This document discusses using silicon nanowires for biomedical applications such as bone tissue engineering and drug delivery. It describes how silicon nanowires can be synthesized, coated with calcium phosphate, and modified with compounds like alendronate to stimulate bone formation and regulate cell behavior. The document also explores incorporating silicon nanowires into polymer scaffolds and their potential as delivery vehicles for cancer therapy using boron neutron capture.

1. Silicon Nanowires for Biomedical
Applications
Ke Jiang, Ph.D
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2. Silicon Nanowires for Bone Tissue Engineering?
 Biological Roles of Silicon
Improve bone calcification in rat and chick. Edith M. Carlisle in the 1970s.
Initiate bone calcification in animals and stimulates formation of collagen.
“Significant positive association” between the density of bone and silicon
uptake in men and in premenopausal women.
An essential component in bioactive glasses as bone substitutes.
 Potential Biological Applications of Silicon Nanowires
Biosensor
Drug delivery
Bio-scaffold
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3. Synthesis of SiNWs
VLS Growth Mechanism
1. Annealing of catalysts;
2. Introduction of SiH4;
3. Precipitation of SiNWs
from Si/Au liquid alloy.
3

4. Cathodic Bias-Induced Calcification of SiNWs
SBF = Simulated Body Fluid (pH ≈ 7.3)
Ion Na+ K+ Mg2+ Ca2+ Cl- HCO3- HPO42- SO42-
SBF (mM) 142.0 5.0 1.5 2.5 148.8 4.2 1.0 0.5
Blood
Plasma 142.0 5.0 1.5 2.5 103.0 27.0 1.0 0.5
(mM)
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K. Jiang, D. Fan, Y. Belabassi, G. Akkaraju, J-L. Montchamp, J. L. Coffer, ACS Appl. Mater. Interface. 2009, 1, 266

5. Calcium Phosphate Coated SiNWs (CaP/SiNWs)
Si Si Ca
P
Ca
P
CaP/SiNWs (synthesized by VLS method) CaP/SiNWs (synthesized by OAG method)
Before coating
Si (111)
Si (220)
After coating Graphite
Si (311)
CaP
Graphite
Au
5
K. Jiang, D. Fan, Y. Belabassi, G. Akkaraju, J-L. Montchamp, J. L. Coffer, ACS Appl. Mater. Interface. 2009, 1, 266

6. Effect of Experimental Conditions on Calcification of SiNWs
1 week 2 weeks 3 weeks 4 weeks
SEM images of calcification of SiNWs as a function of immersion time in SBF
(The sample was biased at a current density of 10 mA/cm2 for 90 min)
Effects of Bias Conditions on Ca/Si Ratio Effects of Bias Conditions on Ca/P Ratio
6
K. Jiang, D. Fan, Y. Belabassi, G. Akkaraju, J-L. Montchamp, J. L. Coffer, ACS Appl. Mater. Interface. 2009, 1, 266

7. Surface Modification of CaP/SiNW with Alendronate
Alendronate
 Internalized by mature osteoclasts
 Inhibit resorptive function of
osteoclasts
 Induce apoptosis of osteoclasts
Fluorescent Microscopy of FITC Labled Fluorescent Spectrum of FITC Labled
Alendronate-CaP/SiNWs Alendronate-CaP/SiNWs
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K. Jiang, D. Fan, Y. Belabassi, G. Akkaraju, J-L. Montchamp, J. L. Coffer, ACS Appl. Mater. Interface. 2009, 1, 266

8. Mouse Stromal Cell (MSC) Proliferation
Mouse Stromal Cells (MSCs)
 derived from bone marrow;
 capable of differentiation into
osteoblasts, chondrocytes, and
adipocytes;
 treat disorders such as osteoporosis.
10 µm MSC proliferation on SiNWs, CaP/SiNWs,
glucose bisphosphonate-CaP/SiNWs,
alendronate-CaP/SiNWs
Optical Image of MSC
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K. Jiang, D. Fan, Y. Belabassi, G. Akkaraju, J-L. Montchamp, J. L. Coffer, ACS Appl. Mater. Interface. 2009, 1, 266

9. Silicon Nanowire/Polycaprolactone (PCL) Nanocomposites as
Biocompatible Scaffolds for Bone Tissue Engineering
 SiNWs usually grow on rigid substrates;
 Flexible materials is desired;
 SiNWs incorporated in a polymer matrix;
 Polycaprolactone: slow degradation rate.
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10. Fabrication of SiNW/PCL Composites
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11. Fabrication of SiNW/PCL Composites
Printing Method Embedding Method
1 cm
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K. Jiang, G. Akkaraju, J. L. Coffer, J. Mater. Res. In Press.

12. Acellular Calcification of SiNW/PCL Composites
Embedding Method Printing Method
Cnts Ca Cnts Ca
40
2.0K P
P
20
1.0K
Si
2 4 6 8 2 4 6 8
Energy (keV) Energy (keV)
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K. Jiang, G. Akkaraju, J. L. Coffer, J. Mater. Res. In Press.

13. MSC Attachment on SiNW/PCL Composites
Fabricated by the Embedding Method
SiNWs SiNW/PCL-2 SiNW/PCL-4 SiNW/PCL-6
1 week
2 weeks
3 weeks
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K. Jiang, G. Akkaraju, J. L. Coffer, J. Mater. Res. In Press.

14. MSC Attachment on SiNW/PCL-film Composites Fabricated
by the Printing Method
SiNWs SiNW/PCL PCL Film
3 days
5 days
7 days
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K. Jiang, G. Akkaraju, J. L. Coffer, J. Mater. Res. In Press.

15. MSCs Viability on SiNW/PCL Composites: MTT Assay
15
K. Jiang, G. Akkaraju, J. L. Coffer, J. Mater. Res. In Press.

16. ALP assay: MSC Differentiation on SiNW/PCL Composites
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K. Jiang, G. Akkaraju, J. L. Coffer, J. Mater. Res. In Press.

17. SiNWs as Delivery Vehicles for Boron Neutron
Capture Therapy (BNCT)
 1935 H. J. Taylor; 1936 G. L. Locher.
10
5B + 1 n → [11B] → 4 He2+ + 7Li3+ + γ0.48 MeV + 2.31 MeV
0 5 2 3
 Both α–particles and lithium ions have pathlength
of several micrometers;
 Boron-containing agents: BSH
 Nanomaterials as Delivery Vehicles:
Dendrimer Liposome Dextran 17
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18. SiNWs as Delivery Vehicle for BNCT
120
After Coating
100 Before Coating
80
Counts
60
40
20
0
0 200 400 600 800 1000 1200
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Diameters
K. Jiang, J. L. Coffer, J. G. Gillen, T. M. Brewer, Chem. Mater., 2010, 22, 279.

19. Dissolution of BSH from SiNWs as a Function of Time
0 min 5 min 10 min 15 min
20 min 25 min 30 min 40 min
50 min 60 min 80 min 100 min
120 min 3h 6h 10 h
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K. Jiang, J. L. Coffer, J. G. Gillen, T. M. Brewer, Chem. Mater., 2010, 22, 279.

20. Dissolution of BSH from SiNWs as a Function of Time
Molar Ratio
Time (min)
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K. Jiang, J. L. Coffer, J. G. Gillen, T. M. Brewer, Chem. Mater., 2010, 22, 279.

21. Remarks
 Catalyst-assisted chemical vapor deposition methods were employed
to synthesize SiNWs, which were coated with calcium phosphate by an
electrochemically induced method.
 The alendronate modified CaP/SiNWs exhibit a cytotoxic behavior,
while deliberate subtle modification of the exposed primary amine with
glucose sensitively improves the cytocompatibility of the nanowire vector.
 SiNW/PCL composites with a variety of surface topography were
fabricated and their cytocompatibility were tested in vitro. These
composite materials show supportive behavior of directing mouse stromal
cells attachment, proliferation, and differentiation functions.
 SiNWs can be used as potential delivery vehicles for boron-containing
agents, therefore exhibited some properties favorable for possible use in
Boron Neutron Capture Therapy.
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