Résumé
Plant cell suspensions are remarkable platforms for the production of therapeutic proteins. The commercialisation of plant cell products, despite its safety and low cost, is limited by low yields, cell fragility, poor control over cell development, and product purification [1]. The encapsulation of cells in porous matrices has been considered for addressing those issues. The matrix provides protection against mechanical stress, control on cell growth, and facilitates the separation of the product. Nonetheless, current immobilisation materials often display poor mechanical resistance and poor diffusive properties. The former leads to cell leakage, while the latter is due to the addition of a matrix around the biological entities, which will limit mass transfer.The aim of the present research is to design a suitable matrix that satisfies biocompatibility, mechanical and diffusive requirements for the immobilisation of higher plant cells. For this purpose, several bio-sourced polymers forming in mild conditions, to preserve cell viability, were assessed in combination with silica, to strengthen the matrix, to form an hydrogel bead around the cells[2 − 4]. In the study of potential polymers such as cellulose, pectin or gellan gum, only alginate material allowed to form a stable hybrid hydrogel with silica in a one-pot synthesis. Alginates low (2.0 wt.%-3.5 wt.%) and medium viscosities (2.0 wt.%-3.0 wt.%) formed stable hydrogel beads by ionotropic gelation with calcium ions, and silica (0.75 M) by aqueous solgel. Additionnaly, a polycation was used to further enhance the stability of the alginate-silica matrix by polyelectrolytic complexation. The synthesis conditions that influenced the matrix properties have been studied and optimised to obtain hydrogel spherical beads compatible with living higher plant cells. When characterized using nitrogen physisorption, dried beads featured a pore size superior to 50 nm, that should allow the diffusion of nutrients and metabolites. However, molecular probe (1.1 nm-12.5 nm) diffusion permeability assay showed no exchange between the matrix and its environment.
Alginate-silica materials were then successfully used for the immobilisation of Nicotiana tabacum cells producing recombinant immunoglobulin G. The cell viability was preserved for a eriod of 15 days. However, the protein could not be recovered outside the beads, as observed by electrophoretic analyses, probably due to the diffusion related issues. The hybrid material also provided better containment of the cells compared to beads made of alginate alone. These results show that hybrid matrices are a promising candidate for the immobilisation of higher plant cells, provided that the remaining diffusion issues are addressed.
| la date de réponse | 4 sept. 2023 |
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| langue originale | Anglais |
| L'institution diplômante |
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| Sponsors | Fund for Research Training in Industry and Agriculture (FRIA) |
| Superviseur | BAO LIAN SU (Promoteur), Catherine Michaux (Président), Stephane Vincent (Jury), Alain KRIEF (Jury), Pierre Van Cutsem (Jury), Marc Boutry (Jury) & Amin Shavandi (Jury) |