Lysosomes and the nucleus are fundamental to cellular metabolic regulation and genetic information transfer, and their dysfunction is closely linked to both physiological and pathological processes. During zebrafish development, changes in skull bone morphology directly participate in the regulation of bone matrix biomineralization. However, existing fluorescent probes struggle to simultaneously track lysosomes and the cell nucleus, and there is a lack of tools for studying the mechanisms underlying zebrafish skull bone development under oxidative stress. Herein, this study designed and synthesized a fluorescent probe to investigate the association between lysosomes and cell nucleus, and achieved imaging analysis of zebrafish skull bone morphology. Spectroscopic characterization showed that the probe exhibited pronounced fluorescence enhancement in a high-viscosity environment simulated by glycerol. The probe exhibits a sensitive graded response to viscosity and generates fluorescence signals corresponding to different viscosities. Cell imaging confirmed that the probe can detect between normal cells and cells under oxidative stress by selectively targeting lysosomes and cell nucleus. Significantly, under oxidative stress, the probe enabled fluorescence imaging of zebrafish skull bones, achieving the first in vivo visualization of this process. This study not only provides a novel tool for the dynamic visualization of subcellular structures, but also offers direct visual evidence for exploring the molecular mechanisms underlying oxidative stress-induced skeletal developmental abnormalities.
Cobalt is a trace element of analytical interest in food and environmental matrices, particularly in plant-based foods where accurate trace-level determination is relevant to elemental characterization. In this work, a sensitive solid-surface fluorescence (SSF) methodology was developed for Co(II) determination in plant-based food samples. The method is based on formation of a Co(II)-8-hydroxyquinoline (8-HQ) coordination system, followed by solid-phase extraction on Nylon membranes in the presence of sodium dodecyl sulfate (SDS). A 23 full factorial design identified 8-HQ and SDS concentrations as the significant variables, and a central composite design established optimal conditions of [8-HQ] = 2.5 × 10−9 mol L−1 and [SDS] = 2.5 × 10−5 mol L−1. Under optimized conditions, Co(II) was measured at λexc = 390 nm and λem = 460 nm, with a detection limit of 4.3 × 10−2 ng L−1, a quantification limit of 0.14 ng L−1, and a linear range of 0.14–4.3 × 104 ng L−1 (R2 = 0.9992). The method was successfully applied to plant-based food samples, with recoveries close to 100%.The photophysical response of Co(II)[(8HQ)₂(OH)₂]2− as Co(II)-8-hydroxyquinoline model complex was studied with TD-DFT/ωB97X-D/def2-TZVP calculations in water, supported by TheoDORE transition-density analysis and natural transition orbitals (NTOs). At the ground-state geometry, the first intense quartet-like state is Q11 at 3.7101 eV (334.18 nm; f = 0.2729; ⟨S2⟩ = 3.795) and is predominantly ligand-centered (LC, 91.4%). At the relaxed Q9 and Q13 geometries, the corresponding bright LC states are localized on alternate 8-HQ ligands. In the experimental emission region, Q7 is a quartet-like metal-centered (MC) state near 2.6565 eV (466.7 nm; ~82% MC), whereas Q8 is a spin-contaminated LC state near 2.7255 eV (454.9 nm; ~97% LC). These calculations place LC and MC states in the same low-energy region but do not identify a unique emitting state or a specific decay pathway.
