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Timeline of Christof Fattinger

2019
Jan
28
Published new article




Article

Principles for Sensitive and Robust Biomolecular Interaction Analysis: The Limits of Detection and Resolution of Diffrac...

Published: 28 January 2019 by American Physical Society (APS) in Physical Review Applied

doi: 10.1103/physrevapplied.11.014056

Label-free biosensors enable the monitoring of biomolecular interactions in real time, which is key to the analysis of the binding characteristics of biomolecules. While refractometric optical biosensors such as surface plasmon resonance (SPR) are sensitive and well-established, they are susceptible to any change of the refractive index in the sensing volume caused by minute variations in composition of the sample buffer, temperature drifts, and most importantly nonspecific binding to the sensor surface in complex fluids such as blood. The limitations arise because refractometric sensors measure the refractive index of the entire sensing volume. Conversely, diffractometric biosensors–for example, focal molography–only detect the diffracted light from a coherent assembly of analyte molecules. Thus any refractive index distribution that is noncoherent with respect to this molecular assembly does not add to the coherent signal. This makes diffractometric biosensors inherently robust and enables sensitive measurements without reference channels or temperature stabilization. The coherent assembly is generated by selective binding of the analyte molecules to a synthetic binding pattern–the mologram. Focal molography has been introduced theoretically [C. Fattinger, Phys. Rev. X 4, 031024 (2014)] and verified experimentally [V. Gatterdam, A. Frutiger, K.-P. Stengele, D. Heindl, T. Lübbes, J. Vörös, and C. Fattinger, Nat. Nanotechnol. 12, 1089 (2017)] in previous papers. However, further understanding of the underlying physics and a diffraction-limited readout is needed to unveil its full potential. This paper introduces refined theoretical models, which can accurately quantify the amount of biological matter bound to the mologram from the diffracted intensity. In addition, it presents measurements of diffraction-limited molographic foci, i.e., Airy discs. These improvements enable us to demonstrate a resolution in real-time binding experiments comparable to the best SPR sensors without the need for temperature stabilization or drift correction and to detect low-molecular-weight compounds label free in an endpoint format. The presented experiments exemplify the robustness and sensitivity of the diffractometric sensor principle.

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2018
Nov
26
Published new article




Article

Image reversal reactive immersion lithography improves the detection limit of focal molography

Published: 26 November 2018 by The Optical Society in Optics Letters

doi: 10.1364/ol.43.005801

Focal molography is a label-free optical biosensing method that relies on a coherent pattern of binding sites for biomolecular interaction analysis. Reactive immersion lithography (RIL) is central to the patterning of molographic chips but has potential for improvements. Here, we show that applying the idea of image reversal to RIL enables the fabrication of coherent binding patterns of increased quality (i.e., higher analyte efficiency). Thereby the detection limit of focal molography in biological assays can be improved.

3 Reads | 0 Citations
2018
Aug
23
Published new article






Principles for sensitive and robust biomolecular interaction analysis - The limits of detection and resolution of diffra...

Published: 23 August 2018 by ArXiv

doi:

Label-free biosensors enable the monitoring of biomolecular interactions in real-time, which is key to the analysis of the binding characteristics of biomolecules. While refractometric optical biosensors are sensitive and well-established, they are susceptible to any change of the refractive index in the sensing volume caused by minute variations in composition of the sample buffer, temperature drifts and nonspecific binding to the sensor surface. Refractometric biosensors require reference channels as well as temperature stabilisation and their applicability in complex fluids such as blood is limited by nonspecific bindings. Focal molography does not measure the refractive index of the entire sensing volume but detects the diffracted light from a coherent assembly of analyte molecules. Thus, it does not suffer from the limitations of refractometric sensors since they stem from non-coherent processes and therefore do not add to the coherent molographic signal. The coherent assembly is generated by selective binding of the analyte molecules to a synthetic binding pattern - the mologram. Focal Molography has been introduced theoretically and verified experimentally in previous papers. However, further understanding of the underlying physics and a diffraction-limited readout is needed to unveil its full potential. This paper introduces refined theoretical models which can accurately quantify the amount of matter bound to the mologram from the diffracted intensity. In addition, it presents measurements of diffraction-limited molographic foci. These improvements enabled us to demonstrate a resolution in real-time binding experiments comparable to the best SPR sensors, without the need of temperature stabilisation or drift correction and to detect small molecules label-free in an endpoint format. The presented experiments exemplify the robustness and sensitivity of diffractometric sensors.

0 Reads | 0 Citations
2011
Jul
05
Published new article






Exploiting Molecular Biology by Time-Resolved Fluorescence Imaging

Published: 05 July 2011 by Springer Nature in Springer Series in Optical Sciences

doi: 10.1007/978-3-642-18443-7_14

Many contemporary biological investigations rely on highly sensitive in vitro assays for the analysis of specific molecules in biological specimens, and the main part of these assays depends on high-sensitivity fluorescence detection techniques for the final readout. The analyzed molecules and molecular interactions in the specimen need to be detected in the presence of other highly abundant biomolecules, while the analyzed molecules themselves are only present at nano-, pico-, or even femtomolar concentration.A short scientific rationale of fluorescence is presented. It emphasizes the use of fluorescent labels for sensitive assays in life sciences and specifies the main properties of an ideal fluorophore. With fluorescence lifetimes in the microsecond range and fluorescence quantum yield of 0.4 some water soluble complexes of Ruthenium like modified Ru(sulfobathophenanthroline) complexes fulfill these properties. They are outstanding fluorescent labels for ultrasensitive assays as illustrated in two examples, in drug discovery and in point of care testing.We discuss the fundamentals and the state-of-the-art of the most sensitive time-gated fluorescence assays. We reflect on how the imaging devices currently employed for readout of these assays might evolve in the future. Many contemporary biological investigations rely on highly sensitive in vitro assays for the analysis of specific molecules in biological specimens, and the main part of these assays depends on high-sensitivity fluorescence detection techniques for the final readout. The analyzed molecules and molecular interactions in the specimen need to be detected in the presence of other highly abundant biomolecules, while the analyzed molecules themselves are only present at nano-, pico-, or even femtomolar concentration.A short scientific rationale of fluorescence is presented. It emphasizes the use of fluorescent labels for sensitive assays in life sciences and specifies the main properties of an ideal fluorophore. With fluorescence lifetimes in the microsecond range and fluorescence quantum yield of 0.4 some water soluble complexes of Ruthenium like modified Ru(sulfobathophenanthroline) complexes fulfil these properties. They are outstanding fluorescent labels for ultrasensitive assays as illustrated in two examples, in drug discovery and in point of care testing.We discuss the fundamentals and the state-of-the-art of the most sensitive time-gated fluorescence assays. We reflect on how the imaging devices currently employed for readout of these assays might evolve in the future.

3 Reads | 0 Citations
2015
Jul
13
Conference participation




Christof Fattinger participated at conference 4th International Symposium on Sensor Science.

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