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<div class="block title" style="margin-top: 35px;"><h3 style="text-align: left;" id="Gold">Gold-coated membranes</h3></div> | <div class="block title" style="margin-top: 35px;"><h3 style="text-align: left;" id="Gold">Gold-coated membranes</h3></div> | ||
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− | <p>Sterlitech Polycarbonate Gold-Coated Membrane Filters | + | <p>Sterlitech Polycarbonate Gold-Coated Membrane Filters represented one of the types of membranes we tested. The pores have a diameter of 0.4 micrometer, which is small enough to confine <i> Escherichia coli </i> bacteria, which diameter and size are respectively about 1 micrometer and 2 micrometers. These membranes were relatively easy to manipulate with a forceps because of their high flexibility. Scanning electron microscopy by courtesy of Bruno Bresson, Sciences et Ingénierie de la Matière Molle |
+ | Physico-chimie des Polymères et Milieux Dispersés).</p> | ||
</div> | </div> | ||
<div class="block half"> | <div class="block half"> | ||
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<img src="https://static.igem.org/mediawiki/2018/1/15/T--Pasteur_Paris--Gold-membrane-micro.jpg"> | <img src="https://static.igem.org/mediawiki/2018/1/15/T--Pasteur_Paris--Gold-membrane-micro.jpg"> | ||
− | <div class="legend"><b>Figure 3: </b>Gold-Coated Membrane | + | <div class="legend"><b>Figure 3: </b>Gold-Coated Membrane </div> |
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<img src="https://static.igem.org/mediawiki/2018/8/83/T--Pasteur_Paris--Alumina-oxide-membrane.jpg"> | <img src="https://static.igem.org/mediawiki/2018/8/83/T--Pasteur_Paris--Alumina-oxide-membrane.jpg"> | ||
− | <div class="legend"><b>Figure 4: </b> | + | <div class="legend"><b>Figure 4: </b>Alumina Oxyde Membrane in grey</div> |
</div> | </div> | ||
<div class="block half"> | <div class="block half"> | ||
<img src="https://static.igem.org/mediawiki/2018/f/f7/T--Pasteur_Paris--Alumina-oxide-membrane-micro.jpg"> | <img src="https://static.igem.org/mediawiki/2018/f/f7/T--Pasteur_Paris--Alumina-oxide-membrane-micro.jpg"> | ||
− | <div class="legend"><b>Figure 5: </b> | + | <div class="legend"><b>Figure 5: </b>Alumina Oxyde Membrane (electron microscope)</div> |
</div> | </div> | ||
<div class="block full"> | <div class="block full"> | ||
− | <p>For PEDOT:PSS, an aqueous solution of PEDOT:PSS was prepared<sup>[1]</sup> and alumina oxide membranes were dipped for 24 hours in this solution. Electron microscopy of the membranes before and after the experiment showed the deposit of a substance on their surface | + | <p>For PEDOT:PSS, an aqueous solution of PEDOT:PSS was prepared<sup>[1]</sup> and alumina oxide membranes were dipped for 24 hours in this solution. Electron microscopy of the membranes before and after the experiment showed the deposit of a substance on their surface in a cluster-like fashion, indicating an incomplete coating.</p> |
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− | <p>Vapor-phase polymerization of PEDOT:Cl and PEDOT:Ts<sup>[2]</sup> also induced a change in the surface of the membranes | + | <p>Vapor-phase polymerization of PEDOT:Cl and PEDOT:Ts<sup>[2]</sup> also induced a change in the surface of the membranes, in a more uniform way. The surface of the membrane seems to have thickened, but without blocking the pores either, which makes for a high quality homogenous coating.</p> |
</div> | </div> | ||
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+ | <div class="block title"><h3 style="text-align: left;" id="Confinement">Confinement</h3></div> | ||
+ | <div class="block full"> | ||
+ | <p>The first issue to tackle was the confinement of the bacteria. For this purpose, we used microfluidic chips. Microfluidic chips are patterns molded in PDMS (polydimethylsiloxane), which can be used to design tiny circuits for liquid flow. We used Institut Curie's design of a microfluidic chip, which has 2 chambers connected by microchannels of 5 micrometers width and 2 micrometers height. We enhanced the design by integrating a membrane filter (gold-coated) to prevent bacteria to pass from one chamber to another. As this technique was quite improvised and new, we didn't had access to the needed equipement for better precision work, leading to many chips being leaky. We managed to conduct an experiment were the chip did not leak and the filter succesfully retained the bacteria introduced in the chip. </p> | ||
+ | </div> | ||
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− | < | + | <img src="https://static.igem.org/mediawiki/2018/f/fd/T--Pasteur_Paris--Test-Filtre-2.jpg"> |
+ | <div class="legend"><b>Figure 10: </b>Membrane filter retaining bacteria on the left (PDMS impurities on the right)</div> | ||
</div> | </div> | ||
+ | |||
+ | <div class="block separator-mark"></div> | ||
<div class="block title"><h3 style="text-align: left;" id="Conductivity">Conductivity</h3></div> | <div class="block title"><h3 style="text-align: left;" id="Conductivity">Conductivity</h3></div> | ||
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− | <p>The second criterion for a fully functional interface is its ability to conduct a neuron’s influx. Thus, conductivity measurements were made for | + | <p>The second criterion for a fully functional interface is its ability to conduct a neuron’s influx. Thus, conductivity measurements were made for different types of membranes. Results indicated that bare alumina oxide and PEDOT:PSS-coated membranes showed similar conductivities, indicating the incomplete coating of PEDOT:PSS on alumina oxide membranes. On the opposite, PEDOT:Cl and PEDOT:Ts exhibit on average better conductivities, but in the same time, the coating of these membranes revealed by electron microscopy seemed to have covered the alumina oxide membranes in a more uniform way, ensuring enhanced conductive capabilities . These results can be criticized because of the high deviation and because the membranes conductivity was measured after several biofilms were grown on them, which may have affected the measurements. </p> |
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+ | <div class="block full"> | ||
+ | <img src="https://static.igem.org/mediawiki/2018/5/50/T--Pasteur_Paris--Membrane-Conductivity.jpg" style="width:500px"> | ||
+ | <div class="legend"><b>Figure 11: </b>Membrane conductivity</div> | ||
</div> | </div> | ||
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+ | </div> | ||
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<div class="block separator-mark"></div> | <div class="block separator-mark"></div> | ||
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+ | <div class="block title"><h3 style="text-align: left;" id="Biocompatibility">Biocompatibility</h3></div> | ||
+ | <div class="block full"> | ||
+ | <p> One last important property of the membranes is the capability of bacteria to form a biofilm on them, as in our prosthesis system, the membrane is going to be directly in contact with the genetically modified biofilm, as well as the human body. We conducted multiple series of biofilm culture on special culture wells designed by our team. Biofilm growth was measured for each type of membrane.</p> | ||
+ | </div> | ||
+ | <div class="block full"> | ||
+ | <img src="https://static.igem.org/mediawiki/2018/8/84/T--Pasteur_Paris--Biofilm-Growth.jpg" style="width:500px"> | ||
+ | <div class="legend"><b>Figure 12: </b>Biofilm growth</div> | ||
+ | </div> | ||
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<div class="block title"><h1>CONCLUSION</h1></div> | <div class="block title"><h1>CONCLUSION</h1></div> | ||
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<div class="block title"><h1>REFERENCES</h1></div> | <div class="block title"><h1>REFERENCES</h1></div> | ||
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− | <ul style="text-align: left;"> | + | <ul style="text-align: left;list-style: disc;"> |
<li style="list-style-type: decimal;">Jikui Wang, Guofeng Cai, Xudong Zhu, Xiaping Zhou, Oxidative Chemical Polymerization of 3,4-Ethylenedioxythiophene and its Applications in Antistatic coatings, Journal of Applied Polymer Science, 2012, Vol. 124, 109-115 .<br><br></li> | <li style="list-style-type: decimal;">Jikui Wang, Guofeng Cai, Xudong Zhu, Xiaping Zhou, Oxidative Chemical Polymerization of 3,4-Ethylenedioxythiophene and its Applications in Antistatic coatings, Journal of Applied Polymer Science, 2012, Vol. 124, 109-115 .<br><br></li> | ||
<li style="list-style-type: decimal;">Alexis E. Abelow, Kristin M. Persson, Edwin W.H. Jager, Magnus Berggren, Ilya Zharov, Electroresponsive Nanoporous Membranes by Coating Anodized Alumina with Poly(3,4ethylenedioxythiophene) and Polypyrrole. 2014, 299, 190-197.<br><br></li> | <li style="list-style-type: decimal;">Alexis E. Abelow, Kristin M. Persson, Edwin W.H. Jager, Magnus Berggren, Ilya Zharov, Electroresponsive Nanoporous Membranes by Coating Anodized Alumina with Poly(3,4ethylenedioxythiophene) and Polypyrrole. 2014, 299, 190-197.<br><br></li> | ||
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<div class="block title"><h1>REFERENCES</h1></div> | <div class="block title"><h1>REFERENCES</h1></div> | ||
<div class="block full"> | <div class="block full"> | ||
− | <ul style="text-align: left;"> | + | <ul style="text-align: left;list-style: disc;"> |
<li style="list-style-type: decimal;">Rigoard, P., Buffenoir, K., Wager, M., Bauche, S., Giot, J.-P., Robert, R., and Lapierre, F. (2009). Organisation anatomique et physiologique du nerf périphérique. /data/revues/00283770/v55sS1/S0028377008004025/.<br><br></li> | <li style="list-style-type: decimal;">Rigoard, P., Buffenoir, K., Wager, M., Bauche, S., Giot, J.-P., Robert, R., and Lapierre, F. (2009). Organisation anatomique et physiologique du nerf périphérique. /data/revues/00283770/v55sS1/S0028377008004025/.<br><br></li> | ||
<li style="list-style-type: decimal;"> https://www.studyblue.com/notes/note/n/chapter-11-nervous-system-ii-divisions-of-the-nervous-system/deck/8819508 <br><br></li> | <li style="list-style-type: decimal;"> https://www.studyblue.com/notes/note/n/chapter-11-nervous-system-ii-divisions-of-the-nervous-system/deck/8819508 <br><br></li> | ||
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<div class="block title"><h1>References</h1></div> | <div class="block title"><h1>References</h1></div> | ||
<div class="block full"> | <div class="block full"> | ||
− | <ul style="text-align: left;"> | + | <ul style="text-align: left; list-style: disc;"> |
<li style="list-style-type: decimal;">MicroProbes for Life Sciences, « Nerve Cuff Electrodes ». Retrieved Oct. 14th, 2018 from https://microprobes.com/products/peripheral-electrodes/nerve-cuff</li> | <li style="list-style-type: decimal;">MicroProbes for Life Sciences, « Nerve Cuff Electrodes ». Retrieved Oct. 14th, 2018 from https://microprobes.com/products/peripheral-electrodes/nerve-cuff</li> | ||
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Latest revision as of 14:49, 10 November 2018
Membrane
When manipulating genetically engineered organisms, it is crucial to guarantee the confinement of these organisms. In our case, we want genetically modified bacteria to stay at the interface between the prosthesis and the external organic medium. At the same time, one of the main issues our project wants to tackle is the conduction of the neuron influx to the prosthesis. The answer to these questions came as a double solution: confinement of the bacteria by conductive nanoporous membranes. The membrane’s nanoporosity allows substances produced by our modified biofilm to pass through the membrane, but the bacteria remain confined. We tested the conductivity and biocompatibility of two types of membranes.
Membrane
Nerve and electrodes
As seen in the other parts of this wiki, we chose to use a nanoporous membrane in our device. The first goal of the membrane was to confine our biofilm, so it does not escape the prosthesis. Moreover, we also used our membrane as a conductive electrode. This solution was interesting since we didn’t have enough time to develop an entire electrical device which collects and treat the signal of the nerves. However, we know we still need to improve our interface if we want the patient to fully control his prosthesis. That is why we decided to look at what is already made in this field. So, first, we detailed how it is possible to model the electrical characteristics of a nerve. Then, we searched for information on electrodes and signal treatment.
This section is principally based on the thesis of Olivier Rossel: Dispositifs de measure et d’interprétation de l’activité d’un nerf. Electronique. Université Montpellier II - Sciences et Techniques du Languedoc, 2012. Français.