Tissue Engineering is a relatively new area,
involving cell biology and materials science. Acceptable values
for many of the important parameters of effective tissue scaffolds
have not been established, and in some cases.
Porosity of tissue scaffolds is universally accepted as an important
parameter, however there is significant variability as to precisely
what aspects of porosity are important, or how best to measure
them.
Experimental Approach
We have initiated a collaborative project of
testing and analysis through ASTM (F04.42.06) to establish a
reference material for scaffold porosity. There are three candidate
manufacturing methods under consideration for fabricating the
reference scaffolds.
Image analysis will be the primary characterization method for
reference materials. Preliminary collaborative work will lead
to the establishment of parameters for image analysis, establishment
of ancillary test methods, and selection of a manufacturing
method for fabrication of reference scaffolds.
We have been joined in the experimental effort by researchers
at the FDA, University of Connecticut, Mayo Clinic, Case Western
Reserve, National University of Singapore, Midwest Orthopedic,
National Physical Laboratory, Queen Mary University, Macropore
Biosurgery, and Queen’s University. Eight other industrial
and academic laboratories have indicated interest in participating
in data analysis and discussion.
Immunofluorescence
An anti-vinculin antibody and a fluorescent secondary antibody
were used to stain vinculin.
Stained cells were examined by confocal fluorescence microscopy.
Results
Begun characterization of candidate scaffolds
by x-ray ?-CAT and by experimental methods
Indications that imaging and image analysis methods must be
carefully applied in order to get reliable correlation with
experimentally determined values. Thresholding and image quality
evaluation are key factors.
Organizing ASTM imaging / image analysis workshop for May 2005
Preparing image quality metrics to be applied preliminary to
quantitative morphology analysis
Future Activities
Precise definition of critical parameters
Identification of scaffold material and fabrication technique
Round Robin – like activity for measurements of parameters
for which standard artifact will be produced.
Publications
ASTM
draft guide for scaffold characterization (in preparation)
ASTM draft guide for image analysis (in preparation)
Society of Biomaterials Meeting Abstract (2004)
World Biomaterials Meeting Abstract (2004)
Contributors
Marcus Cicerone*
John Tesk
Francis Wang
Joy Dunkers
Martin Chiang
Fred Phelan
Biomaterials Group
Polymers Division
Materials Science and Engineering Laboratory
ASTM
draft guide for scaffold characterization (in preparation)