Development of Photoactivated Fluorescent N‐Hydroxyoxindoles and Their Application for Cell‐Selective Imaging

Abstract

Photoactivatable fluorophores are essential tools for studying the dynamic molecular interactions within important biological systems with high spatiotemporal resolution. However, currently developed photoactivatable fluorophores based on conventional dyes have several limitations including reduced photoactivation efficiency, cytotoxicity, large molecular size, and complicated organic synthesis. To overcome these challenges, we herein report a class of photoactivatable fluorescent N-hydroxyoxindoles formed through the intramolecular photocyclization of substituted o-nitrophenyl ethanol (ONPE). These oxindole fluorophores afford excellent photoactivation efficiency with ultra-high fluorescence enhancement (up to 800-fold) and are small in size. Furthermore, the oxindole derivatives show exceptional biocompatibility by generating water as the only photolytic side product. Moreover, structure–activity relationship analysis clearly revealed the strong correlation between the fluorescent properties and the substituent groups, which can serve as a guideline for the further development of ONPE-based fluorescent probes with desired photophysical and biological properties. As a proof-of-concept, we demonstrated the capability of a new substituted ONPE that has an uncaging wavelength of 365–405 nm and an excitation/emission at 515 and 620 nm, for the selective imaging of a cancer cell line (Hela cells) and a human neural stem cell line (hNSCs).

Tumor Customized 2D Supramolecular Nanodiscs for Ultralong Tumor Retention and Precise Photothermal Therapy of Highly Heterogeneous Cancers

“…2-(3-Cyano-4,5,5-Trimethylfuran-2(5H)-Ylidene)Malononitrile (Compound 1): According to a reported protocol, [35] 3-hydroxy-3-methyl-2butanone (26.00 g, 10.00 mmol) was dissolved in absolute ethanol first, to which malononitrile (31.94 g, 30.00 mmol) and magnesium ethoxide (1.24 g, 11.00 mmol) was added later. The solution was stirred overnight at 65 °C under N 2 atmosphere, which was concentrated after cooling to room temperature.…”

“…Cyclohex-1-En-1-Yl)Vinyl)-5,5-Dimethylfuran-2(5H)-Ylidene)Malononitrile (Compound 3): According to a reported protocol, [35] to a solution of compound 1 (0.5 g, 2.895 mmol) in ethanol (25 mL) was added compound 2 (0.635 g, 3.185 mmol). The resulting solution was refluxed overnight.…”

A light-activated magnetic bead strategy utilized in spatio-temporal controllable exosomes isolation

“…Herein, we developed a novel strategy using magnetic bead-based capture and light-activated elution for spatiotemporally controllable exosome isolation from serum. As shown in Figure 1 , we anchored CD63 aptamer on the surface of magnetic beads via light-sensitive nitrobenzene group, which was cleaved by ultraviolet (UV) light at around 365 nm ( Chang et al, 2009 ; Kobayashi et al, 2012 ; Lai et al, 2016 ; Wang et al, 2017 ; Hentzen et al, 2020 ). CD63 is member of tetraspanins that is considered to be a reliable exosome surface marker.…”

When the strategies for cellular selectivity fail. Challenges and surprises in the design and application of fluorescent benzothiadiazole derivatives for mitochondrial staining

“…[11][12][13] These fluorophores have, however, already shown limitations and drawbacks associated with their use. In this sense, several groups are developing new bioprobes derived from other heterocyclics (Figure 1) such as phenazines, 14 quinolines, 15 pyridines, 16 imidazolones, 17 indoles, 18 pyrimidines, 19 benzothiadiazoles 20 and others. [21][22][23][24][25][26][27][28][29][30] A significant challenge pertains to the appropriate design of stable and efficient fluorophores capable of specific responses inside the astonishing and multifactorial environment of living cells.…”