Authors: S-J Yang, F-H Lin, K-C Tsai and M-J Shieh
Affilation: Institute of Biomedical Engineering, National Taiwan University, Taiwan
Pages: 242 - 245
Keywords: photodynamic medicine, 5-Aminolevulinic acid, chitosan, folic acid and nanoparticle
The 5-Aminolevulinic acid (5-ALA) can be converted into protoporphyrin IX (PpIX) that can be utilized as a fluorescent probe for tumor detection. In this study, folic acid was conjugated on chitosan molecules via covalent bond for specific target and then 5-ALA was encapsulated in chitosan nanoparticles to prevent the uptake by E. coli. We mixed chitosan with sodium tripolyphosphate (STPP) to prepare chitosan nanoparticles (CN) by ionic gelation method. Then CN were loaded with 5-ALA (CNA) by the same method. The size and zeta potential of CN and CNA were measured by transmission electron microscope and zetasizer, respectively. CN and CNA were both at the range of 90-110 nm in size and the loading efficiency of 5-ALA in CNA was in the range of 80%-90% depending on the concentration of 5-ALA prepared. Bioassy results of CNA for HT-29 colon cancer cell uptake revealed that HT-29 colon cancer cells could uptake CAN and the content of PpIX converted from 5-ALA in cell body depended on the ratio of folic acid to amino groups on chitosan. This result implied that CNA could exclude the influence of normal flora inside the gut and serves as an ideal vector of colon-specific drug delivery system. According to this concept, we designed a novel photodynamic detection system to enhance the accuracy of endoscopic diagnosis for early colorectal cancer.