Fabrication Techniques and Properties of Scaffolds - Biodegradable Polymer-Based Scaffolds for Bone Tissue Engineering - page 27

oxide nanoparticles as a function of zeta potential was studied and it was reported
that electrostatic interactions played an important role in protein adsorption of
nanoparticles (Patil et al. 2007 ). The adhesion of protein on low density polyethyl-
ene (LDPE) was studied and it was described that the surface wettability and con-
tact time had significant effects on protein adhesion to the surface of biomaterials
(Xu and Siedlecki 2007 ).

2.4 In Vitro Degradation of Scaffolds

Study of the hydrolytic degradation mechanism and rate is crucial factors for the
application in biomedical and pharmaceutical applications (Tsuji 2008 ). The deg-
radation mechanism and rate of biodegradable polymeric scaffolds can be affected
by numerous factors (Li 1999 ). The most common reasons for using absorb-
able polymer scaffolds are to accomplish time-varying mechanical properties and
ensure complete dissolution of the implant, eliminating long-term biocompatibility
concerns or avoiding secondary surgical operations. In order to release admixed
materials such as antibiotics or growth factors, scaffold degradation may also be
desired.

2.4.1 Material and Medium Factors Affecting Degradation

The material and medium factors are given in Table 2.1 . Among these factors,
molecular weight, structure and content of comonomer unit, crystallinity, orienta-
tion, blending, porosity, pH, temperature, and catalytic molecules or ions are the

Table 2.1 Material and medium factors which affect degradation behavior and rate (Tsuji 2008 )
No. Material factors Medium factors

1 Molecular structures Temperature, pH

Molecular weight and distribution, tacticity
(optical purity) and distribution,
comonomer structure, content and
distribution, terminal groups, branching,
crosslinks

Solutes (kinds and concentrations)

2 Highly-ordered structures Enzymes (kinds and concentrations)

Crystallinity, crystalline thickness, spherulitic
size and morphology, orientation,
hybridization (blends and composites)

Microbes (kinds, number and culture
conditions)

3 Material morphology Stress or strain

Materials shape and dimension, porosity and
pore size