Antibacterial agents with broad-spectrum antibacterial properties have always been in large demand. Lysozyme, a common and inexpensive protein, is widely used in food safety and biomedical applications for antibacterial purposes. However, many pathogens are lysozyme-resistant or insensitive. In this research, we investigated the antibacterial activities and mechanism of oligomers and amyloid fibrils formed from hen egg-white lysozyme (HEWL) against Staphylococcus aureus and Escherichia coli. The HEWL fibrils showed significantly enhanced antibacterial activity against both lysozyme-resistant S. aureus and lysozyme-insensitive E. coli. The HEWL oligomers, on the other hand, did not show an obvious improvement in antibacterial activity compared to native HEWL. Our results indicated that the fibrillation of HEWL can significantly enhance antibacterial activity against both S. aureus and E. coli. The natural and inexpensive HEWL amyloid fibrils can be potentially applied to antimicrobial food packaging, animal feed, antibiotic replacement, etc.

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Protein-based soft ionic conductors have attracted considerable research interest in recent years with great potential in applications at the human− machine interfaces. However, a fundamental mechanistic understanding of the ionic conductivity of silk-based ionic conductors is still unclear. Here, we first developed an environmental-friendly and scalable method to fabricate silk-based soft ionic conductors using silk proteins and calcium chloride. The mechanistic understanding of the ion transport and molecular interactions between calcium ions and silk proteins at variable water contents was investigated in-depth by combining experimental and simulation approaches. The results show that calcium ions primarily interact with amide groups in proteins at a low water content. The ionic conductivity is low since the calcium ions are confined around silk proteins within 2.0−2.6 Å. As water content increases, the calcium ions are hydrated with the formation of water shells, leading to the increased distance between calcium ions and silk proteins (3.3−6.0 Å). As a result, the motion of the calcium ions increased to achieve a higher ionic conductivity. By optimizing the ratio of the silk proteins, calcium ions, and water, silk-based soft ionic conductors with good stretchability and self-healing properties can be obtained. Such protein-based soft ionic conductors can be further used to fabricate smart devices such as electrochromic devices.