Carbon-on-Metal Films for Surface Plasmon Resonance Detection of DNA Arrays

Abstract

Surface plasmon resonance (SPR) measurements provide a highly sensitive means for detecting biomolecular interactions in a label-free manner. Numerous studies of biomolecular interactions have been performed with fixed-angle SPR imaging (SPRi) on surfaces patterned with a variety of biomolecules such as DNA, RNA, proteins, and peptides. 1 Arrays increase the information obtainable in a single experiment as multiple reactions can be monitored in parallel.A current and significant limitation of SPR is that the substrate must be a metal thin film. A number of metal thin films are capable of supporting surface plasmons in the near-infrared and visible regions of the electromagnetic spectrum. 2,3 Gold surfaces have been the substrate of choice for SPR measurements for two reasons: gold is relatively stable in the aqueous environments needed for monitoring biomolecular interactions and a versatile chemistry based on the attachment of sulfur-containing ligands to the gold surface has been developed and wellcharacterized. The readily formed gold-sulfur bond enables the direct attachment of ligands to the gold surface 4 as well as attachment via an intermediate self-assembled monolayer (SAM). 5-7 This gold-thiol chemistry has made possible the routine analysis of aqueous binding processes to immobilized molecules at near-neutral pH values and moderate temperatures. The susceptibility of the gold-sulfur bond to oxidation and photodecomposition has prevented SPR sensing from finding utility in areas such as on-surface combinatorial chemistry (due to the harsh chemical conditions employed) and photolithography (due to the adverse effects of ultraviolet radiation on the gold-sulfur bond). 8Here we describe the development of a lamellar structure in which a thin layer of amorphous carbon is deposited onto a surface plasmon-active gold thin film (Figure 1a). Carbon-based surfaces are readily modified with biomolecules of interest using a well-developed and robust chemistry, based upon the attachment of alkene-containing molecules to the substrate through the UV light-mediated formation of carbon-carbon bonds. 9 Recently, a similar lamellar structure utilizing a thin silicate overlayer was used to fabricate and monitor supported bilayer membranes with SPR. 10 E-mail: smith@chem.wisc.edu. Arrays prepared on functionalized carbon-based substrates such as diamond thin films, 11,12 glassy carbon, 12 and amorphous carbon thin films 13 have superior stability to analogous arrays prepared on functionalized glass, silicon, and gold substrates. Amorphous carbon is of particular interest as it can be deposited at room temperature, allowing it to be integrated with other materials 14 such as quartz crystal microbalances, 13 electrodes, 15 and metal thin films without perturbing their structure. The utility of a multilayered substrate containing a metal thin film and an amorphous carbon overlayer is shown here by their use for in situ synthesis of oligonucleotide arrays, which are then employed in the analysis of biomolecule binding proces...

Reflectivity optimization of the SPR graphene sensor

“…When compared with gold, the plasmon coupling in the silver has a sharper angular resonance peak [12], but it presents a drawback that it can be easily oxidized and the poor chemical stability thus affecting the performance of SPR-sensors [11,12]. Many of methods were designed in an attempt to overcome this problem, for example the use of bimetallic silver-gold layers [13,14], a thin oxide fi lms TiO 2 or SnO 2 [15][16][17], In addition to thin fi lms of carbon such as the amorphous carbon [18], amorphous carbonated silicon (a-Si 0.63 C 0.37 ) [19][20][21] and the newer one is, graphene [13].…”

Label-free analysis of biomolecular interactions using SPR imaging

“…To date, such arrays have not been commercialized for label-free analysis using SPRi due largely to the fact that the methods required for array fabrication undermine the adhesion of the gold layer to the glass. However, the advent of carboncoated gold SPR chips has now created the means to fabricate arrays directly on chips for label-free analysis, as discussed in section SPRi applications based on carbon-coated gold, below (30). …”

“…Figure 5 illustrates how this can be achieved by UV-irradiating an alkene, such as 9-decene-1-ol, on the aC surface; the alkene end of the molecule forms C-C bonds with the aC surface, while the hydroxyl groups remain available for further chemistry. The functionalized aC substrates withstood MAS array fabrication, and the resulting DNA arrays enabled real-time monitoring of the binding of specific proteins to the DNA arrays using SPRi (30). …”

Sensitive and selective DNA detection based on the combination of hairpin-type probe with endonuclease/GNP signal amplification using quartz-crystal-microbalance transduction

“…To avoid significant difficulties encountered with conventional protocols, DNA sequence detection and single-nucleotide polymorphism identification [6] have been extensively exploited in application fields as well as in basic biological sciences. A variety of measurement techniques, including electrochemical (such as amperometric [7][8][9], potentiometric [10,11], chronocoulometric [12,13] and impedimetric [14][15][16][17] measurements), optical (e.g., fluorescence [18][19][20][21], surface-enhanced Raman scattering spectroscopy [22], chemiluminescent measurement [23], dual polarization interferometry [24], colorimetric detection [25] and surface plasmon resonance [26,27]), acoustic [28,29] and piezoelectric [30,31] transductions, have been employed to develop DNA biosensors. Among them, the piezoelectric sensing strategy based on quartz crystal microbalance (QCM) have proved to be a promising tool for the detection of DNA sequence due to its simplicity, cost effectiveness, easy operation and high mass sensitivity [32,33].…”