In a cell nucleus, the genome is folded in a complex architecture. Our understanding of the physical principle responsible for this complex organization is still limited. It would be useful to be able to directly exert and measure forces on chromosomes in live cells to study these questions. In this project, we present a novel magnetic nanoprobe that can bind to a specific genomic locus and apply a force to this locus. This probe is an iron oxide nanoparticle coated with specific polymeric ligands. The first challenge lies in avoiding nonspecific interactions between the nanoprobes and biomolecules in the very crowded intranuclear environment. To achieve this, we have designed a specific diblock copolymer to coat the nanoparticles. The first block contains sulfobetaine zwitterions that are very efficient to eliminate nonspecific interactions. The second block contains multiple anchoring groups to ensure long term anchoring stability. The absence of interactions with proteins with the selected polymer coating has been assessed in vitro and in live cells. The second challenge is to conjugate specific proteins that will target selected DNA sequences. We have achieved controlled and efficient binding of targeting proteins to the surface of our nanoparticles, via copper free click chemistry. Here we functionalize our nanoparticles with fluorescent dyes for visualization and with GFP, which will bind to an anti GFP nanobody, fused to a fluorescent protein and a domain that binds a specific DNA sequence in our cell model. The efficiency of the targeting has been assessed after microinjection of the nanoparticle solution in the nucleus of live cells. Manipulation of the genomic locus has been performed with a magnetic tip that produces a strong magnetic field gradient. The magnetic nanoparticles in this gradient are submitted to a force that can move the genomic locus over several micrometers.

Zwitterionic nanoparticles for manipulating chromosomes in live cells

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ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.