Glass substrates modified with organosilanes for DNA immobilization
ALAIN CARRÉ,* WILLIAM BIRCH** and VALÉRIE LACARRIÈRE Corning SAS, Corning European Technology Center, 7 bis, Avenue de Valvins, 77210 Avon, France
Abstract-One technology to produce DNA microarrays involves printing of DNA probes (known DNA sequences) onto a functionalized glass substrate as micro-spots and exposing them to a solution of fluorescently labeled samples of DNA targets (unknown DNA sequences). The functionalization of glass consists of chemically bonding organosilanes to the glass surface. In this paper, two functionalizations are considered. The glass is functionalized with 3-aminopropyltriethoxysilane (APS) or 3-glycidoxypropyltrimethoxysilane (GPS). Silanization with a diaminosilane, N-2-aminoethyl-3-aminopropyltrimethoxysilane (AEAPS), is also considered for comparison. The surface reactivities of APS-, AEAPS-and GPS-treated glass substrates are tested with different methods. One method consists of staining amine functions with gold colloidal particles. This test is applied directly to APS-and AEAPS-treated glass. For probing GPS substrate, epoxide functions are derivatized with a diamine. Wetting performed with water at various pH values is also a simple way to probe surface charge behavior of solid surfaces and to determine their point of zero charge (pzc). The surface of APS and AEAPS substrates is positively or negatively charged, depending on the pH, whereas the GPS substrate is neutral. Glass functionalized with the diaminosilane has a higher pzc than glass functionalized with APS. DNA retention on APS glass at various pH values can be correlated to the surface charge behavior of the solid substrate.