Zamaleeva A.I.,Ecole Normale Superieure de Paris |
Zamaleeva A.I.,French Institute of Health and Medical Research |
Zamaleeva A.I.,French National Center for Scientific Research |
Zamaleeva A.I.,Kazan Federal University |
And 25 more authors.
Nano Letters | Year: 2014
Small-molecule chemical calcium (Ca2+) indicators are invaluable tools for studying intracellular signaling pathways but have severe shortcomings for detecting local Ca2+ entry. Nanobiosensors incorporating functionalized quantum dots (QDs) have emerged as promising alternatives but their intracellular use remains a major challenge. We designed cell-penetrating FRET-based Ca2+ nanobiosensors for the detection of local Ca2+ concentration transients, using commercially available CANdot565QD as a donor and CaRuby, a custom red-emitting Ca2+ indicator, as an acceptor. With Ca2+-binding affinities covering the range of 3-20 μM, our CaRubies allow building sensors with a scalable affinity for detecting intracellular Ca2+ transients at various concentrations. To facilitate their cytoplasmic delivery, QDs were further functionalized with a small cell-penetrating peptide (CPP) derived from hadrucalcin (HadUF1-11: H11), a ryanodine receptor-directed scorpion toxin identified within the venom of Hadrurus gertschi. Efficient internalization of QDs doubly functionalized with PEG5-CaRuby and H11 (in a molar ratio of 1:10:10, respectively) is demonstrated. In BHK cells expressing a N-methyl-d-aspartate receptor (NMDAR) construct, these nanobiosensors report rapid intracellular near-membrane Ca2+ transients following agonist application when imaged by TIRF microscopy. Our work presents the elaboration of cell-penetrating FRET-based nanobiosensors and validates their function for detection of intracellular Ca2+ transients. © 2014 American Chemical Society.
Collot M.,Ecole Normale Superieure de Paris |
Collot M.,CNRS Biomolecules Laboratory |
Collot M.,Laboratory of Biomolecules LBM |
Loukou C.,Ecole Normale Superieure de Paris |
And 36 more authors.
Journal of the American Chemical Society | Year: 2012
We designed Calcium Rubies, a family of functionalizable BAPTA-based red-fluorescent calcium (Ca2+) indicators as new tools for biological Ca2+ imaging. The specificity of this Ca2+-indicator family is its side arm, attached on the ethylene glycol bridge that allows coupling the indicator to various groups while leaving open the possibility of aromatic substitutions on the BAPTA core for tuning the Ca2+-binding affinity. Using this possibility we now synthesize and characterize three different CaRubies with affinities between 3 and 22 μM. Their long excitation and emission wavelengths (peaks at 586/604 nm) allow their use in otherwise challenging multicolor experiments, e.g., when combining Ca2+ uncaging or optogenetic stimulation with Ca2+ imaging in cells expressing fluorescent proteins. We illustrate this capacity by the detection of Ca2+ transients evoked by blue light in cultured astrocytes expressing CatCh, a light-sensitive Ca2+-translocating channelrhodopsin linked to yellow fluorescent protein. Using time-correlated single-photon counting, we measured fluorescence lifetimes for all CaRubies and demonstrate a 10-fold increase in the average lifetime upon Ca2+ chelation. Since only the fluorescence quantum yield but not the absorbance of the CaRubies is Ca2+-dependent, calibrated two-photon fluorescence excitation measurements of absolute Ca2+ concentrations are feasible. © 2012 American Chemical Society.