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1.
Biomaterials ; 33(7): 1982-90, 2012 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-22182748

RESUMO

Cochlear implants provide hearing by electrically stimulating the auditory nerve. Implant function can be hindered by device design variables, including electrode size and electrode-to-nerve distance, and cochlear environment variables, including the degeneration of the auditory nerve following hair cell loss. We have developed a dual-component cochlear implant coating to improve both the electrical function of the implant and the biological stability of the inner ear, thereby facilitating the long-term perception of sound through a cochlear implant. This coating is a combination of an arginine-glycine-aspartic acid (RGD)-functionalized alginate hydrogel and the conducting polymer poly(3, 4-ethylenedioxythiophene) (PEDOT). Both in vitro and in vivo assays on the effects of these electrode coatings demonstrated improvements in device performance. We found that the coating reduced electrode impedance, improved charge delivery, and locally released significant levels of a trophic factor into cochlear fluids. This coating is non-cytotoxic, clinically relevant, and has the potential to significantly improve the cochlear implant user's experience.


Assuntos
Alginatos/química , Compostos Bicíclicos Heterocíclicos com Pontes/química , Implantes Cocleares , Sistemas de Liberação de Medicamentos , Hidrogéis/química , Oligopeptídeos/química , Polímeros/química , Alginatos/metabolismo , Animais , Fator Neurotrófico Derivado do Encéfalo/química , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Compostos Bicíclicos Heterocíclicos com Pontes/metabolismo , Materiais Revestidos Biocompatíveis/química , Materiais Revestidos Biocompatíveis/metabolismo , Implante Coclear , Nervo Coclear/fisiologia , Nervo Coclear/cirurgia , Surdez/reabilitação , Surdez/cirurgia , Eletroquímica , Eletrodos , Ácido Glucurônico/química , Ácido Glucurônico/metabolismo , Cobaias , Ácidos Hexurônicos/química , Ácidos Hexurônicos/metabolismo , Humanos , Hidrogéis/metabolismo , Masculino , Teste de Materiais , Oligopeptídeos/metabolismo , Polímeros/metabolismo , Propriedades de Superfície
2.
Nanotechnology ; 23(1): 015304, 2012 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-22155970

RESUMO

A simple approach for creating periodic nano-cavities and periodic stripes of nano-cavity arrays on poly (3,4-ethylene dioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) thin films using a combination of optical near-field enhancement through self-assembled silica nanospheres and laser interference lithography is presented. Monolayers of close-packed silica nanospheres (800, 600, and 430 nm in diameter) are self-assembled on 2 µm thick PEDOT-PSS electropolymerized films and are subsequently irradiated with 10 ns pulses of 355 nm wavelength laser light. Over areas spanning 2 cm(2), circular nano-cavities with central holes of size 50-200 nm and surrounding craters of size 100-400 nm are formed in the PEDOT-PSS films directly underneath the nanospheres due to strong enhancement (11-18 fold) of the incident light in the near-field, which is confirmed through Mie scattering theory. Predictions from theoretical simulations examining the combined effects of near-field enhancement and interference are in good agreement with the experimental results. The results illustrate the versatility of the described technique for creating nano-cavity arrays or nano-pores in PEDOT-PSS over large areas with designed periodicity and hole size.

3.
J Neural Eng ; 8(1): 014001, 2011 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-21245527

RESUMO

We investigated using poly(3,4-ethylenedioxythiophene) (PEDOT) to lower the impedance of small, gold recording electrodes with initial impedances outside of the effective recording range. Smaller electrode sites enable more densely packed arrays, increasing the number of input and output channels to and from the brain. Moreover, smaller electrode sizes promote smaller probe designs; decreasing the dimensions of the implanted probe has been demonstrated to decrease the inherent immune response, a known contributor to the failure of long-term implants. As expected, chronically implanted control electrodes were unable to record well-isolated unit activity, primarily as a result of a dramatically increased noise floor. Conversely, electrodes coated with PEDOT consistently recorded high-quality neural activity, and exhibited a much lower noise floor than controls. These results demonstrate that PEDOT coatings enable electrode designs 15 µm in diameter.


Assuntos
Compostos Bicíclicos Heterocíclicos com Pontes/química , Microeletrodos , Neurônios/fisiologia , Polímeros/química , Animais , Materiais Biocompatíveis/química , Materiais Biocompatíveis/normas , Eletrodos Implantados/normas , Masculino , Microeletrodos/normas , Córtex Motor/fisiologia , Ratos , Ratos Sprague-Dawley
4.
Nano Lett ; 9(12): 4012-8, 2009 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-19785391

RESUMO

The safety, function, and longevity of implantable neuroprosthetic and cardiostimulating electrodes depend heavily on the electrical properties of the electrode-tissue interface, which in many cases requires substantial improvement. While different variations of carbon nanotube materials have been shown to be suitable for neural excitation, it is critical to evaluate them versus other materials used for bioelectrical interfacing, which have not been done in any study performed so far despite strong interest to this area. In this study, we carried out this evaluation and found that composite multiwalled carbon nanotube-polyelectrolyte (MWNT-PE) multilayer electrodes substantially outperform in one way or the other state-of-the-art neural interface materials available today, namely activated electrochemically deposited iridium oxide (IrOx) and poly(3,4-ethylenedioxythiophene) (PEDOT). Our findings provide the concrete experimental proof to the much discussed possibility that carbon nanotube composites can serve as excellent new material for neural interfacing with a strong possibility to lead to a new generation of implantable electrodes.


Assuntos
Potenciais de Ação/fisiologia , Eletrólitos/química , Microeletrodos , Nanotecnologia/instrumentação , Nanotubos de Carbono/química , Nanotubos de Carbono/ultraestrutura , Neurônios/fisiologia , Cristalização/métodos , Condutividade Elétrica , Desenho de Equipamento , Análise de Falha de Equipamento , Substâncias Macromoleculares/química , Teste de Materiais , Conformação Molecular , Tamanho da Partícula , Propriedades de Superfície
5.
Front Neuroeng ; 2: 7, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-19543541

RESUMO

Chronic microstimulation-based devices are being investigated to treat conditions such as blindness, deafness, pain, paralysis, and epilepsy. Small-area electrodes are desired to achieve high selectivity. However, a major trade-off with electrode miniaturization is an increase in impedance and charge density requirements. Thus, the development of novel materials with lower interfacial impedance and enhanced charge storage capacity is essential for the development of micro-neural interface-based neuroprostheses. In this report, we study the use of conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) as a neural interface material for microstimulation of small-area iridium electrodes on silicon-substrate arrays. Characterized by electrochemical impedance spectroscopy, electrodeposition of PEDOT results in lower interfacial impedance at physiologically relevant frequencies, with the 1 kHz impedance magnitude being 23.3 +/- 0.7 kOmega, compared to 113.6 +/- 3.5 kOmega for iridium oxide (IrOx) on 177 mum(2) sites. Further, PEDOT exhibits enhanced charge storage capacity at 75.6 +/- 5.4 mC/cm(2) compared to 28.8 +/- 0.3 mC/cm(2) for IrOx, characterized by cyclic voltammetry (50 mV/s). These improvements at the electrode interface were corroborated by observation of the voltage excursions that result from constant current pulsing. The PEDOT coatings provide both a lower amplitude voltage and a more ohmic representation of the applied current compared to IrOx. During repetitive pulsing, PEDOT-coated electrodes show stable performance and little change in electrical properties, even at relatively high current densities which cause IrOx instability. These findings support the potential of PEDOT coatings as a micro-neural interface material for electrostimulation.

6.
Hear Res ; 242(1-2): 117-31, 2008 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-18573323

RESUMO

Localized cell and drug delivery to the cochlea and central auditory pathway can improve the safety and performance of implanted auditory prostheses (APs). While generally successful, these devices have a number of limitations and adverse effects including limited tonal and dynamic ranges, channel interactions, unwanted stimulation of non-auditory nerves, immune rejection, and infections including meningitis. Many of these limitations are associated with the tissue reactions to implanted auditory prosthetic devices and the gradual degeneration of the auditory system following deafness. Strategies to reduce the insertion trauma, degeneration of target neurons, fibrous and bony tissue encapsulation, and immune activation can improve the viability of tissue required for AP function as well as improve the resolution of stimulation for reduced channel interaction and improved place-pitch and level discrimination. Many pharmaceutical compounds have been identified that promote the viability of auditory tissue and prevent inflammation and infection. Cell delivery and gene therapy have provided promising results for treating hearing loss and reversing degeneration. Currently, many clinical and experimental methods can produce extremely localized and sustained drug delivery to address AP limitations. These methods provide better control over drug concentrations while eliminating the adverse effects of systemic delivery. Many of these drug delivery techniques can be integrated into modern auditory prosthetic devices to optimize the tissue response to the implanted device and reduce the risk of infection or rejection. Together, these methods and pharmaceutical agents can be used to optimize the tissue-device interface for improved AP safety and effectiveness.


Assuntos
Transplante de Células/métodos , Implantes Cocleares/tendências , Bombas de Infusão Implantáveis , Fatores de Crescimento Neural/farmacologia , Animais , Vias Auditivas/efeitos dos fármacos , Vias Auditivas/fisiologia , Gatos , Transplante de Células/instrumentação , Cóclea/efeitos dos fármacos , Cóclea/fisiologia , Surdez/fisiopatologia , Surdez/terapia , Terapia Genética , Cobaias , Humanos , Modelos Animais , Fatores de Crescimento Neural/administração & dosagem
7.
J Neural Eng ; 4(2): L6-L13, 2007 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-17409471

RESUMO

A number of biomedical devices require extended electrical communication with surrounding tissue. Significant improvements in device performance would be achieved if it were possible to maintain communication with target cells despite the reactive, insulating scar tissue that forms at the device-tissue interface. Here, we report that the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) can be polymerized directly within living neural tissue resulting in an electrically conductive network that is integrated within the tissue. Nano and microscale PEDOT filaments extend out from electrode sites, presumably forming within extracellular spaces. The cloud of PEDOT filaments penetrates out into the tissue far enough that it should be possible to bypass fibrous scar tissue and contact surrounding healthy neurons. These electrically functional, diffuse conducting polymer networks grown directly within tissue signify a new paradigm for creating soft, low impedance implantable electrodes.


Assuntos
Materiais Biocompatíveis/química , Materiais Biocompatíveis/efeitos da radiação , Encéfalo/citologia , Encéfalo/fisiologia , Compostos Bicíclicos Heterocíclicos com Pontes/química , Eletroquímica/instrumentação , Eletroquímica/métodos , Eletrodos Implantados , Polímeros/química , Animais , Compostos Bicíclicos Heterocíclicos com Pontes/efeitos da radiação , Impedância Elétrica , Campos Eletromagnéticos , Desenho de Equipamento , Análise de Falha de Equipamento , Humanos , Polímeros/efeitos da radiação
8.
Biomaterials ; 28(8): 1539-52, 2007 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-17169420

RESUMO

In this paper, we describe interactions between neural cells and the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) toward development of electrically conductive biomaterials intended for direct, functional contact with electrically active tissues such as the nervous system, heart, and skeletal muscle. We introduce a process for polymerizing PEDOT around living cells and describe a neural cell-templated conducting polymer coating for microelectrodes and a hybrid conducting polymer-live neural cell electrode. We found that neural cells could be exposed to working concentrations (0.01 m) of the EDOT monomer for as long as 72 h while maintaining 80% cell viability. PEDOT could be electrochemically deposited around neurons cultured on electrodes using 0.5-1 microA/mm(2) galvanostatic current. PEDOT polymerized on the electrode and surrounded the cells, covering cell processes. The polymerization was impeded in regions where cells were well adhered to the substrate. The cells could be removed from the PEDOT matrix to generate a neural cell-templated biomimetic conductive substrate with cell-shaped features that were cell attracting. Live cells embedded within the conductive polymer matrix remained viable for at least 120 h following polymerization. Dying cells primarily underwent apoptotic cell death. PEDOT, PEDOT+live neurons, and neuron-templated PEDOT coatings on electrodes significantly enhanced the electrical properties as compared to the bare electrode as indicated by decreased electrical impedance of 1-1.5 orders of magnitude at 0.01-1 kHz and significantly increased charge transfer capacity. PEDOT coatings showed a decrease of the phase angle of the impedance from roughly 80 degrees for the bare electrode to 5-35 degrees at frequencies >0.1 kHz. Equivalent circuit modeling indicated that PEDOT-coated electrodes were best described by R(C(RT)) circuit. We found that an RC parallel circuit must be added to the model for PEDOT+live neuron and neuron-templated PEDOT coatings.


Assuntos
Materiais Biocompatíveis/síntese química , Compostos Bicíclicos Heterocíclicos com Pontes/síntese química , Neurônios , Polímeros/síntese química , Animais , Compostos Bicíclicos Heterocíclicos com Pontes/toxicidade , Linhagem Celular Tumoral , Camundongos , Polímeros/toxicidade
9.
Acta Biomater ; 1(1): 125-36, 2005 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-16701786

RESUMO

Ordered conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) was electrochemically fabricated using a self-assembled medium of surfactant molecules as a template. The morphology and microstructure were extensively investigated by optical and electron microscopy, and results show that the coated films were composed of anisotropic domains having a characteristic size of 15-150 nm. The surfactant-templated ordered PEDOT films were electrochemically deposited on microfabricated neural probes with an electrode site area of 1,256 microm(2). The electrical properties were studied by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). EIS showed a lowered magnitude of 35 kOmega (from an initial approximately 800 kOmega) at the biologically relevant frequency of 1 kHz. CV results show that the film has higher charge capacity and is more electrochemically stable than either nodular PEDOT or PPy. Furthermore, we have begun to probe the biological response to such a material intended to define the tissue-material interface. Results show that minute concentrations of the non-ionic surfactant are enough to kill all nearby cells in culture. It is possible however, to create surfactant-templated ordered PEDOT such that SH-SY5Y survive on the conductive polymer.


Assuntos
Materiais Biocompatíveis/química , Compostos Bicíclicos Heterocíclicos com Pontes/química , Polímeros/química , Adesão Celular , Linhagem Celular , Materiais Revestidos Biocompatíveis/química , Eletroquímica , Humanos , Teste de Materiais , Microeletrodos , Microscopia Eletrônica , Neurônios/citologia , Desenho de Prótese , Propriedades de Superfície , Tensoativos/química
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