produced by electrospinning technology have many advantages, such as high specific surface area,small-diameter, high porosity and good mechanical properties. They are widely used as biosensors,tissue engineering scaffolds, wound dressing and drug carriers. Among many temperature-sensitive polymers, Poly(N-isopropylacrylamide)(PNIPAAm) is the most representative one. The LCST value of PNIPAAm is about 32℃, which is very close to human body temperature. PNIPAAm is a kind of water-soluble polymers and has good biocompatibility.This paper intended to prepare a new type of temperature-sensitive drug delivery system based on PNIPAAm. The main contents are as follows:(1) Nanofibers of poly(N-isopropylacrylamide)(PNIPAAm), ethylcellulose(EC) and a blend of both were successfully fabricated by electrospinning. Characterizations are as follows: scanning electron microscopy(SEM), transmission electron microscope(TEM), fourier transform infrared(FTIR), X-ray diffraction(XRD), the water contact angle(CA) and molecular modelling. The results show that when the mass ratio of PNIPAAm to EC is 1: 2, the morphology of nanofiber is optimal. The morphology of nanofibers is smooth, uniform, cylindrical and has no beaded structures. PNIPAAm and EC can dispersed in an amorphous state in nanofibers, and there areintermolecular interaction forces between them(van der Waals forces and hydrogen bonding).Composite nanofibers are temperature sensitive and have good biocompatibility, which are suitable for using as thermo-sensitive drug carriers.(2) Drug loaded nanofibers of poly(N-isopropylacrylamide)(PNIPAAm), ethylcellulose(EC),KET and a blend of them were successfully fabricated by electrospinning. Then a series of properties of nanofibers were characterized by using the above characterization methods. The results suggest that the morphology of different mass ratios of PNIPAAm to EC is good. KET has been converted to the amorphous physical state from crystalline form by electrospinning. The addition of KET does not affect the temperature sensitivity and cytotoxicity of the nanofibers.Drug loaded nanofibers are also temperature sensitive and have good biocompatibility.(3) The different mass ratios of PNIPAAm to EC of PNIPAAm/EC/KET drug loaded composite nanofibers were taken for in vitro drug release experiments under 25℃ and 37℃. The results show that the blend nanofibers combine the advantages of the two polymers, possessing both thermosensitive and sustained release properties. When the temperature is 25 ℃, the drug release rate reduced with the increasing content of EC. When the temperature is 37 ℃, the drug release rate increased with the increasing content of EC. The temperature sensitive property of drug loaded nanofibers increased with the increasing content of PNIIPAAm. When the mass ratio of PNIPAAm to EC is 1:2, PNIPAAm/EC blend fibers can be used for temperature sensitive sustained controlled drug carriers.