Ultrafast Ratiometric Detection of Aflatoxin B1 Based on Fluorescent ß-CD@Cu Nanoparticles and Pt2+ Ions.

Rapid detection of aflatoxin B1 (AFB1) is a very important task in food safety monitoring. However, it is still challenging to achieve highly sensitive detection without antibody or aptamer biomolecules. In this work, a rapid detection of aflatoxin B1 was achieved using a ratiometric fluorescence probe without antibody or aptamer for the first time. In the ratiometric fluorescence system, the fluorescence emission of AFB1 at 433 nm was significantly enhanced due to the ß-cyclodextrin-AFB1 host-guest interaction and the complexation of AFB1 and Pt2+. Meanwhile, the inclusion of aflatoxin B1 also quenched the fluorescence emission of ß-CD@Cu nanoparticles (NPs) at 650 nm based on inner filter effect mechanism. On the basis of the above effects, the ratiometric detection of aflatoxin B1 was achieved in the range of 0.03-10 ng/mL with a low detection limit of 0.012 ng/mL (3σ/s). In addition, the ß-CD@Cu NPs based nanoprobe could achieve stable response within 1 min to AFB1. The above ratiometric detection also demonstrated excellent application potential in the rapid on-site detection of AFB1 in food due to the advantages of convenience, rapidness, and high accuracy.

Mesoporous silica-loaded gold nanocluster with enhanced fluorescence and ratiometric fluorescent detection of thiram in foods.

A core-shell QDs@mSiO2@y-AuNCs nanoprobe was prepared, and a new ratiometric fluorescent sensor for thiram detection was developed. The mechanism of thiram sensing was investigated using FTIR, surface-enhanced Raman, XPS spectra, etc. The sensing of thiram was mainly ascribed to the formation of Au-S bonds between thiram and Au atoms on y-AuNCs surface, resulting in the dissociation of 11-MUA ligand from the y-AuNCs surface and the charge transfer between thiram and y-AuNCs. In the ratiometric fluorescence detection of thiram based on QDs@mSiO2@y-AuNCs, a linear range of 0.5-60 ng/mL was obtained with a LOD of 0.19 ng/mL. Compared with the fluorescence detection based on y-AuNCs, the ratiometric fluorescence detection of thiram demonstrated 3-fold enhanced sensitivity. The improvement was ascribed to two aspects: the fluorescence emission of y-AuNCs was enhanced after they were loaded onto the QDs@mSiO2 nanoparticles; the ratiometric detection mode provided more precise sensing. The detection of thiram can be completed immediately after mixing the nanoprobe with thiram. Good recoveries of thiram in apple and pear samples were achieved. All the above results demonstrated the high potential of this method in practical applications.

DNA dendrimer-templated copper nanoparticles: self-assembly, aggregation-induced emission enhancement and sensing of lead ions.

Copper nanomaterials based on DNA scaffold (DNA-Cu NMs) are becoming a novel fluorescent material, but it is still challenging to obtain highly fluorescent DNA-Cu NMs with excellent stability. In this work, we report a kind of copper nano-assemblies (Cu NASs) with aggregation-induced emission enhancement (AIEE) property using DNA dendrimers with sticky end as template. The sticky end of the DNA dendrimers induced the formation of much bigger Cu NASs with average size ranging from 131 to 264 nm, depending on the length of the DNA dendrimer sticky end from 6 bases to 27 bases. Compared with complete complementary DNA dendrimer, nearly 6-fold fluorescence enhancement was achieved using DNA dendrimer with 27 bases sticky end. Moreover, the DNA dendrimer-Cu NASs demonstrated excellent stability in serum and could be rapidly quenched by Pb2+ ions. Based on the above property, highly sensitive and selective fluorescent detection of Pb2+ ions was possible with a linear range of 2.0-100 nM and a detection limit of 0.75 nM. Due to the sensitive and rapid response to Pb2+ as well as excellent stability in complex matrix, the proposed fluorescent Cu NASs demonstrated high potential as an excellent fluorescent probe for Pb2+ in complex matrix.

A Fluorescent Detection for Paraquat Based on ß-CDs-Enhanced Fluorescent Gold Nanoclusters.

In this report, a fluorescent sensing method for paraquat based on gold nanoclusters (AuNCs) is proposed. It was found that paraquat could quench both glutathione-capped AuNCs (GSH-AuNCs) and ß-cyclodextrin-modified GSH-AuNCs (GSH/ß-CDs-AuNCs). The modification of ß-CDs on the surface of GSH-AuNCs obviously enhanced the fluorescence intensity of GSH-AuNCs and improved the sensitivity of paraquat sensing more than 4-fold. This sensibilization was ascribed to the obvious fluorescence intensity enhancement of GSH-AuNCs by ß-CDs and the "host-guest" interaction between paraquat and ß-CDs. The fluorescence quenching was mainly due to the photoinduced energy transfer (PET) between GSH/ß-CDs-AuNCs and paraquat. With the optimized ß-CDs modification of the GSH-AuNC surfaces and under buffer conditions, the fluorescent detection for paraquat demonstrated a linear response in the range of 5.0-350 ng/mL with a detection limit of 1.2 ng/mL. The fluorescent method also showed high selectivity toward common pesticides. The interference from metal ions could be easily masked by ethylene diamine tetraacetic acid (EDTA). This method was applied to the measurement of paraquat-spiked water samples and good recoveries (93.6-103.8%) were obtained. The above results indicate that host molecule modification of fluorescent metal NC surfaces has high potential in the development of robust fluorescent sensors.

DNA-Gold Nanozyme-Modified Paper Device for Enhanced Colorimetric Detection of Mercury Ions.

In this work, a paper device consisted of a patterned paper chip, wicking pads, and a base was fabricated. On the paper chip, DNA-gold nanoparticles (DNA-AuNPs) were deposited and Hg2+ ions could be adsorbed by the DNA-AuNPs. The formed DNA-AuNP/Hg2+ nanozyme could catalyze the tetramethylbenzidine (TMB)-H2O2 chromogenic reaction. Due to the wicking pads, a larger volume of Hg2+ sample could be applied to the paper device for Hg2+ detection and therefore the color response could be enhanced. The paper device achieved a cut-off value of 50 nM by the naked eye for Hg2+ under optimized conditions. Moreover, quantitative measurements could be implemented by using a desktop scanner and extracting grayscale values. A linear range of 50-2000 nM Hg2+ was obtained with a detection limit of 10 nM. In addition, the paper device could be applied in the detection of environmental water samples with high recoveries ranging from 85.7% to 105.6%. The paper-device-based colorimetric detection was low-cost, simple, and demonstrated high potential in real-sample applications.

Green Extraction of Antioxidant Polyphenols from Green Tea (Camellia sinensis).

In this study, the feasibility of improving the extraction yield of green tea antioxidant polyphenols by the combination of ultrasound-assisted extraction (UAE) and deep eutectic solvents (DESs) was investigated. Choline chloride (ChCl)-glycerol was selected as the best DES among 12 ChCl-based DESs to extract tea antioxidant polyphenols. Subsequently, the influences of extraction parameters on total phenolic content (TPC) values were investigated, and liquid/solid ratio, ultrasonic power, and ultrasonic time were optimized based on the response surface methodology. The optimal extraction conditions were a liquid to solid ratio of 36:1 (mL/g), ultrasonic power of 461.5 W, and ultrasonic time of 21 min, with the highest TPC value of 243 ± 7 mg gallic acid equivalent (mg GAE)/g dry weight (DW), which was 13% higher than that before optimization. In addition, under the optimal extraction conditions, tea polyphenolic extract exhibited higher antioxidant activity compared with conventional extraction methods. Four major catechins in the green tea extracts, including (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG) and (-)-epigallocatechin gallate (EGCG) were identified and quantified by high-performance liquid chromatography. In addition, scanning electron microscopy (SEM) analysis revealed that UAE-DES effectively disrupted the green tea leaf cells, thereby improving tea polyphenol yield. In summary, UAE-DES is an ideal green extraction method for the extraction of tea antioxidant polyphenols.

Colorimetric determination of Pb2+ ions based on surface leaching of Au@Pt nanoparticles as peroxidase mimic.

We report the first use of metallic nanozyme as colorimetric probe for Pb2+ determination. The method is based on the surface leaching of Au@PtNP nanozyme by Pb2+-S2O32- ions, accompanied by a decreased catalytic activity of the metallic nanozyme. To construct this colorimetric determination, the Pt deposition onto the AuNPs was carefully investigated and other experimental factors including kind of substrate and buffer were optimized. With increasing Pb2+ concentration, the catalytic activity of the Au@PtNPs decreased gradually. As a result, the blue color at 650 nm from the oxidation of 3,3',5,5'-tetramethylbenzidine by H2O2 faded gradually. A determination limit of 3.0 nM Pb2+ with a linear range from 20 to 800 nM was obtained. The assay demonstrated negligible response to common metal ions even at elevated concentrations. This colorimetric method was applied to the determination of Pb2+ ions spiked in lake water samples, and good recoveries (96.8-105.2%) were obtained. The above results indicate the potential application of metallic nanozymes in developing robust colorimetric assays. Graphical abstract Schematic representation of the surface leaching of Au@PtNP nanozyme by Pb2+-S2O32- ions, accompanying the decreased catalytic activity of the metallic nanozyme.

The In Vivo Antioxidant and Hepatoprotective Actions of Selected Chinese Teas.

Tea is a popular beverage and shows very strong in vitro antioxidant activity. However, the relationship among in vitro and in vivo antioxidant activities in teas is seldom reported. In this study, in vivo antioxidant and hepatoprotective activities of 32 selected Chinese teas were evaluated on a mouse model with acute alcohol-induced liver injury. The results showed that most teas significantly reduced the levels of alanine transaminase, aspartate transaminase, alkaline phosphatase, triacylglycerol, and total bilirubin in the sera of mice at a dose of 400 mg/kg. In addition, most teas greatly decreased the malondialdehyde level and increased the levels of superoxide dismutase, glutathione peroxidase, and glutathione in the liver of mice, indicating the antioxidant and hepatoprotective activities of teas. Furthermore, the in vivo antioxidant activity of dark tea was stronger than that of green tea, opposite to the results of the in vitro study. Among these 32 teas, Black Fu Brick Tea, Pu-erh Tea, and Qing Brick Tea showed the strongest antioxidant and hepatoprotective activities. Moreover, total phenolic content as well as the contents of epicatechin, gallocatechin gallate, and chlorogenic acid were found to contribute, at least partially, to the antioxidant and hepatoprotective actions of these teas. Overall, teas are good dietary components with antioxidant and hepatoprotective actions.

Nanochemoprevention with therapeutic benefits: An updated review focused on epigallocatechin gallate delivery.

Epigallocatechin gallate (EGCG) is a natural phenolic compound found in many plants, especially in green tea, which is a popular and restorative beverage with many claimed health benefits such as antioxidant, anti-cancer, anti-microbial, anti-diabetic, and anti-obesity activities. Despite its great curative potential, the poor bioavailability of EGCG restricts its clinical applcation. However, nanoformulations of EGCG are emerging as new alternatives to traditional formulations. This review focuses on the nanochemopreventive applications of various EGCG nanoparticles such as lipid-based, polymer-based, carbohydrate-based, protein-based, and metal-based nanoparticles. EGCG hybridized with these nanocarriers is capable of achieving advanced functions such as targeted release, active targeting, and enhanced penetration, ultimately increasing the bioavailability of EGCG. In addition, this review also summarizes the challenges for the use of EGCG in therapeutic applications, and suggests future directions for progress.

Health Functions and Related Molecular Mechanisms of Tea Components: An Update Review.

Tea is widely consumed all over the world. Generally, tea is divided into six categories: White, green, yellow, oolong, black, and dark teas, based on the fermentation degree. Tea contains abundant phytochemicals, such as polyphenols, pigments, polysaccharides, alkaloids, free amino acids, and saponins. However, the bioavailability of tea phytochemicals is relatively low. Thus, some novel technologies like nanotechnology have been developed to improve the bioavailability of tea bioactive components and consequently enhance the bioactivity. So far, many studies have demonstrated that tea shows various health functions, such as antioxidant, anti-inflammatory, immuno-regulatory, anticancer, cardiovascular-protective, anti-diabetic, anti-obesity, and hepato-protective effects. Moreover, it is also considered that drinking tea is safe to humans, since reports about the severe adverse effects of tea consumption are rare. In order to provide a better understanding of tea and its health potential, this review summarizes and discusses recent literature on the bioactive components, bioavailability, health functions, and safety issues of tea, with special attention paid to the related molecular mechanisms of tea health functions.

Effects of Food Processing on In Vivo Antioxidant and Hepatoprotective Properties of Green Tea Extracts.

Food processing can affect the nutrition and safety of foods. A previous study showed that tannase and ultrasound treatment could significantly increase the antioxidant activities of green tea extracts according to in vitro evaluation methods. Since the results from in vitro and in vivo experiments may be inconsistent, the in vivo antioxidant activities of the extracts were studied using a mouse model of alcohol-induced acute liver injury in this study. Results showed that all the extracts decreased the levels of aspartate transaminase and alanine aminotransferase in serum, reduced the levels of malondialdehyde and triacylglycerol in the liver, and increased the levels of catalase and glutathione in the liver, which can alleviate hepatic oxidative injury. In addition, the differences between treated and original extracts were not significant in vivo. In some cases, the food processing can have a negative effect on in vivo antioxidant activities. That is, although tannase and ultrasound treatment can significantly increase the antioxidant activities of green tea extracts in vitro, it cannot improve the in vivo antioxidant activities, which indicates that some food processing might not always have positive effects on products for human benefits.

Effects of Tannase and Ultrasound Treatment on the Bioactive Compounds and Antioxidant Activity of Green Tea Extract.

The present study investigated the effects of tannase and ultrasound treatment on the bioactive compounds and antioxidant activity of green tea extract. The single-factor experiments and the response surface methodology were conducted to study the effects of parameters on antioxidant activity of green tea extract. The highest antioxidant activity was found under the optimal condition with the buffer solution pH value of 4.62, ultrasonic temperature of 44.12 °C, ultrasonic time of 12.17 min, tannase concentration of 1 mg/mL, and ultrasonic power of 360 W. Furthermore, phenolic profiles of the extracts were identified and quantified by high-performance liquid chromatography. Overall, it was found that tannase led to an increase in gallic acid and a decrease in epigallocatechin gallate, and ultrasounds could also enhance the efficiency of enzymatic reaction.

Effects and Mechanisms of Tea and Its Bioactive Compounds for the Prevention and Treatment of Cardiovascular Diseases: An Updated Review.

Cardiovascular diseases (CVDs) are critical global public health issues with high morbidity and mortality. Epidemiological studies have revealed that regular tea drinking is inversely associated with the risk of CVDs. Additionally, substantial in vitro and in vivo experimental studies have shown that tea and its bioactive compounds are effective in protecting against CVDs. The relevant mechanisms include reducing blood lipid, alleviating ischemia/reperfusion injury, inhibiting oxidative stress, enhancing endothelial function, attenuating inflammation, and protecting cardiomyocyte function. Moreover, some clinical trials also proved the protective role of tea against CVDs. In order to provide a better understanding of the relationship between tea and CVDs, this review summarizes the effects of tea and its bioactive compounds against CVDs and discusses potential mechanisms of action based on evidence from epidemiological, experimental, and clinical studies.

Effects and Mechanisms of Tea for the Prevention and Management of Diabetes Mellitus and Diabetic Complications: An Updated Review.

Diabetes mellitus has become a serious and growing public health concern. It has high morbidity and mortality because of its complications, such as diabetic nephropathy, diabetic cardiovascular complication, diabetic neuropathy, diabetic retinopathy, and diabetic hepatopathy. Epidemiological studies revealed that the consumption of tea was inversely associated with the risk of diabetes mellitus and its complications. Experimental studies demonstrated that tea had protective effects against diabetes mellitus and its complications via several possible mechanisms, including enhancing insulin action, ameliorating insulin resistance, activating insulin signaling pathway, protecting islet ß-cells, scavenging free radicals, and decreasing inflammation. Moreover, clinical trials also confirmed that tea intervention is effective in patients with diabetes mellitus and its complications. Therefore, in order to highlight the importance of tea in the prevention and management of diabetes mellitus and its complications, this article summarizes and discusses the effects of tea against diabetes mellitus and its complications based on the findings from epidemiological, experimental, and clinical studies, with the special attention paid to the mechanisms of action.

Colorimetric detection of thiocyanate based on inhibiting the catalytic activity of cystine-capped core-shell Au@Pt nanocatalysts.

In this work, core-shell Au@Pt nanocatalysts (Au@Pt NCs) with ultrathin Pt shell were synthesized and demonstrated high peroxidase-like activity. Thiocyanate ions (SCN-) were found to effectively inhibit the peroxidase-like activity of Au@Pt NCs, and the mechanism was discussed by the characterization of TEM, DLS, EPR and XPS, etc. The inhibition of the catalytic activity of Au@Pt NCs by SCN- was mainly due to the decreased ability of the Au@Pt NCs for capturing •OH radicals and the increased ratio of Pt2+ to Pt° on the surface of the Au@Pt NCs. A sensitive colorimetric detection of thiocyanate (SCN-) was developed, based on the activity inhibition of Au@Pt NCs by SCN-. Interestingly, cystine modification of Au@Pt NCs was found to significantly improve the selectivity of SCN- recognition. After optimization, a colorimetric assay for SCN- was established with a detection limit of 5.0nM and a broad linear calibration over the range of 20nM to 40µM. This assay has the advantages of highly sensitive, selective and low-cost. Moreover, this assay demonstrated highly potential application in the quantitative determination of SCN- in water and raw milk samples.

Using FTIR spectra and pattern recognition for discrimination of tea varieties.

In order to classify typical Chinese tea varieties, Fourier transform infrared spectroscopy (FTIR) of tea polysaccharides (TPS) was used as an accurate and economical method. Partial least squares (PLS) modeling method along with a self-organizing map (SOM) neural network method was utilized due to the diversity and heterozygosis between teas. FTIR spectra results of tea extracts after spectra preprocessing were used as input data for PLS and SOM multivariate statistical analyses respectively. The predicted correlation coefficient of optimization PLS model was 0.9994, and root mean square error of calibration and cross-validation (RMSECV) was 0.03285. The features of PLS can be visualized in principal component (PC) space, contributing to discover correlation between different classes of spectra samples. After that, a data matrix consisted of the scores on the selected 3PCs computed by principle component analysis (PCA) and the characteristic spectrum data was used as inputs for training of SOM neural network. Compared with the PLS linear technique's recognition rate of 67% only, the correct recognition rate of the PLS-SOM as a non-linear classification algorithm to differentiate types of tea reaches up to 100%. And the models become reliable and provide a reasonable clustering of tea varieties.

Effects of Bauhinia championii flavones on hypoxia-reoxygenation injury in myocardial cells / 中国药学杂志

OBJECTIVE: To observe the effect and mechanisms of Bauhinia championii flavones(BCF) on hypoxia/reoxygenation (H/R) myocardial cells of neoanatal rats. METHODS: The cardiomyocytes hypoxia/reoxygenation injury model was developed, and Bauhinia championii flavones was pretreated (final concentration as 50, 100, 200 mg·L-1 respectively). The morphological changes of cardiomyocytes were observed by invert microscope. ELISA was used to evaluate the activities of tumor necrosis factor alpha, the protein expression of Bcl-2, Bax and NF-κβ was observed by immunohisto-chemistry, and Annex v-FITC/PI staining was used to detect apoptosis rate. RESULTS: Compared with model group, Bauhinia championii flavones pretreatment eased cardiomyocytes injury, decreased the activities of TNF-α and iNO S, maintained the eNOS level, up-regulated the expression of Bcl-2, down-regulated Bax and NF-κβ, and inhibited cadiocyte apoptosis (P<0.01 or P<0.05). CONCLUSION: BCF has protective effects on hypoxia/reoxygenation injury, which are associated with adjusting iNOS and NF-κβ signal channel, up-regulating Bcl-2, down-regulating Bax and NF-κβ, and inhibiting cadiocyte apoptosis.

Which model based on fluorescence quenching is suitable to study the interaction between trans-resveratrol and BSA?

There are several models by means of quenching fluorescence of BSA to determine the binding parameters. The binding parameters obtained from different models are quite different from each other. Which model is suitable to study the interaction between trans-resveratrol and BSA? Herein, twelve models based fluorescence quenching of BSA were compared. The number of binding sites increasing with increased binding constant for similar compounds binding to BSA maybe one approach to resolve this question. For example, here eleven flavonoids were tested to illustrate that the double logarithm regression curve is suitable to study binding polyphenols to BSA.