Hybrid quantum-classical polarizability model for single molecule biosensing

Zossimova, Ekaterina; Fiedler, Johannes; Vollmer, Frank; Walter, Michael

doi:10.1039/d3nr05396b

Nanoscale

2024

DOI: 10.1039/d3nr05396b

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Hybrid quantum-classical polarizability model for single molecule biosensing

Ekaterina Zossimova,

Johannes Fiedler,

Frank Vollmer

et al.

Abstract: Optical whispering gallery mode biosensors are able to detect single molecules through effects of their polarizability. We address the factors that affect the polarizability of amino acids, which are the...

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Cited by 3 publications

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Single Molecule Thermodynamic Penalties Applied to Enzymes by Whispering Gallery Mode Biosensors

Houghton,

Toropov,

et al. 2024

Advanced Science

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Optical microcavities, particularly whispering gallery mode (WGM) microcavities enhanced by plasmonic nanorods, are emerging as powerful platforms for single‐molecule sensing. However, the impact of optical forces from the plasmonic near field on analyte molecules is inadequately understood. Using a standard optoplasmonic WGM single‐molecule sensor to monitor two enzymes, both of which undergo an open‐to‐closed‐to‐open conformational transition, the work done on an enzyme by the WGM sensor as atoms of the enzyme move through the electric field gradient of the plasmonic hotspot during conformational change has been quantified. As the work done by the sensor on analyte enzymes can be modulated by varying WGM intensity, the WGM microcavity system can be used to apply free energy penalties to regulate enzyme activity at the single‐molecule level. The findings advance the understanding of optical forces in WGM single‐molecule sensing, potentially leading to the capability to precisely manipulate enzyme activity at the single‐molecule level through tailored optical modulation.

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Single Molecule Thermodynamic Penalties Applied to Enzymes by Whispering Gallery Mode Biosensors

Houghton,

Toropov,

et al. 2024

Advanced Science

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pH-sensitive spontaneous decay of functionalized carbon dots in solutions

Dilshener,

Parsons,

Fiedler

2024

The Journal of Chemical Physics

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Carbon quantum dots have become attractive in various applications, such as drug delivery, biological sensing, photocatalysis, and solar cells. Among these, pH sensing via luminescence lifetime measurements of surface-functionalized carbon dots is one application currently investigated for their long lifetime and autonomous operation. In this article, we explore the theoretical connection between excitation lifetimes and the pH value of the surrounding liquid via the protonation and deprotonation of functional groups. Example calculations applied to m-phenylenediamine, phloroglucinol, and tethered disperse blue 1 are shown by applying a separation approach treating the electronic wave function of functional groups separately from the internal electronic structure of the (large) carbon dot. The bulk of the carbon dot is treated as an environment characterized by its optical spectrum that shifts the transition rates of the functional group. A simple relationship between pH, pKa, and mixed fluorescence lifetime is derived from the transition rates of the protonated and deprotonated states. pH sensitivity improves when the difference in the transition rates is greatest between protonated and deprotonated species, with the greatest sensitivity found where the pKa is close to the pH region of interest. The introduced model can directly be extended to consider multicomponent liquids and multiple protonation states.

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Whispering gallery mode sensing through the lens of quantum optics, artificial intelligence, and nanoscale catalysis

Zossimova,

Jones,

Perera

et al. 2024

Applied Physics Letters

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Ultra-sensitive sensors based on the resonant properties of whispering gallery modes (WGMs) can detect fractional changes in nanoscale environments down to the length and time scales of single molecules. However, it is challenging to isolate single-molecule signals from competing noise sources in experiments, such as thermal and mechanical sources of noise, and—at the most fundamental level—the shot noise limit of classical light. Additionally, in contrast to traditional bulk refractive index measurements, analyzing single-molecule signals is complicated by the localized nature of their interactions with nanoscale field gradients. This perspective discusses multifaceted solutions to these challenges, including the use of quantum light sources to boost the signal-to-noise ratio in experiments and leveraging the power of supercomputers to predict the electronic response of molecules to WGM optoplasmonic fields. We further discuss the role of machine learning in WGM sensing, including several advanced models that can predict molecular polarizability and solvent effects. These advancements in WGM spectroscopy and computational modeling can help to decipher the molecular mechanics of enzymes, enable studies of catalysis on the nanoscale, and probe the quantum nature of molecules.

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Hybrid quantum-classical polarizability model for single molecule biosensing

Abstract: Optical whispering gallery mode biosensors are able to detect single molecules through effects of their polarizability. We address the factors that affect the polarizability of amino acids, which are the...

Cited by 3 publications

References 72 publications

Single Molecule Thermodynamic Penalties Applied to Enzymes by Whispering Gallery Mode Biosensors

Single Molecule Thermodynamic Penalties Applied to Enzymes by Whispering Gallery Mode Biosensors

pH-sensitive spontaneous decay of functionalized carbon dots in solutions

Whispering gallery mode sensing through the lens of quantum optics, artificial intelligence, and nanoscale catalysis

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