Probe Solution Research Articles

Development of a novel fluorescent probe for the detection of glyphosate in food and water samples and the construction of a smartphone-assisted platform.

The extensive use of glyphosate has been a severe threat to the environment and human health, which highlights the importance of the detection of glyphosate in various environmental and food samples. Herein, a novel fluorescent probe (DT-Gly) was constructed for the detection of glyphosate. DT-Gly and glyphosate binding to copper ions (Cu2+) is competitive. Therefore, the increased glyphosate will decrease DT-Gly binds to Cu2+. Accordingly, the absorbance (at 507nm) and fluorescence (at 580nm) intensity of DT-Gly showed excellent linear relationships with glyphosate concentrations (0-20μM). Moreover, the detection limits of DT-Gly for Cu2+ and glyphosate were 94nM and 71nM, respectively. DT-Gly was successfully applied to detect glyphosate in food samples and water samples. We further constructed a convenient platform for the detection of glyphosate by analyzing the changes in RGB values of the probe solution and test strips using a smartphone.

Semiclassical quantization of M5 brane probes wrapped on AdS3× S3 and defect anomalies

We consider two supersymmetric M5 brane probe solutions in AdS7 × S4 and one in AdS4 × S7 that all have the AdS3 × S3 world-volume geometry. The values of the classical action of the first two M5 probes (with S3 in AdS7 or in S4) are related to the leading N2 parts in the anomaly b-coefficient in the (2,0) theory corresponding to a spherical surface defect in symmetric or antisymmetric SU(N) representations. We present a detailed computation of the corresponding one-loop M5 brane partition functions finding that they vanish (in a particular regularization). This implies the vanishing of the order N0 part in the b-anomaly coefficients, in agreement with earlier predictions for their exact values. It remains, however, a puzzle of how to reproduce the non-vanishing order N terms in these coefficients within the semiclassical M5-brane probe setup.

Development of diselenide-based fluorogenic system for the selective and sensitive detection of the Hg(II) in aqueous media.

Mercury(II) is highly toxic thus the selective and sensitive detection of Hg(II) is important. This research article deals with the synthesis and characterization of the fluorogenic system based on diselenide containing rhodamine by single crystal XRD. The probe has been used for selective detection of Hg(II) in aqueous media with detection limit of 62.3 nM. The reaction of the Hg(II) with the probe induces opening of the spirolactam ring triggering fluorescence turn-on response. This reaction causes color change of the probe solution from colorless to pink. In addition, the probe showed the reversible binding behavior with Hg(II) and S2-. The effectiveness of the probe was evaluated using prostate cancer cell line through live cell imaging.

Solute Energetics in Aqueous Xanthan Gum Solutions: What Can Be Learned from a Fluorescent Probe?

Xanthan gum (XG) is a well-known anionic polysaccharide that finds broad application in the food and petroleum industries because of its ability to enhance solution viscosity at low concentrations and moderate temperatures. The aim of this work was to use the solvation probe coumarin 153 (C153) to characterize changes in the xanthan gum (XG) solution microstructure as a function of XG concentration and temperature from the perspective of a dissolved solute molecule. We established the utility of C153 fluorescence to track solution changes for XG concentrations that span the transition region from a dilute to a semi-dilute solution, defined by the xanthan gum overlap concentration, C*~0.02 g/dL. The temperature was varied from 293 to 353 K to probe solution conditions wherein XG has been reported to undergo a structural change from helix to random coil conformation, the details of which are still under debate. While C153 fluorescence does not elucidate direct structural information, the emission response is a simple means by which changes in aqueous XG solution can be identified. C153 spectroscopy is observed to correlate with XG conformational changes, as reported in the literature.

A Novel Method for Mitochondrial Membrane Potential Detection in Heart Tissue Following Ischemia-reperfusion in Mice.

Myocardial ischemia-reperfusion (I/R) injury is associated with a significant reduction in the mitochondrial membrane potential (MMP, ΔΨm). Fluorescence-based assays are effective for labelling active mitochondria in living cells; their application in heart tissue, however, represents a challenge because of a low yield of viable cardiomyocytes after cardiac perfusion. This study aimed to examine a novel method for detecting the changes in the MMP of mouse heart tissue following I/R injury. The I/R model was established, which was characterized by distinct ischemic area and apoptosis in heart tissue. The MMP was detected via a confocal microscope after the ascending aorta was clamped and the mitochondrial probe solution (containing Mito-Tracker Deep Red FM) was perfused from the apex via a peristaltic pump. This method enabled the distribution of the probe solution throughout the cardiac tissue via the coronary circulation. Fluorescence detection revealed that the MMP was profoundly reduced in both ischemic area and border area following I/R when compared with that in the sham group. There was no obvious difference in the MMP of the remote area between the I/R group and the sham group. This study presents a novel method for detecting the MMP in heart tissue, and this method will facilitate the evaluation of changes in the MMP in different regions following I/R.

CoFe2O4-Chitosan and Gold Nanoparticles Based Label-Free Electrochemical Immunosensor for Determination of Leptin

Herein, a label-free electrochemical leptin immunosensor was demonstrated. The sensing platform consists of the immobilizing of the anti-leptin antibody on a glassy carbon electrode (GCE) modified with cobalt iron oxide (CoFe2O4) nanoparticles, chitosan (CHI), and gold nanoparticles (AuNPs). A simple and rapid leptin determination was achieved by measuring the change of current response in a redox probe solution before and after the immunocomplex formation. SEM examined the surface morphologies of the prepared electrodes. The electrochemical performance of the leptin immunosensor was commented on via EIS, CV, and DPV. Under optimized circumstances, a linear response was found between the current peaks acquired from DPV and the logarithm concentration of leptin in the range of 1─4000 ng mL-1 with a detection limit (LOD) of 0.1 ng mL-1. The subjected immunosensor demonstrated satisfactory reproducibility.

Detection of dithiocarbamate pesticide residues in tea by colorimetric and fluorescent double-mode probe regulated by tyrosinase

In this study, a colorimetric/fluorescent double-mode probe for sensitive detection of dithiocarbamates (DTCs) pesticides residues was constructed based on the fluorescence controllable property of Mn3+-sealed metal-organic framework (MnMOF), the chromogenic reaction of enzyme reaction products, and inhibition of tyrosinase activity by DTCs. DTCs inhibited the activity of tyrosinase and impeded the consumption of catechol (CC), thereby weakening the colorimetric signal. The redox reaction between residual CC and MnMOF led to backbone collapse and release of free porphyrin (TCPP), which caused fluorescence enhancement of the probe solution. As the concentration of DTCs increased, the color of probe solution gradually transitioned from reddish brown to light pink in daylight, and the red fluorescence was gradually enhanced under 365 nm UV light. Under the optimal conditions and using zineb as a representative of DTCs, the probe achieved the sensitive response to zineb over the concentration range of 0.03 ∼ 1.1 μg mL−1. The detection limits were 9.23 ng mL−1 and 5.95 ng mL−1 in colorimetric and fluorescent modes, respectively. The practical applicability of the probe was demonstrated by the detection of zineb residues in tea. In this study, a simple, sensitive, and reliable double-mode analysis platform was established for the identification of DTCs residues in tea, which is of great significance for ensuring the quality and safety of tea and human health.

Tailoring a chromogenic diketopyrrolopyrrole based probe for cyanide ion detection-applications in capsules and Arduino programming device

Though some anions are essential to our body’s metabolic processes, even in very little amounts, the cyanide ion is exceedingly toxic and harmful to people, animals, and the environment. A diketopyrrolopyrrole and benzaldehyde based moieties as binding sites has been developed and characterized by DFT and various spectral methods to detect cyanide ions. This probe DPP (4′-(2,5-diethyl-3,6-dioxo-2,3,5,6-tetrahydropyrrolo[3,4-c]pyrrole-1,4-diyl) dibenzaldehyde) shows impressive detection signals together with an easysynthesis procedure, quick reaction time, extraordinary selectivity, and good sensitivity. The orange color of the probe solution turns colorless when cyanide ion solution is added, making cyanide ion recognition visible to the naked eye. Crucially, the probe did not exhibit any signs of interference from possibly competitive ions, indicating its biological compatibility, with a detection limit of 1.03 μM (UV–vis) and 5.84 nM (fluorescence) for the cyanide ion recognition. The HRMS data demonstrate that the probe works with an addition reaction mechanism to bind with cyanide ion. The range of applications for cyanide probes is greatly increased as a result of its ability to sense cyanide ions effectively in variable matrices, including test strips, water, polysulfone capsules, and electronic Arduino devices.

Diamine-functionalized zirconium metal-organic cage ZrT-1-(NH2)2: A ratiometric fluorescent probe for the rapid and sensitive detection of malachite green

Malachite green (MG), a cost-effective triphenylmethane dye known for its insecticidal and germicidal properties in aquaculture, unfortunately poses significant environmental and human health-related risks due to its mutagenic, carcinogenic, and teratogenic effects. Herein, a novel diamine-functionalized zirconium-based metal organic cage (Zr-MOC), abbreviated as ZrT-1-(NH2)2, was synthesized through microwave-assisted method, serving as a ratiometric fluorescent sensor for the precise detection of MG in aquaculture water. When the pH value was adjusted to 3.0, the probe solution exhibited two distinct characteristic emission bands centered at 454 nm and 582 nm, upon excitation at 365 nm. With the addition of MG, the emission intensity at 582 nm was significantly quenched, whereas the fluorescence intensity at 454 nm was gradually increased. The related experimental data and DFT calculations revealed that the quenching process is predominantly governed by the inner filter effect and static quenching mechanisms. Notably, the ratiometric fluorescence probe exhibited a good linear correlation with the MG concentration within the range of 1.37–17.81 nM, boasting a remarkably low detection limit of 1.05 nM. Furthermore, the proposed ZrT-1-(NH2)2 ratiometric fluorescence probe features high recoveries (95.37–104.93 %) and low relative standard deviations (RSD<3.5 %) for the detection of trace MG in aquaculture water, indicating its feasibility and practicality for MG detection.

Green synthesis of thiadiazole Schiff bases and specific recognition of Cr2O72−, SiO32− and S2−

Sulfide (S2−), silicate (SiO32−) and dichromate (Cr2O72−) ions are prevalent contaminants in industrial effluents, and their rapid and accurate detection is of critical importance for environmental monitoring. In this study, we utilized an environmentally friendly, highly efficient, and biodegradable deep eutectic solvent (DES) to catalyze the synthesis of 2-(((5-phenyl-1,3,4-thiadiazol-2-yl)imino)methyl)phenol (Probe M). Probe M exhibits excellent selectivity for S2−, SiO32− and Cr2O72−, and the corresponding color changes can be readily detected by the naked eye. Upon addition of S2− and SiO32− to the probe solution, the solution turns a distinct orange-red, while the addition of Cr2O72− results in a pronounced darkening of the solution. The detection of S2− and SiO32− by probe M under alkaline condition is stable, and the detection of Cr2O72− under acidic condition is stable. Fluorescence titration experiments revealed that probe M forms a 1:2 stoichiometric complex with S2−, SiO32− and Cr2O72−, with binding constants of 3.84 × 104 M−1, 1.86 × 104 M−1 and 3.19 × 104 M−1, respectively. The detection limits were determined to be 1.76 × 10−4 M for S2−, 9.15 × 10−5 M for SiO32−, and 2.13 × 10−4 M for Cr2O72−. The dipstick experiment demonstrates the probe M can be used as a solid-state sensor to identify S2−, SiO32− and Cr2O72−.

A Highly Selective Fluorescent “Turn on” Probe for Al3+ Based on Pyrazolone

AbstractA highly selective fluorescent “turn on” probe for Al3+ based on the conjugate of aminourea and pyrazolone was devised and synthesized. The fluorescence intensity of the probe solution was significantly enhanced by the addition of Al3+ to the probe solution. Other cations such as Cu2+, Ni2+, Fe3+, Co2+, Ag+, Mn2+, Sn2+, Sn4+, Mg2+, Li+, Zn2+, Zr4+, Ce3+, Ca2+, and Na+ did not interfere the detection of Al3+. The 1 : 1 complexation between Al3+ and the probe was confirmed by Job's plot curve. In addition, the solution of the complex formed by Al3+ and the probe can be used for the specific detection of Hg2+, appearing as fluorescence quenching.

A promising platform for the rapid and sensitive sensing of mercury ion and its applications in biological and environmental system

Mercury ion (Hg2+) is one of harmful heavy metal ions that can accumulate inside the human organism and cause some health problems. Herein, a novel NBD derivative, 1-(2-((7-nitrobenzo[c] [1,2,5] oxadiazol-4-yl) amino) ethyl)-3-phenylthiourea (NBD-SCN), has been reasonably designed, which was simply synthesized by introducing NBD moiety as the fluorophore, phenyl-isothionitrate as the reaction site and ethylenediamine as a linker group, resulting in intense fluorescence emission with high fluorescence quantum yields. Intriguingly, probe NBD-SCN provides a dual-mode colorimetric and fluorescence response pattern for the sensing of mercury ion with great limit of detections (3.6 nM) and rapid response time (4 s). The strong combination of mercury ions and sulfur atoms leads to intramolecular cyclization, causing the color of probe solution changed from orange to pale yellow as well as a complete vanishing of fluorescence intensity. The proposed reaction mechanism was verified by fluorescence and UV titration, 1H NMR, FTIR, HRMS analyses and DFT studies. Motivated by an impressive chromatic variation, test strip sensing platform are facilely constructed for real-time and on-site measurement of Hg2+ levels. Furthermore, confocal imaging experiments verify that this probe can be used for monitoring mercury ion in living mung bean sprouts and in biological systems in real time.

Selective Detection of Divalent Cations (Cu2+, Zn2+, Pb2+) and Anions (SO42-, S2-, CO32-) Using a pH-Sensitive Multi-functional Schiff Base inNeutralMedium.

A new Schiff base-based multi-cation/anion probe (L) has been synthesized and characterized using HR-MS, FT-IR, 1H, and 13C NMR techniques. The Schiff base motif provides specific binding sites that detect cations and anions by generating distinct optical output signals upon interaction. A noticeable color change of the probe solution was observed from pale yellow to various shades of yellow upon adding cations such as Cu2+, Zn2+, and Pb2+ and anions such as CO32⁻, S2⁻, and SO42⁻. This color change results from forming complexes like M3L2 with metal ions. Whereas origin of color in presence of anion were attributed due to the deprotonation of acidic proton in the ligand. Moreover, the complexes formed by Zn2+, S2/CO32⁻ ion with L are fluorescent, enabling the detection of Cu2+ and SO42⁻ using the Stern-Volmer plot, with a limit of detection (LODs) of 8.48µM and 10.47µM, respectively. Additionally, increasing the pH of the probe solution above 8 reveals a significant enhancement of fluorescence intensity due to the deprotonation of phenolic -OH and amide -NH in the presence of hydroxide ions. This emission in the basic medium is quenched by Cu2+ ions and restored when Cu2+ is complexed with EDTA. A logic gate has also been constructed for understanding the TURN-OFF-TURN-ON mechanism involving Cu2+ ions and EDTA. Overall, the versatile performance of a single probe L opens up new possibilities as a multifunctional sensor, making it highly suitable for practical applications.

A Turn‐On Fluorescence Probe Based on a New Salamo‐Co (II) Coordination Polymer for Tyrosine Detection and Its Application in Water Samples

ABSTRACTA novel salamo‐Co (II) coordination polymer probe CP was synthesized firstly, and its crystal structure, [Co3(L)2(PTA)(H2O)2]n·4nDMF, was determined by X‐ray diffraction analysis. The probe has a rare aggregation‐induced luminescence enhancement (AIEE) effect. When applied to amino acid detection, it was found to have a high selective recognition of tyrosine. With the increase of tyrosine, the fluorescent strength of the probe was enhanced in a short period of time. In addition, the binding ratio of probe to Tyr was determined by fluorescence titration experiment, and the detection limit LOD of probe CP for Tyr was calculated to be 2.57 × 10−9 M, and the binding constant Ka was 2.96 × 105 M−1. According to UV absorption spectrum, FT‐IR spectra, ESI mass spectrometry, and DFT calculation, it was speculated that Tyr can bind to the probe after adding Tyr into the probe solution, triggering FRET and ICT effects, resulting in increased fluorescence intensity and blue shift, and finally achieving the specific recognition of tyrosine by probe CP. Finally, the practical application of probe CP was studied. Through strip test and real water sample test, it was found that the probe can be used for qualitative and quantitative analysis of tyrosine.

Turn-On Fluorescence Probe for Cancer-Related γ-Glutamyltranspeptidase Detection.

The design and development of fluorescent materials for detecting cancer-related enzymes are crucial for cancer diagnosis and treatment. Herein, we present a substituted rhodamine derivative for the chromogenic and fluorogenic detection of the cancer-relevant enzyme γ-glutamyltranspeptidase (GGT). Initially, the probe is non-chromic and non-emissive due to its spirolactam form, which hinders extensive electronic delocalization over broader pathway. However, selective enzymatic cleavage of the side-coupled group triggers spirolactam ring opening, resulting in electronic flow across the rhodamine skeleton, and reduces the band gap for low-energy electronic transitions. This transformation turns the reaction mixture from colorless to intense pink, with prominent UV and fluorescence bands. The sensor's selectivity was tested against various human enzymes, including urease, alkaline phosphatase, acetylcholinesterase, tyrosinase, and cyclooxygenase, and showed no response. Absorption and fluorescence titration analyses of the probe upon incremental addition of GGT into the probe solution revealed a consistent increase in both absorption and emission spectra, along with intensified pink coloration. The cellular toxicity of the receptor was evaluated using the MTT assay, and bioimaging analysis was performed on BHK-21 cells, which produced bright red fluorescence, demonstrating the probe's excellent cell penetration and digestion capabilities for intracellular analytical detection. Molecular docking results supported the fact that probe-4 made stable interactions with the GGT active site residues.

Green florescent carbon dots synthesized from various household green wastes for detection of parathion methyl pesticide

The purpose of the current study was to examine the use of green household wastes, such as lemon peel, bottle gourd peel (BG), culinary banana peel, and sugarcane bagasse, as a source for synthesizing carbon dots (C-dots) and to determine how the composition of the material affected the functional characteristics of the C-dots and its interaction behaviour for detection of pesticide. The synthesized C-dots showed green fluorescence with varying particle sizes and red shifting fluorescence with more than 100 nm Stokes shift, indicating time and excitation dependent luminescence behaviour. C-dots produced from bottle gourd (BG) peel had a positive impact on the functional characteristics with a maximum emission of 514 nm and excitation of 410 nm. The SAED and TEM pattern confirmed its amorphous structure. The hydronium ion diameter and the quantum yield were 0.99 nm and 3.1 % respectively. Contributing towards food safety, the synthesized C-dots from BG showed significant behaviour in the detection of parathion methyl (MP) like organophosphorus pesticide (OP) as it conjugated with iron and 1 ppm of parathion methyl, which exhibited “Turn-Off-On” fluorescence behaviour with noticeable changed in intensity and act as a promising qualitative tool for detection of parathion methyl in real sample. The intensity of FL and concentration of OP is directly proportional which is established by the investigated OP in vegetable, fruit and water samples. The significance of iron and MP-OP was also investigated in the presence of other metal ions and pesticides and showed that the C-dots synthesized probe solution was reliable and sensitive towards the detection of MP-OP in real samples.

Development of biochromic paper strips from cellulose nanocrystals and anthocyanin extract from pomegranate (Punica granatum L.) for colorimetric determination of urea

AbstractAn anthocyanin (ACN) spectroscopic probe was extracted and immobilized into a matrix of cellulose nanocrystals (CNC)/urease enzyme to create a colorimetric nanocomposite film sensor. The ACN@CNC composite is a disposable molecular biosensor that uses urease as a catalyst, ACN as a molecular probe, and CNC as a probe carrier with a high surface area. The ACN spectroscopic probe was isolated from the pomegranate peel (Punica granatum L.). A mordant was applied to fix ACN onto CNC by forming nanoparticles (6–14 nm) of mordant/ACN (M/ACN) complexation. CNC showed diameters in the range of 11–21 nm, and crystal lengths of 55–130 nm. Under acid/base conditions, the ACN probe solution in distilled water exhibited a reversible color change, as shown by the UV–Vis absorption spectra. In order to create a biocomposite film, CNC were reinforced with a sodium alginate biopolymer. Upon exposure to urea in an aqueous solution, the ACN@CNC film biosensor changes color from purple (598 nm) to white (432 nm). The detection limit of urea was determined at 25–450 ppm. Various methods were utilized to investigate the morphological properties of CNC and ACN@CNC films.

A highly effective curcumin-based fluorescent probe with single-wavelength excitation for simultaneous detection and bioimaging of Cys, Hcy and GSH

Cysteine (Cys), homocysteine (Hcy) and glutathione (GSH) act as significant roles in many physiological processes, and their abnormal proliferation will cause multiple diseases including Alzheimer’s disease, Parkinson’s disease, Cardiovascular disease, atherosclerosis, and soft tissue damage. However, It is challenging work to develop a efficient method for differentiating and detecting GSH, Cys and Hcy because of their significant similarity in structures and functions. In this work, a smart fluorescent probe FBCN based on curcumin was rationally devised and developed by etherifying the phenol hydroxyl group on FBC with NBD-Cl, which emitted strong green at 516 nm. FBCN distinguished Hcy from Cys/GSH with naked eyes based on the color variation of probe solution in sunlight. Meanwhile, GSH induced the powerful fluorescence quenching of probe solution, but the fluorescence color of FBCN solution transformed from green to luminous yellow accompanied with emission wavelength redshifted from 516 nm to 540 nm or 553 nm in the existence of Hcy and Cys, respectively. Probe FBCN had outstanding sensitivity and anti-interference, low detection limit (56.5 nM, 77.7 nM, and 288 nM corresponded to Cys, Hcy, and GSH, respectively), short response time (the response time of FBCN to Cys, Hcy and GSH was 1 min, 2 min and 5 min, respectively). The DFT calculation and HRMS had verified the sensing mechanism of FBCN to biothiols. In addition, the probe was successfully utilized to detect three biothiols levels in living cell and zebrafish.

A ratiometric fluorescent probe for the detection of γ-glutamyl transpeptidase activity and its application in garlic

A novel ratiometric fluorescent probe for the detection of γ-glutamyl transpeptidase (GGT) activity was developed. The recognition of GGT by this probe is achieved by its enzymatic hydrolysis of peptide bonds in the probe. Under optimized conditions, the probe exhibited obvious ratiometric fluorescence responsiveness after interaction with GGT, avoiding potential background interference. The linear concentration range was 0.0350–2 U / mL, with good selectivity and stability. Under a 365 nm UV lamp, as the concentration of GGT increased, the probe aqueous solution gradually changed from dark blue to light blue. In addition, the B/G value of the probe's solution and the GGT activity were linearly correlated. More significantly, the probe was able to effectively identify the GGT activity of garlic.

Highly selective optical and naked-eye recognition of L-cystine through spectroscopy and development of cellulose paper nano biosensor test strips for the early diagnosis of cystinuria

Accurate sensing of small biomolecules from complex biofluid media remains a challenge due to adverse interaction of metallic salts and other biofluid components. L-cystine is the most important biomarker for the disease cystinuria. Recognition of L-cystine in urine is thus fundamental for the timely detection of cystinuria and related chronic kidney disease (CKD). Poor solubility of L-cystine offer limits to design suitable sensors. Herein, we report the synthesis of thioglycolated-β-CD (TG-β-CD) anchored silver nanoparticles (AgNP) as a potential receptor (TG-β-CD⊃AgNP) for the effective optical recognition and quantification of L-cystine through UV–Vis and SERS (surface enhanced Raman spectroscopy) spectroscopic fingerprinting and suitable colourimetric naked-eye detection of L-cystine by indicator displacement assay. Methyl orange (Met-O) indicator was precomplexed with the receptor to generate the probe solution (Met-O@TG-β-CD⊃AgNP). Indicator has been exchanged from Met-O@TG-β-CD⊃AgNP by the addition of L-cystine, with an instantaneous visible colour change from yellow to red. The method is tolerable to other interfering abundant ions and biomolecules. Based on the innovative sensing assay a cellulose paper-dye test strip is developed for point-of-care detection and quantification of the biomarker. Structures of TG-β-CD, TG-β-CD⊃AgNP and Met-O@TG-β-CD⊃AgNP were elucidated by UV–Vis, FT-IR, PXRD, 1H NMR, etc. spectroscopy. Scanning electron microscopy (SEM) was used to examine the morphology of TG-β-CD, AgNP and TG-β-CD⊃AgNP. The chemical changes during the assay were evaluated by conductance, UV–Vis and SERS. The competitive displacement of the indicator and UV turn-on at ppm level analyte concentration made the process compatible for day-to-day point-of-care units.