An immediate luminescence enhancement method for determination of vitamin B1 using long-wavelength emitting water-soluble CdTe nanorods

Colorimetric and naked-eye detection of arsenic(iii) using a paper-based microfluidic device decorated with silver nanoparticles

Arsenic (As) as a metal ion has long-term toxicity and its presence in water poses a serious threat to the environment and human health. So, rapid and accurate recognition of traces of As is of particular importance in environmental and natural resources. In this study, a fast and sensitive colorimetric method was developed using silver nano prisms (Ag NPrs), cysteine-capped Ag NPrs, and methionine-capped Ag NPrs for accurate detection of arsenic-based on transforming the morphology of silver nanoparticles (AgNPs). The generated Ag atoms from the redox reaction of silver nitrate and As(iii) were deposited on the surface of Ag NPrs and their morphology changed to a circle. The morphological changes resulted in a change in the color of the nanoparticles from blue to purple, which was detectable by the naked eye. The rate of change was proportional to the concentration of arsenic. The changes were also confirmed using UV-Vis absorption spectra and showed a linear relationship between the change in adsorption peak and the concentration of arsenic in the range of 0.0005 to 1 ppm with a lower limit of quantification (LLOQ) of 0.0005 ppm. The proposed probes were successfully used to determine the amount of As(iii) in human urine samples. In addition, modified microfluidic substrates were fabricated with Ag NPrs, Cys-capped Ag NPrs, and methionine-capped Ag NPrs nanoparticles that are capable of arsenic detection in the long-time and can be used in the development of on-site As(iii) detection kits. In addition, silver nanowires (AgNWs) were used as a probe to detect arsenic, but good results were not obtained in human urine specimens and paper microfluidic platforms. In this study, for the first time, AgNPs were developed for optical colorimetric detection of arsenic using paper-based microfluidics. Ag NPrs performed best in both optical and colorimetric techniques. Therefore, they can be a promising option for the development of sensitive, inexpensive, and portable tools in the environmental and biomedical diagnosis of As(iii).

A colorimetric sensor based on Glutathione-AgNPs as peroxidase mimetics for the sensitive detection of Thiamine (Vitamin B1)

A label-free sensing strategy based on the enzyme-mimicking property of Glutathione-Ag nanoparticles (GSH-AgNPs) was demonstrated for colorimetric detection of vitamin B1 (VB1). Firstly, obvious blue color accompanied with an absorption peak at 652 nm was observed due to the high peroxidase-like activity of GSH-AgNPs towards 3,3',5,5'-tetramethylbenzidine (TMB). Then, in the presence of VB1, the mimetic activity of GSH-AgNPs could be strongly restrained, evidenced as a promiment colorimetric change to colorless, which can be used to achieve the visualization detection VB1. Linear relationship between absorbance response and VB1 concentration from 0 to 0.2 µM were obtained. The detection limit was calculated as low as 40 nM. The inhibition reasons were thoroughly discussed. Considering the advantages of rapid response, easy procedure and high selectivity, the proposed method possesses potential application in environment and biological analysis for VB1 detection.

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.

Oxygen Vacancy-Engineered PEGylated MoO3-x Nanoparticles with Superior Sulfite Oxidase Mimetic Activity for Vitamin B1 Detection

Sulfite oxidase (SuO_x ) is a molybdenum-dependent enzyme that catalyzes the oxidation of sulfite to sulfate to maintain the intracellular levels of sulfite at an appropriate low level. The deficiency of SuO_x would cause severe neurological damage and infant diseases, which makes SuO_x of tremendous biomedical importance. Herein, a SuO_x mimic nanozyme of PEGylated (polyethylene glycol)-MoO_3-x nanoparticles (P-MoO_3-x NPs) with abundant oxygen vacancies created by vacancy-engineering is reported. Their level of SuO_x -like activity is 12 times higher than that of bulk-MoO₃ . It is also established that the superior increased enzyme mimetic activity is due to the introduction of the oxygen vacancies acting as catalytic hotspots, which allows better sulfite capture ability. It is found that vitamin B1 (VB1) inhibits the SuO_x mimic activity of P-MoO_3-x NPs through the irreversible cleavage by sulfite and the electrostatic interaction with P-MoO_3-x NPs. A colorimetric platform is developed for the detection of VB1 with high sensitivity (the low detection limit is 0.46 µg mL^-1 ) and good selectivity. These findings pave the way for further investigating the nanozyme which possess intrinsic SuO_x mimicing activity and is thus a promising candidate for biomedical detection.

Gold and silver nanoparticles in resonance Rayleigh scattering techniques for chemical sensing and biosensing: a review

This review (with 116 refs.) summarizes the state of the art in resonance Rayleigh scattering (RRS)-based analytical methods. Following an introduction into the fundamentals of RRS and on the preparation of metal nanoparticles, a first large section covers RRS detection methods based on the use of gold nanoparticles, with subsections on proteins (albumin, bovine serum albumin and ovalbumin, glycoproteins, folate receptors, iron binding-proteins, G-proteins-coupled receptors, transmembrane proteins, epidermal growth factor receptors), on pesticides, saccharides, vitamins, heavy metal ions (such as mercury, silver, chromium), and on cationic dyes. This is followed by a section on RRS methods based on the use of silver nanoparticles, with subsections on the detection of nucleic acids and insecticides. Several Tables are presented where an RRS method is compared to the performance of other methods. A concluding section summarizes the current status, addresses current challenges, and gives an outlook on potential future trends. Graphical Abstract Change in the resonance Rayleigh scattering (RRS) intensity when mixing the nanoparticles with the specific analyte.

Highly selective naked eye detection of vitamin B1 in the presence of other vitamins using graphene quantum dots capped gold nanoparticles

The application of Au-GQDs towards the sensitive determination of thiamine was demonstrated.

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.

Construction of a novel turn-on-off fluorescence sensor used for highly selective detection of thiamine via its quenching effect on o-phen-Zn2+ complex

In this work, a simple and selective fluorescence sensor approach called 'turn-on-off' for the determination of thiamine (TM) has been developed. As known, the o-phenanthroline (o-phen) has inner fluorescence, though when reacted with zinc ions to form the o-phen-Zn²⁺ complex the fluorescence intensity was enhanced effectively, while upon addition of TM into the o-phen-Zn²⁺ complex solution, the intensity of the system was gently quenched, which was termed the 'turn-on-off' probe. Notably, the method possessed highly selective, sensitive determination for TM with a detection limit of 0.25 μmol L^-1 and the reduced fluorescence intensity was proportional to the concentration of TM in the range 0.84-80.0 μmol L^-1 . Besides, the proposed mechanism was also investigated through exploring the Fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR) spectroscopy. Furthermore, this manner was successfully applied into practical samples for TM detection with satisfactory results.

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.

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

Determination of molecules and biomolecules using nanoparticles is promising in the development of analytical techniques. Modified Eu-doped Y2O3 nanoparticles (Y2O3:Eu NPs) by captopril have been used as a probe for thiamine (vitamin B1) determination. According to the fluorescence enhancement of modified Eu-doped Y2O3 nanoparticles caused by thiamine, a simple and sensitive method were proposed for its detection. The increase in modified Y2O3:Eu NPs fluorescence signal as a function of thiamine concentration was found to be linear in the concentration range of 0-44 μM. The limit of detection (LOD) of thiamine by this method was 0.144 μM. All the measurements were performed in natural pH, at the room temperature under ambient conditions. Possible interaction mechanism was discussed.