Page 187 - Biodegradable Polyesters

7.3 Improving the Bioactivity of Electrospun Polyesters 165

The results showed that RGDS were successfully immobilized on the PLLA scaf-
folds via plasma treatment. When the RGDS were immobilized on the PLLA sur-
face, they promoted attachment of rat osteosarcoma (ROS), osteoblast-like cells
onto the PLLA, resulting in higher cell densities in the RGDS immobilized scaffold
than in the unmodified scaffold. The results suggested that the immobilization of
RGD (Arg-Gly-Asp) peptides makes PLLA scaffolds more suitable for culture of
osteoblast-like cells and facilitates their application in bone regeneration.
Because of the numerous advantages, plasma surface modification of
biodegradable polymers demonstrates great potential and it has been the
focus of interesting reviews on this subject [12, 67, 69–75]. In particular, recent
achievements on plasma modification of biodegradable aliphatic polyesters have
received particular attention due to the fact that these biodegradable polymers
can play a major role in tissue engineering, such as three-dimensional porous
scaffolds. In the past decade, the use of nonthermal plasmas for polymer surface
modification has become a fast growing field of research.

7.3.1.3 Ozone
Plasma and chemical vapor deposition methods have been extensively used for
improving the wettability and adhesion properties of polymer surfaces. Surface
treatments by gas-phase ozonation under irradiation of UV light have also been
a common technique used for surface modification of polymers and for remov-
ing organic contaminants on inorganic substrates [76–86]. Dry surface treatment
methods, such as oxygen plasma, corona discharge, or UV radiation in combi-
nation with ozone, can modify the physical and chemical properties of substrate
surfaces, facilitating the interactions and contacts between two dissimilar phases
without affecting the properties of the bulk material.
In contrast to plasma techniques, UV–ozone (UV/O ) treatment is milder
3
than the oxygen plasma due to the absence of high kinetic energy particles.
Compared to other dry surface treatment techniques, UV/O methodology is
3
important in that the process can be conducted under atmospheric pressure and
hence the equipment and running costs are relatively low. In addition, the use of
a dry medium eliminates the need for immersing the whole device/component in
a solution for treatment. The above properties of the UV/O methodology allow
3
it to be used in a wide range of applications [81].
Oxygen plasma and UV/O treatments are often used industrially for cleaning
3
(long exposure times) or introducing oxygen species to organic surfaces (short
exposure times). Short-time oxidation treatments can be extremely effective
to improve the adhesion between polymer surfaces and other surfaces. UV/O
3
is especially important for improving adhesion between multilayer films for
packaging and for modifying the surface of biologically compatible polymers [85,
86]. Ozonation treatment with UV light can easily be carried out with a variety of
media, such as gas, solvent, and solution, without the need for a vacuum system
and complex experimental equipment. For instance, a combination of ozone
aeration and UV irradiation was used to study the introduction of amine and
amide groups on a polystyrene (PS) surface in aqueous ammonia solution [87].