This review paper presents the current research progress, challenges and future development on microelectrode array of retinal prosthesis, including epi-retinal and sub-retinal implants.
Microelectrodes ; Prosthesis Design ; Visual Prosthesis

In the neural engineering field, physiological dysfunctions are approached by identifying the target nerves and providing artificial stimulation to restore the function. Neural stimulation and recording technologies play a central role in this approach, and various engineering devices and stimulation techniques have become available to the medical community. For bladder control problems, electrical stimulation has been used as one of the treatments, while only a few emerging neurotechnologies have been used to tackle these problems. In this review, we introduce some recent developments in neural stimulation technologies including microelectrode array, closed-loop neural stimulation, optical stimulation, and ultrasound stimulation.
Electric Stimulation ; Microelectrodes ; Ultrasonography ; Urinary Bladder*

As an interface between external electronic devices and internal neural nuclei, microelectrodes play an important role in many fields, such as animal robots, deep brain stimulation and neural prostheses. Aiming at the problem of high price and complicated fabrication process of microelectrode, a microelectrode twisting machine based on open source electronic prototyping platform (Arduino) and three-dimensional printing technology was proposed, and its microelectrode fabrication performance and neural stimulation performance were verified. The results show that during the fabrication of microelectrodes, the number of positive twisting turns of the electrode wire should generally be set to about 1.8 times of its length, and the number of reverse twisting rings is independent of the length, generally about 5. Moreover, compared with the traditional instrument, the device is not only inexpensive and simple to manufacture, but also has good expandability. It has a positive significance for both the personalization and popularization of microelectrode fabrication and the reduction of experimental cost.
Equipment Design ; Microelectrodes ; Printing, Three-Dimensional

Implantable Neurostimulators ; Micro-Electrical-Mechanical Systems ; Microelectrodes

Pentoxifylline (PENTO) has been known to improve RBC fluidity, and thus improve the flux of RBC through narrow capillaries. Additionally, PENTO also decreases the O2 release from RBC. Nicotinamide (N4) has been reported to decrease the number of acutely hypoxic cells in tumors by temporarily increasing tumor blood flow. Therefore, the purpose of this study was to examine whether the combination of PENTO and NA (PENTO+NA) would reduce the radioresistance of the the FSaII murine fibrosarcoma by oxygenation the hypoxic cells. We observed a significantly enhanced radiation-induced growth delay of the FSaII tumors by PENTO-NA. Thus the enhancement ration was between 2.5 and 2.8 in growth delay assay. The TCD50 of control tumors was about 57 Gy, but that of PENTO-NA treated tumors was about 32 Gy. The TCD50 was modified by a factor of 1.8. We also observed that PENTO+NA, changes in tumor blood flow and intratumor pO2 were measured using laser Doppler flowmetry and O2 microelectrode methods. The tumor blood flow significantly increased at 10 min. after injection of PENTO+NA. Furthermore, we also found that PENTO+NA significantly increased intratumor pO2 from 8 to 19 mmHg. We concluded that PENTO+NA was far more effective than NA alone or PENTO alone. The increase in the response of tumor in vivo to X-irradiation appeared to be due mainly to an increase in the tumor oxygenation. Further studies using various concentrations of PENTO alone and in combination with NA to obtain better sequencing and maximal radiosensitization are warranted.
Capillaries ; Fibrosarcoma ; Laser-Doppler Flowmetry ; Microelectrodes ; Niacinamide* ; Oxygen ; Pentoxifylline*

Vision is one of the most important human sensations about the surrounding world. Visual deprivation not only markedly affects the life of blind people, but also gives a heavy burden to their family and the society. A visual prosthesis is an electronic device that helps the blinds to regain visual perception by directly stimulating the visual pathway using the microelectrodes implanted into the body. In recent years, visual prostheses have been developed rapidly and some devices have already become clinically available. In this paper, we reviewed the history of visual prosthesis, introduced different visual prostheses classified according to the location of the implanted stimulating electrodes. Clinical study results as well as the functional status of the currently available visual prosthesis devices were also summarized.
Blindness ; Electrodes, Implanted ; Humans ; Microelectrodes ; Visual Perception ; Visual Prosthesis

Objective: To compare the difference between the built-in and external reference electrode of microwire electrode array in the process of recording rat brain neuron firings, optimizing the production and embedding of the microwire electrode array, and providing a more affordable and excellent media tool for multi-channel electrophysiological real-time recording system. Methods: A 16 channel microwire electrode array was made by using nickel chromium alloy wires, circuit board, electrode pin and ground wires (silver wires). The reference electrode of the microwire electrode array was built-in (the reference electrode and electrode array were arranged in parallel) or external (the reference electrode and ground wire were welded at both ends of one side of the electrode), and the difference between the two electrodes was observed and compared in recording neuronal discharges in ACC brain area of rats. Experimental rats were divided into built-in group and external group, n=8-9. The test indicators included signal-to-noise ratio (n=8), discharge amplitude (n=380) and discharge frequency (n=54). Results: The microwire electrode array with both built-in and external reference electrodes successfully recorded the electrical signals of neurons in the ACC brain region of rats. Compared with the external group, the electrical signals of neurons in built-in group had the advantages of a higher signal-to-noise ratio (P＜0.05), a smaller amplitude of background signals and less noise interference, and a larger discharge amplitude(P＜0.05); there was no significant difference in spike discharge frequency recorded by these two types of electrodes (P＞0.05). Conclusion: When recording the electrical activity of neurons in the ACC brain region of rats, the microwire electrode array with built-in reference electrode recorded electrical signals with higher signal-to-noise ratio and larger discharge amplitude, providing a more reliable tool for multi-channel electrophysiology technology.
Action Potentials/physiology* ; Animals ; Brain ; Electrophysiological Phenomena ; Microelectrodes ; Neurons ; Rats

Three-electrode testing method was used to investigate the effect of temperature on electrode impedance, and the pH shifts in saline solution resulting from the electrical stimulation were also determined. Experiments in PBS (phosphate buffered solution) solution showed that the electrode impedance was almost invariable at the human body temperature range (35 degrees C-40 degrees C). And the experiments in unbuffered saline solution showed that pH shifts decreased from 0.03 to 0.005 when the frequency of biphasic charged-balanced pulses increased from 1 Hz to 100 Hz. Even stimulated by monophasic pulses (frequency is 15 Hz, amplitude is 50 microA), the stimulus-induced pH shift of electrode only varies 0.15 (anodic pulse current increased 0.15 and cathodic pulse current decreased 0.15).
Electrochemistry ; Eye, Artificial ; Materials Testing ; Microelectrodes ; Prostheses and Implants

In this paper we present an easily available method of intracellular dialysis via a microcatheter inserted into glass pipette during patch clamp experiment. An oblique hole through the glass pipette holder (above the lateral hole for cell-seal suction) is drilled, through which a microcatheter (O.D.=0.1 mm) made from the universal pipetter tip by hand-drawing passes and sticks out of the holder mouth in parallel with the Ag-AgCl electrode. With a syringe connected to the microcatheter, substitution of intracellular solution and intracellular dialysis of drugs can be achieved easily. Compared with repatch technique and intracellular solution substitution techniques used abroad, this method operates more easily and can produce more reliable results.
Dialysis ; instrumentation ; methods ; Equipment Design ; Microelectrodes ; Patch-Clamp Techniques ; instrumentation

The paper proposed a new method to design and fabricate a flexible neural microelectrode arrays (MEA) for retinal prosthesis, the ion-beam technology was introduced to decrease the width of conductive wires and the distances between wires, a high density MEA (120 microelectrodes with a matrix of 10 x 12) was fabricated on a single layer of polymer from this. The MEA was proved to possess a fine electrochemical property. In vitro test, the average impedance of MEA on 1 kHz was 16 k omega +/- 2 k omega and the average phase difference was -85 degrees +/-30 degrees.
Micro-Electrical-Mechanical Systems ; Microelectrodes ; Prosthesis Design ; Visual Prosthesis