Oligonucleotide-templated nanoparticle assembly Fiona McKenzie

Locked Nucleic Acid more stable duplex more selective for complementary target can target double stranded DNA: triplex formation Methods of detection: UV-visible spectroscopy SERRS: ideal for multiplexed analysis Summary of previous work Small, 2007, 3, 1866–1868, Chem. Commun., 2008, 2367–2369

514.5 nm laser excitation ROX ITC Target DNA SH Addition of isothiocyanate dye after oligo functionalisation Aggregation of nanoparticles upon target DNA addition: 1.allows electromagnetic coupling resulting in higher SERRS signals 2. nanoparticle plasmons in resonance with laser excitation and dye absorbance Using SERRS to monitor DNA hybridisation Chem Commun. 2009, 5757–5759

+ target DNA Addition of target results in aggregation: increased SERRS output Using SERRS to monitor DNA hybridisation Chem Commun. 2009, 5757–5759

Different Dye Labels Versatility of labelling method illustrated by use of different dye labels with different means of surface attachment- useful for multiplexing Chem Commun. 2009, 5757–5759

5’ 3’ Triplex SERRS 25 °C60 °C25 °C 60 °C Hybridisation of probes to yield triplex structure also gives rise to SERRS Reversible assembly manuscript in preparation

5’ 3’ 5’ 3’ 5’ 3’ 5’ 3’ SERRS intensity dependence on inter-particle distance investigated Greater the distance, lower intensity anomaly in trend 41 °C 62 °C 65 °C Towards a “SERRS ruler” manuscript in preparation

Effect of melting temperature on SERRS intensity 39 °C SERRS analysis 54 °C 47 °C 39 °C 44 °C 51 °C NaCl used to alter melting temperature Formamide used to alter melting temperature indicates thermodynamic stability of DNA nanoparticle assembly has an effect on SERRS intensity as well as interparticle distance

Mixed Metal SERRS Gold nanoparticles often used in preference due to well-established surface chemistry and improved stability Silver nanoparticles give rise to much greater surface enhancement factors silver nanoparticle probes gold nanoparticle probes Nanoscale, 2009, in press

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