To develop relatively green and ecofriendly smart vehicles for colon-specific drug delivery, carboxymethyl cellulose (CMC) and chitosan (CS) pH-sensitive biopolymers were used in this study. To overcome the weaknesses of CMC carriers, such as poor mechanical performance and an explosive drug release, zinc oxide (ZnO) nanoparticles were incorporated into CMC beads and then coated with a CS layer via a self-assembly technique to form core-shell polyelectrolyte complexes. An anticancer drug, 5-fluorouracil (5-FU), used as a model drug, was loaded into ZnO/CMC/CS bio-nanocomposite beads. Fourier transform infrared spectroscopy, scanning and transmission electron microscopy, and thermogravimetric analysis were used to characterize the chemical structure, morphological changes, and thermal properties of the developed drug carrier, respectively. By studying their swelling and in vitro 5-FU release profiles under simulated gastrointestinal conditions, the pH sensitivity of the developed bio-nanocomposite hydrogel beads could be investigated. The obtained beads with reduced porosity could effectively encapsulate 5-FU and showed self-sustained release behavior depending on the concentrations of CMC, CS, and ZnO nanoparticles. The developed beads also demonstrated a capacity for biodegradation. The results indicated that the ZnO/CMC/CS bio-nanocomposite beads exhibited pH-sensitivity and could be applied efficiently as biodegradable carriers for colon-specific 5-FU delivery.