Charge-Balanced Design for Redox-Responsive Disassembly of Ampholytic β-Sheet Peptide Nanofibers

Self-assembling β-sheet-forming peptides are attractive building blocks for drug delivery nanomaterials. However, their strong intermolecular interactions often lead to high structural stability, which can hinder intracellular dissociation and limit cargo availability. Here, we propose a charge-compensated ampholytic design strategy for β-sheet peptide nanofibers that undergo destabilization and disassembly under reducing conditions. Six ampholytic peptides comprising an anionic main-chain peptide (β-sheet-forming motif, model antigenic cargo, and oligoglutamic acid segment) and a disulfide-linked cationic segment were designed and synthesized to vary the lengths and charges of the anionic and cationic segments, as well as the cationic insertion position. Four peptides formed nanofibers in 4×phosphate buffered saline (4×PBS) and the resulting nanofibers remained stable after dilution to 1×PBS, retaining β-sheet-rich secondary structures and fibrillar morphologies for at least 24 h. Under reducing conditions, the four preformed nanofibers exhibited distinct behaviors, including reduction-insensitive persistence, disassembly, and transient destabilization followed by re-stabilization, depending on peptide charge design. Redox-triggered disassembly was favored when the main-chain peptide had sufficient anionic character and the cationic segment was of moderate length and charge. This study therefore provides a molecular design strategy for controlling the destabilization of β-sheet peptide nanofibers under reducing conditions through disulfide-cleavage-induced disruption of charge compensation.