Targeted drug delivery uses properties of tumour cells and microenvironment, and increases the concentration of drugs in cancer cells. This research aimed at assembling a liposome with cystatin C, capable of active targeting and encapsulating cytotoxic drugs. Cystatin C is an inhibitor of cathepsins. Cathepsin B was found to be a liable target. Cystatin C’s DNA was mutated, substituting in cysteine to introduce a free -SH, capable of conjugation with a liposome. It was then expressed by E. Coli and isolated from the cell lysate. It was successfully tested for its inhibitory activity. PEG liposomes were conjugated with cystatin C and tested. The inhibitiory activity was not confirmed. -S-S- reduction and cystatin C dimerisation can and will be further investigated to confirm this activity.