Relay detection of Cu2+ and bovine serum albumin by a dansyl derivative-based fluorescent probe

"From darkness to radiance": Light-induced type I and II ROS-mediated apoptosis for anticancer effects of dansylpiperazine-bearing squaraine dyes

Photodynamic therapy relies on the generation of cytotoxic effects triggered by the irradiation of a photosensitizer molecule, resulting in the production of reactive oxygen species at concentrations exceeding physiological levels. In this context, squaraine dyes, a prominent family of second-generation photosensitizers, have gained increasing attention for their remarkable properties, with their photobiological characteristics recently emerging as a key focus of in-depth research. Dansylpiperazine-bearing squaraine dyes exhibited strong absorption in the red visible spectral region, excellent photostability, and a predicted ability to interact with human serum albumin, potentially serving as a transport vehicle to target sites. Benzothiazole derivatives excelled in photodynamic activity, demonstrating 7- to 11-fold increased cytotoxicity upon irradiation against prostate adenocarcinoma PC-3 cells and tumor selectivity indices exceeding 10 when compared to normal NHDF cells. In contrast, the introduction of the dansylpiperazino group in indole-derived compounds unexpectedly declined their photodynamic activity. Concerning benzothiazole-based ones, multiple reactive oxygen species were shown to contribute to the photodynamic effects, with singlet oxygen playing a key role. Squaraine internalization was observed in various cytoplasmic organelles, including mitochondria, endoplasmic reticulum, and lysosomes, without clear evidence of preferential localization to any single organelle. Non-genotoxic in the dark, the squaraines induced cell death by apoptosis upon light activation, as evidenced by significant DNA fragmentation and increased caspase 3/7 activation, particularly for the dye with N-ethyl chains, at concentrations below 1.0 μM, underscoring their potency. Checkpoint arrests in G1 and G2/mitosis were observed for non-irradiated and irradiated conditions, respectively, highlighting the antiproliferative effects of these squaraine dyes.

A Cu2+-triggered turn-on fluorescence non-enzymatic probe based on covalent organic framework for the detection of methyl parathion

BACKGROUND

Methyl parathion, a potent organophosphorus insecticide, is extensively employed in agriculture and animal husbandry, leading to significant environmental contamination with pesticide residues, posing a grave threat to human health. This compound irreversibly inhibits acetylcholinesterase (AChE) in the human nervous system, resulting in the accumulation of acetylcholine (ACh), which is detrimental. Various enzyme activity-based assays have been explored due to its pathogenic mechanism, yet these methods are fraught with limitations. Thus, the development of a highly selective, sensitive, rapid, and effective method for detecting methyl parathion residues is crucial.

RESULT

In this study, we introduce a novel, non-enzymatic fluorescent probe for methyl parathion detection. This probe is designed to specifically trigger the fluorescence signal of TAPB-DMTA-COF through the interaction of copper ions with the imine moiety within the TAPB-DMTA-COF structure. The detection of methyl parathion in aqueous environments is facilitated by the Inner filter effect. Compared to previously reported enzyme-catalyzed reaction probes, this probe exhibits a faster reaction time, is not influenced by enzyme activity, and demonstrates high specificity and sensitivity. The probe exhibits a good linear response in the concentration range of 0.56-5.46 μM, with a detection limit of 30.698 nM. Furthermore, the probe yielded satisfactory recoveries of methyl parathion (93.47 %-99.5 %) in different real water samples through spiking recovery experiments.

SIGNIFICANCE

The fluorescent probe based on Cu2+/TAPB-DMTA-COF realizes the fluorescence detection of methyl parathion. The establishment of this simple, efficient, and rapid detection platform offers a new approach for the detection of pesticide residues in aquatic environments. The introduction of metal ions, along with the construction of COF materials and the use of fluorescence signal turn-on, provides a rational design strategy for such detection methods.

A dual-signals fluorometric and colorimetric peptide-based probe for Cu(II) and glyphosate detection and its application for bioimaging and water testing

A novel dual-signal fluorometric and colorimetric probe FMDH (5-FAM-Met-Asp-His-NH2), incorporating a tripeptide (Met-Asp-His-NH2) linked to 5-carboxyfluorescein (5-FAM), was firstly synthesised. FMDH demonstrated exceptional selectivity and sensitivity, rapid response, wide pH response range and robust anti-interference capabilities for monitoring Cu2+. This was achieved through a distinctive naked-eye colorimetric and fluorescent quenching behaviour. A good linearity within the range of 0-3 μM (R2 = 0.9914) was attained, and the limit of detection (LOD) for Cu2+ was 47.4 nM. Furthermore, the FMDH-Cu2+ ensemble responded to glyphosate with notable selectivity and sensitivity. A good linear correlation (R2 = 0.9926) was observed at the lower concentration range (2.4-7.8 μM) and achieving a detection limit as low as 29.9 nM. The response time of FMDH with Cu2+ and glyphosate were less than 20 s, and the pH range of 7-11 that was suitable for practical application under physiological pH conditions. MTT assays confirmed that FMDH offers good permeability and low toxicity, facilitating successful application in imaging analysis of Cu2+ and glyphosate in living cells and zebrafish. In addition, FMDH was employed in the detection of these analytes in real water samples. Cost-effective, highly sensitive and easily prepared FMDH-impregnated test strips were developed for the efficient visual detection of Cu2+ and glyphosate under 365 nm UV light. Increasing concentrations of Cu2+ and glyphosate resulted in notable colour changes under 365 nm UV light, enabling visual semi-quantitative analysis via a smartphone colour-analysis App.

Rational design of peptide-based fluorescent probe for sequential recognitions of Cu(II) ions and glyphosate: Smartphone, test strip, real sample and living cells applications

A new peptide-based fluorescent probe named DMDH with easy-to-synthesize, excellent stability, good water solubility and large Stokes shift (225 nm) was synthesized for highly selective sequential detections of copper ions (Cu2+) and glyphosate (Glyp). DMDH demonstrated great detection performance towards Cu2+via strong fluorescence quenching, and forming non-fluorescence DMDH-Cu2+ ensemble. As a new promising cascade probe, the fluorescence of DMDH-Cu2+ ensemble was significantly recovered based on displacement approach after glyphosate was added. Interestingly, the limit of detections (LODs) for Cu2+ and glyphosate were 40.6 nM and 10.6 nM, respectively, which were far lower than those recommended by the WHO guidelines for drinking water. More importantly, DMDH was utilized to evaluate Cu2+ and glyphosate content in three real water samples, demonstrating that its effectiveness in water quality monitoring. Additionally, it is worth noting that DMDH was also applied to analyze Cu2+ and glyphosate in living cells in view of significant cells permeability and low cytotoxicity. Moreover, DMDH soaked in filter paper was used to create qualitative test strips and visually identify Cu2+ and glyphosate through significant color changes. Furthermore, smartphone RGB color recognition provided a new method for semi-quantitative testing of Cu2+ and glyphosate in the absence of expensive instruments.