Artificial Scaffolds and Mesenchymal Stem Cells for Hard Tissues - Tissue Engineering: Cell-Surface Interactions for Tissue Culture - page 174

by a more pronounced gene expression of the bone markers alkaline phosphatase,
osteocalcin, bone sialoprotein I, and bone sialoprotein II. In addition, dynamic
culture resulted in higher amounts of deoxyribonucleic acid (DNA) and
calcium. Embedding synergistically enhanced the calcium deposition of hMSC
[ 155 ]. Further studies recently reported include the design of novel 2D and 3D
biointerfaces using self-organization to control cell behavior [ 156 ], concave pit-
containing scaffold surfaces that improve SC-derived osteoblast performance and
lead to significant bone tissue formation [ 157 ], polymer thin films for biomedical
applications designed via nanotechnologies [ 158 ], and direct patterning of protein-
and cell-resistant polymeric monolayers and microstructures [ 159 ].
LbL technique using polyelectrolytes. Picart and co-workers studied new
methods for positioning and anchoring of biomolecules onto scaffold surfaces
using multiple functionalities of polyelectrolyte multilayer films [ 153 ]. The LbL
technique using polyelectrolytes was first described by Decher [ 160 ]. A variety of
depositing methods have since been developed for LbL formation including dip
coating, spin coating, and spraying. Entcheva and colleagues developed a new
dewetting method, which appears to be efficient, economical, and fast and could be
used to create unique adsorption topographies, including fractal networks and
aligned fibers [ 161 ]. For future use and industrial applications of LbL films, the
total time required for film preparation and the anchorage of the layer to the
underlying substrate are probably important constraints. Rapid methods such as
spraying are being further developed. In addition, anchorage to the underlying
substrate was improved, in particular for hydrophobic surfaces like poly(tetra-
fluoroethylene) and poly(ethylene), which often require priming methods.
Assembling polyelectrolyte multilayers and their effects on self-assembly of
particles in a so-called bottom-up approach is reported for polymers, particles,
nanoparticles, and carbon nanotubes [ 162 ]. In another approach, polyelectrolyte
multilayer films have been designed for vascular tissue engineering applications.
Human mesenchymal SC differentiation into endothelial-like cells could be

observed on surfaces coated with polyelectrolyte multilayer films [ 163 ].
LB technique. Beside the LbL method, mainly limited to polyelectrolytes, the
LB technique can be used to design mono- and multilayers as coating materials, as
illustrated in Fig. 4 .
LB monolayers can be modified in a very controlled manner to obtain tailor-
made surfaces. The surface roughness is limited to a nanometer scale, depending
on the chemical structure of the monomers and polymers used for film formation.
Appropriate polymers for mono- and multilayer formation via LB thin film
technology are rigid rod-like polymers. Rigidity can be caused by different
structural reasons: rigid monomer units (e.g., aromatic rings in poly-
p-phenylenes), supramolecular structures (e.g., helical structures of polypeptides,
DNA, polyglutamates, cellulose derivatives) or specific packing resulting in rod-
like systems, e.g., phthalocyaninato poly(siloxanes). In Fig. 4 b the regeneration of
cellulose ethers is illustrated. This reaction can be performed after film transfor-
mation directly on the scaffold (c). Part D in Fig. 4 illustrates the so-called reaction
zones for surface modification reactions. Thus, cell-attracting functionalities can