Paper-based visualization of auramine O in food and drug samples with carbon dots-incorporated fluorescent microspheres as sensing element

A paper-based assay for visualization of auramine O (AO) was for the first time established by using CFMs as a ratiometric fluorescent probe (RFP). The CFMs were melamine formaldehyde microspheres (MFMs) incorporated with carbon dots (CDs), where the CDs species as sensing units and MFMs as a signal amplification carrier. The proposed RFP can quantitatively measure AO content from 0.0 to 10.0 μM and exhibited an ultralow limit of detection (LOD, 15.7 nM). In particular, obvious luminescence color change of CFMs from blue to green was perceived with naked-eyes and therefore, a solution-based and a paper-based visualization platform were respectively proposed for on-site visual detection of AO with LODs of 1.15 μM and 0.83 μM, separately. Finally, those fluorescence methods were adopted in sensitively quantitative measurement of AO within various food and drug samples, providing new prospects for analysts and technical support in food quality monitoring.

Label free detection of auramine O by G-quadruplex-based fluorescent turn-on strategy

Auramine o (AO) is a synthetic dye used in paper and textile industries. Although it has been an unauthorized food additive in many countries due to its toxic and carcinogenic possibility, its illegal uses have been detected in certain food products such as pasta, semolina and spices and also in pharmaceuticals. The presence of AO in food products should be monitored, therefore, to minimize the negative health effects on consumers. In this study, a simple, highly sensitive and selective label free detection method was investigated for AO by G-quadruplex-based fluorescent turn-on strategy. The optimum fluorescent detection assay was achieved with a specific G-quadruplex DNA sequence, c-myc, at 400 nM in Tris-HCl buffer at pH 7.4. The linearity of fluorescence intensity depending on AO concentration ranged from 0 to 0.07 µM and LOD and LOQ were 3 nM and 10 nM, respectively. The G-quadruplex-based detection assay was highly specific for AO as compared to other two synthetic food colorings and successfully applied to determine AO in pasta, bulgur and curry powder with recoveries in the range from 70.33% to 106.49%. This G-quadruplex-based label free detection assay has a significant potential to be used in the detection of AO in food products.

Graphitic carbon nitride nanosheets (g-C3N4 NS) as dual responsive template for fluorescent sensing as well as degradation of food colorants

In this work, fluorescent g-C₃N₄ NS with laminar morphology and ultrathin thickness were fabricated. The as synthesized NS were well characterized by UV-Visible and Fluorescence spectroscopy, FT-IR, XRD and HR-TEM. The bright blue fluorescent suspension of g-C₃N₄ NS was utilized for efficient detection of food colorant; tartrazine (Tz) and sunset yellow (SY). Both food colorant were able to quench fluorescence of NS efficiently were able to detect them selectively over other interfering analytes. The chemosensor showed linear range response for low concentration of Tz and SY with limit of detection for Tz and SY as 0.0325 μM (32.5 nM) and 0.221 μM (221 nM), respectively. They served as non-toxic and low cost photocatalyst. The catalytic degradation process was confirmed by mass and UV-Visible spectra analysis. The g-C₃N₄ NS served dual role of detection as well as photocatalytic degradation of food colorant.

Fast Determination of Auramine O in Food by Adsorptive Stripping Voltammetry

The electrochemical behaviour of auramine O on the hanging mercury drop electrode has been investigated by cyclic and square wave voltammetry method. Reduction peak of auramine O was irreversible and adsorptive on the hanging mercury drop electrode. The optimal conditions were chosen to be Briton-Robinson buffer pH 9.0, accumulation potential -0.5 V vs. Ag/AgCl/KCl, accumulation time 60 s, pulse amplitude 250 mV·s^-1, and frequency 50 Hz. At the optimum experimental conditions, the peak of the target analyte was sharp and asymmetric. The linearity of the peak current depending on the concentration ranged from 4.0 × 10^-8 to 6.4 × 10^-7 mol L^-1. The limit of detection and limit of quantitation were 2.46 × 10^-8 mol L^-1 and 8.21 × 10^-8 mol L^-1, respectively. The recovery and relative standard deviation were 94.9% and 2.0% (n = 5). The developed method was successfully applied to determine auramine O in chicken samples with an appropriate sample preparation.

Auramine O, an incense smoke ingredient, promotes lung cancer malignancy

Burning incense to worship deities is a popular religious ritual in large parts of Asia, and is a popular custom affecting more than 1.5 billion adherents. Due to incomplete combustion, burning incense has been well recognized to generate airborne hazards to human health. However, the correlation between burning incense and lung cancer in epidemiological studies remains controversy. Therefore, we speculated that some unknown materials in incense smoke are involved in the initiation or progression of lung cancer. Based on this hypothesis, we identified a major compound auramine O (AuO) from the water-soluble fraction of incense burned condensate using mass spectrometry. AuO is commonly used in incense manufacture as a colorant. Due to thermostable, AuO released from burned incenses becomes an unexpected air pollutant. AuO is classified as a Group 2B chemical by the International Agency of Research on Cancer (IARC), however, the damage of AuO to the respiratory system remains elusive. Our study revealed that AuO has no apparent effect on malignant transformation; but, it dramatically promotes lung cancer malignancy. AuO accumulates in the nucleus and induces the autophagy activity in lung tumor cells. AuO significantly enhances migration and invasive abilities and the in vitro and in vivo stemness features of lung tumor cells through activating the expression of aldehyde dehydrogenase family 1 member A1 (ALDH1A1), and ALDH1A1 knockdown attenuates AuO-induced autophagy activity and blocks AuO-induced lung tumor malignancy. In conclusion, we found that AuO, an ingredient of incense smoke, significantly increases the metastatic abilities and stemness characters of lung tumor cells through the activation of ALDH1A1, which is known to be associated with poor outcome and progression of lung cancer. For public health, reducing or avoiding the use of AuO in incense is recommended.