Scaffolds for Tissue Engineering - Biodegradable Polymer-Based Scaffolds for Bone Tissue Engineering - page 8

(Lucchesi et al. 2008 ). It was also reported that surface modified PHBV films
could be sterilized by ethanol which promoted osteoblast alignment and confine-
ment (Kenar et al. 2008 ).

1.4 Candidate Biomaterials for Tissue Engineering
Scaffolds

1.4.1 Biopolymers

Polymers are long-chain molecules of high molecular weight made up of a num-
ber of small repeating units linked together by covalent bonds. There are a wide
variety of polymers including natural materials (such as cellulose and collagen)
and synthetic materials (such as polyethylene). If biodegradation is desired of
implants, biocompatible and biodegradable polymers can be used. These polymers
include poly(lactic acid) (PLA), poly(glycolic acid) (PGA), poly(hydroxybutyrate)
(PHB) and its copolymer poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV).
While selecting a biodegradable polymer, apart from other required properties, the
degradation rate of the material is also very much important to see if it matches
with the growth rate of the new tissue (Liu and Ma 2004 ). Table 1.2 shows some
bone regeneration materials and their properties (Seal et al. 2001 ).
PGA, PLA and their copolymers poly(lactic acid-co-glycolic acid) (PLGA) are
a family of linear aliphatic polyesters, which are most frequently used in tissue
engineering. By the degradation of hydrolysis of the ester bonds, these polymers
degrade. PGA is one of the most widely used scaffolding polymers. PGA degrades
rapidly in aqueous solutions or in vivo because of its relatively hydrophilic nature.
It loses mechanical integrity between two or four weeks. The most widely used
scaffolds made by this polymer are the nonwoven fibrous fabrics. PLA is another
widely used polymer for scaffold fabrication. The extra methyl group in the PLA
repeating unit (compared with PGA) makes it more hydrophobic which reduces

Table 1.2 Some bone regeneration polymers and their properties (Seal et al. 2001 )
Material Porous ( μ m) Compressive

strength (MPa)

Modulus (MPa) Support cell

adhesion

PLA NR NR 100-500 Ye s

PLGA 60 ± 20 0.5 (tensile), 150-710 Ye s

Poly(ortho-ester) 4-16 2.4 (Young's) NR Ye s

PLA/HA 6-9 NR NR Ye s

PLA/Ca phosphate NR NR 100-500 Ye s

PLGA/Ca phosphate NR 5 (Young's) 0.25 100-500 Ye s

NR indicates “not reported”