Construction of a densely poly(ethylene glycol)-chain-tethered surface and its performance

Abstract

Non-biofouling surfaces constitute one of the most important subjects in sensitively and selectively detecting biomolecular events. Poly(ethylene glycol) (PEG) chains tethered on substrate surfaces are well known to reduce non-biofouling characteristics. Protein adsorption onto a PEG-chain-tethered surface is strongly influenced by the density of the PEG chain and is almost completely suppressed by the successive treatment of longer PEG chains (5 kDa) followed by the treatment of PEG (2 kDa; mixed-PEG-chain-tethered surface) because of a significant increase in PEG chain density. To modify versatile substrate surface, PEG possessing pentaethylenehexamine at one end (N6-PEG) was prepared via a reductive amination reaction of aldehyde-ended PEG with pentaethylenehexamine. Using N6-PEG, antibody/PEG co-immobilization was conducted on a substrate possessing active ester groups. After the antibody was immobilized on the surface, PEG tethered chains were constructed surrounding the immobilized antibody. It is interesting to note that the PEG-chain-tethered functions not only as a non-fouling agent but also improves immune response. The hybrid surface was also applied to oligo DNA immobilization. The oligo DNA/PEG hybrid surface improved hybridization, retaining its non-fouling ability. Densely packed PEG tethered chains surrounding antibodies and/or oligo DNA improved their orientation on the surface. Thus, this material is promising as a high-performance biointerface for versatile applications. Keywords: antibody; biosensing; DNA; end-functionalized poly(ethylene glycol); enzyme-linked immunosorbent assay; hybrid biointerface; soft interface INTRODUCTION Specific biorecognition on substrate surfaces has long been utilized in many applications such as biosensing, 1 immunodiagnostics, 2 enzyme immunoassay, 3 western blotting 4 and protein microarrays. 5 Important factors for the improvement in specific biorecognition on surfaces are the suppression of nonspecific biofouling and the suitable orientation of immobilized biomolecules. The former decreases nonspecific noise and the background level, and the latter increases the specific recognition level. To improve the non-biofouling character of surfaces, numerous efforts have been undertaken. In general, natural polymers such as albumin, casein and dextran have been used for blocking on substrate surfaces. 6 These treatments work well and suppress protein biofouling extensively. If extremely high performance is required, however, these blocking treatments are not enough. In addition, natural products, especially those derived from animals, may have undesired contents such as bacteria and viruses, which may affect the user. 7 Under these circumstances, synthetic polymers have been recently suggested as suitable surface blocking agents. Numerous types of water-soluble polymers, such as poly(acrylamide), poly(vinyl alcohol), poly(vinyl pyrrolidone) and poly(ethylene glycol) (PEG), have been investigated so far. Recently, new types of synthetic polymers such as poly(methoxy ...

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