Based on the inhibition effect on the respiratory chain activity of microorganisms by toxicants, an electrochemical method has been developed to measure the current variation of a mediator in the presence of microorga...Based on the inhibition effect on the respiratory chain activity of microorganisms by toxicants, an electrochemical method has been developed to measure the current variation of a mediator in the presence of microorganisms contacted with a toxicant. Microelectrode arrays were adopted in this study, which can accelerate the mass transfer rate of an anaiyte to the electrode and also increase the total current signal, resulting in an improvement in detection sensitivity. We selected Escherichia coli as the testee and the standard glucose- glutamic acid as an exogenous material. Under oxygen restriction, the experiments in the presence of toxicant were performed at optimum conditions （solution pH 7.0, 37℃ and reaction for 3 hr）. The resulting solution was then separated from the suspended microorganisms and was measured by an electrochemical method, using ferricyanide as a mediator. The current signal obtained represents the reoxidation of ferrocyanide, which was transformed to inhibiting efficiency, IC50, as a quantitative measure of toxicity. The IC50 values measured were 410, 570 and 830 mg/L for sodium nitrite, borax and aluminum potassium sulfate, respectively. The results show that the toxicity sequence for these three food additives is consistent with the value reported by other methods. Furthermore, the order of damage degree to the microorganism was also observed to be： sodium nitrite 〉 borax 〉 aluminum potassium sulfate 〉 blank, according to the atomic force microscopy images of E. coli after being incubated for 3 hr with the toxic compound in buffer solutions. The electrochemical method is expected to be a sensitive and simple alternative to toxicity screening for chemical food additives.展开更多
The emerging field of neuroprosthetics is focused on design and implementation of neural prostheses to restore some of the lost neural functions. Remarkable progress has been reported at most bioelectronic levels—par...The emerging field of neuroprosthetics is focused on design and implementation of neural prostheses to restore some of the lost neural functions. Remarkable progress has been reported at most bioelectronic levels—particularly the various brain-machine interfaces (BMIs)—but the electrode-tissue contacts (ETCs) remain one of the major obstacles. The success of these BMIs relies on electrodes which are in contact with the neural tissue. Biological response to chronic implantation of Microelectrode arrays (MEAs) is an essential factor in determining a successful electrode design. By altering the material compositions and geometries of the arrays, fabrication techniques of MEAs insuring these ETCs try to obtain consistent recording signals from small groups of neurons without losing microstimulation capabilities, while maintaining low-impedance pathways for charge injection, high-charge transfer, and high-spatial resolution in recent years. So far, none of these attempts have led to a major breakthrough. Clearly, much work still needs to be done to accept a standard model of MEAs for clinical purposes. In this paper, we review different microfabrication techniques of MEAs with their advantages and drawbacks, and comment on various coating materials to enhance electrode performance. Then, we propose high-density, three-dimensional (3D), silicon-based MEAs using micromachining methods. The geometries that will be used include arrays of penetrating variable-height probes.展开更多
Recent studies demonstrated that a functional brain network could be regarded as a complex network.With the help of network theory,neuroscientists can identify common organizational principles of the functional brain ...Recent studies demonstrated that a functional brain network could be regarded as a complex network.With the help of network theory,neuroscientists can identify common organizational principles of the functional brain networks.As a consequence,some non-random organizational features,such as"small world"(most of the nodes are not connected directly but can communicate with few intermediate relay steps)and"rich club"(nodes that are rich in connections tend to form strongly interconnected clubs),have been found in functional brain network.Recently,the"small world"organizational feature of neuronal functional networks in vitro was found to be influenced by external applications.However,little is known about the influence of chronic electrical stimulation on functional networks of dissociated cortical cultures during network development.In the present study,cortical cultures were electrically stimulated at a frequency of 0,0.02,and 0.2 Hz,between 7 and 26 days in vitro(DIV).The spontaneous activity of the cortical cultures was recorded using MEAs.Next,a cross-covariance method and graph theory were applied to investigate organizational feature of functional networks.Our results showed that over 3 weeks of stimulation,the network density significantly increased with maturation in the control and 0.02 Hz stimulation groups,but not in 0.2 Hz stimulation groups.Moreover,all the cultures had a small-world topology at 14,18,22,and 26 DIV,free from the effect of chronic electrical stimulation.Besides,we found an asymmetry effect that partial electrical stimulation inhibited the formation of node connections in stimulated areas.This effect was more pronounced at 0.2 Hz than at 0.02 Hz stimulation.Our results suggest that electrical stimulation does not affect the small-world properties of neural cultures.Instead,electrical stimulation modulates connectivity patterns,and neurons within the stimulated area are less connected than neurons outside the stimulated area.展开更多
基金supported by the National Natural Science Foundation of China (No. 20820102037,20935003)the National Basic Research Program (973) of China (No.2010CB933603)
文摘Based on the inhibition effect on the respiratory chain activity of microorganisms by toxicants, an electrochemical method has been developed to measure the current variation of a mediator in the presence of microorganisms contacted with a toxicant. Microelectrode arrays were adopted in this study, which can accelerate the mass transfer rate of an anaiyte to the electrode and also increase the total current signal, resulting in an improvement in detection sensitivity. We selected Escherichia coli as the testee and the standard glucose- glutamic acid as an exogenous material. Under oxygen restriction, the experiments in the presence of toxicant were performed at optimum conditions （solution pH 7.0, 37℃ and reaction for 3 hr）. The resulting solution was then separated from the suspended microorganisms and was measured by an electrochemical method, using ferricyanide as a mediator. The current signal obtained represents the reoxidation of ferrocyanide, which was transformed to inhibiting efficiency, IC50, as a quantitative measure of toxicity. The IC50 values measured were 410, 570 and 830 mg/L for sodium nitrite, borax and aluminum potassium sulfate, respectively. The results show that the toxicity sequence for these three food additives is consistent with the value reported by other methods. Furthermore, the order of damage degree to the microorganism was also observed to be： sodium nitrite 〉 borax 〉 aluminum potassium sulfate 〉 blank, according to the atomic force microscopy images of E. coli after being incubated for 3 hr with the toxic compound in buffer solutions. The electrochemical method is expected to be a sensitive and simple alternative to toxicity screening for chemical food additives.
基金This works was supported by the Natural Science Foundation of Hubei Province (No. 2002AB128)the National Natural Science Foundation of China (No.30400153).
文摘The emerging field of neuroprosthetics is focused on design and implementation of neural prostheses to restore some of the lost neural functions. Remarkable progress has been reported at most bioelectronic levels—particularly the various brain-machine interfaces (BMIs)—but the electrode-tissue contacts (ETCs) remain one of the major obstacles. The success of these BMIs relies on electrodes which are in contact with the neural tissue. Biological response to chronic implantation of Microelectrode arrays (MEAs) is an essential factor in determining a successful electrode design. By altering the material compositions and geometries of the arrays, fabrication techniques of MEAs insuring these ETCs try to obtain consistent recording signals from small groups of neurons without losing microstimulation capabilities, while maintaining low-impedance pathways for charge injection, high-charge transfer, and high-spatial resolution in recent years. So far, none of these attempts have led to a major breakthrough. Clearly, much work still needs to be done to accept a standard model of MEAs for clinical purposes. In this paper, we review different microfabrication techniques of MEAs with their advantages and drawbacks, and comment on various coating materials to enhance electrode performance. Then, we propose high-density, three-dimensional (3D), silicon-based MEAs using micromachining methods. The geometries that will be used include arrays of penetrating variable-height probes.
基金supported by the National Natural Science Fund for Outstanding Young Scholar(Grant No.81622027)the Key Program of the National Key Research and Development Program of China(Grant No.2017YFA0106100)the research fund of PLA of China(Grant Nos.AWS17J011,BWS17J024)。
文摘Recent studies demonstrated that a functional brain network could be regarded as a complex network.With the help of network theory,neuroscientists can identify common organizational principles of the functional brain networks.As a consequence,some non-random organizational features,such as"small world"(most of the nodes are not connected directly but can communicate with few intermediate relay steps)and"rich club"(nodes that are rich in connections tend to form strongly interconnected clubs),have been found in functional brain network.Recently,the"small world"organizational feature of neuronal functional networks in vitro was found to be influenced by external applications.However,little is known about the influence of chronic electrical stimulation on functional networks of dissociated cortical cultures during network development.In the present study,cortical cultures were electrically stimulated at a frequency of 0,0.02,and 0.2 Hz,between 7 and 26 days in vitro(DIV).The spontaneous activity of the cortical cultures was recorded using MEAs.Next,a cross-covariance method and graph theory were applied to investigate organizational feature of functional networks.Our results showed that over 3 weeks of stimulation,the network density significantly increased with maturation in the control and 0.02 Hz stimulation groups,but not in 0.2 Hz stimulation groups.Moreover,all the cultures had a small-world topology at 14,18,22,and 26 DIV,free from the effect of chronic electrical stimulation.Besides,we found an asymmetry effect that partial electrical stimulation inhibited the formation of node connections in stimulated areas.This effect was more pronounced at 0.2 Hz than at 0.02 Hz stimulation.Our results suggest that electrical stimulation does not affect the small-world properties of neural cultures.Instead,electrical stimulation modulates connectivity patterns,and neurons within the stimulated area are less connected than neurons outside the stimulated area.
