Bioresorption and Degradation of Biomaterials - Tissue Engineering: Cell-Surface Interactions for Tissue Culture - page 323

Table 1 Biomaterial resorption assays

Analyzing principle Pros Cons

In vitro
ISO 10993-
(13-15)

Weight changes after
direct contact with
simulated in vivo
fluids

Standard assay, easy to
conduct and analyze

Many of the in vivo
biomaterial resorption
factors (e.g., growth
factors, body
temperature, cells,
hormones) are not
considered

Cell-based
resorption
assays

Analysis of material
surface change after
cell mediated
bioresorption

Cells, which are a major
resorption factor are
considered;
individualized
assessment possible

Not all the in vivo factors
can be included; it is
difficult to standardize
the procedure;
resorption analysis is
sometimes difficult

In vivo
Implantation
in animals

To mimic the in vivo
human environments
as closely as possible,
evaluation by
histology or imaging

Complete physiological
environmental
conditions

Ethical issues, expensive

Clinical
studies

To detect human-specific
effects with all the
clinical level tests

Valid results Ethical issues, safety issue

for clinical trial
candidates

materials are developed and tested in different countries by different groups, the
results can still be compared to each other. ISO 10993 is a series of such standards
designed to evaluate the biocompatibility of medical devices before clinical
evaluation. It is now the generally accepted standard procedure for the evaluation
of medical devices. There are three parts to the ISO 10993 used for analyzing
biomaterial degradation: (1) ISO 10993-13: Identification and quantification of
degradation products from polymeric medical devices; (2) ISO 10993-14: Iden-
tification and quantification of degradation products from ceramics; (3) ISO
10993-15: Identification and quantification of degradation products from metals
and alloys. These three parts cover all the important current degradable materials
for medical purposes.

3.1.1 ISO Degradation Assays for Polymeric Materials

For polymeric biomaterials, such as collagen, PLA, PCL or PGA, ISO 10993-13 is
the suitable test. ISO 10993-13 has two major parts: (1) the accelerated degradation
test and (2) the real-time degradation test. Accelerated degradation testing is
mainly used for a first assessment of general degradability of such biomaterials in
vivo. The principle of the accelerated test is to immerse the material in a simulated