Full text of DOI:10.1109/20.908952

IEEE TRANSACTIONS ON MAGNETICS, VOL. 36, NO. 5, SEPTEMBER 2000
3721
Aggregation of Blood Platelets in Static Magnetic
Fields
M. Iwasaka, Member, IEEE, M. Takeuchi, and S. Ueno, Member, IEEE
Abstract—We investigated the effects of intense magnetic fields
on the blood platelet aggregation process with and without static
magnetic fields of up to 14 T. A rabbit plasma and collagen mixture
was used as the model system for a wounded blood vessel. Platelet
aggregation was activated by the stimulation of acid soluble col-
lagen. The platelet aggregates in strong magnetic fields were larger
than the aggregates in an ambient field. An optical transmission of
blood plasma during platelet aggregation also indicated that strong
magnetic fields enhanced blood platelet aggregation in plasma.
Index Terms—Collagen, fibrin, magnetic orientation, platelet ag-
gregation, static magnetic field.
I. INTRODUCTION
OTH FIBRIN and platelets have important roles in the
blood coagulation process. Fibrin polymers are diamag-
B
netic materials that orient in a magnetic field [1]. In the course
of the polymerization process, the fibrin fibers orient parallel to
the magnetic fields when a magnetic field of intensity 10–20 T is
applied. It is also reported that blood platelet and erythrocyte ex-
hibit magnetic orientation by the parallel alignment of its saucer
plain to the magnetic field direction [2], [3].
Collagen fibers orient perpendicular to the magnetic field di-
rection [4], [5]. The suggested mechanism of the magnetic ori-
entation of proteins and blood cells is due to the diamagnetic
anisotropy of peptide bonds and lipid membrane [2], [3], re-
spectively. The blood coagulation system, which is shown in
Fig. 1(a), consists of materials that orient parallel and perpen-
dicular to the direction of magnetic fields. Thus, slight modu-
lation of blood coagulation processes under magnetic fields of
tesla order is expected. XII, X, et al. indicate factors in a blood
coagulation system.
In the blood vascular system, endothelial cells are injured,
collagen fibers are exposed to blood. Collagen then stimulates
blood platelets into initiating platelet aggregation, as shown in
Fig. 1(b).
In the present study, we investigated the effects of intense
magnetic fields on blood platelet aggregation by measuring the
time course of the optical transmission of blood plasma during
platelet aggregation with and without static magnetic fields of
up to 14 T.
Fig. 1. Blood coagulation system consisting of materials which orient under
strong magnetic fields. (a) A simple illustration of the main connection in blood
coagulation system. (b) Encounter of blood platelets with collagen of blood
vessel.
II. METHODS
We used a horizontal type of superconducting magnet, which
produced magnetic fields of up to 14 T at its center. We eval-
uated the plasma coagulation process by using both an optical
microscopic observation and the optical transmission measure-
ment system.
The optical transmission measurement system has an external
optical cell holder in the superconducting magnet’s bore. Warm
water was introduced to the inside of cell holder’s wall, and
circulated between a water bath and the cell holder, as shown
in Fig. 2. Blood plasma and red blood cells were centrifugally
separated from 10 ml of rabbit blood at 1000 rpm for 15 min.
The concentrated platelet suspension of
1 000 000 of platelets. Calcium chloride was added to the plasma
to increase its concentration to be 5 mM. l of the solu-
tion was moved to a plastic-type optical cuvette, and the cuvette
l contained about
Manuscript received February 1, 2000. This work was supported in part by
Nissan Science Foundation, and grants from the Ministry of Education, Science was inserted into the external optical cell holder in the super-
and Culture of Japan.
The authors can be reached at e-mail: {iwasaka; ueno}@medes.m.u-
tokyo.ac.jp.
conducting magnet’s bore.
After 10 minutes of incubation of the plasma solution at
Publisher Item Identifier S 0018-9464(00)08655-6.
37 C,
l of collagen with a concentration of 3 mg/ml was
0018–9464/00$10.00 © 2000 IEEE

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IEEE TRANSACTIONS ON MAGNETICS, VOL. 36, NO. 5, SEPTEMBER 2000
(a)
Fig. 2. Real time optical transmission measurement system for platelet
aggregation under magnetic field exposures.
added to plasma. Platelets in the plasma were stimulated by
collagen, and plasma coagulation started.
III. RESULTS AND DISCUSSION
After incubation at 37 C for 600 sec, the plasma was
extracted from a cuvette, and moved to a petri dish for op-
tical microscopic observation. Fig. 3 shows the photographs
(phase contrasted optical microscopic images) of aggregating
platelets with and without 14 T magnetic field exposure after
about 660 sec of incubation. A control sample in the ambient
earth’s magnetic field [Fig. 3(a)] showed no visible aggregated
platelets.
(b)
Fig. 3. Optical microscopic observations of aggregating platelets. (a) without
magnetic field exposure, (b) with magnetic field exposure at 14 T.
On the other hand, a sample with 14 T magnetic field expo-
sure showed a large quantity of aggregated platelets.
We also carried out the measurement of an optical transmis-
sion change in plasma during platelet aggregation and following
fibrin gel formation. Fig. 4 shows the time sequences of a plasma
clot formation that was initiated by the stimulation of blood
platelet by collagen at 0 sec. Prior to the collagen addition, the
plasma was incubated for 10 minutes at 37 C. The vertical line
shows the optical transmission of the plasma at 600 nm.
It was observed that the transmission started to increase at
500–2000 seconds after the addition of collagen. The distinct
effects of 14 T magnetic field exposure were the rapid increase
in the optical transmission and the enhancement of transmis-
sion intensity. It was considered that an abrupt increment in the
optical transmission with 14 T exposure at 2000 seconds origi-
nated from the movement of large clots of platelet aggregation.
After the transmission reached the maximum level, it began
to decrease. Optical microscopic observation confirmed the ev-
idence that platelet aggregation occurred under 14 T. The in-
crease in transmission was the result of platelet aggregation. The
particle of aggregated platelet with magnetic field exposure was
larger than the particle without exposure.
Fig. 4. Time course of a plasma clot formation that was initiated by the
stimulation of blood platelet by collagen.
transmission periods. Plasma contains fibrinogen molecules,
which change to fibrin monomers and fibrin monomers poly-
merize to form fibrin fiber network.
The fibrin polymerization occurred after platelet aggregation,
and the sample became a turbid gel when the fibrin polymeriza-
tion was proceeded. The results show that the decrease in trans-
mission in Fig. 4 was due to fibrin polymerization.
It is known that fibrin polymerization occurs after platelet
As shown in Fig. 5, the maximum change of transmission
aggregation. We also observed the samples during decreasing under magnetic field exposure was significantly enhanced. The

IWASAKA et al.: AGGREGATION OF BLOOD PLATELETS IN STATIC MAGNETIC FIELDS
3723
Magnetic field exposure can possibly regulate an excessive
rate of fibrinolysis in the blood vascular system to a normal and
balanced state that emphasizes a rate of blood coagulation.
IV. CONCLUSION
The platelet aggregation that was formed under a magnetic
field at 14 T was larger than the control sample.
The optical transmission of platelet suspension increased
during the initial period of the platelet aggregation. Magnetic
fields of 8 T and 14 T emphasized the increase in optical
transmission.
We concluded that the platelet aggregation, which was initi-
ated by collagen stimulation, was enhanced by magnetic field
exposure of up to 14 T.
Fig. 5. Maximum change in light transmission with magnetic fields of 8 T,
14 T, and ambient magnetic field (0 T).
maximum change of transmission increased proportional to the
magnetic flux density.
A possible mechanism of the observed phenomena, the
enhancements of platelet aggregation under magnetic fields of
14 T and 8 T, is the magnetic orientation of platelet with its
saucer plane directed parallel to a field direction. An adhesive
interaction of oriented platelets should be different from
randomly rotating platelets.
ACKNOWLEDGMENT
The authors would like to thank Dr. H. Tsuda for her helpful
suggestions.
A
diamagnetic torque force acting on intracellular
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significant diamagnetic anisotropy and easily orient under
magnetic fields [2]. Conformational change and redistribution
of micro-tubules influence changes in platelet shape.
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