Biosensors are powerful tools for modern basic research and biomedical diagnostics. Their development requires substantial input from the chemical sciences. Sensors or probes with an optical readout, ...such as fluorescence, offer rapid, minimally invasive sensing of analytes with high spatial and temporal resolution. The near‐infrared (NIR) region is beneficial because of the reduced background and scattering of biological samples (tissue transparency window) in this range. In this context, single‐walled carbon nanotubes (SWCNTs) have emerged as versatile NIR fluorescent building blocks for biosensors. Here, we provide an overview of advances in SWCNT‐based NIR fluorescent molecular sensors. We focus on chemical design strategies for diverse analytes and summarize insights into the photophysics and molecular recognition. Furthermore, different application areas are discussed—from chemical imaging of cellular systems and diagnostics to in vivo applications and perspectives for the future.
Optical biosensors are important tools for basic research and non‐invasive diagnostics. Carbon nanotubes are versatile near‐infrared fluorescent and non‐bleaching materials that can be chemically functionalized to detect a broad variety of biomolecules. This Review highlights chemical design strategies and provides a comprehensive overview of the recent developments in this dynamic field.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Semiconducting single-wall carbon nanotubes (SWCNTs) fluoresce in the near-infrared (NIR), and the emission wavelength depends on their structure (chirality). Interactions with other molecules affect ...their fluorescence, which has successfully been used for SWCNT-based molecular sensors. So far, most such sensors are assembled from crude mixtures of different SWCNT chiralities, which causes polydisperse sensor responses as well as spectral congestion and limits their performance. The advent of chirality-pure SWCNTs is about to overcome this limitation and paves the way for the next generation of biosensors. Here, we discuss the first examples of chirality-pure SWCNT-based fluorescent biosensors. We introduce routes to such sensors via aqueous two-phase extraction-assisted purification of SWCNTs and highlight the critical interplay between purification and surface modification procedures. Applications include the NIR detection and imaging of neurotransmitters, reactive oxygen species, lipids, bacterial motives, and plant metabolites. Most importantly, we outline a path toward how such monodisperse (chirality-pure) sensors will enable advanced multiplexed sensing with enhanced bioanalytical performance.
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IJS, KILJ, NUK, PNG, UL, UM
Single‐walled carbon nanotubes (SWCNTs) are versatile near infrared (NIR) fluorescent building blocks for biosensors. Their surface is chemically tailored to respond to analytes by a change in ...fluorescence. However, intensity‐based signals are easily affected by external factors such as sample movements. Here, we demonstrate fluorescence lifetime imaging microscopy (FLIM) of SWCNT‐based sensors in the NIR. We tailor a confocal laser scanning microscope (CLSM) for NIR signals (>800 nm) and employ time correlated single photon counting of (GT)10‐DNA functionalized SWCNTs. They act as sensors for the important neurotransmitter dopamine. Their fluorescence lifetime (>900 nm) decays biexponentially and the longer lifetime component (370 ps) increases by up to 25 % with dopamine concentration. These sensors serve as paint to cover cells and report extracellular dopamine in 3D via FLIM. Therefore, we demonstrate the potential of fluorescence lifetime as a readout of SWCNT‐based NIR sensors.
DNA‐functionalized single‐walled carbon nanotubes (SWCNTs) as near‐infrared fluorescent sensors for the neurotransmitter dopamine are reported. These sensors change their fluorescence lifetime and this is measured by pulsed excitation and single‐photon counting. Lifetimes are sensitive to the concentration of dopamine, which can be used for imaging dopamine release by cells.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Most of the existing literature on optimal trade execution in limit order book models assumes that resilience is positive. But negative resilience also has a natural interpretation, as it models ...self-exciting behaviour of the price impact, where trading activities of the large investor stimulate other market participants to trade in the same direction. In the paper we discuss several new qualitative effects on optimal trade execution that arise when we allow resilience to take negative values. We do this in a framework where both market depth and resilience are stochastic processes.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Fluorescence lifetime imaging is a powerful technique. In their Research Article (e202300682), Sebastian Kruss et al. used single‐walled carbon nanotubes (SWCNTs) as fluorescent probes/sensors for ...biomolecules in the near infrared (NIR) tissue transparency window. The SWCNTs were functionalized with DNA to render them selective for the important neurotransmitter dopamine. Time correlated single photon counting in a confocal microscope was used to read out fluorescence lifetime, which changed with dopamine concentration. This approach enabled the measurement of dopamine around cells. Thus, the fluorescence lifetime of SWCNTs becomes a new sensing strategy for bio(molecules).
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We start with a stochastic control problem where the control process is of finite variation (possibly with jumps) and acts as integrator both in the state dynamics and in the target functional. ...Problems of such type arise in the stream of literature on optimal trade execution pioneered by Obizhaeva and Wang (J. Financ. Mark. 16:1–32,
2013
) (models with finite resilience). We consider a general framework where the price impact and the resilience are stochastic processes. Both are allowed to have diffusive components. First we continuously extend the problem from processes of finite variation to progressively measurable processes. Then we reduce the extended problem to a linear–quadratic (LQ) stochastic control problem. Using the well-developed theory on LQ problems, we describe the solution to the obtained LQ one and translate it back to the solution for the (extended) initial trade execution problem. Finally, we illustrate our results by several examples. Among other things, the examples discuss the Obizhaeva–Wang model with random (terminal and moving) targets, the necessity to extend the initial trade execution problem to a reasonably large class of progressively measurable processes (even going beyond semimartingales), and the effects of diffusive components in the price impact process and/or the resilience process.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
7.
Inhomogeneous affine Volterra processes Ackermann, Julia; Kruse, Thomas; Overbeck, Ludger
Stochastic processes and their applications,
August 2022, 2022-08-00, Volume:
150
Journal Article
Peer reviewed
We extend recent results on affine Volterra processes to the inhomogeneous case. This includes moment bounds of solutions of Volterra equations driven by a Brownian motion with an inhomogeneous ...kernel K(t,s) and inhomogeneous drift and diffusion coefficients b(s,Xs) and σ(s,Xs). In the case of affine b and σσT we show how the conditional Fourier–Laplace functional can be represented by a solution of an inhomogeneous Riccati–Volterra integral equation. For a kernel of convolution type K(t,s)=K¯(t−s) we establish existence of a solution to the stochastic inhomogeneous Volterra equation. If in addition b and σσT are affine, we prove that the conditional Fourier–Laplace functional is exponential–affine in the past path. Finally, we apply these results to an inhomogeneous extension of the rough Heston model used in mathematical finance.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The molecules released by cells are a fingerprint of their current state. Methods that measure them with high spatial and temporal resolution may provide valuable insights into cell physiology and ...diseases. Here, a nanosensor coating is developed that transforms standard cell culture materials/dishes into “Smart Slides” capable of optically monitoring biochemical efflux from cells. For this purpose, single wall carbon nanotubes (SWCNTs) that are fluorescent in the beneficial near‐infrared (NIR, 850 – 1700 nm) window are used. They are chemically tailored to detect the neurotransmitter dopamine by a change in fluorescence intensity. These nanosensors are spin‐coated on glass substrates and it is shown that such sensor layers can be sterilized by UV light and can be stored in dry condition or buffer for at least 6 weeks and have little influence on cell viability. The optimal sensor density to maximize sensitivity is also identified. Finally, these substrates are used to image dopamine release from neuronal cells cultivated on top in the presence of various psychotropic substances, which represents a system to test pharmaceuticals for neurological or neurodegenerative diseases. Therefore, Smart Slides are a powerful tool to monitor cellular processes in cell culture systems.
Single wall carbon nanotubes (SWCNTs) exhibit fluorescence in the near‐infrared (NIR, >880 nm) and can be effectively functionalized with DNA to serve as highly sensitive sensors. These versatile SWCNT sensors can be coated on diverse surfaces, forming smart functional sensor coatings. They enable real‐time monitoring of cell responses to substances and drugs, offering valuable insights into cellular behavior.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Biochemical processes are fast and occur on small‐length scales, which makes them difficult to measure. Optical nanosensors based on single‐wall carbon nanotubes (SWCNTs) are able to capture such ...dynamics. They fluoresce in the near‐infrared (NIR, 850–1700 nm) tissue transparency window and the emission wavelength depends on their chirality. However, NIR imaging requires specialized indium gallium arsenide (InGaAs) cameras with a typically low resolution because the quantum yield of normal Si‐based cameras rapidly decreases in the NIR. Here, an efficient one‐step phase separation approach to isolate monochiral (6,4)‐SWCNTs (880 nm emission) from mixed SWCNT samples is developed. It enables imaging them in the NIR with high‐resolution standard Si‐based cameras (>50× more pixels). (6,4)‐SWCNTs modified with (GT)10‐ssDNA become highly sensitive to the important neurotransmitter dopamine. These sensors are 1.7× brighter and 7.5× more sensitive and allow fast imaging (<50 ms). They enable high‐resolution imaging of dopamine release from cells. Thus, the assembly of biosensors from (6,4)‐SWCNTs combines the advantages of nanosensors working in the NIR with the sensitivity of (Si‐based) cameras and enables broad usage of these nanomaterials.
(6,4)‐single‐wall carbon nanotubesfluoresce in the near‐infrared (NIR, 880 nm) and can be chemically functionalized with DNA to act as sensors. They provide access to the sweet spot between the efficiency of (Si) cameras of standard microscope equipment and the advantages of NIR, which is shown by high‐resolution mapping of dopamine release from cells.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
We analyse an optimal trade execution problem in a financial market with stochastic liquidity. To this end, we set up a limit order book model in continuous time. Both order book depth and resilience ...are allowed to evolve randomly in time. We allow trading in both directions and for càdlàg semimartingales as execution strategies. We derive a quadratic BSDE that under appropriate assumptions characterises minimal execution costs, and we identify conditions under which an optimal execution strategy exists. We also investigate qualitative aspects of optimal strategies such as e.g. appearance of strategies with infinite variation or existence of block trades, and we discuss connections with the discrete-time formulation of the problem. Our findings are illustrated in several examples.
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