Measuring the mass, density, and size of particles and cells using a suspended microchannel resonator

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205

Recent advances in coherent x-ray diffractive imaging have paved the way to reliable and quantitative imaging of noncompact specimens at the nanometer scale. Introduced a year ago, an advanced implementation of ptychographic coherent diffractive imaging has removed much of the previous limitations regarding sample preparation and illumination conditions. Here, we apply this recent approach toward structure determination at the nanoscale to biological microscopy. We show that the projected electron density of unstained and unsliced freeze-dried cells of the bacterium Deinococcus radiodurans can be derived from the reconstructed phase in a straightforward and reproducible way, with quantified and small errors. Thus, the approach may contribute in the future to the understanding of the highly disputed nucleoid structure of bacterial cells. In the present study, the estimated resolution for the cells was 85 nm (half-period length), whereas 50-nm resolution was demonstrated for lithographic test structures. With respect to the diameter of the pinhole used to illuminate the samples, a superresolution of about 15 was achieved for the cells and 30 for the test structures, respectively. These values should be assessed in view of the low dose applied on the order of ≃1.3 · 10 5 Gy, and were shown to scale with photon fluence.bacterial nucleoid | cellular imaging | coherent x-ray diffractive imaging | x-ray microscopy

Section: Resultsmentioning

confidence: 99%

Quantitative biological imaging by ptychographic x-ray diffraction microscopy

Giewekemeyer

Thibault²,

Kalbfleisch³

et al. 2009

242

205

“…The cantilever oscillates at a frequency that is proportional to its mass, and a cell passing through the embedded channel changes the resonance frequency of the cantilever by an amount proportional to the buoyant mass of the cell. Previous work with the SMR showed that the average density of a population of cells can be calculated from buoyant mass measurements (10,11) and that yeast exhibit cell cycle-dependent variations in average cell density (11), but these methods cannot measure the density of single cells or derive statistics about the density distribution.…”

mentioning

confidence: 99%

Measuring single-cell density

Grover

Bryan

Diez-Silva

et al. 2011

Self Cite

301

268

We have used a microfluidic mass sensor to measure the density of single living cells. By weighing each cell in two fluids of different densities, our technique measures the single-cell mass, volume, and density of approximately 500 cells per hour with a density precision of 0.001 g mL −1 . We observe that the intrinsic cell-to-cell variation in density is nearly 100-fold smaller than the mass or volume variation. As a result, we can measure changes in cell density indicative of cellular processes that would be otherwise undetectable by mass or volume measurements. Here, we demonstrate this with four examples: identifying Plasmodium falciparum malariainfected erythrocytes in a culture, distinguishing transfused blood cells from a patient's own blood, identifying irreversibly sickled cells in a sickle cell patient, and identifying leukemia cells in the early stages of responding to a drug treatment. These demonstrations suggest that the ability to measure single-cell density will provide valuable insights into cell state for a wide range of biological processes.cell size | apoptosis | hematology | biosensor | suspended microchannel resonator

“…We measured density in two ways with the SMR. The first provides an alternative to density gradient centrifugation and population-based approaches described previously (13) by measuring buoyant mass with the SMR and, on the same sample, volume with a commercial Coulter counter. Unlike density gradient centrifugation, this technique provides buoyant mass and volume information, measures growth-arrested cells in almost any medium, and does not require density gradient chemicals.…”

mentioning

confidence: 99%

Measurement of mass, density, and volume during the cell cycle of yeast

Bryan

Goranov²,

Amon³

et al. 2009

Self Cite

246

190

Cell growth comprises changes in both mass and volume-two processes that are distinct, yet coordinated through the cell cycle. Understanding this relationship requires a means for measuring each of the cell's three basic physical parameters: mass, volume, and the ratio of the two, density. The suspended microchannel resonator weighs single cells with a precision in mass of 0.1% for yeast. Here we use the suspended microchannel resonator with a Coulter counter to measure the mass, volume, and density of budding yeast cells through the cell cycle. We observe that cell density increases prior to bud formation at the G1/S transition, which is consistent with previous measurements using density gradient centrifugation. To investigate the origin of this density increase, we monitor relative density changes of growing yeast cells. We find that the density increase requires energy, function of the protein synthesis regulator target of rapamycin, passage through START (commitment to cell division), and an intact actin cytoskeleton. Although we focus on basic cell cycle questions in yeast, our techniques are suitable for most nonadherent cells and subcellular particles to characterize cell growth in a variety of applications.biosensor | cell growth | cell size | microfluidics | Saccharomyces