Periodic Reporting for period 2 - SMART-DNA (Single Molecule Analytical Raman Tools based on DNA nanostructures)
Reporting period: 2019-10-01 to 2021-03-31
Apart from Raman enhancement the excitation of the localized surface plasmon resonance of the metallic nanostructures results in other plasmonic effects such as heating and possibly the transfer of hot electrons. This can lead to diffusion, conformational changes or even dissociation of the target molecules. These issues do not only concern SM-SERS, but also make quantitative SERS and the SERS analysis of complex (bio)molecules very challenging. By the improved structural control achieved by SMART-DNA, nanoscale heating and hot electron transfer and their effect on SERS spectra will be studied on an ensemble and a SM level. Finally, reactions induced by plasmonically generated electrons in DNA and DNA modified with electrophilic molecules will be studied by SERS with the aim to develop novel strategies to improve cancer radiation therapies such as the photothermal therapy.
Objectives of SMART-DNA:
I. Provide control over multiple structural parameters using bionanotechnology. SMART-DNA will create and apply advanced DNA origami based SERS substrates with aptamer binding sites. The SERS substrates should have the following properties: i) Tunable SERS enhancement, (ii) Control of analyte number and orientation in the SERS hot spot using aptamers, (iii) Possibility of analyte diffusion into hot spots, (iv) SERS measurements should be possible with SERS substrates dispersed in solution and immobilized on surfaces.
II. Establish reliable, continuous SM-SERS detection for a broad range of molecules. Field enhancement and structural control will be further optimized to establish SM-SERS measurements for small and complex molecules and for resonant and non-resonant molecules.
III. Explore nanoscale interactions between NPs, molecules and excitation light. Especially changes of temperature, geometry and molecular integrity upon LSPR excitation will be explored for small and complex molecular systems.
IV. Explore electron-transfer induced reactions in DNA and modified DNA. A specific focus will be put on hot-electron induced reactions in DNA derivatives, since these are rather unexplored in the context of SERS but have great potential to become relevant for cancer radiation therapy.
A DNA origami nanofork has been designed and optimized to create plasmonic Dna Origami Nanofork Antennas (DONAs) for single-molecule SERS.
Small molecules have been specifically bound into the SERS hot spots to detect them at the single-molecule level and to study ther properties and reactions.
The proteins Cyt C and horseradish peroxidase (HRP) have been bound by different coupling strategies to the DNA origami fork and detected by single-molecule SERS. The placements of the proteins in the SERS hot spots has been analyzed in detail.
The kinetics of hot electron induced reactions on gold nanoparticles have been studied using a range of molecules and a detailed kinetic model is currently developed. Furthermore, we have studied electron transfer from nanoparticles to modified DNA.