A new type of pH-responsive coordination polymer sphere as a vehicle for targeted anticancer drug delivery and sustained release

A new type of coordination polymer sphere prepared by combining 1,1'-(1,4-butanediyl)bis(imidazole) (bbi) and ferrous ions has been demonstrated as a targeted delivery system for in situ encapsulating anticancer drugs. These stable coordination polymer spheres can be fabricated simply by a deposition method. Drugs, doxorubicin hydrochloride (DOX·HCl) for example, can be easily in situ encapsulated by simply mixing the drug with bbi ligand through the deposition method and results in a high drug loading efficiency up to 98% and a drug loading content of nearly 40%, which is remarkably high for not only metal-organic but also other materials. A noticeable feature of the drug loaded coordination polymer spheres is that they show sustainable drug release for several days due to their superior stability, and are sensitive to external pH owing to the coordination bonds. The drug can be released faster in mild acidic conditions in comparison to physiological acidity. By conjugating folic acid to the surface of the coordination polymer spheres, the vehicles can be taken up selectively by cancer cells through cell surface receptor-mediated mechanisms. Cell viability experiments with HeLla cells demonstrated the low toxicity of the delivery vehicles and the good anticancer efficacy of the drug-loaded coordination polymer spheres.