FUNCTIONALIZED GOLD SURFACES WITH
HYPERBRANCHED POLYGLYCEROLS. STUDIES OF APPLICATION.
1 IMBIV-CONICET. Facultad de Ciencias Químicas. Universidad Nacional de Córdoba. Córdoba.
2 Institut für Chemie und Biochemie. Freie Universität Berlin.
julieta@fcq.unc.edu.ar
The less structurally perfect, hyperbranched polymers, synthesized via one-step reactions have been considered as a possible alternative to dendrimers, since structural perfection is not a strict prerequisite for most applications (1). In particular, hyperbranched polyglycerols (hPG) are available on a large scale, and have relatively low polydispersities (2). Nanostructures arising from the combination of hPG with different kind of surfaces have been used for many applications such as catalysis (3), dye solar cell construction (4), or protein resistant surfaces development (5).
Herein, we present functionalized gold surfaces using self-assembled hPG. The first synthetic part in our approach consists of a controlled introduction of amino and disulfide groups on hPG, in order to obtain structures capable to attach on gold surfaces by a self-assembling process (Fig. 1). 5kDa-hPG with ca. one disulfide group and different percentages (0, 6.5, 9, and 14 %) of amino groups per hyperbranched molecule were synthesized. Secondly, the attachment of modified-hPG to gold surfaces was achieved following the normal overnight dipping procedure of a gold slide in
Fig. 1. Derivatization of hPG. Reagents and conditions: i) MsCl, dry pyridine. 0°C- r.t., 18 h; ii) NaN3, dry DMF, 60°C, 72 h; iii) PPh3, THF/water, r.t., 10 days; iv) DCC, DMAP, DMF, r.t., 18 h.
The contact angle studies confirm that modified surfaces are highly hydrophilic in all cases, as it should be expected. Besides, the FT-IRRAS measurements show the characteristic absorption signals of the PG moiety and indicated that both amino and disulfide groups probably participate in the adsorption process of modified hPG onto gold surfaces. Moreover, two confocal fluorescence measurements were conducted in two cases with the purpose of evaluating the availability and the accessibility of the amino groups on the surface: one of them involved the specific binding of a short DNA segment whereas the other one consisted on the unspecific adsorption of streptavidin, both molecules were labeled with a fluorescent dye. In both cases, experiments show that the amino groups on the surface still remain available and accessible for the attachment of big biomolecules after the modification. These results are encouraging for the construction of specifically functionalized gold surfaces useful for biosensor platform development.
Fig. 2. Protein adsorption of modified surfaces referred to a HDT surface. Fib: fibrinogen, Pep: pepsin, BSA: albumin,
These preliminary results point out a novel synthetic route to create hybrid materials using hyperbranched structures promising for biosensors platforms and protein resistant surfaces development.
REFERENCES
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[5] Siegers et al. Chem. Eur. J. 10, (2004) 2831-2838.