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Science  27 May 2011:
Vol. 332, Issue 6033, pp. 1011
DOI: 10.1126/science.332.6033.1011-b

Cellular communication in three-dimensional (3D) tissues often requires contacts between neighboring cells. These events are mediated by the surrounding extracellular matrix, which influences cell positioning and signal transmission and receipt. Although techniques exist for creating 3D cell constructions, they often depend on artificial scaffolds or the manipulation of individual cells via external forces or tools. Dutta et al. use liposomes that incorporate cationic lipids to fuse orthogonal functional groups, in the form of ketone and oxyamine molecules, to cell membranes of different populations of cells, which can subsequently be coupled through selective oxime ligation. Techniques have previously been developed to generate protein tags on a cell's surface, but these tags have tended to be large and bulky, and thus interfered with other glycans and biomolecules or with the biochemical pathways or functioning of the cells. The authors explored a wide range of applications for their methodology, including the delivery of reagents to cell surfaces, formation of spheroid assemblies of cells with controlled interconnectivity, and patterning of multilayered cell tissues. When multilayers of human mesenchymal stem cells and fibroblasts were assembled together, differentiation led to tissue structures resembling adipocytes and fibroblasts. Liposome fusion could be performed on the same cells several times; thus, there is scope for giving cells multiple surface functionalities or for increasing the concentration of the functional groups at the surface.

J. Am. Chem. Soc. 133, 10.1021/ja2022569 (2011).

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