A Versatile Strategy of Designing Gold Nanoparticle-cDNA Nanoprobes in Developing Aptamer-Based Lateral Flow Assay for Small-Molecule Detection.

Aptamer-based lateral flow assay (Apt-LFA) has shown promising applications for small-molecule detection. However, the design of the AuNP (gold nanoparticle)-cDNA (complementary DNA) nanoprobe is still a big challenge due to the moderate affinity of the aptamer to small molecules. Herein, we report a versatile strategy to design a AuNPs@polyA-cDNA (poly A, a repeat sequence with 15 A bases) nanoprobe for small-molecule Apt-LFA. The AuNPs@polyA-cDNA nanoprobe contains a polyA anchor blocker, complementary DNA segment to DNA on the control line (cDNAc), partial complementary DNA segment with aptamer (cDNAa), and auxiliary hybridization DNA segment (auxDNA). Using adenosine 5'-triphosphate (ATP) as a model target, we optimized the length of auxDNA and cDNAa and achieved a sensitive detection of ATP. In addition, kanamycin was used as a model target to verify the universality of the concept. Therefore, this strategy can be easily extended to other small molecules; therefore, high application potential in Apt-LFAs can be envisaged.

Enzymatic preparation and potential applications of agar oligosaccharides: a review.

Oligosaccharides derived from agar, that is, agarooligosaccharides and neoagarooligosaccharides, have demonstrated various kinds of bioactivities which have been utilized in a variety of fields. Enzymatic hydrolysis is a feasible approach that principally allows for obtaining specific agar oligosaccharides in a sustainable way at an industrial scale. This review summarizes recent technologies employed to improve the properties of agarase. Additionally, the relationship between the degree of polymerization, bioactivities, and potential applications of agar-derived oligosaccharides for pharmaceutical, food, cosmetic, and agricultural industries are discussed. Engineered agarase exhibited general improvement of enzymatic performance, which is mostly achieved by truncation. Rational and semi-rational design assisted by computational methods present the latest strategy for agarase improvement with greatest potential to satisfy future industrial needs. Agarase immobilized on magnetic Fe3O4 nanoparticles via covalent bond formation showed characteristics well suited for industry. Additionally, albeit with the relationship between the degree of polymerization and versatile bioactivities like anti-oxidants, anti-inflammatory, anti-microbial agents, prebiotics and in skin care of agar-derived oligosaccharides are discussed here, further researches are still needed to unravel the complicated relationship between bioactivity and structure of the different oligosaccharides.

Inactivation of Escherichia coli O157:H7 in apple juice via induced electric field (IEF) and its bactericidal mechanism.

Non-conventional heating technology based on electric fields can be utilized to process liquid foods. In this study, the induced electric field (IEF) was investigated to clarify its inactivation mechanism on E.coli. Staining results show that inactivation of E.coli by IEF can be attributed to the reversible destruction of the cell membrane, followed by the denaturation of intracellular enzymes, and finally the irreversible rupture of the cell membrane. The increased levels of extracellular proteins and nucleic acids were also observed. IEF treatment at 400 Hz and 800 V (or 53 V/cm) results in a reduction of 4.5 log CFU·mL-1 in the number of E.coli. Storage life analysis shows that IEF treatment can improve the stability of apple juice and the content of bioactive components. Thus, IEF is a potential technique for liquid food processing.

Non-thiolated nucleic acid functionalized gold nanoparticle-based aptamer lateral flow assay for rapid detection of kanamycin.

A novel Apt-LFA has been established for kanamycin based on non-thiolated nucleic acid-modified colloidal gold nanoprobe (AuNPs@polyA-DNA). The improvement in nucleic acid hybridization speed and efficiency was verified by modifying AuNPs with polyA-DNA strands instead of thiolated oligonucleotides (SH-DNA) strands. Moreover, the AuNPs@polyA-DNA was explored to apply in an Apt-LFA. The experimental factors including the concentration of the aptamer, the concentration of SA-DNAT conjugate, the incubation time, and temperature were carefully investigated. In addition, the kanamycin aptamer was modified by extending several bases at its end to modulate the hybridization complementary strand, which was found to significantly improve the performance of Apt-LFA. Under optimal experimental conditions, the Apt-LFA can detect kanamycin in honey with a LOD of 250 ng mL-1 by the naked eyes. A linear range of 50-1250 ng mL-1 was obtained with a LOD of 15 ng mL-1 in honey by a portable reader. The Apt-LFA was successfully applied to the detection of kanamycin in honey with recoveries of 95.1-105.2%.

Efficient Laser-Induced Construction of Oxygen-Vacancy Abundant Nano-ZnCo2 O4 /Porous Reduced Graphene Oxide Hybrids toward Exceptional Capacitive Lithium Storage.

Recently, binary ZnCo2 O4 has drawn enormous attention for lithium-ion batteries (LIBs) as attractive anode owing to its large theoretical capacity and good environmental benignity. However, the modest electrical conductivity and serious volumetric effect/particle agglomeration over cycling hinder its extensive applications. To address the concerns, herein, a rapid laser-irradiation methodology is firstly devised toward efficient synthesis of oxygen-vacancy abundant nano-ZnCo2 O4 /porous reduced graphene oxide (rGO) hybrids as anodes for LIBs. The synergistic contributions from nano-dimensional ZnCo2 O4 with rich oxygen vacancies and flexible rGO guarantee abundant active sites, fast electron/ion transport, and robust structural stability, and inhibit the agglomeration of nanoscale ZnCo2 O4 , favoring for superb electrochemical lithium-storage performance. More encouragingly, the optimal L-ZCO@rGO-30 anode exhibits a large reversible capacity of ≈1053 mAh g-1 at 0.05 A g-1 , excellent cycling stability (≈746 mAh g-1 at 1.0 A g-1 after 250 cycles), and preeminent rate capability (≈686 mAh g-1 at 3.2 A g-1 ). Further kinetic analysis corroborates that the capacitive-controlled process dominates the involved electrochemical reactions of hybrid anodes. More significantly, this rational design holds the promise of being extended for smart fabrication of other oxygen-vacancy abundant metal oxide/porous rGO hybrids toward advanced LIBs and beyond.

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.

Preparation, characterization and physicochemical properties of novel low-phosphorus egg yolk protein.

BACKGROUND: In order to supply adequate dietary protein for chronic kidney disease (CKD) patients while simultaneously controlling phosphorus intake, a novel method was developed for the preparation of low-phosphorus egg yolk protein (LPYP) using alkaline protease auxiliary dephosphorization. In addition, the physicochemical properties of LPYP were studied. RESULTS: In comparison with raw egg yolk protein (RYP) and defatted egg yolk protein (DFYP), LPYP was found to exhibit differences in amino acid (AA) composition, protein secondary structure, surface hydrophobicity, solubility and emulsion stability. It was observed that dephosphorization improved the AA composition, soluble protein content and dissolution stability of egg yolk protein. In addition, phosphate groups were found to impose a critical influence on the emulsion stability and particle size distribution. The final phosphorus to protein mass ratio (P/Pro) of LPYP was 5.64, which met the requirements of a protein diet for CKD patients. The FAO/WHO mode closeness and stability coefficient were 0.958 and 98.62% respectively. CONCLUSION: LPYP can be effectively obtained by alkaline protease hydrolysis and subsequent alkali dephosphorization. The prepared LPYP can be considered to be a type of safe and suitable protein resource for CKD patients. © 2018 Society of Chemical Industry.

Erratum: Xie, Z.-J.; Bao, X.-Y.; Peng, C.-F. Highly Sensitive and Selective Colorimetric Detection of Methylmercury Based on DNA-Functionalized Gold Nanoparticles. Sensors 2018, 18, 2679.

The authors wish to make the following corrections to their paper [...].

Highly Sensitive and Selective Colorimetric Detection of Methylmercury Based on DNA Functionalized Gold Nanoparticles.

A new colorimetric detection of methylmercury (CH3Hg⁺) was developed, which was based on the surface deposition of Hg enhancing the catalytic activity of gold nanoparticles (AuNPs). The AuNPs were functionalized with a specific DNA strand (HT7) recognizing CH3Hg⁺, which was used to capture and separate CH3Hg⁺ by centrifugation. It was found that the CH3Hg⁺ reduction resulted in the deposition of Hg onto the surface of AuNPs. As a result, the catalytic activity of the AuNPs toward the chromogenic reaction of 3,3,5,5-tetramethylbenzidine (TMB)-H2O2 was remarkably enhanced. Under optimal conditions, a limit of detection of 5.0 nM was obtained for CH3Hg⁺ with a linear range of 10⁻200 nM. We demonstrated that the colorimetric method was fairly simple with a low cost and can be conveniently applied to CH3Hg⁺ detection in environmental samples.

Sol-gel encapsulation of pullulanase in the presence of hybrid magnetic (Fe3O4-chitosan) nanoparticles improves thermal and operational stability.

Pullulanase was sol-gel encapsulated in the presence of magnetic chitosan/Fe3O4 nanoparticles. The resulting immobilized pullulanase was characterized by scanning electron microscopy, vibrating sample magnetometry, Fourier transform infrared spectroscopy and thermogravimetric analysis. The results showed that the addition of pullulanase created a more regular surface on the sol-gel matrix and an enhanced magnetic response to an applied magnetic field. The maximal activity retention (83.9%) and specific activity (291.7 U/mg) of the immobilized pullulanase were observed under optimized conditions including an octyltriethoxysilane:tetraethoxysilane (OTES:TEOS) ratio of 1:2 and enzyme concentration of 0.484 mg/mL sol. The immobilized enzyme exhibited good thermal stability. When the temperature was above 60 °C, the immobilized pullulanase showed significantly higher activity than the free enzyme (p < 0.01); enzyme immobilized by simple sol-gel encapsulation and co-immobilized by crosslinking-encapsulation retained 52 and 69% of their initial activity after 5 h at 62 °C, respectively, compared to 11% for the free enzyme. Moreover, the stability of the pullulanase was improved by crosslinking-encapsulation, as the enzyme retained more than 85 and 81% of its original activity after 5 and 6 consecutive reuses, respectively, compared to 80 and 72% of its original activity for simple sol-gel encapsulated enzymes. This indicated the leakage of enzyme molecules through the pores of the gel was substantially abated by cross-linking. Such immobilized pullulanase provides high stability and ease of enzyme recovery, characteristics that are advantageous for applications in the food industry that involve continuous starch processing.

Changes of gut microbiota structure and morphology in weaned piglets treated with fresh fermented soybean meal.

This study investigated the effects of dietary fresh fermented soybean meal (FSM) on the intestinal microbiota and metabolites, bacterial enzyme activity and intestinal morphology of weaning piglets. A total of 64 weaned piglets were randomly allocated into two treatments. A corn-soybean-based diet was used as the control and other treatment was fed the same basal diet containing 15% fresh FSM. The feeding trial lasted for 21 days. Bacterial community structure and diversity in the cecum and colon were assessed using pyrosequencing-based analysis. The results showed that the phylum level, Firmicutes, Bacteroidetes, Proteobacteria and Tenericutes were dominant in the cecum or colon. Gut Firmicutes increased, while Bacteroidetes and Proteobacteria decreased in the fresh FSM-fed piglets. At the genus level, the relative abundances of butyrate-producing bacteria, Lactobacillus and Prevotella were higher in both cecum and colon of fresh FSM fed piglets. Meanwhile, fresh FSM could promote the development of intestinal morphological and reduce the incidence of diarrhea. The results indicated that fresh FSM might change intestinal function by influencing intestinal microenvironment.

Co-immobilization of ß-agarase and α-agarase for degradation of agarose to prepare bioactive 3,6-anhydro-L-galactose.

Agarose from biomass can be used to synthesize the rare sugar 3,6-anhydro-L-galactose (L-AHG), and the new synthesis route and functional properties of L-AHG have always been the focus of research. Here we developed a novel method to co-immobilize Aga50D and BpGH117 onto streptavidin-coated magnetic nanoparticles and achieved the conversion of agarose to bioactive L-AHG in one pot. Results showed that enzymes were successfully immobilized on the carrier. The activity of co-immobilized enzymes was 2.5-fold higher than that of single immobilized enzymes. Compared with free enzymes, co-immobilized enzymes exhibited enhanced thermal stability. The co-immobilized enzymes retained 79.45 % relative activity at 40 °C for 3 h, while the free enzymes only possessed 21.40 % residual activity. After eight cycles, the co-immobilized enzymes still retained 73.47 % of the initial activity. After silica gel chromatography, the purity of L-AHG obtained by co-immobilized enzymes hydrolysis reached 83.02 %. Furthermore, bioactivity experiments demonstrated that L-AHG displayed better antioxidant and antibacterial effects than neoagarobiose. L-AHG had broad-spectrum antibacterial activity, while neoagarobiose and D-galactose did not show an obvious antibacterial effect. This study provides a feasible method for the production of L-AHG by a co-immobilized multi-enzyme system and confirms that L-AHG plays a key role in the bioactivity of neoagarobiose.

Comparative study on different immobilization sites of immobilized ß-agarase based on the biotin/streptavidin system.

ß-Agarase was biotinylated and immobilized onto streptavidin-conjugated magnetic nanoparticles to provide insights into the effect of immobilization sites on ß-agarase immobilization. Results showed that, compared with free enzyme, the stability of prepared immobilized ß-agarases through amino or carboxyl activation were both significantly improved. However, the amino-activated immobilized ß-agarase showed higher thermostability and catalytic efficiency than the carboxyl-activated immobilized ß-agarase. The relative activity of the former was 65.00 % after incubation at 50 °C for 1 h, which was 1.77-fold higher than that of the latter. Additionally, amino-activated immobilization increased the affinity of the enzyme to the substrate, and its maximum reaction rate (0.68 µmol/min) was superior to that of carboxyl-activated immobilization (0.53 µmol/min). The visualization results showed that the catalytic site of ß-agarase after carboxyl-activated immobilization was more susceptible to the immobilization process, and the orientation of the enzyme may also hinder substrate binding and product release. These results suggest that by pre-selecting appropriate activation sites and enzyme orientation, immobilized enzymes with higher catalytic activity and stability can be obtained, making them more suitable for the application of continuous production.

Engraftment of heavily transfused patients with severe aplastic anemia with a fludarabine-based regimen.

We have developed a practical conditioning regimen without anti-thymocyte globulin (ATG), irradiation, or other myeloablative alkylating agent for low-income countries in which patients with severe aplastic anemia (SAA), who usually have heavily transfused and a prolonged disease history. The application of ATG, Busulphan, and/or irradiation to cyclophosphamide (Cy) to avoid graft rejection has many short- and long-term complications. In this study, we focused on evaluating a fludarabine-based conditioning regimen, among 83 patients with SAA. Patients were treated with fludarabine (40 mg/m(2) /d; day [-5 to -2]) and cyclophosphamide (50 mg/kg/d; day [-5 to -2]). Altogether, 81 patients indicated initial engraftment, whereas two cases showed primary graft failure. And four of the 81 cases indicated graft rejection during follow-up. Regardless of a high cumulative incidence of acute (55/83; 66.2% grade II-IV; 47/83; 56.6% III-IV) and chronic graft-versus-host disease (50/83; 60.2%), in total, 77 patients showed durable engraftment and transfusion independence, and 64 are alive at a median time of 49 months with an overall survival rate of 66%. In conclusion, this conditioning indicated well toleration, mild toxicity, durable engraftment, excellent survival as well as less cost. Its application might shed new light on SAA at high risk of graft rejection in resource-limited countries.

Natural antimicrobial oligosaccharides in the food industry.

An increase in the number of antibiotic resistance genes burdens the environment and affects human health. Additionally, people have developed a cautious attitude toward chemical preservatives. This attitude has promoted the search for new natural antimicrobial substances. Oligosaccharides from various sources have been studied for their antimicrobial and prebiotic effects. Antimicrobial oligosaccharides have several advantages such as being produced from renewable resources and showing antimicrobial properties similar to those of chemical preservatives. Their excellent broad-spectrum antibacterial properties are primarily because of various synergistic effects, including destruction of pathogen cell wall. Additionally, the adhesion of harmful microorganisms and the role of harmful factors may be reduced by oligosaccharides. Some natural oligosaccharides were also shown to stimulate the growth probiotic organisms. Therefore, antimicrobial oligosaccharides have the potential to meet food processing industry requirements in the future. The latest progress in research on the antimicrobial activity of different oligosaccharides is demonstrated in this review. The possible mechanism of action of these antimicrobial oligosaccharides is summarized with respect to their direct and indirect effects. Finally, the extended applications of oligosaccharides from the food source industry to food processing are discussed.

Co-Cultures of Lactobacillus acidophilus and Bacillus subtilis Enhance Mucosal Barrier by Modulating Gut Microbiota-Derived Short-Chain Fatty Acids.

Weaning stress induces intestinal barrier dysfunction and immune dysregulation in mammals. Various interventions based on the modulation of intestinal microbiota have been proposed. Our study aims to explore the effects of co-cultures from Lactobacillus acidophilus and Bacillus subtilis (FAM®) on intestinal mucosal barrier from the perspective of metabolic function of gut microbiota. A total of 180 piglets were allocated to three groups, i.e., a control group (C, basal diet), a FAM group (F, basal diet supplemented with 0.1% FAM), and an antibiotic group (A, basal diet supplemented with antibiotic mixtures). Here, we showed FAM supplementation significantly increased body weight and reduced diarrhea incidence, accompanied by attenuated mucosal damage, increased levels of tight junction proteins, serum diamine oxidase (DAO) and antimicrobial peptides. In addition, 16S rRNA sequencing and metabolomic analysis revealed an increase in relative abundance of Clostridiales, Ruminococcaceae, Firmicutes and Muribaculaceae and a significant increase in the total short-chain fatty acids (SCFAs) and butyric acid in FAM-treated piglets. FAM also increased CD4+ T cells and SIgA+ cells in intestinal mucosa and SIgA production in colon contents. Furthermore, FAM upregulated the expression of IL-22, short-chain fatty acid receptors GPR43 and GPR41, aryl hydrocarbon receptor (AhR), and hypoxia-inducible factor 1α (HIF-1α). FAM shows great application prospect in gut health and provides a reference for infant weaning.

Non-Conventional Induction Heat Treatment: Effect of Design and Electrical Parameters on Apple Juice Safety and Quality.

The proposed non-conventional induction heating, which combines an MSCP and VDC structure, was proved to have excellent thermal effect. Different from other electric field sterilization, this electrotechnology operates with no electrodes, and it is a continuous-flow process with short-duration (about 20 s). In current study, the parameters related to temperature rise were investigated, including applied voltage, frequency, the diameter of the secondary coil and heating tube, as well as their length, etc. It was demonstrated that a smaller diameter of the heating tube, parallel connection sample coils, and higher frequency were beneficial for the inactivation of microorganisms. At 500 Hz, the optimal condition is 800 V, d1 = 2 mm, and L1 = 10 cm. Notably, the system could inactivate all microorganisms and maintained the physicochemical properties of apple juice at 40 kHz. It suggests that this structural design has the potential for industrial applications and the proposed induction heating can realize the rapid sterilization of liquid food without applying electrodes.

Design and optimizing gold nanoparticle-cDNA nanoprobes for aptamer-based lateral flow assay: Application to rapid detection of acetamiprid.

The aptamer-based lateral flow assay strips (Apt-LFAs) have shown promising application prospects in the detection of small molecules. The general principle of Apt-LFAs used for the detection of small molecules is based on the target-induced dissociation (TID) competitive binding among the aptamer, target and gold nanoparticle (AuNP)-complementary DNA (cDNA) nanoprobes. One of the most important components in this device is AuNP-cDNA nanoprobe, which has strong effect on the sensitivity and specificity of Apt-LFAs. In this report, we designed an AuNPs@polyA-cDNA nanoprobe, which consists of a poly adenine (polyA) anchor blocker, a partial complementary DNA fragment to aptamer strand (cDNAa) and complementary DNA fragment to control DNA strand (cDNAc), for rapid detection of acetamiprid. cDNAa of AuNPs@polyA-cDNA nanoprobe was carefully investigated in terms of the hybridization site and length with the aptamer. A specific cDNAa sequence containing key binding bases of acetamiprid aptamer was obtained and verified by molecular docking analysis. After systematic optimization, the Apt-LFA was able to detect a minimum concentration of 0.33 ng mL-1 acetamiprid. The Apt-LFA was successfully applied to detect spiked acetamiprid in tomato and rape samples with the recoveries ranged from 94 to 106%. Based on the strong versatility and verified molecular interaction mechanism, the design strategy could be extended to develop various Apt-LFAs for other small molecules.

Ethnicity-stratified analysis of the association between XRCC3 Thr241Met polymorphism and leukemia: an updated meta-analysis.

BACKGROUND: Presently, whether X-ray repair cross complementing group 3 (XRCC3) Thr241Met polymorphism is correlated to leukemia risk remains controversial. Because of this reason, the objective of current study is to explore whether XRCC3 Thr241Met polymorphism confers risk to leukemia. METHODS: Two independent authors systematically and comprehensively searched Pubmed, Embase, the Cochrane library, Google academic, China National Knowledge Infrastructure (CNKI). Search time is from database foundation to March 2021. RESULTS: Overall, significant associations between leukemia risk and XRCC3 Thr241Met polymorphism were found in Caucasian population by allele contrast (T vs. C: OR 1.20, 95% CI 1.02-1.40), homozygote comparison (TT vs. CC: OR 1.35, 95% CI 1.05-1.73), and recessive genetic model (TT vs. TC/CC: OR 1.31, 95% CI 1.04-1.64). CONCLUSIONS: The present meta-analysis suggests that the XRCC3 Thr241Met polymorphism may be a risk factor for leukemia in Caucasian population.

Maternal galactooligosaccharides supplementation programmed immune defense, microbial colonization and intestinal development in piglets.

The benefits of galactooligosaccharides (GOS) in neonates have been confirmed. However, the effects of nutritional programming by maternal GOS intervention on microbial colonization and intestinal development in the offspring remain unclear. In the present study, late gestational sows were fed with GOS (10 g d-1 added into the diet) or not until parturition, and the performances, immune status, microbiota composition and intestinal barriers in their piglets on day 21 were compared. GOS supplementation in pregnant sows improved their litter characteristics and the growth performance of their piglets during the neonatal stage (day 21), and elevated the plasma IgA levels in both sows and their piglets (P < 0.05). GOS intervention enriched fecal Alloprevotella and Ruminoclostridium_1 in gestational sows and vertically increased fecal Alloprevotella and Ruminococcaceae in their piglets (P < 0.05). Moreover, maternal GOS intervention increased fecal acetate (P < 0.05) and improved the intestinal barriers of their piglets by upregulating intestinal tight junctions (Occludin, Claudin-1, ZO-1), the goblet cell number and Mucin-2 (P < 0.05), which correlated positively with the colonized microbiota (P < 0.05). In summary, GOS supplementation for sows during late gestation nutritionally programmed maternal specific microbes and IgA of their offspring. This neonatal programming showed positive potential in promoting the intestinal barriers, immune defense, and growth performance of the piglets. Our findings provide evidence for maternal nutritional programming in neonates and insights for future application of GOS in maternal-neonatal nutrition.