Artificial Scaffolds and Mesenchymal Stem Cells for Hard Tissues - Tissue Engineering: Cell-Surface Interactions for Tissue Culture - page 169

differentiation. Results demonstrated that cells filled the pores of the PHMGCL
scaffold within one week, displayed increased metabolic activity, and supported
osteogenic differentiation [ 123 ].
4 Scaffold-Cell Interaction
4.1 Surface Modification Methods
From a chemical point of view, surfaces characteristics include hydrophilicity
versus hydrophobicity, polar versus non-polar functionalities, and neutral versus
charged surfaces, all defined by nature and amount of functional chemical groups.
Depending on electron negativity strength of the atoms, non-polar or polar
structures can be created, and hydrophilicity can be changed in a controlled
manner that in turn significantly influences cell adhesion processes. Tailor-made
surfaces can be designed via chemical modification, including physical, mechan-
ical, and chemical adhesion (chemisorption). A stronger connection is realized via
chemical grafting resulting in covalent bonds. In Table 1 bond energies and cor-
responding adhesion forces for different chemical bonds are summarized.
According to Dupré, the adhesion power of any substance on a surface depends
on the surface energies of both substance to be adhered to and substrate, and their
interface energy [ 124 ]. A comprehensive review entitled Biomolecular engineer-
ing at interfaces including discussion of the most relevant aspects influencing cell
adhesion on scaffold surfaces and corresponding analytical methods is given by He
and colleagues [ 125 ]. A detailed analysis of physical and biochemical effects for a
scaffold-based approach to directing SC neural and cardiovascular differentiation
is given by Chew and Low [ 126 ].
4.1.1 Biomimetic Surfaces and Controlled Drug Release
Surface modification in biomedicine, in particular tissue engineering, is mainly
realized via creation of a so-called biomimetic surface. Engineering cell and tissue
behavior at device surfaces is focused on modifying the material surface to interact
selectively with a specific cell type through biomolecular recognition processes.
The cell surface has a variety of receptors that bind with other cells or specific
proteins, which compose the environment surrounding the cells known as the
ECM. A promising approach is the biomimetic modification of the material in
which peptides containing the adhesion domains of the ECM proteins are attached
to the base material. The central hypothesis of biomimetic surface engineering is
that peptides which mimic part of the ECM affect cell attachment to the material,
and surfaces modified with these active peptides can induce tissue formation con-
forming to the cell type seeded on the material. Therefore extensive research over