PEGylated Red-Emitting Calcium Probe with Improved Sensing Properties for Neuroscience.

Monitoring calcium concentration in the cytosol is of main importance as this ion drives many biological cascades within the cell. To this end, molecular calcium probes are widely used. Most of them, especially the red emitting probes, suffer from nonspecific interactions with inner membranes due to the hydrophobic nature of their fluorophore. To circumvent this issue, calcium probes conjugated to dextran can be used to enhance the hydrophilicity and reduce the nonspecific interaction and compartmentalization. However, dextran conjugates also feature important drawbacks including lower affinity, lower dynamic range, and slow diffusion. Herein, we combined the advantage of molecular probes and dextran conjugate without their drawbacks by designing a new red emitting turn-on calcium probe based on PET quenching, Rhod-PEG, in which the rhodamine fluorophore bears four PEG4 units. This modification led to a high affinity calcium probe (Kd = 748 nM) with reduced nonspecific interactions, enhanced photostability, two-photon absorbance, and brightness compared to the commercially available Rhod-2. After spectral characterizations, we showed that Rhod-PEG quickly and efficiently diffused through the dendrites of pyramidal neurons with an enhanced sensitivity (ΔF/F0) at shorter time after patching compared to Rhod-2.journal article2017 Nov 222017 10 24imported"Supporting information" disponible sur le site de l'éditeur à l'adresse suivante : http://pubs.acs.org/doi/suppl/10.1021/acssensors.7b0066

A ratiometric fluorescent molecular probe with enhanced two-photon response upon Zn 2+ binding for in vitro and in vivo bioimaging

A bipyridine centered donor–acceptor–donor (D–π–A–π–D) type ratiometric fluorescent molecular probe exhibited an unprecedented enhancement in the two-photon absorption (2PA) cross section upon Zn2+ binding. Moreover, owing to the excited state charge-transfer of the fluorophore π-backbone, a significant enhancement in the two-photon (2P) excited fluorescence intensity was observed upon Zn2+ binding, resulting in a 13-fold enhancement in the 2PA cross section and a 9-fold enhancement in fluorescence brightness at 620 nm when compared to the cation-free fluorophore. The large 2PA cross section of 1433 GM and 2P action cross section (860 GM), with an excellent 2P excited fluorescence variation from 517 to 620 nm upon Zn2+ binding, facilitated the ratiometric monitoring of free zinc ions in cells. The low cytotoxicity and good photostability of the fluorophore allowed two-photon Zn2+ imaging of HeLa cells. In addition, in vivo two-photon imaging of Zn2+ ions in hepatocytes of live rats illustrated the viability of the probe in tissue imaging and monitoring of free zinc ions in live cells.NRF (Natl Research Foundation, S’pore)Accepted versio