The Research Of The Novel Thermo-sensitive Biomedical Materials

To improve the effectiveness of drug treatment, the targeted drug carriers have been become a hot research topic. The principle is to release drugs in lesion area by using its pH, magnetic characteristics, et al. While temperature sensitive carriers and poly(N-isopropylacrylamide) (PNIPAM) are most. In the present targeting speed to release medicine is not quick for biomaterials, to prepare different structure of microparticles and gels by using the characteristic of temperature sensitive materials of positive and negative type gels as the research system. Firstly, a novel structure was prepared in a three-step process by a method of sequential synthesis because speed of linear poly(N-isopropylacrylamide) is faster than that with the crossing linking. Secondly, a novel release system with one material being in the center and another being in around was assembled by breaking the traditional structure with interpenetrating polymer network (IPN) of polyacrylamide/polyacrylic acid (PAAM/PAAC) and keeping their mechanisms of phase change. Finally, poly (N-isopropylacrylamide) as the shell of nanocapsules was prepared by using the difference of solubility of hydrophobic polymer in organic solvent and water. Transmission electron microscopy was used to detect structure of the gels and microspheres and NaCl was used as the release drugs to display its performance.1. Sandwich-typed hydrogels, which is featured with both ends of linear poly(N-isopropylacrylamide) (PNIPAM) chains being grafted onto cross-linked PNIPAM chains have been prepred. Effect of N-isopropylacrylamide concentration on swelling ratio, temperature-response speed and their controlled-release characteristics was investigated. The results are following:①All phase changes occur at 33℃and the color change from white to translucent.②The proposed hydrogel displays faster and hydration/dehydration dynamic response to temperature cycling owing to linear PNIPAM chains to form big-hole structure.③The release test shows the gels with fast temperature-response speed when temperature is from low to high temperature.2. PAAM and PAAC microgels and columns were prepared respectively and installed under different methods. Their temperature sensitivity, morphology, swelling behavior were studied, the results show that:①The phase change range of novel system narrower according to traditional system with IPN structure.②The proposed system has good sensitive at temperature 25℃-30℃.③The release speed at 15℃is lower than that at 30℃.3. Nanoparticles with polystyrene core/poly (N-isopropylacrylamide) shell were prepared by using firstborn microcrystallization method. Effect of hydrophobic poly styrene chains on formation was studied. The results display its core/shell structure is very obvious and the diameter increase with increasing reaction time of polystyrene.