Biomedical Engineering Reference
In-Depth Information
3. Polymeric biomaterials
Some polymeric biomaterials such as hydrogels are made of water-soluble molecules,
connected usually by covalent bonds, forming a three-dimensional insoluble network. The
space between chains is accessible for diffusion of solutes and this space is controllable by
the level of cross-linked (connected) molecules. They usually show good biocompatibility in
contact with blood, body fluids, and tissues. Therefore, they are very often used as
biomaterials for medical purposes, for instance contact lenses, coating of catheters, etc.
Biomaterials are defined as materials that can be interfaced with biological systems in order
to evaluate, treat, augment, or replace any tissue, organ, or function of the body.
The clinical application of a biomaterial should not cause any adverse reaction in the
organism and should not endanger the life of the patient; any material to be used as part of a
biomaterial device has to be biocompatible. The definition of biocompatibility includes that
the material has to be nontoxic, non-allergenic, noncarcinogenic, and non-mutagenic, and
that it does not influence the fertility of a given patient. Preliminary use of in vitro methods
is encouraged as screening tests prior to animal testing. In order to reduce the number of
animals used, these standards use a step-wise approach with review and analysis of test
results at each stage. Appropriate in vitro investigations can be used for screening
prospective biomaterials for estimations of toxic effect. Cytotoxicity in vitro assay is the first
test to evaluate the biocompatibility of any material for use in biomedical devices (Rogero
et.al. 2003).
Hydrogels can be synthesized by accomplishing crosslinking via -irradiation (Guven, O;
et.al. 1999, Saraydın et.al. 1995, 2002, Karadağ et. al. 2004). However, little work is done on
the biomedical applications of the hydrogels prepared by crosslinking of a homo- or
copolymer in solution with -irradiation. It is well known that the presence of an initiator
and a crosslinking agent affects the macromolecular structure and phase behavior of
hydrophilic polymers in solution and contributes to inhomogeneity of the network
structure. It is argued that more homogeneous network structures can be synthesized, if
crosslinking is accomplished with -irradiation in the absence of an initiator and a
crosslinking agent. The structural homogeneity of the network affects the swelling behavior
and mechanical properties that improved the biological response of materials and
subsequently the performance of many medical devices (Benson 2002). Thus, looking to the
significant consequences of biocompatibility of biomaterials, we, in the present study, are
reporting the results on the biocompatibility with the copolymeric hydrogels prepared with
acrylamide (AAm) and crotonic acid (CA) or itaconic acid (IA) or maleic acid (MA) via
radiation technique. The selection of AAm as a hydrophilic monomer for synthesizing
hydrogel rests upon the fact that it has low cost, water soluble, neutral and biocompatible,
and has been extensively employed in biotechnical and biomedical fields. On the other
hand, CA monomer consists of single carboxyl group, while IA and MA monomers are
consisting of double carboxyl groups. These carboxylic acids could provide the different
functional characteristics to acrylamide-based hydrogels. So, these monomers were selected
for the preparation of the hydrogels and their biocompatibility studies.
In our previous other works,
in vitro
swelling and biocompatibility of blood
in vivo
biocompatibility of radiation crosslinked acrylamide co-polymers such as acrylamide
(AAm), acrylamide/crotonic acid (AAm/CA), acrylamide/itaconic acid (AAm/IA) and
