BIOMATERIAL APPLICATIONS - Advanced Biomaterials: Fundamentals, Processing, and Applications - page 536

nucleic acids, “DNA chips,” are characterized by high densities of biological infor-
mation. Although these technologies are now highly developed and widely used,
they are far from optimized. Additional challenges arise in the fabrication of
protein arrays. Unlike nucleic acids, which share a common physical chemistry
that is largely independent of sequence, proteins are highly diverse in terms of
charge, hydrophobic character, and so on. There is as yet no consensus regarding
the preferred method(s) of array fabrication, and further development will be
required before protein arrays become widely available for use in research and
clinical practice.
One area of increasing attention has been the development of shape-memory
materials that have one shape at one temperature and another shape at a differ-
ent temperature. Such materials might permit new medical procedures. For
example, current approaches for implanting medical devices often require
complex surgery followed by device implantation. Shape-memory materials
might provide such an opportunity because they have the ability to memorize a
permanent shape that can be substantially different from an initial temporary
shape. Thus bulky devices could potentially be introduced into the body in a tem-
porary shape, like a string, that could go through a small laproscopic hole, but
then be expanded on demand into a permanent shape (for example, a stent, a
sheet, and so on) at body temperature. New polymers have been synthesized with
this concept in mind, including phase-segregated multiblock copolymers whose
starting materials are known as biocompatible monomers, such as

ε - caprolactone,

p - dioxanone, and polydimethacarylate (Figure 15.5 ).
The development of high-throughput approaches to create novel biopoly-
mers and screen them for various applications is garnering increased attention.
For example, polymer libraries have been created and then screened for different
applications. This type of high-throughput approach has also been used in the
creation of gene therapy agents.
Microfabrication is a new approach that is gaining importance and may play
a vital role in the development of new biomaterials and delivery systems. They
have been used to make drug delivery silicon chips containing a combination of
drugs in different wells and each drug can be released from the wells upon appro-
priate stimulation. Microfabrication has also been used in the creation of sensors
for treatment of glaucoma as well as for needle-free drug delivery.

15.4 BROAD OVERVIEW OF BIOMATERIAL APPLICATIONS SECTION

In the application section of this topic, various aspects of tissue engineering, syn-
thetic heart valve and blood substitutes have been discussed. In particular some
interesting aspects of neural tissue engineering have been included in the chapter
contributed by Surya K. Mallapragada. Briefl y, various aspect of differentiation
and proliferation of neural progenitor cells (NPC) have been elaborated, includ-
ing current state of the art research in this area. Different parameters affecting
NPC differentiation and proliferation in vitro , especially the role of electric