11 research outputs found
3D correlative single-cell imaging utilizing fluorescence and refractive index tomography
Cells alter the path of light, a fact that leads to well-known aberrations in
single cell or tissue imaging. Optical diffraction tomography (ODT) measures
the biophysical property that causes these aberrations, the refractive index
(RI). ODT is complementary to fluorescence imaging and does not require any
markers. The present study introduces RI and fluorescence tomography with
optofluidic rotation (RAFTOR) of suspended cells, quantifying the intracellular
RI distribution and colocalizing it with fluorescence in 3D. The technique is
validated with cell phantoms and used to confirm a lower nuclear RI for HL60
cells. Furthermore, the nuclear inversion of adult mouse photoreceptor cells is
observed in the RI distribution. The applications shown confirm predictions of
previous studies and illustrate the potential of RAFTOR to improve our
understanding of cells and tissues.Comment: 15 pages, 5 figure
Single-cell diffraction tomography with optofluidic rotation about a tilted axis
Optical diffraction tomography (ODT) is a tomographic technique that can be
used to measure the three-dimensional (3D) refractive index distribution within
living cells without the requirement of any marker. In principle, ODT can be
regarded as a generalization of optical projection tomography which is
equivalent to computerized tomography (CT). Both optical tomographic techniques
require projection-phase images of cells measured at multiple angles. However,
the reconstruction of the 3D refractive index distribution post-measurement
differs for the two techniques. It is known that ODT yields better results than
projection tomography, because it takes into account diffraction of the imaging
light due to the refractive index structure of the sample. Here, we apply ODT
to biological cells in a microfluidic chip which combines optical trapping and
microfluidic flow to achieve an optofluidic single-cell rotation. In
particular, we address the problem that arises when the trapped cell is not
rotating about an axis perpendicular to the imaging plane, but instead about an
arbitrarily tilted axis. In this paper we show that the 3D reconstruction can
be improved by taking into account such a tilted rotational axis in the
reconstruction process.Comment: 7 pages, 3 figure
Accurate evaluation of size and refractive index for spherical objects in quantitative phase imaging
Measuring the average refractive index (RI) of spherical objects, such as
suspended cells, in quantitative phase imaging (QPI) requires a decoupling of
RI and size from the QPI data. This has been commonly achieved by determining
the object's radius with geometrical approaches, neglecting light-scattering.
Here, we present a novel QPI fitting algorithm that reliably uncouples the RI
using Mie theory and a semi-analytical, corrected Rytov approach. We assess the
range of validity of this algorithm in silico and experimentally investigate
various objects (oil and protein droplets, microgel beads, cells) and noise
conditions. In addition, we provide important practical cues for future studies
in cell biology.Comment: 14 pages, 10 figures, 1 tabl
Single-cell diffraction tomography with optofluidic rotation about a tilted axis
Optical diffraction tomography (ODT) is a tomographic technique that can be used to measure the threedimensional (3D) refractive index distribution within living cells without the requirement of any marker. In principle, ODT can be regarded as a generalization of optical projection tomography which is equivalent to computerized tomography (CT). Both optical tomographic techniques require projection-phase images of cells measured at multiple angles. However, the reconstruction of the 3D refractive index distribution post-measurement differs for the two techniques. It is known that ODT yields better results than projection tomography, because it takes into account diffraction of the imaging light due to the refractive index structure of the sample. Here, we apply ODT to biological cells in a micro uidic chip which combines optical trapping and microfluidic flow to achieve an optofluidic single-cell rotation. In particular, we address the problem that arises when the trapped cell is not rotating about an axis perpendicular to the imaging plane, but instead about an arbitrarily tilted axis. In this paper we show that the 3D reconstruction can be improved by taking into account such a tilted rotational axis in the reconstruction process
Dynamic operation of optical fibres beyond the single-mode regime facilitates the orientation of biological cells
The classical purpose of optical fibres is delivery of either optical power, as for welding, or temporal information, as for telecommunication. Maximum performance in both cases is provided by the use of single-mode optical fibres. However, transmitting spatial information, which necessitates higher-order modes, is difficult because their dispersion relation leads to dephasing and a deterioration of the intensity distribution with propagation distance. Here we consciously exploit the fundamental cause of the beam deterioration-the dispersion relation of the underlying vectorial electromagnetic modes-by their selective excitation using adaptive optics. This allows us to produce output beams of high modal purity, which are well defined in three dimensions. The output beam distribution is even robust against significant bending of the fibre. The utility of this approach is exemplified by the controlled rotational manipulation of live cells in a dual-beam fibre-optical trap integrated into a modular lab-on-chip system
New insights into the genetic etiology of Alzheimerâs disease and related dementias
Characterization of the genetic landscape of Alzheimerâs disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/âproxyâ AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE Δ4 allele