Biomedical Engineering Reference
In-Depth Information
20
Cell Adhesion and Spreading on an
Intrinsically Anti-Adhesive PEG Biomaterial
Marga C. Lensen
1,2
, Vera A. Schulte
1
and Mar Diez
1
1
DWI e.V. and Institute of Technical and Macromolecular Chemistry, RWTH Aachen
2
Technische Universität Berlin, Institut für Chemie, Nanostrukturierte Biomaterialien
Germany
1. Introduction
This Chapter deals with bulk hydrogels consisting of a widely used biomaterial:
poly(ethylene) glycol (PEG). PEG is renown for its bio-inertness; it is very effective in
suppressing non-specific protein adsorption (NSPA) and thereby preventing cell adhesion.
However, we have observed unexpected adhesion of fibroblast cells to the surface of bulk
PEG hydrogels when the surface was decorated with micrometer-sized, topographic
patterns. This Chapter describes the aim of our investigations to unravel the biophysical,
biochemical and biomechanical reasons why these cells do adhere to the intrinsically anti-
adhesive PEG material when it is topographically patterned.
1.1 Application of hydrogels in biomaterial science
Amongst the different classes of materials which find use in the field of medicine and
biology, hydrophilic polymers have demonstrated great potential. Networks formed from
hydrophilic polymer often exhibit a high affinity for water, yet they do not dissolve due to
their chemically or physically crosslinked network. Water can penetrate in between the
chains of the polymer network, leading to swelling and the formation of a hydrogel (Langer
& Peppas, 2003; Peppas et al., 2000; Wichterle & Lim, 1960). Generally such polymer
networks can be formed via chemical bonds, ionic interactions, hydrogen bonds,
hydrophobic interactions, or physical bonds (Hoffman, 2002; Peppas, 1986). Hydrogels have
found numerous applications in drug delivery as well as in tissue engineering where they
are used as scaffolds for the cultivation of cells to enable the formation of new tissues (Jen et
al. 1996; Krsko & Libera, 2005; Langer & Tirrell, 2004; Peppas et al., 2006). Hydrogels are
especially attractive for this purpose as they meet numerous characteristics of the
architecture and mechanics of most soft tissues and many are considered biocompatible
(Jhon & Andrade, 1973; Saha et al., 2007). Furthermore, concerning the intended purpose of
cell encapsulation and delivery, hydrogels support sufficient transport of oxygen, nutrients
and wastes (Fedorovich et al., 2007; Lee & Mooney, 2001; Nguyen & West, 2002).
In general, hydrogel matrices can be prepared from a variety of naturally derived proteins
and polysaccharides, as well as from synthetic polymers (Peppas et al., 2006). Depending on
their origin and composition, natural polymers have specific utilities and properties.
Hydrogels from natural sources have for example been fabricated from collagen, hyaluronic
acid (HA), fibrin, alginate and agarose (Hoffman, 2002). Collagen, HA and fibrin are
