Modulation of inner filter effect of non-conjugated silver nanoparticles on blue emitting ZnS quantum dots for the quantitation of betahistine

Highly Efficient Fluorescent Detection of Vitamin B12 Based on the Inner Filter Effect of Dithiol-Functionalized Silver Nanoparticles

We report a fluorescent assay for the determination of vitamin B12 (VB12) based on the inner filter effect (IFE) of 1,3-propanedithiol-functionalized silver nanoparticles (PDT-AgNPs). PDT was simply functionalized on the surface of AgNPs through Ag-thiol interaction, which leads to significantly enhanced fluorescence, with excitation and emission at 360 and 410 nm, respectively, via their thiol-mediated aggregation. Since target VB12 has strong absorption centered at 360 nm, which is almost completely overlapping with the excitation spectra of PDT-AgNPs, the VB12 induced strong quenching of the fluorescence of PDT-AgNPs via IFE. The IFE-based mechanism for the fluorescence quenching of PDT-AgNPs in the presence of VB12 was confirmed by the analyses of Stern-Volmer plots at different temperatures and fluorescence decay curves. The fluorescence-quenching efficiency of PDT-AgNPs was linearly proportional to the concentration of VB12 in a wide range of 1 to 50 μM, with a lower detection limit of 0.5 μM, while preserving excellent selectivity toward target VB12 among possible interfering molecules. Furthermore, the PDT-AgNPs-mediated assay succeeded in quantitatively detecting VB12 in drug tablets, indicating that PDT-AgNPs can serve as an IFE-based fluorescent probe in pharmaceutical preparations by taking advantages of its ease of use, rapidity, and affordability.

Microscale thermophoresis as a powerful growing analytical technique for the investigation of biomolecular interaction and the determination of binding parameters

The in vitro panel of technologies to address biomolecular interactions are in play, however microscale thermophoresis is continuously increasing in use to represent a key player in this arena. This review highlights the usefulness of microscale thermophoresis in the determination of molecular and biomolecular affinity interactions. This work reviews the literature from January 2016 to January 2022 about microscale thermophoresis. It gives a summarized overview about both the state-of the art and the development in the field of microscale thermophoresis. The principle of microscale thermophoresis is also described supported with self-created illustrations. Moreover, some recent advances are mentioned that showing application of the technique in investigating biomolecular interactions in different fields. Finally, advantages as well as drawbacks of the technique in comparison with other competing techniques are summarized.

Silicon nanoparticles / gold nanoparticles composite as a fluorescence probe for sensitive and selective detection of Co2+ and vitamin B12 based on the selective aggregation and inner filter effect

Cobalt as a transition metal ion is a biologically essential trace element, and plays an important role in various biological systems. The silicon nanoparticles (SiNPs) / gold nanoparticles (AuNPs) composite as a simple and efficient fluorescent probe was developed to detect Co²⁺ and vitamin B₁₂ (VB₁₂) based on the selective aggregation and inner filter effect (IFE). The green-emitting SiNPs were synthesized by one-pot hydrothermal method, and the AuNPs were synthesized and modified with thioglycolic acid and cetyltrimethylammonium bromide. The fluorescent probe was fabricated by simple mixing the SiNPs and AuNPs together. In the presence of Co²⁺/VB₁₂, AuNPs are selectively aggregated, which results in the enhancement of the local surface plasmon resonance absorption centered at 520 nm and the green fluorescence of SiNPs is significantly quenched via IFE. The fluorescence quenching efficiency of the probe is linearly proportional to the concentration of Co²⁺ in the range of 0.1-80 µM with a low detection limit of 60 nM, which is far lower than the guideline value of Co²⁺ in drinking water (1.7 µM). For vitamin B₁₂ (VB₁₂), its linear relationship is in the range of 0.1-100 µM, and the limit of detection is 69 nM. Furthermore, the proposed method shows good selectivity for the detection of Co²⁺ and VB₁₂, and does not need sophisticated pretreatment, only through simple filter. It has been applied in actual environmental water samples and drug tablets with satisfactory results.

Eco-Friendly and Sensitive HPLC and TLC Methods Validated for the Determination of Betahistine in the Presence of Its Process-Related Impurity

Reducing the amounts consumed of organic solvents while keeping good chromatographic performance has been a significant step towards the greening of analytical methodologies. When sodium dodecyl sulfate (SDS) and Brij-35 surfactants are combined in a mobile phase, they can be used as a green alternative to organic modifiers. Surfactants have numerous advantages, including low cost and toxicity, safe environmental disposal, and unique selectivity, in addition to high solubilization capabilities. In this research, two highly selective chromatographic methods were adopted for the determination of betahistine (BHS) in the presence of its pharmacopeial impurity 2-(2-hydroxyethyl)pyridine (HEP). A solvent-free HPLC method was validated, in which the mixture was separated using a C18 column (3.5 µm, 75.0 × 4.6 mm) and a mobile phase composed of 0.01 M Brij-35, 0.12 M SDS, and 0.02 M disodium hydrogen phosphate adjusted to a pH of 5.5 using phosphoric acid. The flow rate was 1.5 mL min−1 and the resolved peaks were detected at 260 nm. Another HPTLC-densitometric method was validated using HPTLC aluminum plates coated with silica gel 60 F254 as the stationary phase and a developing system consisting of methylene chloride/methanol/ethyl acetate/ammonia (at a ratio of 5:2:2:0.2 by volume); the separated bands were scanned at 260 nm.

Development of an ultrasensitive spectrophotometric method for carmine determination based on fluorescent carbon dots

A high-efficiency spectrophotometric method based on nitrogen-doped fluorescent carbon dots (N-FCDs) was developed for the ultrasensitive determination of carmine (CRM) in foodstuffs. The N-FCDs were fabricated via a one-pot hydrothermal method with m-phenylenediamine as the starting material. The detection principle was based on the fluorescence quenching effect of N-FCDs by CRM, where their interaction was due to the inner filter effect (IFE) and static quenching. A good linear relationship was established for CRM detection in a concentration range of 0.1-10.0 μM with a detection limit as low as 11.2 nM. The proposed method achieved satisfactory results for CRM determination in commercial food products with recoveries better than 98.6% and relative standard deviations (RSDs) less than 4.07%. The method established in this study was simple, ultrasensitive and reliable for rapid detecting CRM in a food matrix, which could be potentially used as a useful sensing agent for the analysis of additive food colourants.