We present a proof-of-concept of the application of gold nanotriangles in sequence specific DNA detection, using localized surface plasmon resonance (LSPR) spectroscopy and dark-field optical microscopy. The sensing platform comprises gold nanotriangles immobilized on a glass chip and oligonucleotides as probes. Probe formation and testing complementary and non-complementary targets followed common chip technology protocols. Gold nanotriangles showed a remarkable sensitivity of 468 nm per RIU and allowed detection of 20-mer targets. When the target sequence was part of a 50-mer synthetic DNA oligonucleotide, LSPR shifts as high as 35 nm were observed. Conversely, when the target was present in PCR products of ca. 350 bp, obtained from clinical samples, LSPR shifts larger than 20 nm were observed. Moreover, LSPR shifts were less than ±1 nm for the respective non-complementary targets. These results with gold nanotriangles as sensors are a notable improvement to the LSPR shifts of less than 5 nm usually obtained for spherical gold nanoparticles of comparable sizes. Optimal conditions for the detection of synthetic and PCR product targets using gold nanotriangles and oligonucleotide probes were achieved with low percentages of intercalating thioalkanes; target hybridization at room temperature, 3 hours of incubation, and 2× SSC buffer stringency conditions.

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Plasmonic nanoparticles, e.g. nanoscale particles consisting of noble metals, show high potential as transducer elements in novel optical sensors. Their optical properties are based on collective and coherent oscillation of the conduction electrons by irradiating electromagnetic waves. The resulting resonance band (localized surface plasmon resonance [LSPR]) is adjustable in the UV‐ to near‐infrared spectral range and can be defined by the chemical synthesis. The synthesis conditions can determine dimension, material and particle shape, and these parameters represent the main factors for the position of the LSPR and the bulk sensitivity. Therefore, a reproducible synthesis of nanoparticles with defined LSPR is of importance. The sensing principle is based on the strong influence of the surrounding medium's refractive index. Especially, anisotropically shaped particles are especially sensitive to small changes in the medium; therefore, their defined synthesis is in the focus of current developments. In this review, we give an overview of the different synthesis techniques for nanoparticles, including miniaturized fluid devices. For sensoric applications, the conjugation of nanoparticles with biomolecules represents a key step; thus, typical functionalization approaches are considered. In the following sections, different LSPR sensing strategies are introduced, and possible applications, especially in DNA analytics, are demonstrated.