Abstracts of peer-reviewed articles published in referred
journals and revered conference proceedings
1. S. J.
Kalita, D. Rokusek, S. Bose, H. L. Hosick, A.
Bandyopadhyay. Effects
of MgO-CaO-P2O5-Na2O-based additives on mechanical
and biological properties of hydroxyapatite. Journal of Biomedical Materials Research
Part A, Vol. 71A,
Issue I, 2004:35-44.
In this research, we improved densification, hardness and
compression strength of synthetic hydroxyapatite (HAp) ceramics by introducing
small quantities of MgO-CaO-P2O5-Na2O-based
sintering additives. Biological
properties of HAp were not altered by this procedure. Phase analyses were done using a Philips Xpert fully automated diffractometer with Co K-alpha
radiation to understand the influence of additives on phase purity in the final
products. All compositions were
characterized at green and sintered densities, to understand the influence of
additives on densification. Some of the
compositions showed more than a 40% increase in Vickers microhardness compared
to pure HAp processed under the same conditions. Improvement in compression strength was also
detected in some compositions. In
vitro biological testing utilized a modified human osteoblast cell line to
test biocompatibility, cell-attachment and cell proliferation. All these compositions were found non-toxic
and biocompatible. Our results indicate
that MgO-CaO-P2O5-Na2O based sintering
additives can be used to improve both mechanical and biological properties of
HAp ceramics. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 71A: 35–44,
2004. Key words: calcium phosphate; hydroxyapatite; sintering
additives; bioactive ceramics; bone cells.
2. S. J. Kalita, S. Bose, H. L. Hosick, and A. Bandyopadhyay. CaO-P2O5-Na2O-based sintering
additives for hydroxyapatite (HAp) ceramics. Biomaterials, 25; 2004:2331-2339.
We have assessed the effect of CaO–P2O5–Na2O-based
sintering additives on mechanical and biological properties of hydroxyapatite
(HAp) ceramics. Five different compositions of sintering additives were
selected and prepared by mixing of CaO, P2O5,
and Na2CO3 powders. 2.5wt% of each additive was combined
with commercial HAp powder, separately, followed by ball milling, and sintering
at 1250oC and 1300oC in a muffle furnace. Green and
sintered densities of the compacts were analyzed for the influence of additives
on densification of HAp. Phase analyses were carried out using an X-ray
diffractometer. Vickers microhardness testing was used to evaluate hardness of
sintered compacts of different compositions. A maximum microhardness of 4.6
(70.28) GPa was attained for a composition with2.5
wt% addition of CaO:P2O5:Na2O
in the ratio of 3:3:4. Results from mechanical property evaluation showed that
some of these sintering additives improved failure strength of HAp under
compressive loading. Maximum compressive strength was observed for samples
with2.5 wt% addition of CaO. Average failure strength
for this set of samples was calculated to be 220 (750) MPa. Cytotoxicity,
and cell attachment studies were carried out using a modified human osteoblast
cell line called OPC-1. In vitro results showed that these compositions were
non-toxic. Some sintering aids enhanced cell attachment and proliferation,
which was revealed from SEM examination of the scaffolds seeded with OPC-1
cells. © 2003 Elsevier Ltd. All rights reserved. Keywords: Hydroxyapatite;
Calcium phoshpate; Sintering
additives; Bioactive ceramics; Bone cells
3. S. J. Kalita, S. Bose, H. L. Hosick,
and A. Bandyopadhyay. Development of controlled porosity polymer-ceramic
composite scaffolds via fused deposition modeling. Materials Science and Engineering: C, 23;
2003:611– 620.
This research is focused on development and fabrication of
controlled porosity polymer-ceramic composite scaffolds, with 3-D
interconnectivity designed to promote richer supply of blood, oxygen and
nutrients for healthy in-growth of bone cells. Particulate-reinforced
polymer-ceramic composites were developed by high shear mixing of polypropylene
(PP) polymer and tricalcium phosphate (TCP) ceramic. Processing aids were used
to improve plasticity and processibility to the
composites. Controlled porosity scaffolds were fabricated via the fused
deposition process, one of the commercially available rapid prototyping (RP)
techniques. These porous scaffolds were characterized for their use as bone
grafts in terms of physical, mechanical and biological properties. Hg-porosimetry was performed to determine pore size and their
distribution. Scaffolds with different complex internal architectures were also
fabricated using this composite material. Tensile properties of neat PP (as
received), PP with processing aids (without TCP) and PP-TCP composite (with
processing aids) were evaluated and compared using standard dog bone samples.
Uniaxial compression tests were performed on cylindrical porous samples with an
average pore size of 160 Am and varying vol.% porosity
(36%, 48% and 52%). Samples with 36 vol.% porosity
showed the best compressive strength of 12.7 MPa. Cytotoxicity and cell
proliferation studies were conducted with a modified human osteoblast cell-line
(HOB). Results showed that these samples were non-toxic with excellent cell
growth during the first two weeks of in vitro testing. © 2003 Elsevier B.V. All
rights reserved. Keywords: Rapid prototyping; Bio-composites; Fused deposition modeling; Bone graft; Porous materials
4. S. J. Kalita, S. Bose, H. L. Hosick, and A.
Bandyopadhyay. Porous
calcium aluminate ceramics for bone-graft
applications. Journal of
Materials Research, Vol.17 No. 12; 2002:3042-3049.
Calcium aluminate scaffolds with
controlled porosity were processed for bone-graft applications. Indirect fused
deposition process was used to fabricate these structures. Phase analyses were
done using x-ray diffraction technique on powdered samples of calcium
aluminates at different compositions. Hg porosimetry
was used to determine the pore sizes and the pore volumes present in these
controlled porosity structures at different calcium aluminate
compositions. Cylindrical samples were tested under uniaxial compressive
loading as a function of composition and volume fraction porosity (VFP).
Samples of 29% and 44% VFP (designed) with average pore size of 300 mm showed compressive strength
between 2 and 24 MPa. Cytotoxicity and cell proliferation studies were
conducted with a modified human osteoblast cell line (HOB). These materials
showed good cell attachment and a steady cell growth behavior with HOB cells
during the first three weeks of in vitro analyses. © 2002 Materials
Research Society
5. Hong, S.J., Bhatt, H., Suryanarayana, C.,
and Kalita, S.J., 2005.
Synthesis of nano-size hydroxyapatite (HAp) powders by mechanical alloying. Advances in Bioceramics and Biocomposites, D. Zhu and W. M. Kriven,
Editors; CESP, Vol. 26, Issue
6, p33-39.
Nano hydroxyapatite (Ca10(PO4)6(OH)2,
HAp) powders were synthesized by solid-state reaction of Ca(OH)2 and
P2O5 mixtures in a high-energy SPEX 8000 shaker mill,
using hardened steel vial and balls. The phase analysis was carried out using
X-ray powder diffraction technique. Transformation of Ca(OH)2
and P2O5 mixture to HAp phase was first observed
after 1 h of milling. The powder milled for 3 h showed prominently the presence
of HAp phase. TEM analysis revealed that as-synthesized HAp powder was in the
range of 20-60 nm. Measured quantities of synthesized nano-powders were pressed
uniaxially in a steel mold to prepare dense ceramic structures for
densification studies. These green structures were subjected to sintering
studies at 1300 oC for 6 h when the
highest sintered density of 3.17 g/cc was achieved. © 2005 American Ceramic Society
6. Bhatt, H.,
and Kalita, S.J., 2005.
Synthesis and sintering studies of nanocrystalline hydroxyapatite powders doped
with magnesium and zinc. Advances in Bioceramics and Biocomposites, D. Zhu and W. M. Kriven,
Editors; CESP, Vol. 26, Issue
6, p17-23.
In this research, we have synthesized
nanocrystalline hydroxyapatite (Ca10(PO4)6(OH)2,
HAp) powders doped with magnesium and zinc using the water-based sol-gel
technique and characterized them. Calcium nitrate and triethyl phosphite were
used as starting materials. These chemicals were dissolved in distilled water,
separately, under vigorous stirring. As-prepared calcium nitrate sol was added
drop wise into the hydrolyzed phosphite sol and then aged and dried. Dried gel
was then crushed into fine white powders with the help of mortar and pestle and
a measured amount of magnesium oxide and zinc oxide powders were added to the
crushed amorphous powders, separately. Calcination was carried out at 250-500oC.
Morphology of the powders was determined using transmission electron
microscopy. TEM results revealed that the particle size diameter of powders
were in the range of 5-10 nm. Phase analyses were carried out using powder
X-ray diffraction technique. As-synthesized powders were also pressed
uniaxially in a steel mold to prepare dense ceramic structures. These green
structures were sintered at 1300oC for 6 h in a muffle furnace for
densification. Highest sintered density of 3.29 g/cc was measured for
magnesium-doped powder. © 2005 American
Ceramic Society
7. S. J.
Kalita, S. Bose, H. L. Hosick and A Bandyopadhyay. Oxide Based Sintering Additives for HAp
Ceramics. Ceramic Transactions, Vol. 147, edited by Veeraraghavan
(V) Sundar, Richard P. Rusin,
and Claire A. Rutiser (2003).
With the
increase in average age of the human population, the challenge of treating bone
defects and repairs is rising and overall orthopedic market is growing. Hydroxyapatite
(HAp), a bioactive ceramic, is known for its excellent biocompatibility, but
shows poor mechanical performance.
In our research, we have tried to improve mechanical performance of
commercial HAp by introducing small quantities of various sintering
additives. A range of oxide based
sintering additives were selected and prepared based on already reported
results of their biocompatibility when tested individually or in addition with
other materials. Dense compacts were
prepared using a uniaxial press mold with an average green density of 1.6
g/cc. Results showed that some of these
sintering additives significantly improved densification and hardness of
synthetic HAp. A maximum bulk density of
3.05 g/cc was reported. Vickers micro
hardness testing showed that there is 50% increase in the hardness of HAp with
some of the sintering aids. Cytotoxicity
and cell proliferation studies were conducted using a modified human osteoblast
cell-line (HOB). In vitro testing with osteoprecursor cells (OPC1) showed that most
of these compositions were non-toxic.
Microscopic observation revealed that OPC1 cells were anchored and
attached on matrices of most of these compositions. This paper will present physical, mechanical
and cytotoxicity test results of different compositions of hydroxyapatite (HAp)
with various sintering additives. © 2003 American Ceramic Society
8. S.
J. Kalita, J. Finley, S. Bose, H. L. Hosick and A. Bandyopadhyay. Development of Porous
Polymer-Ceramic Composites as Bone Grafts. Mat. Res. Soc. Symp. Proc.
Vol. 726, Q5.8, 2002.
Biomaterials
have made significant contributions to the advancement of modern health care and
drug delivery industries. The present research is based on development of
porous polymerceramic composite scaffolds using
polypropylene (PP) polymer and tricalcium phosphate (TCP) ceramic for
bone-graft applications. Three dimensionally interconnected controlled porosity
scaffolds were fabricated using a fused deposition modeling (FDM) system.
First, ceramic and polymeric materials were compounded under high shear using a
torque rheometer. Compounded materials were then
extruded to a 1.78mm diameter continuous filament using a single screw extruder.
These filaments were used as a feedstock material for an FDM 1650 machine for
direct fabrication of controlled porosity parts. Hg-porosimetry
was done to determine pore size and their distribution in these structures.
Tensile properties of neat composites and as received polymer were measured and
compared using standard dog bone samples. Uniaxial compression tests were
performed on cylindrical porous samples having average pore size of 160 µm and
36 vol% porosity. These samples showed an average
ultimate compressive strength of 12.7 MPa. Average compressive modulus was calculated as
263 MPa. Cytotoxicity and cell proliferation studies were conducted with OPC1
modified human osteoblast cell-line. It was found that composite matrices were
non-toxic and they showed excellent cell growth with OPC1 cells. Mat.
Res. Soc. Symp. Proc. Vol. 726 © 2002 Materials
Research Society
9. S. J. Kalita, S. Bose, H. L. Hosick, S. A.
Martinez and A. Bandyopadhyay. Calcium Carbonate Reinforced Natural polymer Composite
for Bone Grafts. Mat. Res.
Soc. Symp. Proc. Vol. 724, N8.18, 2002.
Biomaterials have made significant
contributions to the advancement of modern health care and drug delivery
industries. The present research is based on development of porous
polymer-ceramic composite scaffolds using polypropylene (PP) polymer and
tricalcium phosphate (TCP) ceramic for bone-graft applications. Three dimensionally interconnected controlled
porosity scaffolds were fabricated using a fused deposition modeling (FDM)
system. First, ceramic and polymeric
materials were compounded under high shear using a torque rheometer. Compounded materials were then extruded to a
1.78mm diameter continuous filament using a single screw extruder. These filaments were used as a feedstock
material for an FDM 1650 machine for direct fabrication of controlled porosity
parts. Hg-porosimetry was done to determine pore size
and their distribution in these structures. Tensile properties of neat
composites and as received polymer were measured and compared using standard
dog bone samples. Uniaxial compression
tests were performed on cylindrical porous samples having average pore size of
160 µm and 36 vol% porosity. These samples showed an
average ultimate compressive strength of 12.7 MPa. Average compressive modulus
was calculated as 263 MPa. Cytotoxicity
and cell proliferation studies were conducted with OPC1 modified human
osteoblast cell-line. It was found that
composite matrices were non-toxic and they showed excellent cell growth with
OPC1 cells. Mat. Res. Soc. Symp. Proc. Vol. 724 © 2002
Materials Research Society