Incorporating Sr nanoparticles in bone structure will result in strengthening of the bone and bone scaffolds!.

1. Louisiana Tech University •
BioMorph
Strontium-Coated Clay Nanoparticles in Calcium
Phosphate Cement for Biomedical Applications
Anusha Elumalai, Yangyang Luo, Ahmed Humayun, David K. Mills
Department of Engineering and Science, Louisiana Tech University, Ruston, LA

2.  Today in orthopedic surgeries the most widely used
biomaterials are metal implants and bone grafts.
 The availability of the right size, appropriate shape,
with desired biofunctionality, antibacterial properties,
biocapability and biodegradability is scarce 1.
 Currently, Calcium Phosphate Cements (CPC) used in regenerative medicine and orthopedic surgery is restricted to
non-load bearing regions such as craniofacial, maxillofacial surgeries or filling hairline bone cracks only 1.
Louisiana Tech University •
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NEED FOR PATIENT SPECIFIC BONE GRAFTS

3.  Bone defects can result from diseases that can be metabolic (Gout), endocrine (Hyperparathyroidism), traumatic (
Stress fracture), degenerative ( osteoporosis, osteoarthritis), and neoplastic ( osteosarcoma) 2.
 Bone is an active tissue but cannot repair itself if the damage is too large an area 3.
 To repair such defects rods, screws, plates and pins are used usually.
 CPCs have been researched since many decades and was approved by FDA in 1996.The composition of CPC is
similar to mineral phase of bone 4.
 These cements are known for their osteoconductive and osteoinductive properties along with bio-
reabsorbility and leads to new tissue formation.
 Due to its low mechanical property, the use of CPCs are limited to non load bearing regions
 The CPCs can be modified using additives such as Strontium, zinc etc.
Louisiana Tech University •
BioMorph
NEED FOR PATIENT SPECIFIC BONE GRAFTS

4.  A soft silver-white chemical element with an atomic number of 38, Strontium (Sr) is an alkaline earth metal
which is not hazardous when occurring in a naturally
stable form 5.
 Sr falls after calcium in the periodic table and shares
many similar properties and is incorporated in bone
repair as Sr2+ (ions) are bone-seeking and can stay
in the body for a long time 6.
 The response of signaling principle and metabolic pathways for calcium follow Sr albeit the effects are weaker
but have almost similar protein binding capacity 6.
 Sr has been shown to have a dual effect of the development and inhibition of degradation by enhancing
osteoblast and inhibition of osteoclast activities.
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WHY STRONTIUM?

5.  Halloysite nanotubes (HNTs) with the chemical formula Al2Si2O5(OH)4.nH2O, are a naturally occurring clay
mineral with a tubular structure and an inner diameter of 10-15 nm and the outer diameter of 50-70 nm, with
average linear dimensions of 50-70 nm 7.
 HNTs have been researched extensively as a delivery system for different chemicals, antibacterial and anticancer
drugs, as an adsorbent, and as a nanofiller to improve mechanical and thermal properties, etc.
 The inner surface of the lumen is positively charged with an external negative surface 7.
 The outer surface has low hydroxyl density which is now targeted to attach metal ions under specific conditions
such as modified surfaces using surfactants, coupling agents, electrostatic adsorption or layer by layer coatings 7,
8.
 The mechanical and biological properties of biomaterials like CPCs can also be enhanced using HNTs 7.
Louisiana Tech University •
BioMorph
HALLOYSITES

6.  Current applications of CPCs in regenerative medicine and orthopedic surgeries are limited to non load bearing
regions
 There is urgent and critical need for osteoconductive and osteoinductive CPCs that have strong mechanical and
anti-infective properties.
 My predecessors in the lab added HNTs to increase the mechanical strength of CPCs
 Our objective in the current study is to :-
 Increase the mechanical properties (such as tensile strength and adhesiveness)
 Drug loading capacity (by loading drugs such as gentamycin sulfate) in HNTs
 Increase the antibacterial and osteoconductive properties of the cement ( By coating Strontium on drug
loaded HNTs)
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GOALS

7.  CPCs have numerous advantages such as durability,
formability, low shrinkage, dense, and a porous nature 8, 9.
 The addition of Halloycites (HNTs) and other
nanoparticles have been used as additives and
have resulted in improving the mechanical stability
of the material and also serving as a drug carrier 2, 10.
 This research aims to develop a novel composite
green Strontium coated HNT (SrHNTs) embedded in CPC
for orthopedic and other biomedical applications.
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CALCIUM PHOSPHATE CEMENT
Calcium
Phosphate
Powder
Liquid
phase
Calcium
Phosphate
Cement
SrHNTs
In Our Lab!!

8. Louisiana Tech University •
BioMorph
STRONTIUM HNT FABRICATION PROCESS
 We proposed that HNTs can be coated with metal carbonates compounds, as metal ions donor, and as NMR shift
reagents—through a simple breakdown of the salt in water.
 This method will result in a free positively-charged metal ion that can readily bond to the negatively-charged HNT
exterior, resulting in metallic coatings forming on the HNT surface. No harmful Chemical or toxic waste is
produced.
Strontium Coated HNTs

9. Louisiana Tech University •
BioMorph
SAFE TO USE SrHNTs !!
 Based on our preliminary data we found that we had successfully coated HNTs using our new safe single step green
process without using any harmful chemicals and did not produce any toxic waste.
 We performed SEM image analysis along with EDS and FT-IR to confirm the presence of Sr on the HNTs.
 We then performed the live dead cytotoxic assay to ensure the safety of the nanoparticles and also get an estimate
of the maximum concentration that could be used in CPC paste without producing harmful effects on the
preosteoblast cells.
 When these nanoparticles are embedded in CPC they will assist with the proliferation of preosteoblast cells.These
tests have paved way for future testing
our green SrHNTs in CPC paste.
SrHNT
Calcium Phosphate
Cement

10. Louisiana Tech University •
BioMorph
FURTHER TESTING
We have more tests to follow up the coatings.
 Material characterization studies will include material strength test of the SrHNT/CPC composites.
 There is a high demand for developing osteoconductive and osteogenic CPC which have a good load bearing
capacity for 3D printing bones for transplantations 19.
 Incorporating SrHNTs in bone structure will result in a strengthening of the bone and will induces bone formation
by osteoblasts while reducing bone reabsorption by osteoclasts along with anti-bacterial and drug loading
capacity.
SrHNT
Calcium
Phosphate
Cement

11. Louisiana Tech University •
BioMorph
THE BIG PICTURE
Embedding these Sr nanoparticles in calcium phosphate paste will enhance the
 Bio compatibility, Osteoconductivity, Osteoinductivity, Biodegradability, Bioactivity, and Mechanical
strength
 We are aiming to make bone grafts that are stronger, cheaper, scalable, tunable and patient specific !!!

12. Louisiana Tech University •
BioMorph
References
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