In Situ Heparan Sulfate-Induced Peptide Self-Assembly to Overcome the Cell Surface Glycocalyx Barrier for Cancer Treatment

Heparan sulfate (HS) is a major component of cell surface glycocalyx with extensive negative charges and plays a protective role by preventing toxins, including small molecule drugs and anticancer cationic lytic peptides (ACLPs), from cells. However, this effect may compromise the treatment efficiency of anticancer drugs. To overcome the impedance of cancer cell glycocalyx, an HS-targeting ACLP PTP-7z was designed by fusion of an ACLP and a Zn²⁺-binding HS-targeting peptide. Upon Zn²⁺ ion binding, PTP-7z could self-assemble into uniform nanoparticles and show improved serum stability and reduced hemolysis, which enable it to self-deliver to tumor sites. The peptide PTP-7z showed a pH- and Zn²⁺ ion-dependent HS-binding ability, which triggers the HS-induced in situ self-assembling on the cancer cell surface in the acidic tumor microenvironment (TME). The self-assembled PTP-7z can overcome the impedance of cell glycocalyx by either disrupting cell membranes or translocating into cells through endocytosis and inducing cell apoptosis. Moreover, PTP-7z can also inhibit cancer cell migration. These results proved that HS-responsive in situ self-assembling is a practical strategy to overcome the cancer cell glycocalyx barrier for ACLPs and could be extended to the design of other peptide drugs to promote their in vivo application.