-Sulfonatocalix[4]arene turns peptide aggregates into an efficient cell-penetrating peptide.

A novel cell-penetrating peptide (CPP) called -YR, with as a fluorescent probe, was developed. Initially, we aimed to use Y as a supramolecular host for water-insoluble drugs, with R driving the complex into cells. However, an unexpected hurdle was discovered; the peptide self-assembled into amorphous aggregates, rendering it ineffective for our intended purpose.