Laboratory of Biosensing and Biophotonics

Blood oxygen saturation is one of the most prominent measurement parameters in daily clinical routine. However up to now, it is not possible to continuously monitor this parameter reliably in mobile patients. High-risk patients suffering from cardiovascular diseases could benefit from long-term monitoring of blood oxygen saturation. In this paper, we present a minimally invasive, implantable patient monitor which is capable of monitoring vital signs. The capability of this multimodal sensor to subcutaneously determine blood pressure, pulse and ECG has been demonstrated earlier. This paper focuses on monitoring of blood oxygen saturation. Even though the signal amplitudes are much weaker than for standard extracorporeal measurements, photoplethysmographic signals were recorded with high quality in vivo directly on subcutaneous muscle tissue. For the first time, it has been shown that blood oxygen saturation can be measured with an implantable, but extravascular sensor. The sensor was...

Dynamic Power Flow Controller (DPFC) provides steady-state and dynamic power flow control for power lines and is considered as a Flexible AC Transmission System (FACTS) controller. This paper deals with control of a standard DPFC using a Discrete Event ...

Glycogen phosphorylase (GlyP) was the first allosteric enzyme to be described. Yet, the precise dynamic changes in solution phase structure and stability that underpin functional regulation have remained elusive. We have developed a new fully-automated and highly flexible implementation of hydrogen/deuterium-exchange mass spectrometry, operating in the millisecond regime. This enabled measurements of the solution phase local structural dynamics involved in allosteric regulation of GlyP. Here, we quantify GlyP structural dynamics in solution, describing correlated changes in structure in the activated (pSer14) and inhibited (glucose-6-phosphate bound) forms of the enzyme. The sensitivity of these measurements discerned that the 250s’ loop is natively disordered in the apo T-state, adopting a more ordered conformation in the active state. The quantitative change in stability of the 280s loop is identified, providing the first direct evidence of the entropic switch that sterically regu...

Probing individual chemical reactions is key to mapping reaction pathways. Trace analysis of sub-kDa reactants and products is obfuscated by labels, however, as reaction kinetics are inevitably perturbed. The thiol-disulfide exchange reaction is of specific interest as it has many applications in nanotechnology and in nature. Redox cycling of single thiols and disulfides has been unresolvable due to a number of technological limitations, such as an inability to discriminate the leaving group. Here, we demonstrate detection of single-molecule thiol-disulfide exchange using a label-free optoplasmonic sensor. We quantify repeated reactions between sub-kDa thiolated species in real time and at concentrations down to 100’s of attomolar. A unique sensing modality is featured in our measurements, enabling the observation of single disulfide reaction kinetics and pathways on a plasmonic nanoparticle surface. Our technique paves the way towards characterising molecules in terms of their char...

Understanding the kinetics and dynamics of single enzymes is crucial for understanding biomolecular processes at a fundamental level. Sensors that provide sensitivity to single enzyme conformational changes at micro/nanoseconds time resolution are required to study these motions. Here, we present an optical sensor based on plasmonically enhanced whispering gallery modes capable of studying the dynamics of single enzymes over timescales of ns-hours. By combing surface chemistry methods for attachment of single enzymes in a preferred orientation with lock-in measurement techniques, we detect signals from single enzyme-substrate interactions in the microsecond timescale. Specific immobilization of enzymes on gold nanoparticles is achieved via histidine groups added to one of the termini of the enzyme. This enables reversible attachment of recombinantly expressed and purified enzymes. The molecular motions of the enzyme and its interactions with the substrate is measured as a shift in the whispering gallery mode resonance frequency. A Pound-Drever-Hall lock is used to track the resonance shift with a microsecond time resolution. Combined with advanced signal processing and simulations, this will enable studying the functional conformational movements of enzymes at the single-molecule level. Future work includes adding microfluidics for fast and automated sample delivery, addition of multiple channels of excitation by combing different wavelengths and polarizations of light. This work provides a proof-of-concept next generation optical sensor for single-molecule enzymology, fundamental protein research, drug discovery and point-of-care devices.