Polymer-Based Biocompatible Surface Coatings 193
Hyperbranched polyglycerols (HPGs) which presented a high density of glycol
groups due to its highly branched architecture is another good candidate for
making non-fouling surfaces.
Siegers and Haag prepared highly protein-resistant, self-assembled monolay-
ers of dendritic disulfide-functionalized polyglycerols (PGs) on gold.
PGs combined the characteristic structural features of highly protein-resistant
surfaces: a highly flexible aliphatic polyether, hydrophilic surface groups and a
highly branched architecture. While PG monolayers were as protein resistant as
PEG SAMs, they were significantly more active than dextran-coated surfaces. Due
to the higher thermal and oxidative stability of the bulk PG as compared to PEG
and the easy accessibility of these materials, it is a promising candidate for the
development of non-fouling surface coatings.
Recently, our group synthesized monothiol-terminated hyperbranched polyg-
lycerols (HPGs) by ring-opening polymerization of glycidol from partially depro-
tonated 2,2’-dihydroxyethane disulfide as the initiator and subsequent reduction
of the disulfide group (Fig. 8.21).
Monothiol-functionalized HPGs readily ad-
sorbed to a gold surface and formed highly uniform thin films on the surface.
It was found that the graft density of the HPG layer decreased with an increase
in the molecular weight of the polymer. A comparison of protein adsorption to
HPG coated surfaces and PEG coated surfaces were also presented. Incubation of
a polymer-coated surface (HPG thiols and PEG thiols) with bovine serum albumin
and immunoglobulin showed that the high molecular weight hyperbranched
polyglycerol was more resistant to protein adsorption than linear PEG of similar
Figure 8.21. Representation of the structures of polymeric films on a gold surface: (a)
linear mPEG monothiol and (b) HPG monothiol. Images adapted from Ref. 120.
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