Modification of crystalline silicon and diamond surfaces for the attachment of DNA

Hydrogen-terminated Si(111) surfaces are first modified by attachment of oligodeoxynucleotides, and characterized with respect to DNA surface density, chemical stability, and DNA hybridization binding specificity. Surface functionalization employs the reaction of ω-unsaturated alkyl esters with the Si(111) surface using UV irradiation. Cleavage of the ester using potassium tert-butoxide yields a carboxyl-modified surface, which serves as a substrate for the attachment of DNA by means of an electrostatically adsorbed layer of polylysine and attachment of thiol modified DNA using a heterobifunctional cross-linker. The resultant DNA-modified surfaces are shown to exhibit excellent specificity and chemical stability under the conditions of DNA hybridization.; The second approach is a more direct method of attaching oligonucleotides to silicon. UV light mediates the reaction of t-butyloxycarbonyl (t-BOC) protected ω-unsaturated aminoalkane (10-aminodec-1-ene) with hydrogenterminated silicon (001). Removal of the t-BOC protecting group yields an aminodecane-modified silicon surface. The resultant amino groups can be coupled to thiol-modified oligodeoxyribonucleotides using a heterobifunctional crosslinker, permitting the preparation of DNA arrays. Two methods for controlling the surface density of oligodeoxyribonucleotides were explored: in the first, binary mixtures of 10-aminodec-1 ene and dodecene were utilized in the initial UV-mediated coupling reaction; a linear relationship was found between the mole fraction of aminodecene and the density of DNA hybridization sites. In the second, only a portion of the t-BOC protecting groups was removed from the surface by limiting the time allowed for the deprotection reaction.; The final surface explored uses a UV-mediated reaction of alkenes to hydrogenterminated diamond. Polycrystalline diamond thin films are hydrogen terminated using a hydrogen plasma and are subjected to UV light in the presence of 1-alkenes. A perfluoronated alkene is shown to attach only with the use of UV light. ω-Unsaturated alkyl esters are attached and subsequently hydrolyzed to the carboxylic acid using potassium tert-butoxide. Additionally, amines containing the trifluoroacetyl (TFA) protection group are similarly attached to the diamond and subsequently deprotected to the primary amine.