Sensing of Flow and Shear Stress Using Fluorescent Molecular Rotors

Haidekker, Mark A.; Akers, Walter J.; Lichlyter, Darcy; Brady, Thomas P.; Theodorakis, Emmanuel A.

doi:10.1166/sl.2005.003

Cited by 26 publications

(54 citation statements)

References 10 publications

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“…In addition, 6 showed no intensity variations in a cuvette with and without stirring [19] (data not shown). On the other hand, dyes with asymmetrical headgroup (2, 3, and 4) exhibited increasing intensity under the low exposure conditions of the custom laser fluorophotometer.…”

Section: Z-e Isomer Recovery Dynamicsmentioning

confidence: 90%

“…The model functions were the exponential association (Eq. 4), based on an earlier publication [19], and the Boltzmann sigmoidal (Eq. 5) that potentially better reflects low intensity increases in the low-flow region:…”

Section: Discussionmentioning

confidence: 99%

“…None the less, several studies demonstrate that the information provided by the fluorescence of molecular rotors is useful, and molecular rotors have been used, for example, to investigate protein conformal changes [16,17], phopsholipid bilayer microviscosity [7], and the microviscosity of the interior of cells [18]. We reported an intriguing new phenomenon, whereby the fluorescence emission intensity increases in moving fluids [19]. This phenomenon can be seen in an experiment as simple as a stirred dye solution in a fluoroscopic cuvette.…”

Section: Introductionmentioning

confidence: 86%

“…This phenomenon can be seen in an experiment as simple as a stirred dye solution in a fluoroscopic cuvette. The intensity increase I over the no-flow baseline was dependent both on the viscosity of the solvent η and the velocity of flow v, and I could be described very accurately by the empirical relationship [19] …”

Section: Introductionmentioning

confidence: 90%

“…Moreover, the sensitivity of the intensity increase at very low flow rates is unusually high, such that instruments of comparable sensitivity (e.g., heated-plate flow meters) show orders of magnitude lower spatial resolution, and flow measurement with comparable resolution (e.g., particle tracking) has much lower sensitivity. Based on our studies, prerequisite for flow sensitivity is a polar functional group on the molecular rotor and a polar solvent: DCVJ (1) does not exhibit this phenomenon at all, and a carboxylic-acid derivative (CCVJ, 2) does not exhibit this phenomenon in nonpolar fluids, such as hexanes [19,20]. Based on these findings, we hypothesized that either polar-polar interaction or hydrogen bond formation play a role in the apparent flow sensitivity.…”

Section: Introductionmentioning

confidence: 92%

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Apparent Shear Sensitivity of Molecular Rotors in Various Solvents

et al. 2015

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Fluorescent environment-sensitive dyes often change their spectral properties concomitantly with multiple solvent properties, such as polarity, protonation, hydrogen bond formation, or viscosity. Careful consideration of the response is needed when a fluorescent dye is used to report a single property. Recently, we observed an increase of emission intensity of viscosity-sensitive molecular rotors in fluids subject to flow and speculated that either polar-polar interaction or hydrogen bond formation play a role in the apparent flow sensitivity. In this study, we show experimental evidence that photoisomerization to an isomer with a lower quantum yield, first proposed by Rumble et al. (J Phys Chem A 116(44):10786-10792, 2012), plays a key role in the observed phenomenon. We subjected four molecular rotors with different electron acceptor motifs to fluid flow in solvents of different polarity and ability to form hydrogen bonds. We also measured the isomerization dynamics in a custom fluorophotometer with extremely low light exposure. Our results indicate that the photoisomerization rate depends both on the solvent and on the electron acceptor group, as does the recovery of the original isomer in the dark. In most solvents, recovery of the dark isomer is much more rapid than originally reported, and a state of quasiequilibrium between both isomers is possible. Moreover, the sensitivity (i.e., relative intensity increase at the same flow rate) is also solvent-dependent. The intensity increase can be detected at very low velocities (as low as 0.06 mm/s). Characteristic for fluorescent dyes is the high spatial resolution, and no flow measurement device with comparable sensitivity and spatial resolution exists, although the nature of the solvent needs to be taken into account for quantitative flow measurement.

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Section: Z-e Isomer Recovery Dynamicsmentioning

confidence: 90%

Section: Discussionmentioning

confidence: 99%