Biomaterials for MEMS

Polymer-Based Biocompatible Surface Coatings 193

8.6 HYPERBRANCHED POLYGLY CIDOL BASED NON-FOULING

SURFACES

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.

118−120

Siegers and Haag prepared highly protein-resistant, self-assembled monolay-

ers of dendritic disulfide-functionalized polyglycerols (PGs) on gold.

118

Dendritic

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).

120

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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