Laser-induced graphene-based digital microfluidics (gDMF): a versatile platform with sub-one-dollar cost.

Digital microfluidics (DMF), is an emerging liquid-handling technology, that shows promising potential in various biological and biomedical applications. However, the fabrication of conventional DMF chips is usually complicated, time-consuming, and costly, which seriously limits their widespread applications, especially in the field of point-of-care testing (POCT). Although the paper- or film-based DMF devices can offer an inexpensive and convenient alternative, they still suffer from the planar addressing structure, and thus, limited electrode quantity. To address the above issues, we herein describe the development of a laser-induced graphene (LIG) based digital microfluidics chip (gDMF). It can be easily made (within 10 min, under ambient conditions, without the need of costly materials or cleanroom-based techniques) by a computer-controlled laser scribing process. Moreover, both the planar addressing DMF (pgDMF) and vertical addressing DMF (vgDMF) can be readily achieved, with the latter offering the potential of a higher electrode density. Also, both of them have an impressively low cost of below $1 ($0.85 for pgDMF, $0.59 for vgDMF). Experiments also show that both pgDMF and vgDMF have a comparable performance to conventional DMF devices, with a colorimetric assay performed on vgDMF as proof-of-concept to demonstrate their applicability. Given the simple fabrication, low cost, full function, and the ease of modifying the electrode pattern for various applications, it is reasonably expect that the proposed gDMF may offer an alternative choice as a versatile platform for POCT.

Associations of residential greenness and ambient air pollution with overweight and obesity in older adults.

OBJECTIVE: This study aimed to examine the impact of greenness and fine particulate matter <2.5 µm (PM2.5 ) on overweight/obesity among older adults in China. METHODS: A total of 21,355 participants aged ≥65 years were included from the Chinese Longitudinal Healthy Longevity Survey between 2000 and 2018. Normalized difference vegetation index (NDVI) with a radius of 250 m and PM2.5 in a 1 × 1-km grid resolution were calculated around each participant's residence. Cox proportional hazards models were used to estimate the effects of NDVI and PM2.5 on overweight/obesity. Interaction and mediation analyses were conducted to explore combined effects. RESULTS: The study observed 1895 incident cases of overweight/obesity over 109,566 person-years. For every 0.1-unit increase in NDVI the hazard ratio of overweight/obesity was 0.91 (95% CI: 0.88-0.95), and for every 10-µg/m3 increase in PM2.5 the hazard ratio was 1.11 (95% CI: 1.07-1.14). The effect of NDVI on overweight/obesity was partially mediated by PM2.5 , with a relative mediation proportion of 20.10% (95% CI: 1.63%-38.57%). CONCLUSIONS: Greenness exposure appears to lower the risk of overweight/obesity in older adults in China, whereas PM2.5 , acting as a mediator, partly mediated this protective effect.

ANRIL regulating the secretion of Muc5ac induced by atmospheric PM2.5 via NF-κB pathway in Beas-2B cells.

PM2.5 can cause airway inflammation and promote the excessive secretion of mucin 5ac (Muc5ac), which can further induce many respiratory diseases. Antisense non-coding RNA in the INK4 locus (ANRIL) might regulate the inflammatory responses mediated by nuclear factor kappa-B (NF-κB) signaling pathway. Beas-2B cells were used to clarify the role of ANRIL in the secretion of Muc5ac induced by PM2.5 . The siRNA was used to silence ANRIL expression. Normal and gene silenced Beas-2B cells were respectively exposed to different doses of PM2.5 for 6, 12, and 24 h. The survival rate of Beas-2B cells was detected by methyl thiazolyl tetrazolium (MTT) assay. Tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß) and Muc5ac levels were determined by enzyme linked immunosorbent assay (ELISA). The expression levels of NF-κB family genes and ANRIL were detected by real time polymerase chain reaction (PCR). The levels of NF-κB family proteins and NF-κB family phosphorylated proteins were determined using Western blot. Immunofluorescence experiments were performed to observe the nuclear transposition of RelA. PM2.5 exposure increased the levels of Muc5ac, IL-1ß and TNF-α, and ANRIL gene expression (p < .05). With the dose and time of PM2.5 exposure increasing, the protein levels of inhibitory subunit of nuclear factor kappa-B alpha (IκB-α), RelA, and NF-κB1 decreased, the protein levels of phosphorylated RelA (p-RelA) and phosphorylated NF-κB1 (p-NF-κB1) increased, and RelA nuclear translocation increased, which indicated that the NF-κB signaling pathway was activated (p < .05). Silencing ANRIL could decrease the levels of Muc5ac, IL-1ß, TNF-α, decrease NF-κB family genes expression, inhibit the degradation of IκB-α and the activation of NF-κB pathway (p < .05). ANRIL played a regulatory role in the secretion of Muc5ac and the inflammation induced by atmospheric PM2.5 via NF-κB pathway in Beas-2B cells. ANRIL could be a target for prevention and treatment of the respiratory diseases caused by PM2.5 .

Leisure Activities, Genetic Risk, and Frailty: Evidence from the Chinese Adults Aged 80 Years or Older.

INTRODUCTION: About half of adults aged ≥80 years suffer from frailty. Exercise is considered effective in preventing frailty but may be inapplicable to adults aged ≥80 years due to physical limitations. As an alternative, we aimed to explore the association of leisure activities with frailty and identify potential interaction with established polygenic risk score (PRS) among adults aged ≥80 years. METHODS: Analyses were performed in a prospective cohort study of 7,471 community-living older adults aged ≥80 years who were recruited between 2002 and 2014 from 23 provinces in China. Leisure activity was assessed using a seven-question leisure activity index and frailty was defined as a frailty index ≥0.25 using a validated 39-item health-related scale. The PRS was constructed using 59 single-nucleotide polymorphisms associated with frailty in a subsample of 2,541 older adults. Cox proportional hazards models were used to explore the associations of leisure activities, PRS with frailty. RESULTS: The mean age of participants was 89.4 ± 6.6 years (range: 80-116). In total, 2,930 cases of frailty were identified during 42,216 person-years of follow-up. Each 1 unit increase in the leisure activity index was associated with 12% lower risk of frailty (hazard ratio: 0.88 [95% confidence interval, 0.85-0.91]). Participants with high genetic risk (PRS >2.47 × 10-4) suffered from 26% higher risk of frailty. Interaction between leisure activity and genetic risk was not observed. CONCLUSION: Evidence is presented for the independent association of leisure activities and genetic risk with frailty. Engagement in leisure activities is suggested to be associated with lower risk of frailty across all levels of genetic risk among adults aged ≥80 years.

Development and Validation of a Lifespan Prediction Model in Chinese Adults Aged 65 Years or Older.

OBJECTIVES: Previous studies investigated factors associated with mortality. Nevertheless, evidence is limited regarding the determinants of lifespan. We aimed to develop and validate a lifespan prediction model based on the most important predictors. DESIGN: A prospective cohort study. SETTING AND PARTICIPANTS: A total of 23,892 community-living adults aged 65 years or older with confirmed death records between 1998 and 2018 from 23 provinces in China. METHODS: Information including demographic characteristics, lifestyle, functional health, and prevalence of diseases was collected. The risk prediction model was generated using multivariate linear regression, incorporating the most important predictors identified by the Lasso selection method. We used 1000 bootstrap resampling for the internal validation. The model performance was assessed by adjusted R2, root mean square error (RMSE), mean absolute error (MAE), and intraclass correlation coefficient (ICC). RESULTS: Twenty-one predictors were included in the final lifespan prediction model. Older adults with longer lifespans were characterized by older age at baseline, female, minority race, living in rural areas, married, with healthier lifestyles and more leisure engagement, better functional status, and absence of diseases. The predicted lifespans were highly consistent with observed lifespans, with an adjusted R2 of 0.893. RMSE was 2.86 (95% CI 2.84-2.88) and MAE was 2.18 (95% CI 2.16-2.20) years. The ICC between observed and predicted lifespans was 0.971 (95% CI 0.971-0.971). CONCLUSIONS AND IMPLICATIONS: The lifespan prediction model was validated with good performance, the web-based prediction tool can be easily applied in practical use as it relies on all easily accessible variables.

Di-(2-ethylhexyl) phthalate (DEHP) promoted hepatic lipid accumulation by activating Notch signaling pathway.

Di-(2-ethylhexyl) phthalate (DEHP) and mono-2-ethylhexyl phthalate (MEHP) can induce hepatic lipid metabolism disorders, while the molecular mechanism still remain unknown. We aim to explore the underlying mechanism of Notch signaling pathway on hepatic lipid accumulation induced by DEHP/MEHP. A total of 40 male wistar rats were exposed to DEHP (0, 5, 50, and 500 mg/kg/d) for 8 weeks, BRL-3A hepatocytes were exposed to MEHP (0, 10, 50, 100, and 200 µM) for 24 h. About 50 µM DAPT and 100 µg/mL Aspirin were used to inhibit Notch pathway and prevent inflammation, respectively. Real-Time PCR was performed to detect the mRNA expression, western blot and immunofluorescence were used to detect the protein expression. Lipids and inflammatory factors levels were determined by commercial kits. The results showed that DEHP/MEHP promoted the expression of Notch pathway molecules and lipids accumulation in rat livers/BRL-3A cells. The up-regulated Notch receptors were correlated with the TG levels in the rat liver. MEHP increased the levels of IL-8 and IL-1ß. The lipids levels were reduced after anti-inflammation. The inhibition of Notch pathway reversed the elevation of inflammation and lipid accumulation caused by MEHP. In conclusion, this study demonstrated that DEHP/MEHP led to lipid accumulation in hepatocytes by up-regulating Notch pathway and the inflammation might play a key role in the process.

Population Attributable Fractions for Modifiable Factors of Longevity and Healthy Longevity Among the Late-Elderly Aged 75 Years or Older - China, 1998-2018.

What is already known about this topic?: Limited evidence on healthy longevity was provided in the world, and no studies investigated the fractions of healthy longevity attributed to modifiable factors. What is added by this report?: Incidences of longevity and healthy longevity in China are provided. It reveals that the total weighted population attributable fractions for lifestyles and all modifiable factors were 32.8% and 83.7% for longevity, respectively, and 30.4% and 73.4% for healthy longevity, respectively. What are the implications for public health practice?: China has a high potential for longevity and healthy longevity. Strategies may be targeted at education and residence in early life as well as healthy lifestyles, disease prevention, and functional optimization in late life.

Di(2-ethylhexyl) phthalate induced thyroid toxicity via endoplasmic reticulum stress: In vivo and in vitro study.

Di(2-ethylhexyl) phthalate (DEHP) could induce thyroid injury but the mechanism was unclear. This study combined in vivo and in vitro experiments to clarify the mechanism. In vivo, the offspring of Sprague Dawley rats were gavaged with different doses of DEHP (5, 50, and 250 mg/[kg⋅d]) from in utero to 12 weeks-old. Transcriptome sequencing was used to detect the mRNA expression profile of the offspring's thyroids. Differentially expressed genes were identified, followed by Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. In vitro, Nthy-ori 3-1 cells were exposed to DEHP's metabolite mono (2-ethylhexyl) phthalate (MEHP) to verify the pathway we found by KEGG analysis. The results indicated that DEHP could disorder the thyroid hormones. Compared with the offspring in control group, the mRNA levels of 656 genes were upregulated in the offspring exposed to 50 mg/(kg⋅d) DEHP. The upregulated genes were enriched in the pathway of "protein processing in the endoplasmic reticulum (ER)." It indicated that the ER stress might play significant role in the thyroid toxicity induced by DEHP. In vitro, the mitochondrial membrane potential (ΔΨm) level of cells was decreased while the reactive oxygen species level was increased after MEHP exposure. MEHP increased the intracellular Ca2+ level and induced ER stress. After ER stress was inhibited by the 4-phenylbutyric acid, the thyroid toxicity caused by MEHP was alleviated. Taken together, our results indicated that DEHP could induce thyroid toxicity by activating ER stress.

The Relationship Between Colorectal Polyps and Serum Lipid Levels: A Systematic Review and Meta-analysis.

Colorectal polyp has been considered as the precancerous lesion of colorectal cancer, to which serum lipid levels are closely related. At present, there is no consensus on the relationship between colorectal polyps and serum lipid levels. We performed a meta-analysis to explore the effects of lipid levels on colorectal polyps. Relevant articles published from 2000 to 2020 were searched in PubMed, Web of Science, EMBASE, and Cochrane Library databases. The mean value and SD of serum lipid indexes and body mass index in colorectal polyps groups and control groups were extracted from the included articles. Combined weighted mean differences (WMDs) and 95% confidence intervals (CIs) were calculated to assess the effect size of serum lipid levels on colorectal polyps. The publication bias of the included studies were assessed based on the Egger test. Thirty-seven articles containing 19,464 cases and 63,979 controls were included. There were no significant publication bias. The levels of high-density lipoprotein cholesterol in the cases were lower than those in the controls (WMD: -2.589 mg/dL, 95% CI: -3.273, -1.906). While the levels of triglyceride (WMD: 16.933 mg/dL, 95% CI: 13.131, 20.736), total cholesterol (WMD: 5.561 mg/dL, 95% CI: 3.477, 7.645), low-density lipoprotein cholesterol (WMD: 3.109 mg/dL, 95% CI: 0.859, 5.359) and body mass index (WMD: 0.747 mg/dL, 95% CI: 0.588, 0.906) were higher in the cases. Colorectal polyps were associated with serum lipid levels and obesity. Hyperlipidemia and obesity may be the risk factors for colorectal polyps.

Role of miR-145-5p/ CD40 in the inflammation and apoptosis of HUVECs induced by PM2.5.

Fine particulate matter (PM2.5) exposure can cause the injury of vascular endothelial cells by inflammatory response. CD40 works in inflammation of endothelial cells and it may be regulated by the miRNAs. This study aimed to clarify the role and mechanism of CD40 and miR-145-5p in PM2.5-induced injury of human umbilical vein endothelial cells (HUVECs). HUVECs were treated with different concentrations of PM2.5 exposure (0, 100, 200, 400 µg/mL) for 24 h. The si-RNA was used for CD40 gene silencing (0, 200 µg/mL PM2.5, siRNA-CD40 and siRNA-CD40 + 200 µg/mL PM2.5). Mimics was used for overexpression of miR-145-5p (0, 200 µg/mL PM2.5, mimics and mimics+200 µg/mL PM2.5). The cell viability of HUVECs was detected with Cell Counting Kit8 (CCK8) kit. The level of cell apoptosis was detected by flow cytometry. The inflammation-related factor including interleukin-1ß (IL-1ß), interleukin-18 (IL-18), tumor necrosis factor α (TNF-α) and C1q complement/tumor necrosis factor (TNF)-associated proteins9 (CTRP9) were tested with enzyme-linked immunosorbent assay (ELISA) kits. The mRNA and protein expression levels of CD40, CD40L, caspase1, NLRP3 (Nod-like receptor family pyrin domain-containing 3) and IKKB were detected with quantitative real-time PCR (qRT-PCR), Western blot and Immunofluorescence. Compared with the control group, the cell viability of HUVECs exposed to PM2.5 was significantly decreased (p < 0.05); the levels of IL-Iß and TNF-α were significantly increased, while the level of CTRP9 was significantly decreased (p < 0.05). The proportion of apoptotic cells was increased after being treated with PM2.5 (p < 0.05). Besides, the mRNA and protein levels of CD40, CD40L, IKKB, NLRP3 and caspase1 were increased comparing with the control group (p < 0.05). After CD40 silencing, the condition of inflammation and apoptosis in HUVECs exposed to PM2.5 was alleviated, and the expression levels of CD40L, IKKB, NLRP3 and caspase1 were significantly decreased (p < 0.05). Furthermore, miR-145-5p was significantly down-regulated after exposure to 200µg/mL PM2.5 (p < 0.05). After over-expression of miR-145-5p, the expression level of CD40 was decreased (p < 0.05). Taken together, PM2.5 can cause inflammation and apoptosis of HUVECs via the activation of CD40, which can be regulated by miR-145-5p. Over-expression of miR-145-5p can down-regulate CD40, further inhibiting the inflammation and apoptosis of HUVECs induced by PM2.5.

[Applications of microfluidic paper-based chips in environmental analysis and detection].

Microfluidic paper-based chips have many advantages such as ease of integration, miniaturization, and automation; high throughput; low production cost; easy portability; easy storage and transportation, environmental friendliness, and feasibility of instantaneous detection. These chips are widely used in clinical diagnosis, food quality control, and immunoassays. With the continuous development of microfluidic paper microarrays in recent years, they have also received great attention for environmental contaminant analysis and detection, and research in this field has been intensive, showing excellent prospects for application. This review summarizes the latest research progress in environmental analysis from the perspective of the application of microfluidic paper-based chips, as well as future development trends and challenges. More than 150 papers from the Science Citation Index (SCI) and Chinese core journals are cited in this paper. This review includes the advantages of microfluidic paper-based chips for environmental analysis and detection; the introduction of paper chip fabrication methods, including wax printing, photolithography, dicing, plasma, laser, and inkjet etching; and the introduction of advanced analytical methods based on paper chips, such as electrochemical analysis, fluorescence analysis, colorimetric analysis, surface-enhanced Raman analysis, and integrated sensing methods. The future development trends and prospects of environmental analysis based on microfluidic paper-based chips are also reviewed. Through a rich and comprehensive review of recent related research, it is shown that although microfluidic paper-based chip technology has only been developed for little more than a decade since its introduction, this technology has seen rapid development in environmental analysis-related research and has yielded rich results. The hydrophilic and porous nature of cellulose in paper as a chip substrate allows the passive transport of liquids without an external power source. The diversity of available microfluidic paper-based chip fabrication and analysis methods allows flexible selection and matching according to different environmental conditions and detection requirements, so that the best detection results can be obtained. Moreover, microfluidic paper chips as detection platforms show good biocompatibility in the analysis and detection of environmental pollutants, enabling the analysis of more types of pollutants. The used paper is biodegradable and can be directly disposed of as ordinary garbage after appropriate degradation treatment; thus it is environmentally friendly and does not impact the health of the operators. In addition, the low production cost and simple operation of the paper chip design study make it possible to fabricate low-cost, portable, and practical analytical equipment, which is important for rapid testing of the conventional environment. However, there are some inherent disadvantages: the mechanical strength of the paper is not sufficiently high to resist deformation; degree of fluid control is difficult to achieve the desired effect, and the sample flow may be lost due to leakage; multiple contaminants may interfere with one another when analyzed in parallel; there are difficulties in commercial mass production. However, these problems also point to the direction for the research and development of microfluidic paper-based chips in the field of environmental testing. With continuous advances in manufacturing and analysis technologies, microfluidic paper-based chips are expected to play a more prominent role in future environmental analysis.

Dual-mode detection of organophosphate pesticides in pear and Chinese cabbage based on fluorescence and AuNPs colorimetric assays.

Herein, a dual-mode method based on fluorescent and colorimetric sensor was developed for determination of organophosphate pesticides (OPs). In this study, indoxyl acetate (IDA) was hydrolyzed by esterase into indophenol. Indophenol leads to changes in fluorescence signal and aggregation of gold nanoparticles (AuNPs); ultimately changing the color from red to blue. When OPs exist, the formation of indophenol was inhibited. With increasing the concentrations of OPs, the enhancement rate of fluorescence signal decreases, and the color change of AuNPs weakened gradually. The assay was applied for determination of dichlorvos, trichlorfon, and paraoxon, and the limits of detection (LODs) were 0.0032 mg/kg, 0.0096 mg/kg, and 0.0074 mg/kg (fluorometric assay), and 0.0120 mg/kg, 0.0224 mg/kg, and 0.0106 mg/kg (colorimetric assay), respectively. Finally, such a convenient and sensitive sensing assay was successfully applied for quantification of OPs in pear and Chinese cabbage with good recoveries ranged between 80.19 and 116.93%.

Role of Notch pathway in effect of mono-2-ethylhexyl phthalate on the proliferation and cell cycle of SH-SY5Y cell.

Neuroblastoma (NB) is an estrogen-dependent tumor. Mono-2-ethylhexyl phthalate (MEHP) has an estrogen-like effect. However, the effects of MEHP on the progression of NB are not well illustrated. This study was to clarify the effect of Notch pathway on proliferation and cell cycle of SH-SY5Y cell induced by MEHP. The viability of SH-SY5Y and BE2C cells were detected by CCK8; cell cycle and apoptosis were detected by flow cytometry; the protein expression levels of Notch pathway and cell cycle related proteins were detected by Western-blot. Results show that MEHP exposure can promote cell proliferation and altered the cell cycle. MEHP exposure can up-regulate the expression of C-MYC, Cyclin D1, Bcl-2 and affected the Notch pathway. In conclusion, MEHP exposure can promote NB cell proliferation and affect the cell cycle and apoptosis. Notch pathway plays a critical role in accelerating the cell cycle and inhibiting the apoptosis of SH-SY5Y cells caused by MEHP.

Limonin induces apoptosis of HL-60 cells by inhibiting NQO1 activity.

Limonin is an important bioactive substance in citrus fruits, especially in seeds, which has great potential in cancer prevention and treatment. In order to explore the anticancer activity based on interaction between limonin and NQO1, Human promyelocytic leukemia cells (HL-60) were studied in vitro. We found that limonin could inhibit proliferation and promote apoptosis of HL-60 cells, and the effect was positively correlated with its dosage. Western blot results showed that limonin could activate the endogenous apoptosis pathway mediated by mitochondria via up-regulating pro-apoptotic proteins (Bax, cytochrome c, Caspase3, and Caspase9) and down-regulating anti-apoptotic proteins (Bcl-2), thus inhibiting the proliferation of HL-60 cells and promoting apoptosis, which further proved the anticancer activity of limonin from the molecular mechanism. At the same time, limonin down-regulated the expression of NQO1, indicating that limonin may indirectly act on the apoptosis pathway by regulating the expression activity of antioxidant enzymes in vivo, thus exerting its inhibitory effect on tumor cells, which provides an idea for the molecular mechanism that natural products can indirectly exert their anticancer effect by regulating the activity of antioxidant enzymes.

Intelligent spectral algorithm for pigments visualization, classification and identification based on Raman spectra.

Raman spectroscopy is a molecular vibrational spectroscopic technique has developed rapidly in recent years, especially in rapid field detection. In this paper, we discuss the Raman spectral pretreatment method and classification algorithm by using nearly 300 pigments spectral data as an example. Here, more than 5 kinds of classification algorithms such as SVM, KNN, ANN and et al are used to sovle the problem of pigments visualization, classification and identification via Raman spectral, and the results show that most of the algorithms fit well, with an accuracy of 90%. Moreover, SNR (Signal to noise ratio) is introduced to evaluate the stability of our algorithm. When the SNR is low, the accuracy of the algorithm decreases sharply. When the SNR was 1, the accuracy rate reached the highest value of 39.46%. In order to slove this problem, the flattopwin, hanning, blackman algorithm was introduced to denoise the signal with low SNR, even when SNR = 1, the signal is 80% accurate. It is proved that in the extreme case of this application, the algorithm still maintains good accuracy, and our research pave the way to use interlligent algorithms to solve the problems in the fields of Raman spectral detection.

An Overview on the Mechanisms and Applications of Enzyme Inhibition-Based Methods for Determination of Organophosphate and Carbamate Pesticides.

Acetylcholinesterase inactivating compounds, such as organophosphate (OP) and carbamate (CM) pesticides, are widely used in agriculture to ensure sustainable production of food and feed. As a consequence of their applications, they would result in neurotoxicity, even death. In this essence, the development of enzyme inhibition methods still shows great significance as rapid detection techniques for on-site large-scale screening of OPs and CMs. Initially, mechanisms and applications of various enzyme-inhibition-based methods and devices, including optical colorimetric assay, fluorometric assays, electrochemical biosensors, rapid test card, and microfluidic device, are highlighted in the present overview. Further, to enhance the enzyme sensitivity for detection; alternative enzyme sources or high yield enrichment methods (such as abzyme, artificial enzyme, and recombinant enzyme), as well as enzyme reactivation and identification, are also addressed in this comprehensive overview.

A balsam pear-shaped CuO SERS substrate with highly chemical enhancement for pesticide residue detection.

Simple and traditional hydrothermal fabrication of a novel balsam pear-shaped CuO with high SERS enhancement is presented. XRD (X-ray diffraction), SEM (scanning electronic microscopy), TEM (transmission electron microscope), HRTEM (high-resolution transmission electron microscope), UV-Vis, and Raman are adopted to ensure that this balsam pear-shaped CuO with dense nanoparticle protuberance is successfully prepared. The LOD of this CuO SERS substrate is 4.79 µg L-1 with R6G as molecular probe. By using DFT (density functional theory) calculation and FDTD (finite difference time domainmethod) simulation, both EM (electromagnetic enhancement) and CM (chemical enhancement) mechanisms are investigated, and the results show that these two-enhancement mechanisms can coexist in this balsam pear-shaped CuO. Finally, the prepared substrate has been applied for the determination of trace levels of paraquat in solution , and results show that its LOD for paraquat is 275 µg L-1 (optimum Raman band: 1646 cm-1 Raman shift), which is better than the government standard in China. A dexterous and facile way for fabrication of CuO SERS-active substrates with low cost and high performance, quite promising in detection of chemically hazardous substances and pesticide residue is provided. Graphical abstract.

A facile seed growth method to prepare stable Ag@ZrO2 core-shell SERS substrate with high stability in extreme environments.

A stable substrate is extraordinarily important for the trace detection of Surface Enhanced Raman Scattering technique. We have designed in this paper a simple seed growth method to prepare Ag@ZrO2 core-shell nanoparticles as well as regulate the core-shell ratio by adjusted concentration of zirconium propoxides added. The shell thickness effect and spacing on SERS activities have been simulated in different finite time domains, which goes perfectly with those previous experiment results. With Ag@ZrO2 core-shell nanoparticles adopted as the SERS substrate and R6G as molecular probe, the detection range could reach as great as 10-8 M. The regression model, obtained through principal component analysis, is adopted for some rapid and precise detection; and the determination coefficient (R2) is going up to 0.9743, proving that the SERS substrate we have prepared has extremely high detection accuracy. To explore the stability of core-shell nanoparticles, we have taken both two different cases of strong acid solution as well as strong alkali solution for the core-shell nanoparticle etching, and this is how a SERS test could be carried out. These experimental results have indicated that the outer zirconia layer could keep the silver surface from oxidation and its stability is ensured, quite crucial for the applied SERS.

Detection of systemic pesticide residues in tea products at trace level based on SERS and verified by GC-MS.

Surface-enhanced Raman spectroscopy (SERS) has the potential to detect pesticide residues in agricultural products. However, some systemic pesticides, such as chlorpyrifos, can enter the plant tissue, and not just stay on the surface. Consequently, many SERS studies halted at practical application because of its complexity. In this work, SERS technology was used to detect chlorpyrifos residues in tea products at the semiquantitative level. A simple pretreatment method effectively avoided interference of other fluorescent substances, and all major peaks could be distinguished on the basis of a novel substrate. A principal component analysis algorithm was applied to form a regression model, and a nanogram detection limit was obtained. Furthermore, chlorpyrifos residues in the same tea products were also measured by gas chromatography-mass spectrometry, and the results show a small range of errors. From the comparative study of the two detection methods, the results suggest the great promise of SERS technology for rapid inspection of agricultural products.

SERS-based vibration model and trace detection of drug molecules: Theoretical and experimental aspects.

Prescription drug abuse can lead to serious medical negligence, so there is an urgent need to address its screening problem. Gliclazide is widely used as an antihypertensive drug for lowering blood sugar, but its excessive intake can cause serious harm to human body. Here we take gliclazide as an example to provide a method to realize the screening of drug abuse. Flower-like silver nanoparticles were prepared as surface enhanced Raman scattering (SERS) substrate, which can quantitatively and accurately detect the concentration of gliclazide. To understanding the enhanced activity of flower-like silver substrates, the Finite-Difference Time-Domain (FDTD) simulation model was established, and the simulation results showed that flower-like silver had high SERS substrate activity as well as enhanced hot spots at the rough particle surface and the adjacent particles. The experimental results indicated that the flower-shaped silver had an excellent Raman enhancement effect using R6G as detection molecules. When the gliclazide solutions with different concentration gradients were tested, the molecular vibrational modes were also obtained using Gaussian calculations. The rapid and accurate detection of gliclazide concentration was processed by Principal Component Analysis, which were consistent with the experiment, suggesting the importance of the combination of experiment and calculation. Finally, SERS substrate test was performed on the daily medication gliclazide tablets (II), which proved that the flower-like silver still has great Raman enhancement effect on the detection of actual samples.