A magnetic nanozyme platform for bacterial colorimetric detection and chemodynamic/photothermal synergistic antibacterial therapy.

Rapid, convenient, and sensitive detection of bacteria and development of novel antibacterial materials are conducive to accurate treatment of bacterial infection and reducing the generation of drug-resistant bacteria caused by overuse of antibiotics. A dual-function magnetic nanozyme, Fc-MBL@rGO@Fe3O4, has been constructed with broad-spectrum bacterial affinity and good peroxidase-like activity. Detection signal amplification was realized in the presence of 3,3',5,5'-tetramethylbenzidine (TMB) with a detection limit of 26 CFU/mL. In addition, the excellent photothermal properties of Fc-MBL@rGO@Fe3O4 could realize synergistic chemodynamic/photothermal antibacterial therapy. Furthermore, the good bacterial affinity of Fc-MBL@rGO@Fe3O4 enhances the accurate and rapid attack of hydroxyl radical (·OH) on the bacterial membrane and achieves efficient sterilization (100%) at low concentration (40 µg/mL) and mild temperature (47℃). Notably, Fc-MBL@rGO@Fe3O4 has a broad spectrum of antibacterial activity against Gram-negative, Gram-positive, and drug-resistant bacteria. The magnetic nanoplatform integrating detection-sterilization not only meets the need for highly sensitive and accurate detection in different scenarios, but can realize low power density NIR-II light-responsive chemodynamic/photothermal antibacterial therapy, which has broad application prospects.

Efficacy of rhizobacteria Paenibacillus polymyxa SY42 for the biological control of Atractylodes chinensis root rot.

Atractylodes chinensis is one of the most commonly used bulk herbs in East Asia; however, root rot can seriously affect its quality and yields. In contrast to chemical pesticides, biological control strategies are environmentally compatible and safe. For this study, 68 antagonistic bacterial strains were isolated from the rhizospheres of healthy Atractylodes chinensis. Strain SY42 exhibited the most potent fungicidal activities, with inhibition rates against F. oxysporum, F. solani, and F. redolens of 67.07 %, 63.40 % and 68.45 %, respectively. Through morphological observation and molecular characterization, strain SY42 was identified as Paenibacillus polymyxa. The volatile organic components (VOCs) produced by SY42 effectively inhibited the mycelial growth of pathogenic fungi through diffusion. SY42 significantly inhibited the germination of pathogenic fungal spores. Following co-culturing with SY42, the mycelium of the pathogenic fungus was deformed, folded, and even ruptured. SY42 could produce cellulases and proteases to degrade fungal cell walls. Pot experiments demonstrated the excellent biocontrol efficacy of SY42. This study revealed that P. polymyxa SY42 inhibited pathogenic fungi through multiple mechanisms, which verified its utility as a biocontrol agent for the control of A. chinensis root rot.

Comparison of gut bacterial communities of Hyphantriacunea Drury (Lepidoptera, Arctiidae), based on 16S rRNA full-length sequencing.

There are a large number of microorganisms in the gut of insects, which form a symbiotic relationship with the host during the long-term co-evolution process and have a significant impact on the host's nutrition, physiology, development, immunity, stress tolerance and other aspects. However, the composition of the gut microbes of Hyphantriacunea remains unclear. In order to investigate the difference and diversity of intestinal microbiota of H.cunea larvae feeding on different host plants, we used PacBio sequencing technology for the first time to sequence the 16S rRNA full-length gene of the intestinal microbiota of H.cunea. The species classification, ß diversity and function of intestinal microflora of the 5th instar larvae of four species of H.cunea feeding on apricot, plum, redbud and Chinese ash were analysed. The results showed that a total of nine phyla and 65 genera were identified by PacBio sequencing, amongst which Firmicutes was the dominant phylum and Enterococcus was the dominant genus, with an average relative abundance of 59.29% and 52.16%, respectively. PERMANOVA analysis and cluster heat map showed that the intestinal microbiomes of H.cunea larvae, fed on different hosts, were significantly different. LEfSe analysis confirmed the effect of host diet on intestinal community structure and PICRUSt2 analysis showed that most of the predictive functions were closely related to material transport and synthetic, metabolic and cellular processes. The results of this study laid a foundation for revealing the interaction between the intestinal microorganisms of H.cunea and its hosts and provided ideas for exploring new green prevention and control strategies of H.cunea.

Ultrasensitive Analysis of Exosomes Using a 3D Self-Assembled Nanostructured SiO2 Microfluidic Chip.

Conventional microfluidics with a solid mixer for exosome detection is constrained by the low binding efficiency of the solid-liquid boundary effects and reduced sensitivity of individual markers. Here, we report a 3D-SiO2 porous chip that combines nanoscale porous characteristics and multiple exosome specific markers to greatly improve the sensitivity for biosensing. The lower limit of detection was 220 particles/µL exosomes in PBS. We applied the 3D-SiO2 porous chip for prostate cancer (PCa) staging in mice and early detection of clinical PCa patients. The developed method could significantly differentiate the different stages of PCa in mice and improve the early detection rate in clinical patients. Expression of multiple specific markers in clinical serum samples identified disease fingerprints, alongside histological results, which supports the potential application of exosomes as a noninvasive surrogate biopsy for PCa.

Structure-guided steric hindrance engineering of Bacillus badius phenylalanine dehydrogenase for efficient L-homophenylalanine synthesis.

BACKGROUND: Direct reductive amination of prochiral 2-oxo-4-phenylbutyric acid (2-OPBA) catalyzed by phenylalanine dehydrogenase (PheDH) is highly attractive in the synthesis of the pharmaceutical chiral building block L-homophenylalanine (L-HPA) given that its sole expense is ammonia and that water is the only byproduct. Current issues in this field include a poor catalytic efficiency and a low substrate loading. RESULTS: In this study, we report a structure-guided steric hindrance engineering of PheDH from Bacillus badius to create an enhanced biocatalyst for efficient L-HPA synthesis. Mutagenesis libraries based on molecular docking, double-proximity filtering, and a degenerate codon significantly increased catalytic efficiency. Seven superior mutants were acquired, and the optimal triple-site mutant, V309G/L306V/V144G, showed a 12.7-fold higher kcat value, and accordingly a 12.9-fold higher kcat/Km value, than that of the wild type. A paired reaction system comprising V309G/L306V/V144G and glucose dehydrogenase converted 1.08 M 2-OPBA to L-HPA in 210 min, and the specific space-time conversion was 30.9 mmol g-1 L-1 h-1. The substrate loading and specific space-time conversion are the highest values to date. Docking simulation revealed increases in substrate-binding volume and additional degrees of freedom of the substrate 2-OPBA in the pocket. Tunnel analysis suggested the formation of new enzyme tunnels and the expansion of existing ones. CONCLUSIONS: Overall, the results show that the mutant V309G/L306V/V144G has the potential for the industrial synthesis of L-HPA. The modified steric hindrance engineering approach can be a valuable addition to the current enzyme engineering toolbox.

Rapid identification of bacteria directly from blood cultures by Co-magnetic bead enrichment and MALDI-TOF MS profiling.

Direct identification of bacteria in blood cultures using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is interfered with by a variety of non-bacterial proteins derived from blood cells and culture media. Thus, appropriate pre-treatments are needed for successful identification. Here, the bacteria in blood culture bottles were enriched using co-magnetic beads and processed for MALDI-TOF MS profiling. In this strategy, the Fc-containing mannose-binding lectin-coated Fe3O4 (Fc-MBL@Fe3O4) is incorporated with human IgG-coated Fe3O4 (IgG@Fe3O4) to form co-magnetic beads, which can recognize both Gram-positive and Gram-negative bacteria. Compared to single magnetic beads Fc-MBL@Fe3O4 or IgG@Fe3O4, co-magnetic beads resulted in better bacterial capture efficiency and, therefore, could decrease the false-negative results. Our proposed strategy is much more suitable for enrichment of clinically unknown bacteria from blood culture bottles for MALDI-TOF MS database identification.

Releasing bacteria from functional magnetic beads is beneficial to MALDI-TOF MS based identification.

Bacterial infections are the key cause of morbidity and mortality worldwide. Matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS)-based bacterial identification has been widely accepted in the clinic. Functional material, such as rabbit immunoglobulin G-modified Fe3O4 (IgG@Fe3O4) and fragment crystallizable mannose binding lectin-modified Fe3O4 (FcMBL@Fe3O4), is used to capture bacteria from biological samples for MALDI-TOF MS identification, and the bacteria MS signals are usually obtained by directly smearing enriched bacteria on a MALDI target with MALDI matrix solution. However, the accuracy of identification based on MALDI-TOF MS may be affected by the presence of functional molecules, especially proteins, resulting in errors in the comparison with the standard bacterial spectra in the database. Moreover, the long-term presence of the magnetic beads on the MALDI-TOF target may reduce the instrument service life. In this study, we constructed FcMBL@Fe3O4 and used it to capture bacteria from both aqueous solution and bovine blood, and the bacterial identification accuracy based on different target preparation methods was compared. In the presence of Ca2+, the similarity scores for bacteria identified with FcMBL@Fe3O4 were ~88% and ~82% for Staphylococcus. aureus and Escherichia coli, respectively. In the presence of ethylenediaminetetraacetic acid (EDTA), bacteria separate from FcMBL@Fe3O4, resulting in similarity scores of ~96% and ~92% for S. aureus and E. coli, respectively. These results indicate that the functional proteins on the surface of nanoparticles affect the accuracy of identification accuracy based on the MALDI-TOF MS database. Thus, the release of bacteria from the functional material could increase the identification accuracy and be beneficial for maintaining the instrument.

Cross-Linked Polyamide Chains Enhanced the Fluorescence of Polymer Carbon Dots.

Carbon dots (CDs) have attracted tremendous attention for their outstanding advantages in luminescence. Here, α-amino-substituted lysine derivatives with the determined chemical structure were employed as precursors to obtain bright and highly stable fluorescent CDs through a facile hydrothermal route. The relationships among the chemical structure of precursors, CD fluorescence, and particle size were investigated. The results indicated that increased numbers of functional groups in precursors could promote the degree of cross-linking and lead to a smaller size, better fluorescent properties, and stronger stability of CDs. The C-CDs that were prepared from lysine derivatives with most functional groups showed excitation-dependent dual excitation and dual emission (DE2), high-stability luminescence, strong resistance to photobleaching, and high selectivity to Fe3+ and could be used as a sensitive probe for Fe3+ detection.

Elevated SPINK2 gene expression is a predictor of poor prognosis in acute myeloid leukemia.

Acute myeloid leukemia (AML) has a high mortality rate and its clinical management remains challenging. The aim of the present study was to identify the hub genes involved in AML. In order to do so, the gene expression data of the GSE9476 database, including 26 AML and 10 normal samples, were downloaded from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) were then identified via bioinformatics analysis. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses were performed on DEGs. Furthermore, the most upregulated genes were selected for further investigation in the Oncomine, gene expression profiling interactive analysis and UALCAN datasets. In total, 1,744 upregulated and 1,956 downregulated genes were detected. The GO and KEGG results revealed that upregulated genes were enriched in metabolic processes, while downregulated genes were associated with the immune response. Serine protease inhibitor Kazal-type 2 (SPINK2) ranked first among all the upregulated genes and was regarded as a hub gene in the development of AML. The overexpression of SPINK2 was validated in 12 patients with AML from the Linyi Central Hospital and in data from the Oncomine and Gene Expression Profiling Interactive Analysis (GEPIA) databases. Furthermore, the UALCAN and GEPIA datasets demonstrated that patients with high SPINK2 levels had shorter survival times. In conclusion, the results from the present study revealed that the SPINK2 gene was upregulated in patients with AML and that elevated SPINK2 expression was associated with poor outcomes in these patients.

Comparison with reconstruction algorithms in magnetic induction tomography.

Magnetic induction tomography (MIT) is a kind of imaging technology, which uses the principle of electromagnetic detection to measure the conductivity distribution. In this research, we make an effort to improve the quality of image reconstruction mainly via the image reconstruction of MIT analysis, including solving the forward problem and image reconstruction. With respect to the forward problem, the variational finite element method is adopted. We transform the solution of a nonlinear partial differential equation into linear equations by using field subdividing and the appropriate interpolation function so that the voltage data of the sensing coils can be calculated. With respect to the image reconstruction, a method of modifying the iterative Newton-Raphson (NR) algorithm is presented in order to improve the quality of the image. In the iterative NR, weighting matrix and L1-norm regularization are introduced to overcome the drawbacks of large estimation errors and poor stability of the reconstruction image. On the other hand, within the incomplete-data framework of the expectation maximization (EM) algorithm, the image reconstruction can be converted to the problem of EM through the likelihood function for improving the under-determined problem. In the EM, the missing-data is introduced and the measurement data and the sensitivity matrix are compensated to overcome the drawback that the number of the measurement voltage is far less than the number of the unknown. In addition to the two aspects above, image segmentation is also used to make the lesion more flexible and adaptive to the patients' real conditions, which provides a theoretical reference for the development of the application of the MIT technique in clinical applications. The results show that solving the forward problem with the variational finite element method can provide the measurement voltage data for image reconstruction, the improved iterative NR method and EM algorithm can enhance the image quality from different points, and the proposed image segmentation can make the lesions of the reconstruction image more likely to be identified.