Simultaneous detection of dual microRNAs related to EV71 using ICP-MS based on metal nanoparticle labeling with hybridization chain reaction.

BACKGROUND: Hand, foot, and mouth (HMFD) disease caused by enterovirus 71 (EV 71), is closely associated with severe clinical manifestations and can be deadly. Early detection of EV 71 can be achieved by detecting the increment in miR296 and miR16 in the serum. Using HCR to amplify signals and convert biological signals into metal nanoparticle signals detectable by ICP-MS is a detection method that can collect more accurate and reliable information, compared with traditional methods, in the detection of biological samples. RESULTS: We described a strategy for the simultaneous detection of miR296 and miR16 by ICP-MS based on metal nanoparticles (NPs) labeling with HCR. Briefly, single-stranded DNA (ssDNA) and magnetic beads (MBs), as well as NPs and signal probes for miRNA (Sp-miR) were firstly conjugated via the streptavidin-biotin recognition system, constituting ssDNA-MBs and NPs-Sp-miR complex, respectively. The latter complex then hybridized with the former through HCR, generating the nanosensors for targets. Then, the targets were added and hybridized with ssDNA, and the HCR complex with NPs was released into the solution. Finally, the corresponding signals of the NPs were measured by ICP-MS. Results demonstrated that the developed method had good sensitivity and satisfactory selectivity and precision. Furthermore, when applied to biological samples with a complex matrix, the developed method also showed good recovery (88 % - 92 %) and reproducibility (RSD<10 %). SIGNIFICANCE: This method contributes to the early diagnosis of HFMD and opens up ideas for the further development of high-throughput biomarker detection. The strategy has practical potential for miR296 and miR16 detection in biological samples and provides a promising tool for multiple miRNA detection.

A new chemotherapy strategy for advanced hepatocellular carcinoma with exrahepatic metastasis: predictors of long-term survival.

The prognosis of hepatocellular carcinoma (HCC) with extrahepatic metastasis (EHM) is extremely poor. This study aimed to identify prognostic factors for systemic chemotherapy of HCC with EHM. Eighty-five patients who received systemic chemotherapy for HCC with EHM between May 2014 and October 2021 were retrospectively evaluated. Patient demographic data and characteristics of hepatic tumors and EHM were assessed to identify factors that were significantly associated with prognosis. Of the 85 patients, 68 (80.0%) had pulmonary metastasis, 11 (12.9%) had abdominal lymph node metastasis, 7 (8.2%) had abdominal metastasis, and 4 (4.7%) had bone metastasis. The median overall survival (OS) was 17.0 months, and the median progression-free survival (PFS) was 5.1 months. Univariate analysis of OS showed that synchronous EHM-HCC, serum albumin level<35 g/l and number of hepatic tumors>1 were significantly associated with poorer OS. The results of the multivariate analysis indicated that the serum albumin level and number of hepatic tumors were independent prognostic factors. Subgroup analysis of patients with 0, 1, or 2 of these independent prognostic factors showed that the median OS was 24.0 months, 16.2 months and 7.7 months and that the ORR was 38.3%, 22.6% and 0, respectively. Systemic chemotherapy is beneficial for well-selected HCC patients with EHM. The number of hepatic tumors and serum albumin level were independent risk factors for prognosis, and the number of risk factors significantly influenced OS. Therefore, these factors need to be considered before administering systemic chemotherapy for HCC patients with EHM.

Heavy metals in meat products from Shandong, China and risk assessment.

In this study 13 heavy metals were analysed in representative livestock meat, poultry meat, livestock offal and poultry offal samples (20 per category) from marketplaces and retail stores in 16 cities in Shandong province, China. The investigated heavy metals were Cu, Cr, V, Ni, As, Se, Sn, Cd, Pb, Sb, Mn, Ba and Hg. Results revealed mean levels of total heavy metals in meat and offal of 1.56 mg/kg and 39.8 mg/kg, respectively. Cu, Cr, Mn, Ni, Se, Ba and Pb were found in all samples (100%), followed by Hg (95.0%), V (91.3%), Sn (73.8%), Cd (51.3%), As (21.3%) and Sb (11.3%). Hazard Quotient (HQ) and Hazard Index (HI) values showed that high meat intake can cause potential health risks. Thus, continuous monitoring of health risks and trends of heavy metals in meat products is needed, both for food safety and consumer's health.

ICP-MS and fluorescence dual-mode detection of ZIKV-RNA based on quantum dot labeling with hybridization chain reaction.

The detection of Zika virus (ZIKV) is of great significance to human life and health. Herein, we presented an ICP-MS and fluorescent dual-mode sensor for quantitative analysis of Zika virus RNA fragments (ZIKV-RNA), which employed quantum dots (QDs) as signal tags and combined with hybridization chain reaction (HCR). The dual-mode sensor realized cross-checking of the analysis results and improved the assay accuracy. Firstly, the single-stranded DNA (ssDNA) was anchored on the surface of magnetic beads (MBs). Afterward, HCR was conducted with probe DNA-CdSe quantum dots conjugates (pDNA-QDs) and link DNA (lDNA), producing the MBs-ssDNA-[pDNA-QDs-lDNA]n conjugates. In the presence of target ZIKV-RNA, a strand displacement reaction occurred, leading to the dissociation of the [pDNA-QDs-lDNA]n labels from the conjugates into the solution. Finally, the signal intensity was detected using ICP-MS and fluorescence analysis, with achieved limits of detection of 131 pM and 152 pM, respectively. The inter-assay RSD values of fluorescence and ICP-MS were 3.94 % and 4.26 % at 10 nM level, respectively, showing that the method had good precision. This method showed high selectivity and was applied to the analysis of biological fluids. There was no significant difference between the results of ICP-MS modes and fluorescence mode. This method offers a new strategy for sensitivity analysis of ZIKV-RNA and exhibits promise in clinical applications for diagnosis.

Occurrence of 8 trace elements in Rhizoma Cibotii from China and exposure assessment.

The contamination of trace elements in Chinese edible herbs has attracted worldwide concern over the world. The objective of the present study was to investigate the occurrence and exposure assessment of eight trace elements in Rhizoma Cibotii from China. For this purpose, the method of inductively coupled plasma mass spectrometry was employed to detect the contamination levels of target trace elements in 58 Rhizoma Cibotii samples. The results demonstrated that the trace elements of Cr, Ni, Cu, Zn, and Pb were detected in all analyzed samples; the occurrence frequencies of As, Se, and Cd were 98.3%, 96.6%, and 98.3%, respectively. The highest mean levels were found in Zn (17.32 mg/kg), followed by Pb (8.50 mg/kg) and Cu (3.51 mg/kg). For a further step, one-way ANOVA was used to compare the difference of eight elements levels among groups, and Pearson's correlation analysis was used to explore the correlation between elements in Rhizoma Cibotii. A strong positive correlation between Zn and Cd was observed by Pearson's correlation analysis, which indicated that the possible presence of Cd contamination in Rhizoma Cibotii. Based on the contamination levels, the mean exposure of individual element and the health risks of eight trace elements in Rhizoma Cibotii were estimated by health risk assessment models. The calculated HQ values were less than 1, indicating that the contamination of trace elements in Rhizoma Cibotii did not pose significant health risks to human. In conclusion, the study provided baseline information on the contamination levels of trace elements in Rhizoma Cibotii. Moreover, it is necessary to monitor the trend of trace elements levels in Rhizoma Cibotii, which will be useful for ingredient control and human health protection.

Combined FOLFOX4 with all-trans retinoic acid versus FOLFOX4 with placebo in treatment of advanced hepatocellular carcinoma with extrahepatic metastasis: a randomized, double-blind comparative study.

The majority of hepatocellular carcinoma (HCC) cases are diagnosed at an advanced stage. Currently, there are only a few therapeutic methods available for patients with advanced HCC and extrahepatic metastasis (EHM). Systemic chemotherapy, such as FOLFOX4 (infusions of fluorouracil, leucovorin, and oxaliplatin), has been reported for treating advanced HCC with EHM, but its effectiveness is very poor. In this randomized, double-blind, placebo-controlled study, we aimed to assess the efficacy and safety of FOLFOX4 with all-trans-retinoic acid (ATRA) as a palliative treatment for HCC patients with EHM, compared to FOLFOX4 with a placebo. The primary endpoint was overall survival (OS), and subsequently, an exploratory model was developed based on bioinformatics to predict the efficacy of FOLFOX4-ATRA treatment. A total of 108 patients were randomly assigned in a 1:1 ratio to receive either FOLFOX4-ATRA or FOLFOX4-placebo. The intention-to-treat (ITT) population showed a median OS of 16.2 months for the FOLFOX4-ATRA group, compared with 10.7 months for the FOLFOX4-placebo group (HR 0.56, 95% CI 0.33-0.93; p = 0.025). The median progression-free survival (PFS) was 7.1 months for the FOLFOX4-ATRA group and 4.2 months for the FOLFOX4-placebo group (HR 0.62, 95% CI 0.41-0.94; p = 0.024). A panel of proteins with unique upregulation during complete response (CR) (SOD3, TTR, SSC5D, GP5, IGKV1D-33) and partial response (PR) (TGFB1, GSS, IGHV5-10-1) effectively predicted CR and PR in patients treated with FOLFOX4-ATRA, as compared to FOLFOX4-placebo. The results suggest that FOLFOX4-ATRA is a safe and effective treatment for patients with advanced HCC and EHM in eastern China.

Two-phase effects of environmentally relevant lanthanum on life-history traits of Daphnia magna and transgenerational bioenergetic profiles: Implications for nutritional and environmental consequences.

The versatile applicability of rare earth elements (REEs) especially lanthanum (La) in diverse fields, has led to large-scale mineral exploitation globally, inevitably resulting in substantial release of La into environment. As emerging anthropogenic environmental contaminant, La-induced toxicological effects and potential ecotoxicological implications in relation to realistic levels of La in aquatic ecosystems are becoming major concerns. To address these issues, Daphnia magna was selected as a prototype, and toxicity tests were conducted to explore the effects of La exposure on life-history characteristics and fecundity fitness, as showcased by quantitative variations from the individual level to population scale. In parallel, to further denote transgenerational caloric impacts of parental La exposure, bioenergetic profiles on newborn neonates were concurrently determined by measuring macromolecule forms in terms of proteins, glycogens and lipids to quantify nutritional alterations at progeny level. The results revealed that low-dose La exposure slightly stimulated the demographic potential and nutritional responses, exhibiting dose-dependent hormesis-like effects and promising non-toxicological potential to Daphnia, whereas high-dose La exposure of greater than 59.2 µg La L - 1, conspicuously imposed detrimental effects on quantity and quality of offspring, i.e. not only reducing body size, lifespan expectancy and reproductive output in a concentration-dependent way and resulting in lower population fitness by a dynamic life-table analysis, but eventually leading to the decrease of nutritional qualities and caloric contents on neonates. Taken together, these two-phase findings regarding the dose-related shift from hormesis to inhibition not only provided valuable insights into the complicated biological outcomes of La effects on environmentally-relevant organisms, but experimentally highlighted the significant implications of considering environmental and nutritional consequences in ecologically assessing the La-triggered risk at environmentally realistic occurrences, particularly on gradient scenarios crossing upstream and downstream of highly complex mining watersheds.

DNAzyme-powered cascade DNA walkers for sensitive detection of uracil DNA glycosylase activity.

Uracil-DNA glycosylase (UDG) is a crucial repair enzyme, which is considered a reliable biomarker due to its abnormal expression associated with serious diseases. Herein, DNAzyme-powered cascade walkers were proposed for sensitive detection of UDG. The cascade walkers consisted of a fixed walker and a subsequently activated free walker. The fixed walker was constructed on 13 nm AuNPs by loading a fixed walking strand (WS1) and a track strand 1 (TS1). The WS1 contained a DNAzyme sequence, which was pre-locked by a locking strand (LS) with an uracil base. The TS1 inserted an RNA cleavage site and sealed the same DNAzyme. The free walker tracks were conjugated on 25 nm AuNPs by modifying a FAM-labeled track strand 2 (TS2) with an RNA cleavage site. When UDG specifically recognized the LS, the WS1 was released with the assistance of Endo·IV. Then the WS1 continuously cleaved TS1s to drive the fixed walker, thus releasing many sequences containing DNAzyme. The released sequences acted as free walking strands (WS2s) to repeatedly cleave TS2s to power the free walker, which led to fluorescence accumulation. The cascade walkers successfully detected UDG with a limit of 8.5 × 10-5 U mL-1. The cascade walkers offer a new method for sensitively analyzing glycosylase.

Cascade primer exchange reaction-based amplification strategy for sensitive and portable detection of amyloid ß oligomer using personal glucose meters.

Amyloid ß oligomer (AßO) is an important biomarker for Almerzheimer's disease (AD) early diagnosis. In present study, cascade primer exchange reaction (PER) based amplification strategy was proposed for sensitive and portable detection of AßO using personal glucose meters (PGM). Two PER processes were employed here. In the primary PER, the hairpin template 1 (HT1) was designed with a primer binding domain, a primer extending domain and a blocking extending domain. The primers were designed to be modified on magbeads surface. Initially, the primer binding domain in HT1 was locked by AßO aptamer. When target AßO was present, aptamer bound with AßO and dissociated from HT1 to initiate the primary PER. The products acted as the primer of the secondary PER to hybridize with another hairpin template 2 (HT2), initiating the secondary PER and producing numerous ssDNA with repeated DNA-invertase binding sites. After binding with DNA-invertase, the obtained conjugates were magnetically separation to catalyze the conversion of sucrose to glucose, which were detected by a PGM. The strategy achieved a limit of detection of 0.22 pM with a linear ranged from 1 pM to 250 pM. Satisfactory reproducibility results were obtained in actual samples. This strategy provided a superior tool for sensitive and convenient detection of AßO, and showing a great potential in the early diagnosis of AD.

A novel chemotherapy strategy for advanced hepatocellular carcinoma: a multicenter retrospective study.

BACKGROUND: Chemotherapy is a common treatment for advanced hepatocellular carcinoma, but the effect is not satisfactory. The study aimed to retrospectively evaluate the effects of adding all-trans-retinoic acid (ATRA) to infusional fluorouracil, leucovorin, and oxaliplatin (FOLFOX4) for advanced hepatocellular carcinoma (HCC). METHODS: We extracted the data of patients with advanced HCC who underwent systemic chemotherapy using FOLFOX4 or ATRA plus FOLFOX4 at the Eastern Hepatobiliary Surgery Hospital, First Hospital of Jilin University, and Zhejiang Sian International Hospital and retrospectively compared for overall survival. The Cox proportional hazards model was used to calculate the hazard ratios for overall survival and disease progression after controlling for age, sex, and disease stage. RESULTS: From July 2013 to July 2018, 111 patients with HCC were included in this study. The median survival duration was 14.8 months in the ATRA plus FOLFOX4 group and 8.2 months in the FOLFOX4 only group ( P  < 0.001). The ATRA plus FOLFOX4 group had a significantly longer median time to progression compared with the FOLFOX4 group (3.6 months vs. 1.8 months, P  < 0.001). Hazard ratios for overall survival and disease progression were 0.465 (95% confidence interval: 0.298-0.726; P  = 0.001) and 0.474 (0.314-0.717; P  < 0.001) after adjusting for potential confounders, respectively. CONCLUSION: ATRA plus FOLFOX4 significantly improves the overall survival and time to disease progression in patients with advanced HCC.

All-Trans-Retinoic Acid Plus Oxaliplatin/Fluorouracil/Leucovorin for Advanced Hepatocellular Carcinoma with Pulmonary Metastasis: A Multicenter Retrospective Study.

Aim: To study the impact of All-trans-retinoic acid (ATRA) plus FOLFOX4 compared to FOLFOX4 alone in patients with advanced hepatocellular carcinoma (HCC) with pulmonary metastasis. Methods: The data of patients with advanced HCC who underwent systemic chemotherapy using FOLFOX4 or ATRA plus FOLFOX4 at the Eastern Hepatobiliary Surgery Hospital, First Hospital of Jilin University, Zhejiang Sian International Hospital and Fujian Cancer Hospital were retrospectively analyzed. The survival outcomes in the 2 groups were compared. Results: From May 2014 to July 2020, 66 patients were suitable to enter into this study. The median survival (14.0 vs 8.0 months, p=0.012), and the median time to progression in the ATRA plus FOLFOX4 group were both significantly longer than those in the FOLFOX4 group (8.7 vs 3.2 months, p=0.002). The 6 month-, 1 year- and 2 year- overall survival rates were also significantly better in the ATRA plus FOLFOX4 group (100.0%, 64.7% and 20.5%; respectively) than the FOLFOX4 group (59.4%, 21.9%, and 12.5%, respectively; p<0.001). Leukocytopenia, fatigue, anorexia, nausea, were the most common acute toxicities, but these were mostly NCI CTCAE Grade 1 or 2. There was no significant difference in adverse events between the two groups. Conclusion: ATRA plus FOLFOX4 significantly improved the survival outcomes in patients with advanced HCC with pulmonary metastasis.

Mycotoxin surveillance on wheats in Shandong province, China, reveals non-negligible probabilistic health risk of chronic gastrointestinal diseases posed by deoxynivalenol.

Abnormal climate changes have resulted in over-precipitation in many regions. The occurrence and contamination levels of mycotoxins in crops and cereals have been elevated largely. From 2017 to 2019, we did investigation targeting 15 mycotoxins shown in the wheat samples collected from Shandong, a region suffering over-precipitation in China. We found that deoxynivalenol (DON) was the dominant mycotoxin contaminating wheats, with detection rates 304/340 in 2017 (89.41%), 303/330 in 2018 (91.82%), and 303/340 in 2019 (89.12%). The ranges of DON levels were < 4 to 580 µg/kg in 2017, < 4 to 3070 µg/kg in 2018, and < 4 to 1540 µg/kg in 2019. The exposure levels were highly correlated with local precipitation. Male exposure levels were generally higher than female's, with significant difference found in 2017 (1.89-fold, p = 0.023). Rural exposure levels were higher than that of cities but not statistically significant (1.41-fold, p = 0.13). Estimated daily intake (EDI) and margin of exposure (MoE) approaches revealed that 8 prefecture cities have probabilistically extra adverse health effects (vomiting or diarrhea) cases > 100 patients in 100,000 residents attributable to DON exposure. As a prominent wheat-growing area, Dezhou city reached ~ 300/100,000 extra cases while being considered as a major regional contributor to DON contamination. Our study suggests that more effort should be given to the prevention and control of DON contamination in major wheat-growing areas, particularly during heavy precipitation year. The mechanistic association between DON and chronic intestinal disorder/diseases should be further investigated.

Terbium (III)-based Metallacrowns with aggregation-induced emission feature coupled with cu (II) for fluorescence detection of cysteine.

The Metallacrowns (MCs) composed of repeated [Metal-N-O] subunits are a type of new material, but the MCs have not been developed and utilized in analytical applications. This essay reports on a new kind of terbium(III)-based Metallacrowns (Tb-MCs) with aggregation-induced emission (AIE) feature to build a sensing platform. It is first time that Tb-MCs are able to aggregate to larger aggregates in water along with a bright green emission, so that the property makes it possible to apply in biosensing. Thereafter, the AIE of Tb-MCs can be quenched effectively by Cu2+. Based on the high affinity of thiol to Cu2+, cysteine (Cys) recovers the fluorescence of Tb-MCs in the presence of Cu2+. There is a good linear range varying from 0.02 to 20 µM with a low limit of detection (LOD) 9.67 nM of Cys. In the end, this novel probe is also successfully applied to the determination of Cys in human serum with satisfactory results.

Primer-template conversion-based cascade signal amplification strategy for sensitive and accurate detection of polynucleotide kinase activity.

Here, a primer-template conversion-based cascade signal amplification strategy is described for the sensitive detection of polynucleotide kinase (PNK) activity. This strategy integrated rolling circle amplification (RCA) and multiple-repeated-strand displacement amplification (MRSDA) with G-quadruplex based fluorescence lighting-up assay. A delicate dumbbell-shaped DNA probe with 5'-hydroxyl terminus was designed, in which G-quadruplex and half recognition site of nicking enzyme Nb.BbvCI were encoded in two loops respectively. Under the action of PNK, the 5' terminus on dumbbell probe was firstly phosphorylated, and then the dumbbell was cyclized with the catalyzation of T4 ligase to become the RCA template. The RCA process produced multiple copies of the prolonged primer. After that, under the assistance of nicking enzyme Nb.BbvCI, a primer-template conversion occurred, which converted the primer and template of RCA into the template and primer of the subsequent MRSDA, respectively. The MRSDA generated multiple repeated ssDNA sequences which possessed G-quadruplexes for outputting signal by lighting-up fluorescence of thioflavin T (ThT). The cascade signal amplification of RCA and MRSDA provided high detection sensitivity, and the target-dependence of template in cascade signal amplification led to a low background. The method showed excellent detection limit of 0.2 × 10-6 U µL-1 in buffer and 5 cells in cell lysate sample. Moreover, this method displayed favorable selectivity when interfering proteins were present. The developed strategy has good practical potential for PNK activity detection in clinical diagnosis and medical research.

Occurrence and dietary exposure of heavy metals in marketed vegetables and fruits of Shandong Province, China.

The contamination of heavy metals in vegetables and fruits is a serious threat to food safety and human health. The present study was designed to investigate the occurrence and dietary exposure of lead (Pb), arsenic (As), cadmium (Cd), and mercury (Hg) in vegetables and fruits in Shandong Province, China. Results demonstrated that the mean level of total heavy metals was 30.25 µg/kg. The most frequently found heavy metal was Cd (69.2%) with a mean value of 11.54 µg/kg. The mean exposure values of Pb, As, Cd, and Hg in vegetables were 0.052, 0.045, 0.038, and 2.40 × 10-3 µg/kg bw/day, respectively. Moreover, the calculated hazard quotient (HQ) values of mean levels for these four heavy metals were all less than 1, indicating the health risk of heavy metal exposure caused by vegetable consumption was low. This study has displayed baseline information on heavy metal contamination in vegetables and fruits, which can provide useful data support for the formulation of relevant standards and government management.

Binding mediated MNAzyme signal amplification strategy for enzyme-free and label-free detection of DNA-binding proteins.

A novel MNAzyme signal amplification strategy was developed for enzyme-free and label-free detection of DNA-binding proteins. This strategy relied on the binding-mediated MNAzyme cleavage and G-quadruplex-based light-up fluorescence switch. Three DNA sequences were designed to construct the MNAzyme in which DNA1 (including half binding site of the target protein and a toehold sequence) and DNA2 (including another half binding site of the target protein and one MNAzyme partzyme) firstly hybridized. The target protein recognized the binding sites on DNA1-DNA2 hybrid to form a stable protein-DNA1-DNA2 conjugates. Then, the MNAzyme was assembled with the presence of DNA3 which contained another MNAzyme partzyme and the complementary sequence of DNA1. The active MNAzyme cleaved DNA4 to release the G-quadruplex that was locked in the stem of DNA4. Finally, N-methyl mesoporphyrin IX (NMM) was inserted into the released G-quadruplex structure and the fluorescence signal was turned on. Taking nuclear factor-κB p50 (NF-κB p50) as the model, the limit of detection was low to 0.14 nM. Furthermore, the sequence-specific recognition of NF-κB p50 with DNA displayed excellent selectivity and specificity. The results in present work showed that this strategy will be a promising tool for DNA-binding proteins analysis in biomedical exploration and clinical diagnosis.

MOF@MnO2nanocomposites prepared usingin situmethod and recyclable cholesterol oxidase-inorganic hybrid nanoflowers for cholesterol determination.

In this work, through thein situgrowth of MnO2nanosheets on the surface of terbium metal-organic frameworks (Tb-MOFs), MOF@MnO2nanocomposites are prepared and the fluorescence of Tb-MOFs is quenched significantly by MnO2. Additionally, the hybrid nanoflowers are self-assembled by cholesterol oxidase (ChOx) and copper phosphate (Cu3(PO4)2·3H2O). Then a new strategy for cholesterol determination is developed based on MOF@MnO2nanocomposites and hybrid nanoflowers. Cholesterol is oxidized under the catalysis of hybrid nanoflowers to yield H2O2, which further reduces MnO2nanosheets into Mn2+. Hence, the fluorescence recovery of Tb-MOFs is positively correlated to the concentration of cholesterol in the range of 10 to 360µM. The limit of detection (LOD) of cholesterol is 1.57µM. On the other hand, the hierarchical and confined structure of ChOx-inorganic hybrid nanoflowers greatly improve the stability of the enzyme. The activity of hybrid nanoflowers remains at a high level for one week when stored at room temperature. Moreover, the hybrid nanoflowers can be collected by centrifugation and reused. The activity of hybrid nanoflowers can continue at a high level for five cycles of determination. Therefore, it can be concluded that the hybrid nanoflowers are more stable and more economic than free enzymes, and they show a similar sensitivity and specificity to cholesterol compared with free ChOx. Finally, this strategy has been further validated for the determination of cholesterol in serum samples with satisfactory recoveries.

pH-modulated aggregation-induced emission of Au/Cu nanoclusters and its application to the determination of urea and dissolved ammonia.

A fluorescence platform is designed based on aggregation-induced emission of Au/Cu nanoclusters (Au/Cu NCs) driven by pH value. When pH increases from 6.0 to 7.0, Au/Cu NCs change from aggregation to dispersion, accompanied by the oxidation of Cu cores. Under the catalysis of urease, urea is hydrolysed to release ammonia, which further undergoes a hydrolysis reaction to produce OH-, causing the pH to increase. The fluorescence of Au/Cu NCs quenches linearly at 590 nm with the excitation wavelength at 320 nm when the concentration of urea varies from 5.0 to 100 µM. The limit of detection (LOD) and limit of quantification (LOQ) of urea are 2.23 and 7.45 µM, respectively. Combined with headspace single-drop microextraction technology, Au/Cu NCs are employed to monitor dissolved ammonia with low-cost and simple operation. The linear range of dissolved ammonia is from 20 to 300 µM. The LOD and LOQ of dissolved ammonia are 7.04 and 23.4 µM, respectively. The relative standard deviation (RSD) values of the intra-day and inter-day precision of urea are 2.4-3.0% and 3.0-3.7%, respectively, and those of dissolved ammonia are in the range 3.4-5.1% (intra-day precision) and 4.2-5.8% (inter-day precision). No interferences have been indentified in the determination of urea and dissolved ammonia. Finally, the proposed method has been applied to determine urea in human urine samples and dissolved ammonia in water samples with satisfactory results.Graphical abstract The pH increase produces the dispersion and decomposition of Au/Cu NCs, leading to the fluorescence quenching. Both urea and dissolved ammonia are detected successfully because they cause the pH change to alkaline.

Occurrence of polycyclic aromatic hydrocarbons in fried and grilled fish from Shandong China and health risk assessment.

Diet is the main way for the human body to ingest polycyclic aromatic hydrocarbons (PAHs). In this study, the occurrence, dietary exposure, and health risks of 15 PAHs in 31 fried and grilled fish samples were investigated, which were collected from the Shandong Province of China. The results showed that benzo[a]pyrene (BaP) of 5 samples exceeded the European Union (EU) limit value. Naphthalene (NaP) and fluorene (Fle) were present in all samples, and the average concentration of ∑15PAHs was 91.1 µg/kg, with light PAHs dominated. The average contamination level of ∑15PAHs in fried and grilled fish was distributed differently, and there seemed to be more PAH contamination in the grilled samples. The results of the margin of exposure (MOE) suggested that PAH ingestion through fried and grilled fish did not imply significant toxicological concern for consumers in Shandong. The incremental lifetime cancer risk (ILCR) values for the consumption of fried and grilled fish were higher than 1 × 10-6, indicating a potential health risk in the adult population. The study provides baseline health information on PAH intake by residents due to dietary exposure to fried and grilled fish food products, suggesting that health risk monitoring of PAHs in such foods should be continually performed.

Tuning the conformation of G-quadruplexes by sodium and potassium ions: application to photometric and fluorometric determination of amyloid ß(1-40).

A dual channel method is described for the determination of the amyloid-ß peptide Aß(1-40) that is associated with Alzheimer's disease. The method exploits (a) conformational changes of a G-quadruplex that are triggered by Na+ and K+ ions and (b) the strong affinity between Aß(1-40) and Cu2+. A G-quadruplex DNA forms an antiparallel structure in the presence of Na+ and can catalyze the oxidation of tetramethylbenzidine by H2O2 system in the presence of Cu2+ to form a visible blue color. If, however, Cu2+ binds to Aß(1-40), the blue color is no longer formed. Measuring the absorption decrease at 452 nm, the determination of Aß(1-40) is realized. If K+ is added to the Na+-containing buffer, the antiparallel G-quadruplex DNA is transformed to parallel. This leads to the insertion of protoporphyrin IX (PPIX) into the G-quadruplex and generates enhanced fluorescent signal, with excitation/emission wavelength at 410/630 nm. The G-quadruplex then catalyzes the metalation of PPIX by Cu2+, and the fluorescence intensity decreases. In the presence of Aß(1-40), the formation of Aß(1-40)-Cu2+ triggers the recovery of the fluorescence. The Na+/K+-induced tuning of the conformation of the G-quadruplex with the same sequence enables dual (colorimetric and fluorometric) determination of Aß(1-40), with detection limits of 4.9 pM and 2.3 pM, respectively. The cost is quite low since the developed strategy is label free and enzyme free by using low-cost DNA and Cu2+. More importantly, the dual channel determination operation is very simple without any further modification process. Tuning the conformation of G-quadruplexes by sodium(I) and potassium(I): application to photometric and fluorometric determination of amyloid ß(1-40).