Journal of Fluorescence最新文献

This research presents a new ratiometric fluorescent probe designed for Cu²⁺ detection, utilizing a dual mechanism of intramolecular charge transfer (ICT) and fluorescence resonance energy transfer (FRET). In this probe, coumarin acts as the energy donor while naphthalimide serves as the acceptor, with a 2-picolinic ester moiety functioning as the Cu²⁺ binding site. In the absence of Cu²⁺, the 2-picolinic ester effectively suppresses electron transfer, inhibiting both ICT and FRET, resulting in strong blue fluorescence (λem = 478 nm) from the coumarin moiety. However, upon Cu²⁺ binding, the Cu²⁺-triggered hydrolysis of the 2-picolinic ester activates the ICT process and enables FRET, leading to a distinct yellow fluorescence (λem = 550 nm). Furthermore, the fluorescence intensity ratio (I_550nm/I_478nm) exhibited a strong linear correlation with Cu²⁺ concentrations (0.1-4 µM), achieving a detection limit of 14 nM. Remarkable selectivity and sensitivity toward Cu²⁺ were observed with this probe over an extensive pH range. The probe exhibited excellent biocompatibility in cell viability tests and performed effectively in ratiometric imaging of intracellular Cu²⁺ in A549 cells.

The freshness of food is directly connected with safety, hygiene, and human health. Accurate quantification of biogenic amine level is crucial for assessing the food quality. Therefore, a dual-excitation ratiometric fluorescent probe MCCN based on hemicyanine dye for the examination of biogenic amines was constructed. After the addition of biogenic amines to the MCCN solution, an elimination reaction occurred after a nucleophilic addition reaction to form Schiff base MC-CA, resulting in colorimetric and ratiometric fluorescence responses. The probe MCCN solution was blue. After successively adding biogenic amines (cadaverine, n-butylamine and spermidine), the fluorescence emission intensity of probe MCCN at 709 nm reduced under excitation at 650 nm, meanwhile a new fluorescence emission peak emerged at 545 nm gradually increased under excitation at 450 nm, accompanying by a visible color variation from blue to yellow. The probe MCCN also displayed remarkable selectivity toward biogenic amines over other analytes. Based on the above excellent characteristics, the probe MCCN was successfully utilized to detect biogenic amines in the extract supernatant of shrimp and fish during the spoilage process. In addition, photographing the MCCN-loaded food extract supernatant enabled the correlation of color parameters with storage time, affording an accurate and simple method to reveal food spoilage process. The excellent sensing performance makes the MCCN probe a convenient and accurate screening platform for real-time assessing food freshness.

Viscosity plays a pivotal role in regulating diffusion, a process central to various biological functions. Its detection is crucial in diagnostics, disease detection, and food freshness identification. To probe such micro-viscosity changes in live cells, fluorescent molecular rotors (FMRs) are commonly employed. The study developed two benzothiazole-based fluorescent molecular rotors, BCN1 and BCN2, designed for viscosity sensing via the TICT mechanism. Both probes were structurally characterized by various techniques such as NMR, FTIR, HRMS, SCXRD and exhibited high sensitivity of 1.18 cP (BCN1) and 1.94 cP (BCN2) in methanol-glycerol mixtures. Photophysical studies revealed strong emission, large Stokes shifts, pH resilience, and minimal aggregation. Biocompatibility was confirmed through cytotoxicity assays, enabling successful application in live-cell imaging and food spoilage detection. Solid-state fluorescence probes enabled high-resolution latent fingerprint visualization across various substrates, revealing nine different features of three different levels of fingerprint analysis. DFT calculations supported their electronic properties. Collectively, BCN1 and BCN2 emerge as multifunctional probes with broad utility in biological, environmental, and forensic applications.

A novel fluorescent Schiff base chemosensor, N'¹,N'⁶-bis((E)-3,5-dibromo-2-hydroxybenzylidene)adipohydrazide (DBSA), has been developed for the detection of Cobalt (II) ions. DBSA exhibits distinct fluorescence enhancement upon interacting with Co(II) ions via photoinduced electron transfer (PET). The developed sensor demonstrates a remarkable sensitivity, with the detection limits of 9.9 nM for Co(II) ions, which aligns well with the Environmental Protection Agency (EPA) regulatory thresholds for drinking water contaminants. Structural characterization by LC-MS, FTIR coupled with Job's plot and NMR titration studies confirm the formation of DBSA-Co complex with a binding constant of 4.61 × 10⁶ M^- 1. The chemo sensor exhibits a quantum yield of 0.082, highlighting its potential applicability in photochemical processes. Computation studies were used to further investigate the binding interactions with Co²⁺ ions. The practical utility of DBSA has been validated through successful analyses in varied aqueous matrices, including tap water, lake water and recycled water. Cytotoxicity assessment via MTT assays on SH-SY5Y cells confirms excellent biocompatibility of the probe. This work presents a significant advancement in the design of efficient molecular probes for environmental monitoring, offering a robust platform for the concurrent detection of transition-metal ions in aqueous systems.

Fluorescent conjugated polymers, recognized for their environmental stability, biocompatibility, tunable conductivity, and facile processability, have been extensively employed in the fabrication of multifunctional materials. In this study, three novel fluorescent conjugated polymers-PF-SO10 (blue), PF-SO10-BT1 (green), and PF-SO10-DTBT1 (red)-were synthesized and characterized, and subsequently applied for the enhancement of latent and visible blood fingerprints via powder dusting. Under 365 nm irradiation, the developed fingerprints displayed strong fluorescence, enabling clear visualization across six non-porous substrates and revealing third-level fingerprint details. The prominent photoluminescence property of the conjugated polymers provides a basis for the visualization of blood fingerprints. In a comparative evaluation with conventional reagents, including Amido Black 10B (AB) and 3,3',5,5'-Tetramethylbenzidine (TMB), demonstrated the superior performance of this method. To address the potential subjectivity of visual inspection, a Python-based quantitative evaluation framework was further introduced, incorporating metrics such as global contrast, average gradient sharpness, local contrast, and ridge orientation consistency. Collectively, the findings highlight the advantages of this strategy, including low cost, high contrast, strong selectivity, and minimal background interference, thereby offering a promising approach for reliable detection and visualization of blood fingerprints in forensic applications.

Extensive surgical resection improves survival in cancer patients. Fluorescence-guided imaging techniques have significantly enhanced the precision of cancer resections. Triple-negative breast cancer (TNBC) lacks expression of the estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2), and no other targetable molecules have been identified. In this study, we verified that the L-type amino acid transporter 1 (LAT1, also known as SLC7A5) is overexpressed in triple-negative breast cancer (TNBC) cells and we constructed a novel near-infrared fluorescent dye Cys-PEG₅-IR target to SLC7A5. We then report the SLC7A5 receptor specificity of Cys-PEG₅-IR as a contrast agent for TNBC imaging in vitro and in vivo. The conjugation elevated cell fluorescence on SLC7A5-overexpressing TNBC cells and produced minimal cell fluorescence when treated with SLC7A5 knockdown. Tumor uptake of Cys-PEG₅-IR was significantly higher than the unlabeled IR in the subcutaneous MDA-MB-231 TNBC xenograft. This work highlights the prospect of using methionine (Met) transport pathway as an alternative strategy for targeting cancer cells, especially TNBC cells.