Covalent functionalization and biomolecular recognition properties of DNA-modified silicon nanowires

Abstract

The direct covalent modification of silicon nanowires with DNA oligonucleotides, and the subsequent hybridization properties of the resulting nanowire–DNA adducts, are described. X-ray photoelectron spectroscopy and fluorescence imaging techniques have been used to characterize the covalent photochemical functionalization of hydrogen-terminated silicon nanowires grown on SiO2 substrates and the subsequent chemistry to form covalent adducts with DNA. XPS measurements show that photochemical reaction of H-terminated Si nanowires with alkenes occurs selectively on the nanowires with no significant reaction with the underlying SiO2 substrate, and that the resulting molecular layers have a packing density identical to that of planar samples. Functionalization with a protected amine followed by deprotection and use of a bifunctional linker yields covalently linked nanowire–DNA adducts. The biomolecular recognition properties of the nanowires were tested via hybridization with fluorescently tagged complementary and non-complementary DNA oligonucleotides, showing good selectivity and reversibility, with no significant non-specific binding to the incorrect sequences or to the underlying SiO2 substrate. Our results demonstrate that the selective nature of the photochemical functionalization chemistry permits silicon nanowires to be grown, functionalized, and characterized before being released from the underlying SiO2 substrate. Compared with solution-phase modification, the ability to perform all chemistry and characterization while still attached to the underlying support makes this a convenient route toward fabrication of well characterized, biologically modified silicon nanowires.

Nanowire-Based Electrochemical Biosensors

“…The use of photochemical hydrosilation to functionalize free standing SiNWs with DNA without an intervening oxide was recently demonstrated [108]. In this procedure hydrogen terminated SiNWs are covalently linked to 10-NBoc-Amino-dec-1-ene through ultraviolet (UV) initiated reaction (Scheme 3a) [109].…”

Quantitative Real-Time Measurements of DNA Hybridization with Alkylated Nonoxidized Silicon Nanowires in Electrolyte Solution

“…[33][34][35][36] Such chemistry has been used for the covalent attachment of DNA to VLS grown SiNWs. 37 DNA may also be immobilized on amineterminated surfaces via electrostatic interactions. In this paper, we explore how the characteristics of SiNW sensors vary as the nature of the inorganic/organic interface is varied.…”

Organic Surface Modification of Silicon Nanowire-Based Sensor Devices

“…The first report on the modification of oxide-free SiNW-based devices is by Heath and coworkers (Bunimovich, 2006). The authors followed an established, multistep protocol (Bunimovich, 2004;Streifer, 2005) that starts with the hydrosilylation of H-terminated SiNWs with tert-butyl allylcarbamate (Figure 7, alkene 7a) irradiated at 254 nm. After deprotection, the researchers obtained a positively charged amine-terminated monolayer on the SiNWs, enabling the adsorption of negatively charged, oligo ss-DNA.…”