Nanocomposites of Cellulose For Medical Application

Asif Rasheed

Lecturer, Department of ChemistryUniversity of Wisconsin, Whitewater

800 West Main Street, Whitewater, WI 53190

rasheeda@uww.edu

Cellulose:• The most abundant, biodegradable and biocompatible

polymer• Applications include fiber, paper, membrane, polymer and

paint industries• Tissue engineering• Nanocomposites

Strong intra and intermolecular hydrogen bonding hence difficult for processing

H - bonding is reduced by partial replacement of hydroxyl groups, this process involves complex multiple steps and uses toxic chemicals => Conern to Environment

Effect on Nano-filler

Cellulose Dissolution

• Ionic Liquid: Able to break down H-bonding in biopolymers, hence can dissolve biopolymers e.g. cellulose and silk

Cellulose pulp paper (Grade V-60) from Buckeye Technologies Inc.

Degree of Polymerization ~ 820

Control cellulose film regenerated from ionic liquid

NNH3C

O

O

CH3

CH3

1-ethyl-3-methylimidazolium acetate (EMI acetate)

1) Composites of cellulose and vapor grown carbon nanofiber (VGCNF) and carbon nanotubes

2) Composites of cellulose and hydroxyapatite (HAP)

1) Cellulose-CNT Nanocomposite

• Young’s Modulus ~ 1 TPa

• Electrical Conductivity

• ~ 100 times Stronger than Steel at 1/6th of weight

• Thermal Conductivity

SWNT MWNT VGCNF

Previous Experience with Polyacrylonitrile (PAN)/VGCNF Nanocomposites

2

4

6

8

0 5 10 15 20 25 30 35 40

VGCNF (wt %)

Spec

ific

Mod

ulus

(GPa

.cm

3 /g)

(b)

(a)

(d)

(c)

(e)(A)

(a) Exp.(b) Theo. (0.2 μm)(c) Theo. (1μm)(d) Theo. (10 μm)(e) Theo. (100 μm)

Experimental and theoretical specific modulus of various PAN/VGCNF composite films assuming the modulus of VGCNF to be 50 GPa. (a) Experimental modulus, (b) theoretical modulus assuming VGCNF length to be 0.2 m, (c) 1 m, (d) 10 m and (e) 100 m.

y = 1.291x + 3.4417R2 = 0.9506

-2

-1

0

1

2

3

4

-1.6 -1.2 -0.8 -0.4 0.0

log (V-Vc)

log

(con

duct

ivit

y)

-2

0

2

4

0 0.2 0.4 0.6 0.8

V

log

(con

duct

ivity

)

Electrical conductivity of PAN/VGCNF composite films.

0.0

0.1

0.2

0.3

0.4

0.5

20 40 60 80 100 120 140 160

Temperature (oC)

Tan

δ

(a)

(d)

(b)

(e)

(f)

(a) Control PAN(b) PAN/VGCNF (5 %)(c) PAN/VGCNF (10 %)(d) PAN/VGCNF (20%)(e) PAN/VGCNF (40%)(f) PAN/VGCNF (90 %) (c)

Tan δ (below) as a function of temperature for (a) Control PAN, (b) PAN/5%VGCNF, (c) PAN/10%VGNCF, (d) PAN/20%VGCNF, (e) PAN/40%VGCNF and (f) PAN/90%VGCNF composite films.

Guo, H.; Rasheed, A.; Kumar, Satish J Mater Sci (2008) 43:4363-4369

Mechanical Properties Electrical Conductivity Thermal Stability

• Electroactive paper• Actuators/sensors• Medical Devices

Cellulose+5%VGCNF

Incorporation of a nano-filler (SWNT, MWNT, VGCNF) into cellulose matrix is expected to

• Enhance tensile strength and tensile modulus

• Impart thermal stability

• Reduce shrinkage (dimensional stability)

• Result in electrical conductivity in the nanocomposite

2) Cellulose/Hydroxyapatite Nanocomposites

• Hydroxyapatite (HAP) Ca10(PO4)6(OH)2 finds many applications as bio-material

• Filler to replace amputated bone• Coated to promote bone in-growth into prosthetic implants• Cellulose Hydroxyapatite composites have great potential to

be used in bone tissue engineering

Previous Reports: Cellulose/HAP Composites

• Precipitated on cellulose in-situ from aqueous solution*• Deposition of HAP limited to surface• The process is extensively long (up to ~14 days) to prepare the

composite

*Materials Letters 60 (2006) 1710-1713

Hong, L.; Wang Y. L.; Jia, S. R.; Huang, C. G.; Wan, Y. Z. 2005. Hydroxyapatite/bacterial Cellulose Composites Synthesized via Biomimetic Route. Materials Letter. 60:1710-1713

Current Approach

• Homogenous dispersion of HAP in cellulose matrix

• Fast processing• Composition of composite

can be easily varied

Cellulose+10% HAP Cellulose+60% HAP

Acknowledgments

• Students (Peter Zastraw, Matthew Magruder, Travis Martin)• Prof. Peter Jacobs (Geology Department, UW-Whitewater)

for XRD• UW-Whitewater for funding• Department of Chemistry, UW-Whitewater

Cellulose/HAP Composites: XRD

Testing for biocompatibility