Young Investigator Award at BIOS Photonics/West

Since 2007 PicoQuant GmbH awards a "Young Investigator Award" at the session on "Single Molecule Spectroscopy and Imaging" during the BIOS / Photonics West show. Young scientists (age 35 or below) are encouraged to participate in this best paper competition which offers a cash award worth 750 USD. Participants must be both the primary author and presenter of an accepted abstract to be eligible. The proceedings paper also has to be submitted at least 1 week before the meeting starts for review purposes.

2008 award

All talks presented in that session were of high quality so that it proved extremely difficult for the jury to nominate the winner. In the end the price was awarded to Andrea M. Armani from the California Institute of Technology (CalTech) for

Label-free detection of cytokines using optical microcavities
Andrea M. Armani, Scott E. Fraser, California Institute of Technology

Ultra-high-Q microresonators have demonstrated sensitive and specific chemical and biological detection.[1, 2] The sensitivity is derived from the long photon lifetime inside the cavity which amplifies small signals. Specificity is achieved through surface functionalization. Recently, microtoroid resonators demonstrated quality factors greater than 100 million. Here, these ultra-high-Q microcavities are shown to be capable of performing label-free, single molecule studies [3, 4]. The detection mechanism is new and relies upon a thermo-optic mechanism to enhance resonant wavelength shifts induced through binding of a molecule.
In the present work, planar arrays of ultra-high-Q microtoroid resonators were used to detect Interleukin-2 (IL-2) in fetal bovine serum (FBS). IL-2 is a cytokine released in response to immune system activation by extrinsic and intrinsic stimuli. The surface of the microtoroids was sensitized for detection using anti-IL-2 and a series of "doped" serum solutions were prepared containing [300, 600, 900]aM of IL-2. The label-free, single molecule detection data and the theoretical basis for detection will be presented.
[1] A. M. Armani, R. P. Kulkarni, S. E. Fraser, R. C. Flagan, and K. J. Vahala, Science, 2007.
[2] A. M. Armani and K. J. Vahala, Optics Letters, vol. 31, pp. 1896-1898, 2006.
[3] A. M. Armani, D. K. Armani, B. Min, K. J. Vahala, and S. M. Spillane, Applied Physics Letters, vol. 87, pp. 151118, 2005.
[4] D. K. Armani, T. J. Kippenberg, S. M. Spillane, and K. J. Vahala, Nature, vol. 421, pp. 925-928, 2003.

2007 award

The quality of the talks presented in that session were very high so that it proved extremely difficult for the jury to nominate the winner. In the end the price was split between H.R.C. Dietrich (TU Delft) and M.I. Rudenko (University of California/Santa Cruz) for

A new optical method for characterizing single molecule interactions
H. R. C. Dietrich, B. Vermolen, B. Rieger, I. T. Young, Y. Garini, Technische Univ. Delft (Netherlands)

In recent years, fundamental biochemical and biophysical research has started to apply single molecule techniques rather than techniques that look at a general population of molecules. This allows one to gain detailed insight into biological processes and functions of biomolecules. Therefore, the improvement and development of new single molecular methods are of increasing importance. DNA-protein interactions are of interest due to their importance in the control of cellular processes. These interactions occur, for example, in transcription regulation, DNA replication and DNA repair. We have developed an optical method to study dynamic behaviors related to DNA-protein interactions. This technique is based on sub-micron gold beads that scatter polychromatic light. One end of the DNA molecule is immobilized onto a gold support; the other end is attached to a gold bead (d = 80 nm). In solution, the DNA/bead system is moving within a volume that depends on the length of the DNA polymer. The precise determination of this action volume gives information on the effective length of the DNA tether and its variation due to the interaction with other proteins or with changes in the environment (e.g. pH and salt concentration). This method allows the detection and study of single molecular interactions in a very simple and robust way. We use a darkfield microscope equipped with a sensitive CCD camera in order to image the DNA/bead system. We can record about 20 images per second. We then analyze the motion of each individual bead/molecule over time intervals ranging up to two hours as our system setup does not suffer from bleaching. From the change in the bead position due to Brownian motion, we can deduce diffusion characteristics and other relevant parameters. We will present results of experiments based on the analysis of the DNA/bead system under varying conditions of fluid viscosity, salt concentration, addition of recA and naked DNA.

Integration and characterization of SiN nanopores for single-molecule detection in liquid-core ARROW waveguides
M. I. Rudenko, D. Yin, Univ. of California/Santa Cruz; M. Holmes, A. R. Hawkins, Brigham Young Univ.; H. Schmidt, Univ.of California/Santa Cruz

Single molecule detection using microfluidic waveguide channels provides researchers with valuable information for drug development and promotes fascinating discoveries regarding molecular dynamics on the nanoscale. We have developed a novel device (“lab on chip”) based on low loss liquid-core antiresonant reflecting optical (ARROW) waveguides with single molecule fluorescence sensitivity and SiN nanopores, integrated on one platform. Analysis of concurrent optical (fluorescence) and electrical (ionic current blockade) signals provides new single molecule detection capabilities. The ARROW waveguide consists of alternating PECVD-deposited SiN and SiO2 layers. The channel is formed by a sacrificial etch. We measured ARROW channel resistance with solution of 0.1M KCl and Hepes at pH 7.6 as a ribosome buffer and also different concentrations of KCl using Ag/AgCl electrodes, and found impedance to be in GOhm range. In order to integrate a nanopore, a micropore is first dry etched through the top layers of the waveguide leaving only a SiN layer covering the core. A focused ion beam machine is used to form a 60-120 nm (top diameter) conical nanopore in the SiN membrane. The pore size can be reduced further to 20-40 nm using a scanning electron microscope. Detailed studies of the nanopore fabrication, size determination, electrical properties and particle translocation will be presented. In summary, we have shown that nanopores can be integrated with liquid-core optical waveguides to pave the way for electrical and optical single molecule detection on a single chip.