Functional Multilayered Polyelectrolyte Assemblies on Biological Cells - Cell Surface Engineering: Fabrication of Functional Nanoshells - page 19

technique is reported, where the living lymphocytes are functionalized via
LbL assembly combined with a photolithographic-patterning technique
(Figure 2.5c). 81 The peculiar feature of this work is the selective functiona-
lization of the cellular membrane, i.e. just a certain part of the cell is coated
with polymers, while the bulk of the cell remains intact.
The development of biosensors also requires the surface modification of
human cells, for instance, human breast cancer cells are encapsulated in
multilayers built from various polycations (PEI, PAH, PLL or PDDA) and
polyanions (PSS or PAA). 87 The LbL deposition of polymers was applied not
only to single cells, but also to multicellular assemblies such as pancreatic
islets. Polymer-encapsulated islets are believed to find applications in cell-
based therapy of type I diabetes as therapeutic transplants with increased
immune response resistance with polymer shells acting as a barrier between
the transplant and the immune system. Isolated islets consisting of nu-
merous cells assemble in spherical aggregates of around 200 mm are coated
with PAH/PSS, PDDA/PSS and PLL-PEG/AL. 78 The comparatively large
diameters of pancreatic islets outline a modified coating procedure. Islets
are retained in cell-culture inserts with small pores (12 mm), which are filled
with polyelectrolytes, incubated and then drained and washed with appro-
priate buffers. This allows numerous centrifugation steps to be avoided,
which may lead to unnecessary aggregations.

d n 8 y 4 n g | 4

2.2.2.3 Multicellular Animals
Although the modification and engineering of the cell surfaces with poly-
mers/nanoparticles became a versatile tool to control the physiological
parameters and the spatial distribution of the modified cells, this technique
has been limited exclusively to unicellular organisms so far. Since the
multicellular organisms are regarded as considerably more complex than
unicellular species, both in terms of physiology and behavior, the en-
capsulation of multicellular organisms with polyelectrolytes and nano-
particles may provide the scientific community with a powerful instrument
to study ecology, behavior, and motility of microscopic invertebrates via
tailoring functional moieties using LbL assembly. Fakhrullin and cow-
orkers report the surface modification of microscopic live multicellular
nematodes Caenorhabtidis elegans with polyelectrolyte multilayers (pure
and doped with 20-nm gold nanoparticles) and the direct magnetic func-
tionalization of nematodes with biocompatible magnetic nanoparticles.
Magnetically functionalized nematodes can be effectively separated and
moved using an external magnetic field. At the same time, the surface-
functionalized nematodes preserve their viability and reproduction
(Figure 2.6a). 88
Inspired by strategies in the living systems generated by evolution,
Tang and coworkers induced an extra UVB-adsorbed coat on the chorion
(eggshell surrounding embryo) of zebrafish, during the blastula period.
Short and long-term UV exposure experiments show that the artificial

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