Silicon surface biofunctionalization with dopaminergic tetrahydroisoquinoline derivatives

• Published in: Applied surface science 2016-01, Vol.360, p.419-428
• Main Authors: Lucena-Serrano, A., Lucena-Serrano, C., Contreras-Cáceres, R., Díaz, A., Valpuesta, M., Cai, C., López-Romero, J.M.
• Format: Article
• Language: English
• Subjects: Alkaloids; Dopaminergic activity; Hydrosilylation; Phenylisoquinoline; Photografting; Silicon-wafer
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2015.10.195

•Two dopaminergic tetrahydroisoquinolines (THI) were synthesized.•Vinyl-terminated THI incorporated onto the HSi(111) substrates via a hydrosilylation.•The highest yield in coverage was obtained in DMSO, at 4h of irradiation and 0.1mbar of vacuum.•Alkynyl-terminated Si surface was produced for incorporation of azide-THI by click reaction.•Best yields on grafted molecule were obtained by click reaction in absence of ascorbic acid. In this work we grafted vinyl- and azido-terminated tetrahydroisoquinolines (compounds 1 and 2, respectively) onto HSi(111) silicon wafers obtaining highly stable modified surfaces. A double bond was incorporated into the tetrahydroisoquinoline structure of 1 to be immobilized by a light induced hydrosilylation reaction on hydrogen-terminated Si(111). The best results were obtained employing a polar solvent (DMSO), rather than a non-polar solvent (toluene). The azide derivative 2 was grafted onto alkenyl-terminated silicon substrates with copper-catalyzed azide-alkyne cycloaddition (CuAAC). Atomic force microscopy (AFM), contact angle goniometry (CA) and X-ray photoemission spectroscopy (XPS) were used to demonstrate the incorporation of 1 and 2 into the surfaces, study the morphology of the modified surfaces and to calculate the yield of grafting and surface coverage. CA measurements showed the increase in the surface hydrophobicity when 1 or 2 were incorporated into the surface. Moreover, compounds 1 and 2 were prepared starting from 1-(p-nitrophenyl)tetrahydroisoquinoline 3 under smooth conditions and in good yields. The structures of 1 and 2 were designed with a reduced A-ring, two substituents at positions C-6 and C-7, an N-methyl group and a phenyl moiety at C-1 in order to provide a high affinity against dopaminergic receptors. Moreover, O-demethylation of 1 was carried out once it was adsorbed onto the surface by treatment with BBr3. The method presented constitutes a simple, easily reproducible and high yielding approach for grafting complex organic biomolecules with dopaminergic properties onto silicon surfaces.