INTRODUCTION TO PROCESSING OF BIOMATERIALS - Advanced Biomaterials: Fundamentals, Processing, and Applications - page 242

processes has demonstrated that cells interact with implanted biomaterial via
surface integrin receptors and show changes in cellular fate processes depending
on the type and scale (macro/micro/nano) of the interaction [9, 10]. Therefore, via
modifi cations in surface chemistry/topography of biomaterials, it is possible to
alter cellular fate processes such as adhesion, migration and proliferation [11-20].
These cues were substantially implemented in designing biomaterials to improve
biointegration and biocompatibility which in turn led to the development of
advanced processing techniques. Initially, strategies for modifi cation of surface
topography involved different types of lithography and other surface etching
techniques, whereas modifi cation of surface chemistry involved various grafting
techniques.
The last few decades have witnessed a rapid growth in the area of micro/
nanotechnology that has signifi cantly infl uenced the fi eld of bioengineering.
This has, in turn, initiated the utilization of sophisticated tools (such as novel
lithographic techniques, direct writing to create surface nanotopography) that
can enable improved contact guidance [21, 22] of cells on biomaterials when
compared to conventional surface modifi cation techniques. Improved properties
demonstrated by these micro/nano surface modifi ed implants [23] has also opened
up new methods to fabricate biomaterial-based devices having dimensions in the
cellular and sub-cellular scale (or more precisely micrometer and nanometer
scale) applications.
This chapter is meant to provide the reader with an introduction to the area
of biomaterial processing and to enable a better understanding of other chapters
in this section. In the fi rst part, various conventional as well as advanced process-
ing techniques (manufacturing, fi nishing, and sterilization) for four major classes
of materials (metals, ceramics, polymers, and composites) used as biomaterials
has been explained in brief. The second part of this chapter discusses advanced
techniques used for micro/nanometer scale modifi cation and fabrication.
8.3 PROCESSING OF BIOMATERIALS
8.3.1 Metals
8.3.1.1 Introduction. Metals, as biomaterials, have been used for a wide
variety of biomedical applications. For example, in orthopedics, metals are used
for bone and joint replacement in the form of fracture fi xation plates, simple
metallic wires, and screws. Besides orthopedic applications, metals are also used
in other biomedical applications such as dental implants, electrodes in neural im-
plants, in heart valves, and in pacemakers [24].
Most biomedical applications of metals demand some basic properties like,
non-toxicity/biocompatibility, corrosion resistance and good mechanical proper-
ties that include static and cyclic load-bearing capabilities, tensile yield and ulti-
mate strength, modulus of elasticity, fatigue endurance limit and toughness [28].
Since the aforementioned properties are largely infl uenced by the processing that