Morphology, mechanical properties and viability of encapsulated cells.

The morphological and mechanical properties of encapsulated yeast cells (Saccharomyces cerevisiae) have been investigated by atomic force microscopy (AFM). Single living cells have been coated through the alternate deposition of oppositely charged polyelectrolyte (PE) layers. The properties of cells coated by different numbers of PE layers and from PE solutions of different ionic strength have been investigated. AFM imaging indicates an increase in PE coating stability when decreasing the solution ionic strength. The Young's moduli of the different examined systems have been evaluated through a quantitative analysis of force-distance curves by using the Hertz-Sneddon model. The analysis indicates an increase in hybrid system stiffness when lowering the ionic strength of the PE solution. An evaluation of the viability of encapsulated cells was obtained by confocal laser scanning microscopy (CLSM) measurements. CLSM analysis indicates that cells preserve their subcellular structure and duplication capability after encapsulation. By coupling AFM and CLSM data, a correlation between local stiffness and duplication rate was obtained.