Extending visual range of bacteria with upconversion nanoparticles and constructing NIR-responsive bio-microrobots

The motility of bacteria is crucial for navigating competitive environments and is closely linked to physiological activities essential for their survival, such as biofilm development. Precise regulation of bacterial motility enhances our understanding of these complex processes. While optogenetic tools have been used to control and investigate bacterial motility, the excitation light in most existing systems are limited to the visible light spectrum. Here, we introduce a new type of bio-microrobot comprising genetically engineered E. coli cells and orthogonally emissive upconversion nanoparticles that can respond to both 980 nm and 808 nm NIR light. This system allows toggling of bacterial states between tumbling and swimming via simply alternating the NIR light between different wavelengths. It is believed that the use of NIR light with deeper tissue penetration suggests potential applications for these bio-microrobots in areas like targeted drug delivery.