A fluorescent probe for detecting thiamine using the luminescence intensity of nanoparticles

A New Sensitive Fluorescence Sensor and Photocatalyst for Determination and Degradation of Sodium Valproate Using g-C3N4@Fe3O4@CuWO4 Nanocomposite and FCCD Optimization

In this research, carbon nitride nanocomposite coupled with Fe3O4 and CuWO4 was thermally synthesized and characterized by different techniques, including SEM, TEM, XRD, EDX, and FTIR. Due to sodium valproate's luminescence quenching of this nanocomposite, a reliable, accurate, sensitive, selective, and fast-acting sodium valproate assay was proposed. Optimization of this fluorescent sensor was carried out by the FCCD approach. In the optimum conditions, the plot of sodium valproate concentration versus nanocomposite fluorescence emission showed a linear response (R2 = 0.9918), with a range of 0-0.55 µM, the limit of detection (S/N = 3) equal to 0.85 nM and limit of qualification equal to 2.82 nM. Photocatalytic activity of g-C3N4@Fe3O4@CuWO4 (40%) nanocomposite exhibited a good potency to sodium valproate degradation. Active species of degradation including superoxide radicals, holes, and hydroxyl radicals were investigated using ammonium oxalate, benzoquinone, and 2-propanol to identify the mechanism of photodegradation action. The activity of benzoquinone in the photocatalytic process led to a reduction in the rate of analyte degradation, which indicates the prominent role of superoxide radicals compared to other species in the degradation process. The degradation rate of the analyte using the Fenton reagent was found to be around two times more than in the Fenton reagent-free process. The possible mechanism for the fluorescence sensor and photocatalytic degradation reaction was also discussed.

Sensitive and highly selective colorimetric biosensing of vitamin-C and vitamin-B1 by flavoring agent-based silver nanoparticles

A sensitive scheme was established for the detection of vitamin C (Ascorbic acid) and vitamin B1 (Thiamin HCl) using Maltol capped AgNPs (McAgNPs) as colorimetric sensor. The designed scheme showed an instant alteration in color from yellow to orange and green for vitamin-C and vitamin B1 sequentially. The probe was sensitive in a concentration range of (0-1 µM) with limit of detection 0.064 and 0.038 µM for vitamin C and vitamin B1 sequentially. The interaction mechanism between vitamin C and vitamin B1 and McAgNPs was evaluated by visible spectroscopy, FTIR, and AFM. Vitamin C attaches on the surface of nanoparticles by C=O group, while OH, C-S-C, and NH₂ groups are involved in the binding of vitamin B1 with McAgNPs. The Vit-C/Vit-B1-McAgNPs complexes were stable over a wide range of pHs. The size of McAgNPs increased after the interaction of vitamin C/vitamin B1 from 30-40 nm to 500 and 400 nm sequentially. The scheme was successfully applied for the detection of vitamin C and vitamin B1 in urine, plasma, water, and commercial pharmaceutical tablets with good recoveries. The scheme was ascertained to be more sensitive than many other formerly described schemes.

L-cysteine modified silver nanoparticles for selective and sensitive colorimetric detection of vitamin B1 in food and water samples

The use of L-cysteine modified silver nanoparticles (Cys-capped AgNPs) as a colorimetric probe for determination of vitamin B1 (thiamine) is described in the present work. This method is based on the measurement of red shift of localized surface plasmon resonance (LSPR) band of Cys-capped AgNPs in the region of 200–800 nm. The color of Cys-capped AgNPs was changed from yellow to colorless by the addition of vitamin B1. The mechanism for detection of vitamin B1 is based on the electrostatic interaction between positively charged vitamin B1, which causes the red shift of LSPR band from 390 nm to 580 nm. The interaction between Cys-capped AgNPs and vitamin B1 was theoretically explored by density function theory (DFT) using LANL2DZ basis sets with help of Gaussian 09 (C.01) program. The morphology, size distribution and optical properties of Cys-capped AgNPs were characterized by transmission electron microscope (TEM), UV-Visible spectrophotometry, Fourier transform infrared spectroscopy (FTIR) and dynamic light scattering (DLS) techniques. The method is linear in the range of 25–500 μg mL⁻¹ with correlation coefficient (R²) 0.992 and limit of detection of 7.0 μg mL⁻¹. The advantages of using Cys-capped AgNPs as a chemical sensor in colorimetry assay are being simple, low cost and selective for detection of vitamin B1 from food (peas, grapes and tomato) and environmental (river, sewage and pond) water samples.

Rapid and visual readout of vitamin B1 based on the electrostatic interaction induced aggregation of gold nanoparticles

In this work, a simple and rapid colorimetric assay for the quantitative detection of vitamin B1 (VB1) has been fabricated based on citrate-stabilized gold nanoparticles (AuNPs). The UV-Vis spectra of AuNPs varied and the relative color changed from red to purple with the sequential addition of VB1. The characterization results of AuNPs with and without the addition of VB1 confirmed that the observed phenomena were attributed to the aggregation of AuNPs induced by VB1 through electrostatic interaction. The assay was rapid and sensitive to VB1 with a detection limit of 10.9 nM ranging from 30 nM to 650 nM in 15 min. Meanwhile, the developed assay displayed excellent selectivity to VB1 since AuNPs showed negligible response to common metal ions and biological molecules. Moreover, the feasibility for the quantitative detection of VB1 in tablets and human urine samples has also been demonstrated.

Schematic illustration for colorimetric detection of VB1 with AuNPs based on the electrostatic interaction.

Thiamine Assays-Advances, Challenges, and Caveats

Thiamine (vitamin B1) is essential to the health of all living organisms and deficiency has long been associated with diseases in animals such as fish, birds, alligators, and domesticated ruminant mammals. Thiamine is also implicated in several human diseases including Alzheimer's, diabetes, dementia, depression and, most notably, Wernicke-Korsakoff syndrome and Beriberi disease. Yet, highly sensitive and specific detection of thiamine remains an analytical challenge, as pM to nm levels of thiamine need to be detected in environmental and human samples, respectively, various phosphorylated variants need to be discriminated, and rapid on-site detection would be highly desirable. Furthermore, appropriate sample preparation is mandatory, owing to the complexity of the relevant sample matrices including fish tissues, ocean water, and body fluids. This Review has two objectives. First, it provides a thorough overview of analytical techniques published for thiamine detection over the last 15 years. Second, it describes the principles of analytical approaches that are based on biorecognition and may open up new avenues for rapid and high-throughput thiamine analysis. Most notably, periplasmic binding proteins, ribozymes, and aptamers are of particular interest, as they function as bioaffinity recognition elements that can fill an important assay technology gap, owing to the unavailability of thiamine-specific commercial antibodies. Finally, the authors provide brief evaluations of key outcomes of the major assay concepts and suggest how innovative techniques could help develop sensitive and specific thiamine analytical test systems.

A simple turn on fluorescent sensor for the selective detection of thiamine using coconut water derived luminescent carbon dots

In this study microwave-assisted hydrothermal method was used to prepare highly luminescent carbon dots (1-6 nm size) within a minute from tender coconut (Cocos nucifera) water. The synthesized carbon dots (C-dots) exhibit emission of blue and green lights while excited at 390 and 450 nm wavelengths, respectively. As an application, these C-dots were tested for a simple "turn on" fluorescent sensor for rapid detection of thiamine (vitamin B1). The detection of thiamine in human body is very important to prevent various diseases such as beriberi, neurological disorders, optic neuropathy, etc. The fluorescence emission intensity of C-dots quenches after addition of Cu(2+) ion and then again increases selectively (turn on) after the addition of thiamine. The fluorescence emission intensity enhancement of Cu(2+) ion modified C-dots in the presence of thiamine exhibits a linear relationship within the thiamine concentration range of 10-50 μM. The limit of detection was found to be 280 nM from this study. The selectivity of the detection was also tested in the presence of different organic molecules and inorganic ions (Ca(2+), Mg(2+), Na(+), K(+), Cl(-), SO4(2-), and NO3(-)) which are present in blood serum and urine and found to be almost no interference in the detection. Finally, to see the applicability in real samples a commercial vitamin capsule was tested and found less than 3% error in the detected concentration. The C-dots were also used for bioimaging of fungus and the results show they are also suitable for this application too.

Sensitive and highly selective determination of vitamin B1 in the presence of other vitamin B complexes using functionalized gold nanoparticles as fluorophore

This work describes the spectrofluorimetric determination of thiamine in the presence of vitamin B complexes using 4-amino-6-hydroxy-2-mercaptopyrimidine as fluorophore. The detection limit was found to be 6.8 fM L⁻¹ (S/N = 3).