Electrochemical determinations of 6-mercaptopurine on the surface of a carbon nanotube-paste electrode modified with a cobalt salophen complex

Synthesis of N-Doped Graphene Quantum Dots from Cellulose and Construction of a Fluorescent Probe for 6-Mercaptopurin Quantitative Detection

With cellulose as the precursor and ethylenediamine as the N source, N-doped graphene quantum dots (N-GQDs) were synthesized by a simple and feasible one-pot hydrothermal method. The whole process did noSchemet need a strong acid or strong base and avoided interference from inorganic salt residues. The whole process lasted only 3 h and avoided any complex postprocessing. Because of the outstanding optical properties of N-GQDs, a high-efficiency 6-mercaptopurine fluorescent probe based on the inner filter effect of fluorescence was established. The detection range was 0.2-60 μM and the detection limit was 0.05 μM. This method can preliminarily detect 6-mercaptopurine in human urine and avoids any sample preparation or extraction in advance and brings satisfactory results.

Electrochemistry as a Powerful Tool for Investigations of Antineoplastic Agents: A Comprehensive Review

Cancer is most frequently treated with antineoplastic agents (ANAs) that are hazardous to patients undergoing chemotherapy and the healthcare workers who handle ANAs in the course of their duties. All aspects related to hazardous oncological drugs illustrate that the monitoring of ANAs is essential to minimize the risks associated with these drugs. Among all analytical techniques used to test ANAs, electrochemistry holds an important position. This review, for the first time, comprehensively describes the progress done in electrochemistry of ANAs by means of a variety of bare or modified (bio)sensors over the last four decades (in the period of 1982-2021). Attention is paid not only to the development of electrochemical sensing protocols of ANAs in various biological, environmental, and pharmaceutical matrices but also to achievements of electrochemical techniques in the examination of the interactions of ANAs with deoxyribonucleic acid (DNA), carcinogenic cells, biomimetic membranes, peptides, and enzymes. Other aspects, including the enantiopurity studies, differentiation between single-stranded and double-stranded DNA without using any label or tag, studies on ANAs degradation, and their pharmacokinetics, by means of electrochemical techniques are also commented. Finally, concluding remarks that underline the existence of a significant niche for the basic electrochemical research that should be filled in the future are presented.

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.

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%.

Nanonetwork of Coordination Polymer AHMT-Ag for the Effective and Broad Spectrum Detection of 6-Mercaptopurine in Urine and Blood Serum

Nanocrystalline coordination polymers (NCCPs) have been considered as an incredible electrochemical sensor for the effective detection of biologically dynamic drug 6-mercaptopurine (6-MP). In the present report, a significantly stable infinite arrayed coordination polymeric network was self-assembled via metal with efficient organic tecton 4-amino-3-hydrazino-5-mercapto-1,2,4,-triazole (AHMT) in which silver(I) ions are coordinated by AHMT via hydrazino and exocyclic thiol linkage to form AHMT-Ag NCCP. An efficient and highly sensitive detection of 6-MP is attained owing to eminent electron channeling via polymeric nanocrystallite pores. An effective charge transfer leads to an interface of the AHMT-Ag nano-pores and electrolyte anchored electrode via π-π electron coupling and hydrophobic interaction. The voltammogram exposes acute redox behavior of 6-MP and discloses an impeccable illustration for the AHMT-Ag facilitated oxidation of 6-MP. This unique signature was applied in voltammetric detection of 6-MP in blood serum, human urine, and pharmaceutical formulation (tablet) by a considerable high sensitivity of 0.074, 0.058, and 0.036 μA/μM and a detection limit of 87, 97, and 37 nM, respectively. Thus, the prepared AHMT-Ag NCCP can provide a valuable platform for fabrication of highly sensitive electrochemical devices to assay biologically essential drug molecules.

A New Electrochemical Sensor for Direct Detection of Purine Antimetabolites and DNA Degradation

The development of a reliable electrochemical sensor using a hybrid nanocomposite consisting of ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate) functionalized graphene oxide (GrO-IL) and gold nanoparticles (AuNPs) stabilized by chitosan (Chit) was described. The new sensor, labelled as GrO-IL-AuNPs-Chit/CSE, exhibited an improved electrocatalytic response to cancer drugs such as purine antimetabolites (6-thioguanine, 6-mercaptopurine, and azathioprine) in a wide concentration range with a low detection limit (20-40 nmol·L^-1, S/N = 3), and satisfactory recoveries (97.1-103.0%). The sensor has been also successfully used for cyclic voltammetric study of a salmon sperm double-stranded DNA degradation and DNA-6-mercaptopurine interaction in aqueous solutions (pH 7.4).

Electrochemical Sensors Containing Schiff Bases and their Transition Metal Complexes to Detect Analytes of Forensic, Pharmaceutical and Environmental Interest. A Review

Schiff bases and their transition metal complexes are inexpensive and easy to synthesize. These compounds display several structural and electronic features that allow their application in numerous research fields. Over the last three decades, electroanalytical scientists of various areas have developed electrochemical sensors from many compounds. The present review discusses the applicability of Schiff bases, their transition metal complexes and new materials containing these compounds as electrode modifiers in sensors to detect analytes of forensic, pharmaceutical and environmental interest. In forensic sciences, Schiff bases are mainly used to analyze illicit drugs: chemical reactions involving Schiff bases can help to elucidate illicit drug production and to determine analytes in seized samples. In the environmental area, given that most methodologies provide Limit of Detection (LOD) values below the values recommended by regulatory agencies, Schiff bases constitute a promising strategy. As for pharmaceutical applications, Schiff bases represent an approach for analysis of complex biological samples containing low levels of the target analytes in the presence of a large quantity of interfering compounds. This review will show that new highly specific materials can be synthesized based on Schiff bases and applied in the pharmaceutical industry, toxicological studies, electrocatalysis and biosensors. Most literature papers have reported on Schiff bases combined with carbon paste to give a chemically modified electrode that is easy and inexpensive to produce and which displays specific and selective sensing capacity for different applications.

Two Highly Stable Luminescent Lead Phosphonates Based on Mixed Ligands: Highly Selective and Sensitive Sensing for Thymine Molecule and VO3 - Anion

Two luminescent lead phosphonates with two-dimensional (2D) layer and three-dimensional (3D) framework structure, namely, Pb₃[(L₁)₂(Hssc)(H₂O)₂] (1) and [Pb₂(L₂)_0.5(bts)(H₂O)₂]·H₂O (2) (H₂L₁ = O(CH₂CH₂)₂NCH₂PO₃H₂, H₄L₂ = H₂PO₃CH₂NH(C₂H₄)₂NHCH₂PO₃H₂, H₃ssc = 5-sulfosalicylic acid, NaH₂bts = 5-sulfoisophthalic acid sodium) have been prepared via hydrothermal techniques. The two compounds not only show excellent thermal stability but also remain intact in aqueous solution within an extensive pH range. Moreover, the atomic absorption spectroscopy analysis experiment indicates that there does not exist the leaching of Pb²⁺ ions from the lead phosphonates, which show they are nontoxic in aqueous solution. In compound 1, the Pb(1)O₄, Pb(2)O₇, Pb(3)O₄, and CPO₃ polyhedra are interlinked into a one-dimensional chain, which is further connected to adjacent chain by sharing the Hssc^2- to form a 2D layer. Interestingly, compound 1 as a highly selective and sensitive luminescent material can be used to detect the thymine molecule with a very low detection limit of 8.26 × 10^-7 M. In compound 2, the Pb(1)O₆ and Pb(2)O₅ polyhedra are interlinked into a dimer via edge sharing, which is further connected to adjacent dimer to form a tetramer via corner sharing, and such a tetramer is then interlinked into a 2D layer through bts^3- ligands; the adjacent 2D layers are finally constructed to a 3D structure by sharing the L₂ ^4- ligand. Compound 2 can be applied as an excellent luminescent sensor for sensing of VO₃ ^- anion. Furthermore, the probable fluorescent quenching mechanisms of the two compounds have also been studied.

Resonance light scattering determination of 6-mercaptopurine coupled with HPLC technique

A simple, fast, costless, sensitive and selective method of resonance light scattering coupled with HPLC was established for the determination of 6-mercaptopurine in human urine sample. In a Britton-Robinson buffer solution of pH5.5, the formation of coordination complex between 6-mercaptopurine and metal palladium (II) led to enhance the RLS intensity of the system. The RLS signal was detected by fluorescence detector at λ(ex)=λ(em)=315 nm. The analytical parameters were provided by the coupled system, the linear of 6-mercaptopurine response from 0.0615 to 2.40 μg L(-1) and the limit of detection (S/N=3) was 0.05 μg L(-1). The presented method has been applied to determine 6-mercaptopurine in human urine samples which obtained satisfactory results. Moreover, the reaction mechanism and possible reasons for enhancement of RLS were fully discussed.

Fluorescence quenching and spectrophotometric methods for the determination of 6-mercaptopurine based on carbon dots

A carbon dot-based fluorescence probe was designed for detecting 6-mercaptopurine (6-MP) via fluorescence quenching.

Selective recognition of 6-mercaptopurine based on luminescent metal-organic frameworks Fe-MIL-88NH₂

A novel and rapid spectrofluorometry method for the recognition of 6-mercaptopurine (6-MP) has been developed based on luminescent metal-organic frameworks Fe-MIL-88NH2 as fluorescent probe. The strong fluorescence of Fe-MIL-88NH2 at 430 nm could be quenched by 6-MP directly, and the Fe-MIL-88NH2 shows high selectivity for 6-MP compared to other thiol-containing amino acids such as homocysteine (Hcy), cysteine (Cys), glutathione (GSH), etc. Under optimal conditions, the relative fluorescence intensity was linearly proportional to the concentration of 6-MP in the range of 5-600 μM with the detection limit at 1.17 μM (S/N=3). Furthermore, the present approach has been successfully applied to the determination of 6-MP in human serum samples. The possible fluorescence quenching mechanism has also been investigated, where it is revealed that the quenching was attributed to competition of absorption of the light source energy as well as electron transfer between Fe-MIL-88NH2 and 6-MP.

Spectrophotometric Determination of 6-Mercaptopurine in Pharmaceutical Sample Using Fe(III)-Potassium Ferricyanide System

In the present work,we developed a simple,fast,sensitive and inexpensive method to determine 6-mercaptopurine (6-MP) in pharmaceutical sample using Fe (III)-potassium ferricyanide system by spectrophotometry.The results show that in acid medium, Fe (Ш) can be reduced to Fe (II) by hydrosulfuryl (-SH) in 6-Mercaptopurin molecule, and then Fe (II) reacts with potassium ferricyanide to form a soluble Prussian blue (KFeIII[FeII(CN)6]),the content of 6-MP was determinated indirectly through determinating the absorbance of the soluble Prussian blue.The various effect factors on the determination of 6-MP by spectrophotometry using potassium Fe (III)-ferricyanide system were investigated in detail.The maximum absorption wavelength of chromogenic system was 755 nm, good linear relationship was obtained between the absorbance and the concentration of 6-MP in the range of 0.4120~2.884 μ g·/mL,the equation of the linear regression was A=0.0411+0.1462C (μ g·/mL),with a linear correlation coefficient was 0.9991.This proposed method had been successfully applied to determinate of 6-MP in real pharmaceutical,and the results agreed well with those obtained by pharmacopoeial method.

Decrease in cytotoxicity of copper-based intrauterine devices (IUD) pretreated with 6-mercaptopurine and pterin as biocompatible corrosion inhibitors

The copper intrauterine device (IUD) based its contraceptive action on the release of cupric ions from a copper wire. Immediately after the insertion, a burst release of copper ions occurs, which may be associated to a variety of side effects. 6-Mercaptopurine (6-MP) and pterin (PT) have been proposed as corrosion inhibitors to reduce this harmful release. Pretreatments with 1 × 10(-4) M 6-MP and 1 × 10(-4) M PT solutions with 1h and 3h immersion times were tested. Conventional electrochemical techniques, EDX and XPS analysis, and cytotoxicity assays with HeLa cell line were employed to investigate the corrosion behavior and biocompatibility of copper with and without treatments. Results showed that copper samples treated with PT and 6-MP solutions for 3 and 1 h, respectively, are more biocompatible than those without treatment. Besides, the treatment reduces the burst release effect of copper in simulated uterine solutions during the first week after the insertion. It was concluded that PT and 6-MP treatments are promising strategies able to reduce the side effects related to the "burst release" of copper-based IUD without altering the contraceptive action.