pH‐Responsive Protein Conformation Transistor

Abstract Analogous to electronic transistors, transistor‐like responsive materials undergo sharp structural transitions in response to a very narrow range of microenvironment signals. This kind of material is typically limited to synthetic polymer‐derived nanoscale assembly or disassembly and has profound implications for modern high‐tech applications. Herein, we evolve this system from synthetic polymers to biopolymers and extend the corresponding assembly scale from the nanoscale to meso/macro‐scale. We develop unique protein nanocrystals with core–shell structures through a two‐step nucleation process. The protein nanocrystals exhibit exceptional transistor‐like pH‐responsive mesoscale assembly through the formation of inter‐particle β‐sheet linkers. This allows ultrasensitive cross‐linking behavior, such as self‐coacervation at a water/water interface, ultrafast gelation in seconds, and ultrasensitive swelling for detection of basic vapors at extremely low concentrations. This breakthrough has great promise for broader applications such as drug encapsulation and delivery, biosensing, cytomimetic materials, and microfluidic chemistry.