Detection of pioglitazone based on dual-emission ratiometric fluorescence probe consisting of ZIF8 and to L-ASC-AuNP/DA nanoparticles.

A simple and sensitive dual-emission ratiometric fluorescent probe was developed using zeolitic imidazolate framework 8 (ZIF8) and L-ascorbic acid Au-doped dopamine nanoparticles (ZIF8/L-ASC-AuNP/DA NP) for the determination of pioglitazone (Pio), an oral hypoglycemic agent and insulin sensitizer, in real samples. The prepared system was based on the Pio-enhanced dual-emission intensity of ZIF8/L-ASC-AuNP/DA NP. The potential impact of various parameters on the system's emission intensity was tested. According to the findings, there is a strong linear correlation between the system's turn-on fluorescence intensity and Pio concentrations in the range 0.3 nM to 30.0 µM. The obtained value for the limit of detection (LOD) was 0.14 nM. In addition, the intra- and inter-day accuracy of the nanoprobe was studied and the findings revealed satisfactory precision and accuracy of the system. The short-term and freeze-thaw stability of Pio in plasma samples was evaluated and the results indicated the high stability of the developed nanoprobe under the test conditions. Pio was accurately detected in human plasma samples under ideal conditions with analytical recoveries in the range 86.0 - 109.3%. The results showed that the devised probe may be employed as an easy, sensitive, and precise approach for detecting Pio in real samples.

A dual-emission ratiometric fluorescent biosensor for ultrasensitive detection of glibenclamide using S-CDs/CdS quantum dots.

In the present work, sulfide-doped carbon dots (S-CDs)/cadmium sulfide quantum dots (CdS QDs) ratiometric fluorescent nanosensor has been developed for sensitive and selective determination of glibenclamide (GLC) in biological fluids. The method was based on the quenching effect of GLC on the dual-emission intensity of the S-CDs/CdS QDs system at 420 nm and 650 nm, which are related to S-CDs and CdS QDs, respectively. The fluorimetric data analysis indicated that the fluorescence signals of the system were quenched by adding GLC in a concentration-dependent manner. A good linear relationship was observed between GLC concentration and the quenched fluorescence intensity of the S-CDs/CdS QDs in the range of 0.3 nM-10.0 µM. The limit of detection (LOD) value was estimated to be 0.12 nM. Furthermore, under optimum conditions, GLC was detected in spiked human serum sample (as real media) using the developed ratiometric nanosensor with an accuracy of 99.6%. According to the results, the developed dual-emission system can be used as a reliable method for the quantitative detection of GLC in biological samples.

Simple fluorescence chemosensor for the detection of calcium ions in water samples and its application in bio-imaging of cancer cells.

This article describes the design, synthesis and characterization of a sensor suitable for practical measurement of ionized calcium in water samples and cancer cells. Calcium is an important ion in living organs and works as a messenger in several cellular functions. A lack of Ca ions interrupts the immune system and can lead to several diseases. A novel magnetic-polydopamine nanoparticle (PDNP)/rhodamine B (RhB)/folic acid (FA) nanoparticle was developed for the determination of calcium ions in MCF 7 cell lysates and water samples. Furthermore, the produced nanoparticle was employed for bioimaging of folate receptor (FR)-overexpressed cancer cells. This nanoprobe displayed a bright photoluminescence emission at 576 nm under an excitation wavelength of 420 nm. In the presence of calcium ions, the fluorescence emission of the MNPs-PDNPs/RhB/FA probe was proportionally decreased from 20 ng mL-1 to 100 ng mL-1 and 0.5 µg mL-1 to 20 µg mL-1 with a lower limit of quantification (LLOQ) of about 20 ng mL-1. The developed sensor showed a low-interference manner in the presence of possible coexistence interfering ions. In addition, this nanomaterial showed excellent biocompatibility with favorable differentiation ability to attach to the FR-positive cancer cells. The MNPs-PDNPs/RhB/FA nanoparticle has been utilized for bioimaging of the MCF 7 cell with favorable differentiation ability.

A ratiometric fluorescent sensor for detection of metformin based on terbium-1,10-phenanthroline-nitrogen-doped-graphene quantum dots.

Metformin (MTF), an effective biguanide and oral antihyperglycemic agent, is utilized to control blood glucose levels in patients with type II diabetes mellitus, and the determination of its concentration in biological fluids is one of the main issues in pharmacology and medicine. In this work, highly luminescent nitrogen-doped graphene quantum dots (N-GQDs) were modified using terbium (Tb3+)-1,10-phenanthroline (Phen) nanoparticles (NPs) to develop a dual-emission ratiometric fluorescent sensor for the determination of MTF in biological samples. The synthesized N-GQDs/Tb-Phen NPs were characterized using different techniques to confirm their physicochemical properties. The N-GQDs/Tb-Phen NPs showed two characteristic emission peaks at 450 nm and 630 nm by exciting at 340 nm that belong to N-GQDs and Tb-Phen NPs, respectively. The results indicated that the emission intensity of both N-GQDs and Tb-Phen NPs enhanced upon interaction with MTF in a concentration-dependent manner. Also, a good linear correlation between the enhanced fluorescence intensity of the system and MTF concentration was observed in the range of 1.0 nM-7.0 µM and the limit of detection (LOD) value obtained was 0.76 nM. In addition, the prepared probe was successfully used for the estimation of MTF concentration in spiked human serum samples. In conclusion, the reported dual-emission ratiometric fluorescent sensor can be used as a sensitive and simple fluorimetric method for the detection of MTF in real samples.

Ultrasensitive detection of glibenclamide based on its enhancing effect on the fluorescence emission of CdTe quantum dots.

Glibenclamide (GB), as a sulfonylurea-based medication is commonly prescribed for the treatment of type 2 diabetes. Due to its increasing consumption, there is a need to develop a simple, fast, and reliable detection method to follow its concentration in pharmaceutical and biological samples. Herein, a novel fluorometric method is developed for the sensitive measurement of GB. The method is based on the enhancing effect of GB on the fluorescence emission of mercaptopropionic acid (MPA) capped cadmium telluride quantum dots (CdTe QDs). QDs were synthesized in aqueous solution and were characterized by fluorescence spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Fluorescence intensity of QDs was enhanced by adding GB in a very low concentration. The effect of operative factors such as pH, buffer, contact time and concentration of CdTe QDs were investigated and in the optimized condition, a linear increase was achieved for the emission intensity of QDs by increasing GB concentration in the range 49-345 ng mL-1 , with a detection limit of 17.84 ng mL-1 . The offered method has an acceptable precision (relative standard deviations were < 2.8%) and was satisfactorily applied for the determination of GB in pharmaceutical products and human urine samples.