Bioresorption and Degradation of Biomaterials - Tissue Engineering: Cell-Surface Interactions for Tissue Culture - page 318

3 Measurements of Bioresorption ........................................................................................ 322

3.1 ISO Medical Biomaterials Degradation Assays ...................................................... 322

3.2 Cell-Based Resorption Assays ................................................................................. 325

3.3 In Vivo Tests of Biomaterial Degradation .............................................................. 327

4 Conclusions and Outlook .................................................................................................. 327

References ............................................................................................................................... 328

1 Introduction

1.1 Stable and Degradable Biomaterials

By definition, biomaterials come into close contact with tissues of the body [ 1 ].
As soon as this happens, an interaction starts between the body and the material.
Body fluids represent an extremely corrosive mixture of fluid, ions and proteins
[ 1 - 4 ]. Movement of the body leads to mechanical stresses in the form of bending
and shearing forces, which further promote the degradation of the material [ 5 ].
Additionally to this ''passive'' degradation, there is an inflammatory cellular
response to foreign materials, which includes immune cells like monocytes,
neutrophils, lymphocytes, macrophages or osteoclasts, and these cells can actively
participate in the bioresorption (For review see [ 1 ]). The degree and nature of this
foreign body response also depends on the properties of the device, such as material
composition, three-dimensional morphology including porosity, surface structure
and surface chemistry [ 6 - 8 ]. There are two main strategies for dealing with this
tendency of the body to attack external materials: (1) try to find and use materials that
are as inert as possible and do not induce an adverse inflammatory reaction; (2)
integrate the body's innate repair mechanisms into the design of temporary devices,
which can be slowly degraded or replaced by healing tissue when their work is done.
The advantages and disadvantages of these two approaches are directly linked to the
intended application, the site of implantation and the specific patient. An implant
that is designed to last inertly for 20 years inside the body is a good option for a
70-year-old patient. In a 30-year-old patient, or even more in growing children, it is
obvious that a strategy which involves regeneration may be a better solution.
A necessary precondition, limiting the use of temporary supporting or augmenting
biomaterials, however, is sufficient healing or regeneration capacity of the tissue,
ensuring that after healing the implant is no longer needed [ 9 ].

1.2 Medical Applications for Resorbable Biomaterials

Consequently, bioresorbable implants are of great use for the temporary
management of tissue defects in tissues with a usually good healing ability like skin,
bone or tendon. Here fixation of the tissue improves the healing process and after the
tissue is regenerated it can support its own structure without the need of the