Bioactive polymeric nanocomposites for bone tissue engineering

Research area: Polymer science, nanomaterials and biopolymer
Degree: Honours
Supervisor: Prof Naba Dutta

Summary: Bone tissue engineering represents an alternative approach to the replacement of diseased or damaged bone tissue The challenge of tissue engineering is to develop suitable bone replacement materials/scaffolds with desirable mechanical strength, porosity and bioactivity to allow cell adhesion, migration, growth and proliferation, resulting in excellent integration with surrounding tissues [1].

A variety of materials including metals, surface-treated/ceramic-coated metals, bioactive ceramics (particularly calcium phosphate ceramics) have been developed and successfully employed for bone tissue engineering and active bonding with bone, without the formation of an intervening fibrous tissue layer [2-4]. However, bone implants from such materials may subject bone to stress shielding osteopenia due to their very high rigidity and elastic modulus compared to bone [5].

Polymers and polymer-based composites may be an ideal bone substitute, as their mechanical properties, biocompatibility and chemical activity could be tailored and manipulated according to the need and demand. However, most of the traditional synthetic polymeric materials do not exhibit bioactivity and may be subjected to wear, and their wear debris may also lead to particulate-induced osteolysis [6-10]. Therefore, neither bioactive ceramics/metals nor non-bioactive polymers are ideally suited for use as bone substitutes. Despite the shortcomings both these materials are used extensively for bone replacement. There is a significant need and demand for the development of a bone substitute that is bioactive and exhibits mechanical properties comparable to that of bone. 

Recently, organic-inorganic composites, hybrids and nanocomposites have attracted significant attention as an alternative material for bone substitute, because their porosity, mechanical properties, biocompatibility, bioactivity and biodegradability may be tailored and manipulated to suit the need [11-16]. An ideal bone substitute should maintain its mechanical properties as it degrades until the newly regenerating bone can adequately support the loading, however, such biodegradable and biocompatible polymeric composites/nanocomposites are yet to be developed.

In this project, the synthesis of novel polymeric nanocomposites based on poly (ϵ-caprolactone) (PCL)/modified PCL will be attempted and their properties will be evaluated as a bioactive bone substitute. The nanocomposite will be synthesized by the co-condensation of metal alkoxides/organofunctional alkoxide/triethyl phosphate-and PCL end-capped with triethoxy silane (Si-PCL).

The condensation of these reactants will be achieved by sol-gel method. Amphiphilic block copolymer such as poly (ethylene glycol)-block-poly (propylene glycol)-block-poly (ethylene glycol) of desired microstructure and molecular weight will be employed as structural director to control and manipulate the self-organization and porosity of the nanocomposites. The mechanical properties, morphology and porosity of such nanocomposites will be evaluated using standard methods and protocols. Biocompatibility of the composites will be estimated using deposition of apatite crystals (HAp) on the nanocomposite upon exposure to simulated body fluid (SBF).

1. R.Langer, J.P.Vacanti, Science, 260 (1993)1993.
2. L.L.Hench, R.J. Splinter, W.C. Allen, T.K. Greenlee, Jr.J.Biomed Mater Res 2 (1972) 117, 
3. H.M.Kim, F.Miyaji,T. Kokubo, T. Nakamura, J.Biomed Mater Res 32 (1996)409. 
4. J. J. Yoo and S-H. Rhee, J.Biomed. Mater Res 68A (2004)401. 
5. P. Christel, A. Meunier, J.M.Dorlot, J. Winvolet, L. Sedel, P. Bortin in Bioceramics: Materials: Characteristics versus in vivo behavior, Ann NY Acad. Sci. 1988, 523:234. 
6. M.J. Jasty, W.E. Floyd, A.I. Schiller, S.R. Golding, W.H. Harris, J. Bone Joint Surg Am. 68 (1986) 912. 
7. T.T. Glant, J.J. Jacobs, G. Molnar, A.S. Shanbhag, M. ValyonJ. O. Galante, J Bone Miner Res 8(1993) 1071. 
8. B. Derbyshire, J. Fisher, D. Dowson, C. Hardaker, K.Brummitt, Med Eng Phys, 16 (1994) 229.
9. J. Yao, T.T. Galant, M.W. Lark, K. Mikeez, J.J. Jacobs, N.I. Hutchinson, J. Bone Miner Res 10 (1995)1417. 
10. A. Prabhu, C.E. Shelburne, D. F. Gibbons, J. Biomed mater Res 42 (1998) 655.
11. K. Tsuru, C. Ohtsuki, A. Osaka, T. Iwamoto, J.D. Mackenzie, J. Mater Sci., Mater Med 8(1997) 157. 
12. Q. Chen, F. Miyaji, T. Kokubo, T. Nakamura, Biomaterials, 20(1999)1127. 
13. Q. Chen, F. Miyaji, T. Kokubo, T. Nakamura, J. Biomed Mater Res 51 (2000) 605. 
14. Q. Chen, F. Miyaji, T. Kokubo, T. Nakamura J. Mater Sci: Mater Med 12(2001)515.
15. N. Miyata, K. Fuke, Q. Chen, M. Kawashita,T. Kokubo, T. Nakamura, Biomaterials, 23 (2002)3033. 
16. S.H. Rhee, J.Y. Choi, J. Am. Ceram Soc. 85 (2002)1318. M. Kamitakahara, M. Kawashita, N. Miyata T. Kokubo, T. Nakamura, J. Sol-Gel Sci., Technol., 21 (2001)75.

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