A Simple Schiff Base as Fluorescent Probe for Detection of Al3+ in Aqueous Media and its Application in Cells Imaging

Novel Flavonoid Photoswitchable "Turn-On" Fluorescent Chemosensors: Synthesis of Bromo Flavonols for Nanomolar Aluminum Ion Detection and Cellular Imaging, among Other Applications

Aluminum (Al), a non-essential element in living systems, can potentially cause chronic toxicity. Therefore, it is crucial to have a specific and sensitive method for detecting Al3+ in order to assess its risk to life. In this study, we designed and synthesized a novel fluorescent probe (IV) based on bromoflavonol. Upon binding to Al3+, probe IV exhibits a blue shift in emission and enhanced fluorescence, making it suitable for Al3+ detection. Our UV-Vis absorption and fluorescence emission spectra demonstrate that probe IV has high selectivity and sensitivity towards Al3+ while being immune to interference from other metal ions. Through fluorescence titration, we determined that the detection limit (LOD) of probe IV for Al3+ is 1.8 × 10-8 mol/L. Job's curve and 1 H NMR titration further confirmed a 1:1 binding stoichiometry between probe IV and Al3+. Additionally, using DFT (Density Functional Theory), we calculated the energy gap difference between IV and IV + Al3+ and found that the complex formed by probe IV and Al3+ is more stable than IV alone. We successfully detected Al3+ in tap water and river water from the middle regions of the Han River, achieving recoveries of over 96% using this probe. This demonstrates its potential for quantitative detection of Al3+ in environmental water samples. Moreover, we successfully used the probe for imaging Al3+ in MG63 cells, suggesting its potential application in biological imaging.

Fluorescent ovalbumin-functionalized gold nanocluster as a highly sensitive and selective sensor for relay detection of salicylaldehyde, Hg(II) and folic acid

A sensitive and selective relay-based scheme for the detection of salicylaldehyde, Hg2+, and folic acid (FA) has been demonstrated using fluorescent ovalbumin functionalized gold nanoclusters (OVA-AuNCs, λem = 655 nm) in this article. The OVA-AuNCs were conjugated to salicylaldehyde via an imine linkage to form Salic_OVA-AuNCs conjugate. The molecular docking study reveals that multiple functional groups and amino acid residues are involved in the interaction between salicylaldehyde and the OVA-AuNCs. The coupling of salicylaldehyde with OVA-AuNCs results in fluorescence quenching at 655 nm and concomitant formation of an emission band at 500 nm, which have leveraged to detect salicylaldehyde down to 2.02 µM. Following that, the Salic_OVA-AuNCs has been used for the detection of Hg2+ and FA. Several processes, such as internal charge transfer (ICT), photoinduced electron transfer (PET) and metallophilic interactions, are involved between the Salic_OVA-AuNCs nanoprobe and the analytes, which allowed to detect Hg2+ and FA down to 0.13 nM and 0.11 nM, respectively. The Salic_OVA-AuNCs nanoprobe has an additional naked-eye utility when applied to paper-strip sensing strategy for Hg2+ and FA detection.