Deep Learning-Assisted Automated Multidimensional Single Particle Tracking in Living Cells.

The translational and rotational dynamics of anisotropic optical nanoprobes revealed in single particle tracking (SPT) experiments offer molecular-level information about cellular activities. Here, we report an automated high-speed multidimensional SPT system integrated with a deep learning algorithm for tracking the 3D orientation of anisotropic gold nanoparticle probes in living cells with high localization precision (<10 nm) and temporal resolution (0.9 ms), overcoming the limitations of rotational tracking under low signal-to-noise ratio (S/N) conditions. This method can resolve the azimuth (0°-360°) and polar angles (0°-90°) with errors of less than 2° on the experimental and simulated data under S/N of ∼4. Even when the S/N approaches the limit of 1, this method still maintains better robustness and noise resistance than the conventional pattern matching methods. The usefulness of this multidimensional SPT system has been demonstrated with a study of the motions of cargos transported along the microtubules within living cells.

A novel reversible fluorescent probe for Cu2+ and S2-ions and imaging in living cells.

A novel fluorescent probe TSOC (thiazole salicylaldehyde oxazole chlorinated) was synthesized based on benzothiazole conjugated olefinic bonds with salicylicaldehyde unit as fluorophore and a phenyl oxazole unit as bonding unit. The probe could reversibly detect of Cu2+and S2-over other common ions with longer emission and large stokes shift in an aqueous solution at pH 7.3 (DMSO-Hepes, v/v, 5:1, 10 mM). The bonding mechanism was supported through the titration experiment of fluorescence and absorption spectroscopy,1H-NMR titration, HR-MS and DFT calculations. Moreover, the probe further exhibited good cell permeability and were successfully used to visualize Cu2+and S2-in living cells.

A novel fluorescence probe for the selective detection of cysteine in aqueous solutions and imaging in living cells and mice.

A novel fluorescent probe based on hydroxyquinoline conjugated with a charged trimethylindolenine unit Toc-Ac was developed, which exhibited long wavelength emission (560 nm) and a large Stokes shift (∼140 nm) due to the intrinsic mechanism of the intramolecular charge transfer process. The probe Toc-Ac showed a highly sensitive response to Cys (the detection limit was 3.86 × 10-8 M) in aqueous solution and was successfully applied for detecting endogenous Cys in living cells and mice.

A hemicyanine-based "turn-on" fluorescent probe for the selective detection of Cu2+ ions and imaging in living cells.

A novel hemicyanine-based fluorescent probe was developed for the fast, selective, and reversible detection of Cu2+ ions with "turn-on" fluorescence response in the aqueous solution. The sensing mode was demonstrated through fluorescence, UV-vis, HRMS, 1H NMR, and DFT calculations. The probe was successfully used for the imaging of Cu2+ ions in living cells.

A novel near-infrared turn-on fluorescent probe for the detection of Fe3+ and Al3+ and its applications in living cells imaging.

In this study, a new hemicyanidine-based colorimetric-fluorescent probe L has been synthesized and characterized by X-ray single crystal diffraction, NMR, HRMS and other technologies. The probe L serves as a "turn-on" probe for the detection of Fe3+ and Al3+ ions in DMF-HEPES system with a high sensitivity and an excellent selectivity. The probe L manifesting the color of the solution containing L turns red on the addition of Fe3+, and turns pink on the addition of Al3+. The fluorescence turn-on detection of Fe3+ and Al3+ ions is attributed to the photo-induced electron transfer (PET) process and the exertion of the chelation-enhanced fluorescence effect (CHEF) mechanism. The results of thin layer silica gel plate coloration experiments also present the same characteristics. Additionally, we further demonstrate that the probe L exhibit good cell permeability and could be employed to monitor Fe3+ and Al3+ ions in the living cells.

Coumarin-based colorimetric-fluorescent sensors for the sequential detection of Zn2+ ion and phosphate anions and applications in cell imaging.

Two novel coumarin based fluorescent sensors CHP and CHS have been synthesized for the sequential detection of Zn2+ ion and phosphate anion (PA) in DMF/HEPES buffer medium (1/5 v/v, 10 mM, pH = 7.4). On the addition of Zn2+ ion to the solution of CHP or CHS resulted in a pronounced fluorescence enhancement, accompanying noticeable color change (under UV or daylight), while there was hardly obvious change with other competing metal ions co-existing. The detection limits (DL) of CHP and CHS toward Zn2+ were separately determined as 1.03 × 10-7 (R2 = 0.9886) and 1.87 × 10-7 (R2 = 0.9902). The PET binding processes were affirmed by spectroscopic techniques, HRMS experiments and theoretical calculations. Subsequently, the CHP-Zn2+ or CHS-Zn2+ complexes showed high selectivity fluorescence quenching toward PA by snatching Zn2+ ion from its complex and the binding processes were reversible. DLs were calculated as 2.07 × 10-7 M (R2 = 0.9928) and 2.63 × 10-7 M (R2 = 0.9954), respectively. Furthermore, the cell imaging experiments demonstrated that the sensors were capable of detecting of Zn2+ and PA in vitro cells.

Indole-based colori/fluorimetric probe for selective detection of Cu2+ and application in living cell imaging.

A highly sensitive and selective indole-based probe IHT exhibited obvious color change from colorless to violet easily detected by naked eye as well as 'turn on' fluorescence response to Cu2+ ion at physiological pH condition. The detection limit was determined to be as low as 8.93 × 10-8 M, which was much lower than drinking water permission concentrations by the United States Environmental Protection Agency. The 1:2 binding mechanism was well confirmed by fluorescence titration, Job's plot, HRMS, IR analysis and DFT calculations. Furthermore, the probe IHT was successfully used for fluorescence imaging of Cu2+ ion in living cells.

Fluorescent schiff base probes for sequential detection of Al3+ and F- and cell imaging applications.

Two novel Schiff-base fluorescent probers SQ and NQ based on 8-hydroxyquinoline moiety were designed and synthesized. The both probes were capable of binding with Al3+ by naked eye detection to produce a significant fluorescence enhancement response with a detection limit of 1.48 × 10-8 and 4.23 × 10-8 M, respectively. At the same time, the formed complexes SQ-Al3+ and NQ-Al3+ could sequentially detect F-, and the detection limits of F- were determined to be 1.64 × 10-7 and 3.58 × 10-8 M, respectively. The "off-on-off" fluorescence response process demonstrated that the binding were reversible. The probes were further successfully utilized to detect Al3+ and F- in vitro PC12 cells.

A novel fluorescent-colorimetric probe for Al3+ and Zn2+ ion detection with different response and applications in F- detection and cell imaging.

A novel Schiff base fluorescence probe (HL) was synthesized by the condensation of salicylaldehyde and an 8-aminoquinoline derivative. This probe acts as a "turn-on" dual selectivity fluorescence probe for Zn2+ and Al3+ ions, providing different colors and detection limits (DL) of 11.5 and 23.5 nM, respectively. Moreover, when Zn2+ and Al3+ co-exist, HL exhibits a preference for Al3+ by displacing Zn2+ from the HL-Zn2+ complex, realizing a dual-channel signal output for Al3+. The HL-Al3+ system could further discern F- by a "turn-off" fluorescence response with a DL of 86.0 nM. Furthermore, the probe HL was capable of monitoring intracellular Al3+, Zn2+ and F- in living PC12 cells in vitro through fluorescence imaging, which proved its value in potential in vivo applications.