Weirong Yao

A novel surface-enhanced Raman scattering sensor to detect prohibited colorants in food by graphene/silver nanocomposite

A novel surface-enhanced Raman scattering (SERS) sensor made up of a graphene and silver nanocomposite was developed for detecting prohibited colorants in food. This SERS platform exhibited an excellent enrichment effect between the colorant molecules and the graphene and an ability to enhance the Raman spectra of the silver nanoparticles. Detection of different concentrations of each prohibited colorant was carried out by SERS measurements on this novel substrate. In addition, from the SERS spectra of a mixture of four kinds of prohibited colorants, it was possible to easily distinguish each colorant by its characteristic peaks. A control experiment was also performed to compare the SERS spectra obtained using the graphene/silver nanocomposite substrate with spectra obtained using Ag alone as a substrate. The results showed that the SERS nanocomposite was better for detecting prohibited colorants. The proposed method has advantages in terms of providing a simple and rapid method for the sensitive analysis of prohibited additive colorants in food.

Logic gates based on G-quadruplexes: principles and sensor applications

AbstractThis review (with 139 refs.) gives a fundamental introduction into the sensors and logic gates based on G-quadruplexes (G4s). G4 characterizes vibrant binding activities and topology diversity, which contribute to the multiple signal output modes (including labeled moieties based on distance changes, label-free outputs by employing fluorescent ligands, G4/hemin DNAzyme with catalyzing activity and colorimetric readout using gold nanoparticles) and versatile design strategies (including target-induced G4 formation/disruption, liberation of blocked G4, split G4 probes, polymerase-assisted amplification and G4/hemin enrichment on sensor surface) of G4s-based methods. Following two important trends in logic gates (application of intelligent detection schemes and logic circuit constructions), specific sections review logic sensors and logic circuits based on G4s with several representative examples. We close this review with conclusions and give a perspective that employment of DNA technologies (such as aptamers, DNA junctions/origami, toehold-mediated strand displacement, enzyme-assisted amplification, metal ion-dependent DNAzymes) and various nanomaterials in G4s-based methods results in quite a large potential in terms of logic detection and construction of logic circuits. Graphical AbstractThe vibrant binding activities, different structural topologies, multiple signal output modes and a variety of designing strategies contribute to the versatile roles of G-quadruplexes in the application and development of DNA logic gates and logic circuits.

Label-free detection of the foodborne pathogens of Enterobacteriaceae by surface-enhanced Raman spectroscopy

Label-free and rapid assessment of foodborne pathogenic contamination, which can have significant implications for food safety, is critically important. In this study, seven foodborne bacteria (Salmonella typhimurium ATCC 50013, Salmonella O7HZ10, Shigella boydii CMCC51514, Shigella sonnei CMCC51529, Shigella dysenteriae CMCC51252, Citrobacter freundii ATCC43864, and Enterobacter sakazakii 154) have been examined, which are classified as Enterobacteriaceae according to biological taxonomy. They often have high rates of outbreak. A rapid and sensitive measurement method has been developed based on surface-enhanced Raman spectroscopy (SERS) coupled with gold nanoparticles as SERS substrates. The respective SERS spectra of the pathogens and their reproducibility have been compared. The principal component analysis (PCA) multivariate statistical technique has been employed to analyze the data, and a dendrogram cluster was constructed by hierarchical cluster analysis (HCA). Our results have shown that a rapid, sensitive, label-free identification of the foodborne pathogenic bacteria could be obtained by using gold nanoparticles as effective and stable SERS substrates.

Comparative studies by IR, Raman, and surface-enhanced Raman spectroscopy of azodicarbonamide, biurea and semicarbazide hydrochloride

Azodicarbonamide is widely applied in the food industry as a new flour gluten fortifier in China, Canada, the United States, and some other countries, whose metabolites of biurea and semicarbazide hydrochloride are reaction products during baking. In this study, IR, Raman and surface-enhanced Raman scattering (SERS) spectra of azodicarbonamide, biurea, and semicarbazide hydrochloride have been studied, and vibrational bands have been assigned on the basis of density functional theory (DFT) calculations. The calculated Raman spectra were in good agreement with experimental Raman spectra. The SERS method coupled with active gold substrates has also been applied for detection of the three chemicals with pure water as solvent, with the limit of detection of this method being as low as 10 μg/mL (less than 45 μg/mL). These results showed that azodicarbonamide and its metabolites could be detected by the vibrational spectra technique, which might be applied as a powerful tool for the rapid detection on these species derived from agents added to flour.

Hepatoprotective potential of Aloe vera polysaccharides against chronic alcohol-induced hepatotoxicity in mice.

BACKGROUND Aloe vera polysaccharides are reported to exhibit multiple biological effects, including anti-oxidation, anti-inflammation and immune enhancement. However, their influence on alcoholic liver disease (ALD) remains unclear. This study was designed to determine the protective effect of extracted A. vera polysaccharides (AVGP) against ALD in a chronic alcohol-feeding mouse model and investigate the possible underlying mechanisms. RESULTS Supplementation of AVGP significantly attenuated the levels of serum aminotransferases, lipids and hepatic TG and ameliorated histopathological alterations in the model of ALD. Interestingly, AVGP markedly up-regulated hepatic expression of lipolytic genes (AMPK-α2 and PPAR-α) but had no effect on lipogenic gene expression. AVGP diminished alcohol-dependent oxidative stress partly through a decrease in MDA and increase in GSH and SOD. Alcohol-induced inflammation was also mitigated by AVGP treatment via significant reduction in LPS and TNF-α, down-regulation of TLR-4 and MyD88 and up-regulation of IκB-α. CONCLUSION This study clearly showed that AVGP exerts a potent protective effect against chronic alcohol-induced liver injury. Its hepatoprotective effect appears to be associated with its antioxidant capacity and its ability to accelerate lipolysis and inhibit inflammatory response. The results indicate that AVGP could be considered as a potent food supplement in the prevention of ALD.

Theoretical calculation (DFT), Raman and surface-enhanced Raman scattering (SERS) study of ponceau 4R

Ponceau 4R is used as a coloring agent in many different products, such as food, drinks, medicines, cosmetics and tobacco. However, ponceau 4R also shows carcinogenic, teratogenic and mutagenic behavior in high doses. In this work, standard Raman, theoretical Raman and surface-enhanced Raman scattering (SERS) spectra have been used to investigate ponceau 4R. More specifically, density functional theory (DFT) calculations have been used to calculate the optimized Raman spectrum of ponceau 4R at the B3LYP/6-31G(d) level. This has provided a better understanding of the optimized geometry and vibrational frequencies of this dye. In addition, the experimental spectrum of ponceau 4R has been compared with the theoretical spectrum; good agreement was obtained. Finally, it has shown that using SERS the detection limit of the ponceau 4R solution can be as low as 5 μg/mL. This has been achieved by SERS measurements of ponceau 4R on a substrate of gold nanoparticles. The SERS peaks at 1030, 1236, 1356 and 1502 cm(-1) were chosen as index for semi-quantitative analysis, showing that the SERS technique provided a useful ultrasensitive method for the detection of ponceau 4R.

SiO2@Au nanoshells-based SERS method for detection of sunset yellow and chrysoidine.

A novel surface-enhanced Raman scattering (SERS) substrate made up of SiO2@Au nanoshells has been developed for detecting sunset yellow and chrysoidine. It exhibits an excellent enrichment SERS effect on these two colorant molecules. In this work, density functional theory (DFT) calculations have been carried out to determine the molecular structure and theoretical Raman spectra. This provided a good description of the characteristic peaks of the molecules. In addition, the appropriate thicknesses of the shell and environment pH have been derived to obtain improved SERS signals. The lowest concentration is 1 ppm and 0.5 ppm for sunset yellow and chrysoidine, respectively. Under optimal detection condition, it has proved possible to distinguish each colorant by its characteristic peaks in the SERS spectra of a mixture of the two colorants.

Rapid surface enhanced Raman scattering detection method for chloramphenicol residues

Chloramphenicol (CAP) is a widely used amide alcohol antibiotics, which has been banned from using in food producing animals in many countries. In this study, surface enhanced Raman scattering (SERS) coupled with gold colloidal nanoparticles was used for the rapid analysis of CAP. Density functional theory (DFT) calculations were conducted with Gaussian 03 at the B3LYP level using the 3-21G(d) and 6-31G(d) basis sets to analyze the assignment of vibrations. Affirmatively, the theoretical Raman spectrum of CAP was in complete agreement with the experimental spectrum. They both exhibited three strong peaks characteristic of CAP at 1104 cm(-1), 1344 cm(-1), 1596 cm(-1), which were used for rapid qualitative analysis of CAP residues in food samples. The use of SERS as a method for the measurements of CAP was explored by comparing use of different solvents, gold colloidal nanoparticles concentration and absorption time. The method of the detection limit was determined as 0.1 μg/mL using optimum conditions. The Raman peak at 1344 cm(-1) was used as the index for quantitative analysis of CAP in food samples, with a linear correlation of R(2)=0.9802. Quantitative analysis of CAP residues in foods revealed that the SERS technique with gold colloidal nanoparticles was sensitive and of a good stability and linear correlation, and suited for rapid analysis of CAP residue in a variety of food samples.

Release of bisphenols from can coatings into canned beer in China market.

BACKGROUND The aim of this research was to understand the migration of bisphenols from can coatings into foods in the Chinese market. RESULTS The migration of bisphenols was studied in commercial cans from the Chinese market filled with four types of food simulant (FS), which were heated at 121 °C for 30 min and stored at 40 °C for 30 days. Only bisphenol A (BPA) and bisphenol A diglycidyl ether (BADGE) were found in the can coatings, and SimC (10% (v/v) ethanol/water) was the most suitable FS for their release. The levels of these bisphenols in 24 kinds of canned beer from Chinese markets were also investigated. The average concentrations of BPA and BADGE were 2.85 ± 0.79 and 0.38 ± 0.19 µg · L⁻¹ respectively, which were both lower than the EU limits, and their respective daily intakes were estimated at 0.015 and 0.0020 µg · kg⁻¹ body weight · day⁻¹. Besides, increasing storage temperature and time accelerated the release of bisphenols into FSs. CONCLUSION The present results provide some guidance to reduce the migration of bisphenols during the transport and storage of canned foods.

An AuNPs-functionalized AlGaN/GaN high electron mobility transistor sensor for ultrasensitive detection of TNT

Herein, an ultrasensitive sensor based on a AlGaN/GaN high electron mobility transistor (HEMT) was developed for the detection of 2,4,6-trinitrotoluene (TNT). The sensing surface of the AlGaN/GaN HEMT grid was covalently bonded with a layer of gold nanoparticles which were functionalized with cysteamine for specific electrostatic interaction with TNT. The binding of TNT to cysteamine through donor–acceptor interactions could affect the surface charge on the gate area of the AlGaN/GaN HEMT, resulting in a gate voltage change and density changes of the 2-dimensional electron gas (2EDG) at the interface of AlGaN/GaN. By the merit of the high electron mobility of the AlGaN/GaN transistor and robust binding between cysteamine and TNT, the sensor demonstrated a fast response and excellent performance with quantitative ranges at ppt levels (from 0.1 ppt to 10 ppb) with good selectivity towards TNT. This HEMT sensor showed attractive properties for TNT detection in terms of speed, sensitivity and miniaturization.