Marie-Laure did a 3 months research internship in Prof Paunov’s group at the University of Hull in 2005 as an exchange student from ENSCR (Rennes, France). She is currently a research engineer at Lactalis, France.  Internship supervisors: Prof Vesselin Paunov (PI) and Dr Olivier Cayre (Co-PI)

Research project 1:

Fabrication of Spherical Cellosomes of Living Yeast Cells

(In collaboration with Dr R. Fakhrullin with whom we later developed cellosomes of rhombohedral shape)

We pioneered a new class of colloid structures, cellosomes, which represent hollow microcapsules whose membranes consist of a single monolayer of living cells [1]. These structures were designed based on templating of air bubbles with living cells, which allowed us to fabricate spherical cellosomes (Fig. 1). Air microbubbles were templated by yeast cells coated with poly(allylamine hydrochloride) (PAH), then coated with carboxymethylcellulose and rehydrated resulting in the formation of spherical multicellular structures (Figs. 3-4). Yeast cells locked in the cellosome membrane remain viable after the assembly for up to 2 weeks (Fig. 4). Our methods for fabrication of cellosomes may found applications in the development of novel symbiotic bio-structures, artificial multicellular organisms and in tissue engineering. The unusual structure of cellosomes resembles the primitive forms of multicellular species, like Volvox, and other algae and could be regarded as one possible mechanism of the evolutionary development of multicellularity.

Fig. 1 Schematic representation of experimental approaches for the development of celloidosomes: formation of spherical celloidosomes templated on air microbubbles.

Fig. 2 Optical microscopy images of air-bubbles with adsorbed layers of PAH-percoated yeast cells. The cells are attracted to the air-water interface and form dense monolayers which were further jammed with oppositely charged polyelectrolyte (PSS or CMC).

Fig. 3 Optical images of an air bubble templates with yeast cells and polyelectrolytes and the result of its dissolution – formed cellosome of living yeast cells.

Fig. 4 SEM images of the formed cellosomes. Note that these structures are rigid enough to retain their spherical geometry even after drying.

Fig. 5 (a) Optical microscope image of yeast cells coated with PAH/PSS/PAH layers after treatment with fluorescein diacetate (FDA); (b) Fluorescence microscopy image of the same sample with FITC filter set. Optical micrograph in transmitted light (c) and the corresponding fluorescence microscope image (d) of yeastosomes after treatment with FDA. The green fluorescence indicates that both the individual yeast cells and the ones assembled in the yeastosomes are still viable after coating with polyelectrolyte and assembly into coherent shells [1].

References

1. . Brandy, M.K., Cayre, O.J., Fakhrullin, R. F., Velev, O.D., Paunov, V.N., “Directed assembly of cells into living yeastosomes by microbubble templating”, Soft Matter, 6 (2010) 3494-3498.