An enzymatic ratiometric fluorescence assay for 6-mercaptopurine by using MoS2 quantum dots

A novel turn-on fluorescence sensor based on the Nd (III) complex for the ultrasensitive detection of 6-mercaptopurine

6-mercaptopurine (6MP) is a chemotherapeuticdrug widely used for treating inflammatory bowel diseases and several cancers. Nevertheless, determining and monitoring its concentration in the human body is highly important because over or under-doses of 6MP can lead to critical health issues. In this paper, we have developed a turn-on fluorescent probe for the determination of the anticancer drug 6-mercaptopurine (6-MP) based on coordination complex [Nd (Anth)3 (H2O)3]. [Nd (Anth)3 (H2O)3] has been synthesized through a simple precipitation process taking the stoichiometric ratio of Nd (III) nitrate hexahydrate and 2-aminobenzoic acid (2-ABA), commonly known as anthranilic acid (Anth). The synthesis and structure have been investigated and validated by different characterizations like UV-visible spectroscopy, FT-IR, HRMS, XPS, and SEM. The synthesized complex displayed excellent fluorescence properties, and the fluorescence intensity was enhanced with the addition of 6MP in the form of a [Fe (6MP)3]2+ mixed complex (Fe-6MP), which is formed by dissolving it in FeCl3. The fabricated sensors displayed the best linear response in a wide range of concentrations from 2.55 μM to 45.51 μM of 6MP. The lower limit of detection (LOD) of the developed sensor was found to be 0.26 μM with a linear correlation coefficient (R2) of 0.99. The synthesized probe gives an acceptable response for the sensing of 6MP in the presence of several interfering agents.

Magnetic nanoparticles based on cerium MOF supported on the MWCNT as a fluorescence quenching sensor for determination of 6-mercaptopurine

In this study, a new magnetic nanocomposite was developed as an efficient and fast-response fluorescence quenching sensor for determination of anticancer drug 6-mercaptopurine (6-MP). For this purpose, the needle-shape fluorescence metal-organic framework of cerium (Ce-MOF) were successfully synthesized on the surface of multiwalled carbon nanotubes using 1,3,5-benzenetricarboxylic acid ligand via a facile solvothermal assisted route and magnetized. The accuracy of the proposed synthesis was confirmed using the FT-IR, FE-SEM, XRD, and VSM methods. The obtained product as presented the fluorescence emission in 331 nm by excitation of 293 nm in excitation/emission slit widths of 10.0 nm. The operation of suggested method is based on quenching the fluorescence signal in accordance with increasing the 6-MP concentration. The proposed assay effectively detected the trace amount of 6-MP in the linear range of 1.0 × 10^-6 to 7 × 10^-5 M. The limit of detection and limit of quantification were obtained as 8.6 × 10^-7 and 2.86 × 10^-6 M, respectively. The analyte molecule was determined in real samples with satisfactory recoveries between 98.75 and 105.33.

Intrinsic Dual-Emitting Carbon Quantum-Dot-Based Selective Ratiometric Fluorescent Mercaptopurine Detection

Mercaptopurine (6-MP), an immunosuppressive drug, has been widely prescribed for treating leukemia and autoimmune diseases. The level of the 6-MP drug in body fluids is of great interest due to the severe health problems related to its overdose. This study used a facile microwave preparation route to synthesize carbon quantum dots (CQDs) using glutathione and formamide as carbon sources. The obtained monodispersed quantum dots showed dual fluorescence emission with a sensitive affinity toward the 6-MP drug. The sensor's response was optimized by tuning the temperature, pH, and volume ratio of the probe. The prepared ratiometric fluorescence method showed accurate measurements for determining mercaptopurine in aqueous solutions in the concentration range of 1.4-7.6 mg L^-1 with the limit of detection of 1.3 mg L^-1. The sensor's performance was assessed in complex solutions, human urine, and human plasma sample and recovery values in the range of 88-127% were obtained. The reliable dual fluorometric sensor showed promising results for 6-MP determination and potential application for the determination of other chemical and biochemical species.

Ratiometric fluorescence immunoassay based on MnO2–o-phenylenediamine–fluorescent carbon nanodots for the detection of α-fetoprotein via fluorescence resonance energy transfer

The ratiometric fluorescence immunoassay based on MnO2–o-phenylenediamine–fluorescent carbon nanodots is superior to the traditional single-wavelength-based method.

A MnO2 nanosheet-assisted ratiometric fluorescence probe based on carbon quantum dots and o-phenylenediamine for determination of 6-mercaptopurine

A MnO₂ nanosheet-assisted ratiometric fluorescence probe based on carbon quantum dots (CQDs) and o-phenylenediamine (OPD) has been developed for the detection of the anticancer drug 6-mercaptopurine (6-MP). CQDs with strong fluorescence are synthesized via the one-step hydrothermal method. MnO₂ nanosheets as an oxidase-mimicking nanomaterial directly oxidize OPD into 2,3-diaminophenazine (DAP) which has a fluorescence emission at 570 nm, whereas the fluorescence of CQDs at 445 nm is then reduced by the DAP through the inner filter effect (IFE) under a single excitation wavelength (370 nm). After adding 6-MP, MnO₂ nanosheets can be reduced to Mn²⁺ and lose their oxidase-like property, blocking the IFE with the fluorescence decrease of DAP and fluorescence increase of CQDs. The novel ratiometric fluorescence probe exhibits considerable sensitivity toward 6-MP and linear response is in the 0.46-100.0 μmol L^-1 concentration range with the detection limit of 0.14 μmol L^-1. Furthermore, the probe shows good selectivity when exposed to a series of interfering other organic and inorganic compounds, and biomolecules and can be applied to the detection for 6-MP in human serum samples and pharmaceutical tablets. Satisfactory recoveries of 6-MP in human serum samples are in the range 96.1-110.9% with the RSD of 1.4 to 3.2%. The amount of 6-MP is successfully estimated as 49.3 mg in pharmaceutical tablet with the RSD of about  2.2%.

Application and Analysis of 6-Mercaptopurine Nanomedicine in the Treatment of Leukemia

As a first-line drug widely used in the treatment of leukemia, 6-MP has obvious effects on leukemia. However, 6-MP disadvantages such as poor solubility in water, easy binding with serum proteins, short circulation time, and large toxic and side effects greatly limit the application of 6-MP. For this reason, various 6-MP nano drug-loading systems have been designed to increase the water solubility of 6-MP, extend the circulation time, and increase the bioavailability of 6-MP to a certain extent, reducing its toxic and side effects. However, its therapeutic effect in vivo and in vitro is still far from expectations, and there is a lot of room for improvement. In order to solve the above problems encountered in the clinical application of 6-MP, we have tried two ways of polymer prodrugs and drug-loaded vesicles to achieve efficient targeted delivery and treatment of 6-MP. We designed hyaluronic acid (HA)-based gluteal-skin-responsive 6-MP polymer prodrug (HA-GS-MP) for highly effective targeted therapy of acute myeloid leukemia. Hyaluronic acid is a natural polysaccharide, which has excellent biocompatibility and biodegradability, and has a good ability to actively target malignant tumor cells overexpressing the CD₄₄ receptor. 6-MP is connected to the HA chain through a vinyl sulfide bond, which is stable under physiological conditions (no drug release), and under intracellular reducing conditions, the connection bond is broken and 6-MP is quickly released. HA-GS-MP has a simple preparation process, good water solubility, long cycle time, and strong targeting ability. This GSH-responsive CD₄₄ targeted 6-MP polymer prodrug is expected to improve the therapeutic effect on acute myeloid leukemia cells.

A novel hybrid fluorescence probe sensor based on metal-organic framework@carbon quantum dots for the highly selective detection of 6-mercaptopurine

In the present study, MIL-101(Fe) and amine-carbon quantum dots (CQDs) were combined via a post-synthetic modification (PSM) method; thus, a novel MIL-101(Fe)@amine-CQD hybrid fluorescent probe sensor for the detection of 6-mercaptopurine (6-MP) was synthesized. Amine-CQDs as a fluorescent material can convert the bonding interaction between MIL-101(Fe) and 6-MP into recognizable fluorescence signals, and MIL-101 (Fe) as an adsorbent can pre-concentrate 6-MP. Hereupon, this new sensor demonstrates high selectivity and sensitivity towards the detection of 6-MP. The addition of 6-MP to this probe quenches the fluorescence signal at 599 nm. In this study, factors such as pH, response time, and concentration of MIL-101(Fe)@amine-CQDs were optimized by the one-factor-at-a-time (OFAT) method. Under optimal conditions, the relationship between the fluorescence enhancement factor and the concentration of 6-MP for this sensor in the range of 0.1667-1.0000 μg L^-1 was linear (R² = 0.9977, n = 3). The limit of detection and limit of quantitation were 55.70 ng L^-1 and 202.06 ng L^-1, respectively, which are better than similar techniques. The repeatability of intra-day and inter-day was 2.4% and 4.7%, respectively. This fluorescent sensor was employed to determine 6-MP in real samples and exhibited acceptable results.

Ratiometric fluorescent nanoprobe based on CdTe/SiO2/folic acid/silver nanoparticles core-shell-satellite assembly for determination of 6-mercaptopurine

A sensitive and robust fluorescent assay of 6-MP is described which relies on the facile assembly of a fluorescence nanoprobe by design of silica nanosphere encapsulated CdTe quantum dots (CdTe QDs) as scaffold, coupling with chemically tethered folic acid (FA)-protected silver nanoparticles (AgNPs) that function as responsive element. In this way a stable ternary core-shell-satellite nanostructure with dual-emission signals can be established. On binding to the target molecules, 6-MP, FA molecules initially occupied by AgNPs are liberated to give dose-dependent fluorescence emission, which can further form a self-calibration ratiometric fluorescence assay using CdTe QDs as an internal reference. The nanoprobe color vividly changes from red to blue, enabling the direct visual detection. The linear concentration range is 0.15~50 μM with the detection limit of 67 nM. By virtue of the favorable selectivity and robust assays, the nanoprobe was applied to 6-MP detection in urine samples, with recoveries from 97.3 to 106% and relative standard deviations (RSD) less than 5%. Graphical abstract.

A ratiometric fluorometric ciprofloxacin assay based on the use of riboflavin and carbon dots

Carbon dots (CDs) were hydrothermally synthesized from selenious yeast. They were further coupled with riboflavin to form a dually emitting probe for ciprofloxacin (CIP). Under 370 nm excitation, the probe displays dual (blue and green) emissions with peaks at 443 and 510 nm. When CIP is added, the blue fluorescence of the CDs is enhanced while the green fluorescence remains unaffected. The ratio of the relative fluorescence intensities at 443 and 510 nm increases linearly in the 0.5-200 μM CIP concentration range. The fluorescent probe is selective and has a 0.13 μM detection limit. Satisfactory recoveries (97.9-101.1%) were received when the probe was used to quantify CIP in spiked water and human serum samples. Graphical abstractBlue-emissive carbon dots were prepared from selenious yeast via a hydrothermal method, and then coupled with riboflavin as a ratiometric fluorometric probe for ciprofloxacin determination.

Ratiometric fluorescent immunoassay for the cardiac troponin-I using carbon dots and palladium-iridium nanocubes with peroxidase-mimicking activity

A nanozyme-linked immunosorbent assay is described for cardiac troponin I which is a biomarker for myocardial infarction. The method is based on the use of Pd-Ir nanocubes with excellent peroxidase-like activity. The nanocubes catalyze the oxidization of nonfluorescent o-phenylenediamine (OPD) by H₂O₂ to form a yellow fluorescent product (oxOPD) with excitation/emission maxima at 400/570 nm. Carbon dots are added as a reference fluorophore. Under the same excitation wavelength, they display blue fluorescence (450 nm). The ELISA uses the Pd-Ir nanocubes as a label for the secondary antibody and OPD as substrate. The ratio of fluorescence intensities at 570 and 450 nm increases in the 1 pg·mL^-1 to 1 ng·mL^-1 cardiac troponin I concentration range, and the detection limit is 0.31 pg·mL^-1. The method was applied to analyze spiked serum samples, and the results compared well with those obtained by a commercial chemiluminescence assay. Graphical abstract Schematic presentation of the ratiometric fluorescence immunoassay for cardiac troponin-I. Pd-Ir nanocubes were employed to fabricate nanozyme-based signal labels for its excellent peroxidase-mimicking activity.

A label-free fluorescent sensor based on silicon quantum dots–MnO2 nanosheets for the detection of α-glucosidase and its inhibitor

We have successfully designed a fluorescence SiQD–MnO₂ nanosheet sensing platform to detect α-glucosidase and acarbose for the first time.