Labelling Bacterial Nanocages with Photo-switchable Fluorophores

• Published in: Chemphyschem Vol. 17; no. 12; pp. 1815 - 1818
• Main Authors: Putri, Rindia M., Fredy, Jean Wilfried, Cornelissen, Jeroen J. L. M., Koay, Melissa S. T., Katsonis, Nathalie
• Format: Journal Article
• Language: English
• Published: Germany Blackwell Publishing Ltd 17-06-2016; Wiley Subscription Services, Inc; John Wiley and Sons Inc
• Subjects: Bacteria; Bacterial Proteins - chemistry; Benzopyrans - chemistry; Brevibacterium - chemistry; Brevibacterium linens; Communication; Communications; Fluorescent Dyes - chemistry; Indoles - chemistry; Light; molecular switches; Nanostructures - chemistry; Nanotechnology; Particle Size; Photochemical Processes; photochromism; protein cages; self-assembly; spiropyrans; Surface Properties; Ultraviolet Rays; spiropyrans; self-assembly; protein cages; photochromism; molecular switches
• ISSN: 1439-4235; 1439-7641
• DOI: 10.1002/cphc.201600013

The robustness and biocompatibility of bacterial nanocages holds promise for bio‐nanotechnologies. The propensity of these nano‐carriers to penetrate cells has been demonstrated, which calls for the development of tracking strategies, both in vitro and in vivo. Here, we label bacterial nanocages with photo‐switchable fluorophores, to facilitate their imaging by super‐resolution microscopy. We demonstrate the functionalization of the encapsulin from Brevibacterium linens with a spiropyran, which is not fluorescent, by covalent attachment to the amine residues at the outer encapsulin shell. Upon alternating irradiation with ultraviolet and visible light, the spiropyran switches forth and back to its fluorescent merocyanine photo‐isomer and thus the fluorescence can be switched on and off, reversibly. We also show that the bacterial compartments preserve their structural integrity upon covalent modification and over at least five irradiation cycles.
Blinking at the surface of bacterial cages: The protein‐based nanocage of Brevibacterium linens is labeled using photoswitchable fluorophores. This is achieved by covalent attachment of a spiropyran switch to the amine residues that are available at the outer surface of the nanocage. Upon alternating ultraviolet and visible light irradiation, the fluorescence switches on and off while the protein cage retains its structural integrity.