e.g., Iridium oxide, Titanium nitride and platinum black, to improve sensitivity and signal-to-noise ratio.22. Typical MEA based neurochip system includes five.
Copyright © 2014 American Scientific Publishers All rights reserved Printed in the United States of America
Journal of Biomaterials and Tissue Engineering Vol. 4, 1–8, 2014
Development of Multiple Types of Neurochips Rongyu Tang1 † , Li Zhang2 † , Junjie Li1 , Changyong Wang1 , Zhiqiang Liu1 , Yao Han1 , and Qiuxia Lin1 ∗ 1
Department of Advanced Interdisciplinary Studies, Institute of Basic Medical Sciences and Tissue Engineering Research Center, Academy of Military Medical Sciences, Beijing 100850, China 2 Department of Oral and Maxillofacial Surgery, General Hospital of Shenyang Military Command, Shenyang, China
REVIEW
The biological activity of neural tissue and cells are constantly influenced by and closely related to the surrounding microenvironment. The ability to construct and control microenvironment is essential for many neuroscientific studies, including tissue engineering, stem cell differentiation induction, in vitro drug screening and disease models. In the past 40 years multiple types of neurochips emerged in responding to the needs of neuroscience research in vitro adopting the state-of-the-art microfabrication and microelectronics technologies. Microfabrication techniques were used to construct three-dimensional structures, e.g., the tissue culture scaffold, perfusion microfluidics or microenvironment recreation, according to the requirement of experiments, either providing forces to capture and separate cells, guidance cue to distribute cells and construct tissue or transportation to deliver oxygen, drug and nutrition. The neurochip integrating bioelectric sensors and functional circuits further acquired the capabilities of signal detection, cell stimulation and data analysis, becoming a multi-functional platform of neuroscience research. This review presented the classification, the manufacture techniques, the development history and the application of neurochips. The progress of our laboratory in developing multiple types of neurochips and system was also introduced.
Keywords: Microelectrode Array, Neurochip, Tissue Engineering, Neural Culture.
CONTENTS 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2. Types of Neurochip . . . . . . . . . . . . . . . . . . . . 2.1. Neurochip Based on Soft Lithography . . . . . 2.2. Neurochip Based on Microelectronic Sensors 2.3. Hybrid Neurochip . . . . . . . . . . . . . . . . . . 3. The Applications of Neurochip . . . . . . . . . . . . . 3.1. Neural Tissue Engineering . . . . . . . . . . . . 3.2. Neuropathology and Pharmacology . . . . . . . 3.3. Basic Neuroscience . . . . . . . . . . . . . . . . . 4. Outlooks . . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledgments . . . . . . . . . . . . . . . . . . . . . References and Notes . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
. . . . . . . . . . . .
1 3 3 4 5 6 6 6 6 6 7 7
1. INTRODUCTION Interfacing with neural cell and tissue in vitro using chip based microstructure1 and microelectronic sensors2 is an important milestone in modern neuroscience, which laid the foundation for further development of neural tissue engineering, neurological drug screening, neural stem cells research and many other neurosciences conducted in vitro. The development of these studies put ∗ †
Author to whom correspondence should be addressed. These two authors contributed equally to this work.
J. Biomater. Tissue Eng. 2014, Vol. 4, No. xx
forward demands on the construction and intervention of microenvironment, especially on the detection and analysis of neural signals. Neuroscience research with assists of microfabricated chips (Neuroscience-on-chip,3 Neural-biology-on-chip4) emerged and multiple types of neurochips5, 6 developed according to various research demands. Microfabrication technology7 is a general term for a series of techniques to manufacture components with micron or submicron precision, including integrated circuit (IC), microelectromechanical systems (MEMs), photolithography, soft lithography, etc. Microfabrication technology is a crucial component of neurochip technology and opens the door for fast and mass production of neurochips with low cost. Microfabrication techniques are capable of spatial structures construction and surface chemistry modification as ways to control microenvironment and thereby to manipulate cells, e.g., high precision drug delivery, cell capture, sorting and growth guidance. Microfabricated sensor and functional circuit further extended the function of neurochip. The integration of microelectronics into a monolithic chip not only minimized the devise, but also provided precision and repeatability to experiment parameters.
2157-9083/2014/4/001/008
doi:10.1166/jbt.2014.1247
1
Development of Multiple Types of Neurochips
Tang et al.
Rongyu Tang
REVIEW
Li Zhang
Junjie Li
Changyong Wang
Zhiqiang Liu
2
J. Biomater. Tissue Eng. 4, 1–8, 2014
Tang et al.
Development of Multiple Types of Neurochips
Yao Han
Qiuxia Lin
REVIEW
The neurochips were widely used in different levels of researches, e.g., the molecular level (neural transmitter, ion channels, synapse), the cellular level (neurons, glial cells), the subsystem level (neural tissue engineering, neural networks) and system level. Neurochip provided an integrated solution and multi-functional platform for neuroscience research. Neurochips can be classified according to different methods. This review introduces neurochips by fabrication techniques and build-in sensor types. Applications of neurochips in various fields were then overviewed, followed by the introduction to the development of multiple types of neurochips in our laboratory.
2. TYPES OF NEUROCHIP 2.1. Neurochip Based on Soft Lithography Soft lithography is a series of microfabrication techniques based on silicone rubber (PDMS) molding and thermal curing, that pioneered by Whitesides group.1 This technique typically requires only single step of photolithography procedure for mold fabrication and therefore can be mass duplicated in a common biology laboratory. Many microfabrication techniques further derived based on fundamental soft lithography, including the microfluidics, the micro-contact printing and stencil patterning. Microfluidic chip and micro-contact printed chip are common and widely used types of neurochip based on soft lithography. Soft lithography reduced the technique barrier and costs to fabricate neurochips. Soft lithography based neurochip can be designed and fabricated in a common biology laboratory with basic equipments of photolithography. This J. Biomater. Tissue Eng. 4, 1–8, 2014
type of neurochip possesses many congenital advantages and prevailed as the major type of neurochip. PDMS is highly permeable to oxygen and carbon dioxide, which is vital to maintain cell survive and stabilize metabolism inside neurochips. PDMS is also transparent and flexible which extended its compatibility with optical survey and mechanical intervention approaches. The lack of embedding sensor and microelectronics is greatly compensated by the compatibility with external optical and mechanical equipments, e.g., microscope, chromatogram, pump and flow cytometer. Soft lithography molded PDMS can be plasma treated and covalent bonded with substrates, e.g., glass or polymers, obtaining chamber and channels, which is suitable for cell culture and fluid transportation. Many neuroscience researches benefited from these characteristics, e.g., on aspects of optics, mechanics and microfluidics. In the optics, transparent and micro-sized neurochip allows microscopic examination. Online optical monitoring of neural connectome was realized by assembling a microfluidic chip with an external image sensor and an embedded system.8 Optic stimulation and inhibition of optogenetic transfect neurons in neurochip can be readily conducted with external light source, performing targeted interrogation of neural circuit by visually guided whole-cell electrophysiological measurements.9 In aspect of mechanics, astrocytes were cultured on PDMS microcolumns and the degree of bending signifies the direction and magnitude of the shearing force between the cell and the surface.10 In aspect of microfluidics, spatial and temporal controlled perfusion of nutrition and oxygen provided foundation for tissue engineering, pharmacology and chronic researches. Precisely controlled perfusion of 3
Development of Multiple Types of Neurochips
Tang et al.
REVIEW
soluble reagent and medicine enables targeted stimulation, differential transfection and drug screen.11 With external programmed pumps and switches, complex perfusion protocol can be realized, e.g., an automated perfusion neurochip comprises 96 chambers and 16 multiplexed channels which is capable of preparing individually formulated medium in each chamber.12 Our laboratory developed multiple types of neurochips including a soft lithography based neurochip for neural tissue engineering research (Fig. 1). This microfluidic neurochip generated laminar flow from gravity force without using external pump. The laminar flow distributed the dissociated neural cells into stripes inside a microfluidic chamber. The growth and connecting of neural processes between cell layers can be monitored conveniently with optical microscopy. This soft lithography based neurochip contributed to the understanding of neural tissue morphogenesis. 2.2. Neurochip Based on Microelectronic Sensors Neurochips purely based on soft lithography without imbedded sensor or electronics rely heavily on external equipment and are not self-contained in performing control and interaction tasks, e.g., data acquisition, temperature control and selective stimulation. Microelectronic sensor based neurochips greatly expanded the capability of neurochips. Different types of microelectronic sensors offer capability of acquiring dynamic neural signals, e.g., action potential, field potential, membrane current. The integrated electronic circuit makes multiple functions possible, e.g., signal modulation, signal amplification, multiplexing, analog to digital converting and signal analysis. Many types of microelectronic sensors for neural interfacing purpose have emerged and impelled the development of neurochip and neuroscience research (Table I). Manufacture of microelectronic sensors employed microfabrication techniques adopted from IC industry, e.g., integration circuit technology, complimentary metal oxide semiconductor technology, photolithography, metal sputter and reactive ion etching etc. These manifold types of sensors imbedded in neurochip works on different mechanisms resulting in distinguished performance on sensitivity, addressing and spatial resolution. Four common types
(a)
(b)
Fig. 1. (a) Soft lithograph based neurochip fabricated in our laboratory. (b) The microfluidic channels merged into one chamber for layered neural culture. Scale bar: 50 m.
4
Table I. The research history and milesones of Neurochip based on microelectronic sensors. Years
Events
1970s 1980s
The first MEA sensors for bioelectronic monitoring in vitro2 The first multichannel recording from neural culture using MEA13 FETs array for neural interfacing14 The first designated Neurochip15 The emergence of commercialized MEA and systems (Multichannel systems GmbH, Plexon Inc., Cyberkinetics Inc.) The emergence of high density FETs array with ten thousands of channels16 Nanometer sized electrodes array17
1990s 2000s
2010s
of neuroelectrophysiological sensors were briefly introduced in the following: Light addressable potentiometric sensor (LAPS): LAPS measures the photoeffect-induced current, which reflects the energy state of illuminated area including the field potential caused by neural excitation. The addressing approach of LAPS is novel and provided freedom to select sensitive region from virtually the whole surface area of the sensor by light focusing and targeting. Different methods have been utilized to improve the signal-to-noise ratio of LAPS.18 Field-effect transistors (FETs): The architecture of FETs sensor is chiefly based on that of CMOS and therefore can be manufactured on the production line of IC industry. This endows FETs with the advantages of high precision, large scale integration and mass production.19 FETs sensor has achieved very high spatial resolution,16 which is a favorable characteristic for neural transducer. Integrated patch clamps: The sensitivity of patch clamp is extremely high and is capable of detecting pico-ampere current through single ion channel. Integrated patch clamp was developed aiming to raise the spatial resolution while keeping the high sensitivity of traditional patch clamp.20 Microelectrode array (MEA): The performance of MEA on sensitivity and spatial resolution is more balanced in comparison with FETs and integrated patch clamps. MEA is capable of sensing microvolt range action potential synchronously with tens to ten thousands channels.21 MEA is the most common type in these sensors, and is introduced with emphasis in following sections. Typical MEA was often fabricated on substrate of silicon or glass utilizing microfabrication techniques, e.g., photolithography, metal sputter, reactive ion etching (RIE) and plasma enhanced chemical vapor deposition (PECVD). Nobel metals, e.g., platinum, gold and Iridium were generally used for the conductor of microelectrodes. The tip of microelectrodes requires high specific surface coatings, e.g., Iridium oxide, Titanium nitride and platinum black, to improve sensitivity and signal-to-noise ratio.22 Typical MEA based neurochip system includes five components: MEA sensor, peripheral circuits, a computer, J. Biomater. Tissue Eng. 4, 1–8, 2014
Tang et al.
Development of Multiple Types of Neurochips
the software and the cell supporting modules. The microelectrodes transmit local action potential to peripheral circuit for amplification and modulation. Acquired analog signal was converted into digital signal for online processing or stored in hard disk for offline analysis. Our laboratory designed and fabricated MEA sensor 23 and system (Fig. 2). The 60 channels MEA was fabricated on glass substrate using ITO as the conductor of microelectrodes. Tips of the microelectrodes were coated with platinum black. The MEA system consists of a home-made amplifier, a data acquisition cards (National Instrument, USB-6259) and a Labview based software. The system has 32 channels with 200 times amplification scale and 35 Hz ∼15 KHz passband (−3dB cutoff frequency).
(a)
(b)
Fig. 2. (a) The MEA developed in our laboratory (60 channels, ITO conductor, glass substrate). Inset: Platinum black coated microelectrode of 30 m diameter. (b) The homemade MEA system (pMEA32-III).
J. Biomater. Tissue Eng. 4, 1–8, 2014
Cell patterning aimed to regulate cell position and the route of intercellular connectivity using approaches e.g., surface chemistry and topography features. The control over cell morphology and network topology is of interest to neuroscience researchers due to the close related function of neural circuit with the connectome and morphology. Hybrid neurochip combining microelectronic sensor with cell patterning techniques greatly promoted the research on organized neural network in vitro and the understanding to group behavior of neurons. Many techniques were adopted to pattern neural cells on surface of microelectronic sensors, including chemical cues, topographical features and soft lithographical structures. Different hybrid neurochips emerged with patterned neural cells on microelectronic sensors. Microfabricated cages on microelectrodes trapped somas while allowing penetration and connection of neurites to form neural networks. The cage greatly improved the reliability of monitoring and stimulation. The specificity of one-neuron-to-oneelectrode is convenient for studying small cultured neural networks.27 Microfluidic channels provided guidance to the growth of neurites,28 Micro-contact printed polyD-lysine hydrophilic pattern encouraged cell alignment to micro-holes on surface of SiN resulting in improved coupling of neurons to integrated planar patch-clamp.29 Superimposed topographic patterns and chemical cues provided pronounced directional selectivity.30 These hybrid neurochips having patterned or guided neuronal growth on sensor interfaces enabled the establishment and interrogation of defined networks for the convenience of neuroscientific studies. Our laboratory developed a hybrid neurochip with carbon nano-tube (CNT)/matrigel, a composite hydro gel showing enhanced effect on cell adhesion and neurite growth, micro-contact printed on MEA (Fig. 4). Alternate printing scheme was applied leaving half of the nodes uncovered in order to differentiate the effect of the CNT/matrigel on cell adhesion and signal coupling. 5
REVIEW
2.3. Hybrid Neurochip As described the soft lithography based neurochip and microelectronic sensor based neurochip respectively possess distinctive advantages, e.g., the ability on signal detection, on cell culture and on microenvironmental control.24 Hybrid neurochips combined these techniques and advantages therefore provided more functions and extended the application domains. FETs array, integrated circuits and microfluidics were combined to construct an automated neural cell based biosensor for the detection of chemical compounds and biological toxins, which is a promising high-throughput neuron-based drug screening systems.25 Optical and MEA sensors were combined with microfluidics making possible of synchronous chemical stimulation, calcium imaging and electrophysiology recording,26 which is a multifunctional tool for basic neuroscience research. Our laboratory developed hybrid neurochip combining MEA with microfluidic structures capable of electrophysiology interfacing and chemical stimulation (Fig. 3). Spatially targeted delivery of medicine to axon or soma was realized with the guidance of microfluidic channels. Microelectrodes were aligned with medicine perfusion channels and cell culture chambers to make sure recording of correlated neural response to stimulation of medicines. This neurochip was developed to be a platform for neuropharmacology and electrophysiology researches.
Fig. 3. The hybrid neurochip developed in our laboratory combining MEA with microfluidics.
Development of Multiple Types of Neurochips
Tang et al.
the environment of brain. Spontaneous generated and stimulation evoked spikes were recorded from the three dimensional connected neural networks grown inside the neurochip.33
REVIEW
Fig. 4. The hybrid neurochip based on MEA and micro-contact printing. Inset: florescent of the printed CNT/matrigel on microelectrodes.
The above sections introduced varying neurochips and classified them, according to the fabrication techniques and build-in sensors, into three catalogues: (I) the neurochips without sensor embedded (mainly based on soft lithography), (II) the neurochips with microelectronic sensors integrated, (III) the hybrid neurochips combining sensors with other techniques, e.g., microfluidics and cell patterning. Following sections will give a brief introduction to the application of these neurochips in neuroscience researches.
3. THE APPLICATIONS OF NEUROCHIP Multiple types of neurochips with respective features and advantages have been widely used in the fields of neuroscience, e.g., neural tissue engineering, neuropharmacology and basic neuroscience. 3.1. Neural Tissue Engineering The advantages on microenvironment construction and signal interfacing have made neurochip a favorable platform for neural tissue engineering researches. Microfabricated physical structure and chemical substances in microenvironment are used to influence the tissue morphogenesis and the express of biochemical characteristics. Layered neural tissue was recreated mimicking the structure of cortex using thermally gelled agarose-alginate mixture as the scaffold inside a soft lithography based neurochip which can be used for neurodegenerative diseases or corticogenesis studies.31 Multiple cell types were cultured in a transwell structure neurochip to model the brain-blood-barrier function and evaluate pharmacological passage to brain. The cells can be monitored with external microscope or integrated electrodes while exposing to fluid shear stress or to biochemical stimulation.32 Microelectronic sensor and stimulator realized the electrophysiological monitoring and intervention serving as the interface of the neurochip system to the engineered neural tissue. A stack of MEAs and microfluidic channels were assembled with layered approach into three dimensional neurochip approximating 6
3.2. Neuropathology and Pharmacology Neural cells and tissue cultured in neurochips were used as in vitro model of neurological disease, such as the model of Alzheimer’s disease and neuroinflammatory.34 Many neuropharmacology research platforms based on neurochips emerged for screening and detection of medicine, toxic and biochemical substances. A microfluidic neurochip based platform was used for nerve injury and regeneration research capable of partial chemical stimulation and observation of deterioration and regeneration.35 A MEA based electrophysiology and neurochemistry research platform capable of synchronous monitoring of action potential and neurotransmitters found the extracellular dopamine level affect the strength of membrane current. The integration of both neural-electrical and neural-chemical recording hold potential on study of neural communication which is inherently both electrical and chemical modulated.36 On neurotoxicity research neurochip with integrated module of protein purification was used to study the resistance to neurotoxins.37 3.3. Basic Neuroscience Neurochips were widely used in all aspects of the basic neuroscience researches, including differentiation of neural stem cells, biochemical pathway, synaptic plasticity, coding of memory38 and neural development.39 These neural processes were related with many factors, including the interaction and signaling of biochemical substances e.g., hormones, enzymes and extracellular matrix proteins and even the mechanic property of microenvironment. The multiple functions in structure construction, modification of surface chemistry and delivery of soluble material made neurochip a strong platform for basic neuroscience research. Many researches were reported using neurochips, e.g., the effect of growth factor on neural stem cells40 and the induction of differentiation with stiffness of substrate.41, 42
4. OUTLOOKS Neurochip technology has been rapidly developed and widely applied in many aspects of neurosciences including neural tissue engineering. The physical structure, surface chemistry and fluidic transportation of neurochips induce and regulate the cell adhesion, migration, neurite outgrowth, synaptic connection and genetic expression. Integrated or external sensors of neurochip can perform real time, multichannel, noninvasive and long term interaction with neural cells and tissue. Neurochip technology provided the ability of high-precision fabrication, microenvironment control and cell signal transduction that J. Biomater. Tissue Eng. 4, 1–8, 2014
Tang et al.
6.
7. 8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
Acknowledgments: This work was supported by National Natural Science Foundation of China (Nos. 61178082; 31271034). 19.
References and Notes 1. Y. Xia and G. M. Whitesides, Soft lithography. Annu. Rev. Mater. Sci. 28.1 (1998). 2. C. A. Thomas, Jr., P. A. Springer, G. E. Loeb, Y. Berwald-Netter, and L. M. Okun, A miniature microelectrode array to monitor the bioelectric activity of cultured cells. Experimental Cell Research 74, 1 (1972). 3. A. K. Soe, N. Saeid, and K. Khashayar, Neuroscience goes on a chip. Biosens. Bioelectron. 35.1 (2012). 4. N. Z. Li, A. Tourovskaia, and A. Folch, Biology on a chip: Microfabrication for studying the behavior of cultured cells. Critical Reviews™ in Biomedical Engineering 31.5 and 6 (2003). 5. A. Gramowski, K. J. gelt, S. Stuwe, R. Schulze, G. P. McGregor, A. Wartenberg-Demand, J. Loock, O. Schroder, and D. G. Weiss,
J. Biomater. Tissue Eng. 4, 1–8, 2014
20.
21.
22.
Functional screening of traditional antidepressants with primary cortical neuronal networks grown on multielectrode neurochips. European Journal of Neuroscience 24, 2 (2006). A. Charrier, D. Martinez, R. Monette, T. Comas, R. Movileanu, C. Py, M. Denhoff, A. Krantis, and G. Mealing, Cell placement and guidance on substrates for neurochip interfaces. Biotechnol. Bioeng. 105, 2 (2010). M. J. Madou, Fundamentals of Microfabrication: The Science of Miniaturization. CRC Press (2002). G. Zheng, S. A. Lee, Y. Antebi, M. B. Elowitz, and C. Yang, The ePetri dish, an on-chip cell imaging platform based on subpixel perspective sweeping microscopy (SPSM). Proceedings of the National Academy of Sciences 108, 41 (2011). V. Jokinena, P. Sakhab, P. Suvantoa, C. Riverab, S. Franssilaa, S. E. Lauri, and H. J. Huttunen, A microfluidic chip for axonal isolation and electrophysiological measurements. Journal of Neuroscience Methods 212, 2 (2013). I. R. Minev, P. Moshayedi, and J. W. Fawcett, Interaction of glia with a compliant, microstructured silicone surface. Journal of Acta Biomaterialia 9, 6 (2013). G. Mauleon, C. P. Fall, and D. T. Eddington, Precise spatial and temporal control of oxygen within in vitro brain slices via microfluidic gas channels. PloS One 7, 8 (2012). R. Gómez-Sjöberg, A. A. Leyrat, D. M. Pirone, C. S. Chen, and S. R. Quake, Versatile, fully automated, microfluidic cell culture system. Anal. Chem. 79, 22 (2007). J. Pine, Recording action potentials from cultured neurons with extracellular microcircuit electrodes. Journal of Neuroscience Methods 2, 1 (1980). P. Fromherz, A. Offenhausser, T. Vetter, and J. Weis, A neuronsilicon junction: A Retzius cell of the leech on an insulated-gate field-effect transistor. Science 252, 5010 (1991). M. Maher, J. Wright, J. Pine, and Y. C. Tai, A microstructure for interfacing with neurons: The Neurochip. Proceedings of the 20th Annual International Conference of the IEEE (1998), Vol. 4. B. Eversmann, M. Jenkner, F. Hofmann, C. Paulus, R. Brederlow, B. Holzapfl, P. Fromherz, M. Merz, M. Brenner, M. Schreiter, R. Gabl, K. Plehnert, M. Steinhauser, G. Eckstein, D. SchmittLandsiedel, and R. Thewe, A 128 × 128 CMOS biosensor array for extracellular recording of neural activity. IEEE Journal of Solid-State Circuits 38, 12 (2003). J. T. Robinson, M. Jorgolli, A.Shalek, M. Yoon, R. S. Gertner, and H. Park, Vertical nanowire electrode arrays as a scalable platform for intracellular interfacing to neuronal circuits. Nat. Nanotechnol. 7, 3 (2012) A. B. M. Ismail, T. Yoshinobu, H. Iwasaki, H. Sugihara, T. Yukimasa, I. Hirata, and H. Iwata, Electrical properties of a light-addressable microelectrode chip with high electrode density for extracellular stimulation and recording of excitable cells. Biosens. Bioelectron. 16 (2001). P. Fromherz, Neuroelectronic interfacing: Semiconductor chips with ion channels, nerve cells, and brain. Nanoelectronics and Information Technology (2003). C. Py, M. W. Denhoff, M. Martina, R. Monette, T. Comas,T. Ahuja, D. Martinez, S. Wingar, J. Caballero, S. Laframboise, J. Mielke, C. Luk, N.Syed, and G. Mealing, A novel silicon patch clamp chip permits high fidelity recording of ion channel activity from functionally defined neurons. Biotechnol. Bioeng. 107, 4 (2010). U. Egert, B. Schlosshauer, S. Fennrich, W. Nisch, M. Fejtl, T. Knott, T. Muller, and H. Hammerle, A novel organotypic long-term culture of the rat hippocampus on substrate-integrated multielectrode arrays. Brain Research Protocols 2 (1998). S. Y. Chen, W. H. Pei, H. Zhao, Q. Gui, R. Y. Tang, Y. F. Chen, X. L. Fang, and H. D. Chen, 32-site microelectrode modified with Pt black for neural recording fabricated with thin-film silicon membrane. Science China Information Sciences 1, 7 (2013).
7
REVIEW
contributed to the progress of neural tissue engineering research. Traditional electrophysiological and biochemical sensors, e.g., patch clamp and ion selective electrodes, can only probe a fraction of the overall electrical activity or neurotransmitter dynamics hindered by the limitation of the signal resolution or the density of channels. However, the nervous system is believed working in distributed or parallel computing manner with numerous neurons interacted in emergent level. Future development of the neurochip will face the challenge of recreating complex neural tissue inside neurochips and building advanced microelectronic sensors. Neurochip with high bandwidth, large-scale cell colony and nano resolution are expected. Revealing of the complete image of neural activity will most likely to happen in an in vitro engineered neural tissue inside a three dimensional neurochip equipped with extremely high density sensors. Soft lithography based neurochips have been widely accepted in biological laboratories and appeared in literatures due to its versatility, cost efficiency and relatively lower technical barriers. In comparison microelectronic sensor based neurochips have not been universally accepted despite their apparently more advanced transducer and complex functions. In the past half century, the reduction of costs in IC industry obeyed Moore’s Law. There are good reasons to believe the same will happen on once standardized and commercialized neurochips. In addition integrated temperature sensor, PH value control and automated microfluidics can work self-efficiently without sustain of desktop incubator. This will greatly reduce the cost and dependence on large scale equipments. Based on these reasons application of sensor based neurochips will be rapidly expanded once emerged on production line of IC industry. Diversified, high-precision, high-throughput, low-cost neurochips will continue to promote the development of neuroscience.
Development of Multiple Types of Neurochips
REVIEW
Development of Multiple Types of Neurochips 23. R. Y. Tang, W. H. Pei, S. Y. Chen, H. Zhao, Y. F. Chen, Y. Han, C. L. Wang, and H. D. Chen, Fabrication of strongly adherent platinum black coatings on microelectrodes array. Science China Information Sciences 1, 11 (2013). 24. F. Morin, N. Nishimura, L. Griscom, B. LePioufle, H. Fujita, Y. Takamuraa, and E. Tamiya, Constraining the connectivity of neuronal networks cultured on microelectrode arrays with microfluidic techniques: A step towards neuron-based functional chips. Biosens. Bioelectron. 21 (2006). 25. B. D. DeBusschere and G. T. A. Kovacs, Portable cell-based biosensor system using integrated CMOS cell-cartridges. Biosens. Bioelectron. 16 (2001). 26. A. Scott, K. Weir, C. Easton, W. Huynh, W. J. Moody, and A. Folch, A microfluidic microelectrode array for simultaneous electrophysiology, chemical stimulation, and imaging of brain slices. Lab on a Chip 13, 4 (2013). 27. J. Ericksona, A. Tookerb, Y. Tai, and J. Pine, Caged neuron MEA: A system for long-term investigation of cultured neural network connectivity. Journal of Neuroscience Methods 175 (2008). 28. J. M. Peyrin, B. Deleglise, L. Saias, M. Vignes, P. Gougis, S. Magnifico, and B. Brugg, Axon diodes for the reconstruction of oriented neuronal networks in microfluidic chambers. Lab on a Chip 11, 21 (2011). 29. A. Charrier, D. Martinez, R. Monette, T. Comas, R. Movileanu, C. Py, M. Denhoff, A. Krantis, and G. Mealing, Cell placement and guidance on substrates for neurochip interfaces. Biotechnol. Bioeng. 105, 2 (2010). 30. A. Kundu, L. Micholt, S. Friedrich, D. R. Rand, C. Bartic, D. Braeken, and A. Levchenko, Superimposed topographic and chemical cues synergistically guide neurite outgrowth. Lab on a Chip 13, 15 (2013). 31. A. Kunze, M. Giugliano, A. Valero, and P. Renaud, Micropatterning neural cell cultures in 3D with a multi-layered scaffold. Biomaterials 32, 8 (2011). 32. L. M. Griep, F. Wolbers, B. de Wagenaar, P. M. ter Braak, B. B. Weksler, I. A. Romero, P. O. Couraud, I. Vermes, A. D. van der Meer, and A. van den Berg, BBB ON CHIP: Microfluidic platform to
Tang et al.
33.
34.
35.
36.
37.
38.
39.
40.
41.
42.
mechanically and biochemically modulate blood-brain barrier function. Biomed. Microdevices 15, 1 (2013). K. Musick, D. Khatami, and B. C. Wheeler, Three-dimensional micro-electrode array for recording dissociated neuronal cultures. Lab on a Chip 9, 14 (2009) F. Bianco, N. Tonna, R. D. Lovchik, R. Mastrangelo, R. Morini, A. Ruiz, and M. Matteoli, Overflow microfluidic networks: Application to the biochemical analysis of brain cell interactions in complex neuroinflammatory scenarios. Anal. Chem. 84, 22 (2012). L. Li, L. Ren, W. Liu, J. C. Wang, Y. Wang, Q. Tu, and J. Wang, Spatiotemporally controlled and multifactor involved assay of neuronal compartment regeneration after chemical injury in an integrated microfluidics. Anal. Chem. 84, 15 (2012). M. C. Chuang, H. Y. Lai, J. A. Ho, and Y. Y. Chen, Multifunctional microelectrode array (mMEA) chip for neural-electrical and neuralchemical interfaces: Characterization of comb interdigitated electrode towards dopamine detection. Biosens. Bioelectron. 41 (2013). Y. Song, N. Lin, C. Liu, H. Jiang, G. Xing, and X. Cai, A novel dual mode microelectrode array for neuroelectrical and neurochemical recording in vitro. Biosens. Bioelectron. 38, 1 (2012). T. T. Kanagasabapathi, D. Ciliberti, S. Martinoia, W. J. Wadman, and M. M. J. Decré, Dual-compartment neurofluidic system for electrophysiological measurements in physically segregated and functionally connected neuronal cell culture. Frontiers in Neuroengineering 4 (2011). J. Park, H. Koito, J. Li, and A. Han, Microfluidic compartmentalized co-culture platform for CNS axon myelination research. Biomed. Microdevices 11, 6 (2009). B. G. Chung, L. A. Flanagan, S. W. Rhee, P. H. Schwartz, A. P. Lee, E. S. Monuki, and N. L. Jeon, Human neural stem cell growth and differentiation in a gradient-generating microfluidic device. Lab on a Chip 5, 4 (2005). K. Saha, A. J. Keung, E. F. Irwin, Y. Li, L. Little, D. V. Schaffer, and K. E. Healy, Substrate modulus directs neural stem cell behavior. Biophys. J. 95, 9 (2008). A. J. Keung, P. Asuri, S. Kumar, and D. V. Schaffer, Soft microenvironments promote the early neurogenic differentiation but not selfrenewal of human pluripotent stem cells. Integr. Biol. 4 (2012).
Received: xx Xxxx xxxx. Accepted: xx Xxxx xxxx.
8
J. Biomater. Tissue Eng. 4, 1–8, 2014
