Biomedical Engineering Reference
In-Depth Information
yields even further and reducing the cost of biomineralization methods will require
imaginative solutions, including both production in different hosts and
in vitro
synthesis. If magnetosomes can be prepared with increased yields and superior
modifi cation/functionalization, they will become attractive materials for commer-
cial biomedical nanomagnets, although for this to occur it will be important not
only to develop
in vitro
biomedical systems on a commercial basis but also to
develop
in vivo
-based systems for targeted therapies.
This may be achieved by utilizing the present knowledge base for immobilizing
and displaying proteins and DNA on magnetosomes (see Section 11.5). It should
be possible to adapt and modify crosslinking and genetically modifi ed fusion
protein expression to accommodate new proteins, drugs, and genes as they are
developed. It should be noted here that magnetosomes that express fusion proteins
may prove to be particularly advantageous. In addition, if several bioactive com-
pounds can be attached to one particle in specifi c quantities, by utilizing different
anchor-fusion proteins and expression promoters, then biomedical nanomagnetic
particles with multiple and complex functions could be developed.
Whilst magnetosomes are perhaps the best heat-loss material for hyperthermic
therapies studied to date, cobalt-enhanced magnetosomes may improve this effect
further. Future studies in this area should not only test the specifi c heat - loss of
cobalt-enhanced magnetosomes, but also be followed by toxicology studies, further
functionalization and animal and clinical trials. In this respect, the cobalt doping
of magnetosomes has opened up a range of possibilities to manipulate the com-
position of biomagnetite. The knowledge that cobalt doping is possible, and that
magnetic characteristics could also be varied with other magnetic metal dopants
such as nickel or manganese, will surely lead to future investigations.
The ability to alter the magnetic properties of magnetite, and in turn other
particle specifi cations, by varying the particles' sizes is vital. At present, despite
magnetic bacteria having been identifi ed with variously shaped and sized magne-
tosomes, only cubo-octahedral particles may be used, and consequently a vast
potential of various magnetosomes is left untapped. To overcome such limits, a
concerted effort must be made to isolate and culture magnetic bacteria with mag-
netosomes of different shapes and sizes. Likewise, studies must be conducted to
increase and optimize cell growth, the eventual aim being to provide multiple sizes
and shapes of magnetosomes for biomedical specifi cations. In this regard, recent
investigations have been conducted with MV-1, MC-1 and RS-1 strains, all of
which produce magnetosomes of various shapes. MV-1 produces larger, elongated
particles with an increased coercivity, and may be grown on a large scale, at higher
densities; moreover, the cobalt-doping of these elongated particles should increase
coercivity even further.
In the long-term approach to using magnetosomes as biomedical nanomagnetic
materials, it will be necessary to determine details of not only the biomineraliza-
tion process but also the biomineralization proteins. Having identifi ed exactly
which proteins are required, it may become possible to insert biomineralization
genes into other bacteria/cells or hosts, allowing them to produce magnetosomes
in higher yields. Alternatively, a magnetic function may be added to an already
