Ce3+-Doped Li2Ca5Gd(BO3)5 Phosphors with Multiple Luminescent Centers and High Pressure Sensitivity under Near UV Excitation.

The performance of Ce3+-based phosphors under mechanical high pressures becomes attractive due to the potential application as a visual pressure sensor. Li2Ca5Gd(BO3)5 was selected as the host for the Ce3+ doping. Rietveld refinements reveal that rare earth cations occupy M1, M2, and M3 sites, and indeed, the photoluminescent spectra of Li2Ca5Gd1-xCex(BO3)5 (0.005 ≤ x ≤ 0.15) exhibit the characteristic of multiple activators, defined as CeI, CeII, and CeIII, with the maximal emission wavelength at ∼444, 419, and 378 nm, respectively. The optimal internal and external quantum efficiencies are 86.29% for x = 0.005 and 20.26% for x = 0.10, respectively, under the NUV excitation at 363 nm. In-situ high pressure emission spectra under 375 nm excitation exhibit an overall red-shift, and the linear pressure susceptibilities up to 6.7 GPa for CeI and CeII centers are -390 and -279 cm-1/GPa, respectively, which is probably the largest among Ce3+-doped oxides and oxysalts. Due to the above superiorities, Ce3+-doped LCGB possesses a high potential as a visual pressure sensor, and this is a successful study on the structure-property relationship of inorganic materials.

A 3D bioprinted nano-laponite hydrogel construct promotes osteogenesis by activating PI3K/AKT signaling pathway.

Development of nano-laponite as bioinks based on cell-loaded hydrogels has recently attracted significant attention for promoting bone defect repairs and regeneration. However, the underlying mechanisms of the positive function of laponite in hydrogel was not fully explored. In this study, the effect of 3D bioprinted nano-laponite hydrogel construct on bone regeneration and the potential mechanism was explored in vitro and in vivo. In vitro analyses showed that the 3D construct protected encapsulated cells from shear stresses during bioprinting, promoted cell growth and cell spreading, and BMSCs at a density of 107/mL exhibited an optimal osteogenesis potential. Osteogenic differentiation and ectopic bone formation of BMSCs encapsulated inside the 3D construct were explored by determination of calcium deposition and x-ray, micro-CT analysis, respectively. RNA sequencing revealed that activation of PI3K/AKT signaling pathway of BMSCs inside the laponite hydrogel significantly upregulated expression of osteogenic related proteins. Expression of osteogenic proteins was significantly downregulated when the PI3K/AKT pathway was inhibited. The 3D bioprinted nano-laponite hydrogel construct exhibited a superior ability for bone regeneration in rat bones with defects compared with groups without laponite as shown by micro-CT and histological examination, while the osteogenesis activity was weakened by applications of a PI3K inhibitor. In summary, the 3D bioprinted nano-laponite hydrogel construct promoted bone osteogenesis by promoting cell proliferation, differentiation through activation of the PI3K/AKT signaling pathway.

Purification and identification of globulin-1 S allele as a novel allergen with N-glycans in wheat (Triticum aestivum).

Wheat (Triticum aestivum) contains various allergenic proteins and induces diverse allergic reactions. Although many allergens are found to be glycoproteins, research on glycosylated allergens in wheat is rare. In this study, the main glycoprotein in wheat soluble protein was purified by sequential multi-column chromatography including affinity chromatography, gel filtration chromatography, and ion-exchange chromatography. The purified proteins were identified as globulin-1 S allele by liquid chromatography-tandem mass spectrometry and characterized by circular dichroism spectra. The strong IgE-binding capacity of the purified fractions was further demonstrated, suggesting globulin-1 S allele to be a novel allergen in wheat. Further de-N-glycosylated treatment by N-Glycosidase F showed that N-glycosylation enhanced the IgE-binding of globulin-1 S allele. These results identified globulin-1 S allele as a novel allergen in wheat, demonstrated the role of glycosylation in IgE-binding, and provided new insights into the prevention and treatment of wheat allergy.

Determination of Tropomyosin in Shrimp and Crab by Liquid Chromatography-Tandem Mass Spectrometry Based on Immunoaffinity Purification.

A UPLC-MS/MS method was developed for the detection of tropomyosin (TM) in shrimp and crab. After simple extraction, the samples were purified by immunoaffinity column and then digested by trypsin. The obtained sample was separated by Easy-nLC 1000-Q Exactive. The obtained spectrums were analyzed by Thermo Proteome Discoverer 1.4 software and then ANIQLVEK with high sensitivity was selected as the quantitative signature peptide. Isotope-labeled internal standard was used in the quantitative analysis. The method showed good linearity in the range of 5-5,000 µg/L with a limit of quantification (LOQ) of 0.1 mg/kg. The average recoveries were 77.22-95.66% with RSDs ≤ 9.97%, and the matrix effects were between 88.53 and 112.60%. This method could be used for rapid screening and quantitative analysis of TM in shrimp and crab. Thus, it could provide technical support for self-testing of TM by food manufacturers and promote further improvement of allergen labeling in China.

High-Throughput Identification of Allergens in a Food System via Hybridization Probe Cluster-Targeted Next-Generation Sequencing.

Food allergies (FAs) are a crucial public health problem and a severe food safety issue, resulting in an urgent need for an accurate method to detect all of the hidden allergens that exist in food systems. Current methods for detecting allergens typically utilize ELISA, PCR, or LC-MS, which are suitable for the confirmatory analysis of allergens from ingredients rather than unintended contaminants. In this study, we demonstrate a hybridization probe cluster-targeted next-generation sequencing (HPC-NGS) platform for high-throughput screening of potential allergens in food systems. The HPC-NGS successfully captured target DNA fragments and identified 19 allergenic ingredients in a complex food system. Additionally, the HPC-NGS provided expected allergenic species matching rates of 94.24-100% in single food materials and 99.87-99.98% in processed food products. Thus, HPC-NGS enables the accurate characterization of allergenic ingredients and unintended allergenic contaminants in foods. Our results provide new perspectives on the use of HPC-NGS in the accuracy of high-throughput detection technologies for allergens imposed by the complex matrix effect.

Allergenicity assessment and allergen profile analysis of different Chinese wheat cultivars.

BACKGROUNDS: As one of the most important cereals, wheat (Triticum aestivum) can cause severe allergic reactions, such as baker's asthma, allergic rhinitis, and atopic dermatitis. A growing number of people are developing allergies to Chinese wheat; however, only a few wheat cultivars have been screened on allergenicity in China. OBJECTIVE: The aim of the present study was to assess the allergenicity of different Chinese wheat cultivars and characterize wheat allergen profiles of patients with allergic rhinitis. METHODS: We determined protein (soluble protein, gliadin, and glutenin) composition in Chinese wheat by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and the immunoglobulin E (IgE) binding capacity by enzyme-linked immunosorbent assay (ELISA) and Western blot using 10 positive sera from wheat allergy patients. We identified 5 gel bands with significant IgE binding capacity using liquid chromatography-tandem mass spectrometry (LC-MS/MS). RESULTS: Soluble protein, albumin, and globulin, showed the highest allergenicity, followed by gliadin, while glutenin only had slight allergenicity. In soluble protein, 5 protein bands with molecular weights of 27, 28, 53, 58, and 62 kDa showed very significant allergenicity. Meanwhile, the relative abundances of 28 kDa-protein and 58 kDa-protein were significantly positively correlated with the IgE-binding capacity of Chinese wheat cultivars, which were identified as rRNA N-glycosidase and ß-amylase, respectively, among other proteins in those highly complex gel bands. CONCLUSION AND CLINICAL RELEVANCE: 28 kDa-protein (rRNA N-glycosidase) and 58 kDa-protein (ß-amylase) were speculated to be the main allergens of Chinese wheat causing baker's asthma and allergic rhinitis. These results provide new insights into the prevention and treatment of wheat allergy and the development of hypoallergenic wheat products, whose clinical significance is worth further evaluation.

Effects of deglycosylation and the Maillard reaction on conformation and allergenicity of the egg ovomucoid.

Ovomucoid (OVM), known as the major allergen in egg white, has gained increasing concerns in industrialized countries. Here, we found the deglycosylation and Maillard reaction with galactooligosaccharide (GOS) and fructooligosaccharide (FOS) can induce conformational transformation of OVM from other structures (ß-turn, strang, and random coils) to α-helix. We also introduced an approach to reduce the allergenicity of Gallus domesticus OVM by Maillard reaction with GOS and FOS. However, the OVM glycated by mannosan (MOS) and deglycosylated OVM exhibited higher allergenicity than native OVM. Therefore, GOS and FOS, especially GOS, could be applied in the reduction of the potential allergenicity of OVM through glycation. Furthermore, these findings may provide new insights into the development of hypoallergenic egg products. PRACTICAL APPLICATION: In this study, the allergenicity and conformation of OVM treated with deglycosylation and glycation (GOS, FOS, and MOS) were investigated. The results would provide a better understanding of the effects of deglycosylation and Maillard reaction with different reducing sugars on the molecular characteristics of OVM and further provide new insights into the development of hypoallergenic egg products.

A sensitive immunosensor based on FRET between gold nanoparticles and InP/ZnS quantum dots for arginine kinase detection.

Arginine kinase (AK) is one of the most important allergens in shrimp products. Herein, a novel immunoassay for quantitation of AK was developed using the antibody modified gold nanoparticle (AuNP) and quantum dot (QD). When the first antibody modified AuNP (AuNP-Ab1) was bridged by AK with the secondary antibody modified QD (QD-Ab2), fluorescence resonance energy transfer (FRET) would occur between the AuNP and QD, which led to a decrease in fluorescent signals. The decrease in fluorescence intensity was found to correlate linearly with the log of AK concentration in the range of 1.0 × 10-6-1.0 × 10-3 mg/mL (R2 = 0.9909) and the detection limit was 0.11 ng/mL. The immunoassay was further proved to have encouraging specificity, precision and accuracy. Compared with existing methods, this study provided a promising approach to develop a highly sensitive and selective detection method for AK in shrimp related food samples.

Unveiling specific nanoparticle-protein interactions via evaporated drops: From molecular recognition to allergen identification.

Unveiling specific interactions between nanoparticles (NPs) and proteins could benefit a better control of NPs' performance in recognition-based detection, imaging and drug delivery. Herein, we investigated the specific recognition between an aptamer modified gold nanoparticle (Apt-AuNP) and its target protein arginine kinase (AK) through a coffee-ring effect (CRE)-based approach. The evaporated droplets of the Apt-AuNP with AK featured a ring-disk-ring transition with elevated AK concentration and a disk pattern was found when the Apt was saturated by AK. Moreover, the AK concentration versus ring thickness curve below the saturation point was proved to fit in an exponential function, indicating the strong association between the Apt-AuNP and AK. In contrast, the ring thickness above the saturation point fitted in a Gompertz growth model that was similar with the Apt-AuNPs incubated with the nonspecific protein (bovine serum albumin, BSA), suggesting that AK was nonspecifically adsorbed onto the AuNPs. The impact of the specific NP-protein interaction on the translation of CRE into macroscopic patterns was further utilized to identify target food allergen AK by the Apt-AuNPs over nontarget allergens (tropomyosin, ovalbumin and ß-lactoglobulin). This work provided new insight into the general NP-protein association process and demonstrated the feasibility of employing CRE as an effective tool to profile the specific interactions between NPs and proteins.

Fluorescence-based quantitative platform for ultrasensitive food allergen detection: From immunoassays to DNA sensors.

Food allergies are global health issue with an increasing prevalence that affect food safety; hence, food allergen detection, labeling, and management are considered to be important priorities in the food industry. In this critical review, we provide a comprehensive overview of several fluorescence-based platforms based on different biorecognition ligands, such as antibodies, DNA, aptamers, and cells, for food allergen quantification. Traditional analytical methods are generally unsuitable for food manufacturers to accomplish the real-time identification of food allergens in food products. Therefore, it is important to develop simple, rapid, inexpensive, accurate, and sensitive methods to improve user accessibility. A fluorescence-based quantitative platform provides an excellent detection platform for food allergens because of its high sensitivity. This review summarizes the traditional antibody-based fluorescent techniques for food allergen detection, such as the time-resolved fluoroimmunoassay , immunofluorescence imaging, fluorescence enzyme-linked immune sorbent assay, flow injection fluoroimmunoassay, and fluorescence immunosensors. However, these methods suffer from disadvantages such as the significant rate of false-positive and false-negative results due to antibody cross-reactivity with nontarget food components in the complex food matrix and epitope degradation during food processing. Hence, different types of fluorescence-based immunoassays are suitable for standardization and quantification of allergens in fresh foods. In addition, we summarize new fluorescence-based quantitative platforms, including fluorescence genosensors, fluorescence cell sensors, and fluorescence aptamer sensors. With the advantages of high sensitivity and simple operation, fluorescence biosensors will have great potential in the future and could provide portable methods for multiallergen real-time detection in complex food systems.

Phenotypic characterization of Slc26a2 mutant mice reveals a multifactorial etiology of spondylolysis.

Confusion persists over pathogenesis of spondylolysis. To confirm pathogenicity of the previously identified causative mutation of spondylolysis and investigate the genetic etiology, we generate a new mouse line harboring D673V mutation in the Slc26a2 gene. D673V mutation induces delayed endochondral ossification characterized by transiently reduced chondrocyte proliferation in mice at the early postnatal stage. Adult D673V homozygotes exhibit dysplastic isthmus and reduced bone volume of the dorsal vertebra resembling the detached vertebral bony structure when spondylolysis occurs, including the postzygopophysis, vertebral arch, and spinous process, which causes biomechanical alterations around the isthmic region of L4-5 vertebrae indicated by finite element analysis. Consistently, partial ablation of Slc26a2 in vertebral skeletal cells using Col1a1-Cre; Slc26a2 fl/fl mouse line recapitulates a similar but worsened vertebral phenotype featured by lamellar isthmus. In addition, when reaching late adulthood, D673V homozygotes develop an evident bone-loss phenotype and show impaired osteogenesis. These findings support a multifactorial etiology, involving congenitally predisposed isthmic conditions, altered biomechanics, and age-dependent bone loss, which leads to SLC26A2-related spondylolysis.

Surface plasmon resonance (SPR) biosensors for food allergen detection in food matrices.

Food allergies are recognized as a growing public health concern, with an estimated 3% of adults and 6-8% of children affected by food allergy disorders. Hence, food allergen detection, labeling, and management have become significant priorities within the food industry, and there is an urgent requirement for reliable, sensitive, and user-friendly technologies to trace food allergens in food products. In this critical review, we provide a comprehensive overview of the principles and applications of surface plasmon resonance (SPR) biosensors in the identification and quantification of food allergens (milk, egg, peanut, and seafood), including fiber-optic surface plasmon resonance (FOSPR), surface plasmon resonance imaging (SPRI), localized surface plasmon resonance (LSPR), and transmission surface plasmon resonance (TSPR). Moreover, the characteristics and fitness-for-purpose of each reviewed SPR biosensor is discussed, and the potential of newly developed SPR biosensors for multi-allergen real-time detection in a complex food system is highlighted. Such SPR biosensors are also required to facilitate the reliable, high-throughput, and real-time detection of food allergens by the food control industry and food safety control officials to easily monitor cross-contamination during food processing.

[All-ceramic premolar guiding plate retains resin-bonded fixed partial dentures].

OBJECTIVE: This study aims to investigate the fracture resistance and short-term restorative effects of resin-bonded fixed partial dentures (RBFPDs) made from heat-pressed lithium-disilicate-based glass-ceramic (IPS e.max press) and zirconia ceramic (WIELAND) and retained by all-ceramic guiding plates when used to restore missing mandibular second premolars. METHODS: A total of 64 human mandibular first premolars and first molars were prepared as abutments, then were randomly divided into 4 groups (n=8): E0, heat-pressed ceramic RBFPDs, no cyclic loading; E1, heat-pressed ceramic RBFPDs exposed to 300 000 cycles of dynamic loading; W0, zirconia ceramic RBFPDs, no cyclic loading; and W1, zirconia ceramic RBFPDs exposed to 300 000 cycles of dynamic loading. Fracture strength was tested in a universal testing machine. RESULTS: The medians of fracture strength were 1 242.85 N±260.11 N (E0), 1 650.85 N±206.77 N (W0), 1 062.60 N±179.98 N (E1), and 1 167.61 N±265.50 N (W1). Statistical analysis showed that all the groups exhibited significantly higher fracture strength compared with the maximum bite force in the premolar region (360 N; P<0.001). The W0 group had significantly higher fracture strength than the E0 group (P<0.05). Meanwhile, no significant difference in fracture strength was observed between the E1 and W1 groups (P>0.05). Significant statistical differences were found between the zirconia ceramic groups (W0 and W1, P<0.05) but not between the glassceramic groups (E0 and E1, P>0.05) after dynamic loading. CONCLUSIONS: The RBFPDs retained by all-ceramic guiding plates exhibited promising fracture properties and optimal short-term restorative effects when used to restore missing mandibular second premolars.

A chiral assembly of gold nanoparticle trimer-based biosensors for ultrasensitive detection of the major allergen tropomyosin in shellfish.

A biosensor based on a chiral assembly of polymer of gold nanoparticle (AuNP) trimers was developed for the detection and quantification of the major shellfish allergen tropomyosin (TROP). TROP and anti-TROP monoclonal antibodies (mAb) were immobilized on 20 nm and 30 nm 16-mercaptohexadecanoic acid (16-MHDA) functionalized AuNPs to assemble a trimer, which has a Circular dichroism (CD) signal. The free TROP from samples was quantified as an inhibitor for the formation of the AuNP trimer. The AuNP trimer-based biosensor allowed for the selective determination of TROP in the range of 0.1-15 ng mL-1 with the limit of detection (LOD) of 21 pg mL-1 (S/N = 3) and the limit of quantitation (LOQ) of 70 pg mL-1 (S/N = 10). The use of a AuNP trimer-based biosensor with simple sample preparation functions with specificity and accuracy; this highlights its applicability for the detection of allergens in shellfish products, related products and their production lines. Furthermore, based on the less conserved sequences of TROP in phylogenetically different species, this biosensor is currently being used to identify the adulteration of shellfish products using TROP as biomarker.

Suppressing UPR-dependent overactivation of FGFR3 signaling ameliorates SLC26A2-deficient chondrodysplasias.

BACKGROUND: Mutations in the SLC26A2 gene cause a spectrum of currently incurable human chondrodysplasias. However, genotype-phenotype relationships of SLC26A2-deficient chondrodysplasias are still perplexing and thus stunt therapeutic development. METHODS: To investigate the causative role of SLC26A2 deficiency in chondrodysplasias and confirm its skeleton-specific pathology, we generated and analyzed slc26a2-/- and Col2a1-Cre; slc26a2fl/fl mice. The therapeutic effect of NVP-BGJ398, an FGFR inhibitor, was tested with both explant cultures and timed pregnant females. FINDINGS: Two lethal forms of human SLC26A2-related chondrodysplasias, achondrogenesis type IB (ACG1B) and atelosteogenesis type II (AO2), are phenocopied by slc26a2-/- mice. Unexpectedly, slc26a2-/- chondrocytes are defective for collagen secretion, exhibiting intracellular retention and compromised extracellular deposition of ColII and ColIX. As a consequence, the ATF6 arm of the unfolded protein response (UPR) is preferentially triggered to overactivate FGFR3 signaling by inducing excessive FGFR3 in slc26a2-/- chondrocytes. Consistently, suppressing FGFR3 signaling by blocking either FGFR3 or phosphorylation of the downstream effector favors the recovery of slc26a2-/- cartilage cultures from impaired growth and unbalanced cell proliferation and apoptosis. Moreover, administration of an FGFR inhibitor to pregnant females shows therapeutic effects on pathological features in slc26a2-/- newborns. Finally, we confirm the skeleton-specific lethality and pathology of global SLC26A2 deletion through analyzing the Col2a1-Cre; slc26a2fl/fl mouse line. INTERPRETATION: Our study unveils a previously unrecognized pathogenic mechanism underlying ACG1B and AO2, and supports suppression of FGFR3 signaling as a promising therapeutic approach for SLC26A2-related chondrodysplasias. FUND: This work was supported by National Natural Science Foundation of China (81871743, 81730065 and 81772377).

Ion-Exchange Chromatography Coupled With Dynamic Coating Capillary Electrophoresis for Simultaneous Determination of Tropomyosin and Arginine Kinase in Shellfish.

Tropomyosin (TM) and arginine kinase (AK) are known as two major allergens in seafood. For the first time, we demonstrate a newly developed ion-exchange chromatography coupled with dynamic coating capillary electrophoresis (IEC-DCCE) method to simultaneously analyze the TM and AK in shellfish. First, we have optimized the procedure of IEC for simple enrichment of TM and AK crude extract. By using 30 mM borate-borax at pH 9.0 with 0.3% (v/v) Tween-20 as a dynamic coating modifier for capillary electrophoresis (CE) separation, the migration time, separation efficiency and electrophoretic resolution greatly improved. The limits of detection (LOD) were 1.2 µg mL-1 for AK and 1.1 µg mL-1 for TM (S/N = 3), and the limits of quantification (LOQ) were 4.0 µg mL-1 for AK and 3.7 µg mL-1 for TM (S/N = 10). The recovery of AK ranged from 91.5 to 106.1%, while that of TM ranged from 94.0 to 109.5%. We also found that only when the concentrations of AK and TM were above LOD reported here, these proteins can stimulate human mast cell (LAD2) degranulation. Finally, the use of IEC-DCCE to analyze fresh shellfish samples highlights the applicability of this method for the simultaneous detection of these allergens in complex food systems.

Determination of a major allergen in fish samples by simple and effective label-free capillary electrophoretic analysis after background suppression in ion-exchange chromatography.

A simple analytical method using ion-exchange chromatography (IEC) coupled with capillary zone electrophoresis (CZE) was newly developed for detection and quantification of parvalbumin (PV), a major allergen, in fish. The procedure of IEC for simple enrichment of PV crude extract was optimized. By using 25 mmol/L borate-borax buffer with 15 kV separation voltage at pH 9.2 for CZE separation, the migration time, separation efficiency and electrophoretic resolution greatly improved. Under the optimal conditions, PV was determined in 2.8 min, with the limit of detection (LOD) at 0.71 µg/mL (S/N = 3) and the recoveries at 89.6%-104.7%. We also found that only when the concentration of PV was above LOD reported here was the protein capable of stimulating human mast cell degranulation, indicating the biological significance of the LOD. Finally, the use of this method to analyze fish samples with simple sample preparation highlights the applicability for detection of allergens in seafood matrices.

Effect of different surface treatments and retainer designs on the retention of posterior Pd-Ag porcelain-fused-to-metal resin-bonded fixed partial dentures.

The aim of this study was to investigate the adhesive property of palladium-silver alloy (Pd-Ag) and the simulated clinical performance of Pd-Ag porcelain-fused-to-metal (PFM), resin-bonded, fixed partial dentures (RBFPDs). A total of 40 Pd-Ag discs (diameter=5 mm) were prepared and divided into the following four groups (n=10): a) No sandblasting, used as a control; and b, 50 µm; c, 110 µm; and d, 250 µm aluminum oxide (Al2O3) particles, respectively. Another 50 discs were pre-sandblasted and divided into five groups (n=10) subjected to different treatments: e) Sandblasting, used as a control; f) silane; g) alloy primer; h) silica coating + silane and i) silica coating + alloy primer. All 90 discs were bonded to enamel with Panavia F 2.0 and then subjected to shear bond strength (SBS) testing. The fracture surfaces were examined by scanning electron microscopy. Next, 40 missing maxillary second premolar models were restored with one of the four following RBFPD designs (n=10): I) A premolar occlusal bar combined with molar double rests (MDR); II) both occlusal bars with a wing (OBB); III) a premolar occlusal bar combined with a molar dental band (MDB); and IV) two single rests adjacent to the edentulous space with a wing (SRB) used as a control. All specimens were aged with thermal cycling and mechanical loading. Subsequently, they were loaded until broken. The data were analyzed by one-way analysis of variance. Al2O3 (250 µm) abrasion provided the highest SBS (P<0.05). The alloy primer and silica + silane exhibited increased SBS. Furthermore, fracture analysis revealed that the failure mode varied among the different treatments. Whereas MDB exhibited the highest retention (P<0.05), that of OBB was greater than that of MDR (P<0.05), and the control exhibited the lowest retention. Abrasion with Al2O3 (250 µm) effectively increased the adhesive property of Pd-Ag. Additionally, treatment with the alloy primer and silica coating + silane was able to increase the adhesive property of abraded Pd-Ag. Under the present conditions, all three modified retainer types provided improved outcomes for Pd-Ag PFM RBFPDs compared with the control.

Complete genome sequence of N2-fixing model strain Klebsiella sp. nov. M5al, which produces plant cell wall-degrading enzymes and siderophores.

The bacterial strain M5al is a model strain for studying the molecular genetics of N2-fixation and molecular engineering of microbial production of platform chemicals 1,3-propanediol and 2,3-butanediol. Here, we present the complete genome sequence of the strain M5al, which belongs to a novel species closely related to Klebsiella michiganensis. M5al secretes plant cell wall-degrading enzymes and colonizes rice roots but does not cause soft rot disease. M5al also produces siderophores and contains the gene clusters for synthesis and transport of yersiniabactin which is a critical virulence factor for Klebsiella pathogens in causing human disease. We propose that the model strain M5al can be genetically modified to study bacterial N2-fixation in association with non-legume plants and production of 1,3-propanediol and 2,3-butanediol through degradation of plant cell wall biomass.

Characterization and toxicology evaluation of chitosan nanoparticles on the embryonic development of zebrafish, Danio rerio.

In the present study, chitosan nanoparticles were prepared, characterized and used to evaluate the embryonic toxicology on zebrafish (Danio rerio). The average particle size of chitosan nanoparticles was 84.86nm. The increased mortality and decreased hatching rate was found in the zebrafish embryo exposure to normal chitosan particles and chitosan nanoparticles with the increased addition concentration. At 120h post-fertilization (hpf), the rate of mortality were 25.0 and 44.4% in the groups treated with chitosan nanoparticles and normal chitosan particles at 250mg/L, respectively. At 72hpf, the hatching rate in the groups treated with normal chitosan particles were lower (P<0.01) at 300 and 400mg/L than those of the corresponding control groups, respectively. However, there were no significant differences between the groups treated with chitosan nanoparticles and the control groups across all the addition concentrations. More abundant typical malformation of embryos was observed in the groups treated with normal chitosan particles compared with those treated with chitosan nanoparticles. The LC50 (medium lethal concentration) of chitosan nanoparticles was 280mg/L at 96hpf and 270mg/L at 120hpf. As for normal chitosan particles, the LC50 was 257mg/L at both 96hpf and 120hpf. The TC50 (medium teratogenic concentration) of the zebrafish treated with chitosan nanoparticles and normal chitosan particles were 257mg/L and 137mg/L, respectively. It indicated that the chitosan nanoparticles were relatively more secure compared with normal chitosan particles.