Brief presentation on Composite materials MME Dept IIT Kharagpur

1. Biodegradable Polymer
Matrix Nanocomposites
For Tissue Engineering
Anand Singh 09MT3904
Nandan Kumar 09MT1027
Piyush Verma 09MT3018
Department of Metallurgical and
Materials Engineering
IIT Kharagpur

2. Tissue Engineering
• Use of cells to repair the damaged biological tissue, leaving only
natural substances to re-establish organ function.
• Challenge: appropriate design and fabrication of porous,
biodegradable, and biocompatible scaffolds.

3. What are Scaffolds?
• Cells are often implanted or 'seeded' into an artificial structure
capable of supporting 3-D tissue formation called Scaffolds.
• Scaffolds act as substrate for cellular growth, proliferation, and
support for new tissue formation.

4. Biomaterials
• Materials used for tissue engineering applications must be designed
to stimulate specific cell response at molecular level.
• Characteristics: Direct cell attachment, proliferation, differentiation,
and extracellular matrix production and organization.

5. Objective
• Fundamental requirements of biomaterials:
i. biocompatible surfaces
ii. favourable mechanical properties.
• Conventional single-component polymer materials cannot satisfy
these requirements.
• Multi-component polymer systems

6. Why Nanotechnology?
• Biological components, such as DNA, involve nano-dimensionality,
hence it has logically given rise to the interest in using
nanomaterials for tissue engineering.
• Enables the development of new systems that mimic the complex,
hierarchical structure of the native tissue.
• Nanomaterials have inherent high surface area-volume ratio
• Available polymeric porous scaffolds revealed insufficient stiffness
and compressive strength

7. Nanocomposites
• Nanocomposite materials often show an excellent balance between
strength and toughness
• Major Factor: Interface adhesion between nanoparticles and
polymer matrix
• Mechanical properties are dependant on
i. properties of the matrix
ii. properties and distribution of the fillers
iii. interfacial bonding
iv. synthesis or processing methods
• Surface modification of nanostructures is needed to promote better
dispersion of fillers and to enhance the interfacial adhesion.

8. Polymer Matrices For Bio-nanocomposites
• Polymers are the primary materials for scaffold fabrication
• Major Types:-
1) Natural-based materials: Biological recognition, poor mechanical
properties, limited in supply, costly. Eg. Polysaccharides (starch,
alginate, chitin/chitosan, hyaluronic acid derivatives) or proteins
(soy, collagen, fibrin gels, silk)
2) Synthetic polymers: relatively good mechanical strength, shape
and degradation rate can be easily modified, surfaces are
hydrophobic, lack of cell-recognition signals. Eg. Poly(lactic acid)
(PLA), poly(glycolic acid) (PGA), poly(3-caprolactone) (PCL), poly
(hydroxyl butyrate) (PHB)

9. Nanostructures For Bio-nanocomposites
 Hydroxyapatite (HA)
• Hydroxyapatite (Ca10(PO4)6(OH)2) is the major mineral component
(69% wt.) of human hard tissues
• It possesses excellent biocompatibility with bones, teeth, skin and
muscles
• Promotes faster bone regeneration, and direct bonding to
regenerated bone without intermediate connective tissue.
• Problems:
i. brittleness of the HA
ii. lack of interaction with polymer

10. Contd..
 Metal nanoparticles
• Nanoparticles of noble metals exhibit significantly distinct physical,
chemical and biological properties from their bulk counterparts
• Their electromagnetic, optical and catalytic properties of noble-metal
nanoparticles such as gold, silver and platinum, are strongly
influenced by shape and size
• Aim: To obtain small particle sizes, narrow size distributions and
well-stabilized metal particles.
• Silver (Ag) has been known to have a disinfecting effect and has
been commercially employed as antimicrobial agent.
• Problem: They are easily aggregated because of their high surface
free energy, and they can be oxidized or contaminated in air.

11. Contd..
 Carbon nanostructures
• Fullerenes, carbon nanotubes (CNTs), carbon nanofibres (CNFs),
graphene and a wide variety of carbon related forms.
• Regular geometry gives CNT excellent mechanical and electrical
properties.
• By dispersing a small fraction of carbon nanotubes into a polymer,
significant improvements in the composite mechanical strength have
been observed.
a) Covalent Functionalization: Fluorine, radicals, amine groups, etc. are
attached to the CNT sidewall, play a determinant role in the mechanism of
interaction with cells.
b) Non-covalent attachment: SWCNTs is not damaged and their properties
remain intact, forces between the polymer and the SWCNTs are very weak

12. Processing Techniques
 Electrospinning:

13. Contd..
• Electrospun using a high voltage power supply at 20 kV potential
between the solution and the grounded surface
• The PLLA/HA mixture was loaded in a 20mL glass syringe equipped
with a blunt 23 gauge needle
• The ground collector (9 cm in diameter) located at a fixed distance
of 15 cm from the needle.
• The flow rate of the solution and the spinning time were set to
0.85mL/h and 8 h, respectively

14. Contd..
 Foaming Technology:
• Objective - To produce porous structure in matrix.
• Material used to produce porosity-Supercritical CO₂
• Matrix – Poly Lactic Acid (PLA)
• Reinforcement – Nano Hydroxy Apatite (nHA)
PLA Hydroxy Apatite

15. Contd..
Why PLA?
• Biodegradable
(Gradually transforms loads to the bone as organ heals)
(Medical implants in the form of screws, pins, rods, and as a mesh)
Why supercritical CO₂ ?
• Non-toxic, non- flammable , noncorrosive, abundant, inexpensive, commercially available in high
purity, and readily accessible supercritical conditions ( Critical Temperature = 31.1˚C and Critical
pressure = 7 37MPa)
Why nHA ?
• Nanocrystalline HA (nHA) enhances osteoblast adhesion and surface deposition of calcium-
containing materials. (with respect to Bone-tissue growth).
• Inorganic calcium-containing constituent of bone matrix and teeth, imparting rigidity to these
structures

16. Contd..
Steps involved:
• Firstly amorphous or semi-
crystalline polymer is saturated with
CO₂ at temperature 31.1 and
pressure 7.37 Mpa, with the
diffusion of gas into polymer matrix,
it forms single-phase polymer/CO₂
solution.
• When the equilibrium is reached,
pressure is reduced or temperature
is increased or both, so that the
supercritical CO₂ turns into gas and
escape out of the polymer leaving
pores

17. Contd..

18. Applications
• Fracture fixation
• Interference Screws
• Meniscus Repair
• Suture anchors
• Suture coating
• Dental and orthopedic implants
• Drug delivery

19. References
• Z.C.Xing, S.J.Han, Y.S.Shin and I.K.Kang, Fabrication of
Biodegradable Polyester Nanocomposites by Electrospinning for
Tissue Engineering, Journal of Nanomaterials, v 2011, pp 1-18
• X.Shi, J.L.Hudson, P.P.Spicer, J.M.Tour, R.Krishnamoorti and
A.G.Mikos, Injectable Nanocomposites of Single-Walled Carbon
Nanotubes and Biodegradable Polymers for Bone Tissue
Engineering, Journal of Biomacromolecules, v 7, 2006, pp 2237-
2242
• Xia Liao, Haichen Zhang, and Ting He, Preparation of Porous
Biodegradable Polymer and Its Nanocomposites by Supercritical
CO2 Foaming for Tissue Engineering, Journal of Nanomaterials,
Volume 2012, Article ID 836394, pp 1-12.

20. Thank You