Figure 5.

A schematic representing the click coupling of IONPs functionalised with azide (red) groups and those functionalised with alkyne groups (blue). These particles expose azide/alkyne groups in the prescence of matrix metalloproteinase (MMP) enzymes, facilitating a click reaction mediated particle coupling. The effect on the T₂ relaxation can be seen alongside both the individual IONPs (top) and the nanocluster (bottom). The particles also contain tumour specific peptide ligands and are functionalised with PEG to improve biocompatibility in vivo. Reprinted with permission from the authors of [52]. Copyright (2014), with permission from John Wiley and Sons.