PH-responsive hollow core zeolitic-imidazolate framework-8 as an effective drug carrier of 5-fluorouracil

Abstract

To enhance the porosity and accessibility, a novel drug carrier, the hollow core zeolitic-imidazolate framework-8 (HZIF-8), is designed using polystyrene as a hard template to sequentially load and release 5-fluorouracil (FU). HZIF-8 is signified by a large surface area and pore volume, reaching 1727.1 m2/g and 0.99 cm3/g, respectively. The obtained HZIF-8 exhibits rhombic dodecahedron morphology with a uniform particle size of 450 nm. The integrated hollow core is observed at ca. 180 nm. Evaluation of the FU encapsulation behavior in HZIF-8 nanospheres is demonstrated via the adsorption kinetics, isotherm, and thermodynamic studies. The maximum FU uptake is monitored at 40 °C with the loading capacity of 161.9 mg/g. This study suggests that the FU uptake follows the pseudo-second-order law and multilayer mechanism. The governing mechanism is chemical binding in its first layer and physical interaction in the upper layers. The release study of FU from FU-loaded HZIF-8 shows that the cumulative release at pH 5.5 (92.03%) is four times higher than that at pH 7.4 (23.31%), indicating a stimulus-responsive release mechanism where pH is required as an internal stimulus factor.