Micelle-like Nanoassemblies of Short Peptides Create Antimicrobial Selectivity in a Conventional Antifungal Drug

The discovery of novel antibacterial drugs against infectious diseases has decreased over the past few decades because of their poor cost performance. In this study, we report that the nanoassembly of a short-peptide hydrogelator (P1) endowed novel antifungal selectivity to a conventional antifungal drug, amphotericin B (AmB), which expands its application spectrum. Clinical use of AmB is limited because of poor water solubility and poor selectivity in its toxicity, which often causes harmful effects on tissues. P1 was the low-molecular-weight hydrogelator (LMWHg) that showed low cytotoxicity and was enzymatically degraded. In general, an LMWHg entraps foreign hydrophobic molecules inside the hydrophobic space in the self-assembled body. P1 successfully solubilized AmB in water as a form of a nanocomplex (NC) that had a chain-like structure. The NCs showed remarkably low toxicity toward Saccharomyces cerevisiae as a model fungus when compared with free AmB, meaning that P1 suppressed the antifungal activity of AmB via coassembly. The suppressed antifungal activity of AmB recovered when P1 in the NCs was degraded by a protease to liberate AmB from the coassembly with P1. P1 at a high concentration formed a hydrogel incorporating AmB (AmB-P1 gel), in which the antifungal activity of AmB was suppressed as well as that in the NC. The coassembly with AmB affected the morphology of the P1 self-assembly. While S. cerevisiae that did not secrete proteases formed a colony on the AmB-P1 gel, Aspergillus oryzae that secreted proteases did not grow on the AmB-P1 gel at all, resulting in the selective killing of the fungus. Because some of malignant, infectious fungi secrete proteases, the coassembly strategy of conventional antifungal drugs with self-assembling molecules should lead to "drug repositioning" of approved drugs in the health and medical fields.