Conformational switch

Temperature-induced conformational switch of PNIPAM

PNIPAM is a thermosensitive polymer that undergoes a reversible coil-to-globule conformational transition around its lower critical solution temperature (LCST), around 32°C. It switches from a hydrophilic, swollen state to a hydrophobic, collapsed state.

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PNIPAM-based immunoassay

Immunoassay based on the thermal precipitation of PNIPAM

The peculiar properties of PNIPAM make it possible to use this polymer as a support for immunoassays based on thermal precipitation.

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Cell culture

Cell culture on PNIPAM-grafted surfaces

PNIPAM-grafted surfaces can be used as a soft support for cell cultures. Cells grow on hydrophobic PNIPAM and are softly released by lowering the temperature and making the PNIPAM hydrophilic.

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Adsorption and release of proteins

Controlled adsorption and release of proteins on hydrophobic PNIPAM-grafted surfaces

The same way cells adsorb on hydrophobic PNIPAM surfaces, proteins may be reversibly trapped on PNIPAM surfaces, then released upon command. This is actually one of the things I did during my thesis.

• Download the resizable, editable SVG source file (SVG, 63 KB)

Licensing and reuse

All the source files are vector graphics, i.e. they can be resized at will without loss of quality or pixelation. They are released under a Creative Commons Attribution ShareAlike license, which means you are free to use them, modify them, redistribute them for any purpose as long as you appropriately attribute them, and that you distribute any derivative works only under the same license.

Opening out

In January 2008, I attended the Biodevices conference in Madeira (see my article about Biodevices). I also took a few days of vacation to visit the island after the conference. It was not yet the season for flowers, but it was really beautiful and flowers were growing all over the island; among them were strelitzias, also called birds of paradise. When I saw them, it hit me: they were a perfect symbol of unfolding. Besides, they were orange and blue, my two favourite complementary colors. They were just perfect. I took a lot of pictures of strelitzias and I used them to design a draft logo that represented a bird of paradise unfolding.

A bird of paradise in Madeira

Design principle: user testing is mandatory

First draft logo

Every designer will tell you that no matter how hard you work on a product, you have to seek feedback from users and people who have not been involved in the process. I would even say that the harder and the longer you work on it, the more you have to seek external feedback. In the case of my draft logo, I had worked on it so long that it was obvious for me it represented an opening strelitzia.

However, the first two people I asked did not think of a strelitzia; instead they asked me why my logo was some sort of chimera that would be the improbable result of a one-night stand between a slug and a hedgehog. Thanks to their comments, I managed to see through their eyes and I had to admit they were right, so I tweaked the logo a bit.

Final logo

In order to avoid the confusion with a sludgehog, I added a small stem to the flower. Now, if someone does not recognize a strelitzia at first, they will think it represents some sort or bird, which is much better than the previous mythical creature.

Final logo

Unlike most of the website, this logo is not released under a free license for an obvious reason: a logo is meant to identify a unique entity, and this entity is unfoldscience.

Links

• Download the vector graphics logo (SVG, 23.5 KB)

Preview of the thesis

I am glad to announce that my Ph.D thesis is now available for download. The document, called Technologies PNIPAM pour les laboratoires sur puce (“PNIPAM technologies for lab-on-chips”) is only available in French (University policy), but there are some pretty pictures and infographics in there too for people who don’t speak French; one of them is the “Interdisciplinarity, biology and micro-nanotechnologies” information graphics I published earlier.

Summary

Labs on chips are miniaturized devices integrating one or several laboratory functions, usually dedicated to the handling of chemical and biological samples. Our work aimed at integrating a smart polymer called poly(N-isopropylacrylamide) (PNIPAM) in microsystems, in order to develop a new technological process for labs on chips.

PNIPAM is a thermosensitive polymer that undergoes a reversible state transition; it switches from a hydrophilic, swollen state below its temperature of transition (LCST ~ 32°C), to a hydrophobic, collapsed state above it. The technology we developed is based on heating elements and a surface functionalization process to graft the PNIPAM layer.

Our results show that the electro-osmotic flow can be modulated by thermally controlling the PNIPAM, thus paving the way to electrokinetic mixers. This thermal control also enables the adsorption (and partial desorption) of proteins on fonctionalized beads, the main application being sample preparation.

Keywords: Lab on a chip, NIPAM, microfluidics, thermosensitive polymer.

Tools

I mainly used LaTeX to create this document. All vector infographics were made using Inkscape.

Although the PDF file can be searched as plain text, I have also started to convert the document to wikitext in order to make the whole content available on Wikisource. However, this process takes time and I have other priorities at the moment, so any help is welcome.

Licensing & reuse

I released the whole document under a GNU free documentation license, which means you are free to use it, modify it, redistribute it for any purpose as long as you appropriately attribute it, and that you distribute any derivative works only under the same license. You also have to provide a copy of the license.

Link

• Download the high-quality PDF thesis (PDF, 130 p., 6.45 MB)

Because technology provides the tools and biology the problems, the two should enjoy a happy marriage.

Although this statement is awfully simplistic, biology and technology do enjoy a happy marriage, and I was thrilled to experience it during the last three years. My Ph.D work has been very interdisciplinary and I wanted to dedicate a special section of my thesis to how cool, yet difficult, it is to work at the crossroads of biology, chemistry, physics & technology. Because an image is worth a thousand words, I assembled a nice comparison of various reference biological objects and technological devices at the micro- and nanoscale. Most of the images I used were available on Wikimedia Commons and I made the others.

Biological and technological scales compared

The source file is vector graphics, i.e. it can be resized at will without loss of quality or pixelation. It is released under a Creative Commons Attribution ShareAlike license, which means you are free to use it, modify it, redistribute it for any purpose as long as you appropriately attribute it, and that you distribute any derivative works only under the same license.

Links

• Download the vector graphics source file (SVG, 1.46 MB)
• See the author & licensing information page on Wikimedia Commons, including links to all the images used in this one

Notes