Living Materials Based Dynamic Information Encryption via Light‐Inducible Bacterial Biosynthesis of Quantum Dots

Microbial biosynthesis, as an alternative method for producing quantum dots (QDs), has gained attention because it can be conducted under mild and environmentally friendly conditions, distinguishing it from conventional chemical and physical synthesis approaches. However, there is currently no method to selectively control this biosynthesis process in a subset of microbes within a population using external stimuli. In this study, we have attained precise and selective control over the microbial biosynthesis of QDs through the utilization of an optogenetically engineered Escherichia coli (E. coli). The recombinant E. coli is designed to express smCSE enzyme, under the regulation of eLightOn system, which can be activated by blue light. The smCSE enzymes use L‐cysteine and Cd2+ as substrates to form CdS QDs. This system enables light‐inducible bacterial biosynthesis of QDs in precise patterns within a hydrogel for information encryption. As the biosynthesis progresses, the optical characteristics of the QDs change, allowing living materials containing the recombinant E. coli to display time‐dependent patterns that self‐destruct after reading. Compared to static encryption using fluorescent QD inks, dynamic information encryption based on living materials offers enhanced security. Optogenetically engineered Escherichia coli (E. coli/eLightOn‐smCSE) that biosynthesize CdS quantum dots (QDs) in response to light can be utilized for dynamic information encryption. By harnessing the advantage of living materials, this approach introduces three layers of security: the information remains invisible under natural light, becomes readable only with specific substrates, and auto‐deletes after access.