Engineering Graded Tissue Interfaces - Structural Interfaces and Attachments in Biology - page 294

Fig. 14.1 Schematic diagrams for the successive binding of heparin and growth factor onto the
fibril surface of a PCL/F127 cylindrical scaffold and the formation of 3D growth factor gradient on
the scaffold (reproduced, with permission, from [ 43 ])
of retrovirus encoding the osteogenic transcription factor Runx2/Cbfa1. Gradients
of immobilized retrovirus, achieved via deposition of controlled poly( L -lysine)
densities, resulted in spatial patterns of transcription factor expression, osteoblas-
tic differentiation, and mineralized matrix deposition. They found that the graded
distribution of mineral deposition and mechanical properties were maintained
when implanted in vivo in an ectopic site.
Even though many growth factor cocktails have been investigated, due to the
complexity of the biological environment at the interface, an appropriate composi-
tion and pattern have yet to be determined. Great care must be given in the design of
appropriate carriers and to tailor the retention time, biological activity, and release
kinetics of growth factors at specific sites within two engineered tissues and their
interface.