Bioactive Glass-Based Coatings and Modified Surfaces: Strategies for the Manufacture, Testing, and Clinical Applications for Regenerative Medicine - Biological and Biomedical Coatings: Processing and Characterization - page 398

TABLE 9.10
Qualitative or Quantitative Approaches of Cellular Testing

Approach TestAim TestObjectives

Qualitative To evaluate the possible

performance of the test material
at a simulated bony site

To assess the:
• Morphology and attachments of cells on the surface
• Production and subsequent calcification of
extracellular matrix

Quantitative To quantitatively assess cellular

physiology/function

To measure:
• Cellular viability
• Cellular proliferation
• Expression of osteoblastic phenotype
• Production and subsequent calcification of
extracellular matrix
• Production of bone specific proteins (e.g., osteoclacin,
osteonectin)
• Alkaline phosphatase activity
• Nucleic activity

Mature, differentiated cells (e.g., fibroblasts, chondrocytes, osteoblasts, and osteoclasts)
isolated from connective tissues are usually employed and cultured on bioactive glass sur-
faces. Cells capable of redifferentiation (e.g., stem cells and marrow stromal cells) have also
been cultured either on bioactive surfaces or exposed to their ionic dissolution products to
assess their ability to control stem cell growth and differentiation. For specific examples of
cellular interactions with bioactive surfaces (bulk, particles, extracts, and composite), see
Tables 9.11 to 9.14.
Cell cultures remain simplistic tests in that they do not include the fluid circulation or
interactions with multiple cell types and/or proteins. In addition, mechanical loading fac-
tors are not taken into account. However, these shortcomings are masked by the significant
amount of biological data obtained from traditional qualitative and quantitative testing
strategies.

In Vivo Testing

The goal of in vivo testing of a medical device is to determine the safety or biocompat-
ibility of the device in a biological environment. In vivo testing is the final phase in the
NAMSA safety evaluation of the medical devices process (see Table 9.8).
As mentioned previously, bioactivity testing via immersion in SBF cannot be taken as a
direct indicator that a candidate material with elicit bioactivity in vivo. In addition, bioactivity
testing and cellular testing both cannot determine the rate of complex tissue attachment and
also the quality/strength of attachment (as indicated by mechanical pull-out tests). Figure
9.9 shows typical in vivo interfacial adherence of Bioglass ® composition (BGC) and A/W
glass-ceramic (A/W) with bone (B). Due to their compositional related bioactivities, the
interfacial strength was shown to be higher than the material strength, resulting in bulk
material fracture failure at the implant/tissue interface [24].
Testing protocols designed for in vivo characterization of bioceramics are too numerous
to be included in this chapter but in Tables 9.15 and 9.16, I have presented some specific
examples. The reader should refer to the excellent review by Hollinger and Citron to find
out more about in vivo testing protocols [23].