Facile Synthesis of S-doped Carbon Quantum Dots and Their Application in the Detection of Sudan I in Saffron.

This study employed citric acid as a carbon source and thiourea as a sulphur source to conduct a straightforward one-step microwave synthesis of sulphur-doped carbon quantum dots (SCQDs). For the characterization of as-synthesized SCQDs, several methods such as fluorescence spectroscopy, X-Ray photoelectron spectroscopy (XPS), X-Ray diffraction (XRD), and zeta potential analyzer were utilized. XRD and XPS spectroscopy are used to examine the chemical composition and morphological aspects. These QDs have a limited size distribution spanning up to 5.89 nm, with a maximum distribution at 7 nm, according to zeta size analyser examinations. At an excitation wavelength of 340 nm, the highest fluorescence intensity (FL intensity) of SCQDs was attained. With a detection limit of 0.77 M, the synthesized SCQDs were employed as an efficient fluorescent probe for the detection of Sudan I in saffron samples.

Long pepper (Piper longum) derived carbon dots as fluorescent sensing probe for sensitive detection of Sudan I.

In this piece of work, microwave-assisted conversion of a natural precursor in to high-valued nano-scale material was carried out by a completely greener method. The fluorescent carbon dots prepared, designated as long pepper derived carbon dots (LPCDs), have been thoroughly characterized to explore the physical and chemical properties. The system exhibits excitation dependent emission behavior and from the optimal studies the excitation and emission wavelength of the system was found to be 330 nm and 455 nm respectively. On account of the superior fluorescent behavior of the LPCDs, it was successfully employed as a fluorescent sensing probe to detect Sudan I with good level of selectivity and sensitivity. This carcinogenic dye extensively used as food adulterant can impart several health issues. Food product safety is of high concern, therefore a simple facile and economical analytical method was proposed based on the fluorescence of LPCDs for this dye detection with satisfactory statistical parameters. A linear relationship was maintained in the range of 0 to 27.27 µM Sudan I with limit of detection of 0.92 µM. The quenching mechanism was studied and finally attributed to Förster resonance energy transfer (FRET) mechanism. In addition, the probe was effectively implemented for Sudan I detection in commercial chili powder samples with good level of recovery parameters.

A test strip constructed by molecular imprinting for ratiometric fluorescence with ultra-low limit of detection for selective monitoring of Sudan I in chili powder.

An up-conversion molecularly imprinted ratiometric fluorescent probe with a monodisperse nuclear-satellite structure and its test strip are designed which can avoid fluorescent background interference to detect Sudan I in chili powder highly selective and sensitive. The detection mechanism is based on the selective recognition of Sudan I by imprinted cavities on the surface of ratiometric fluorescent probe and the inner filter effect between Sudan I molecules and the emission of up-conversion materials (NaYF4:Yb,Tm). Under optimized experimental conditions, the response of fluorescent ratio signals (F475/F645) of this test strip show a good linear relationship in the range 0.02-50 µM Sudan I. The limits of detection and quantitation are as low as 6 nM and 20 nM, respectively. Sudan I is selectively detected in the presence of fivefold higher concentrations of interfering substances (imprinting factor up to 4.4). Detection of Sudan I in chili powder samples show ultra-low LOD (44.7 ng/g), satisfactory recoveries (94.99-105.5%) and low relative standard deviation (≤ 2.0%). This research offers a reliable strategy and promising scheme for highly selective and sensitive detection of illegal additives in complex food matrix via an up-conversion molecularly imprinted ratiometric fluorescent test strip.

Allergic contact dermatitis from dyes used in the temple of spectacles.

BACKGROUND: We observed an increasing number of patients who presented with facial or retro-auricular dermatitis after skin contact with plastic spectacles or plastic covered temples. OBJECTIVES: To identify the allergens in plastic spectacles that may cause allergic contact dermatitis. METHODS: All patients with suspected allergic contact dermatitis to eyewear were tested with Solvent Orange 60 (SO60), four additionally with Solvent Yellow 14 (SY14), and five with scrapings from their own spectacles. In one case, a chemical analysis of the spectacles was performed to uncover the causative allergen. RESULTS: Three patients were allergic to SO60, two patients to SY14, and two patients were allergic to both SO60 and SY14. CONCLUSION: Patients with suspected allergic contact dermatitis from spectacles should be tested with SO60 and SY14, and based on findings from previous reports, also with Solvent Red 179.

Melatonin reverses mitochondria dysfunction and oxidative stress-induced apoptosis of Sudan I-exposed mouse oocytes.

Sudan I is one of the industry dyes and widely used in cosmetics, wax agent, solvent and textile. Sudan I has multiple toxicity such as carcinogenicity, mutagenicity, genotoxicity and oxidative damage. However, Sudan I has been illegally used as colorant in food products, triggering worldwide attention about food safety. Nevertheless, the toxicity of Sudan I on reproduction, particularly on oocyte maturation is still unclear. In the present study, using mouse in vivo models, we report the toxicity effects of Sudan I on mouse oocyte. The results reflect that Sudan I exposure disrupts spindle organization and chromosomes alignment as well as cortical actin distribution, thus leading to the failure of polar body extrusion. Based on the transcriptome results, it is found that the exposure of Sudan I leads to the change in expression of 764 genes. Moreover, it's further reflected that the damaging effects of Sudan I are mediated by the destruction of mitochondrial functions, which induces the accumulated ROS to stimulate oxidative stress-induced apoptosis. As an endogenous hormone, melatonin within the ovarian follicle plays function on improving oocyte quality and female reproduction by efficiently suppressing oxidative stress. Moreover, melatonin supplementation also improves oocyte quality and increases fertilization rate during in vitro culture. Consistent with these, we find that in vivo supplementation of melatonin efficaciously suppresses mitochondrial dysfunction and the accompanying apoptosis, thus reverses oocyte meiotic deteriorations. Collectively, our results prove the reproduction toxicity of Sudan I for the exposure of Sudan I reduces the oocyte quality, and demonstrate the protective effects of melatonin against Sudan I-induced meiotic deteriorations.

Benzo[a]pyrene-Induced Genotoxicity in Rats Is Affected by Co-Exposure to Sudan I by Altering the Expression of Biotransformation Enzymes.

The environmental pollutant benzo[a]pyrene (BaP) is a human carcinogen that reacts with DNA after metabolic activation catalysed by cytochromes P450 (CYP) 1A1 and 1B1 together with microsomal epoxide hydrolase. The azo dye Sudan I is a potent inducer of CYP1A1/2. Here, Wistar rats were either treated with single doses of BaP (150 mg/kg bw) or Sudan I (50 mg/kg bw) alone or with both compounds in combination to explore BaP-derived DNA adduct formation in vivo. Using 32P-postlabelling, DNA adducts generated by BaP-7,8-dihydrodiol-9,10-epoxide were found in livers of rats treated with BaP alone or co-exposed to Sudan I. During co-exposure to Sudan I prior to BaP treatment, BaP-DNA adduct levels increased 2.1-fold in comparison to BaP treatment alone. Similarly, hepatic microsomes isolated from rats exposed to Sudan I prior to BaP treatment were also the most effective in generating DNA adducts in vitro with the activated metabolites BaP-7,8-dihydrodiol or BaP-9-ol as intermediates. DNA adduct formation correlated with changes in the expression and/or enzyme activities of CYP1A1, 1A2 and 1B1 in hepatic microsomes. Thus, BaP genotoxicity in rats in vivo appears to be related to the enhanced expression and/or activity of hepatic CYP1A1/2 and 1B1 caused by exposure of rats to the studied compounds. Our results indicate that the industrially employed azo dye Sudan I potentiates the genotoxicity of the human carcinogen BaP, and exposure to both substances at the same time seems to be hazardous to humans.

Luminescent Chemosensor Based on Ru(II) Bipyridine Complex for Detection of Sudan I through Inner Filter Effect.

Presence of Sudan I in food stuff can be problematic and need to be checked in order to protect our health from possible carcinogen. Therefore, it is essential to detect Sudan I by efficient, rapid and reliable method. In this work, we have designed a Ru(II) polypyridyl complex, [Ru(bpy)2(CIP)]2+ probe for the selective and sensitive detection of Sudan I. Upon addition of Sudan I to the solution of [Ru(bpy)2(CIP)]2+ in ethanol, the luminescence quenched rapidly, and linear concentration range with analyte has been obtained from 0.8 to 100 µM with the limit of detection as low as 0.26 µM (S/N = 3). The effective luminescence quenching was resulted due to the inner filter effect (IFE) between luminophore, [Ru(bpy)2(CIP)]2+ and quencher, Sudan I. Our spectroscopic study was essentially provided sufficient analytical evidences in order to prove occurrence of IFE mechanism. As there were no interferences observed in luminescence measurement from the other substances the present probe has been successfully applied for the detection of Sudan I in commercial chili powder sample, making the probe suitable for practical usage.

Response of soil enzymes, functional bacterial groups, and microbial communities exposed to sudan I-IV.

As an important type of typical synthetic azo dyes, the use of sudan I-IV dyes has been of concern worldwide because of their wide applications and illegal addition into various foodstuffs, potentially resulting in water and soil pollution and having adverse effects on human health and ecosystems. However, to date, little has been reported regarding the environmental levels of these dyes and the risks that they pose to human health and ecosystems. Understanding the responses of soil enzymes, functional groups of bacteria and microbial communities to sudan dyes is of great importance to reveal their effect on the soil environment. In this study, we performed a toxicological study on the specific and overall effects of sudan I-IV dyes on the activity of soil enzymes including catalase, urease, and alkaline phosphatase after a 2- and 7-day exposure, functional groups of soil bacteria including nitrogen-fixing, ammonia-oxidizing, and denitrifying bacteria on day 14, and the structure and diversity of soil microbial community compositions on day 30. The results showed that sudan I-IV affected the activity of the soil enzymes, the abundance of the bacterium functional groups, and the structure and diversity of microbial community compositions, and the effects varied by sudan dyes I-IV, the exposure concentration, and the exposure time.

A simple assay platform for sensitive detection of Sudan I-IV in chilli powder based on CsPbBr3 quantum dots.

Sudan dyes are phenyl-azoic derivatives widely used in industry. Classified as carcinogenic and are strictly forbidden in foodstuffs; however, some unscrupulous businessmen adopted it for coloring foodstuffs. Here, a simple and effective fluorescence (FL) assay platform has been developed for the detection of Sudan I-IV based on CsPbBr3 perovskite quantum dots (QDs). It was found that the fluorescent emission of CsPbBr3 QDs can be effectively quenched by Sudan I-IV. Under the optimized conditions, the FL quenching efficiency of CsPbBr3 QDs was quantitatively correlated to the logarithmic concentrations of Sudan I-IV over the ranges of 100-10,000, 0.1-1000, 0.1-2000 and 0.4-1000 ng mL-1 for Sudan I-IV, and the corresponding limits of detection were 3.33, 0.03, 0.03 and 0.04 ng mL-1 (at 3σ/slope), respectively. CsPbX3 QDs (X = Cl, Br, and I or mixed halide systems Cl/Br and Br/I) was utilized as sensor in FL assay, which have unique optical properties of high FL quantum yields (up to 90%), narrow half peak width (26 nm) and tunable FL emissions spectra (410-700 nm). Meanwhile, the practical use of this assay platform for Sudan I-IV detection in chilli powder samples was also demonstrated, which indicated the potential in practical applications.

Ultra-Sensitive Lab-on-a-Chip Detection of Sudan I in Food using Plasmonics-Enhanced Diatomaceous Thin Film.

Sudan I is a carcinogenic compound containing an azo group that has been illegally utilized as an adulterant in food products to impart a bright red color to foods. In this paper, we develop a facile lab-on-a-chip device for instant, ultra-sensitive detection of Sudan I from real food samples using plasmonics-enhanced diatomaceous thin film, which can simultaneously perform on-chip separation using thin layer chromatography (TLC) and highly specific sensing using surface-enhanced Raman scattering (SERS) spectroscopy. Diatomite is a kind of nature-created photonic crystal biosilica with periodic pores and was used both as the stationary phase of the TLC plate and photonic crystals to enhance the SERS sensitivity. The on-chip chromatography capability of the TLC plate was verified by isolating Sudan I in a mixture solution containing Rhodamine 6G, while SERS sensing was achieved by spraying gold colloidal nanoparticles into the sensing spot. Such plasmonics-enhanced diatomaceous film can effectively detect Sudan I with more than 10 times improvement of the Raman signal intensity than commercial silica gel TLC plates. We applied this lab-on-a-chip device for real food samples and successfully detected Sudan I in chili sauce and chili oil down to 1 ppm, or 0.5 ng/spot. This on-chip TLC-SERS biosensor based on diatomite biosilica can function as a cost-effective, ultra-sensitive, and reliable technology for screening Sudan I and many other illicit ingredients to enhance food safety.

Encoding CsPbX3 perovskite quantum dots with different colors in molecularly imprinted polymers as fluorescent probes for the quantitative detection of Sudan I in food matrices.

All-inorganic cesium lead halides (CsPbX3, X  = Cl, Br, I) perovskite quantum dots (PQDs) have attracted extensive research attention due to their unique optical properties. However, their instability and sensitivity to air and moisture hinder further use in fluorescent sensing applications. In this work, the construction and application of PQDs encoded molecularly imprinted polymers (MIPs-CsPbX3) for Sudan I detection were proposed. After being encoded the PQDs, the obtained MIPs-CsPbX3 microspheres exhibited high stability for the external environment, remarkable bright fluorescence, and specific recognition for Sudan I. The fluorescent intensity of the MIPs-CsPbX3 microspheres was obviously quenched upon loading Sudan I, and good linear responses in the range of 0.5-150 µg L-1, limit of detection of 0.3 µg L-1, and good recoveries of 95.27 % to 105.96 % in spiked samples were obtained. The developed fluorescent probe provided a selective and sensitive quantified method for Sudan I detection in food matrices.

Amplified electrochemical sensor employing Ag NPs functionalized graphene paper electrode for high sensitive analysis of Sudan I.

In this study, a high-performance flexible reduced graphene oxide (rGO) paper electrode composed of silver nanoparticles (Ag NPs) for the detection of Sudan I was fabricated. Ag NPs were doped with rGO nanoheets by self-assemble and assembled into a paper electrode with layer-by-layer structure via vacuum filtration. Thanks to the highly efficient electrocatalysis of Ag NPs towards reduction of azo bond, the as-prepared hybrid paper can be used alone as a flexible sensor for the detection of Sudan I in chili powder, with the high sensitivity (22.93 µA µmol/L) and the low detection limit (41.3 nmol/L). The sensor also expressed good selectivity, repeatability, reproducibility, stability and recovery between 96.1% and 101.8% (RSD < 6%). With the advantages of low-cost and scalable production capacity, such Ag NPs/rGO functional papers can be used as flexible disposable sensors for electrochemical detection of Sudan I.

Polyoxometalates-graphene nanocomposites modified electrode for electro-sensing detection of Sudan I in food.

Sudan I, a lipophilic azo dye -dye, is desirable and urgent to be accurate detected due to its increasing levels and high toxicity in food and environmental monitoring and analysis. Herein, a sensitive electrochemical sensor for Sudan I was established based on a new K10P2W18Fe4(H2O)2O68 functionalized carbon nanomaterials (Fe4P2W18-GNPS). The electrode modified nanocomposite, Fe4P2W18-GNPS, was successfully fabricated and characterized by FTIR, SEM and UV-vis. The effective combination of Fe4P2W18 and graphene exhibited high electrocatalytic activity towards the oxidation of Sudan I, promote charge transfer, and more sensing sites. Under optimized experimental conditions, the proposed differential pulse voltammetry (DPV) showed excellent analytical performances for Sudan I with the limit of detection (LOD) of 5 nM (S/N = 3), the sensitivity of 13.10 µA·µM-1cm-2 at the 0.005-2 µM and 0.39 µA·µM-1cm-2 at 10-200 µM. The stability and reproducibility make the electrochemical sensor suitable for detecting the Sudan I in food.

Rapid determination of illegally added Sudan I in cake by triphenylamine functionalized polyhedral oligomeric silsesquioxane fluorescence sensor.

Triphenylamine functionalized polyhedral oligomeric silsesquioxane (POSS@TPA) was prepared using the Friedel-Crafts reaction with tris(4-bromophenyl)amine (TPA) as the functional monomer and polyhedral oligomeric silsesquioxane (POSS) as the framework. The as-prepared POSS@TPA has a stable structure and accomplished pore performance, allowing for the selective adsorption of Sudan I and result in the fluorescence quenches of POSS@TPA. Thus, the POSS@TPA could be used as sensors to fluorescence detect 0.12-7.4 mg/L Sudan I, with a detection limit of 0.091 mg/L. Moreover, the POSS@TPA have good reuseability can be reused more than 5 cycles after washing. Noteworthily, the response time of POSS@TPA for determination was as short as 1 min. Furthermore, the sensor was effectively used to determine Sudan I in cakes with excellent recoveries (86.4-108.8 %) and relative standard deviations (2.5-4.9 %). The results matched those of high-performance liquid chromatography (HPLC). Our work shows great potential in terms of the rapid detection of food safety.

Sudan I monitoring as a hazardous azo dye using an electroanalytical tool amplified with NiO/SWCNTs-ionic liquid catalysts.

Sudan I is an azo dye that causes cancer and is not allowed to be used in food products. The current study focused on the design and manufacture of an electrochemical sensor modified with NiO/SWCNTs, as a nano-catalyst, and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (1H3MIbTMI), as an ionic liquid binder, to monitor Sudan I as azo additive dyes in various food samples. The modified carbon paste electrode (CPE/NiO/SWCNTs/1H3MIbTMI) offered superior electrochemical performance metrics as an analytical sensor to detect trace levels of Sudan I within the concentration range of 1.0 nM-250 µM. The limit of detection was determined as 0.3 nM by the differential pulse voltammetric (DPV) technique. The proposed CPE/NiO/SWCNTs/1H3MIbTMI can be put forward to be employed as an analytical instrument for sensing Sudan I in various culinary sauces, including chili, tomato, and strawberry sauces. The obtained recovery range was determined as 97.6%-104.35%. These findings demonstrated the effectiveness of the newly created material and its potential for usage as a novel analytical instrument.

Multifunctional Carbon Dots-Based Fluorescence Detection for Sudan I, Sudan IV and Tetracycline Hydrochloride in Foods.

Sudan dyes are strictly prohibited from being added to edible products as carcinogens and tetracycline hydrochloride (TC) remaining in animal-derived food may cause harm to the human body. Therefore, it is necessary to establish a high-sensitivity, simple and convenient method for the detection of Sudan dyes and TC in foods for safety purposes. In this work, multifunctional blue fluorescent carbon dots (B-CDs) were prepared by a one-step hydrothermal synthesis using glucose as the carbon source. The results show that the fluorescence intensity of B-CDs was significantly affected by the acidity of the solution and can be quenched by Sudan I, IV and TC through selective studies. Interestingly, the fluorescence quenching intensities of B-CDs have a good linear relationship with the concentration of Sudan I and IV at pH = 3-7. The wide range of pH is beneficial to broaden the application of B-CDs in a practical samples analysis. The method has been successfully applied to real food samples of tomato paste, palm oil and honey, and the detection limits are 26.3 nM, 54.2 nM and 31.1 nM for Sudan I, Sudan IV and TC, respectively. This method integrates Sudan dyes and TC into the same multifunctional B-CDs, which shows that the sensor has a great potential in food safety detection.

Amplified electrochemical sensor employing screen-printed electrode modified with Ni-ZIF-67 nanocomposite for high sensitive analysis of Sudan I in present bisphenol A.

This study utilized a facile one-pot protocol to synthesize Ni-cobalt zeolitic imidazolate framework (Ni-ZIF-67) nanocomposite, which was then characterized by Fourier transform infrared spectroscopy, X-ray diffraction, energy dispersive X-ray spectroscopy and scanning electron microscopy. The Ni-ZIF-67 nanocomposite was subsequently applied to modify a screen-printed electrode (SPE) as a durable sensor for detection of Sudan I concomitantly with bisphenol A (BPA), with remarkably increased electrochemical response when comparing with a bare SPE. The results showed the calibration plot to be linear in the concentration range between 0.03 µM and 535.0 µM, with a narrow limit of detection of 9.0 nM (S/N = 3). Our proposed protocol was successful in detecting target analytes in real tap water and food specimens.

Molecular Modeling Study of the Genotoxicity of the Sudan I and Sudan II Azo Dyes and Their Metabolites.

Azo dyes are defined by the presence of a characteristic N=N group. Sudan I and Sudan II are synthetic azo dyes that have been used as coloring agents. Although animal toxicity studies suggest that Sudan dyes are mutagenic, their molecular mechanism of action is unknown, thus making it challenging to establish thresholds for tolerable daily intake or to understand how these molecules could be modified to ameliorate toxicity. In addition, dye metabolites, such as azobiphenyl and 4-aminobiphenyl, have been correlated with epigenetic alterations. We shed some light on the mechanisms of Sudan dye genotoxicity through a molecular modeling study of Sudan I and Sudan II dyes and two common metabolites interacting with DNA as adducts. The results suggest that all four adducts cause significant perturbations to the DNA helical conformation and structure; thus, it can be inferred that DNA repair and replication processes would be significantly impacted.

Electrochemical behaviour of Sudan I at Fe3O4 nanoparticles modified glassy carbon electrode and its determination in food samples.

In this work, a simple and sensitive electrochemical method was developed to determine Sudan I based on magnetic Fe3O4 nanoparticles modified glassy carbon electrode using cyclic voltammetry and differential pulse voltammetry. The sensor exhibited an obviously electrocatalytic activity towards the oxidation of Sudan I, which can be confirmed by the increased oxidation peak current and the decreased oxidation peak potential when compared with the bare GCE. The determination conditions, such as pH, modifier amount, accumulation time and accumulation potential, were optimised. And some kinetic parameters were calculated. Under the optimum experimental conditions, the oxidation current of Sudan I was proportional to its concentration from 0.01 to 1µM and 1 to 20µM. The detection limit was estimated to be 0.001µM (S/N=3). The developed method was successfully applied to determine Sudan I content in food samples with satisfactory results.