Chitosan/β-cyclodextrin nanocarriers enhance 5-fluorouracil efficacy against colorectal cancer via pH-responsive...

Globally, colorectal cancer continues to be a major cause of cancer-related death. Clinical application of 5‑fluorouracil (5‑FU) is constrained by reduced bioavailability and dose‑limiting toxicity. To overcome these restrictions, a ternary drug delivery system was developed in this study. Chitosan and β‑cyclodextrin were physically assembled into a pseudopolyrotaxane complex, and 5‑FU was incorporated by solvent evaporation to form a solid dispersion. The resulting nanocomposite had a mean hydrodynamic diameter of 187 nm and a zeta potential of + 32.5 mV. Fourier transform infrared spectroscopy revealed peak shifts consistent with non‑covalent interactions. X‑ray diffraction confirmed amorphization of 5‑FU within the formulation. The ternary system released 5‑FU more rapidly at pH 5.5 than at pH 7.4. In HCT‑116 colorectal cancer cells, the 5‑FU/chitosan/β‑cyclodextrin formulation showed an IC₅₀ of 16.5 µM, compared with 42.5 µM for free 5‑FU and 27.5 µM for the binary 5‑FU/β‑cyclodextrin complex. Gene expression analysis indicated upregulation of P53 and Caspase‑3 and downregulation of BCL2 and VEGF. A complementary in silico analysis of 5-FU-responsive genes (from public dataset GSE183977) identified a protein‑protein interaction network enriched in apoptosis and cell‑cycle pathways, with IL6, MYC, EGR1, and ATF3 as central hub genes. The obtained results show that incorporation of 5‑FU into a chitosan/β‑cyclodextrin matrix improves its activity against colorectal cancer cells. This effect is attributed to enhanced solubility, pH‑responsive release, and modulation of apoptotic and angiogenic pathways.