A porous silica material, doped with calcium, gives targeted delivery of a new platinum anticancer drug.

Platinum-based cancer treatments, such as cisplatin, are well known, however, their use can be limited by their severe side effects. These side effects can be minimised if the platinum compounds accumulate only in the target organs or cells. One way of achieving this is to use carrier ligands that are designed to promote specific accumulation.

Giovanni Natile at the University of Bari, Italy, and co-workers designed a novel platinum complex with geminal bisphosphonate ligands. These ligands are attracted to calcium ions, meaning they could be used to specifically target bone. 

The researchers loaded their complex into a silica xerogel, with the aim of using the material as bone fillers, acting as a bone substitute while slowly releasing the platinum drug at the site of the tumour.  

Silica xerogels - highly porous dried out gels - are biocompatible and slowly erode after implantation. They have been used previously for the slow release of cisplatin.

Using a normal silica xerogel with Natile's complex, however, meant that the drug was released in an inactive form. So, Natile's team used calcium-doped silica xerogels. The calcium ions acted as anchors, binding the bisphosphonate ligand and releasing the active platinum drug.  

Natile hopes that the platinum released will be sufficient to give therapeutic activity at the site of the implant, while being too low to cause undesired toxic effects on neighbouring tissues. 

Norberto Roveri an expert in functionalised inorganic matrices at the University of Bologna, Italy, welcomed the research. 'The combination of 'intelligent' drug design and strategic formulation of multi-functional nanostructured inorganic materials to be used as bone filler after surgery provides novel solutions for the local treatment of bone tumours,' he said. 

Ian Gray