Introductionand purpose: Site-specific delivery systems are highly advantageous for local cancer treatment as they allow a more significant delivery of the drug to the tumor with minimal systemic side effects. Furthermore, combination therapy is a promising approach that attracts more attention in cancer treatment due to its synergistic effects. In this work, nanosponges immobilized polymeric microbeads for colon-specific delivery systems were developed for a drug combination of 5-fluorouracil and curcumin to treat colorectal cancer. MethodsSodium alginate and low molecular chitosan polymers were used to create microbead-based formulations containing curcumin-encapsulated nanosponges and 5-fluorouracil. To improve curcumin's low solubility, Diphynylacarbonate (DPC) hyper cross-linking of β-CD was used to create curcumin-loaded β-CD nanosponges that further incorporated in the polymeric microbeads along with free 5-fluorouracil. ResultsThe optimized microbeads were spherical with a mean particle size of 1.1 ± 0.05 mm. The produced beads were subsequently coated with a multilayer coating of ethyl cellulose and Eudragit S100 polymers, which functioned as pH-dependent and time-dependent coatings to ensure drug delivery to the colon. The developed formulation (Coated MB5) showed controlled release of the drug and sustained cytotoxic effect. The release profiles of 5-fluorouracil and curcumin from Coated MB5 were best described by zero-order followed by first-order release functions. About 66.4 % of 5-FU and 73.1 % of curcumin were released for 24 h. In vivo roentgenographic evaluation in a rabbit model indicated that the optimized coated microbeads successfully reached the colon 7–9 h after administration. ConclusionsAs a prospective colon-specific drug delivery system, a successful formulation (Coated MB5) was developed for the combined delivery of 5-fluorouracil and curcumin. More in vivo studies are needed to demonstrate the therapeutic efficacy of optimized formulations and their potential to improve colorectal cancer therapy by providing a more targeted administration of combination medicines with fewer undesirable side effects.