Bismuth citrate as metal-organic framework for drug delivery

Abstract

Colloidal bismuth subcitrate (CBS) was initially an effective drug in treating H. pylori. infection with minimal toxicity.1 It shows a three-dimensional anionic framework composing of bismuth dimeric units,2 and diverse structures are also observed with different cations. Therefore, CBS is found to be a flexible, porous and low cytotoxic material which could be a potential metal-organic framework (MOF) for drug delivery. In this study, we elucidate the MOF concept by co-crystallization of CBS with anionic small molecule spermidine. Our crystallography data reveal the co-crystallization in two types of crystals: sheet-like and rod-like colorless crystals, which have not reported before. The most extensive channel of Sper@CBS-MOF can be found on plane (110) with the dimension of 25.0 × 13.4 Å. It is found that spermidine acting as a guest molecule, can be diffused into the MOF structure and docked inside the channel via electrostatic interactions. CBS-MOF is subsequently characterized in terms of morphology, thermal stability and cytotoxicity. CBS-MOF exhibits excellent drug loading ability using cationic commercial drugs metformin and isoniazid as an example.