Synthesis and Characteristics of Polymer-Mediated Curcumin Molecular Imprinting for Quantitative Determination of Curcumin in Food Samples.

In this study, a molecularly imprinted polymer (MIP)-based extraction process for determining curcumin in food samples was carried out. MIP and NIP were thermally synthesized in acetonitrile solvent (porogen) using methacrylic acid as a functional monomer, ethylene glycol dimethacrylate as a cross-linking agent, azobisisobutyronitrile as an initiator, and curcumin as a template molecule. Parameters affecting the synthesis process, such as temperature, the ratio of the components in the reaction, and the extraction solvent, were investigated. The characteristics of the synthesized material were examined using infrared spectroscopy and scanning electron microscopy. The maximum adsorption capacity of the material was found to be 1.34 mg/g MIP with an adsorption efficiency of 89.96% for MIP and 12.35% for NIP. The MIP material exhibited high selectivity for curcumin compared to other compounds such as quercetin (18.00%), rutin (14.74%), and ketoconazole (0.00%). The analysis method for curcumin using the MIP material was performed with validated parameters including linear range (1 - 25 mg/L, r2 = 0.9997), accuracy (recovery rate of 90.90 %), precision (RSDR = 0.338 %, RSDr = 1.591 %), detection limit (0.051 mg/L), and quantification limit (0.156 mg/L). The validation results indicated that the HPLC-DAD method was entirely suitable for analyzing the curcumin content in food samples.

Analytical techniques for determination of heavy metal migration from different types of locally made plastic food packaging materials using ICP-MS.

Plastic food packaging is an essential element for customer convenience and the preservation of food quality. Nonetheless, heavy metals in the packaging materials, either intentionally or nonintentionally added, can be transferred to the food. Therefore, determining heavy metal contents in these packaging materials is essential. In this study, heavy metals, including Co, Ge, As, Cd, Sb, Pb, Al, and Zn from different intrinsic plastic food packaging materials were analyzed using the inductively coupled plasma-mass spectrometry (ICP-MS) method. Moreover, the migration of these elements into the environment was also investigated. This method is validated following the new technique's requirements, which include linearity range, accuracy, precision, the limit of detection (LOD), and the limit of quantitation (LOQ). The method has been suitably validated with the regression equation from the standards prepared in HNO3 1% v/v. The linear range was found to be ~1-20 ng mL-1 for Co, Ge, As, Cd, Sb, and Pb and 5-80 ng mL-1 for Al and Zn elements. The LODs are ~0.10, 0.25, 0.12, 0.13, 0.11, 0.12, 0.61, and 0.85 ng mL-1, and the LOQs are 0.33, 0.83, 0.40, 0.43, 0.36, 0.40, 2.01, and 2.81 ng mL-1 obtained for Co, Ge, As, Cd, Sb, Pb, Al, and Zn, respectively. In addition, the recovery percentages received ranged 85.4%-94.1% for Co, 82.6%-95.1% for Ge, 86.3%-97.9% for As, 87.3%-96.3% for Cd, 88.0%-104.4% for Sb, 96.3%-106.0% for Pb, 88.4%-104.0% for Al, and 95.1%-99.7% for Zn. Finally, the migration of these heavy metals from polypropylene (PP) and polystyrene (PS) into foodstuffs was also simulated according to EU legislation, showing that the most leached element was Zn, followed by Al and Pd, with the migration of ~8.38% and ~0.41%, and ~0.19%, respectively.

Rickettsia felis and species of fleas parasitizing on household dogs in the Central Highlands of Vietnam.

Rickettsia felis is an obligate intracellular gra m-negative bacterium that belongs to the family of Rickettsiaceae. Ctenocephalides felis, cat flea, is the primary vector of the bacteria. The flea is the most common ectoparasite in dogs and associated with flea-borne spotted fever in humans. Information on R. felis and flea species parasitizing on dogs in Vietnam is limited. This study aimed to identify the species of fleas collected from dogs in the Central Highlands of Vietnam and detected the existence of R. felis in these fleas utilizing molecular tools. Morphological identification of 1618 fleas and molecular confirmation revealed the predominance of C. felis orientis parasitizing on dogs in the Central Highlands of Vietnam. Sixty-eight out of 100 fleas collected from household dogs were positive for spotted fever group rickettsiae; whilst R. felis was detected in 97.06 % (66/68) of C. felis orientis and C. felis felis. The results of this study indicate the potentially high risk of R. felis infection to humans and animals.

Investigation of arsenic contamination in groundwater using hydride generation atomic absorption spectrometry.

The validated hydride generation atomic absorption spectrometry (HG-AAS) method has been used to investigate total arsenic in groundwater. Under optimal experimental conditions, the concentration of arsenic in groundwater can be analysed in the range of 0.5 to 50 µg/L, with a method detection limit of 0.15 µg/L. Its recovery in the field is from 96.3 to 99.8%, with high repeatability. The method was used to observe the total arsenic pollution in groundwater collected in Phu Tho Province, Vietnam. A total of 364 groundwater samples were analysed. The results showed that arsenic pollution was significant, with 15.93% of the samples higher than the maximum permissible level of arsenic. About 20.69% of the contaminated samples had a total arsenic ten times higher (100 µg/L) than the maximum permissible level of arsenic. The pollution source was also considered by comparing the arsenic level in the groundwater with arsenic in the surface water in the same areas. Thus, the use of the high-accuracy and sensitive method, HG-AAS, supplies valuable data on groundwater pollution for water resources management and environmental protection.

Combined Gap-Polymerase Chain Reaction and Targeted Next-Generation Sequencing Improve α- and ß-Thalassemia Carrier Screening in Pregnant Women in Vietnam.

Vietnam has a high thalassemia burden. We collected blood samples from 5880 pregnant Vietnamese women during prenatal health checks to assess thalassemia carrier frequency using combined gap-polymerase chain reaction (gap-PCR) and targeted next-generation sequencing (NGS). Thalassemia carriers were identified with prevalence of 13.13% (772), including 7.82% (460) carriers of α-thalassemia (α-thal), 5.31% (312) carriers of ß-thalassemia (ß-thal), and 0.63% (37) concurrent α-/ß-thal carriers. Deletional mutations (368) accounted for 80.0% of α-thal carriers, of which, --SEA (Southeast Asian) (n = 254; 55.0%) was most prevalent, followed by the -α3.7 (rightward) (n = 66; 14.0%) and -α4.2 (leftward) (n = 45; 9.8%) deletions. Hb Westmead (HBA2: c.369C>G) (n = 53) and Hb Constant Spring (Hb CS or HBA2: c.427T>C) (in 28) are the two most common nondeletional α-globin variants, accounting for 11.5 and 6.0% of α-thal carriers. We detected 11 different ß-thal genotypes. Hb E (HBB: c.79G>A) (in 211) accounted for 67.6% of ß-thal carriers. The most common ß-thal genotypes were associated with mutations at codon 17 (A>T) (HBB: c.52A>T), codons 41/42 (-TTCT) (HBB: c.126_129delCTTT), and codon 71/72 (+A) (HBB: c.217_218insA) (prevalence 0.70%, 0.68%, and 0.2%, respectively). Based on mutation frequencies calculated in this study, estimates of 5021 babies in Vietnam are affected with clinically severe thalassemia annually. Our data suggest a higher thalassemia carrier frequency in Vietnam than previously reported. We established that combining NGS with gap-PCR creates an effective large-scale thalassemia screening method that can detect a broad range of mutations.

Virtual screening and rational design of antioxidant peptides based on tryptophyllin L structures isolated from the Litoria rubella frog.

Discovery of natural antioxidants has been carried out for decades relying mainly on experimental approaches that are commonly associated with time and cost demanding biochemical assays. The maturation of quantitative structure activity relationship (QSAR) modelling has provided an alternative approach for searching and designing antioxidant compounds with alleviated costs. As a contribution to this approach, this work aimed to establish a fragment-based 3D-QSAR procedure to discover and design potential antioxidants based on tryptophyllin L structures isolated from the red tree frog Litoria rubella. A force field and a Gaussian 3D-QSAR model were built to screen for potential antioxidants from tripeptide fragments covering all sequences of tryptophyllin L database. Among those, PWY(NH2 ) corresponding tryptophyllin L 4.1 was predicted to have the highest 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) radical cation (ABTS+ ·) scavenging capability. Two newly designed peptides PYW and PYW(NH2 ) together with PWY(NH2 ), tryptophyllin L 4.1, and the reference peptide PWY were synthesized and subjected to two antioxidant assays including ABTS scavenging and ferric reducing antioxidant power assays. Although the experimental TEAC values of the five peptides were roughly similar to those from predictions, the activity order was not in agreement with the predictions. The dissimilarities were accounted by the difference in the experimental procedures, the deviation of modelling regression, and the synergetic effect of structural and experimental features. The ABTS radical scavenging assays revealed that all the tested peptides were strong ABTS+ · scavengers with the antioxidant capabilities approximately twice as high as trolox and higher than glutathione. The ferric reducing activities of the peptides were, on the other hand, much weaker than that of trolox suggesting different antioxidant mechanisms inserted by trolox and the peptides. This work was a demonstration that 3D-QSAR methods can be employed in conjunction with experimental methods to effectively detect and design antioxidant peptides.

A Validated Method for the Simultaneous Determination of Methamphetamine and 3,4-Methylenedioxy-N-methamphetamine in Blood-Based Liquid Chromatography-Tandem Mass Spectrometry.

A liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method has been validated for the simultaneous determination of methamphetamine (MA) and 3,4-methylenedioxy-N-methamphetamine (MDMA) in the blood sample. Under the optimal experimental conditions, the concentration of MA can be determined in the range from 1 µg/L to 5000 µg/L with the method detection limit (MDL) of 0.31 µg/L. The range from 0.5 to 500 µg/L is observed for the determination of MDMA with the MDL down to 0.25 µg/L. The practical applicability of the method is performed with the recovery ranging from 85.3% to 94% for MA and from 86.9% to 95.5% for MDMA. At the different concentrations of drugs, the relative standard deviations (RSD) for both MA and MDMA are lower than 5.7%. The method was applied to analyse 1995 blood samples that had been collected from the Forensic Medicine Centre of Ho Chi Minh City. The results showed 1.75% positive with MA and 0.25% positive with MDMA. These two drugs take 10% of the total drugs positive samples. By using deuterium-labelled methamphetamine-d5 and 3,4-methylenedioxy-N-methamphetamine-d5 as the internal standards in the determination and the use of MS/MS in multiple reaction monitoring mode signal readout, the method exhibits robustness specificity and can be applied in simultaneous determination of MA and MDMA in blood with high selectivity and sensitivity.

A Stakeholder Survey on Live Bird Market Closures Policy for Controlling Highly Pathogenic Avian Influenza in Vietnam.

Extensive research in Vietnam and elsewhere has shown that live bird markets (LBMs) play a significant role in the ecology and zoonotic transmission of avian influenzas (AIs) including H5N1 and H7N9. Vietnam has a large number of LBMs reflecting the consumer preferences for live poultry. Under pressure to mitigate risks for H7N9 and other zoonotic AIs, Vietnam is considering, among other mitigation measures, temporary closures of LBMs as a policy to reduce risk of AI outbreaks. However, the efficacy of market closure is debated, particularly because little is known about how poultry traders may react, and whether trading may emerge outside formal marketplaces. Combining efforts of anthropologists, economists, sociologists, and veterinarians can be useful to elucidate the drivers behind poultry traders' reactions and better understanding the barriers to implementing risk mitigation measures. In this paper, we present results from a stakeholder survey of LBM stakeholders in Vietnam. Our qualitative data show that trading outside formal markets is very likely to occur in the event of a temporary LBM market closure. Our data show that the poultry value chain in Vietnam remains highly flexible, with traders willing and able to trade poultry in many possible locations. Our results indicate that simplification of the poultry value chain along with strict enforcement, engagement of stakeholders, and adequate communication would be a necessary prerequisite before market closure could be an effective policy.

Investigating poultry trade patterns to guide avian influenza surveillance and control: a case study in Vietnam.

Live bird markets are often the focus of surveillance activities monitoring avian influenza viruses (AIV) circulating in poultry. However, in order to ensure a high sensitivity of virus detection and effectiveness of management actions, poultry management practices features influencing AIV dynamics need to be accounted for in the design of surveillance programmes. In order to address this knowledge gap, a cross-sectional survey was conducted through interviews with 791 traders in 18 Vietnamese live bird markets. Markets greatly differed according to the sources from which poultry was obtained, and their connections to other markets through the movements of their traders. These features, which could be informed based on indicators that are easy to measure, suggest that markets could be used as sentinels for monitoring virus strains circulating in specific segments of the poultry production sector. AIV spread within markets was modelled. Due to the high turn-over of poultry, viral amplification was likely to be minimal in most of the largest markets. However, due to the large number of birds being introduced each day, and challenges related to cleaning and disinfection, environmental accumulation of viruses at markets may take place, posing a threat to the poultry production sector and to public health.

Proteolysis-mediated protection of gold nanoparticles for sensitive activity assay of peptidases.

Rapid, sensitive and quantitative assays for peptide hydrolysis enzymes are of paramount importance for drug development and in the diagnosis of disease. Here, we proposed a novel biosensor for sensitive and selective active screening of peptidases. This strategy relies on the proteolysis-mediated protection of gold nanoparticles (AuNPs) that were decorated with biotin-labeled substrate peptides and can be aggregated by streptavidin. Enzyme-mediated protection of AuNPs offers this strategy high specificity, and the use of AuNPs additionally allows a visual and homogeneous assay format, thus permitting improved simplicity and throughput of the assays. As a model case, desirable selectivity and sensitivity in peptidase assay were achieved in the active assays of pancreatic elastase with a wide linear response range from 0.005 to 0.10 U/mL and a detection limit of 0.003 U/mL. The results indicated that this strategy can offer a simple, robust and convenient platform for visualized peptidase activity analysis and related biochemical studies with high sensitivity and selectivity.

Enzyme-catalyzed assembly of gold nanoparticles for visualized screening of DNA base excision repair.

Activity screening of DNA base excision repair (BER) enzymes is a crucial step for understanding numerous fundamental biochemical processes. A novel label-free homogeneous technique is developed for visualized uracil-DNA glycosylase (UDG) activity assay using gold nanoparticles (AuNPs). This strategy relies on the enzyme-catalyzed assembly of AuNPs decorated with DNA probes. In the presence of endonuclease IV (an enzyme which can further hydrolyze the products from UDG-catalyzed reaction), the substrate DNA selectively interacts with UDG followed by the efficient release of a single-strand probe. The released single-strand probe then makes the network-like assembly of decorated AuNPs to provide a visible signal for UDG activity. This strategy that can be performed in a label-free homogeneous assay format improved the duration, the simplicity and the throughput of UDG activity screening. The results provided in the present study revealed that this strategy could hold great potential as a robust, convenient and visualized platform for activity screening of uracil-DNA glycosylases with high selectivity and desirable sensitivity.