Phytochemical studies of white mulberry fruits (Morus alba L.)

Medicinal preparations made from plant materials have been widely used for many years due to their high pharmacological efficacy and safety of use. Therefore, a study of white mulberry fruits (Morus alba L.) for the content of substances is very important for the pharmaceutical industry such as flavonoids, alkaloids, polysaccharides, minerals, vitamins, and amino acids. White mulberry has a wide distribution area around the world, including in Kazakhstan, especially in the southern regions of the country (Almaty, Zhambyl, and Turkestan regions). The composition of the fruits of this plant is significantly influenced by the area where the trees grow, and therefore, the establishment of a specific composition of biologically active substances is very important. In the course of this study, such methods as gas chromatography were used-mass spectrometry of an extract obtained using carbon dioxide under subcritical conditions, atomic absorption, gravimetric, and spectrophotometric methods. As a result, for the first time in Kazakhstan, the composition of white mulberry fruits (Morus alba L.), namely, biologically active substances, has been identified, such as alkaloids, flavonoids, vitamins, macro- and microelements, and amino acids and fatty acids; in addition, the percentage composition of the above compounds has been determined. The results of the study show a comparative analysis of the component composition of white mulberry fruits (Morus alba L.) in various areas of tree growth, including outside of Kazakhstan. The obtained data testify to the great possibilities of using this raw material in medicine, pharmacology, and the food industry.

A dual-mode nanoprobe based on silicon nanoparticles and Fe(II)-phenanthroline for the colorimetric and fluorescence determination of nitrite

A fluorometric and colorimetric dual-modal nanoprobe (denoted as Fe²⁺-Phen/SiNPs) has been developed for selective and sensitive determination of nitrite (NO₂^-). The mechanism is based on fluorescence quenching between silicon nanoparticles (SiNPs) and Fe(II)-phenanthroline complex (Fe²⁺-Phen) via inner filter effect and redox. With the addition of increasing NO₂^-, Fe²⁺ is oxidized to Fe³⁺, recovering the fluorescence of SiNPs. Meanwhile, the color of the system gradually changes from orange-red to colorless, which enables colorimetric measurement. The NO₂^- concentration shows a wide linear relationship with fluorescence intensity from 0.1 to 1.0 mM (R² = 0.9955) with a detection limit of 2.4 μM in the fluorometric method (excitation wavelength: 380 nm). By contrast, the linear range of the colorimetric method ranges from 0.01 to 0.35 mM (R² = 0.9953) with a limit of detection of 6.8 μM (proposed selective absorbance: 510 nm). The probe has been successfully applied to nitrite determination in water, salted vegetables, and hams demonstrating broad application prospects for the determination of nitrite in complicated matrices.

Dual enzymes-mimic activity of nanolayered manganese-calcium oxide for fluorometric determination of metformin

There are different analytical methods available for the determination of metformin, as an oral hypoglycemic and antidiabetic drug, in biological samples. However, most of these methods suffer from some drawbacks, including high-priced materials and equipment, damaging chemical reagents, time-consuming nature, and tedious operation procedures. So, in this work a new, sensitive and simple method was reported for the detection of metformine. In this regard, nanolayered manganese-calcium oxide (NL-MnCaO₂) were synthesized and characterized using scanning electron microscopy (SEM), fourier transform infrared (FTIR) spectroscopy, and X-ray powder diffraction (XRD) techniques. Also, we studied the enzyme-like activity of synthesized particles and reported a bifunctional nanozyme, which performs the dual roles for peroxidase and catalase-mimicking. The results demonstrated the hindering effect of metformin on the peroxidase-mimic activity of NL-MnCaO₂ and this effect was increased by raising metformin concentration. So, a sensitive fluorometric detection system was designed for the analytical assay of metformin, based on the terephthalic acid (TA)-H₂O₂ reaction with NL-MnCaO₂. An acceptable linearity was observed between the metformin concentration and fluorescence quenching of the system in the range of 0.07-0.77 mM. Limit of detection (LOD) and limit of quantification (LOQ) were 0.17 μM and 0.96 μM, respectively. The proposed system was applied for the estimation of metformin concentration in serum samples by recoveries of 86.68-106%. So, the proposed fluorometric method provides some main advantages such as wide linear range, low detection limit, rapid detections, high sensitivity, and good practicability for the determination of metformin in biological samples.

Turning the Page: Advancing Detection Platforms for Sulfate Reducing Bacteria and their Perks

Sulfate reducing bacteria (SRB) are blamed as main culprits in triggering huge corrosion damages by microbiologically influenced corrosion. They obtained their energy through enzymatic conversion of sulfates to sulfides which are highly corrosive. However, conventional SRB detection methods are complex, time-consuming and are not enough sensitive for reliable detection. The advanced biosensing technologies capable of overcoming the aforementioned drawbacks are in demand. So, nanomaterials being economical, environmental friendly and showing good electrocatalytic properties are promising candidates for electrochemical detection of SRB as compared with antibody based assays. Here, we summarize the recent advances in the detection of SRB using different techniques such as PCR, UV visible method, fluorometric method, immunosensors, electrochemical sensors and photoelectrochemical sensors. We also discuss the SRB detection based on determination of sulfide, typical metabolic product of SRB.

A peptide nucleic acid-regulated fluorescence resonance energy transfer DNA assay based on the use of carbon dots and gold nanoparticles

A convenient fluorometric method was developed for specific determination of DNA based on peptide nuclei acid (PNA)-regulated fluorescence resonance energy transfer (FRET) between carbon dots (CDs) and gold nanoparticles (AuNPs). In this system, CDs that display lake blue fluorescence with excitation/emission maxima at 345/445 nm were used as fluorometric reporter, while AuNPs were used as fluorescence nanoquencher. A neutral PNA probe, which is designed to recognize the target DNA, was used as a coagulant to control the dispersion and aggregation of AuNPs. Without DNA, PNA can induce immediate AuNP aggregation, thus leading to the recovery of the FRET-quenched fluorescence emission of CDs. However, the addition of the complementary target DNA can protect AuNPs from being aggregated due to the formation of DNA/PNA complexes, which subsequently produces a high fluorescence quenching efficiency of CDs by dispersed AuNPs. Under optimized conditions, quantitative evaluation of DNA was achieved in a linear range of 5-100 nM with a detection limit of 0.21 nM. This method exhibited an excellent specificity towards fully matched DNA. In addition, the application of this assay for sensitive determination of DNA in cell lysate demonstrates its potential for bioanalysis and biodetection. Graphical abstract A simple fluorometric biosensor for specific detection of DNA was developed based on peptide nuclei acid (PNA)-regulated fluorescence resonance energy transfer (FRET) between carbon dots (CDs) and gold nanoparticles (AuNPs).

A dual-modal fluorometric and colorimetric nanoprobe based on graphitic carbon nitrite quantum dots and Fe (II)-bathophenanthroline complex for detection of nitrite in sausage and water

A fluorometric and colorimetric dual-mode sensing platform based on graphitic carbon nitrite quantum dots (g-CNQDs) and Fe (II)-bathophenanthroline complex (BPS-Fe²⁺) was designed to the sensitive detection of nitrite (NO₂^-) in sausage and water. In this system, the fluorescence of g-CNQDs was quenched by BPS-Fe²⁺ complex due to the inner filter effect (IFE). When NO₂^- was present, Fe²⁺ was oxidized by nitrite to form BPS-Fe³⁺ complex with BPS, leading to the recovery of the fluorescence from g-CNQDs. Therefore, we constructed a "turn-off-on" fluorescence probe for detection of NO₂^-. Moreover, with the increase of NO₂^- concentration, the color of the solution changed from red to colorless, so the UV-vis measurements and on-site visual detection were realized. The method is capable of detecting NO₂^- in the concentration range of 2.32-34.8 μM with good selectivity and high sensitivity. In addition, the method has the potential to determine NO₂^- in water samples and sausage samples.

Selenium and nitrogen co-doped carbon quantum dots as a fluorescent probe for perfluorooctanoic acid

Highly fluorescent carbon quantum dots co-doped with selenium and nitrogen  (SeN-CQDs) were fabricated via a one-pot hydrothermal route using selenomethionine as the sole precursor. The SeN-CQDs aggregates have sizes between 30 and 45 nm and display blue fluorescence with a quantum yield of 8% at excitation/emission wavelengths of 350/445 nm. The fluorescence is pH dependent and decreases under acidic conditions. The doping of the CQDs with selenium and nitrogen was proven by X-ray photoelectron spectroscopy (XPS). Fluorescence is selectively quenched by perfluorooctanoic acid (PFOA), and this is accompanied by a decreased fluorescence lifetime. Quenching is not due to aggregation in view of the unaltered sizes of nanoparticles as revealed by TEM and DLS analyses. UV-vis absorption titration suggested the formation of an excited state complex between SeN-CQDs and PFOA, and quenching originates from the internal electron transfer in the excited state complex. The method was used to detect PFOA quantitatively in the linear range of 10-70 μM with a 1.8 μM detection limit. The nanoprobe has a high selectivity for PFOA over potentially interfering molecules. The practicability of the method was ascertained by accurate detection of PFOA in real samples by the standard addition method. The method may be further improved by tuning the interaction between PFOA and SeN-CQDs through optimizing the doping and the surface composition of the SeN-CQDs. Graphical abstract Schematic presentation of a fluorometric method for perfluorooctanoic acid detection by using a selenium and nitrogen co-doped carbon quantum dots as the fluorescent probe.

Protein carbonyl determination by a rhodamine B hydrazide-based fluorometric assay

A new fluorometric assay is presented for the ultrasensitive quantification of total protein carbonyls, and is based on their specific reaction with rhodamine B hydrazide (RBH), and the production of a protein carbonyl-RBH hydrazone the fluorescence of which (at ex/em 560/585 nm) is greatly enhanced by guanidine-HCl. Compared to the fluorescein-5-thiosemicarbazide (FTC)-based fluorometric assay, the RBH assay uses a 24-fold shorter reaction incubation time (1 h) and at least 1000-fold lower protein quantity (2.5 µg), and produces very reliable data that were verified by extensive standardization experiments. The protein carbonyl group detection sensitivity limit of the RBH assay, based on its standard curve, can be as low as 0.4 pmol, and even lower. Counting the very low protein limit of the RBH assay, its cumulative and functional sensitivity is 8500- and 800-fold higher than the corresponding ones for the FTC assay. Neither heme proteins hemoglobin and cytochrome c nor DNA interfere with the RBH assay.

The Activity of Class I-IV Alcohol Dehydrogenase Isoenzymes and Aldehyde Dehydrogenase in Bladder Cancer Cells

OBJECTIVES

The aim of this study was to determine the differences in the activity of Alcohol Dehydrogenase (ADH) isoenzymes and Aldehyde Dehydrogenase (ALDH) in normal and cancerous bladder cells.

METHODS

Class III, IV of ADH and total ADH activity were measured by the photometric method and class I, II ADH and ALDH activity by the fluorometric method.

RESULTS

Significantly higher total activity of ADH was found in both, low-grade and high-grade bladder cancer, in comparison to healthy tissues.

CONCLUSION

The increased activity of total ADH in bladder cancer cells may be the cause of metabolic disorders in cancer cells, which may intensify carcinogenesis.