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Molecular motor propelled filaments reveal light-guiding in nanowire arrays for enhanced biosensing.

ten Siethoff L, Lard M, Generosi J, Andersson HS, Linke H, Månsson A - Nano Lett. (2014)

Bottom Line: This enables effective collection of light emitted by fluorescent analytes located at different focal planes along the nanowire.We unequivocally demonstrate the light-guiding effect using a novel method whereby the changes in emitted fluorescence intensity are observed when fluorescent cytoskeletal filaments are propelled by molecular motors along the wires.The findings are discussed in relation to nanobiosensor developments, other nanotechnological applications, and fundamental studies of motor function.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry and Biomedical Sciences, Linnaeus University , SE-391 82 Kalmar, Sweden.

ABSTRACT
Semiconductor nanowire arrays offer significant potential for biosensing applications with optical read-out due to their high surface area and due to the unique optical properties of one-dimensional materials. A challenge for optical read-out of analyte-binding to the nanowires is the need to efficiently collect and detect light from a three-dimensional volume. Here we show that light from fluorophores attached along several μm long vertical Al2O3 coated gallium phosphide nanowires couples into the wires, is guided along them and emitted at the tip. This enables effective collection of light emitted by fluorescent analytes located at different focal planes along the nanowire. We unequivocally demonstrate the light-guiding effect using a novel method whereby the changes in emitted fluorescence intensity are observed when fluorescent cytoskeletal filaments are propelled by molecular motors along the wires. The findings are discussed in relation to nanobiosensor developments, other nanotechnological applications, and fundamental studies of motor function.

No MeSH data available.


Related in: MedlinePlus

Nanowire arrays. a, Scanning electron microscopy(SEM) image ofnanowires in 50 × 50 μm2 array with 1 μminterwire distance and 5 μm nanowire length. Close up view ininset. b, Fluorescence micrograph from in vitro motility assay experimentwith the same type of array geometry as in panel a before the additionof ATP. Focus is kept on the top of the nanowires. Actin filaments(bright fluorescent lines) are aligned with nanowire arrays beingattached to HMM on the tip of the nanowires. Strongly fluorescentspots on nanowires attributed to light-guiding from fluorescent actinfilaments interacting with the wires along their length. Occasionalfluorescent spots outside the array in panel b (arrows) are attributedto actin filaments attached to nanowires spuriously formed by parasiticgrowth (examples of such wires also indicated in panel a) and aretherefore in focus.
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fig2: Nanowire arrays. a, Scanning electron microscopy(SEM) image ofnanowires in 50 × 50 μm2 array with 1 μminterwire distance and 5 μm nanowire length. Close up view ininset. b, Fluorescence micrograph from in vitro motility assay experimentwith the same type of array geometry as in panel a before the additionof ATP. Focus is kept on the top of the nanowires. Actin filaments(bright fluorescent lines) are aligned with nanowire arrays beingattached to HMM on the tip of the nanowires. Strongly fluorescentspots on nanowires attributed to light-guiding from fluorescent actinfilaments interacting with the wires along their length. Occasionalfluorescent spots outside the array in panel b (arrows) are attributedto actin filaments attached to nanowires spuriously formed by parasiticgrowth (examples of such wires also indicated in panel a) and aretherefore in focus.

Mentions: We chose GaP as our material system becauseof the established biocompatibility of GaP nanowires21 and the generally advantageous optical properties of theIII–V semiconductor materials.3,12,13 Nanowires were produced by gold-particle-seeded metalorganic vapor phase epitaxy (MOVPE)22 (Figures 1a and S1). Because nanowiregrowth is initialized by GaP assembly at the interface of the substrateto the gold particle, the wire size and array geometry (Figures 1a and 2a) can be definedby electron beam lithography (EBL)-defined gold patterning. The useof regular nanowire spacing enables the growth of arrays with uniformwire length. After testing several surface derivatization procedures(see Supporting Information, results section)with respect to actomyosin motility quality (speed and fraction ofmobile actin filaments) we chose atomic layer deposition of Al2O3 on nanowires (Figure 1a) and surrounding areas, creating suitable surface contact anglesfor motility23 without the need for priorsilanization. Together with the GaP nanowire core diameter (30–50nm in different arrays), the 60 nm of Al2O3 coatingresulted in a total nanowire diameter of 150–171 nm (∼160nm unless otherwise stated). The wire length was either 0.96 ±0.03 or 5 ± 0.2 μm (mean ± standard deviation) indifferent arrays. In vitro motility studies were performed14 by infusing HMM (120 μg/mL) into flowcells formed by a chip with nanowire arrays (Figure 1) as the ceiling and a coverslip as the floor. Irrespectiveof the actual geometry, “top” and “bottom”in the text below are defined as indicated in Figure 1b. The HMM-induced sliding of Alexa Fluor 488 phalloidin labeledactin filaments was observed after infusion of assay solution (1 mMMgATP; 22–25 °C). The filaments were observed using epi-fluorescencemicroscopy. We used a Nikon Eclipse TE300 inverted microscope withHg-lamp illumination, Nikon 100 × 1.4 NA oil immersion objective,FITC filter set [excitation, 465–495 nm; dichroic mirror cutoff,505 nm; emission barrier filter, 515–555 nm] and a HammamatsuEMCCD camera. Further details of the experimental methods are givenin the Supporting Information, methodssection, e.g., quantitative analysis of the motility quality of filamentsmoving up and down wires (Supporting Figures S2–S3).


Molecular motor propelled filaments reveal light-guiding in nanowire arrays for enhanced biosensing.

ten Siethoff L, Lard M, Generosi J, Andersson HS, Linke H, Månsson A - Nano Lett. (2014)

Nanowire arrays. a, Scanning electron microscopy(SEM) image ofnanowires in 50 × 50 μm2 array with 1 μminterwire distance and 5 μm nanowire length. Close up view ininset. b, Fluorescence micrograph from in vitro motility assay experimentwith the same type of array geometry as in panel a before the additionof ATP. Focus is kept on the top of the nanowires. Actin filaments(bright fluorescent lines) are aligned with nanowire arrays beingattached to HMM on the tip of the nanowires. Strongly fluorescentspots on nanowires attributed to light-guiding from fluorescent actinfilaments interacting with the wires along their length. Occasionalfluorescent spots outside the array in panel b (arrows) are attributedto actin filaments attached to nanowires spuriously formed by parasiticgrowth (examples of such wires also indicated in panel a) and aretherefore in focus.
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fig2: Nanowire arrays. a, Scanning electron microscopy(SEM) image ofnanowires in 50 × 50 μm2 array with 1 μminterwire distance and 5 μm nanowire length. Close up view ininset. b, Fluorescence micrograph from in vitro motility assay experimentwith the same type of array geometry as in panel a before the additionof ATP. Focus is kept on the top of the nanowires. Actin filaments(bright fluorescent lines) are aligned with nanowire arrays beingattached to HMM on the tip of the nanowires. Strongly fluorescentspots on nanowires attributed to light-guiding from fluorescent actinfilaments interacting with the wires along their length. Occasionalfluorescent spots outside the array in panel b (arrows) are attributedto actin filaments attached to nanowires spuriously formed by parasiticgrowth (examples of such wires also indicated in panel a) and aretherefore in focus.
Mentions: We chose GaP as our material system becauseof the established biocompatibility of GaP nanowires21 and the generally advantageous optical properties of theIII–V semiconductor materials.3,12,13 Nanowires were produced by gold-particle-seeded metalorganic vapor phase epitaxy (MOVPE)22 (Figures 1a and S1). Because nanowiregrowth is initialized by GaP assembly at the interface of the substrateto the gold particle, the wire size and array geometry (Figures 1a and 2a) can be definedby electron beam lithography (EBL)-defined gold patterning. The useof regular nanowire spacing enables the growth of arrays with uniformwire length. After testing several surface derivatization procedures(see Supporting Information, results section)with respect to actomyosin motility quality (speed and fraction ofmobile actin filaments) we chose atomic layer deposition of Al2O3 on nanowires (Figure 1a) and surrounding areas, creating suitable surface contact anglesfor motility23 without the need for priorsilanization. Together with the GaP nanowire core diameter (30–50nm in different arrays), the 60 nm of Al2O3 coatingresulted in a total nanowire diameter of 150–171 nm (∼160nm unless otherwise stated). The wire length was either 0.96 ±0.03 or 5 ± 0.2 μm (mean ± standard deviation) indifferent arrays. In vitro motility studies were performed14 by infusing HMM (120 μg/mL) into flowcells formed by a chip with nanowire arrays (Figure 1) as the ceiling and a coverslip as the floor. Irrespectiveof the actual geometry, “top” and “bottom”in the text below are defined as indicated in Figure 1b. The HMM-induced sliding of Alexa Fluor 488 phalloidin labeledactin filaments was observed after infusion of assay solution (1 mMMgATP; 22–25 °C). The filaments were observed using epi-fluorescencemicroscopy. We used a Nikon Eclipse TE300 inverted microscope withHg-lamp illumination, Nikon 100 × 1.4 NA oil immersion objective,FITC filter set [excitation, 465–495 nm; dichroic mirror cutoff,505 nm; emission barrier filter, 515–555 nm] and a HammamatsuEMCCD camera. Further details of the experimental methods are givenin the Supporting Information, methodssection, e.g., quantitative analysis of the motility quality of filamentsmoving up and down wires (Supporting Figures S2–S3).

Bottom Line: This enables effective collection of light emitted by fluorescent analytes located at different focal planes along the nanowire.We unequivocally demonstrate the light-guiding effect using a novel method whereby the changes in emitted fluorescence intensity are observed when fluorescent cytoskeletal filaments are propelled by molecular motors along the wires.The findings are discussed in relation to nanobiosensor developments, other nanotechnological applications, and fundamental studies of motor function.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry and Biomedical Sciences, Linnaeus University , SE-391 82 Kalmar, Sweden.

ABSTRACT
Semiconductor nanowire arrays offer significant potential for biosensing applications with optical read-out due to their high surface area and due to the unique optical properties of one-dimensional materials. A challenge for optical read-out of analyte-binding to the nanowires is the need to efficiently collect and detect light from a three-dimensional volume. Here we show that light from fluorophores attached along several μm long vertical Al2O3 coated gallium phosphide nanowires couples into the wires, is guided along them and emitted at the tip. This enables effective collection of light emitted by fluorescent analytes located at different focal planes along the nanowire. We unequivocally demonstrate the light-guiding effect using a novel method whereby the changes in emitted fluorescence intensity are observed when fluorescent cytoskeletal filaments are propelled by molecular motors along the wires. The findings are discussed in relation to nanobiosensor developments, other nanotechnological applications, and fundamental studies of motor function.

No MeSH data available.


Related in: MedlinePlus