Measurement of the Diffusion Coefficients of Fluorescence Beads and Quantum Dots by Using Fluorescence Correlation Spectroscopy

Han, Yesul; Lee, Jaeran; Lee, Yu‐Mi; Kim, Sok Won

doi:10.3938/jkps.59.3177

Cited by 10 publications

(7 citation statements)

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“…For freely diffusing QD655, the diffusion times of τ D1 = 2.34 ± 0.14 ms ( f 1 = 73%) and τ D2 = 0.04 ± 0.01 ms ( f 2 = 27%) were determined. The diffusion time τ D1 corresponded to the unhindered diffusion of QD655 and fits very well with data from a previous study reporting τ D = 2.78 ms for quantum dots in PBS 40 . In comparison with freely diffusing organic dyes such as fluorescein, rhodamine 6G or Atto655-carboxylic acid with sizes in the range of ~0.5 nm, this diffusion is 55 times slower, because of the larger particle size of quantum dots 63,64 .…”

Section: Resultssupporting

confidence: 87%

“…The presence of a second diffusion component with the diffusion time τ D2 was not entirely clear. A possible explanation could be the unstable blinking of quantum dots due to the surface charge density, induced by a pH change from pH 9 in borate buffer to pH 7 in PBS as well as the used excitation light intensities 40,65 .…”

Section: Resultsmentioning

confidence: 99%

“…The knowledge of the diffusion coefficient was used to calculate the hydrodynamic particle size, which is twice the hydrodynamic radius R h , using the Stokes-Einstein equationwhere k B is the Boltzmann constant, T is the temperature and η the viscosity of the surrounding medium. Since quantum dots and lipodots were prepared in PBS, the viscosity of η = 2.55 mPa s was used for calculations 40 .…”

Section: Methodsmentioning

confidence: 99%

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Study on intracellular delivery of liposome encapsulated quantum dots using advanced fluorescence microscopy

Bruun

Hille

2019

Sci Rep

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Quantum dots increasingly gain popularity for in vivo applications. However, their delivery and accumulation into cells can be challenging and there is still lack of detailed information. Thereby, the application of advanced fluorescence techniques can expand the portfolio of useful parameters for a more comprehensive evaluation. Here, we encapsulated hydrophilic quantum dots into liposomes for studying cellular uptake of these so-called lipodots into living cells. First, we investigated photophysical properties of free quantum dots and lipodots observing changes in the fluorescence decay time and translational diffusion behaviour. In comparison to empty liposomes, lipodots exhibited an altered zeta potential, whereas their hydrodynamic size did not change. Fluorescence lifetime imaging microscopy (FLIM) and fluorescence correlation spectroscopy (FCS), both combined with two-photon excitation (2P), were used to investigate the interaction behaviour of lipodots with an insect epithelial tissue. In contrast to the application of free quantum dots, their successful delivery into the cytosol of salivary gland duct cells could be observed when applying lipodots. Lipodots with different lipid compositions and surface charges did not result in considerable differences in the intracellular labelling pattern, luminescence decay time and diffusion behaviour. However, quantum dot degradation after intracellular accumulation could be assumed from reduced luminescence decay times and blue-shifted luminescence signals. In addition to single diffusing quantum dots, possible intracellular clustering of quantum dots could be assumed from increased diffusion times. Thus, by using a simple and manageable liposome carrier system, 2P-FLIM and 2P-FCS recording protocols could be tested, which are promising for investigating the fate of quantum dots during cellular interaction.

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Section: Resultssupporting

confidence: 87%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Study on intracellular delivery of liposome encapsulated quantum dots using advanced fluorescence microscopy

Bruun

Hille

2019

Sci Rep

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“…The numerical diffusion is determined with a 3D version of the 2D method of Bailey (Bailey 2017) as 1.2 10 -9 m 2 /s for the used time-step and mesh-size. This is approximately 5000 larger than the diffusion calculated using the Stoke-Einstein equation (Han et al 2011) for the passive fluorescent fluid tracers used in the mixing experiments. In principle, the numerical diffusion can be tuned by varying the time-step and mesh-size, however, attempts to do this led to numerical instabilities and convergence problems.…”

Section: Mixingmentioning

confidence: 68%

Magnetic bead mixing in a microfluidic chamber induced by an in-plane rotating magnetic field

Shanko

Buul

Wang

et al. 2022

Microfluid Nanofluid

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Magnetic microbeads have been widely used for the capturing of biomarkers, as well as for microfluidic mixing for point-of-care diagnostics. In magnetic micromixing, microbead motion is generated by external electromagnets, inducing fluid kinetics, and consequently mixing. Here, we utilize an in-plane rotating magnetic field to induce magnetic bead mixing in a circular microfluidic chamber that allows better access with (optical) readout than for existing micromixing approaches. We analyze the magnetic bead dynamics, the induced fluid profiles and we quantify the mixing performance of the system. The rotating field causes the combination of (1) a global rotating flow counter to the external field rotation induced by magnetic particles moving along the chamber side wall, with (2) local flow perturbations induced by rotating magnetic bead clusters in the central area of the chamber, rotating in the same direction as the external field. This combination leads to efficient mixing performance within 2 min of actuated magnetic field. We integrate magnetic mushroom-shaped features around the circumference of the chamber to generate significantly higher global fluid velocities compared with the no-mushroom configuration, but this results in less efficient mixing due to the absence of the central rotating bead clusters. To validate and understand the experimental results and to predict further enhancement of mixing, we carry out numerical simulations of induced fluid profiles and their corresponding mixing indices, and we explore the additional effect of integrating geometrical structures. The micromixing method we introduce here is particularly suitable for microfluidic devices in which the biochemical assay happens in a microfluidic chamber under no-flow conditions, i.e., with initially stagnant fluids, and for which the time-to-result is critical, such as in point-of-care diagnostics.

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“…Additionally, maximum and minimum transmitted energies are observed for the PBS and fructose–water solution, respectively. It should be noted that the PBS solution is the most viscous material among the tested materials [ 17 ]. However, the fructose–water solution exhibits the lowest viscosity [ 18 ] among them because the addition of fructose in water lowers its viscosity.…”

Section: Resultsmentioning

confidence: 99%

Multiparameter Microwave Characterization and Probing of Ultralow Glucose Concentration Using a Microfabricated Biochip

Adhikari¹,

Kim²,

Kim³

2016

Micromachines

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This paper presents a planar biochip consisting of electromagnetically coupled, symmetric, square open loops for the multiparameter microwave characterization of deionized water, a phosphate-buffered saline solution, and a fructose-deionized water solution. The characterization additionally includes the probing of an ultralow glucose concentration in a very small volume of human sera and in solutions of D-glucose powder and deionized water. The interaction between the coupled electromagnetic field and the aqueous solution sample translates into a predictable relationship between the electrical characteristics of the biochip (magnitude and phase of S-parameters, attenuation, phase constant, group delay, characteristic impedance, and effective complex permittivity) and the physical properties of the solution. Owing to the microfabrication technology used for fabricating the proposed microbiochip, it is possible to develop robust, compact square open loops with a microsized coupling gap that characterizes a very small volume (1 µL) of the sample. Additionally, the biochip's impedance peaks at its resonances were modeled using glucose-level-dependent coupling capacitance between folded square open loops and mutual inductance between center-loaded T-shaped stubs. These peaks linearly shifted in frequencies and markedly varied in impedance. Consequently, a physiologically relevant amount of glucose (50-400 mg/dL) with a high sensitivity (up to 2.036 Ω/(mg¨dL´1)) and an ultralow detection limit (up to 4.8 nmol/L) was linearly detected.

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Measurement of the Diffusion Coefficients of Fluorescence Beads and Quantum Dots by Using Fluorescence Correlation Spectroscopy

Cited by 10 publications

References 0 publications

Study on intracellular delivery of liposome encapsulated quantum dots using advanced fluorescence microscopy

Study on intracellular delivery of liposome encapsulated quantum dots using advanced fluorescence microscopy

Magnetic bead mixing in a microfluidic chamber induced by an in-plane rotating magnetic field

Multiparameter Microwave Characterization and Probing of Ultralow Glucose Concentration Using a Microfabricated Biochip

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