Helicobacter pylori infection facilitates cell migration and potentially impact clinical outcomes in gastric cancer.

Gastric cancer is a significant health concern worldwide. Helicobacter pylori (HP) infection is associated with gastric cancer risk, but differences between HP-infected and HP-free gastric cancer have not been studied sufficiently. The objective of this study was to investigate the effects of HP infection on the viability and migration of gastric cancer cells and identify potential underlying genetic mechanisms as well as their clinical relevance. Cell counting kit-8, lactate dehydrogenase, wound healing, and transwell assay were applied in the infection model of multiple clones of HP and multiple gastric cancer cell lines. Genes related to HP infection were identified using bioinformatics analysis and subsequently validated using real-time quantitative PCR. The association of these genes with immunity and drug sensitivity of gastric cancer was analyzed. Results showed that HP has no significant impact on viability but increases the migration of gastric cancer cells. We identified 1405 HP-upregulated genes, with their enriched terms relating to cell migration, drug, and immunity. Among these genes, the 82 genes associated with survival showed a significant impact on gastric cancer in consensus clustering and LASSO prognostic model. The top 10 hub HP-associated genes were further identified, and 7 of them were validated in HP-infected cells using real-time quantitative PCR, including ERBB4, DNER, BRINP2, KCTD16, MAPK4, THPO, and VSTM2L. The overexpression experiment showed that KCTD16 medicated the effect of HP on gastric cancer migration. Our findings suggest that HP infection may enhance the migratory potential of gastric cancer cells and these genes might be associated with immunity and drug sensitivity of gastric cancer. In human subjects with gastric cancer, HP presence in tumors may affect migration, immunity, and drug sensitivity.

Phellodendron chinense C.K.Schneid: An in vitro study on its anti-Helicobacter pylori effect.

ETHNOPHARMACOLOGICAL RELEVANCE: Phellodendron chinense C.K.Schneid(P. chinense Schneid) is known in TCM as Huang Bo, is traditionally used to support gastrointestinal function and alleviate stomach-related ailments, including gastric ulcer bleeding and symptoms of gastroesophageal reflux disease. Helicobacter pylori (H. pylori) is classified by the WHO as a Group 1 carcinogen. However, the specific activity and mechanism of action of P. chinense Schneid against H. pylori infection remain unclear. It has been noted that Huangjiu processing may alter the bitter and cold properties of P. chinense Schneid, but its effect on antimicrobial activity requires further investigation. Additionally, it remains uncertain whether berberine is the sole antimicrobial active component of P. chinense Schneid. AIM OF STUDY: This study aims to elucidate the anti-H. pylori infection activity of P. chinense Schneid, along with its mechanism of action and key antimicrobial active components. MATERIALS AND METHODS: Phytochemical analysis was carried out by UPLC-MS/MS. HPLC was employed to quantify the berberine content of the extracts. Antimicrobial activity was assessed using the micro broth dilution method. Morphology was observed using SEM. The impact on urease activity was analyzed through in vitro urease enzyme kinetics. RT-qPCR was employed to detect the expression of virulence genes, including adhesin, flagellum, urease, and cytotoxin-related genes. The adhesion effect was evaluated by immunofluorescence staining and agar culture. RESULTS: P. chinense Schneid exhibited strong antimicrobial activity against both antibiotic-sensitive and resistant H. pylori strains, with MIC ranging from 40 to 160 µg/mL. Combination with amoxicillin, metronidazole, levofloxacin, and clarithromycin did not result in antagonistic effects. P. chinense Schneid induced alterations in bacterial morphology and structure, downregulated the expression of various virulence genes, and inhibited urease enzyme activity. In co-infection systems, P. chinense Schneid significantly attenuated H. pylori adhesion and urease relative content, thereby mitigating cellular damage caused by infection. Huangjiu processing enhanced the anti-H. pylori activity of P. chinense Schneid. Besides berberine, P. chinense Schneid contained seven other components with anti-H. pylori activity, with palmatine exhibiting the strongest activity, followed by jatrorrhizine. CONCLUSIONS: This study sheds light on the potential therapeutic mechanisms of P. chinense Schneid against H. pylori infection, demonstrating its capacity to disrupt bacterial structure, inhibit urease activity, suppress virulence gene transcription, inhibit adhesion, and protect host cells. The anti-H. pylori activity of P. chinense Schneid was potentiated by Huangjiu processing, and additional components beyond berberine were identified as possessing strong anti-H. pylori activity. Notably, jatrorrhizine, a core component of P. chinense Schneid, exhibited significant anti-H. pylori activity, marking a groundbreaking discovery.

In vitro anti-Helicobacter pylori activity and antivirulence activity of cetylpyridinium chloride.

The primary treatment method for eradicating Helicobacter pylori (H. pylori) infection involves the use of antibiotic-based therapies. Due to the growing antibiotic resistance of H. pylori, there has been a surge of interest in exploring alternative therapies. Cetylpyridinium chloride (CPC) is a water-soluble and nonvolatile quaternary ammonium compound with exceptional broad-spectrum antibacterial properties. To date, there is no documented or described specific antibacterial action of CPC against H. pylori. Therefore, this study aimed to explore the in vitro activity of CPC against H. pylori and its potential antibacterial mechanism. CPC exhibited significant in vitro activity against H. pylori, with MICs ranging from 0.16 to 0.62 µg/mL and MBCs ranging from 0.31 to 1.24 µg/mL. CPC could result in morphological and physiological modifications in H. pylori, leading to the suppression of virulence and adherence genes expression, including flaA, flaB, babB, alpA, alpB, ureE, and ureF, and inhibition of urease activity. CPC has demonstrated in vitro activity against H. pylori by inhibiting its growth, inducing damage to the bacterial structure, reducing virulence and adherence factors expression, and inhibiting urease activity.

In vitro anti-Helicobacter pylori activity and the underlining mechanism of an empirical herbal formula - Hezi Qingyou.

Background: Helicobacter pylori (H. pylori) is thought to primarily colonize the human stomach and lead to various gastrointestinal disorders, such as gastritis and gastric cancer. Currently, main eradication treatment is triple or quadruple therapy centered on antibiotics. Due to antibiotic resistance, the eradication rate of H. pylori is decreasing gradually. Therefore, searching for anti-H. pylori drugs from herbal sources has become a strategy for the treatment. Our team proposed a Hezi Qingyou Formula (HZQYF), composed of Chebulae Fructus, Ficus hirta Vahl and Cloves, and studied its anti-H. pylori activity and mechanism. Methods: Chemical components of HZQYF were studied using UHPLC-MS/MS and HPLC. Broth microdilution method and agar dilution method were used to evaluate HZQYF's antibacterial activity. The effects of HZQYF on expression of adhesion genes (alpA, alpB, babA), urease genes (ureE, ureF), and flagellar genes (flaA, flaB) were explored using Reverse Transcription-quantitative Polymerase Chain Reaction (RT-qPCR) technology. Effects on morphology and permeability of the extracellular membrane were studied using scanning electron microscopy (SEM) and N-phenylnaphthalen-1-amine (NPN) uptake. Effect on urease activity was studied using a urease kinetics analysis in vitro. Immunofluorescence staining method was used to examine the effect on adhesion. Western blot was used to examine the effect on cagA protein. Results: Minimum inhibitory concentration (MIC) values of the formula against H. pylori clinical strains and standard strains were 80-160 µg/mL, and minimum bactericidal concentration (MBC) values were 160-320 µg/mL. The formula could down-regulate the expression of adhesion genes (alpA, alpB, babA), urease genes (ureE, ureF) and flagellar genes (flaA, flaB), change the morphology of H. pylori, increase its extracellular membrane permeability, and decrease its urease activity. Conclusion: Present studies confirmed that HZQYF had promising in vitro anti-H. pylori activities and demonstrated its possible mechanism of action by down-regulating the bacterial adhesion, urease, and flagellar gene expression, which provided scientific bases for further clinical investigations.

1,3,6-Trigalloylglucose: A Novel Potent Anti-Helicobacter pylori Adhesion Agent Derived from Aqueous Extracts of Terminalia chebula Retz.

1,3,6-Trigalloylglucose is a natural compound that can be extracted from the aqueous extracts of ripe fruit of Terminalia chebula Retz, commonly known as "Haritaki". The potential anti-Helicobacter pylori (HP) activity of this compound has not been extensively studied or confirmed in scientific research. This compound was isolated using a semi-preparative liquid chromatography (LC) system and identified through Ultra-high-performance liquid chromatography-MS/MS (UPLC-MS/MS) and Nuclear Magnetic Resonance (NMR). Its role was evaluated using Minimum inhibitory concentration (MIC) assay and minimum bactericidal concentration (MBC) assay, scanning electron microscope (SEM), inhibiting kinetics curves, urea fast test, Cell Counting Kit-8 (CCK-8) assay, Western blot, and Griess Reagent System. Results showed that this compound effectively inhibits the growth of HP strain ATCC 700392, damages the HP structure, and suppresses the Cytotoxin-associated gene A (Cag A) protein, a crucial factor in HP infection. Importantly, it exhibits selective antimicrobial activity without impacting normal epithelial cells GES-1. In vitro studies have revealed that 1,3,6-Trigalloylglucose acts as an anti-adhesive agent, disrupting the adhesion of HP to host cells, a critical step in HP infection. These findings underscore the potential of 1,3,6-Trigalloylglucose as a targeted therapeutic agent against HP infections.

Magnetic Biochar Derived from Fenton Sludge/CMC for High-Efficiency Removal of Pb(II): Synthesis, Application, and Mechanism.

Magnetic biochar composites (MBC) were developed by a simple one-step pyrolysis method using Fenton sludge waste solid and carboxymethyl cellulose sodium. Detailed morphological, chemical, and magnetic characterizations corroborate the successful fabrication of MBC. Batch adsorption experiments show that the synthesized MBC owns high-efficiency removal of Pb(II), accompanied by ease-of-separation from aqueous solution using magnetic field. The experiment shows that the equilibrium adsorption capacity of MBC for Pb(II) can reach 199.9 mg g-1, corresponding to a removal rate of 99.9%, and the maximum adsorption capacity (qm) reaches 570.7 mg g-1, which is significantly better than that of the recently reported magnetic similar materials. The adsorption of Pb(II) by MBC complies with the pseudo second-order equation and Langmuir isotherm model, and the adsorption is a spontaneous, endothermic chemical process. Investigations on the adsorption mechanism show that the combination of Pb(II) with the oxygen-containing functional groups (carboxyl, hydroxyl, etc.) on biochar with a higher specific surface area are the decisive factors. The merits of reusing solid waste resource, namely excellent selectivity, easy separation, and simple preparation make the MBC a promising candidate of Pb(II) purifier.

A Rapid and Visual Method for Nucleic Acid Detection of Escherichia coli O157:H7 Based on CRISPR/Cas12a-PMNT.

Rapid, accurate and visual point-of-care testing (POCT) methods for pathogenic bacteria detection are essential for avoiding foodborne diseases caused by pathogens or their toxins. In this study, we proposed a rapid and visual detection method that we named "Cas12aVIP". By combining recombinase polymerase amplification (RPA), a CRISPR/Cas12a system and a cationic-conjugated polythiophene derivative (poly[3-(3'-N,N,N-triethylamino-1'-propyloxy)-4-methyl-2,5-thiophene hydrochloride] (PMNT) mixed with single-stranded DNA (ssDNA)), the solution turned red in the absence of the target DNA based on conformational modifications of the conjugated backbone of PMNT, whereas it displayed yellow, thus realizing the colorimetric detection of DNA. The Cas12aVIP method yielded high specificity and no interference from other nontargeted bacteria. The detection was accomplished in 40 min and the signal could be observed by the naked eye under natural light, presenting great potential for a variety of rapid nucleic acid detection applications without requiring technical expertise or ancillary equipment.

Detection and Quantification of Adulterated Beef and Mutton Products by Multiplex Droplet Digital PCR.

In order to seek high profit, businesses mix beef and mutton with cheap meat, such as duck, pork, and chicken. Five pairs of primers were designed for quintuple droplet digital PCR (qddPCR) of specific genomic regions from five selected species and specificity and amplification efficiency were determined. The mixed DNA template with an equal copy number was used for detecting the accuracy and limit of multiplex PCR. The results showed that the primers and probes of the five selected species had good specificity with the minimum number of detection copies: 0.15 copies/µL beef (Bos taurus), 0.28 copies/µL duck (Anas platyrhynchos), 0.37 copies/µL pork (Sus scrofa), 0.39 copies/µL chicken (Gallus gallus), and 0.41 copies/µL mutton (Ovis aries), respectively. The five sets of primers and probes could quickly judge whether the specified meat components existed in the food commodities.

Screening of Antifungal Lactic Acid Bacteria as Bioprotective Cultures in Yogurt and a Whey Beverage.

ABSTRACT: The demand for preservative-free food products is rising, and biopreservation is a potential alternative to replace or reduce the use of chemical preservatives. The objectives of this study were to assess the antifungal activity of lactic acid bacteria (LAB; n = 98) and the efficacy and applicability of the chosen bioprotective cultures against fungal spoilers in dairy products. First, 14 antifungal strains were preliminarily screened by in vitro tests against Pichia pastoris D3, Aspergillus niger D1, Geotrichum candidum N1, Kluyveromyces marxianus W1, and Penicillium chrysogenum B1 and validated by challenge tests in yogurt, indicating that the fungal-inhibiting activity of LAB was species specific and yogurt fermented with antifungal LAB cultures was more effective in extending shelf life. Second, the chosen 14 LAB strains were identified by the 16S rDNA sequence analysis and carbohydrate fermentation test. The results were as follows: nine strains were Lactobacillus plantarum, three were Lactobacillus paracasei, one was Enterococus faecium, and one was Lactobacillus rhamnosus. Among them, active L. plantarum N7 was the chosen and studied factor affecting antifungal activity by using the response surface methodology. Finally, in situ tests were conducted to validate the activity of L. plantarum N7 in actual dairy products (whey beverages). Physicochemical and microbial indices of whey beverages during storage indicated that antifungal L. plantarum N7 could slow yeast growth and be candidates of interest for industrial applications.

Development of a lateral flow test strip for simultaneous detection of BT-Cry1Ab, BT-Cry1Ac and CP4 EPSPS proteins in genetically modified crops.

A colloidal gold immunochromatographic strip (ICS) for simultaneous detection of multiple transgenic proteins, including CP4 EPSPS, BT-Cry1Ab and BT-Cry1Ac, was developed in this study. The sensitivity of the strip to the target protein was 5 ng/mL for CP4 EPSPS, 100 ng/mL for BT-Cry1Ab and Cry1Ac, respectively. Parallel analysis for maize, soybean, sugar beet and cotton showed the strip could detect 1% of transgenic content in crops containing BT-Cry1Ab and Cry1Ac, and, at least, 0.1% of content in crops containing CP4 EPSPS. The detection results for seed samples indicated the multicomponent analysis ICS had good accuracy. The analysis could be completed within 10 min and had the advantages of being high-throughput, easy to operate and visual detection. This is the first report of semi-quantitative ICS for detecting three transgenic proteins simultaneously. The developed approach may provide insights into the development of ICS for analyzing simultaneously multiple components in genetically modified crops.

Mitigation of Cd accumulation in rice with water management and calcium-magnesium phosphate fertilizer in field environment.

Pollution of Cd has seriously threatened environmental safety and human health. The field experiment was conducted to investigate the effects of calcium-magnesium phosphate fertilizer and water management on bioavailability of Cd in soils and its accumulation in rice. The results revealed that continuous flooding has enhanced soil pH from 5.10 to 5.72 and reduced soil redox potential (Eh) from 164 to - 60 mV. Application of calcium-magnesium phosphate fertilizer has significantly raised soil pH from 5.10 to 6.45 (P < 0.05). The treatment of calcium-magnesium phosphate fertilizer and continuous flooding has reduced available content of Cd in soils by 28.57%. The content of Cd in brown rice was significantly diminished by 51.36% (P < 0.05). The continuous flooding has promoted formation of residual Cd in soil with application of calcium-magnesium phosphate fertilizer. The biomass and grain production of rice was not significantly decreased compared with control.

Standard Reference Line Combined with One-Point Calibration-Free Laser-Induced Breakdown Spectroscopy (CF-LIBS) to Quantitatively Analyze Stainless and Heat Resistant Steel.

Due to the influence of self-absorption of major elements, scarce observable spectral lines of trace elements, and relative efficiency correction of experimental system, accurate quantitative analysis with calibration-free laser-induced breakdown spectroscopy (CF-LIBS) is in fact not easy. In order to overcome these difficulties, standard reference line (SRL) combined with one-point calibration (OPC) is used to analyze six elements in three stainless-steel and five heat-resistant steel samples. The Stark broadening and Saha-Boltzmann plot of Fe are used to calculate the electron density and the plasma temperature, respectively. In the present work, we tested the original SRL method, the SRL with the OPC method, and intercept with the OPC method. The final calculation results show that the latter two methods can effectively improve the overall accuracy of quantitative analysis and the detection limits of trace elements.

Calibration-Free Laser-Induced Breakdown Spectroscopy (CF-LIBS) with Standard Reference Line for the Analysis of Stainless Steel.

In this work, calibration-free laser-induced breakdown spectroscopy (CF-LIBS) is used to analyze a certified stainless steel sample. Due to self-absorption of the spectral lines from the major element Fe and the sparse lines of trace elements, it is usually not easy to construct the Boltzmann plots of all species. A standard reference line method is proposed here to solve this difficulty under the assumption of local thermodynamic equilibrium so that the same temperature value for all elements present into the plasma can be considered. Based on the concentration and rich spectral lines of Fe, the Stark broadening of Fe(I) 381.584 nm and Saha-Boltzmann plots of this element are used to calculate the electron density and the plasma temperature, respectively. In order to determine the plasma temperature accurately, which is seriously affected by self-absorption, a pre-selection procedure for eliminating those spectral lines with strong self-absorption is employed. Then, one spectral line of each element is selected to calculate its corresponding concentration. The results from the standard reference lines with and without self-absorption of Fe are compared. This method allows us to measure trace element content and effectively avoid the adverse effects due to self-absorption.

Self-assemblies of 5'-cholesteryl-ethyl-phosphoryl zidovudine.

Anti-HIV prodrugs are recently focused on due to their ability of self-assembly, macrophage targeting, and enhanced antiviral effects. Here, an amphiphilic prodrug of zidovudine, an anti-HIV nucleoside analogue, 5'-cholesteryl-ethyl-phosphoryl zidovudine (CEPZ) was synthesized. CEPZ showed some unique physicochemical properties. The solubility of CEPZ in the noncompetitive solvents chloroform and tetrahydrofuran (THF) was very high based on the hydrogen bonds between zidovudine groups, though CEPZ was sparing soluble in alcohols and almost insoluble in water. The typical amphiphilic property of CEPZ was demonstrated according to the Langmuir monolayers at the air/water interface. The LogP of CEPZ was high to 13.78, indicating the high hydrophobicity of amphiphilic CEPZ similar to phospholipids. Homogenous and stable self-assemblies were formed with the mean size of 128.7nm and the zeta potential of -35.4mV after injecting the CEPZ-in-THF solution into water. Hydrophobic interaction between the cholesteryl moieties of CEPZ could drive molecular self-assembly and lead to the formation of spherical vesicles. CEPZ self-assemblies showed strong stability even under high temperature and gravity probably due to the high surface charge. CEPZ was very slowly degraded in neutral solutions (e.g., pH 7.4), but fast in acid solutions (e.g., pH 5.0) and some tissue homogenates. CEPZ was quickly eliminated from the circulation and distributed into the mononuclear phagocyte system (MPS) including the liver, spleen and lung after bolus intravenous administration of CEPZ self-assemblies to mice. The MPS targeting effect of CEPZ self-assemblies makes them become a promising self-assembled drug delivery system to eradicate the HIV hidden in the macrophages.

Self-assembled drug delivery systems. Part 7: hepatocyte-targeted nanoassemblies of an adefovir lipid derivative with cytochrome P450-triggered drug release.

A novel strategy was used in the design of self-assembled drug delivery systems (SADDSs) in this study. The nanoassemblies of an amphiphilic adefovir lipid derivative were prepared and demonstrated to have the functions of hepatocyte targeting, enzyme-triggered drug release and high anti-hepatitis effect. An amphiphilic adefovir lipid derivative, N-lauroyl-1-(3-chlorophenyl)-1,3-propanyl phosphonyl adefovir (LCPA) was prepared and formed the nanoassemblies by injecting the mixture of LCPA and another amphiphilic polymer, d-galactide polyoxyethylene (20) cetyl ether (GPCE) (ca. 20:1, mol/mol) into water. The nanoassemblies were very stable and showed negative charge. LCPA was sensitive to the cytochrome P450 isozymes that were expressed predominantly in the hepatocytes to produce adefovir. GPCE contained a long hydrophilic chain and a galactose ligand targeting the asialoglycoprotein receptors overexpressed on the surface of hepatocytes. The nanoassemblies showed the long-circulating and liver targeting effects according to the results of pharmacokinetics, tissue distribution and fluorescence imagination after bolus intravenous administration of the nanoassemblies to the mice. The highly efficient hepatitis B treatment was achieved by 10 day continuous administration of the nanoassemblies to the HBV-infected mice. Many functions were combined in the nanoassemblies, including prodrug, molecular self-assembly, nanotechnology, long-circulating, hepatocyte targeting and hepatocyte over expressing enzyme-triggered drug release.

Identification and quantification of genetically modified Moonshade carnation lines using conventional and TaqMan real-time polymerase chain reaction methods.

Genetically modified carnation (Dianthus caryophyllus L.) Moonshade was approved for planting and commercialization in several countries from 2004. Developing methods for analyzing Moonshade is necessary for implementing genetically modified organism labeling regulations. In this study, the 5'-transgene integration sequence was isolated using thermal asymmetric interlaced (TAIL)-PCR. Based upon the 5'-transgene integration sequence, conventional and TaqMan real-time PCR assays were established. The relative limit of detection for the conventional PCR assay was 0.05 % for Moonshade using 100 ng total carnation genomic DNA, corresponding to approximately 79 copies of the carnation haploid genome, and the limits of detection and quantification of the TaqMan real-time PCR assay were estimated to be 51 and 254 copies of haploid carnation genomic DNA, respectively. These results are useful for identifying and quantifying Moonshade and its derivatives.

A multifunctional in situ-forming hydrogel for wound healing.

In this study, a multifunctional in situ-forming hydrogel (MISG) was prepared as a wound dressing designed to stop bleeding, inhibit inflammation, relieve pain, and improve healing. A mixture of poloxamers 407 and 188 was used for the matrix of the MISG. Other ingredients include aminocaproic acid (to stop bleeding), povidone iodine (anti-infective), lidocaine (pain relief), and chitosan (to enhance wound healing and regeneration). The incipient gelation temperature of the MISG was modified by varying the poloxamer concentration. Poloxamer cytotoxicity was evaluated in addition to the effect of the MISG on hemostasis in rabbits, pain relief in mice, bacteriostasis in vitro, and wound healing. The optimal MISG matrix consisted of 30% (w/v) poloxamer (407/188, 1 : 1, w/w) solution and was able to change to a gel within 10 minutes at 37 °C. The poloxamer solution had no cytotoxicity in fibroblasts. Compared to sterile gauze alone, the MISG significantly shortened average hemostasis time and decreased bleeding. The hydrogel showed strong bacteriostatic action similar to povidone iodine solution. It markedly increased the pain threshold and accelerated wound healing compared to the gauze. The MISG is a promising formulation for wound healing in emergency situations.

Validation of a carnation-specific gene, ANS, used as an endogenous reference gene in qualitative and real-time quantitative PCR for carnations.

The validation of the anthocyanin synthase (ANS) gene as a carnation endogenous reference gene applicable both in classical and real-time PCR methods is a prerequisite for the development of PCR assays for genetically modified (GM) carnation detection. This is important due to the fact that GM carnation lines, developed by Florigene Pty Ltd, have been approved for commercialization. In this study, both methods were tested on 14 different carnation cultivars, and identical amplification products were obtained with all of them. No amplification products were observed with samples from 14 other plant species, which demonstrated that the system was specific to carnation. The results of Southern blot analysis confirmed that the ANS gene had a low copy number in the 10 tested carnation varieties. In qualitative and real-time PCR assays, the LOD values of 0.05 and 0.005 ng carnation DNA, respectively, were validated. Moreover, the real-time PCR system was validated with high PCR efficiency and linearity. Thus, the ANS gene had species specificity, low heterogeneity, and low copy number among the tested cultivars. These results provide evidence that the gene can be used as an endogenous reference gene of carnation, as well as in qualitative and quantitative PCR systems.

High sensitive detection of Cry1Ab protein using a quantum dot-based fluorescence-linked immunosorbent assay.

Protein-based detection methods, enzyme-linked immunosorbent assay (ELISA) and lateral flow strip, have been widely used for rapid, spot, and sensitive detection of genetically modified organisms (GMOs). Herein, one novel quantum dot-based fluorescence-linked immunosorbent assay (QD-FLISA) was developed employing quantum dots (QDs) as the fluorescent marker for the detection of the Cry1Ab protein in MON810 maize. The end-point fluorescent detection system was carried out using QDs conjugated with goat anti-rabbit secondary antibody. The newly developed Cry1Ab QD-FLISA assay was highly specific to the Cry1Ab protein and had no cross-reactivity with other target proteins, such as Cry2Ab, Cry1F, and Cry3Bb. The quantified linearity was achieved in the value range of 0.05-5% (w/w). The limits of detection (LOD) and quantification (LOQ) of the QD-FLISA were 2.956 and 9.854 pg/mL, respectively, which were more sensitive than the conventional sandwich ELISA method. All of the results indicated that QD-FLISA was a highly specific and sensitive method for the monitoring of Cry1Ab in GMOs.

Expression and purification of the synthetic preS1 gene of Hepatitis B Virus with preferred Escherichia coli codon preference.

To produce high levels of hepatitis B virus (HBV) preS1 protein at low cost, a DNA fragment encoding the preS1 region, residues 1-119, of HBV adr subtype was synthesized by overlapping-PCR according to Escherichia coli (E. coli) B preferred codon usage. The synthetic preS1 gene (spreS1) was cloned into the bacterial expression vector pET-30a and transferred into the expression strain E. coli BL21(DE3). Recombinant preS1 protein with an N-terminal His6 tag was expressed at high levels in soluble form, yielding about 44% of the total cellular protein. This technique overcomes problems that existed in previously reported expression systems of preS1 or its epitope, i.e., low-level expression or expression in inclusion bodies. Using this His-tagged preS1 expression system, recombinant protein was purified by single-step affinity chromatography on a Ni-NTA column resulting in a yield was about 28 mg recombinant protein per liter culture. Furthermore, Western blotting and indirect ELISA analysis demonstrate that the reactivity of preS1-specific antibody is comparable between the recombinant and commercialized preS1 protein. Thus, our improved expression system could be used for practical, low-cost large-scale production of recombinant preS1 without refolding steps.