2. oxyhemoglobin. The bonding to the dioxygen molecules is
weak. Therefore, on reaching the site of oxygen utilization
such as the muscles, the oxygen can be released. Nickel ions
are present in some enzyme systems in the form of por-
phyrin-type complexes. Certain bacteria which reduce carbon
dioxide to methane, need nickel. M. thermoacetica is one of
the examples of the above-mentioned bacteria.15
For quick
recovery, it is desirable to keep the surrounding tissues pro-
tected from infection and allergy. Silver is an established
antimicrobial agent and thus, it can serve as solution to
infection and allergy problems.
In the light of this situation, authors have synthesized fer-
romagnetic bioactive ceramics using nickel and iron and con-
ducted comparative study of bioactive and drug delivery
properties of silver nanoparticles coated and uncoated ferro-
magnetic bioactive ceramics. To investigate the antimicrobial
properties, study has been undertaken with six different
gram-positive and gram-negative strains. Cell proliferation
and cytoprotective tests have been conducted with the help
of MG63 cell lines. Transmission electron microscopy
(TEM), X-ray diffraction (XRD), vibrating sample magne-
tometer (VSM), and Brunauer–Emmett–Teller (BET) tech-
niques have been used to investigate the growth of HAp
layer and degradation and ferromagnetic behavior of the
samples. Reactivity with red blood cells has been investigated
to check the cytotoxic behavior of samples during hemolysis
study. Furthermore, the effect of magnetic field on the drug
release properties of samples has also been investigated.
II. Materials and Methods
(1) Sample Preparation
Ferromagnetic samples of the composition xNiO–(3Àx)
Fe2O3–52CaO–30SiO2–15P2O5 (where x = (0, 3) mol%) have
been prepared in the laboratory using sol–gel technique. Tetra-
ethyl orthosilicate (TEOS), triethyl phosphate, calcium nitrate
tetra hydrate, iron nitrate nona hydrate, nickel nitrate hexa
hydrate, and silver nitrate have been used as source materials
for SiO2, P2O5, CaO, Fe2O3, NiO, and Ag, respectively.
(A) Preparation of Ferromagnetic Bioactive Ceram-
ics: 1M HNO3 was used as the catalyst for hydrolysis pro-
cess. TEOS was added into 1M HNO3 solution (TEOS and
H2O molar ratio equal to eight) and the mixture was stirred
up to 1 h for complete hydrolysis. Precursor of phosphorus,
calcium, iron, and nickel were dissolved one by one with the
stirring of 40 min for each. After one hour of vigorous stir-
ring, transparent solution was obtained. The solution was
kept in an airtight beaker for 3 days for aging. The gel was
heated up to 60°C for 12 h and 120°C for 12 h. The samples
were calcinated up to 700°C for 8 h. Prepared samples had
been crushed in agar and mortar for 1 h. Description of the
prepared samples is provided in Table I.
(B) Silver Coating on Sample: One gram of prepared
ferromagnetic bioactive sample has been coated with 1M sil-
ver nitrate solution (20 mL). Samples have been dipped into
the silver nitrate solution with mild stirring up to 1 h. Sample
filtration has been undertaken with 0.22 lm millipore filter
paper which was followed by drying up to 100°C for 4 h.
(2) Assessment of In Vitro Bioactivity
In vitro bioactive nature of samples has been evaluated with
the help of simulated body fluid (SBF) solution. SBF solu-
tion has been prepared as per the recipe reported elsewhere.16
One gram of sample has been used for immersion in 50 mL
of SBF as per the protocol published by authors elsewhere.17
To maintain ions concentration, old SBF was replaced with
fresh SBF solution after every 12 h.
(3) Materials Preparation for Antimicrobial Test
(A) Test Organisms: The reference strains of bacteria
and two yeasts, used for testing of their sensitivity to fungal
extracts, were obtained from Microbial Type Culture Collec-
tion (MTCC), Institute of Microbial Technology, Chandi-
garh, India and the clinical isolate methicillin-resistant
Staphylococcus Aureus (MRSA) was obtained from Post
Graduate Institute of Medical Education and Research,
Chandigarh, India. Reference strains included are gram-posi-
tive bacteria Staphylococcus aureus (MTCC740), gram-nega-
tive bacteria, Klebsiella pneumoniae (MTCC109), Shigella
flexneri (MTCC1457), Salmonella typhimurium (MTCC
1251), and Escherichia coli (MTCC-119). The bacterial cul-
tures were maintained on nutrient agar slants. Inoculum
preparation and screening of samples for antibacterial activ-
ity by agar well diffusion of samples are performed by
authors as describe elsewhere.17
(B) Minimum Inhibitory Concentration: Minimum
inhibitory concentration (MIC) was evaluated as per the fol-
lowing procedure. A stock solution of all the samples 2.5%
(25 mg/mL) concentration were prepared and incorporated
into Muller Hinton agar medium. The final concentrations of
the compounds in the medium containing plates have the
range varying from 0.05 up to 5 mg/mL. Word “compound”
refers to the “sample suspended in dimethyl sulfoxide
(DMSO)”. These plates were then inoculated with 10 lL of
the activated bacterial strain(s) by streaking with a sterile
toothpick. The plates were incubated at 37°C for 24 h and
the lowest concentration of the compound causing complete
inhibition of the bacterial growth was taken as MIC. The
results were compared with that of control, in which the
sample was replaced with DMSO. The experiments were per-
formed in triplicate.
(4) Characterization Techniques
TEM, XRD, Fourier-transform infrared spectroscopy
(FTIR) and VSM studies have been undertaken using JEOL
J 1200 TEM Machine, Bruker D8 Focus XRD Machine
(Karlsruhe, Germany), Perkin Elmer Spectrometer (Baeswei-
ler, Germany) and Microsence VSM EZ Series Model (Lowell,
MA), respectively. BET analysis has been conducted by
Micrometrics ASAP 2020 (Norcross, GA) to explore the sur-
face area and porous nature of samples Biological properties
of samples have been studied with the help of drug release,
cytotoxicity, cell culture, and antimicrobial studies. Labsystem
Multiskan EX ELISA (Sunnyvale, CA) and Biorad 680-XR
Table I. Samples with Surface Area and Pore Size Values During Drug Loading and Release
Sample description Denotation
BET study
SBET (m3
/g) D (nm)
Drug loaded Drug released Drug loaded Drug released
Uncoated iron-based sample (x = 0) xNiOX=0 1.76 4.94 19 36
Uncoated nickel-based sample (x = 3) xNiOX=3 1.32 5.87 13 39
Silver-coated iron-based sample (x = 0) xNiOX=0 Ag 13.87 14.47 43 45
Silver-coated nickel-based sample (x = 3) xNiOX=3 Ag 14.95 21.57 19 24
2 Journal of the American Ceramic Society—Anand et al.
3. Machines (Sunnyvale, CA) with 570 and 590 nm wavelengths
of UV–Visible range have been used for biological studies.
III. Results and Discussion
(1) Checking the Growth of HAp Layer
Growth of HAp is prerequisite for suitability of synthetic
material for bone regeneration applications. The presence of
HAp during in vitro study of the samples has been investi-
gated by employing TEM and XRD techniques.
(A) TEM Analysis: Micrographs of xNiOx=0 and
xNiOx=0Ag have been shown in Figs. 1(a) and (b). Values
of hkl from fast fourier transform (FFT) and micrographs of
high-resolution TEM (HRTEM) of samples have also been
provided in the Fig. 1. Table in Fig. 1(c) shows the compar-
ison of the hkl values calculated from XRD and TEM data
and they have been found to be in good agreement. The hkl
values of (100), (002), (101), and (300) in FFT of Fig. 1(a)
indicate the presence of HAp. On the other hand, hkl values
of (220) and (111) indicate the presence of silver nanoparti-
cles on the surface of HAp.
(B) XRD Studies: XRD patterns of the uncoated sam-
ples have been provided in Figs. 2(a) and (c). Sharp peaks of
HAp (JCPDS no. 73-1731), calcium silicate (JCPDS no. 03-
1068), and calcite (JCPDS no. 83-0577) indicate the crys-
talline nature of bioactive material. Calcium iron phosphate
(JCPDS no. 49-1223) and nickel oxide (JCPDS no. 47-1049)
peaks have also been observed in iron- and nickel-doped sam-
ples. Iron attached with calcium and phosphorus has similar
ionic radius as that of the calcium. Therefore, iron replaces
the some part of calcium from HAp phase and form calcium
iron phosphate phase (Ca19Fe2 (PO4)14). Calcium iron phos-
phate is useful to reduce the toxic behavior of iron. Similar
crystalline phases in the silver-coated samples have also been
observed with the presence of silver (JCPDS no. 04-0783) hkl
(111) at 2h = 38.11° and hkl (220), at 2h = 64.42°.
During in vitro analyses, observations have been under-
taken after 2, 5, and 10 days. In case of uncoated samples, it
has been seen that crystalline peaks start to dissolve after
2 days and completely disappear after 5 days. Only peak of
HAp at 2h = 31.9° remain present throughout the in vitro
analyses. It may be due to the stability of HAp in pH 7–8.
When XRD study has been undertaken on the 10th
day of
in vitro analysis, new phases of HAp have been observed to
grow on the surface of the sample. This feature indicates the
bone regeneration ability of prepared samples. All the
uncoated samples have shown almost similar HAp growth
during in vitro analysis.
XRD patterns of silver-coated samples have shown slow
dissolution of peaks up to 5 days of in vitro analysis. It
may be due to the delocalization of nanoparticles of silver
metal on the surface of samples. Silver particles act as a
barrier in between SBF and surface of the sample which
decrease the dissolution rate of the sample. It can be
noticed that the rate of growth of HAp in the case of sil-
ver-coated sample is slow as compared to uncoated samples.
But after 10 days, new phases of HAp start to grow and
other phases like silver and calcium silicate are observed to
be near the complete dissolution. Many authors have
reported silicate glass with amorphous nature but there are
few authors also who have reported silica-based bioactive
ceramics. For example, Kaur et al.,2
Erol et al.,7
Oudadesse,
et al.4
and Oki et al.5
have reported bioactive glasses and
Lin et al.18
and Wu et al.19
have reported bioactive ceram-
ics. All the above-mentioned authors have prepared silica-
based bioactive materials. These results indicate that it is
possible to prepare bioactive glasses as well as bioactive
ceramics using silica as a constituent material during the
preparation of bioactive samples. Authors speculate that
crystalline nature of the prepared samples may be due to
the presence of crystalline phase of hydroxyl apatite, calcite,
and calcium iron phosphate crystalline phases in the sam-
ples20, 21
during sintering process. Boccaccini et al.22
have
also reported similar crystallization due to sintering process.
Our samples are composite materials. A broad hump has
been observed in the XRD pattern during in vitro analyses.
This may be either due to the calcium phosphate phase for-
mation in the SBF or it may be due to formation of some
apatite layer which is still amorphous in nature. Authors
may conduct the further experimental investigation to
understand these data.
(C) FTIR Studies: Figure 3 provides the FTIR spec-
tra of the prepared samples. Following observations are
reported.
(a) Before In vitro Study: FTIR spectra indicate the
presence of SiO2 content due to Si–O rocking (465 cmÀ1
),
(a) (c)
(b)
Fig. 1. TEM micrographs with HRTEM and FFT patterns (a) xNiOX=0, (b) xNiOX=0Ag, and (c) Table of hkl calculated from XRD and
TEM data.
Ferromagnetic Bioactive Ceramics 3
4. two dimensional silica network (at 1040 cmÀ1
) and SiO4
4À
(4
nonbridging oxygen) (at 872 cmÀ1
). Peaks at 558 and
601 cmÀ1
are due to (m4PO4 vibrations which indicate the
presence of HAp phase in the samples before in vitro analysis
[Figs. 3(a)–(d)]. Similar vibrations for phosphorus have been
observed at 1040 cmÀ1
. The presence of calcite has been indi-
cated due to the presence of peaks at 1380, 1440 cmÀ1
(m3CO3
2À
vibrations), 872 cmÀ1
(m2 assym.CO3
2À
), near
1805 cmÀ1
(m1 + m2 sym. CO3), and at 1090 cmÀ1
due to m1
sym. CO3 sym. vibrations. OH molecule vibrations are also
reported at 1640 and 3640 cmÀ1
. Clear peaks at 2920–2940
and 2860 cmÀ1
are due to the formation of heavy-metal ion
vibrations (a–Fe phase) (Figs. 3(b) and (d)].
(b) After In Vitro Analysis: FTIR spectra were taken
after 2, 5, and 10 days of immersion of samples in SBF.
Peaks at 558 and 601 cmÀ1
which are due to (m4) PO4 vibra-
tions became more prominent due to the formation of HAp
phase after 5 and 10 days of in vitro analyses. Carbonate
peaks have started to disappear due to the dissolution of cal-
cium carbonate after 2 days of in vitro analyses. The presence
of SiO2 content is due to the formation of silica gel layer
which enhance the formation of HAp layer. FTIR data con-
firm the conclusions of the analysis of XRD spectra.
(2) Ferromagnetic Behavior and Drug Release Properties
Ferromagnetic hysteresis loop of the samples has been inves-
tigated using VSM technique. Drug release properties have
been studied using gentamycin as an antibiotic with and
without the application of magnetic field.
(A) VSM Technique: Soft ferromagnetic materials can
have medical applications in the areas of treatment of cancer
cells, image sensing, and drug carriers.23
Uniform field has
been used to magnetize the sample. Sample was placed under
sinusoidal vibrator at room temperature. Observed hysteresis
loop has been shown in Fig. S1. Narrow hysteresis loops
have low saturation magnetization value with high coercive
force value. Moreover, it has been reported that smaller is
the area of hysteresis loop, lower energy is required for
demagnetization of material.24
It can be concluded from
Fig. S1 that our samples exhibit similar behavior to soft fer-
romagnetic material and may be used for different medical
applications like drug delivery and hyperthermia treatment.13
Low saturation magnetization value of samples may be due
to the reaction of iron with other elements such as calcium
and phosphorus with the formation of calcium iron phos-
phate phase (as inferred from XRD study).
(B) Drug Release Properties: To check the drug’s car-
rier’s ability of ferromagnetic particle, drug release study of
prepared samples has been undertaken under normal condi-
tion as well as under the influence of the magnetic field
(Fig. 4). Drug release study for normal conditions has been
performed as reported elsewhere.25, 26
Gentamycin as an
antibiotic has been tested for drug release study of the sam-
ples. One gram of prepared sample has been immersed in
20 mL of gentamycin solution. The sample has been kept in
the solution up to 24 h. After filtering the powder and drying
at 40°C up to 24 h, release of gentamycin from the drug-
loaded sample has been investigated in an incubator at 37°C.
One gram of powder has been dipped in the 20 mL of SBF
under 37°C. Gentamycin release was determined by UV anal-
ysis. The release medium was withdrawn at the predeter-
mined time intervals and replaced with a fresh SBF solution
each time. The trends for uncoated and silver-coated samples
are provided in Figs. 4(a) and (b). Similar observations have
been undertaken for the drug release under the magnetic
(a)
(b)
(c)
(d)
Fig. 2. XRD graphs of uncoated (a) xNiOX=0, (c) xNiOX=3 and coated (b) xNiOX=0Ag, (d) xNiOX=3 Ag samples before and after in vitro
analysis.
4 Journal of the American Ceramic Society—Anand et al.
5. field. Samples soaked in SBF were placed under the magnetic
field for 10 min. It has been observed that in both conditions
(with and without magnetic field), all the prepared samples
have shown quick release in first hour and then there is
decrease in the rate of release of drug in SBF. When samples
have been kept under magnetic field, drug release of sample
has been observed to increase to almost 10%–15%
[Figs. 4(a) and (b)]. High drug release of the samples under
the magnetic field may be due to the heat produced by
vibrating ferromagnetic particles.
Commutative concentration of drug release in the silver-
coated ferromagnetic sample is lower as compared to
uncoated samples. This can be attributed to high zeta poten-
tial of nanoparticles which enhance the electric interaction in
between silver molecule and gentamycin molecule.27
Drug
release studies show that prepared samples have good
response in drug delivery phenomena and can be used as
drug carriers.
Representative figure for two samples has been provided
as Fig. 4(c). Surface area (SBET) and pore size (D) values of
samples loaded with gentamycin and its release are given in
Table I. Pore size of samples is in the range of type II (2–
50 nm) which represents their mesoporus nature. Higher sur-
face area of silver-coated samples is due to the presence of
silver nanoparticles (high surface to volume ratio) on the sur-
face of sample. Size of gentamycin molecule is about 0.9 nm.
Therefore, it can easily encapsulate into the pores (few
nanometers) of samples. During in vitro drug release from
the samples, increase in the surface area and pore size of the
samples have been observed as compared to drug-loaded
samples. This feature supports the speculation of the authors
that drug encapsulates in the pores of samples.
400 800 1200 1600 2000 2400 2800 3200 3600 4000
5 days
Intensity(a.u.)
xNix=0
1632
1470
1380
1040
601
558
2 days
Before SBF
10 days
465
Wavenumber (cm
-1
)
400 800 1200 1600 2000 2400 2800 3200 3600 4000
Intensity(arb.units)
xNix=3
5 days
2 days
Before SBF
872 10 days
465
558
601
1040
1440
1634 2860 2928
Wavenumber (cm
-1
)
400 800 1200 1600 2000 2400 2800 3200 3600 4000
1430
1380
1640
2 days
5 days
Before SBF
10 days
470
558
601
1040
Intensity(arb.units)
Wavenumber (cm
-1
)
xNix=0
Ag
400 800 1200 1600 2000 2400 2800 3200 3600 4000
xNix=3
Ag
2840
2920
1630
470
558
601
1040
1430
2 days
5 days
Before SBF
10 days
Intensity(a.u.)
Wavenumber (cm
-1
)
(a) (b)
(c) (d)
Fig. 3. FTIR spectra of uncoated (a) xNiOX=0,(b) xNiOX=3, and coated (c) xNiOX=0Ag, (d) xNiOX=3Ag samples before and after in vitro
analysis.
0.2 0.4 0.6 0.8 1.0
0
1
2
3
4
5
6
7
8
0 5 10 15 20 25 30
0
10
20
30
40
50
60
70
80
Time(hrs.)
xNix=0
Ag (without Magnetic field)
xNix=3
Ag (without Magnetic field)
xNix=0
Ag (with Magnetic field)
xNix=3
Ag (with Magnetic field)
Time(hrs.)
Drugrelease%
0 5 10 15 20 25 30
0
10
20
30
40
50
60
70
80
90
100
xNix=0
(without Magnetic field)
xNix=3
(without Magnetic field)
xNix=0
(with Magnetic field)
xNix=3
(with Magnetic field)
Drugrelease%
QuantityAdsorbed(mmol/g)
Relative Pressure p/po
NiOX=0
(Gentamycin Loaded)
NiOX=0
(Gentamycin Released)
NiOX=0
Ag(Gentamycin Loaded)
NiOX=0
Ag(Gentamycin Released)
(a) (b) (c)
Fig. 4. Drug release of prepared samples (a) uncoated samples (b) coated samples. Error bar indicates the standard deviation observed for three
measurements and (c) N2 adsorption isotherms.
Ferromagnetic Bioactive Ceramics 5
6. From Figs. 4(a) and (b) it can be observed that about
40%–50% drug has been released within the first 10 h and
then next 10 h drug release rate reached up to 70% after that
it became almost constant with maximum release up to 80%
in 30 h. This anomalous release rate of drug molecule is due
to encapsulation of drug molecule with nanostructure silver
molecule and also in the pores of sample. High release rate
of drug in the first interval is due to immediate release of
drug molecules from the pores of sample and slow release
rate is due to the high zeta potential property of nanostruc-
ture which hold the drug molecule more tightly.
Concentration of released gentamycin has been fitted in
the first-order kinetic equation. This model can be used to
describe absorption and elimination behavior of drugs. Fol-
lowing equation has been used to elucidate the drug release
behavior of gentamycin from our samples.
logQt ¼ logQ0 À K1t=2:303 (1)
where, Qt is cumulative concentration released in aqueous
solution at time t, Q0 is the initial amount of drug, t is the
time in hrs, and K1 is the release rate constant. To find the
release profile, logQt is plotted against t and correlation coef-
ficient (R2
) has been evaluated. Calculated values of R2
and
K1 are provided in Table II. It has been observed that the
values of R2
of silver-coated samples are closer to 1 than
uncoated samples, which indicate that it is possible to predict
the release behavior of gentamycin of coated samples with
better accuracy.
Ferromagnetic drug-loaded samples can also be used for
the treatment of cancerous cells.18
Loaded drug may be anti-
cancer or antibiotic which can kill the cancerous cells and
heal the surrounding tissues. Moreover, cancerous cells may
also be killed by raising surrounding temperature of infected
body region in the range from 42°C to 45°C by hyperther-
mia. For the treatment of cancerous bone cells, there is
requirement of a bioactive material which not only kills the
cancerous cells but also help to regenerate the new bone tis-
sues with the formation of HAp at the infected area of bone.
It has been observed that it is possible to use our ferromag-
netic samples for growth of HAp layer as well as drug release
studies. It may be possible to use our reported compositions
for hyperthermia treatment for which their possibility of rais-
ing temperature needs experimental investigation which can
be part of our future studies.
(3) Estimation of Samples as Effective Implant Materials
All the synthesized bioactive materials may not be successful
implant materials in the human body. Degradation rate,
reactivity with blood cells, antimicrobial properties, and cell
viability against human cell lines are some of the key studies
which can be used to explore the practical utility of the
implant materials.
(A) In Vitro Degradation Study: To check the
biodegradability of prepared samples, set of in vitro degrada-
tion studies have been performed as reported by authors
elsewhere.17
Detailed information is provided under Support-
ing data.
(B) Hemolysis: Reactive behavior of prepared samples
with Red and White cells of human blood have been investi-
gated. Detailed information is provided under Supporting
data.
(C) Antimicrobial Activity: The bacterial cultures used
in this study (Table S1) are responsible for causing gastroin-
testinal tract and respiratory infections. All the compounds
have shown good inhibitory activity against all the microor-
ganisms tested (gram-positive and gram-negative bacteria).
Gram-negative bacteria acquire resistance more readily due
to their outer membrane which contains narrow porin chan-
nels which retard the entry into the cell (even small hydro-
philic compounds), a lipopolysaccaride moiety which slows
down the trans membrane diffusion of lipopolyphilic antibi-
otics and they often possess a multidrug efflux pump which
eliminates many antibiotics from the cells, resulting in many
diseases. Our samples have shown antibacterial activity
against gram-negative bacteria such as K. pneumoniae, S.
typhimurium and E. coli with varied zone of inhibition. S.
aureus and K. pneumoniae were found to be the most sensi-
tive organisms with zone of inhibition values 21 mm
(xNiOX=0) and 20 mm (xNiOX=3) and 21 mm (xNiOX=0Ag)
and 24 (xNiOX=3Ag), respectively (shown in Table S1). The
importance of the study has further enhanced when it was
observed that the resistant strain “MRSA” have shown sensi-
tivity to these samples. As shown in the Table S1, silver-
coated samples have shown better MIC of 0.050 mg/mL
against S.aureus and K.pneumoniae as compared to uncoated
samples (0.70–2 mg/mL). Thus, our reported chemical com-
positions have shown broad antibacterial potential which can
be further exploited for various pharmaceutical processes. It
has been noticed that silver coating improves the antimicro-
bial properties of the synthesized samples.
(D) Cell Culture Studies: Samples behavior with MG
63 cell lines has been investigated a per the procedure pub-
lished by authors elsewhere.17
Briefly, Dulbecco’s Modified
Eagle’s Medium has been used with fetal bovine serum 10 wt
%, streptomycin and gentamycin 100 U/mL each to main-
tain cell lines under 37°C incubation with humid environ-
ment containing 5% CO2. 3-(4,5-dimethylthiazol-2-yl)-2,5-
diphenyltetrazolium bromide (MTT) assay has been used to
check the cell integrity. Figures S3(a) and (b) are the repre-
sentative optical microscope images (at 40X) of cell growth
on the samples xNiOX=0 and xNiOX=0Ag. Figure S3(c)
shows the cell viability of samples with respect to MG63 cell
lines. Samples have been compared with commercial avail-
able culture plate. It has been observed that all the prepared
samples successfully provide the positive environment for cell
growth. Leaching of ions seems to have significant impact on
the biological behavior of samples. Cell viability of uncoated
samples has been observed to be better as compared to
coated samples. It may be due to slightly toxic nature of sil-
ver. Due to low molar concentration of silver and low degra-
dation rate of silver-coated samples, toxicity level is within
survivable range and thus, significant cell proliferation has
been observed even for silver-coated samples.
Oxidative stress (cytoprotective test) test data for samples
with MG 63 cells is provided in Fig. S4(d). Results of oxida-
tive stress study are provided under Supporting data. MTT
assay has shown a sharp drop in cell viability (~20%) in
4 days for silver containing samples. It has been reported
that silver is not only toxic against bacteria19, 20
but also
against cells.22
It is speculated that toxic nature of silver
against bacteria as well as cells may be responsible for higher
decrease in cell viability within 4 days. Therefore, concentra-
tion of silver should be monitored carefully within the bioac-
tive system.
Prepared samples fulfill the fundamental requirements to
act as bone regeneration materials with excellent drug release
and antimicrobial properties. Arcos et al.21
have reported the
Table II. Correlation Coefficient and Release Rate Constant
Calculated from the First-Order Kinetic Model
Sample Code R2
K1
xNix=0 (without magnetic field) 0.9420 À0.7 9 10À2
xNix=3 (without magnetic field) 0.9884 À2.2 9 10À2
xNix=0 (with magnetic field) 0.9479 À1.3 9 10À2
xNix=3 (with magnetic field) 0.9890 À2.5 9 10À2
xNix=0Ag (without magnetic field) 0.9819 À1.6 9 10À2
xNix=3Ag (without magnetic field) 0.9800 À2.3 9 10À2
xNix=0Ag (with magnetic field) 0.9889 À2.6 9 10À2
xNix=3Ag (with magnetic field) 0.9935 À3.4 9 10À2
6 Journal of the American Ceramic Society—Anand et al.
7. bioactivity of iron-doped bioactive samples after 6 days, but
in our prepared samples HAp phase has been observed after
2 days of in vitro analysis. Faster growth of HAp layer is
desired because it can lead to quick recovery of the damaged
bone. Due to ferromagnetic in nature, samples can also be
checked further for the treatment of cancerous bone for
hyperthermia treatment. It has been found that coating of sil-
ver nanoparticles improves degradation rate and antimicrobial
properties. As part of future study, authors purpose experi-
mental investigation of temperature variation as function of
magnetic field for silver-coated samples to explore the possi-
bility of using the samples for hyperthermia treatment. Cell
culture study may also be performed with human cancer cell
line under the influence of magnetic field so that death of cells
(due to rise in temperature or hyperthermia) can be recorded.
IV. Conclusions
Formation of hydroxyl apatite layer on the surface of samples
during in vitro analysis indicate the bioactive nature of sam-
ples with the controlled degradation of samples in the SBF
solution. Silver-coated samples have shown low degradation
rate as compared to uncoated samples. Degradation study
with citric buffer also indicate the slow degradation rate of sil-
ver-coated samples. Being a antimicrobial agent, the presence
of silver for long time during in vitro analysis is always advan-
tageous for the protection against the gram-positive and
gram-negative microorganisms. VSM data show the ferro-
magnetic behavior of all the prepared samples which is a posi-
tive indication for their possible use as ferromagnetic
bioactive materials for clinical applications. Drug delivery
tendency of ferromagnetic particles has been observed to be
enhanced in the range 10%–15% under the influence of exter-
nal magnetic field. Drug encapsulation in the powder samples
has been speculated from the analysis of BET studies. All the
prepared samples have been observed to be nontoxic in nat-
ure and they provide the healthy environment for the growth
of MG 63 cells. Prepared samples have also been observed to
be good cytoprotective materials. Antimicrobial testing of
samples confirms the strong tendency of samples to kill gram-
positive and gram-negative microorganisms. The reported
samples can act as drug carriers for antibiotic drugs.
Acknowledgments
The authors Vikas Anand and Kulwinder Kaur are grateful to the financial
assistance provided by the UGC, New Delhi (India) through SRF (NET)
[F.17-74/2008(SA-I)] and DST, New Delhi (India) through INSPIRE program
[IF-120620], respectively.
Supporting Information
Additional Supporting Information may be found in the
online version of this article:
Fig. S1. The hysteresis loop of synthesized magnetic bioac-
tive ceramics (a), (c) uncoated sample and (b), (d) silver-
coated samples.
Fig. S2. In vitro degradation of prepared samples (a) pH
change in citric buffer, (b) pH change in SBF, (c) XRD
graphs of uncoated samples in citric buffer and (d) XRD
graphs of coated samples in citric buffer.
Fig. S3. Representative micrographs (at 40 X) of RBCs (a)
uncoated sample (b) silver-coated sample (c) positive control
and (d) negative control.
Fig. S4. Representative micrographs (at 40X ) of MG 63
cell lines (a) uncoated sample, (b) silver-coated sample and
cell viability bar graphs through (c) cell culture and (d) cyto-
protective test. Error bars in (c) and (d) indicates the stan-
dard deviation observed for three measurements.
Table S1. Inhibition zone and MIC values against different
microorganism (Error bar indicates the standard deviation
observed for three measurements.).
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Ferromagnetic Bioactive Ceramics 7
