Bioresorption and Degradation of Biomaterials - Tissue Engineering: Cell-Surface Interactions for Tissue Culture - page 319

biomaterial [ 10 ]. For the same purpose, non-resorbable materials can also be used,
but these have to be actively removed after the treatment, resulting in additional
operations with all the complications for the patient, including pain and costs [ 10 ].
Widely used applications of biodegradable materials are therefore sutures and
bands for the closing of soft tissue wounds or in the repair of tendons and liga-
ments [ 11 ]. Gauzes, felts and velour dressings made of biodegradable fibers are
used in the treatment of burns or traumatic injuries [ 12 ]. Degradable polymeric
meshes have been studied for their use in arterial grafting [ 13 - 16 ] and for sple-
norrhaphy and pelvic peritoneum reconstruction [ 17 ].
Bioresorbable implants have also been used in orthopedics and traumatology
[ 18 ]. The use of bioabsorbable osteosynthetic screws, pins and nails in patients with
peri- and intra-articular fractures has been shown to lead to bony union without any
abnormal blood levels, infections or foreign body reactions [ 10 , 19 , 20 ].
In bone, controlled degradation can have an additional benefit. Bone is constantly
remodeled and adapted to the load it has to bear [ 21 ]. A rigid fixation with a stiff
implant will lead to decreases in stress levels inside the bone (stress shielding) which
results in active degradation of the bone tissue by osteoclasts with deleterious effects
on the mechanical properties of the bone [ 1 , 22 - 25 ]. Ideally, controlled degradation
of a temporary material leads to consecutive loss of mechanical strength of the device
which in turn leads to slowly rising forces in the healing tissue, thereby enhancing the
healing process and avoiding the unwanted consequences of stress shielding.
For medical devices in the cardiovascular system like intravascular stents, the
mechanical forces are also important. An implant made of such a material should
be able to function fully under constant blood flow until the diseased vessel
completely recovers. After that, the stent should be gradually dissolved, consumed
or absorbed [ 26 ].
Apart from these long-used applications, progress in the development of novel
biomaterials has enabled the invention of a variety of novel medical technologies,
like drug and gene delivery systems, tissue engineering and scaffold-based cell
therapies, organ printing, nanotechnology-based diagnostic systems and micro-
electronic devices [ 27 ].
2 Biodegradable Materials
The materials utilized for temporary biomedical devices include metals, ceramics,
glasses, polymers and composites of the former [ 1 , 28 ].
2.1 Metals
After decades of designing strategies to minimize the corrosion of metallic biomate-
rials, there is a growing interest in using corrodible alloys in a number of medical
applications [ 29 ]. When metals are used in implants, corrosion is always a concern