Three of the block copolymers (5a4/5c1/5c2) were used for the development of peptide crosslinked nanogels. The peptide cross-linker was prepared by solid phase peptide synthesis inserting an azido-lysine residue at both the C-and N-termini according to literature procedures. An MMP-7-cleavable sequence (Figure ) was installed into the peptide backbone enabling enzyme-triggered nanogel degradation. LC-MS spectra of the functionalised MMP-7-cleavable peptide after purification is shown in Figure . In order to prepare the cross-linked nanogels, we developed a two-step protocol. First, the formation of self-assembled nanogels was induced by heating the block copolymer solution to 45 °C (above the LCST). A solution of the cross-linker was then added, together with small amounts of CuSO4•5H2O and (+)-sodium-L-ascorbate, leading to covalent crosslinking; the mixture was subsequently purified by size exclusion chromatography. Upon cooling below the LCST, our nanogels therefore retained their structure, despite the solubilisation of the polymer chains.