Colorectal cancer cell detection by 5-aminolaevulinic acid-loaded chitosan nano-particles

Colorectal cancer is one of the leading causes of malignant death in Taiwan because it often remains undetected until later stages of the disease. In this study, we designed an oral form nano-particle to encapsulate 5-aminolaevulinic acid (5-ALA) to improve the detection of colorectal cancer cells in vivo. The nano-particle should escape from bacteria uptake in the gastrointestinal tract which seriously interferes the results of endoscopic observation. In this study, chitosan was mixed with sodium tripolyphosphate (STPP) and 5-ALA to prepare chitosan nano-particles (CN) and 5-ALA loaded chitosan nano-particles (CNA) by adding different pH values and concentrations of 5-ALA solution. The average particle size and zeta-potential of CN and CNA were measured by the Zetasizer-3000. The results revealed that particle size with different zeta-potential could be manipulated just by 5-ALA concentrations and pH values. CNA particles prepared at pH 7.4 and pH 9 of 5-ALA solutions with a concentration higher than 0.5 mg/ml showed a promising loading efficiency of up to 75% and an optimum average particle size of 100 nm. The zeta-potential for CNA was over 30 mV that kept the nano-particle stable without aggregation when stored in suspension solution. Fluorescence microscope examination showed that CNA could be engulfed by Caco-2 colon cancer cells but showed no evidence of being taken up by Escherichia coli. This result implies that CNA could exclude the influence of normal flora inside the gut and serves as an adequate tool for fluorescent endoscopic detection of colorectal cancer cells in vivo.