Surface Modification for Protein Resistance Using a Biomimetic Approach
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Surface Modification for Protein Resistance Using a Biomimetic Approach Jeffrey L. Dalsin and Phillip B. Messersmith Biomedical Engineering Department and Institute for Bioengineering and Nanoscience in Advanced Medicine (IBNAM), Northwestern University, Evanston, IL 60208
ABSTRACT In recent years the immobilization of poly(ethylene glycol) (PEG) on surfaces has proved to be one of the most attractive methods to prevent biological fouling of surfaces. We have developed a paradoxical biomimetic PEGylation strategy that exploits the adhesive characteristics of proteins secreted by marine mussels—one of nature’s most notorious foulers. Linear PEGs were coupled to peptides containing 3,4-dihydroxyphenylalanine (DOPA), an unusual amino acid which is found in high concentration in these so-called mussel adhesive proteins. Using surface plasmon resonance, we have demonstrated enhanced resistance to protein adhesion on gold substrates modified with the DOPA-containing PEGs.
INTRODUCTION For many emerging medical and non-medical applications, strict control of the fluid-solid interface is of essential importance, and the non-specific bioadhesion of proteins and cells on surfaces continues to impede many aspects of biomaterials research. Although a variety of polymeric surface modifications have been investigated, the immobilization of PEG on surfaces appears to be one of the most promising routes to create surfaces that are resistant to cell and protein adhesion.1,2 The current arsenal of surface modification strategies, however, often requires the presence of specific surface functional groups and thus, have a limited capacity to be used for modification of a variety of materials. Moreover, existing approaches may result in PEG coatings that are susceptible to hydrolysis and/or thermal degradation.1 Marine and freshwater mussels are known to secrete unique proteins to secure themselves to many types of surfaces on which they reside in the ocean’s turbulent intertidal zone. These mussel adhesive proteins (MAPs) are able to form tenacious bonds with rocks, wooden structures, and metal and fiberglass ship hulls.3 Perhaps the best characterized protein is Mytilus edulis foot protein 1 (Mefp-1), in which the consensus peptide Ala-Lys-Pro-Ser-Tyr-DHP-HypThr-DOPA-Lys (DHP: dihydroxyproline) is tandemly repeated some 75-85 times.4,5 It is widely believed that the unusual catecholic amino acid DOPA, a post-translationally modified tyrosine, is in large measure responsible for the adhesive characteristics of the protein.6 Although the exact nature of the DOPA-substrate interaction is not fully understood, it is clear that phenols and catechols have a very high affinity to metals in the aqueous environment. Several investigators have examined the ability of various phenols to chelate metal ions7 as well as adhere to metallic particles and metal oxide surfaces.8,9 For metals with insignificant surface oxide such as platinum, catechols form essentially irreversible organometallic complexes.10 There is also some spectroscopic e
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