Jerome Wenger NanoBioPhotonics

Achieving sub-millisecond temporal resolution to monitor fast molecular dynamics has been a persistent challenge in single-molecule fluorescence spectroscopy. The fluorescence brightness, or the number of photons detected per second and per molecule, is the key parameter that determines the temporal resolution of these techniques. Unfortunately, conventional confocal microscopes fall short in providing the brightness required for sub-millisecond monitoring. In a recent article published in Advanced Optical Materials, we present a method for achieving high temporal resolution in single-molecule fluorescence techniques using optical horn antennas.

Significance:

- We demonstrate the use of plasmonic nanoantennas to achieve a remarkably high level of collection efficiency, reaching over 90% of the total emitted light from a single diffusing molecule.

- With a fluorescence brightness of 2 million photons/s/molecule, we can perform fast FCS measurements and observe single molecules within individual diffusion bursts at microsecond binning time.

- This technological advancement expands the application of plasmonic antennas and zero-mode waveguide nanoapertures towards higher fluorescence count rates and faster temporal resolutions

Freely available on ArXiv 2303.00416

We are pleased to welcome Julia Osmolska to our lab for the next two months as an intern. Julia will be working on a fascinating research project on gold nanoclusters and the use of plasmonics to enhance their photoluminescence.

Julia comes to us from the group of Joanna Olesiak-Banska at the Wroclaw University of Science and Technology, and we are eager to learn from her expertise and experience in the field. With her background, we are confident that she will make valuable contributions to our lab during her time here.

Please join us in welcoming Julia to our lab and stay tuned for updates on her research progress. We can't wait to see the impact that she will make during her time here!

We are thrilled to announce the arrival of our newest PhD student, Malavika Kayyil Veedu, who will be joining us for the next three years. She will be working with us on a cutting-edge research project on plasmonics-enhanced fluorescence and nanopores.

Malavika comes to us as part of the Marie Curie research program doctoral network called Dynamo, funded by the European Union. With her background and experience, she will be a valuable addition to our team and we can't wait to see the exciting results that come from her research.

We believe that collaboration is key to making meaningful advancements in our field, and we are confident that Malavika will bring a fresh perspective and new ideas to our lab.

Proteins are naturally fluorescent in the ultraviolet, offering an appealing approach to probe proteins in their native state without introducing any external fluorescent label. The UV autofluorescence of proteins is based on the presence of tryptophan amino acids, which typically occur as 1 to 5 tryptophan per protein. However, due to weak signals and large backgrounds in the UV, the current technology was restricted to large proteins featuring several tens of tryptophan residues. The vast majority of proteins remained well below the detection sensitivity for single label-free protein detection.

In a recent Nano Letters publication, our team breaks into this sensitivity limit and achieves label-free UV-autofluorescence detection down to the single tryptophan level thanks to a nanophotonic enhancement of the signal. Our approach relies on a rationally-designed combination of plasmonic antennas, antioxidants and background noise reduction techniques to improve the signal to background ratio by over an order of magnitude. Achieving the ultimate sensitivity of UV-FCS down to the single tryptophan regime has wide applications for various communities from nanophotonics to biochemistry.

We conclusively demonstrate UV-fluorescence correlation spectroscopy (UV-FCS) on proteins with a single tryptophan residue. This unlocks the applicability of UV-FCS to a broad library of thousands of proteins, which remained previously inaccessible (over 90% of human proteins have at least one tryptophan residue, but only 4% have more than 20 tryptophans). Fluorescence correlation spectroscopy (FCS) and related techniques have a large impact on molecular biophysics in assessing diffusion properties, local concentrations or kinetic reaction rates.

The signal to background maximization approach is of interest to a wide range of scientists and engineers working with single molecule fluorescence, photonics, or plasmonics. Our article details several multidisciplinary aspects: (i) plasmonic nanophotonic elements to enhance the fluorescence, (ii) antioxidants to neutralize the reactive oxygen species ubiquitous to ultraviolet and (iii) background suppression based on a rational understanding of the background physical origins.

Preprint is also freely availabe on ArXiv 2301.01516

We currently have two open positions with funding from China Scholarship Council CSC and Groupe Ecoles Centrales GEC-CSC:

- One for a PhD: "UV autofluorescence microscopy"

- One for a postdoc: "Fiber-integrated plasmonic nanotweezers to manipulate single proteins"

Find them on the https://gec-csc.fr/ website with application form, section Natural & Life sciences: Physics & Astronomy. Application deadline January 10 2023!

It is not mentioned on the application website but I would expect Chinese nationality is a requirement for eligibility.