Design and optimization of bifunctional peptides for controlled core–shell nanocapsule formation

Nanocapsules with core–shell structures hold significant potential across diverse applications. Biomimetic templating offers a benign approach for synthesizing inorganic nanostructures using biomolecules, leveraging amino acid sequences from natural sources and combinatorial biology in a process known as biomineralization. This study investigates the design and functionality of bifunctional peptides for controlled interfacial biosilicification. Five bifunctional peptides were designed and compared for their surface activity, structural behavior, and biosilicification capability under benign conditions. AM1 and SurSi-G1 demonstrate rapid adsorption, lower interfacial tension, and higher surface activity. In contrast, SurSi and its variants show slower adsorption due to higher molecular charge, resulting in high interfacial tension. Biosilicification assays confirmed that peptide charge strongly influences particle morphology, with SurSi and SurSi-R3 yielding well-dispersed silica nanoparticles, while AM1, SurSi-R2, and SurSi-G1 formed larger aggregates. Low ionic strength and sufficient surface charge enhance electrostatic interaction between positively charged bifunctional peptides and negatively charged hydrolyzed silicic acid, facilitating controlled biosilicification at interface and enabling the precise formation of core–shell nanocapsules. These findings highlight the pivotal role of peptide sequence and charge distribution in determining surface activity and interfacial biosilicification, providing insights for optimizing nanocapsule synthesis.