One of the things I enjoy doing is making links between the different topics in Chemistry and treating Chemistry holistically rather than taking a modular approach. A nice example which encompasses nanotechnology, catalysis, organic chemistry, acids and bases, nucleic acids and medicines and drugs has just been reported.

One of the most common drugs administered as part of chemotherapy is doxorubicin. This compound is an antibiotic which was first obtained by mutating a strain of the bacterium Streptomyces peucetius. It functions by binding to DNA and preventing nucleic acids from replicating and thus preventing cell division.  

It is known as an anthracycline and has the chemical formula:

You could ask students to identify the functional groups in a molecule of doxorubicin. These would include ketone, hydroxyl (alcohol), ether and amine as well as aromatic rings. It will have some polarity due to the many –OH groups but it is administered in an ionic form as its hydrochloride salt (the amine becomes protonated by the hydrochloric acid) to increase its solubility in an aqueous medium.

Doxorubicin is given to treat many different types of cancer including cancer of the breast, ovaries, lymph glands and the thyroid. There are however several problems with administering doxorubicin. It is required in relatively large doses and can cause quite serious side-effects such as cardiac problems as well as nausea and hair loss. This relates well to the benefit to risk ratio and to the concept of therapeutic window in Option D.

A more efficient way of delivering much smaller doses of doxorubicin has been developed by a team at Northwestern University. In an article published in Science Translational Medicine they report how they have reversibly bound doxorubicin to nanodiamonds.  The nanodiamonds are thought to act as a surface catalyst and the doxorubicin remains in the body ten times longer. Currently this has only been tested in mice but the doxorubicin has been shown to be much more effective when it is delivered in this way and less toxic. Nanodiamonds have the characteristic diamond structure but are only 2 to 20 nanometres in diameter. They are found in the detonation products from explosions and are also present in some meteorites. They are being increasingly used in research in living systems as they show antioxidant and anti-inflammatory properties. It is thought that certain biologically important molecules interact with the surface of the nanodiamonds and it is this which led to the research with doxorubicin.