Physics-Biology interface seminar: Yang Si


14:00 - 15:00

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Fluorescent Nano-objects For Bioimaging Applications

Yang Si (ENS Cachan)

Special seminar: poster prize from the NOMBA workshop

Bacteria are the most abundant organisms in the world. Studying models of bacterial chromosome dynamics in the cytoplasm is very important to understand how bacteria adapt to different growth environments and in response to stimuli.

Optical labeling is one of the most common methodologies used for bioanalytical purposes. The fundamental issues for any fluorescent material are the same: brightness and stability. In the quest for very bright and stable labels, novel polymer-based, self-stabilized, fluorescent nanoparticles (FNPs) and fluorescent polymer chains (FPCs) have been developed in the PPSM laboratory. They are brighter, more stable, photobleach slowly and are more easily functionalized compared with other fluorescent labels like GFP and QDs.
A methodology to insert these FNPs (60nm) into E.coli bacteria was developed. To control if the FNP are indeed internalized, we developed a protocol based upon FNP luminescence quenching by methylene blue.

Biotin conjugated FNPs could be used to study specific membrane proteins. By using a strepdavidin-biotin link, we made a “Sandwich” to build a bridge between particles, specific antibodies and bacteria.

Negatively charged FPCs can easily enter into E.coli bacteria. It is found that FPCs can label the cytoplasm but not the DNA, which appears to be more compact. These unique properties will allow the study of DNA and cytoplasm viscosity changes during bacterial growth.

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