Precision mass measurements in solution reveal properties of single cells and bioparticles

Precise characterization of biological materials ranging from single cells (~1-20 microns) to extracellular vesicles (20-200 nm) is of fundamental interest because of their biological and translational value. Here we discuss the value of precision mass measurements in solution for informing various physical and biological parameters, such as mass accumulation rate, longitudinal cell growth or cell density. We introduce how the limits of the single-particle mass measurements can be pushed down to nano-scale dimensions enabling the resolution of extracellular vesicles and viruses in solution. We believe with future advancements on the precision and throughput of this approach, the capability of analyzing biologically relevant particles in solution will have broad biological and translational impact

High-speed multiple-mode mass-sensing resolves dynamic nanoscale mass distributions

Simultaneously measuring multiple eigenmode frequencies of nanomechanical resonators can determine the position and mass of surface-adsorbed proteins, and could ultimately reveal the mass tomography of nanoscale analytes. However, existing measurement techniques are slow (<1 Hz bandwidth), limiting throughput and preventing use with resonators generating fast transient signals. Here we develop a general platform for independently and simultaneously oscillating multiple modes of mechanical resonators, enabling frequency measurements that can precisely track fast transient signals within a user-defined bandwidth that exceeds 500 Hz. We use this enhanced bandwidth to resolve signals from multiple nanoparticles flowing simultaneously through a suspended nanochannel resonator and show that four resonant modes are sufficient for determining their individual position and mass with an accuracy near 150 nm and 40 attograms throughout their 150-ms transit. We envision that our method can be readily extended to other systems to increase bandwidth, number of modes, or number of resonators.United States. Army Research Office (Grant W911NF-09-0001)Center for Integration of Medicine and Innovative Technology (Contract 09-440)National Science Foundation (U.S.) (Grant 1129359

The measurement of Navier slip on individual nanoparticles in liquid

The Navier slip condition describes the motion of a liquid, relative to a neighboring solid surface, with its characteristic Navier slip length being a constitutive property of the solid-liquid interface. Measurement of this slip length is complicated by its small magnitude, expected in the nanometer range based on molecular simulations. Here, we report an experimental technique that interrogates the Navier slip length on individual nanoparticles immersed in liquid, with sub-nanometer precision. Proof-of-principle experiments on individual, citrate-stabilized, gold nanoparticles in water give a constant slip length of 2.7$\pm$0.6 nm (95% C.I.) - independent of particle size. Achieving this feature of size independence is central to any measurement of this constitutive property, which is facilitated through the use of individual particles of varying radii. This demonstration motivates studies that can now validate the wealth of existing molecular simulation data on slip.Comment: 12 pages, 4 figure

Suspended nanochannel resonators at attogram precision

Nanomechanical resonators can quantify individual particles down to a single atom; however the applications are limited due to their degraded performance in solution. Suspended micro- and nanochannel resonators can achieve vacuum level performances for samples in solution since the target analyte flows through an integrated channel within the resonator. Here we report on a new generation suspended nanochannel resonator (SNR) that operates at approximately 2 MHz with quality factors between 10,000-20,000. The SNR is measured to have a mass sensitivity of 8.2 mHz/attogram. With an optimized oscillator system, we show that the resonator can be oscillated with a mass equivalent frequency stability of 0.85 attogram (4 parts-perbillion) at 1 kHz bandwidth, which is 1.8 times the calculated stability imposed by the thermal noise. We demonstrate the use of this mass resolution by quantifying the mass and concentration of nanoparticles down to 10 nm in solution

Determining therapeutic susceptibility in multiple myeloma by single-cell mass accumulation

Multiple myeloma (MM) has benefited from significant advancements in treatment that have improved outcomes and reduced morbidity. However, the disease remains incurable and is characterized by high rates of drug resistance and relapse. Consequently, methods to select the most efficacious therapy are of great interest. Here we utilize a functional assay to assess the ex vivo drug sensitivity of single multiple myeloma cells based on measuring their mass accumulation rate (MAR). We show that MAR accurately and rapidly defines therapeutic susceptibility across human multiple myeloma cell lines to a gamut of standard-of-care therapies. Finally, we demonstrate that our MAR assay, without the need for extended culture ex vivo, correctly defines the response of nine patients to standard-of-care drugs according to their clinical diagnoses. This data highlights the MAR assay in both research and clinical applications as a promising tool for predicting therapeutic response using clinical samples

Microfluidic active loading of single cells enables analysis of complex clinical specimens

A fundamental trade-off between flow rate and measurement precision limits performance of many single-cell detection strategies, especially for applications that require biophysical measurements from living cells within complex and low-input samples. To address this, we introduce ‘active loading’, an automated, optically-triggered fluidic system that improves measurement throughput and robustness by controlling entry of individual cells into a measurement channel. We apply active loading to samples over a range of concentrations (1–1000 particles μL[superscript −1]), demonstrate that measurement time can be decreased by up to 20-fold, and show theoretically that performance of some types of existing single-cell microfluidic devices can be improved by implementing active loading. Finally, we demonstrate how active loading improves clinical feasibility for acute, single-cell drug sensitivity measurements by deploying it to a preclinical setting where we assess patient samples from normal brain, primary and metastatic brain cancers containing a complex, difficult-to-measure mixture of confounding biological debris.National Cancer Institute (U.S.) (R01 CA170592)National Cancer Institute (U.S.) (R33 CA191143)National Cancer Institute (U.S.) (Cancer Center Support (Core) Grant P30-CA14051)Bridge Projec

Microfluidic active loading of single cells enables analysis of complex clinical specimens

A fundamental trade-off between flow rate and measurement precision limits performance of many single-cell detection strategies, especially for applications that require biophysical measurements from living cells within complex and low-input samples. To address this, we introduce ‘active loading’, an automated, optically-triggered fluidic system that improves measurement throughput and robustness by controlling entry of individual cells into a measurement channel. We apply active loading to samples over a range of concentrations (1–1000 particles μL[superscript −1]), demonstrate that measurement time can be decreased by up to 20-fold, and show theoretically that performance of some types of existing single-cell microfluidic devices can be improved by implementing active loading. Finally, we demonstrate how active loading improves clinical feasibility for acute, single-cell drug sensitivity measurements by deploying it to a preclinical setting where we assess patient samples from normal brain, primary and metastatic brain cancers containing a complex, difficult-to-measure mixture of confounding biological debris.National Cancer Institute (U.S.) (R01 CA170592)National Cancer Institute (U.S.) (R33 CA191143)National Cancer Institute (U.S.) (Cancer Center Support (Core) Grant P30-CA14051)Bridge Projec

Drug sensitivity of single cancer cells is predicted by changes in mass accumulation rate

Assays that can determine the response of tumor cells to cancer therapeutics could greatly aid the selection of drug regimens for individual patients. However, the utility of current functional assays is limited, and predictive genetic biomarkers are available for only a small fraction of cancer therapies. We found that the single-cell mass accumulation rate (MAR), profiled over many hours with a suspended microchannel resonator, accurately defined the drug sensitivity or resistance of glioblastoma and B-cell acute lymphocytic leukemia cells. MAR revealed heterogeneity in drug sensitivity not only between different tumors, but also within individual tumors and tumor-derived cell lines. MAR measurement predicted drug response using samples as small as 25 μl of peripheral blood while maintaining cell viability and compatibility with downstream characterization. MAR measurement is a promising approach for directly assaying single-cell therapeutic responses and for identifying cellular subpopulations with phenotypic resistance in heterogeneous tumors.United States. National Institutes of Health (R01 CA170592)United States. National Institutes of Health (R33 CA191143)National Cancer Institute (U.S.) (U54 CA143874)United States. National Institutes of Health (NIH/NIGMS T32 GM008334

RETRATO EN EL PATIO [Material gráfico]

INCLUIDAS EN EL PEQUEÑO ÁLBUM FOTOGRÁFICO FAMILIAR DE LA COLECCIÓN LUIS SUÁREZ GALVÁNCopia digital. Madrid : Ministerio de Educación, Cultura y Deporte. Subdirección General de Coordinación Bibliotecaria, 201