"Turn-On" Fluorescent and Colorimetric Detection of Zn2+ Ions by Rhodamine-Cinnamaldehyde Derivative

Selective immediate detection of Cu2+ by a pH-sensitive rhodamine-based fluorescence probe in breast cancer cell-line

A biocompatible fluorogenic chemosensor (N-(3-carboxy acryloyl)) rhodamine B (RHA) comprising a furan-2,5-dione receptor and a rhodamine fluorophore via an iminohydrazine crosslinker has been prepared for more scrutinizing optical properties and utilization in molecular imaging of living cells. The consequences indicated that RHA not only is a good pH indicator in acidic media but also can be used as a great sensitive fluoroionophore with high selectivity. The fluorescence emission of the molecule RHA is quite stable in the presence of 15 diverse cations, 18 anions (especially H₂PO₄^-, S², and F^-), and 5 amino acids with the different functional group as a model, except Cu²⁺ ions with observable emission intensity changing. The Cu²⁺ probe has a dual functional effect, an "on-off" mechanism in solvent media, and an "off-on" mechanism in Phosphate Buffered Saline (PBS) in acidic pH conditions. The detection limits for Cu²⁺ in acetone-water media was 0.69 μM and 0.18 μM in pH = 5.0. Moreover, RHA can fluorescently and colorimetrically image Cu²⁺ ions in acidic and neutral pH with low cytotoxicity in living cells.

Visual Detection of Cucumber Green Mottle Mosaic Virus Based on Terminal Deoxynucleotidyl Transferase Coupled with DNAzymes Amplification

A simple, rapid, and sensitive visual detection method for observing cucumber green mottle mosaic virus was reported based on the template-independent polymerization activity of terminal deoxynucleotidyl transferase (TdT), coupled with the cascade amplification of Mg²⁺-dependent DNAzyme and hemin/G-quadruplex DNAzyme. Briefly, the hybridized dsDNA of T1/P1 was cut into two parts at its position of 5′-AA↓CG↑TT-3′ by the restricted enzyme AcII. The longer, newborn fragment originating from P1 was tailed at its 3’-end by oligo dG, and an intact enzymatic sequence of Mg²⁺-dependent DNAzyme was generated. The substrate sequence in the loop segment of the hairpin probe (HP) hybridized with the newborn enzymatic sequence and was cleaved into two parts in the presence of Mg²⁺. The locked G-quadruplex sequence in the stem segment of the HP was released, which catalyzed the oxidation of ABTS^2- in the presence of H₂O₂, and the resulting solution turned green. A correlation between the absorbance and concentration of T1 was obtained in a range from 0.1 pM to 2 nM, with a detection limit of 0.1 pM. In addition to promoting a lower detection limit and shorter monitoring time, this method also demonstrated an excellent selectivity to single or double nucleotide changes. Therefore, the designed strategy provided a rapid and efficient platform for viral inspection and plant protection.