Electrostatic self-assembly of agro-sourced biomolecules: structural, thermodynamic study and d[...]

Electrostatic self-assembly of agro‑sourced biomolecules: structural, thermodynamic study and development of stimulable carriers.

15/04/2026 Contrat doctoral – NANCY, Grand Est, France

Electrostatic self‑assembly of agro‑sourced biomolecules: structural, thermodynamic study and development of stimulable carriers.

Colloids, polysaccharides, peptides, interactions, coacervation

Context and Originality

The development of new systems capable of vectorizing active molecules to a defined target is a major research focus of the Laboratory of Biomolecule Engineering (LIBio). The originality of LIBio lies in the formulation of innovative vectors whose constituents are derived from renewable agro‑resources. In this thesis, an original approach based on self‑assembly via electrostatic interactions between polyelectrolytes and small ionized biomolecules will be explored.

Interactions between two polyelectrolytes can lead to the formation of various and complex colloidal structures (aggregates, coacervates, soluble complexes, gels, etc.) depending on numerous parameters such as the chemical nature, molecular weight of the species involved, their relative proportions, pH, ionic strength, etc. Many agro‑sourced polyelectrolytes, such as polysaccharides and proteins, have proven to be good candidates for forming such structures through liquid‑liquid phase separation mechanisms. The interest in these supramolecular assemblies lies in their sensitivity to environmental conditions, allowing control over the formed structures based on the physicochemical properties of the system. This enables the development of assemblies responsive to external parameters such as pH, ionic strength, concentration, temperature or physical actions like shear stress, opening prospects for controlled release of encapsulated actives.

The thesis focuses on the study of self‑assemblies between polysaccharides and peptides via electrostatic interactions. The polysaccharides considered are chitosan (polycation) and gum arabic (polyanion). Peptides will either be commercial or derived from parallel projects within partner laboratories of the Biomolecules 4 Bioeconomy (B4B) project, of which LIBio is an integral part.

Scientific Questions

• What colloidal structures spontaneously form through electrostatic interactions between macromolecules and peptides?
• Is it possible to modulate these structures based on the physicochemical parameters of the medium (pH, ionic strength, temperature)?
• Can the formed structures be used for the encapsulation and controlled release of active biomolecules regardless of their properties?
• What is the impact of adding a charged molecule (polymer or peptide) to preexisting electrostatic assemblies?

Experimental Methods

• Titration techniques (turbidimetry, isothermal titration calorimetry).
• Colloidal stability studies (static multiple light scattering, turbidimetry).
• Particle size and charge measurements (dynamic light scattering, laser granulometry).
• Nanoscale structural characterization (small‑angle X‑ray scattering, access to synchrotron beamline).
• Modification of polysaccharides via enzymatic or chemical routes to modulate interactions.

Future Perspectives

Encapsulation or purification applications will be tested at the end of the thesis, depending on results.

Candidate Profile

Must hold a Master’s degree (BAC+5) in physical chemistry or biochemistry with experience in:

• Peptide extraction, purification, and characterization.
• Polyelectrolyte handling and characterization.
• Colloidal system analysis.

They should have a strong affinity for laboratory work and be able to integrate well into a research team.

Required/Developed Skills During the PhD

• Peptide characterization (chromatographic methods, LC‑MS/MS).
• Biopolymer characterization (Fourier‑transform infrared spectroscopy, size‑exclusion chromatography, nuclear magnetic resonance).
• Characterization of nano‑ and micro‑objects (size, structure, charge).
• Thermodynamic parameters of interactions.
• Small‑angle scattering (SAXS).