Magnetotactic bacteria.

This presentation is about magnetotactic bacteria which synthesized magnetic nanoparticles and the applications of nanoparticles.

1. MAGNETOTACTIC
BACTERIA FOR
NATURAL SYNTHESIS
OF MAGNETIC
NANOPARTICLES
SEMINAR REPRESENTED BY
QAMRUNNISA ABDUL WAHID SHAIKH
MSC-I (MICROBIOLOGY)
MB 601-INSTRUMENTATION AND
MOLECULAR BIOPHYSICS

2. CONTENT:
NANOPARTICLES
MAGNETIC NANOPARTICLES
MAGNETOTACTIC BACTERIA
MAGNETOSOME
SYNTHESIS OF MAGNETIC NANOPARTICLES
APPLICATIONS OF MAGNETIC NANOPARTICLES

3. NANOPARTICLES:
Nano particles are sub-nanosized colloidal structures composed of
synthetic and semi-synthetic polymers.
Size-10-100nm
Ultrafine particles
Figure : Structure of nanoparticles
The word “nano” is derived from a Greek word meaning “dwarf” or
“extremely small”.
=10
6
nm

4. MAGNETIC NANOPARTICLES:
Magnetic nanoparticles are a class of nanoparticles which
can be manipulated using magnetic field.
OR
Magnetic nanoparticles (MNPs) are those nanoparticles
(NPs) that show some response to an applied magnetic field.
Such particles consist of two components:
Iron(Fe), Nickel(Ni)
and Cobalt(Co)
Size: 1-100nm
Perform best in the size ranges of 10-20nm in various applications.

5. SYNTHESIS METHODS OF
MAGNETIC NANOPARTICLES:
Hydrothermal
MICROEMULSION
MAGNETOTAC
TIC BACTERIA
HYDROTHERMAL

6. 6
MAGNETOTACTIC BACTERIA(MTB):
Magnetic bacteria, which is known as Magnetotactic
bacteria (MTB) can produce nanosized and membrane-
bound magnetite particles with regular morphology and
size within the single-domain region under mild
conditions at normal temperature and pressure. other
words, magnetic bacteria synthesize nano bacterial
magnetic particles (BMPs).
INTRODUCTION:
Magnetotactic bacteria(MTB)
HISTORY:
• Salvatore Bellini in 1962
• Richard P. Blakemore in 1975

7. EXAMPLES OF MAGNETOTACTIC BACTERIA(MTBs):
i.Magnetospirillum gryphiswaldense strain MSR-1
ii.M. Magnetotacticum strain MS-1
iii.M. Magneticum strain AMB-1
iv.Magnetococcus sp. strain MC-1
v.Magneto-ovoid strain MO-1.
Figure :Transmission electron microscope
(TEM) images of MTB.
(A) TEM micrograph of a cell of
Magnetospirillum magneticum strain AMB-1.
(B) TEM micrograph of an magnetosome
membrane surrounding bullet-shaped
magnetite crystals.
(C) TEM micrograph of an magnetosome
chain from a Magnetococcus marinus
 MC-1 cell

8. Morphologically, metabolically, and
phylogenetically diverse group of prokaryotes.
Gram negative prokaryote.
Distributed worldwide, having been found on all
continents, and are ubiquitous in sediments of
freshwater, brackish, marine, and hypersaline
habitats.
They move by flagella.
Display Various morphologies such as rods, vibrio,
spiral,cocci and multicellular .
Some produce Fe3O4 (magnetite) others produce
Fe3S4 (greigite), some produce both.
Usually found in oxic-anoxic interference in
aquatic habitat.
CHARACTERISTICS OF MAGNETOTACTIC
BACTERIA(MTB):

9. THE EARTH’S MAGNETIC FIELD:
The Earth can be considered as a large magnet surrounded by a magnetic field. The
Earth’s magnetic field is like a dipole magnet that has north and south poles.
Geographic north pole= magnetic south pole
Geographic south pole = magnetic north pole
Moves according to the Earth’s magnetic field lines and can orient,
migrate along geomagnetic field lines.
Magnetic south pole
Magnetic north pole

10. 10
MAGNETOSOME OR MAGNETITE :
Magnetosomes are a type of vesicles that is found in the cell. This structure is surrounded by
a lipid bilayer membrane derived from the cytoplasmic membrane and consists of inorganic
crystals containing magnetic iron ie magnetite(Fe
3
O
4
) and greigite(Fe
3
S
4
).
Magnetosomes are generally organized in linear chains and orient the cell body along
geomagnetic field lines while flagella actively propel the cells, resulting in so-called
Magnetotaxis.
Magnetospirillum magneticum and Magnetospirillum sp, which have approximately 15-20
magnetosomes along the cell’s center line aligned horizontally. This line-up along the central
line creates a structure similar to a compass needle that has the magnetic moment.
Figure : structure of magnetosome

11. Electron chromatographic analysis shows that there is a filament that accompanies the
magnetosome chains, and that the magnetosomes are connected to this filament by acidic
MamJ proteins.
Figure : Magnetosomes and their
alignment on the filament
(Source: Nature
Reviews/Microbiology and American Society for
Microbiology, http://forms.
asm.org/micr obe/index.asp?bid=63469)

12. Magnetite (Fe3O4) is the main chemical component of
magnetosomes characterized by the high chemical purity,
fine grain size uniformity, and good biocompatibility, which
can be used as a new kind of nano-magnetic materials
applied in many fields of biochemistry, magnetic materials,
clinical medicine and wastewater treatment etc.
 In various electron microscopes, magnetosome
crystals of various shapes were observed in MTB, such
as cubic octagonal, bullet-shaped, prismatic and
rectangular.
Figure-Transmission electron microscopy images of several different MTB showing their
distinctive cell and magnetosome crystal compositions and morphologies.

13. 13
THE FORMATION OF MAGNETOSOMES:
The formation mechanism of magnetosomes is a complex process and Magnetosome
formation is the mineralization process under strict biochemical mechanisms
control,including four steps:
that includes the
i.Formation of magnetosome vesicles
•Taking the iron mineral into the cell
•Carrying the iron in the magnetosome vesicles and
•The control of magnetite or greigite biomineralisation within the vesicle

14. 1.Formation of magnetosome vesicles
2.Taking the iron mineral into the cell
3.Carrying the iron in the magnetosome
vesicles
4. The control of magnetite or greigite
biomineralisation within the vesicle.
Figure : Formation of magnetosome

15. Figure :Transmission electron
microscopy image
of magnetosome formation

16. PURIFICATION OF MAGNETIC NANOPARTICLES:
Culture MTBs
•Dual vessel fermentor
•Media –DMZ380
Harvest cells by
Centrifugation
5000xg
Wash pellet 3 times
with 10mM HEPES
buffer(PH:7.4) and
1mM EDTA
Resuspend pellet in
1M NaOH
Magnetic nanoparticles
were collected using a
neodymium boron
magnets
Analyze structural,
elemental and magnetic
properties of magnetic
nanoparticles
Washed with
sterile distilled
water
Stored at 4
0
C in
sterile distilled
water
Discard
supernatant
Boiled-20min

17. Figure : (a)-(c) TEM images of MTB-
NPs with different shapes
(a)Elongated prism
(b)Cubo-octahedral
(c)Bullet shape
(d)High magnification shoeing their
magnetosome membrane (MMs)
Figure : (a)-(e) TEM images of
magnetic nanoparticles.
(f)-SEM image of Fe
3
O
4

18. APPLICATIONS OF MAGNETIC
NANOPARTICLES:

19. MTB are used in magnetic hyperthermia, which is used in tumor therapy.
Magnetic hyperthermia is a method in which magnetic nanoparticles are
sent to the tumor and are heated by applying alternate magnetic fields.
The heat generated by the nanoparticles has an anti-tumor effect.
This technique can be used in the
treatment of some tumors such as in
lung cancer.
The interest in the
“magnetic hyperthermia”
by using magnetosomes for
cancer treatment has increased.
MAGNETIC HYPERTHERMIA:

20. Magnetic hyperthermia is also known as magnetic
nanoparticles mediated intracellular hyperthermia, is a
thermotherapy which involve targeting of a tumor with the
help of magnetic nanoparticles in the presence of
external magnetic field that causes production of heat
through Neel relaxationloss of magnetic nanoparticles.
Heat generation through Neel relaxation is due to rapid
changes in the direction of magnetic moments.
As a temprature of tumor cells increased within range of
hyperthermia temprature(41-46
0
C).
Tumor cells are more sensitive to heat as compared to
normal cells due to poor vascularization, so the survival
rate of tumor cells decreases drastically by increasing
temprature and at one stage the tumor cells burst.
This themotherapy specifically destroyes tumor cells
without destruction of neighbouring healthy cells.

21. There are three hyperthermia treatment
1)Local hyperthermia treatment is used to treat the small portion
of body such as tumor to heat and it requires very high
temprature
2)Regional hyperthermia is used to treat the large area of the
body such as organ, body cavity.
3)Whole body hyperthermia is used to treat matastatic
cancer(cancer which has spread within whole body.
General mechanism of hyperthermia consist of two steps
1)Prepration of magnetic nanoparticles
2)Injection of magnetic fluid carrying magnetic nanoparticles into
tumor sites.
Once the magnetic nanoparticles are entered into the cancer
cells they are heated with the help of an external localized and
alternating magnetic field. An alternating magnetic field causes
the nanoparticles within tumor tissue to vibrateand this
vibrational energy is ultimately converted into heat causing
increase in temprature and leading to destruction of tumor cells.

22. Cancer Therapeutics
Surgery, radiotherapy and chemotherapy are the key
components of cancer treatment. Chemotherapy uses
cytotoxic agents to target malignant tumours in organs or
tissues. Unfortunately, chemotherapy is expensive and in
addition to cancer affects normal cells leading to numerous
side effects.
By using nanoimaging and nanodrug delivery systems
cancer cells can be selectively targeted thus reducing
undesired systemic drug toxicity. Nanoparticle-based drug
delivery systems, especially liposomes , have already been
approved by the US Food and Drug Administration (FDA)
for the treatment of specific cancers and continue to be
developed in pre-clinical research.

The most widely used MNPs are magnetite Fe
3
O
4
 and
maghemite -Fe
γ
2
O
3
. Pure metals such as Fe, Ni and Co,
ferrites of the form MeO@Fe
2
O
3
 (Me = Mg, Zn, Mn, Ni, Co,
etc) may be also used to prepare MNPs.

23. Magnetic nanoparticles appear to be very appropriate for
drug delivery.
MNPs need to be coated with surfactants or polymers
(e.g. dextran, polyethylene glycol) to stabilise them and
attach functional groups to their surfaces.
The functionalisation is used to bind the appropriate
molecules, such as anti-cancer drugs or antibodies, to the
nanoparticles.
Surfactants and polymers increase also the
biocompatibility of the nanoparticles. Indeed, without this
shield MNPs could not resist opsonisation (i.e. the process
by which an exogenous molecule is tagged for destruction
by phagocytosis) when introduced in vivo.

Another advantage of these nanoparticles is that they are
nontoxic and well tolerated in vivo, independently of the
administration routes.
Drug delivery:

24. Nanoparticles are already widely used in drug delivery,
offering to transport various agents such as antimicrobial
molecules, genes, proteins and anti-cancer drugs.
Many chemotherapeutic drugs and siRNA treatments have
already been loaded in different nanoparticles and have
demonstrated a great efficacy against different types of
cancers .
 While cancer drug delivery via MNPs is seen in its infancy
(to date, only a few reports with in vivo results have been
published), it has great potential due to the numerous
advantages of MNPs.
 For example, recently, Maeng et al.  have shown promising
results MNPs loaded with doxorubicin (a potent anti-cancer
agent) against liver cancer in rat and rabbit cancer models.
Gene therapy represents an alternative to anti-cancer
drug treatment for cancer. Indeed, this therapy could target
directly genes and regulate the altered gene expression,
which is involved in carcinogenesis.

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