pH-sensitive carboxymethyl starch-gelatin coated COF/5-Fu for colon cancer therapy

Owing to the desired structure, recently covalent organic frameworks (COFs) have emerged as one of the more efficient drug-loading platforms. Therefore, in the current study, we constructed COF with a spherical structure as a platform for 5-fluorouracil (5-Fu) loading. The as-synthesized COF showed a larger pore size (∼30.42 nm) than the 5-Fu dimension and a surface area of 230.58 m2/g. With these advantages, the 5-Fu loading percentage on COFs was achieved at ∼93.33 % (COF/5-Fu). However, their imine bond is relatively unstable in harsh acidic conditions. Hence, to prevent the fast drug release at pH 1.2, and considering that the key objective of the frontier work was to construct an oral site-definite controlled drug delivery system, there is an urgent and strong need to cap COF/5-Fu into carboxymethyl starch-gelatin (CMS-Gel) coat (COF/5-Fu@CMS-Gel). Drug release tests showed that the loaded 5-Fu was released highly at pH 7.4, but only 14.11 % of 5-Fu releases occurred at pH 1.2. The structural analyses supported the hypothesis of the successful formation of the prepared samples. The MTT assay showed the biocompatible nature of neat COF@CMS-Gel and its cytotoxic potential after drug loading. All these good properties can guarantee that the COF/5-Fu@CMS-Gel is promising for controlled colon drug delivery.