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Background: Nanofibers have remarkable characteristics such as large surface to area volume ratios and the ability to be extensively functionalized, and thus have gained attention in research for controlled and localized drug release. Such systems can be applied for instance to control the delivery of cancer drugs. Objective:A series of new theranostic formulations for colorecral cancer (CRC) were prepared in the form of core-shell fibers containing anticancer drugs (5-fluorouracil or ferulic acid) and their cyclodextrin inclusion complexes, together with a gadolinium-based magnetic resonance imaging (MRI) contrast agent. Method:Electrospinning, a simple process for producing ultra-fine fibers with diameters on the micro- to nanometer scale through the application of a strong electrostatic force on a polymer solution, has been applied to produce fibers in this work. The shell of the fibers was formed from Eudragit S100, a pH-sensitive polymer insoluble below pH 7.0, and the drugs were loaded in the core. A detailed characterization and functional performance assays were performed. Results: SEM images show the formation of smooth ribbon-like fibers, with diameters ranging from 1.41 to 5.08 µm, and TEM reveals a clear interface between core and shell compartments. XRD and DSC data confirm the encapsulation of the drug into the cyclodextrin cavity and the formation of amorphous solid dispersions. Drug release from the systems at pH 1 and 7 showed that all the drug loading was released within one hour at pH 1. Conclusion: Based on these results, it is proposed that the relatively low molecular weight drugs were able to diffuse out of the system into the release medium, despite the insolubility of the shell polymer under these conditions. These findings have important implications for the design of electrospun drug delivery systems.