Folic Acid-Conjugated Chitosan Nanoparticles Enhanced Protoporphyrin IX Accumulation in Colorectal Cancer Cells

Abstract

Folic acid can be covalently conjugated to chitosan molecules via its gamma-carboxyl moiety and thus retain a high affinity for colorectal cancer cells bearing folate receptor overexpression. Colorectal cancer is one of the leading causes of malignant death and often goes undetected with current colonoscopy practices. Improved methods of detecting dysplasia and tumors during colonoscopy will improve mortality. A folic acid conjugated chitosan nanoparticle as a suitable vehicle for carrying 5-aminolaevulinic acid (5-ALA) is developed to enhance the detection of colorectal cancer cells in vivo after a short-term uptake period. Chitosan can be successfully conjugated with folic acid to produce folic acid-chitosan conjugate, which is then loaded with 5-ALA to create nanoparticles (fCNA). The loading efficiency of 5-ALA in fCNA particles and the z-average diameter were in the range 35-40% and 100 nm, respectively. The zeta-potential for fCNA was 20 mV, enough to keep the nanoparticle stable without aggregation. The fCNA is then incubated with HT29 and Caco-2 colorectal cancer cell lines overexpressing folate receptor on the surface of the cell membrane to determine the rate of accumulation of protoporphyrin IX (PpIX). The results show that fCNA can be taken up more easily by HT29 and Caco-2 cell lines after short-term uptake period, most likely via receptor-mediated endocytosis, and the PpIX accumulates in cancer cells as a function of the folate receptor expression and the folic acid modification. Therefore, the folic acid-chitosan conjugate appears to be an ideal vector for colorectal-specific delivery of 5-ALA for fluorescent endoscopic detection.