A 4‐Arm PEG‐Thiodepsipeptide Precursor Enables Gelatinase‐Promoted Hydrogel Formation

Abstract

AbstractIn situ hydrogelation of injectable precursors upon biological stimulus is relevant to generate hydrogels under mild conditions and, potentially, at a biological side of interest. Here, it is shown that hydrolytic enzymes can be used to initiate the formation of covalent hydrogel networks, realizing a cleavage‐leading‐to‐gelation strategy. For this purpose, a two‐component system is used, consisting of a 4‐arm polyethylene glycol‐thiodepsipeptide conjugate, PEG4TDPo containing the matrix metalloproteinases MMP‐2‐ and MMP‐9‐cleavable Ac‐Pro‐Leu‐Gly#SLeu‐Leu‐Gly‐ thiodepsipeptide sequence releasing a thiol upon hydrolysis, and a maleimide functionalized 4‐armed PEG (PEG4MAL). PEG4TDPo is synthesized in a PEG‐functionalization protocol involving convergent and divergent synthetic steps without the need for rigorous purification procedures. In a fluorometric assay, it is shown that the construct is in fact cleaved by both investigated MMPs. PEG4TDPo in the presence of 10 wt.% PEG4MAL formed hydrogels upon addition of MMP‐2 or ‐9 with average gelation times of 28 and 40 min, respectively, as is investigated by rheology. The much faster gelation times compared to the enzyme‐free system showed the specific input of the enzymatic reactions. The MMP‐assisted activation and crosslinking strategy can potentially become useful by targeting tissues showing an increased expression of MMPs, such as cancers, or to detect MMPs.