Abstract
An oligodeoxynucleotide hairpin containing a photolabile 2-nitrobenzyl group in the loop and terminated with a thiol function was prepared. The photocleavage of such a hairpin on gold yields a surface activated with a single stranded oligonucleotide which can be utilised to direct the assembly of nanoparticles conjugated with a complementary strand. Analysis of photocleaved surfaces gives nanoparticle coverage one order of magnitude higher than nonphotocleaved surfaces. This illustrates the ability of photocleavable hairpins to direct the assembly of nanomaterials on conducting materials. The conjugation of the photocleavable hairpin to a gold nanoparticle allows the observation of intermolecular interactions between hairpins linked in different nanoparticles, by comparing the thermal dissociations of a hairpin-nanoparticle conjugates at 260 nm and 520 nm. We have also shown that it is possible to permanently alter the physiochemical properties of DNA-nanoparticles by the introduction of a photocleavable group. Indeed for the first time it has been shown that by exposure to UV light the disassembly of nanoparticle aggregates can be induced.
Highlights
The use of DNA to form macroscopic aggregates was first demonstrated by Mirkin in 1996 [1].This method involved conjugating two non-complementary oligonucleotides to gold nanoparticles and mixing them in the presence of a bridging strand partially complementary to both strands; this bridging element causing aggregation of the nanoparticles as visible by a plasmon shift in the visible region.This technique was further advanced to develop electric [2] and scanometric [3] based DNA sensors, such sensors have been shown to be orders of magnitude more sensitive than standard fluorophore based assays.At the same time Alivisatos developed a method to assemble oligonucleotides into rationally designed dimers and trimers [4]
Hairpin oligonucleotide sequence A was prepared. This oligonucleotide has a photolabile linker in apex of the loop and a dithiol group at the 3′-end
A commercially available phosphoramidite was used for the introduction of the photolabile 2-nitrobenzyl group at the half of the sequence (Scheme 2c)
Summary
The use of DNA to form macroscopic aggregates was first demonstrated by Mirkin in 1996 [1].This method involved conjugating two non-complementary oligonucleotides to gold nanoparticles and mixing them in the presence of a bridging strand partially complementary to both strands; this bridging element causing aggregation of the nanoparticles as visible by a plasmon shift in the visible region.This technique was further advanced to develop electric [2] and scanometric [3] based DNA sensors, such sensors have been shown to be orders of magnitude more sensitive than standard fluorophore based assays.At the same time Alivisatos developed a method to assemble oligonucleotides into rationally designed dimers and trimers [4]. The use of DNA to form macroscopic aggregates was first demonstrated by Mirkin in 1996 [1] This method involved conjugating two non-complementary oligonucleotides to gold nanoparticles and mixing them in the presence of a bridging strand partially complementary to both strands; this bridging element causing aggregation of the nanoparticles as visible by a plasmon shift in the visible region. This technique was further advanced to develop electric [2] and scanometric [3] based DNA sensors, such sensors have been shown to be orders of magnitude more sensitive than standard fluorophore based assays. The aim of this work is to link these photolabile molecules onto surfaces to obtain functionalized surfaces
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