= Scaffold degradation
<Scaffold degradation> is the progressive alteration or breakdown of a <tissue-engineering scaffold> under its chemical and biological environment. For a degradable <polymer>, <chain scission> can change molecular size and mechanical behavior before a large amount of solid has disappeared. <Polymer erosion>, meaning loss of material from the scaffold, is therefore related to degradation but is not the same measurement.
A simple chain-counting example shows why. Suppose a specimen initially contains 10,000 identical repeat units arranged in 100 chains. Its mean chain length is 100 units. Cutting each chain once produces 200 chains and a mean of 50 units, while all 10,000 repeat units can still remain in the specimen. Chemical breakdown has occurred without mass leaving. The example neglects the small mass change from newly formed end groups; it is a bookkeeping model, not a measured degradation law.
Mechanical support and tissue formation must evolve together. As the original material weakens, <cells> can deposit <extracellular matrix>, but this does not imply that their mechanical contributions add as two independent springs. Geometry, bonding and local material changes affect the load paths. A scaffold that loses support before a functional matrix forms and one that retains obstructive remnants too long present different engineering problems.
The primary follow-up study of engineered bovine arteries examined culture time and scaffold type. It reported polymer remnants after eight weeks and a different smooth-muscle cell phenotype near those remnants.<Morphologic and mechanical characteristics of engineered bovine arteries by Laura E. Niklason and others>[Printed p. 628, abstract and introduction]{ref} These observations motivate measuring local biological state alongside bulk mechanical performance; the association alone does not establish that every residual polymer fragment has the same effect.
A useful laboratory comparison records retained dry mass, molecular-size change and a specified mechanical response at several times. An acellular incubation under matched medium conditions can help separate material changes from changes associated with the <cells>. Temperature, medium exchange, geometry and the analysis method should be stated, because a single percentage of mass remaining does not fully characterize <scaffold degradation>.
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