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M2

Nanoscale resolution optical imaging of bone and teeth porosity using single particle tracking.

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The characterization of bone and teeth porosity at the microscopic and nanoscopic scale ( 0.01-100 µm) is an important biomedical challenge. This porosity results from the biological cellular activity during bone/teeth formation and repair and may have a mechanical function which is not yet elucidated. The methods currently used in materials science for 3D imaging with resolutions of 10-50 nm (e.g. X-ray nanoCT, FIB-SEM) are either too localized to provide a statistically representative view of the system, or fail to preserve the living tissue in its functional state. Thus, there are strong perspectives offered to new methods based on super-resolution optical microscopies such as single particle tracking (SPT) using quantum dots or nanoparticles.

This master project follows a PhD which allowed acquiring a unique expertise in confocal and non-linear optics imaging and characterization of the cellular network in bone and dentin. Although the network characteristics could be precisely evaluated, the typical spatial resolution that can be achieved using those techniques is 200 nm in the transverse direction. A better optical resolution (50 nm or less) is, thus, required to characterize the smallest porosity and obtain reliable quantitative measurements. This could, in principle, be achieved by tracking single fluorophores in diluted concentration within the porosity, similar to PALM/STORM super-resolution techniques. The trick to overcome the optical diffraction limit, is to use very small particles (quantum dots, nanoparticles) which displacement can be used to reconstruct their local environment with about 10nm accuracy.

The objectives of this internship are :
- to define a protocol for SPT imaging using quantum dots and gold nanoparticles.
- to establish the data processing tools framework for image reconstruction.
- to validate a proof of concept for SPT imaging of porosity in dentin.
This study first relies on experimental work (sample preparation, SPT microscopy) combined with image treatment to analyze the multiscale porosity.

This project is at the Physics/Medicine interface and could suit a candidate with a background in Physics or Materials Science wishing to strengthen his/her knowledge in imaging with biomedical perspectives, or to a biologist with a strong background in microscopy wishing to develop new methods for the study of complex networks similar to neurons or vascular ones.

The project will be performed in close collaboration with the laboratory MSSMat of the Ecole Centrale Paris and the INSERM U1033 unit in Lyon.

Contacts :
Aurélien Gourrier, aurelien.gourrier@univ-grenoble-alpes.fr, 0476514729
Aurélie Dupont, aurelie.dupont@univ-grenoble-alpes .fr, 0476635816

Particle tracking