Building cellosomes from living cells

Spherical yeastosome in the making. The air bubble around which the cells have been templated slowly dissolves in the aqueous phase but the cells stay “jammed” in the cellosome structure by the polyelectrolyte layer which is holding them together. The cells remain viable during this procedure so we end up with a living multicellular structure.

Magnetic yeast

Manipulating magnetic yeast cells with a magnet.

Magnetic yeastosomes

Manipulating yeast cellosomes templated on magnetite pre-coated aragoinite microcrystals with an external magnet.

pH triggered release of encapsulated probiotic cells from shellac microcapsules

Shellac-cell microcapsule bursts upon changing the pH above 7 to release viable cells in the environment. The effect is triggered by a tiny amount of swelling microgel doping the shellac matrix. The capsule protects the cells in acidic environment.

Magnetic emulsion

Styrene-in-water emulsion with hydrophobised magnetite nanoparticles dispersed in the oil phase. Note that the magnetite nanoparticles are attracted by the magnet and segregate in one part of the each emulsion droplet forming an anisoptropic structure. We “arrest” these structureed by polymerising the emulsion drops in the presence of the magnet to produce micromagnets – anisotropic magnetic microparticles  – see next video.

“Cat-eye” magnetic emulsion

When the magnetite nanoparticle concentration in the styrene-in-water emulsion is high enough, the application of external magnetic field causes the magnetite particles to aggregate in strange structures which are reminiscent of cat-eye. Once magnetic field is applied these platelet structured magnetite remain in the emulsion drop and follow the rotation of the magnetic field.

“Magnetic mixer” from a magnetic emulsion

At high magnetite concentration in the oil phase, magnetic emulsion in external magnetic field develops anisotropic structures where the magnetic material forms a separate compartment in each emulsion drop once the external magnetic field is applied. As you can see rotating the magnet causes quite a “stir”. This effect can be used to make microreactor mixers of out each emulsion drop.

Magnetic lanes from Janus particles

After polymerizing magnetic emulsions with gelled continuous aqueous phase in permanent magnetic field we released the particles by melting the hydrogel and washing them with water. The video clip shows what happened when you apply magnetic field to the produced magnetic Janus particles which tend to order in chains in specific manner which leads to formation of magnetic lanes.

Rotating magnetic Janus particles

The video clip shows the response of magnetic Janus particle upons rotation of a magnet in near vicinity.

Magnetic Pickering Janus particle

The video clip shows the response of a polymerised Pickering oil drop with magnetically segregated magnetite nanoparticle on its surface. The produced solid microparticle rotates with the position of the magnet in near vicinity.

Snakes and Ladders chip design for coating of drops of ferrofluid

The video clip shows our Snakes and Ladders chip in action. Magnetic drops are generated and fed into the chip from the LHS of the chip. The channels contains streams of  solutions of polyelectrolyte with alternating charge. A permanent magnet makes the drops to move down the side channels and pass through streams of different polyelectrolyte solutions.  The final result is a Layer-by-Layer coating on the surface of the drops leaving the chip from the RHS. More details in Lab on a Chip, 17 (2017) 3785 – 3795. doi: 10.1039/c7lc00918f.

More information can be found in the following references:

Fakhrullin, R.F., Garcia-Alonso, J., Paunov, V.N., “A Direct technique for preparation of magnetically functionalized living yeast cells”, Soft Matter, 6 (2010) 391-397.

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.

Dyab, A.K.F., Ozmen, M., Ersoz, M., Paunov, V.N., “Fabrication of novel anisotropic magnetic microparticles”, J. Mater. Chem., 19 (2009) 3475-3481.

Fakhrullin, R.F., Brandy, M.K., Cayre, O.J., Velev, O.D., Paunov, V.N., “Live celloidosome structures based on the assembly of individual cells by colloid interactions”, Phys. Chem. Chem. Phys., 12 (2010) 11912-11922.

Fakhrullin, R., Paunov, V.N., “Fabrication of living cellosomes of rod-like and rhombohedral morphologies based on magnetically responsive templates”, Chem. Commun, 19 (2009) 2511-2513.

Alorabi, A.Q., Tarn, M.D., Gómez-Pastora, J., Bringas, E. Ortiz, I.,  Paunov, V.N., Pamme, N.,  On-chip polyelectrolyte coating onto magnetic droplets – towards continuous flow assembly of drug delivery capsulesLab on a Chip, 17 (2017) 3785 – 3795.