Journal of Biomaterials and Nanobiotechnology, 2011, 2, 426-434
doi:10.4236/jbnb.2011.24052 Published Online October 2011 (http://www.SciRP.org/journal/jbnb)
A Novel Synthesis Route to Produce Boron Nitride
Nanotubes for Bioapplications
Tiago Hilário Ferreira, Paulo Roberto Omelas da Silva, Raquel Gouvêa dos Santos,
Edésia Martins Barros de Sousa*
Nanotechnology Service, Nuclear Technology Development Center (CDTN)/CNEN, Avenda Presidente Antônio Carlos, Belo
Horizonte, Brazil.
Received June 27th, 2011; revised July 22nd, 2011; accepted August 12th, 2011.
ABSTRACT
Nanostructures of boron nitride have attracted a great deal of interest due to their potential applications that comprise a
broad range of topics, including biomedical technology, since it presents good chemical stability and suggests good bio-
logical inertia. This paper reports a facile and effective synthesis based on CVD process with new conditions to produce
boron nitride nanotubes in higher amount using boron powder, ammonium nitrate and hematite as catalysts in tubular fur-
nace, without using extreme conditions. The characterization of the material was carried out by Fourier transformed infra-
red spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis, scanning electron microscopy (SEM) and
transmission electron microscopy (TEM). From the results, it was possible to verify the production of a hexagonal BN
nanotube filled with Fe nanoparticles. It was possible to understand the reactions involved in synthesis process, and also
confirm the formation of hexagonal boron nitride nanotubes with iron nanoparticles as catalysts. Depending on the final use,
samples need to be purified to analyze their unique properties in some bioapplications. In the other hand, sometimes BNNTs
containing Fe nanoparticles have potential for use in therapeutic drug, gene and radionuclide delivery, and radio frequency
methods for the catabolism of tumors via hyperthermia. In this sense, some application-related studies on BNNTs such as
biocompatibility tests have also been investigated in both pure and BN nanotube filled with Fe.
Keywords: Boron nitride, Nanotubes, Biocompatibility Testing, Bioapplications
1. Introduction
In the last decade, significant research efforts have been
devoted to achieve materials with well-defined nanostru-
ctures for wide range of applications [1,2]. Nanotubes
materials are currently a field of intensive activity due to
their high potential in a very broad range of applications
due to their outstanding mechanical, electronic, optical,
and thermal properties, and in particular, their high as-
pect ratio and propensity to functional modification for
biomedical applications.
After the discovery of carbon nanotubes (CNT) it has
been suggested that carbon is not a unique material being
able to form nanotubes. In this sense, boron nitride ap-
pears as a potential material for this class in view of the
structural similarity of graphite and bulk BN [3].
Hexagonal boron nitride (h-BN) is well known as one
important ceramic material with outstanding thermal and
electrical properties. Furthermore it has excellent chemi-
cal stability, good resistance to corrosion, low density
and high melting point [4]. These characteristics make
h-BN an attractive candidate for a wide range of techni-
cal applications [5,6]. In the field of biomedical techno-
logy its use as nanostructured materials has been pro-
posed due to its unique properties that suggest a good
biological inertia.
Nowadays, there is a fast growth of the number of
studies on boron nitride nanotubes, BNNT, aiming at,
among other aspects i) the investigation of the synthesis
parameters [7], ii) characterization of the physical pro-
perty in general [8], iii) evaluation and improvement of
the stability by introducing other compounds [9], iv)
surface modification [10], and v) biological behaviors
[11].
Regarding to the synthesis parameters, since the dis-
covery of CNTs [12], research into new and improved
BNNT synthetic techniques has been towards enhance
yield, obtain better nanostructure quality, and controlled
chirality and diameter. Recently, many studies have been
reporting the preparation of nanostructures of boron ni-

A Novel Synthesis Route to Produce Boron Nitride Nanotubes for Bioapplications427
tride with special morphologies, such as nanotubes [13],
nanocapsules [14], nanocages [15], porous structures [16]
and hollow spheres [17]. Traditionally, h-BN was pre-
pared by the classical high-temperature synthesis routes,
including reaction of B2O3, boric acid, or borax with
carbon and nitrogen/ammonia and urea at temperature
around 2000˚C [18]. On the other hand, for special BN
nanostructures synthesis, laser ablation, chemical vapor-
phase, carbothermal reduction of B2O3 and B4C and
other methods have been developed [19]. Most of these
methods cannot meet the need of high yields, and there-
fore, the understanding on its synthesis is still a chal-
lenging subject. Moreover, BNNT obtained from differ-
ent synthetic methods has different physical properties.
The quality, quantity, and type of nanotubes synthesized
depend on the synthetic method used.
Depending of the synthesis route, the growth of BNNTs
often requires the assistance of metal catalysts, predomi-
nantly, iron group metals Fe, Co, and Ni. However,
similar to the case of CNTs, the as-synthesized BNNTs
often contain impurities such as metal catalyst particles
or boron oxide layers on the nanotube surfaces, which
need to be removed, depending on the final use. When
associated with metallic nanoparticles that have magnetic
properties, BNNT obey Coulomb’s law and can be ma-
nipulated by an external magnetic field. Therefore it may
act as a modulator of the microvascular tone. This regu-
lation is manifested primarily in the smaller resistance
arterioles, resulting in substantial modulation of mi-
crovascular flow resistance [20]. Moreover, these nano-
particles also can be coated with biological molecules to
make them interact or bind to a specific target. Therefore,
they have potential for use in therapeutic drug, gene and
radionuclide delivery, radio frequency methods for the
catabolism of tumors via hyperthermia, and contrast en-
hancement agents for magnetic resonance imaging ap-
plications [21].
The biocompatibility and bio-applications of inorganic
nanomaterials have become hot topics in recent years.
Ciofani et al. [22] initiated the first biocompatibility tests
on BNNTs. In their experiments, PEI-coated BNNTs
were used for in vitro tests on a human neuroblastoma
cell line. The results indicated very good cell viability up
to a concentration of 5.0 mg/ml of BNNTs in the cell
culture medium. Chunyi Zhi et al. [23] presented an
overview of the up-to-date developments in boron nitride
nanotubes, including biocompatibility and bioapplica-
tions. According to them, due to natural complexity of
nanomaterials, frequently, the discrepancies in results are
obtained during different experiments on the same kind
of nanomaterial. Therefore, we agree with them that
more experiments should be performed on BNNTs with
different preparation histories to confirm their intrinsic
properties.
Considering the special properties of BNNT useful for
various structural and biomedical applications due to the
presence of small Fe particles as production residuals, we
have explored in this work a special and facile synthesis
route to obtain nanostructures of boron nitride with re-
markable yield. Indeed, we investigated previously the
cytotoxicity of both samples (as-prepared and containing
Fe-nanoparticles) by hemolytic tests and MTT assays for
pure BNNT. To accomplish this purpose, hematite na-
noparticles, boron powder and ammonium nitrate were
mixed and BNNT were formed by using an annealing
method. The structural properties of the samples have
been investigated using different techniques. The results
indicate that both pure and Fe-BNNT is a potential nano-
material for bioapplications.
2. Experimental
2.1. Synthesis
In this study, BN nanostructures samples were prepared
using amorphous boron powder, ammonium nitrate
(NH4NO3) of a purity of 95% or better and hematite
(Fe2O3) of a purity of 95% and particle size less than 50
nm. The powders were mixed well in a weight ratio of
15:15:1, respectively. An alumina boat containing the
powder mixture was placed in tubular furnace and heated
up to 550˚C without gas flow. This temperature was kept
constant for one hour. After that, the temperature was
slowly raised until 1300˚C in a nitrogen gas flow. Nitro-
gen pressure was 0.2 Pa, and its gas flow was 50 sccm.
After one hour in this temperature ammonia gas flow
was introduced for one hour followed by nitrogen gas
flow until the complete cooling.
The presence of impurities such as metal catalyst par-
ticles can be interesting or not, depending on the applica-
tion. If the magnetic properties is essential for the pro-
posed final use, like drug targeting or hyperthermia,
these nanoparticles exert great influence on the perform-
ance of the BNNT. However, sometimes they need to be
removed to enable the better application and exploiting
the properties of this material. The metal particles can be
found scattered or in the form of small clusters. Consid-
ering these ambiguous behavior, both as prepared and
purified samples were investigated in this work. So, to
purify BN nanotubes it was chosen the chemically modi-
fied techniques described in the literature [24]. The puri-
fication was based on washing the sample with HCl so-
lution (3 M) at 90˚C for 10 minutes, and then the sample
was collected by filtration and dried at 40˚C.
2.2. Characterization
Samples as prepared and purified were characterized by
Fourier-transform infrared spectroscopy (FTIR), X-ray
diffraction (XRD), thermogravimetric analysis (TGA),

A Novel Synthesis Route to Produce Boron Nitride Nanotubes for Bioapplications 428
scanning electron microscopy (SEM), and transmission
electron microscopy (TEM). The XRD patterns were
obtained using a Rigaku Geigerflex-3034 diffractometer
with a Cu-K tube. FTIR measurements were conducted
in a Perkin-Elmer 1760-X spectrophotometer in the range
4000 - 400 cm–1 at room temperature using KBr pellets.
TGA measurements were performed by Shimadzu TGA
50WS with temperature ranging from 25˚C to 900˚C.
Approximately 3.0 mg of start mixture and final sample
were analyzed using a heating rate of 10˚C·min–1, with
nitrogen (N2) atmosphere flow of 20 mL·min–1 and pla-
tinum cell open. SEM characterization was performed in
a scanning electron microscope (JEOL JSM, 840A) op-
erating at 15 kV. TEM characterization was performed
through a Tecnai—G2-20-FEI 2006 electron microscope
with an acceleration potential of 200 kV.
2.3. Biocompatibility Tests
2.3.1. Hem oly t i c Tests
For hemolytic tests, triplicates samples of as prepared
and pure BNNT were prepared in suspensions of phos-
phate buffer solution (PBS) at concentrations of 15.0,
32.5, 45, 62.5, 90 and 125 μg/mL. The samples were
incubated with 300 μL of blood to a final volume of 1.5 mL
for one hour; then, the solution was centrifuged for 10
minutes to 1000 rpm, and the supernatant was read at
540 nm on a spectrophotometer UV-Vis (Shimadzu).
PBS and Triton 5% v/v were used as negative and posi-
tive control, respectively.
2.3.2. Cytoto x i ci ty Studi es
Malignant U87 (wild-type p53), T98 (mutant p53) glio-
blastoma, MCF-7 adenocarcinoma mammary gland cells
and normal MRC-5 (diploid) fibroblast lung cells were
maintained in Dulbecco’s Modified Eagle’s Medium
(DMEM-Gibco), supplemented with 10% fetal bovine
serum and antibiotics (50 U·mL–1 penicillin/50 mM
streptomycin), in a water jacketed incubator with atmos-
phere of 5% CO2/95% air at 37˚C. The cytotoxic effects
were quantified using a 3-(4,5-dimethiol-2-thioazolyl)-2,
5-diphenyl tetrazolium bromide (MTT) colorimetric as-
say [25]. Briefly, cells were seeded at 1500 cells/well in
96-well flat-bottomed plates and incubated for 24 h.
Cells were treated with BNNT with increasing concen-
trations of 0.1; 10.0; 50.0; 100.0; 200.0 µg/mL previ-
ously dispersed in PBS and DMEM. Following 48 h of
incubation at 37˚C, MTT reagent was added to each well
and incubated for 4h. After this, dimethyl sulfoxide
(DMSO) was added to each well to dissolve formazan
crystals and absorbance was measured at 570 nm. All
tests were performed in triplicates with full agreement
between the results. The fraction of surviving cells in
treated groups was calculated as a percentage of control
group (incubated only in DMEM), and the absorbance in
control considered 100% survival.
3. Results and Discussion
3.1. Synthesis
The knowledge of the chemical reaction mechanism is
important to understand how reaction of -Fe2O3 with B
proceeds to formation of the BN nanotubes. They can be
described in Equations. (1) and (2):


 
43 23
23 2
10Bs 2NHNOsFeOs
4BNs3BOg 4Hg 2Fes




(1)






23 32
3B Og6NHg6BNs9HOg (2)
During the reaction process, NH4NO3 was decom-
posed into NH3 and HNO3 at low temperature. NH3 dis-
sociated into active nitrogen vapor and H2 gas at high
temperature. At the same time, B vapor were formed and
reacted with Fe2O3 to produce metallic Fe and B2O3. So,
the vapor is likely to contain boron oxide phases gene-
rated from the reaction of boron with Fe2O3. After that,
Fe-filled boron nitride nanotubes began to grow on the
surface of metal catalyst, as described in Equation (1).
However, the proposed conditions do not favor the con-
sumption of all boron from the reaction mixture. To
complete this, the presence of an ammonia flow directs
the reaction to formation of boron nitride remains, ac-
cording to Equation (2).
Figure 1 shows the FTIR spectra of samples treated at
550 and 1300˚C. The presence of the band centered at
540 cm-1 which corresponds to strain on the O-B-O, and
the bands centered at 760 and 1190 cm–1 related to B-O
strain, indicating the presence of boron oxide (B2O3 and
B2O) can be observed for the samples heated at low
temperature. We also observed the presence of a small
band centered at 640 cm–1 which can be ascribed to the
vibration of Fe-O bond, which is typical of hematite
phase (Fe2O3).
The sample treated at 1300˚C presented characteristic
bands of B-N. The most important feature displayed in
the spectra is the strong asymmetric band centered at
1380 cm–1, which corresponds to the bond B-N stretch,
along with a less intense band at 790 cm–1 ascribed to
B-N-B bond. It is noteworthy that this technique pro-
vides important data to characterize the phase h-BN,
since it is possible to distinguish sp2 bonds of hexagonal
h-BN phase samples and sp3 of cubic phase c-BN. Ac-
cording to Hao and colleagues [26] bonds sp2-type of
h-BN are thermodynamically stable under the synthesis
conditions of this work, while for the formation of sp3
bonds typical of c-BN, there is a kinetics barrier of for-
mation. Other authors have presented similar results in
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A Novel Synthesis Route to Produce Boron Nitride Nanotubes for Bioapplications429
(a)
(b)
Figure 1. (a) Infrared spectrum of the samples treated at
550 and 1300˚C; (b) Expanded infrared spectrum.
which the formation of h-BN occur around 1380˚C [27,
28]. Peaks in 1096 and 1166 cm–1 are due to the forma-
tion of c-BN phase and they were not found in the sam-
ple treated at 1300˚C.
Figure 2 shows the XRD patterns of the samples
treated at 550˚C and 1300˚C. The peaks at 2θ = 14.55°,
2θ = 27.76°, 2θ = 30.59° and 2θ = 57.55° are relative to
the boron oxide (B2O3) (JCPDS, N°. 41 - 624) present in
curves of samples treated at 550˚C. The predominance of
the boron oxides phases at this temperature suggests that
the oxygen present in the initial mixture, derived from
the Fe2O3 and from the environment, favors initially the
formation of B2O (intermediate compound), and after
B2O3. The formation of boron oxide (B2O3) is of great
importance in this chemical process because it is the
precursor for the synthesis of h-BN. It is known that the
B2O3 has a low vapor pressure compared to elemental
boron [29] and this allows the presence of boron in a
gaseous form at a lower temperature, in these synthesis
conditions. In the sample treated at 1300˚C is possible to
identify the presence of typical peaks of h-BN at 2θ =
26.75°, 2θ = 41.58°, 2θ = 50.16° and 2θ = 75.86°
Figure 2. XRD pattern of the samples treated at 550 and
1300˚C.
(JCPDS, N°. 9 - 12). Peaks for metallic iron and some
peaks with very low intensity relative to the boron oxide
B2O3 also can be identified. In addition, the presence of
this paramagnetic iron phase was supported by Moss-
bauer spectroscopy at room temperature (not showed
here). No noticeable peaks of other impurities, such as
Fe2O3, were detected in this pattern. This indicates that
the catalyst particles inside the BN nanotubes are α-Fe
metal particles.
The TGA curve of sample weight changes as a func-
tion of heating temperature is shown in Figure 3. A
comparison between reaction mixture and final sample
was achieved and shows distinct behavior between them.
It is possible to observe a significant mass loss of starting
sample which initiate at 125˚C and is accentuated be-
tween 205˚C and 250˚C. This mass loss of about 58%
can be attributed to the presence of humidity and mainly
to the decomposition of ammonium nitrate. A significant
sample weight increase of about 40% between 500˚C and
900˚C can be observed, and it can be explained by the
formation of h-BN from the nitrogen gas flow and boron
in the sample that has not reacted, according to Equa-
tions (1) and (2). For the final sample, which has been
treated at 1300˚C the curve presented a small mass loss
(approximately 3%), showing a very good thermal stabil-
ity of the final h-BN material. Both XRD and FTIR
analyses suggest that the weigh increase corresponds to
the h-BN formation confirming the analysis from TGA.
Figure 4 shows the micrograph of the sample treated
at 1300˚C obtained by SEM using backscattered electron
beam (Figure 4(a)), where it is possible to observe a few
sheets of h-BN in nano-scale, and the indication of initial
formation of BNNTs. It is also possible to observe the
presence of iron nanoparticles (bright points) between
BN sheets, and they are found throughout the sample.

A Novel Synthesis Route to Produce Boron Nitride Nanotubes for Bioapplications 430
Figure 3. Thermogravimetric analysis of starting material
and sample obtained after heat treatment.
Figure 4. SEM micrographs of (a) BN nanostructure with
iron nanoparticle and (b) boron nitride nanotubes.
Figure 4(b) shows the presence of nanotubes and nano-
fibers with about 100 nm of diameter. The TEM images
of the sample are shown in Figure 5. It could be seen BN
sheets and some nanotubes like observed by SEM im-
ages (Figure 4). From expanded scale (Figure 5(b)) it
was possible to observe interplanar spaces of h-BN when
the sample is positioned in the perpendicular direction to
the electron beam of the transmission microscope.
The starting BN nanotubes samples contain catalyst
particles including Fe and a small amount of B2O3, as
determined FTIR and DRX. After this treatment, a selec-
tive chemical leaching process was used to remove metal
catalysts from BN nanotubes. Hydrochloric acid (HCl)
was found as an effective acid that could dissolve both
Fe and boron oxide. Regarding to purification process,
the following reactions occurred during the leaching
process:
32
Fe HClFeClH 
The product FeCl3 and the residual B2O3 are soluble in
hot water and they can be easily removed by washing
with hot water followed by filtration, according to used
method. XRD analysis (Figure 6) confirmed the effec-
tive chemical leaching process. The Fe diffraction peak
is absent from the XRD pattern taken from the leached
sample. The unchanged BN diffraction peaks suggest
Figure 5. TEM images of the BN nanostructures.
Figure 6. XRD pattern of the samples with iron and after
purification.
that BNNT structures are not damaged by the above
treatment. From the results obtained by the characteriza-
tion of samples, it was observed that the hexagonal boron
nitride was successfully achieved in satisfactory quantity.
However, the synthesis parameters of the proposed syn-
thesis lead to a partially formation of BN nanotubes, as
can be confirmed by the results of SEM and TEM chara-
cterization. In this context, it was proposed a second heat
treatment at a lower temperature in a nitrogen gas flow
during one hour, around 900˚C, to promote the forma-
tion of nanotubes. Samples after this second heat treat-
ment were analyzed by TEM.
In Figure 7 TEM images of BNNTs clearly evidence a
straight-walled tubular structure having an outer diame-
ter of approximately 30 nm (Figure 7(a)). Furthermore,
the HRTEM image (Figure 7(b)) reveals the multi-
walled nature of the BNNTs with each layer being clear-
ly distinguishable; the layers are spaced by 0.33 nm and
it corresponds to the crystallographic plane 002. This
distance of the BN layers agrees with that established by
Terrones and colleagues [13], and indicates that our BN
nanotube has a similar structure with those products syn-
thesized by arc discharge and laser ablation techniques.
From the analysis of Figure 8 it is possible to observe
the ordering of the layers of h-BN (top of the figure and
in highlighted frame) with interplanar space of 0.18 nm.
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A Novel Synthesis Route to Produce Boron Nitride Nanotubes for Bioapplications431
Figure 7. High-resolution TEM images of individual BN
nanotubes and of crystallographic plane 002.
Figure 8. TEM image of crystallographic plane 102.
This value (d) corresponds to the peak at 2θ = 41.58°
obtained in the analysis by XRD, which is characteristic
of h-BN. According to the database JCPDS N° 9 - 12, this
peak corresponds to the crystallographic plane 102. This
plan is extremely difficult to visualize and it had not
commonly reported.
3.2. Bioaplications
The data analysis from hemolytic test show that the per-
centage of hemolysis tended to zero for all concentra-
tions evaluated, according to Figures 9 and 10. These
results suggest that the as prepared BNNT and pure ma-
terials tested have no significant hemolytic activity, in-
dicating a good biotolerance to the materials.
The results of the MTT assay, as a measure of meta-
bolic activity of different cells following 48 h of contact
with the pure BNNT are shown in Figures 11 and 12.
The cytotoxicity of BNNT nanoparticles increased slightly
with increasing mass concentration of particle in all of
the cell cultures. Although the inhibitory concentration
of BNNT that kills 50% (IC50) of normal cells is around
50 µg/mL, only from a concentration of 200 µg/mL of
BNNT nanoparticles, the cell viability decreased to a
level between 40% and 50% of control. Similar results
Figure 9. Study of the Hemolytic activities of pure BNNT in
concentrations ranging 15 - 125 µg/mL compared to nega-
tive control (PBS). The results showed no hemolytic activity
in all the concentrations analyzed.
Figure 10. Study of the Hemolytic activities of pure BNNT
Fe in concentrations ranging 15 - 125 µg/mL compared to
positive control (TRITON). The results showed no hemo-
lytic activity significative in all the concentrations analyzed.
Figure 11. Effect of boron nitride nanocomposite (BNNT) in
concentrations ranging from 0.1 to 200.0 µg/mL on normal
cell lines (MRC-5) after 48 h treatment. The inhibitory
concentration of BNNT that kills 50% (IC50) of normal
cells is around 50 µg/mL.

A Novel Synthesis Route to Produce Boron Nitride Nanotubes for Bioapplications 432
Figure 12. Effect of boron nitride nanocomposite (BNNT) in
concentrations ranging from 0.1 to 200.0 µg/mL in different
tumor cells lines MCF-7, T98 and U87 after 48 h treatment
by the MTT assay. The inhibitory concentration of BNNT
that kills 50 % (IC50) of normal cells is around 50 µg/mL.
were found for tumor cells lines. However, the results re-
vealed that BNNT may have important toxicicity at con-
centrations higher than 200 µg/mL.
To our knowledge there are very few studies directly
or indirectly investigating the toxic effects of boron ni-
tride nanomaterials and no clear guidelines are present-
ly available to quantify these effects [30,31]. As when
one thinks in bioapplication, the material may be in con-
tact with cells or biological fluids such as blood. Evalua-
tion of the biocompatibility of BNNT on normal fibro-
blast cells shows that the IC50 of the evaluated BN’s is
around 50 g/mL. According Hussain et al. [32], the
nanomaterials cadmium oxide (CdO-1000 nm) and silver
(Ag-15 and 100 nm) showed high toxicity for rat liver
derived cell line (BRL 3A) using this same method.
Concentration as low as 25 µg/ml of CdO-1000 nm and
50 µg/ml of Ag-15 and 100 nm were able to evoke
around 95% of cell death indicating that the IC50 for
these materials, a parameter of toxic potential, is lower
than 25 and 50 µg/mL, respectively. Based in our study,
the IC50 of the evaluated BNNT (50 nm) on MRC-5
(fibroblast lung human) and tumor cell lines was higher
than 200g/mL, indicating that BN are less toxic than
CdO-1000, Ag-15 and Ag-100. These data show that
BNNT exhibited a good biocompatibility at concentra-
tions adequate for potential pharmacological applications
(between 0.1 to 10 µg/mL). Indeed, according to the li-
terature, boron nitride nanotubes are suitable for the de-
velopment of novel nanovectors for cell therapy, drug
delivery system, and other biomedical applications [11].
In conclusion, the MTT assay revealed that BNNT
may become lightly toxic to cultured human cells at high
concentrations. Although important, these results are
preliminary and a deeper study of performance of these
materials has to be developed.
4. Conclusions
Summarizing, we developed an easy and direct chemis-
try synthesis route to obtain nanotubes of boron nitride
with iron nanoparticles, without use of extreme conditions.
From FTIR and XRD analysis it was possible to under-
stand the reactions involved in the synthesis process, and
also to confirm the formation of hexagonal boron nitride.
From SEM and TEM images, it was possible to observe
the formation of BN nanotubes and also the crystallo-
graphic planes 002 and 102. Preliminary biocompatibi-
lity tests revealed that hemolytic activity of this material
is extremely low. MTT tests show that BNNT exhibited
a good biocompatibility at concentrations adequate for
potential pharmacological applications. The features pre-
sented suggest that this nanomaterial can be used for some
biological applications, as nanovectors for cell therapy, drug
delivery system and to assist in cancer treatment by using
radioisotopes.
5. Acknowledgements
This research was supported by the Brazilian agencies
CAPES, CNPq and FAPEMIG. The authors would like
to thank the Microscopy Center-UFMG for technical
support during electron microscopy work.
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