Biomimetic Crystallization of MnFe₂O₄ Mediated by Peptide‐Catalyzed Esterification at Low Temperature

Abstract Enzymes are some of the most efficient catalysts in nature. If small catalytic peptides mimic enzymes, there is potential for broad applications from catalysis for new material synthesis to drug development, due to the ease of molecular design. Recently a hydrogel‐based combinatory phage display library was developed and protease‐mimicking peptides were identified. Here we advanced the previous discovery to apply one of these catalytic peptides for the synthesis of bimetal oxide nanocrystals through the catalytic ester‐elimination pathway. Conventional bimetal oxide crystallization usually requires high temperatures above several hundred °C; however, this catalytic peptide could grow superparamagnetic MnFe₂O₄ nanocrystals at 4 °C. Superconducting quantum interference device (SQUID) analysis revealed that MnFe₂O₄ nanocrystals grown by the catalytic peptide exhibit superparamagnetism. This study demonstrates the usefulness of protease‐mimicking catalytic peptides in the field of material synthesis.