Cell-directed-assembly: directing the formation of nano/bio interfaces and architectures with living cells.

BACKGROUND The desire to immobilize, encapsulate, or entrap viable cells for use in a variety of applications has been explored for decades. Traditionally, the approach is to immobilize cells to utilize a specific functionality of the cell in the system. SCOPE OF REVIEW This review describes our recent discovery that living cells can organize extended nanostructures and nano-objects to create a highly biocompatible nano//bio interface [1]. MAJOR CONCLUSIONS We find that short chain phospholipids direct the formation of thin film silica mesophases during evaporation-induced self-assembly (EISA) [2], and that the introduction of cells alter the self-assembly pathway. Cells organize an ordered lipid-membrane that forms a coherent interface with the silica mesophase that is unique in that it withstands drying-yet it maintains accessibility to molecules introduced into the 3D silica host. Cell viability is preserved in the absence of buffer, making these constructs useful as standalone cell-based sensors. In response to hyperosmotic stress, the cells release water, creating a pH gradient which is maintained within the nanostructured host and serves to localize lipids, proteins, plasmids, lipidized nanocrystals, and other components at the cellular surface. This active organization of the bio/nano interface can be accomplished during ink-jet printing or selective wetting-processes allowing patterning of cellular arrays-and even spatially-defined genetic modification. GENERAL SIGNIFICANCE Recent advances in the understanding of nanotechnology and cell biology encourage the pursuit of more complex endeavors where the dynamic interactions of the cell and host material act symbiotically to obtain new, useful functions. This article is part of a Special Issue entitled Nanotechnologies - Emerging Applications in Biomedicine.