Materials Sciences and Applicatio ns, 2011, 2, 1317-1321
doi:10.4236/msa.2011.29179 Published Online September 2011 (
Copyright © 2011 SciRes. MSA
Functionalization of Cobalt Ferrite Nanoparticles
with Alginate Coating for Biocompatible
Prasad M. Tamhankar, Aparna M. Kulkarni, Shrikant C. Watawe*
Lokmanya Tilak Institute of Postgraduate Teaching and Research, Gogate Jogalekar College, Ratnagiri, Maharashtra, India.
Email: *
Received January 30th, 2011; revised March 28th, 2011; accepted April 11th, 2011.
The soft magnetic materials have potential applications in the field of bioengineering as carriers for targeted drug de-
livery. The magnetic properties, particle size after coating, Curie temperature and its biocompatibility are important
parameters for the synthesis of materials. In the present communication cobalt ferrite nanoparticles have been synthe-
sized using co-precipitation method and coated with sodium alginate. The X-ray diffraction and infrared spectroscopic
measurements have been used to confirm the ferrite structure formation and coating of the samples with alginate. The
SEM micrographs have been used to confirm the particle size which is found to be 45 nm before coating and 78 nm
after coating. The saturation magnetization obtained using the hysteresis data for the uncoated cobalt ferrite sample is
19.8 emu/gm while for the coated sample it reduces to 10.2 emu/gm. The AC susceptibility measurements indicate SP
structure for the uncoated samples with Curie temperature less than 100˚C. The thermo gravimetric measurements have
been used to estimate the amount of alginate coating on the sample and it has been correlated with retention of mag-
netic properties after coating. The value of saturation magnetization reduces after coating due to mass reduction of
magnetic material in the sample in accordance with the TGA measurements.
Keywords: Nanomagnetic Materials, Biocompatible Coating, Co-Precipitation Method
1. Introduction
The soft magnetic materials have potential applications
as carriers for targeted drug delivery but there are limita-
tions due to their toxicity [1-8]. The switching property is
advantages for the hyperthermia and drug release me-
chanism. Coating these nanoparticles with biocompatible
polymeric material is the area of research. Some critical
parameters in the synthesis include the size of the mag-
netic nanoparticles. Different methods have been used by
researchers to synthesize uniform sized nanoparticles one
of them is the co-precipitation method. The biological
applications of these particles require the size to be in the
range of 30 to 50 nm and the coating thickness to in-
crease the size to 70 to 80 nm [9]. At the same time there
should be retention of ambient magnetic property so that
they can be used for switching applications [10]
For targeted drug delivery the external magnetic field
gradients can be used to direct the functionalized mag-
netic particles to the specific site, retain and subsequently
remove them. The in vivo route inherently has certain
limitations which can be overcome by modifications in
techniques and materials used in the process [11-15]. The
coated magnetic nano particles are required to exhibit
magnetic properties, remain stable, well dispersed and
not aggregate to inhibit the blood flow. Once injected,
they are opsonized [16] and the reticulo-endothelical
system of the body, mainly sets the macrophage cells of
the liver into phagocytic activity, where these nanoparti-
cles are taken up due to hydrophobic surface of the cells.
Thus the surface of the magnetic nanoparticles for its in
vivo usage require surface modifications to ensure they
are non toxic, biocompatible and stable to the reticulo-
endothelical system of the body. Considering the hydro-
phobic and hydrophilic interaction during opsonization
the coating of polymer materials such as dextran, poly-
vinyl alcohol (PVA), polyethylene glycol (PEG), poly-
ethylene oxide (PEO), oleic acid has been reported [7].
In the present communication the cobalt ferrite nano-
particles have been coated with alginate. The choice of
Functionalization of Cobalt Ferrite Nanoparticles with Alginate Coating for Biocompatible Applications
alginate is because alginic acid is composed of residue of
D-Mannuronic acid, L-Glucoronic acid. The molecule
consists of chains of D-Glucoronic acid units joined by
B-14 Glycosidic linkages. The chain length is long and
varies with the method of preparation. The molecular
weight and viscosity measurement suggest molecules of
from 220 to 860 units. The alginate absorbable haemo-
static dressing is reported to be non toxic and non irritant.
They have advantage over oxidized Cellulose, which
include selective rate of absorption, Sterilization by auto
cleaning or dry heat and compatibility with antibiotics
such as penicillin. They may be used internally in neuro-
surgery, dental surgery to be subsequently absorbed. Ex-
ternally they may be used (e.g. for burns or sites from
which skin graft have been taken) to arrest bleeding and
form a protective dressing which may be left or later
washed away with sodium citrate solution. Protective
films of calcium alginates may also be used by painting
the insured surfaced with sodium alginate solution and
then spraying it with calcium chloride solution. Alginate
is insoluble in water and most of the organic solvents
Considering the above applications of alginate the
coating of magnetic nanoparticles has been carried out
and analyzed using the XRD and IR. The SEM micro-
graphs have been used to confirm the particle size while
the thermo gravimetric measurements (TGA) have been
used to estimate the amount of alginate coating on the
sample and it has been correlated with retention of mag-
netic properties after coating.
2. Experimental
Ferrite nanoparticles were synthesized using controlled
co-precipitation method in which AR Grade metal chlo-
rides were used as starting agents, taken in proper molar
proportions, in aqueous medium and alkalized using
strong alkali 1.5 M NaOH, adding it drop by drop with
constant stirring on mechanical stirrer till the reaction is
complete at constant temperature of 25˚C to obtain the
required size of the particles. The obtained precipitate
was filtered through filter paper and washed several
times with deionised water and dried in oven at 80˚C for
2 hours to obtain fine ferrite powder.
For coating of the ferrite powder the 0.1M solution of
Sodium Alginate CaCl2 was prepared in deionised water.
Then 2gms of ferrite powder was mixed with sodium
Alginate and CaCl2 solution in 1:1 proportion stored over
night and filtered to obtain precipitate which was dried
for 2 hours at 80˚C in oven.
The characterization was carried out using PHILIPS
(PW3710) X-ray diffractometer with Cu Kα radiation (λ
= 1.5424 A.U.). The parameters chosen for measurement
were 2θ of 0.5˚ and 2θ range from 20˚ to 90˚. Approxi-
mately 20mg of the sample was sprinkled onto a low
background quartz XRD holder coated with a thin layer
of silicone grease to retain the sample. The IR spectro-
graphs were carried out on SHIMADZU (FTIR – 8400 s)
spectrometer in the wavelength range 400 cm1 to 2000
cm1. Each spectrum was obtained by averaging 30 in-
terferograms with resolution of 2 cm1. Pellets for FT-IR
analysis were prepared by mixing the samples with spec-
troscopic grade KBr powder. The SEM micrographs
were taken on JEOL-JEM-6360 microscope. The TGA/
DTA measurements were carried out using UNIVER-
SAL V2 4F TA instrument in the Nitrogen atmosphere at
the rate 10˚C/min. The magnetization measurements
were carried out on Magnets make hysterisis loop tracer
using magnetic field of 100 Gauss.
3. Results and Discussion
Figure 1(a) and (b) show the XRD patterns for uncoated
and alginate coated cobalt ferrite. The peaks on the XRD
patterns were indexed in the light of natural spinal struc-
ture MgAl2O4. According to spinal structure the planes
that diffract x-rays are (220), (311), (400), (422), (511)
and (440). For spinel ferrite the (311) plane line is in-
tense line. The observed reflections in the present case
are also similar to these. The sample exhibits cubic spinal
structure, the absence of extra-lines in the present pat-
terns confirms single phase formation of the ferrites by
completion of solid state reaction at much lower tem-
perature then the conventional sintering method. The
broadening of the line at half height, δ, was related to the
average diameter DRX of the particles according to the
law DRX = 0.9 λ/δ(θ) cos θ, where λ is the wavelength of
the beam and θ is the Bragg angle. The average crystal-
lite size was calculated on the main peak, i.e., the (311)
reflection peak. The lattice parameters and the particle
sized estimated using the XRD data were found to be
8.325 Å and 46 nm respectively. The values of lattice
parameter are found to be in agreement with the reported
values for the uncoated ferrites [23]. The particle size is
mainly dependent on the method of preparation and the
co-precipitation method used for the synthesis is found to
be useful to obtain ferrite particles in the required size
range. The XRD pattern retains peak pattern after coating
indicating that the ferrite structure is retained after coat-
Figures 2(a) and (b) depict the IR spectrographs for
the cobalt ferrite and alginate coated cobalt ferrite re-
spectively. The IR spectra for uncoated cobalt ferrite
shows two characteristic peaks ν1 at 430 cm1 and ν2 at
525 cm1, which have been attributed to the intrinsic vi-
brations of the tetrahedral (Td) and octahedral (Oh) coor-
dination compounds and lattice vibrations of E-symmetry
[24,25]. The IR spectra for the coated sample shows peak
Copyright © 2011 SciRes. MSA
Functionalization of Cobalt Ferrite Nanoparticles with Alginate Coating for Biocompatible Applications1319
20 30 40 50 60 70 80 90
alginate coated Co ferrite
Diffraction angle
20 30 40 50 60 70 80 90
uncoated Co ferrite
Diffraction angle
Figure 1. X-ray diffractograms for uncoated and alginate
coated cobalt ferrites.
05001000 1500 2000 2500 3000 3500 4000 4500
60 alginate coated particles
wavenumber (cm-1)
300 400 500 600 700 800 9001000
uncoated particles
wavenumber (cm-1)
Figure 2. IR spectrograph for uncoated and alginate coated
cobalt ferrite.
at 3410 cm1 which is attributed to the O-H Stretching
vibrations while at 3000 cm1 to the Symmetric C-H
Stretching vibrations. The peak at 1697 cm1 and 1622
cm-1may be attributed to the C=O and H-O-H bending
vibrations respectively. The peak at 1251 cm1 is attrib-
uted to the C-O week bond due to surfactants while 870
cm1 to the CH2 rocking vibrations. The peaks at 570
cm1and 480 cm1 to the Tetrahedral Metal & Oxygen
Stretching and Octahedral Metal Oxygen Stretching vi-
brations respectively [7]. The shift in characteristic peak
towards higher wave number after coating may be attrib-
uted to the Doppler shift due to coating material on the
ferrite material. The peaks correspond to the alginate
structure, confirming the coating of the ferrite powder.
Figures 3(a) and (b) depict the microstructure of the
uncoated and coated cobalt ferrite samples respectively.
The micrographs have been taken on the powder samples
and the particle size determined using line intercept
method which is 42 nm for uncoated ferrite powder and
78 nm after alginate coating. The XRD analysis also
shows the value in the same range. The smaller particle
size may be attributed to the method of preparation of the
samples. The increase in particle size for coated samples
is as expected. The particle size obtained is suitable from
Figure 3. (a) SEM micrograph of cobalt ferrite; (b) SEM
micrograph of alginate coated cobalt ferrite.
Copyright © 2011 SciRes. MSA
Functionalization of Cobalt Ferrite Nanoparticles with Alginate Coating for Biocompatible Applications
the intended application point of view.
Figure 4 depicts the TGA/DTA plot of alginate coated
cobalt ferrite sample. The plot has been used for estima-
tion of percentage of coating material on the magnetic
material. It has been used to estimate the amount of
magnetic material per unit mass of the coated sample and
correlated with the saturation magnetization of the coated
sample. The values of saturation magnetization for un-
coated and coated samples are 94.4 emu/gm and 32.8
emu/gm respectively [26]. The lower values for the
coated samples may be attributed to the percentage re-
duction of ferrite material in the sample after coating and
the surface bonding of coating material with free oxygen
ions at the surface in the ferrite material. The amount of
magnetic property retained per unit Volume in the coated
sample is in the range which may be used in biocompati-
ble applications. Since below which it behaves as a hard
magnet making it unsuitable for switching applications
[9]. Additionally there is particle size at which stabilizing
magnetic energy of the particle is equal to thermal energy
of the environment making it unsuitable for such applica-
tions. Therefore the size of magnetic nanoparticles is of
prime importance from the point of view of application.
4. Conclusions
Uniform sized magnetic nanoparticles can be synthesized
using the co-precipitation method and coated with algi-
nate. The retention of requisite amount of magnetization
after coating ensures its possible applicability in biologi-
100 200 300400 500
Figure 4. TGA/DTA plot for alginate coated cobalt ferrite.
cal and in vivo applications.
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