Imperial College London

DrRylieGreen

Faculty of EngineeringDepartment of Bioengineering

Reader in Polymer Bioelectronics
 
 
 
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Contact

 

+44 (0)20 7594 0943rylie.green

 
 
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2.06Bessemer BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
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76 results found

Shi A, Shemesh J, Asadnia M, Robles UA, Green R, Yeoh GH, Warkiani MEet al., 2015, A novel microfluidic patterning device for neuron-glia co-culture, Pages: 633-635

� 15CBMS-0001. Many biological processes in the body are regulated by synchronized activity between two cell types. To study cell-cell interactions, it is necessary to develop easy to use co-culture systems, where different cell types can be cultured within the same confined space. Designing a complete 3D biomimetic system to study these interactions in vitro requires complex protocols and use of non-conventional materials such as hydrogels. This paper reports development of a temporarily sealed microfluidic device which utilizes a novel valve design to directly and accurately co-culture two cell lines in alternating rows, allowing them to proliferate towards each other and then observe their interaction at the boundaries of their interface.

CONFERENCE PAPER

Aregueta-Robles UA, Lim KS, Martens PJ, Lovell NH, Poole-Warren LA, Green Ret al., 2015, Producing 3D Neuronal Networks in Hydrogels for Living Bionic Device Interfaces, 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), Publisher: IEEE, Pages: 2600-2603, ISSN: 1557-170X

CONFERENCE PAPER

Gilmour AD, Goding J, Poole-Warren LA, Thomson CE, Green RAet al., 2015, In vitro biological assessment of electrode materials for neural interfaces, Pages: 450-453, ISSN: 1948-3546

© 2015 IEEE. The development of the next generation electrode interfaces for neural prosthetic devices requires high-through-put multifaceted testing strategies to assess material interactions with both peripheral and central nervous system (CNS) immune cells. The utility of a primary astrocyte enriched glial cell culture was assessed as a potential in vitro tool for understanding the immune response to electrode materials. Conductive polymer consisting of electropolymerized poly(3,4-ethylenedioxythiophene) (PEDOT) doped with paratoluene sulfonate (pTS) was used as a novel electrode material and compared to the conventional electrode material, platinum (Pt). Morphology of astrocytes and microglia in contact with the materials was analyzed and compared to an immunoassay of TNFα release from human blood plasma. While all electrode materials failed to stimulate TNFα release from human leukocytes, the materials in contact with glial cells resulted in progressive reactive gliosis. This primary astrocyte in vitro assay provides insight into the degeneration of electrode performance in vivo as a result of scar tissue reactions in chronic implant devices. It also highlights the relevance of testing for immune reactions with an appropriate cell system.

CONFERENCE PAPER

Patton AJ, Green RA, Poole-Warren LA, 2015, Mediating conducting polymer growth within hydrogels by controlling nucleation, APL Materials, Vol: 3, Pages: 014912-014912

JOURNAL ARTICLE

Green RA, Matteucci PB, Dodds CWD, Palmer J, Dueck WF, Hassarati RT, Byrnes-Preston PJ, Lovell NH, Suaning GJet al., 2014, Laser patterning of platinum electrodes for safe neurostimulation., J Neural Eng, Vol: 11

OBJECTIVE: Laser surface modification of platinum (Pt) electrodes was investigated for use in neuroprosthetics. Surface modification was applied to increase the surface area of the electrode and improve its ability to transfer charge within safe electrochemical stimulation limits. APPROACH: Electrode arrays were laser micromachined to produce Pt electrodes with smooth surfaces, which were then modified with four laser patterning techniques to produce surface structures which were nanosecond patterned, square profile, triangular profile and roughened on the micron scale through structured laser interference patterning (SLIP). Improvements in charge transfer were shown through electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and biphasic stimulation at clinically relevant levels. A new method was investigated and validated which enabled the assessment of in vivo electrochemically safe charge injection limits. MAIN RESULTS: All of the modified surfaces provided electrical advantage over the smooth Pt. The SLIP surface provided the greatest benefit both in vitro and in vivo, and this surface was the only type which had injection limits above the threshold for neural stimulation, at a level shown to produce a response in the feline visual cortex when using an electrode array implanted in the suprachoroidal space of the eye. This surface was found to be stable when stimulated with more than 150 million clinically relevant pulses in physiological saline. SIGNIFICANCE: Critical to the assessment of implant devices is accurate determination of safe usage limits in an in vivo environment. Laser patterning, in particular SLIP, is a superior technique for improving the performance of implant electrodes without altering the interfacial electrode chemistry through coating. Future work will require chronic in vivo assessment of these electrode patterns.

JOURNAL ARTICLE

Baek S, Green RA, Poole-Warren LA, 2014, Effects of dopants on the biomechanical properties of conducting polymer films on platinum electrodes, JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A, Vol: 102, Pages: 2743-2754, ISSN: 1549-3296

JOURNAL ARTICLE

Baek S, Green RA, Poole-Warren LA, 2014, The biological and electrical trade-offs related to the thickness of conducting polymers for neural applications, ACTA BIOMATERIALIA, Vol: 10, Pages: 3048-3058, ISSN: 1742-7061

JOURNAL ARTICLE

Hassarati RT, Goding JA, Baek S, Patton AJ, Poole-Warren LA, Green RAet al., 2014, Stiffness Quantification of Conductive Polymers for Bioelectrodes, JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS, Vol: 52, Pages: 666-675, ISSN: 0887-6266

JOURNAL ARTICLE

Cheong GLM, Lim KS, Jakubowicz A, Martens PJ, Poole-Warren LA, Green RAet al., 2014, Conductive hydrogels with tailored bioactivity for implantable electrode coatings, ACTA BIOMATERIALIA, Vol: 10, Pages: 1216-1226, ISSN: 1742-7061

JOURNAL ARTICLE

Hassarati RT, Dueck WF, Tasche C, Carter PM, Poole-Warren LA, Green RAet al., 2014, Improving Cochlear Implant Properties Through Conductive Hydrogel Coatings, IEEE TRANSACTIONS ON NEURAL SYSTEMS AND REHABILITATION ENGINEERING, Vol: 22, Pages: 411-418, ISSN: 1534-4320

JOURNAL ARTICLE

Aregueta-Robles UA, Woolley AJ, Poole-Warren LA, Lovell NH, Green RAet al., 2014, Organic electrode coatings for next-generation neural interfaces., Front Neuroeng, Vol: 7, ISSN: 1662-6443

Traditional neuronal interfaces utilize metallic electrodes which in recent years have reached a plateau in terms of the ability to provide safe stimulation at high resolution or rather with high densities of microelectrodes with improved spatial selectivity. To achieve higher resolution it has become clear that reducing the size of electrodes is required to enable higher electrode counts from the implant device. The limitations of interfacing electrodes including low charge injection limits, mechanical mismatch and foreign body response can be addressed through the use of organic electrode coatings which typically provide a softer, more roughened surface to enable both improved charge transfer and lower mechanical mismatch with neural tissue. Coating electrodes with conductive polymers or carbon nanotubes offers a substantial increase in charge transfer area compared to conventional platinum electrodes. These organic conductors provide safe electrical stimulation of tissue while avoiding undesirable chemical reactions and cell damage. However, the mechanical properties of conductive polymers are not ideal, as they are quite brittle. Hydrogel polymers present a versatile coating option for electrodes as they can be chemically modified to provide a soft and conductive scaffold. However, the in vivo chronic inflammatory response of these conductive hydrogels remains unknown. A more recent approach proposes tissue engineering the electrode interface through the use of encapsulated neurons within hydrogel coatings. This approach may provide a method for activating tissue at the cellular scale, however, several technological challenges must be addressed to demonstrate feasibility of this innovative idea. The review focuses on the various organic coatings which have been investigated to improve neural interface electrodes.

JOURNAL ARTICLE

Green RA, Guenther T, Jeschke C, Jaillon A, Yu JF, Dueck WF, Lim WW, Henderson WC, Vanhoestenberghe A, Lovell NH, Suaning GJet al., 2013, Integrated electrode and high density feedthrough system for chip-scale implantable devices, BIOMATERIALS, Vol: 34, Pages: 6109-6118, ISSN: 0142-9612

JOURNAL ARTICLE

Gilmour AD, Green RA, Thomson CE, 2013, A low-maintenance, primary cell culture model for the assessment of carbon nanotube toxicity, TOXICOLOGICAL AND ENVIRONMENTAL CHEMISTRY, Vol: 95, Pages: 1129-1144, ISSN: 0277-2248

JOURNAL ARTICLE

Green RA, Matteucci PB, Hassarati RT, Giraud B, Dodds CWD, Chen S, Byrnes-Preston PJ, Suaning GJ, Poole-Warren LA, Lovell NHet al., 2013, Performance of conducting polymer electrodes for stimulating neuroprosthetics., J Neural Eng, Vol: 10

OBJECTIVE: Recent interest in the use of conducting polymers (CPs) for neural stimulation electrodes has been growing; however, concerns remain regarding the stability of coatings under stimulation conditions. These studies examine the factors of the CP and implant environment that affect coating stability. The CP poly(ethylene dioxythiophene) (PEDOT) is examined in comparison to platinum (Pt), to demonstrate the potential performance of these coatings in neuroprosthetic applications. APPROACH: PEDOT is coated on Pt microelectrode arrays and assessed in vitro for charge injection limit and long-term stability under stimulation in biologically relevant electrolytes. Physical and electrical stability of coatings following ethylene oxide (ETO) sterilization is established and efficacy of PEDOT as a visual prosthesis bioelectrode is assessed in the feline model. MAIN RESULTS: It was demonstrated that PEDOT reduced the potential excursion at a Pt electrode interface by 72% in biologically relevant solutions. The charge injection limit of PEDOT for material stability was found to be on average 30× larger than Pt when tested in physiological saline and 20× larger than Pt when tested in protein supplemented media. Additionally stability of the coating was confirmed electrically and morphologically following ETO processing. It was demonstrated that PEDOT-coated electrodes had lower potential excursions in vivo and electrically evoked potentials (EEPs) could be detected within the visual cortex. SIGNIFICANCE: These studies demonstrate that PEDOT can be produced as a stable electrode coating which can be sterilized and perform effectively and safely in neuroprosthetic applications. Furthermore these findings address the necessity for characterizing in vitro properties of electrodes in biologically relevant milieu which mimic the in vivo environment more closely.

JOURNAL ARTICLE

Green RA, Lim KS, Henderson WC, Hassarati RT, Martens PJ, Lovell NH, Poole-Warren LAet al., 2013, Living electrodes: tissue engineering the neural interface, Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, Vol: 2013, Pages: 6957-6960, ISSN: 1557-170X

Soft, cell integrated electrode coatings are proposed to address the problem of scar tissue encapsulation of stimulating neuroprosthetics. The aim of these studies was to prove the concept and feasibility of integrating a cell loaded hydrogel with existing electrode coating technologies. Layered conductive hydrogel constructs are embedded with neural cells and shown to both support cell growth and maintain electro activity. The safe charge injection limit of these electrodes was 8 times higher than conventional platinum (Pt) electrodes and the stiffness was four orders of magnitude lower than Pt. Future studies will determine the biological cues required to support stem cell differentiation from the electrode surface.

JOURNAL ARTICLE

Baek S, Green R, Granville A, Martens P, Poole-Warren Let al., 2013, Thin film hydrophilic electroactive polymer coatings for bioelectrodes (vol 1, pg 3803, 2013), JOURNAL OF MATERIALS CHEMISTRY B, Vol: 1, Pages: 6670-6670, ISSN: 2050-7518

JOURNAL ARTICLE

Green RA, Lim KS, Henderson WC, Hassarati RT, Martens PJ, Lovell NH, Poole-Warren LAet al., 2013, Living Electrodes: Tissue Engineering the Neural Interface, 35th Annual International Conference of the IEEE-Engineering-in-Medicine-and-Biology-Society (EMBC), Publisher: IEEE, Pages: 6957-6960, ISSN: 1557-170X

CONFERENCE PAPER

Baek S, Green R, Granville A, Martens P, Poole-Warren Let al., 2013, Thin film hydrophilic electroactive polymer coatings for bioelectrodes, JOURNAL OF MATERIALS CHEMISTRY B, Vol: 1, Pages: 3803-3810, ISSN: 2050-750X

JOURNAL ARTICLE

, 2013, Back matter, Journal of Materials Chemistry B, Vol: 1, Pages: 6670-6670, ISSN: 2050-750X

JOURNAL ARTICLE

Green RA, Hassarati RT, Bouchinet L, Lee CS, Cheong GLM, Yu JF, Dodds CW, Suaning GJ, Poole-Warren LA, Lovell NHet al., 2012, Substrate dependent stability of conducting polymer coatings on medical electrodes, BIOMATERIALS, Vol: 33, Pages: 5875-5886, ISSN: 0142-9612

JOURNAL ARTICLE

Green RA, Hassarati RT, Goding JA, Baek S, Lovell NH, Martens PJ, Poole-Warren LAet al., 2012, Conductive Hydrogels: Mechanically Robust Hybrids for Use as Biomaterials, MACROMOLECULAR BIOSCIENCE, Vol: 12, Pages: 494-501, ISSN: 1616-5187

JOURNAL ARTICLE

Poole-Warren L, Goding J, 2012, Challenges of therapeutic delivery using conducting polymers., Ther Deliv, Vol: 3, Pages: 421-427, ISSN: 2041-5990

JOURNAL ARTICLE

Green RA, Hassarati RT, Goding JA, Baek S, Lovell NH, Martens PJ, Poole-Warren LAet al., 2012, Macromol. Biosci. 4/2012, Macromolecular Bioscience, Vol: 12, Pages: n/a-n/a, ISSN: 1616-5187

JOURNAL ARTICLE

Green RA, Toor H, Dodds C, Lovell NHet al., 2012, Variation in performance of platinum electrodes with size and surface roughness, Sensors and Materials, Vol: 24, Pages: 165-180, ISSN: 0914-4935

JOURNAL ARTICLE

Green R, Duan C, Hassarati R, Goding J, Byrnes-Preston P, Suaning GJ, Poole-Warren L, Lovell NHet al., 2011, Electrochemical stability of poly(ethylene dioxythiophene) electrodes, Pages: 566-569

The conducting polymer poly(ethylene dioxythiopene) (PEDOT) has been investigated as a coating for visual prosthesis electrode arrays. The prototype electrode array was coated with PEDOT doped with two conventional anions: paratoluene sulfonate (pTS) and lithium perchlorate (LiClO4). PEDOT variants were analyzed for charge injection limit, electrochemical stability following continuous biphasic stimulation, accelerated ageing and steam sterilization conditions. It was found that PEDOT/LiClO4 was the most stable conducting polymer under chronic stimulation and high temperature circumstances. However, PEDOT/pTS exhibited acceptable stability in comparison to conventional platinum. © 2011 IEEE.

CONFERENCE PAPER

Ouyang L, Green R, Feldman KE, Martin DCet al., 2011, Direct local polymerization of poly(3,4-ethylenedioxythiophene) in rat cortex, BRAIN MACHINE INTERFACES: IMPLICATIONS FOR SCIENCE, CLINICAL PRACTICE AND SOCIETY, Vol: 194, Pages: 263-271, ISSN: 0079-6123

JOURNAL ARTICLE

Green RA, Ordonez JS, Schuettler M, Poole-Warren LA, Lovell NH, Suaning GJet al., 2010, Cytotoxicity of implantable microelectrode arrays produced by laser micromachining, BIOMATERIALS, Vol: 31, Pages: 886-893, ISSN: 0142-9612

JOURNAL ARTICLE

Green RA, Baek S, Poole-Warren LA, Martens PJet al., 2010, Conducting polymer-hydrogels for medical electrode applications, SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS, Vol: 11, ISSN: 1468-6996

JOURNAL ARTICLE

Green RA, Baek S, Poole-Warren LA, Martens PJet al., 2010, Conducting polymer-hydrogels for medical electrode applications., Sci Technol Adv Mater, Vol: 11, ISSN: 1468-6996

Conducting polymers hold significant promise as electrode coatings; however, they are characterized by inherently poor mechanical properties. Blending or producing layered conducting polymers with other polymer forms, such as hydrogels, has been proposed as an approach to improving these properties. There are many challenges to producing hybrid polymers incorporating conducting polymers and hydrogels, including the fabrication of structures based on two such dissimilar materials and evaluation of the properties of the resulting structures. Although both fabrication and evaluation of structure-property relationships remain challenges, materials comprised of conducting polymers and hydrogels are promising for the next generation of bioactive electrode coatings.

JOURNAL ARTICLE

Green RA, Lovell NH, Poole-Warren LA, 2010, Impact of co-incorporating laminin peptide dopants and neurotrophic growth factors on conducting polymer properties, ACTA BIOMATERIALIA, Vol: 6, Pages: 63-71, ISSN: 1742-7061

JOURNAL ARTICLE

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