Biomedical Engineering Reference
In-Depth Information
Nature. For example, Safarik et al. imparted new functions of paramagnet-
ism to yeast cells Kluyveromyces fragilis
9
and Saccharomyces cerevisae
10
by the
direct deposition of magnetic iron oxide nanoparticles on the cell wall. In the
initial step the cells were washed with acetic acid or saline solution to re-
move the extracellular compounds from the cell wall and reduce the non-
specific binding. Then, the cell suspension was incubated with magnetic
nanoparticles that led to magnetically responsive yeast hybrids. It was ob-
served that the nanoparticle stabilization agents influenced the e
ciency
and incubation time for magnetization of the cells.
11
In the case of magnetic
nanoparticles that were stabilized by sodium citrate, the obtained magnetic
coating on the cell surface was thin and poor and required a longer incu-
bation time than other agents. Using tetramethylammonium hydroxide or
perchloric acid-stabilized nanoparticles made the process of cell magnet-
ization faster and more ecient. Magnetic nanoparticle-cell hybrids were
applied to the development of biosorbents, biocatalysts, and new cell isol-
ation techniques. The magnetized cells were shown to effectively absorb
heavy metal ions from solution, including toxic mercury,
10
and were easily
separated using an external magnetic field. The catalytic functions of mag-
netic nanoparticles interfaced cells have been demonstrated by hydrogen
peroxide decomposition and sucrose conversion by intracellular enzymes.
This fact indicates that the cell magnetization is nontoxic and modified cells
preserve their metabolic activity.
11
From the studies described above we can see that by using a suitable
stabilizing mediator it is possible to deposit nanoparticles of great variety of
shapes and compositions. Therefore, different types of 1D and 2D nano-
structures could also be used to modify the cell surface. Among these
alternative nanomaterials multilayered polyelectolyte-based nanofilms were
extensively used to modify cell surfaces to obtain hollow micro- and nano-
capsules for living cell encapsulation. In general, they were deposited onto
the cells via layer-by-layer assembly of oppositely charged polyelectrolytes
and were also utilized as mediators for nanoparticles deposition.
12
Since the
deposition of nanofilms often cannot be completed in a single step this
technique is beyond the scope of this chapter and was discussed in more
details in Chapter 2.
Carbon nanomaterials are of particular interest as materials for cell
functionalization due to their unique electronic, optical, thermal, mechan-
ical, and chemical properties. Biocompatible carbon nanotubes were inter-
faced with the cytoplasmic membrane of Chinese hamster ovary cells via
carbohydrate receptors. The carbon nanotubes were first coated with mucin-
like glycoproteins to mimic the surface chemistry of a cell followed by
specific interactions via the carbohydrate-binding protein lectin, which is
capable of crosslinking cells and glycoproteins. The most important obser-
vation was that these coated tubes were found to be noncytotoxic while
uncoated tubes were cytotoxic.
13
The group of Maheshwari demonstrated the interaction of graphene
sheets with yeast cells for a ''dual-use technology'' application.
14
In one case
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