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Investigative study of nucleic acid-gold nanoparticle interactions using laser-based techniques, electron microscopy, and resistive pulse sensing with a nanopore

Michelle Low , Sam Yu, Ming Yong Han and Xiaodi Su
Australian Journal of Chemistry. 2011. 64(9) 1229-1234

In this study, we employ a range of analytical tools to study the interactions between a mixed base peptide nucleic acid (PNA, 22-mer) probe and gold nanoparticles (AuNP). The binding of charge neutral PNA to citrate capped AuNP (50 nm) causes the particles to change size and/or aggregation/dispersion status in a PNA concentration-dependent manner. Under a UV-vis spectrophotometer, AuNP aggregation can be detected at PNA concentrations as high as 400 nm. Using dynamic light scattering measurement, the changing of particle sizes can be detected at a relatively low PNA concentration of 50 nm. Using a resistive pulse sensor, i.e. nanopore-based sensing platform, a particle-by-particle measurement technique, subtle changes of the AuNP size induced by PNA at very low concentrations of 5 nm can be identified. Transmission electron microscopy measurement confirmed that at very low PNA concentration, a small population of particles form a nano-assembly of NP clusters. Based on the fact that hybridization of PNA probe with target DNA is able to retard particle aggregation, we can quantify specific DNA sequences with a limit of detection ranging from 10 nm to 1 nm, depending on the characterization tools used. With this study, we show that as a complementary technique, the resistive pulse nanopore-based sensing platform provides significant resolution advantages for metal nanoparticle measurement as compared with light-based techniques.

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