DESIGNING NANOFIBROUS SCAFFOLDS FOR TISSUE ENGINEERING - Advanced Biomaterials: Fundamentals, Processing, and Applications - page 451

solutions with PVA, followed by photo cross-linking by triethylene glycol diacry-
late (TEGDA). The electrospun QCh/PVA fi bers had diameters in 60-200 nm
range [152]. The study demonstrated that an increase in QCh content in QCh/
PVA solution resulted in an increase in solution conductivity, thereby leading to
a decrease in the diameter of the electrospun nanofi bers [152] .
Chitosan is thus expected to be of great value as a scaffold material for tissue
engineering with the combination of biocompatibility, intrinsic antibacterial
activity, ability to bind to growth factors, and ability to be processed in a variety
of shapes [153].
Encouraging results obtained after electrospinning of a few natural polymers
has provided researchers an opportunity to explore other natural polymers, as
well as their blends with other natural or synthetic polymers. Although natural
polymers are a better choice for the synthesis of scaffolds for tissue engineering,
they are still limited in their applications because of certain concerns like deple-
tion of natural resources, risk of potential pathogen transmission, elicitation of
immune response, limited control on molecular weight, and consequential degra-
dation and mechanical properties [154].

13.4.2 Synthetic Polymers
Synthetic polymers have an advantage over natural polymers in that they can be
modifi ed or tailored depending upon the requirement for a specifi c biomedical
application. In addition, one can also circumvent the batch-to-batch variability in
properties as well as the reduced availability (in some cases) that are associated
with natural polymers. Since synthetic polymers allow for a greater degree of
control on properties (physical and chemical), they are a more desirable source of
raw materials for biomedical applications. For example, polymer modifi cations
(physical/chemical) can be advantageous for the immobilization of bioactive
agents that can be very useful in drug delivery and tissue engineering applica-
tions. Amongst the available synthetic polymers, the ones more suitable for tissue
engineering applications are most often the degradable types. Within this sub-
class, hydrolytically degradable polymers are preferred over the enzymatically
degradable polymers to avoid any patient-to-patient variation in degradation
profi les when used as implants. This section discusses various synthetic hydro-
lytically degradable polymers that have been electrospun and applied in tissue
engineering.

-hydroxy) esters are a family of
polymers that contain hydrolytically cleavable ester linkages in their aliphatic
back-bone chain. These thermoplastic polymers can be synthesized by ring
opening or condensation polymerization reactions, depending upon the mono-
mers used [155,156]. The most common amongst the class of poly(

13.4.2.1 Poly( a -hydroxy) Esters. Poly( α

- hydroxy)
esters are the Food and Drug Administration (FDA) approved poly(glycolic
acid) (PGA), poly(lactic acid) (PLA) and poly(lactide-co-glycolide) (PLGA).

α