Isolation,identification,and virulence gene analysis of pathogenic Aeromonas dhakensis in Macrobrachium rosenbergii and histopathological observation

To identify the cause of mass mortality of adult Macrobrachium rosenbergii in a farm in Gaoyou City,Jiangsu Province,China,a dominant strain named DKQ-1 was isolated from the hepatopancreas of dying M.rosenbergii and identified as Aeromonas dhakensis by purification culture,biochemical characterization,and 16S rRNA and gyrB gene sequence analysis.The results of the challenge test revealed that the strain was highly pathogenic and the 50%lethal dose(LD_(50))in 72 h to M.rosenbergii was 1.54×10^(5)CFU/mL.The amplification results of virulence genes show that strain DKQ-1 carried 9 virulence genes,including ascV,aexT,aer,act,lip,ompAI,gcaT,acg,and exu,supporting the strong virulence of strain DKQ-1 to M.rosenbergii.Histopathological observation of the hepatopancreas,gills,and intestines indicated that DKQ-1 injection into M.rosenbergii could cause serious tissue damage,which further supported the strong virulence of this strain.In addition,a drug susceptibility test revealed that strain DKQ-1 was sensitive to 16 kinds of antibiotics,resistant to 9 kinds of antibiotics,and had intermediate resistance to spectinomycin and kanamycin.This study is the first report of A.dhakensis isolated from M.rosenbergii and provided a reference for the pathogen identification of bacterial diseases in M.rosenbergii,and for the prevention and treatment caused by A.dhakensis.

Microelectrode arrays for monitoring neural activity in neural stem cells with modulation by glutamate in vitro

In this study, a 60-channel microelectrode array(MEA) was fabricated and used to monitor the neural spikes and local field potentials(LFPs) of neurons differentiated from rat neural stem cells in vitro. The neurons were grown on the MEA surface to detect neural signals. Glutamate(Glu) was used to modulate neural activity during experiments. To enhance detection performance, platinum nanoparticles were modified onto the microelectrode site surface. Glutamate stimulated neural spikes and LFPs were recorded using the MEA. The average spike amplitude was approximately 70 μV in the normal state. The spike amplitude increased by 29% from 70 μV to 90 μV with Glu modulation. The firing rate increased by 69% from 4.01 Hz to 6.8 Hz with Glu modulation. The LFP power increased from 326 μW in the normal state to 617 μW with Glu modulation in the 0–10 Hz frequency band. Data analysis shows that neural activity stimulated by Glu modulation was recorded experimentally at high temporal-spatial resolution. These results may provide a new neuron detection method, as well as further understanding of neural stem cell spike firing and associated mechanisms.

A NEW QUANTITATIVE DETECTION METHOD OF RECOMBINANT CFP10-ESAT6 AMALGAMATION PROTEINS FROM MYCOBACTERIUM TUBERCULOSIS BASED ON MICRO-MAGNETIC PROBES STRATEGY

A new rapid,specific and sensitive method for assay of recombinant CFP10-ESAT6 amalgamation proteins from Mycobacterium tuberculosis was proposed.The method used streptavidincoated magnetic beads to enrich the specific biotinylated anti-CFP10 antibody,then adopted a sandwich-type enzyme linked immunosorbent assay technology with two kinds of monoclonal antibodies:biotinylated anti-CFP10 antibody and HRP-labeled anti-CFP10 antibody to identify the target CFP10-ESAT6 proteins,and finally detected chemiluminescence intensity by a small home-made optical sensor.It was shown that,the corresponding chemiluminescence intensity had a good logarithmic linear response to the concentration of CFP10-ESAT6 proteins when ranging at 1~1000 ng/mL,and the correlation coefficient is 0.9937.The proposed method could detect the CFP10-ESAT6 proteins with low detection limit(1 ng/mL)and the detection time could be controlled within 45 min.Compared with commonly used detection methods of M.tuberculosis,this method was easy to operate,faster,and of higher sensitivity.The achievement of the quantitative detection of CFP10-ESAT6 proteins has important scientific significance and wide application prospects in tuberculosis control.

Nanomaterial-based microelectrode arrays for in vitro bidirectional brain–computer interfaces:a review

A bidirectional in vitro brain–computer interface(BCI)directly connects isolated brain cells with the surrounding environment,reads neural signals and inputs modulatory instructions.As a noninvasive BCI,it has clear advantages in understanding and exploiting advanced brain function due to the simplified structure and high controllability of ex vivo neural networks.However,the core of ex vivo BCIs,microelectrode arrays(MEAs),urgently need improvements in the strength of signal detection,precision of neural modulation and biocompatibility.Notably,nanomaterial-based MEAs cater to all the requirements by converging the multilevel neural signals and simultaneously applying stimuli at an excellent spatiotemporal resolution,as well as supporting long-term cultivation of neurons.This is enabled by the advantageous electrochemical characteristics of nanomaterials,such as their active atomic reactivity and outstanding charge conduction efficiency,improving the performance of MEAs.Here,we review the fabrication of nanomaterial-based MEAs applied to bidirectional in vitro BCIs from an interdisciplinary perspective.We also consider the decoding and coding of neural activity through the interface and highlight the various usages of MEAs coupled with the dissociated neural cultures to benefit future developments of BCIs.

Simulation and fabrication of in vitro microfluidic microelectrode array chip for patterned culture and electrophysiological detection of neurons

To enable the detection and modulation of modularized neural networks in vitro,this study proposes a microfluidic microelectrode array chip for the cultivation,compartmentalization,and control of neural cells.The chip was designed based on the specific structure of neurons and the requirements for detection and modulation.Finite-element analysis of the chip’s flow field was conducted using the COMSOL Multiphysics software,and the simulation results show that the liquid within the chip can flow smoothly,ensuring stable flow fields that facilitate the uniform growth of neurons within the microfluidic channels.By employing MEMS technology in combination with nanomaterial modification techniques,the microfluidic microelectrode array chip was fabricated successfully.Primary hippocampal neurons were cultured on the chip,forming a well-defined neural network.Spontaneous electrical activity of the detected neurons was recorded,exhibiting a 23.7%increase in amplitude compared to neuronal discharges detected on an open-field microelectrode array.This study provides a platform for the precise detection and modulation of patterned neuronal growth in vitro,potentially serving as a novel tool in neuroscience research.

An implantable microelectrode array for simultaneous L-glutamate and electrophysiological recordings in vivo

L-glutamate,the most common excitatory neurotransmitter in the mammalian central nervous system(CNS),is associated with a wide range of neurological diseases.Because neurons in CNS communicate with each other both electrically and chemically,dualmode(electric and chemical)analytical techniques with high spatiotemporal resolution are required to better understand glutamate function in vivo.In the present study,a silicon-based implantable microelectrode array(MEA)composed of both platinum electrochemical and electrophysiological microelectrodes was fabricated using micro-electromechanical system.In the MEA probe,the electrophysiological electrodes have a low impedance of 0.018 MΩat 1 kHz,and the electrochemical electrodes show a sensitivity of 56 pAμM^(−1) to glutamate and have a detection limit of 0.5μM.The MEA probe was used to monitor extracellular glutamate levels,spikes and local field potentials(LFPs)in the striatum of anaesthetised rats.To explore the potential of the MEA probe,the rats were administered to KCl via intraperitoneal injection.K+significantly increases extracellular glutamate levels,LFP low-beta range(12–18 Hz)power and spike firing rates with a similar temporal profile,indicating that the MEA probe is capable of detecting dual-mode neuronal signals.It was concluded that the MEA probe can help reveal mechanisms of neural physiology and pathology in vivo.

Low sample volume origami-paper-based graphene-modified aptasensors for label-free electrochemical detection of cancer biomarker-EGFR

In this work,an electrochemical paper-based aptasensor was fabricated for label-free and ultrasensitive detection of epidermal growth factor receptor(EGFR)by employing anti-EGFR aptamers as the bio-recognition element.The device used the concept of paper-folding,or origami,to serve as a valve between sample introduction and detection,so reducing sampling volumes and improving operation convenience.Amino-functionalized graphene(NH 2-GO)/thionine(THI)/gold particle(AuNP)nanocomposites were used to modify the working electrode not only to generate the electrochemical signals,but also to provide an environment conducive to aptamer immobilization.Electrochemical characterization revealed that the formation of an insulating aptamer–antigen immunocomplex would hinder electron transfer from the sample medium to the working electrode,thus resulting in a lower signal.The experimental results showed that the proposed aptasensor exhibited a linear range from 0.05 to 200 ngmL^(−1)(R^(2)=0.989)and a detection limit of 5pgmL^(−1) for EGFR.The analytical reliability of the proposed paper-based aptasensor was further investigated by analyzing serum samples,showing good agreement with the gold-standard enzyme-linked immunosorbent assay.

In-situ observations of novel single-atom thick 2D tin membranes embedded in graphene

There is ongoing research in freestanding single-atom thick elemental metal patches,including those suspended in a two-dimensional(2D)material,due to their utility in providing new structural and energetic insight into novel metallic 2D systems.Graphene pores have shown promise as support systems for suspending such patches.This study explores the potential of Sn atoms to form freestanding stanene and/or Sn patches in graphene pores.Sn atoms were deposited on graphene,where they formed novel single-atom thick 2D planar clusters/patches(or membranes)ranging from 1 to 8 atoms within the graphene pores.Patches of three or more atoms adopted either a star-like or close-packed structural configuration.Density functional theory(DFT)calculations were conducted to look at the cluster configurations and energetics(without the graphene matrix)and were found to deviate from experimental observations for 2D patches larger than five atoms.This was attributed to interfacial interactions between the graphene pore edges and Sn atoms.The presented findings help advance the development of single-atom thick 2D elemental metal membranes.