Metal partitioning in coccolith-based calcite and biotechnological applications of metal-doped coccolith materials

Despite established cultures of coccolithophore microalgae and attainable large-scale production of coccolith biominerals (gram quantities of calcite mineral from litres of culture), the coccolith as an advanced functional material has made little progress in bionanotechnologies. This project will quantitatively describe metal doping into and on the surface of coccolith-based calcite for several transition metals, main group elements and lanthanides. Elucidating the potential of coccolithophore to incorporate metal ions into/onto biogenic calcite production will not only reveal the biotechnological possibilities for coccolith materials but will offer insights on the role of metals in the biomineralization process and the biological screening effect. Metal-doped coccolith materials will be subjected to physical and chemical characterization (focus placed on strategic metals that have enchanced incorporation into biogenic calcite or can be replaced/deposited on coccoltih surface). Select metal-doped coccolith candidates will be pursued for biotechnological application accordingly based on their physical and optical properties (e.g., catalytic activity for transition metals and photoluminescence for lanthanides).

Characterization of the grafting efficiency of antigenic proteins to capsid like particles for vaccine development

Among the vectors used to develop vaccines, virus-like particles (VLPs) are particularly interesting for the transfer of antigens (Ag). In fact, VLPs self-assemble into molecular motifs associated with pathogens, triggering vigorous immune responses, thus avoiding the need for adjuvants. As part of an ANR project in partnership with the Institut de Biologie Cellulaire Intégrative de Gif sur Yvette and the Institut Gustave Roussy de Villejuif, we are interested in the structural characterization of vaccines based on T5 bacteriophage pseudocapsids (T5-CLP).
During development, various quality indicators need to be reliably assessed to guide vaccine design, control production or verify safety and stability. Several attributes affecting the purity, efficacy and safety of T5-CLPs have been identified. Among these, the amount of Ag grafted is considered critical, as it determines vaccine efficacy. In this thesis, we propose to develop the potential of nanocharacterization technologies to rapidly and reliably validate the antigenic load of these vaccine particles. To do this, we will draw on conventional approaches such as proteomics and electron microscopy, and on a selection of advanced nanocharacterization technologies including nanoresonator mass spectrometry.

Nano-object simulations in biological media

Understanding the non-specific or specific interactions between biomolecules and nanomaterials is key to the development of safe nanomedicines and nanoparticles. Indeed, adsorption of biomolecules is the first process occurring after the introduction of biomaterials into the human body, which controls their biological response. In this thesis, we will simulate the interface between nanosystems and biomolecules on a scale of a hundred nanometers, using the new exascale computing resources available at the CEA from 2025 (Jules Verne machine installed at the CCRT).

Nano- and micropatterned biomineral-based materials: Orientation-specific assembly of coccoliths into arrays

Coccoliths of coccolithophorid algae are anisotropically-shaped microparticles consisting of calcite (CaCO3) crystals with unusual morphologies arranged in complex 3D structures. Their unique micro- and nanoscale features make coccoliths attractive for various applications in nanotechnology. It is anticipated that the range of applications of coccoliths can be further extended by (bio)chemical modification and functionalization as well as possibilities for their arrangement into 2D and 3D arrays. However, methods for both aspects are still lacking.
The aim of this project is thus to develop methods for regioselective functionalization of coccoliths and their assembly into arrays. Regioselective functionalization of the margin area and central area of coccoliths will be achieved by exploitation of local differences in the composition of the insoluble organic matrix of coccoliths. The existence of local differences in the composition of biomacromolecules within this matrix has only very recently been demonstrated. In particular, we will regioselectively introduce proteins/(poly-)peptides that can serve as “anchoring points” for in vitro modifications into the insoluble organic matrix of coccoliths by genetic engineering of a coccolithophore. These engineered coccoliths form the basis for the construction of coccolith arrays. Three independent approaches for the assembly of such arrays will be pursued. The structural and physico-chemical properties of the coccolith-based magnetite-calcite hybrid material will be determined by means of a number of analytical methods.
This interdisciplinary project will benefit greatly from the complementary expertise of the binational groups. In the long term, we aim to create an advanced pool of methods to regioselectively endow coccoliths with desired properties and to develop new biomineral-based materials for nanotechnological applications.

Aptamer-based molecular fingerprinting for the diagnosis of neurodegenerative diseases.

The PhD project consists of developing a novel diagnostic capable of detecting the signature of a pathological forms of protein intimately associated to neurodegenerative diseases. The aim is to improve the diagnosis of patients suffering from neurodegenerative proteinopathies due to the aggregation of the proteins alpha-synuclein and tau, e.g. Parkinson’s and Alzheimer’s diseases. This project builds on our team's expertise in aptamer technology (nucleic acid-based ligands) and the production of structurally distinct aggregates of alpha-synuclein and tau that we demonstrated to trigger distinct synucleinopathies and tauopathies. During this work, different aptamer libraries will be evaluated against different polymorphs of protein fibers found in different diseases. These aptamers will then be used to design a diagnostic test using a recently patented method (AptaFOOT-Seq). The student should have a strong interest in biomedical research, particularly the molecular aspects of biology. This thesis will provide in-depth training in RNA and protein synthesis and purification, directed molecular evolution, quantitative PCR (qPCR and droplet PCR), high-throughput sequencing, bioinformatics analysis and structural biochemistry. The aim of the thesis is to obtain results that can be exploited in terms of intellectual property and to enable the student to envisage a career in an academic or industrial environment.

Development of new antidote formulations based on chitosan-coated bilosome with active targeting, against intoxications by organophosphorus neurotoxins for nasal administration

The aim of this innovative project is to develop and validate the biological efficacy of new formulations including original and patented reactivators (CNRS/IRBA). These molecules present a large spectrum of action against acetylcholinesterase (AChE) inhibited by Organophosphorus Neurotoxins (NOPs), hence the interest in developing centrally effective antidotes for nose-to-brain administration. The novel bilosome-based formulations designed at CEA will be administered via the non-invasive nasal route, which could enable delivery to the brain either after passage into the systemic circulation, or by absorption through the olfactory nerves which provides direct access to cerebrospinal fluid and brain parenchyma, bypassing the blood-brain barrier (BBB). The approval by health authorities of Nyxoïd (naloxone) and Valtoco (diazepam) demonstrates the relevance of nasal therapeutic approaches to emergency situations (e.g. overdose, epilepsy) in subjects who may be unconscious or in respiratory distress. The project's innovations could ultimately interest the recently-created french company OPGS Pharmaceuticals, for the valorization of the work with the preclinical development (toxicity, selectivity...) and a possible industrialization of this medical countermeasures.
The thesis will take place in TOULOUSE.