Colloidal quantum dots initiating current bursts in lipid bilayers

Ramachandran, Sujatha; Merrill, N.E.; Blick, Robert H.; Weide, Daniel W. van der

doi:10.1016/j.bios.2004.08.042

Cited by 28 publications

(22 citation statements)

References 10 publications

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“…For instance they have been used to mark individual receptors in cell membranes 3 or to label living embryos at different stages. 4 It has long been a goal to optically trap or otherwise control quantum dots 5 to establish a combined visualization and optical manipulation technique. Optical trapping of aggregates of colloidal quantum dots in two dimensions was recently proved possible 6 using a pulsed YLF laser, and it was claimed that to trap quantum dots with a continuous wave (CW) laser one would need extremely high powers on the order of 20 W. In this Letter, we prove that optical trapping of individual quantum dots using a CW infrared laser operated at only 0.5 W is, in fact, possible.…”

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confidence: 99%

Three-Dimensional Optical Control of Individual Quantum Dots

2008

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We show that individual colloidal CdSe-core quantum dots can be optically trapped and manipulated in three dimensions by an infrared continuous wave laser operated at low laser powers. This makes possible utilizing quantum dots not only for visualization but also for manipulation, an important advantage for single molecule experiments. Moreover, we provide quantitative information about the magnitude of forces applicable to a single quantum dot and of the polarizability of an individual quantum dot.Colloidal quantum dots (QDs) are fluorescent semiconductor nanocrystals.1 They are bright and photostable with a broad excitation spectrum and a narrow emission spectrum, normally distributed around a specific wavelength, dependent on the size of the QD. Absorption of any photons with wavelengths above this specific wavelength causes the formation of an electron-hole pair, the recombination of which results in photon emission. The fluorescent blinking of nanocrystal quantum dots is the result of a bistability between an emitting state where the quantum dot is described as on and the nonemitting off state.2 The extreme brightness and photostability of QDs make them excellent choices as markers to visualize biological systems. For instance they have been used to mark individual receptors in cell membranes 3 or to label living embryos at different stages. 4 It has long been a goal to optically trap or otherwise control quantum dots 5 to establish a combined visualization and optical manipulation technique. Optical trapping of aggregates of colloidal quantum dots in two dimensions was recently proved possible 6 using a pulsed YLF laser, and it was claimed that to trap quantum dots with a continuous wave (CW) laser one would need extremely high powers on the order of 20 W. In this Letter, we prove that optical trapping of individual quantum dots using a CW infrared laser operated at only 0.5 W is, in fact, possible. By observing the Brownian motion of the trapped quantum dots, we deduced the strength of the optical trap and thus found the magnitude of the optical forces acting on a single quantum dot. We used two independent approaches to render probable that it was indeed a single quantum dot in the trap and not an aggregate.An inducible dipole in an inhomogeneous field experiences a force in the direction of the field gradient, the gradient force, F b grad . A particle with an induced dipole moment will be forced toward the laser focus by this three-dimensional restoring force. Hence, the existence of an induced QD dipole moment is essential for optical trapping. Opposing the gradient force are the scattering force, F b scat , and the absorption force, F b abs , which are proportional to the scattering and absorption cross sections, respectively. If infrared laser light, with a wavelength that exceeds the maximum emitted wavelength of the QDs by far, is used for trapping and if the QDs are physically very small in comparison to the focus area of the trapping laser light, then the scattering and absorption forces ...

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confidence: 99%

Three-Dimensional Optical Control of Individual Quantum Dots

2008

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“…These advances made possible to have excellent fluorescent bioprobes, which allowed to study long cellular dynamics, or some specific cellular processes with a better performance than with the traditional organic dyes. QDs can be delivered inside living cells in order to study them, using techniques such as microinjection [42], peptide-induced transport [108], electroporation [109], or phagocytosis [90] as it is shown in Fig. 6.16.…”

Section: Cell Detectionmentioning

confidence: 99%

Quantum Dots for Sensing

Goicoechea

Arregui

Matı́as

2008

Sensors Based on Nanostructured Materials

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Quantum confinement has become a powerful tool for creating new materials with extraordinary properties. Since 1980s, the quantum effects on materials have become relevant as far as the scientific community has focused its attention on smaller devices. When certain particle scale is trespassed, quantum confinement effects start to play a relevant role in the macroscopic properties of the matter. Since their beginning, quantum-confined structures have been widely used in optoelectronic device technology rather than in sensor applications. Nevertheless, sensor applications based on quantum dots experiment a real boost thanks to the semiconductor nanocrystals. The possibility of having high-quality, industrially scaled-up, biocompatible quantum dot nanocrystals has supposed a real breakthrough in the biological and medical fields. Quantum dots significantly improve the sensing tools in applications such as cellular assays, cancer detection, or DNA sequencing. This chapter summarizes the state of the art of the use of quantum dots in the sensor field.First of all, it is necessary to give a definition of what quantum confinement is and why it is so important in order to develop new materials with interesting properties. Historically, the scientific community has classified the existing materials based on their composition, and more recently also based on their internal structure. In other words, the external properties of a material were attributed to its basic components (iron, aluminum, etc.), and how these basic units were geometrically and spatially arranged inside the material. This latter consideration reaches its highest importance with the composite materials, which make possible to engineer their final properties simply by controlling

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“…Among the new surface modifications of QDs, amphiphilic molecules made through exchange interactions with hydrophobic ligands on the surfaces of QDs, such as phospholipids, calixarenes, cyclodextrines, and complex copolymers (in particular polyacrylic acid derivatives), have been used for this purpose. [3][4][5] Alternatively, researchers have also used biocompatible materials such as poly(ethylene glycol) (PEG) * Author to whom correspondence should be addressed. and poly(maleic anhydride alt-1-tetradecene) to coat the surface of QDs.…”

Section: Introductionmentioning

confidence: 99%

Preparation and Characterization of CdSe/ZnS Quantum Dots Encapsulated in Poly(ethylene glycol)-<I>b</I>-Poly(D,L-lactide) Micelle Nanoparticles

Lee¹,

Im²,

Huh³

et al. 2010

J. Nanosci. Nanotech.

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The final goal of this study is to develop multi-functional organic/inorganic hybrid nanoparticles, which can be utilized as biomedical imaging probes and drug delivery carriers. As an initial step toward this goal, we encapsulated CdSe/ZnS quantum dots (QDs) into poly(ethylene glycol)-b-poly(D,L-lactide) (PEG-PLA) micelles using a solid dispersion method. The size and fluorescent intensity of QDs encapsulated in PEG-PLA micelles depended on the amount of incorporated QDs. For example, when the amount of QDs increased from 0.1 to 1.0 microg, the mean diameter increased from 24.2 +/- 6.0 to 211.2 +/- 6.5 nm and the fluorescent intensity changed from 10.2 +/- 1.0 to 469.9 +/- 15.6 (RFU). Stability studies showed that the size and zeta-potential (ZP) of QDs encapsulated in PEG-PLA micelles (QEMs) did not change significantly in response to a change in pH conditions or under a 10% serum condition. We also tested the cytotoxicity and cellular uptake of the QEMs. The viability of HeLa cells treated with micelles for 24 h was 80-100% in various concentration ranges of micelles. Confocal laser scanning microscopic images showed that the QEMs penetrated into the cells, particularly into the cytosolic compartments. Our results suggest that the QEMs may be a promising multi-functional nanocarrier for biomedical imaging and drug delivery.

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Colloidal quantum dots initiating current bursts in lipid bilayers

Cited by 28 publications

References 10 publications

Three-Dimensional Optical Control of Individual Quantum Dots

Three-Dimensional Optical Control of Individual Quantum Dots

Quantum Dots for Sensing

Preparation and Characterization of CdSe/ZnS Quantum Dots Encapsulated in Poly(ethylene glycol)-<I>b</I>-Poly(D,L-lactide) Micelle Nanoparticles

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