Biomimetic cell-mediated three-dimensional assembly of halloysite nanotubes.

Biomimetic architectural assembly of clay nanotube shells on yeast cells was demonstrated producing viable artificial hybrid inorganic-cellular structures (armoured cells). These modified cells were preserved for one generation resulting in the intact second generation of cells with delayed germination.

A whole-cell amperometric herbicide biosensor based on magnetically functionalised microalgae and screen-printed electrodes.

We report the fabrication of an amperometric whole-cell herbicide biosensor based on magnetic retention of living cells functionalised with magnetic nanoparticles (MNPs) on the surface of a screen-printed electrode. We demonstrate that Chlorella pyrenoidosa microalgae cells coated with biocompatible MNPs and retained on the electrode with a permanent magnet act as a sensing element for the fast detection of herbicides. The magnetic functionalisation does not affect the viability and photosynthesis activity-mediated triazine herbicide recognition in microalgae. The current of ferricyanide ion was recorded during alternating illumination periods and biosensor fabricated was used to detect atrazine (from 0.9 to 74 µM) and propazine (from 0.6 to 120 µM) (the limits of detection 0.7 and 0.4 µM, respectively). We believe that the methodology presented here can be widely used in fabrication of a number of whole cell biosensors since it allows for efficient and reversible cells immobilisation and does not affect the cellular metabolism.

Polyelectrolyte-mediated assembly of multiwalled carbon nanotubes on living yeast cells.

Here we report the three-dimensional assembly of carbon nanotubes on the polyelectrolyte-coated living Saccharomyces cerevisiae cells using the polyelectrolyte-mediated layer-by-layer approach. Synthetic polyelectrolytes poly(allylamine hydrochloride) and poly(sodium 4-styrenesulfonate) were layer-by-layer deposited on the surfaces of the yeast cells followed by the deposition of water-soluble oxidized multiwalled carbon nanotubes (MWNTs) and an additional outermost polyelectrolyte bilayer. This resulted in the fabrication of polyelectrolyte/nanotubes composite coatings on the cell walls of the yeast cells, which could be clearly seen using the conventional optical microscopy. Transmission and scanning electron microscopy was applied to further investigate the composite coatings. Viability of the encapsulated cells was confirmed using the intercellular esterase activity test. Finally, electrochemical studies using voltammetry and electrochemical impedance measurements were performed, indicating that the composite polyelectrolytes/MWNTs coatings sufficiently affect the electron mediation between the encapsulated yeast cells and the artificial electron acceptor, making it possible to distinguish between living and dead cells. The technique described here may find potential application in the development of microelectronic devices, core-shell and hollow composite microparticles, and electrochemical cell-based biosensors.