Open AccessImmobilization of Recombinant Fluorescent Biosensors Permits Imaging of Extracellular Ion Signals
Author(s) -
Sandra Burgstaller,
Helmut Bischof,
Thomas Rauter,
Tony Schmidt,
Rainer Schindl,
Silke Patz,
Bernhard Groschup,
Severin Filser,
Lucas van den Boom,
Philipp Sasse,
Robert Łukowski,
Nikolaus Plesnila,
Wolfgang F. Graier,
Roland Malli
Publication year - 2021
Publication title -
acs sensors
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.055
H-Index - 57
ISSN - 2379-3694
DOI - 10.1021/acssensors.1c01369
Subject(s) - biosensor , extracellular , biotinylation , biophysics , fluorescence , intracellular , live cell imaging , chemistry , recombinant dna , förster resonance energy transfer , cell , biochemistry , nanotechnology , microbiology and biotechnology , biology , materials science , physics , quantum mechanics , gene
Given the importance of ion gradients and fluxes in biology, monitoring ions locally at the exterior of the plasma membrane of intact cells in a noninvasive manner is highly desirable but challenging. Classical targeting of genetically encoded biosensors at the exterior of cell surfaces would be a suitable approach; however, it often leads to intracellular accumulation of the tools in vesicular structures and adverse modifications, possibly impairing sensor functionality. To tackle these issues, we generated recombinant fluorescent ion biosensors fused to traptavidin (TAv) specifically coupled to a biotinylated AviTag expressed on the outer cell surface of cells. We show that purified chimeras of TAv and pH-Lemon or GEPII 1.0, Förster resonance energy transfer-based pH and K + biosensors, can be immobilized directly and specifically on biotinylated surfaces including glass platelets and intact cells, thereby remaining fully functional for imaging of ion dynamics. The immobilization of recombinant TAv-GEPII 1.0 on the extracellular cell surface of primary cortical rat neurons allowed imaging of excitotoxic glutamate-induced K + efflux in vitro. We also performed micropatterning of purified TAv biosensors using a microperfusion system to generate spatially separated TAv-pH-Lemon and TAv-GEPII 1.0 spots for simultaneous pH and K + measurements on cell surfaces. Our results suggest that the approach can be greatly expanded by immobilizing various biosensors on extracellular surfaces to quantitatively visualize microenvironmental transport and signaling processes in different cell culture models and other experimental settings.