Curcumin-Loaded Ligand-Conjugated Chitosan Nanoparticles: A Comparative Study of Folic Acid, Phenylalanine, and...

Colorectal cancer therapy requires drug delivery systems that improve treatment efficacy and minimize systemic toxicity. In this study, chitosan-based nanoparticles were fabricated and functionalized with folic acid (FA), phenylalanine (PA), and butyric acid (BA) to enhance the delivery of curcumin to Caco-2 cancer cells. The nanoparticles were prepared using an ionic gelation method, and their physicochemical properties, cellular uptake efficiency, and cytotoxicity-including safety evaluation against normal HIEC-6 cells-were investigated. Results showed that ligand conjugation significantly influenced the physicochemical properties of the nanoparticles. CRFANP (FA-modified) exhibited the largest particle size (263.5 nm) due to its rigid aromatic structure, while CRPANP (PA-modified) showed an intermediate size (138.0 nm) and the lowest surface charge (15.59 mV). In contrast, CRBANP (BA-modified) presented the smallest particle size (128.2 nm) and the highest positive surface charge (23.27 mV). These distinct physicochemical properties directly influenced their cellular interactions; CRBANP and CRFANP showed higher uptake than CRPANP, with CRBANP yielding the maximum accumulation of curcumin in Caco-2 (21.92 nM/mg protein) and HT-29 cells (22.09 nM/mg protein). Correlating with the uptake data, cytotoxicity assays revealed that CRBANP was the most potent formulation, exhibiting the lowest IC₅₀ of 1.30 µM in Caco-2 cells, which was significantly lower than that of CRFANP (3.49 µM) and CRPANP (7.40 µM), while demonstrating high selectivity against Caco-2 cells with an SI of 46.5 and no apparent toxicity toward normal HIEC-6 cells. This enhanced efficacy is attributed to the synergistic action of butyric acid as a histone deacetylase inhibitor (HDACi), which complements curcumin's anticancer activity. These findings indicate that integrating butyric acid into chitosan nanoparticles provides an effective and selective strategy for targeted colorectal cancer therapy.