Suchergebnisse

Most of the cancer deaths could be avoided by early detection of the tumor when it is confined to its primary site and it has not metastasized. To this aim, one of the most promising strategies is the discovery and detection of protein biomarkers shed by the young tumor to the bloodstream. Proteomic technologies, mainly mass spectrometry and multiplexed immunoassays, have rapidly developed during last years with improved limits of detection and multiplexing capability. Unfortunately, these developments together major investments and large international efforts have not resulted into new useful protein biomarkers. Here, we analyze the potential and limitations of current proteomic technologies for detecting protein biomarkers released into circulation by the tumor. We find that these technologies can hardly probe the deepest region of the plasma proteome, at concentrations below the pg/mL level, where protein biomarkers for early cancer detection may exist. This clearly indicates the need of incorporating novel ultrasensitive techniques to the proteomic tool-box that can cover the inaccessible regions of the plasma proteome. We here propose biological detectors based on nanomechanical systems for discovery and detection of cancer protein biomarkers in plasma. We review the modes of operation of these devices, putting our focus on recent developments on nanomechanical sandwich immunoassays and nanomechanical spectrometry. The first technique enables reproducible immunodetection of proteins at concentrations well below the pg/mL level, with a limit of detection on the verge of 10 ag/mL. This technology can potentially detect low abundance tumor-associated proteins in plasma at the very early stages of the tumor. The second technique enables the identification of individual intact proteins by two physical coordinates, the mass and stiffness, instead of the mass-to-charge ratio of the protein constituents. This technology enormously simplifies the identification of proteins and it can provide useful information on interactions and posttranslational modifications, that otherwise is lost in mass spectrometry. ; This study has been supported by European Union' s Horizon 2020 research and innovation programme under grant agreement No 731868 − VIRUSCAN; Spanish Ministry of Economy and Competitiveness (grant MAT2015-66904-R) and Spanish Association against Cancer (AECC) Scientific Foundation (grant PS15153089TAMA

A sensor device based on a single polymer cantilever and optical readout has been developed for detection of molecular recognition reactions without the need of a reference cantilever for subtraction of unspecific signals. Microcantilevers have been fabricated in the photoresist SU-8 with one surface passivated with a thin fluorocarbon layer. The SU-8 surface is sensitized with biological receptors by applying silanization methods, whereas the fluorocarbon surface remains inert to these processes. The thermal and mechanical properties of the chosen materials allow overcoming the main limitations of gold-coated silicon cantilevers: the temperature, pH, and ionic strength cross sensitivities. This is demonstrated by comparing the response of SU-8 cantilevers and that of gold-coated silicon nitride cantilevers to variations in temperature and pH. The sensitivity of the developed polymeric nanomechanical sensor is demonstrated by real-time detection of the human growth hormone with sensitivity in differential surface stress of about 1 mN/m. ; The authors acknowledge J. M. Rodríguez-Prado and M. Mellado for providing reagents for the molecular recognition experiments and J. Treviño, E. Mauriz, and D. Haefliger for fruitful discussion. J.T. and M.C. acknowledge financial support from the Spanish Ministry of Science (MERG-CT-2004- 510638) and the European Union (GEN2001-4856-C13-11). ; Peer reviewed

In this work we study the different phenomena taking place when a hydrostatic pressure is applied in the inner fluid of a suspended microchannel resonator. Additionally to pressure-induced stiffness terms, we have theoretically predicted and experimentally demonstrated that the pressure also induces mass effects which depend on both the applied pressure and the fluid properties. We have used these phenomena to characterize the frequency response of the device as a function of the fluid compressibility and molecular masses of different fluids ranging from liquids to gases. The proposed device in this work can measure the mass density of an unknown liquid sample with a resolution of 0.7 µg/mL and perform gas mixtures characterization by measuring its average molecular mass with a resolution of 0.01 atomic mass units ; This work was supported by the European Union's Horizon 2020 research and innovation program under European Research Council grant 681275-LIQUIDMASS-ERC-CoG-2015 and the Spanish Science Ministry (MINECO) through project MOMPs TEC2017-89765-R. The service from the Micro and Nanofabrication Laboratory (MiNa) and X-SEM Laboratory, is funded by MCIU (CSIC13-4E-1794) and EU (FEDER, FSE). ; Peer reviewed

Trabajo presentado en la 20th International Conference on Solid-State Sensors, Actuators and Microsystems & Eurosensors XXXIII (TRANSDUCERS & EUROSENSORS XXXIII), celebrada en Berlín (Alemania), del 23 al 27 de junio de 2019 ; Hollow nanomechanical resonators represent a promising technique for particle spectrometry, as their design allows highly sensitive particle mass sensing in liquid environments by putting together the good mechanical behavior of a nanomechanical resonator vibrating in vacuum or gas environment with physiological compatibility of liquid environments for biological applications. Nevertheless, for real-world practical applications these sensors require not only a high mass sensitivity but also a high-throughput particle flow. In this work, we use a fast-response and low-cost hollow nanomechanical resonator which let us measure up to 10 particles per second. However, this unprecedented particle velocities brings new implications related to the entanglement between the mechanics and the microfluidics in this structure. We realized that the measured particle masses depend on the fluid velocity. The study of this phenomenon demonstrates the need to introduce a correction factor in mass sensing dependent on particle velocity. ; This work was supported by the European Union's Horizon 2020 program under European Research Council grant 681275 – LIQUIDMASS- ERC- CoG-2015 and by the Comunidad de Madrid (iLUNG B2017/BMD-3884) - co-funded by FSE & FEDER and the Spanish Science Ministry(MINECO) through project TEC2017-89765-R. All authors acknowledge the service from the X-SEM Laboratory at IMN and MINECO under project CSIC13- 4E-1794, also with support from EU (FEDER, FSE). All the authors also acknowledge the service from the MiNa Laboratory at IMN, and funding from CM (project SpaceTec, S2013/ICE2822), MINECO (project CSIC13- 4E-1794) and EU (FEDER, FSE). ; Peer reviewed

Characterization of micro and nanoparticle mass has become increasingly relevant in a wide range of fields, from materials science to drug development. The real-time analysis of complex mixtures in liquids demands very high mass sensitivity and high throughput. One of the most promising approaches for real-time measurements in liquid, with an excellent mass sensitivity, is the use of suspended microchannel resonators, where a carrier liquid containing the analytes flows through a nanomechanical resonator while tracking its resonance frequency shift. To this end, an extremely sensitive mechanical displacement technique is necessary. Here, we have developed an optomechanical transduction technique to enhance the mechanical displacement sensitivity of optically transparent hollow nanomechanical resonators. The capillaries have been fabricated by using a thermal stretching technique, which allows to accurately control the final dimensions of the device. We have experimentally demonstrated the light coupling into the fused silica capillary walls and how the evanescent light coming out from the silica interferes with the surrounding electromagnetic field distribution, a standing wave sustained by the incident laser and the reflected power from the substrate, modulating the reflectivity. The enhancement of the displacement sensitivity due to this interferometric modulation (two orders of magnitude better than compared with previous accomplishments) has been theoretically predicted and experimentally demonstrated. ; This work was supported by the European Union's Horizon 2020 program under European Research Council grant 681275—LIQUIDMASS-ERC-CoG-2015 and by the Comunidad de Madrid (iLUNG B2017/BMD-3884)—co-funded by FSE & FEDER and the Spanish Science Ministry (MINECO) through project MOMPs TEC2017-89765-R. All authors acknowledge the service from the X-SEM Laboratory at IMN and MINECO under project CSIC13-4E-1794, also with support from EU (FEDER, FSE).

In the last two decades, nano-mechanical resonators have risen as highly promising devices for mass sensing due to their ultrahigh sensitivity. They can be used to measure the mass and stiffness of single particles like small pollution particles, viruses, bacteria, or even proteins. These capabilities of the nano-mechanical resonators have allowed the birth of a new type of mass spectrometry with no need of fragmentation or ionization of the sample and therefore ideal to measure big masses, where conventional mass spectrometers have important problems. The shape and modes of vibration of a nano-mechanical resonator can be very different and the advantages and drawbacks of one respect to another is still a hot topic. A unified theoretical framework to describe the effect of particle adsorption on a mechanical resonator is fundamental but still lacks in the literature. In this work, we present such a framework and examine the particular case of a rod-like particle adsorbed on a cantilever beam for flexural and torsional vibrations as well as on a disk resonator for radial breathing vibrations and compare the results with finite element simulations ; This work was supported by the European Union's Horizon 2020 Research and Innovation Program under Grant Agreement No. 731868—VIRUSCAN. REFERENCES ; No

© 2021 by the authors. ; Over the last decades, nanomechanical sensors have received significant attention from the scientific community, as they find plenty of applications in many different research fields, ranging from fundamental physics to clinical diagnosis. Regarding biological applications, nanomechanical sensors have been used for characterizing biological entities, for detecting their presence, and for characterizing the forces and motion associated with fundamental biological processes, among many others. Thanks to the continuous advancement of micro- and nano-fabrication techniques, nanomechanical sensors have rapidly evolved towards more sensitive devices. At the same time, researchers have extensively worked on the development of theoretical models that enable one to access more, and more precise, information about the biological entities and/or biological processes of interest. This paper reviews the main theoretical models applied in this field. We first focus on the static mode, and then continue on to the dynamic one. Then, we center the attention on the theoretical models used when nanomechanical sensors are applied in liquids, the natural environment of biology. Theory is essential to properly unravel the nanomechanical sensors signals, as well as to optimize their designs. It provides access to the basic principles that govern nanomechanical sensors applications, along with their intrinsic capabilities, sensitivities, and fundamental limits of detection. ; This research was funded by the European Union's Horizon 2020 research and innovation program under grant agreement no. 731868—VIRUSCAN. ; Peer reviewed

7 pages, 5 figures, 1 table. ; Thermomechanical noise determines the lowest detection limits of microcantilever-based devices for measuring forces and surface stress variations. In this work, arrays of 334-nm-thick single-crystalline silicon microcantilevers with dissimilar lengths and widths from 50 to 500 µm and 20 to 200 µm, respectively, have been fabricated to calculate the minimal detectable force and surface stress on the basis of the measurement of the spring constant, resonance frequency, and quality factor. The calculated minimal detectable force and surface stress are of the orders of 10–15 N Hz–1/2 and 10–7 N m–1 Hz–1/2, respectively, and both follow a nonintuitive dependence on the dimensions. The minimal detectable force decreases as the cantilevers are shorter and narrower, whereas the minimal detectable surface stress decreases by making the cantilevers shorter and wider. Theoretical expressions of the minimal detectable force and surface stress are provided as a function of the material properties, cantilever dimensions, and quality factor, which allow us to interpret the results. Both force and surface stress noises follow the same dependence on the quality factor and material properties, however, exhibit striking differences in the dimension dependences. The force and surface stress noises enhance with the quality factor. If the quality factor is kept constant, the force noise enhances as the cantilever is longer and wider, whereas the surface stress noise enhances by making the cantilever shorter and wider. The observed increase of the force noise with the length is attributed to the strong decrease of the quality factor. The results imply that the design of cantilevers for surface stress measurements in general should be different than for atomic force microscopy probes. ; The authors would like to acknowledge the European Union (IST-2001-37239) and the Spanish Ministry of Science (GEN2001-4856-C13-11 and TIC2002-10473-E) for the financial support. ; Peer reviewed

3 pages, 4 figures. ; We have grown self-organized InSb quantum dots on semi-insulating InP (001) substrates by molecular beam epitaxy. We studied the size dependency of the uncapped InSb quantum dots on the nominal thickness of the deposited InSb by atomic force microscopy. The dot sizes have a pronounced minimum at about 2.2 monolayers of InSb. After a nominal thickness of 3.2 monolayers we observe a drastic change of the dot shape, from quantum dots to quantum dashes. From there on the dots grow in a quasicylindric shape aligned in the (110) direction. ; The authors would like to acknowledge gratefully financial support from the European Union (HCM, Network CT930349). ; Peer reviewed

Tumorigenesis induces actin cortex remodeling, which makes cancerous cells softer. Cell deformability is largely determined by myosin-driven cortical tension and actin fiber architecture at the cell cortex. However, it is still unclear what the weight of each contribution is, and how these contributions change during cancer development. Moreover, little attention has been paid to the effect of energy metabolism on this phenomenon and its reprogramming in cancer. Here, we perform precise two-dimensional mechanical phenotyping based on power-law rheology to unveil the contributions of myosin II, actin fiber architecture and energy metabolism to the deformability of healthy (MCF-10A), noninvasive cancerous (MCF-7), and metastatic (MDA-MB-231) human breast epithelial cells. Contrary to the perception that the actin cortex is a passive structure that provides mechanical resistance to the cell, we find that this is only true when the actin cortex is activated by metabolic processes. The results show marked differences in the nature of the active processes that build up cell stiffness, namely that healthy cells use ATP-driven actin polymerization whereas metastatic cells use myosin II activity. Noninvasive cancerous cells exhibit an anomalous behavior, as their stiffness is not as affected by the lack of nutrients and ATP, suggesting that energy metabolism reprogramming is used to sustain active processes at the actin cortex. ; This work was supported by the European Union's Horizon 2020 research and innovation program under European Research Council Grant 681275-LIQUIDMASS-ERCCoG-2015, under Grant Agreement No. 731868 – VIRUSCAN and by the Spanish Science, Innovation and Universities Ministry through project CELLTANGLE reference RTI2018-099369-B-I00; by the Comunidad de Madrid (iLUNG B2017/BMD-3884) with support from EU (FEDER, FSE) and Ramón y Cajal grant RYC-2017-21640 to P.M.K. The service from the X-SEM Laboratory is funded by MCIU (CSIC13-4E-1794) and EU (FEDER, FSE).

Ultrasensitive physical, chemical and biological sensors have emerged in the last decade based on the measurement of the eigenfrequencies of micro- and nanosized cantilever plates. Surface stress is omnipresent in these devices due to a variety of factors such as the fabrication process, temperature variations and analyte adsorption. How surface stress influences on the eigenfrequencies of cantilever plates has remained as an unsolved question in physics that has raised a long debate since first experiments in 1975. Recent theoretical models have shed light on the role of the net surface stress. Still, there exists a discrepancy between theory and some experimental reports, affecting to the capability for quantification of these sensors. In this Letter, we present a theoretical framework that demonstrates that the cantilever bending due to differential surface stress between opposite faces of the cantilever, a neglected effect in classical beam theory, plays a relevant role in the stiffness and eigenfrequencies of cantilevers. We develop a new theoretical framework that provides analytical equations that accurately describe the effect of surface stress on the first three vibration modes of cantilevers. Our findings provide the final piece of the puzzle for solving this long-standing problem in physics ; This study has been supported by European Union' s Horizon 2020 research and innovation programme under grant agreement No 731868 – VIRUSCAN and European Research Council grant 681275 – LIQUIDMASS- ERC- CoG-2015; by Spanish Ministry of Economy and Competitiveness (grant MAT2015-66904-R). PMK acknowledges financial support by Fundación General CSIC (ComFuturo Program) ; Peer reviewed

Carbapenem-resistant Enterobacteriaceae have recently become an important cause of morbidity and mortality due to healthcare-associated infections. Most commonly used diagnostic methods are incompatible with fast and accurate directed therapy. We report here the direct identification of the blaOXA48 gene, which codes for the carbapenemase OXA-48, in lysate samples from Klebsiella pneumoniae. The method is PCR-free and label-free. It is based on the measurement of changes in the stiffness of DNA self-assembled monolayers anchored to microcantilevers that occur as a consequence of the hybridization. The stiffness of the DNA layer is measured through changes of the sensor resonance frequency upon hybridization and at varying relative humidity. ; This work was supported by the Spanish Science Ministry (MINECO) through project MAT2015-66904-R and by European Research Council through NANOFORCELLS project (ERC-StG-2011-278860) and European Union's Horizon 2020 research and innovation program under grant agreement No. 731868-VIRUSCAN. D.R. acknowledges the Ramon y Cajal fellowship supported by Spanish Ministry MINECO. Authors also acknowledge the service from the XSEM Laboratory at IMN and funding from MINECO under project CSIC13-4E-1794 with support from EU (FEDER, FSE). ; Peer reviewed

There is a need for noninvasive techniques for simultaneous imaging of the stress and vibration mode shapes of nanomechanical systems in the fields of scanning probe microscopy, nanomechanical biological and chemical sensors and the semiconductor industry. Here we show a novel technique that combines a scanning laser, the beam deflection method and digital multifrequency excitation and analysis for simultaneous imaging of the static out-of-plane displacement and the shape of five vibration modes of nanomechanical systems. The out-of-plane resolution is at least 100 pm Hz−1/2 and the lateral resolution, which is determined by the laser spot size, is 1–1.5 μm. The capability of the technique is demonstrated by imaging the residual surface stress of a microcantilever together with the shape of the first 22 vibration modes. The vibration behavior is compared with rigorous finite element simulations. The technique is suitable for major improvements in the imaging of liquids, such as higher bandwidth and enhanced spatial resolution. ; The authors acknowledge financial support from the Spanish Science Ministry through the projects ANEM! (TEC2009-14517-C02) and INMUNO-swing (IPT-2011-0821-010000), and from the European Union through the project NANOFORCELLS (ERC-StG-2011-278860). ; Peer reviewed

The properties of water at the nanoscale are crucial in many areas of biology, but the confinement of water molecules in sub-nanometre channels in biological systems has received relatively little attention. Advances in nanotechnology make it possible to explore the role played by water molecules in living systems, potentially leading to the development of ultrasensitive biosensors. Here we show that the adsorption of water by a self-assembled monolayer of single-stranded DNA on a silicon microcantilever can be detected by measuring how the tension in the monolayer changes as a result of hydration. Our approach relies on the microcantilever bending by an amount that depends on the tension in the monolayer. In particular, we find that the tension changes dramatically when the monolayer interacts with either complementary or single mismatched single-stranded DNA targets. Our results suggest that the tension is mainly governed by hydration forces in the channels between the DNA molecules and could lead to the development of a label-free DNA biosensor that can detect single mutations. The technique provides sensitivity in the femtomolar range that is at least two orders of magnitude better than that obtained previously with label-free nanomechanical biosensors and with label-dependent microarrays. ; D.R. acknowledges the fellowship funded by the Autonomic Community of Madrid (CAM). J.T, M.C, J.M and D.R acknowledge financial support by Spanish Ministry of Science (MEC) under grant No. TEC2006-10316 and CAM under grant No. 200550M056. C.B. acknowledges funding provided by MEC under grant No. BIO2007-67523. Work at Centro de Astrobiología was supported by European Union (EU), Instituto Nacional de Técnica Aeroespacial (INTA), MEC and CAM. All the authors acknowledge A. Cebollada, J.M. García-Martín, J. García, J.L. Costa-Kramer, M. Arroyo-Hernández and J.V. Anguita for their assistance in the gold deposition on the cantilevers. ; Peer reviewed

The real-time analysis of single analytes in flow is becoming increasingly relevant in cell biology. In this work, we theoretically predict and experimentally demonstrate hydrodynamic focusing with hollow nanomechanical resonators by using an interferometric system which allows the optical probing of flowing particles and tracking of the fundamental mechanical mode of the resonator. We have characterized the hydrodynamic forces acting on the particles, which will determine their velocity depending on their diameter. By using the parameters simultaneously acquired: frequency shift, velocity and reflectivity, we can unambiguously classify flowing particles in real-time, allowing the measurement of the mass density: 1.35 ± 0.07 g·mL-1 for PMMA and 1.7 ± 0.2 g·mL-1 for silica particles, which perfectly agrees with the nominal values. Once we have tested our technique, MCF-7 human breast adenocarcinoma cells are characterized (1.11 ± 0.08 g·mL-1) with high throughput (300 cells/minute) observing a dependency with their size, opening the door for individual cell cycle studies. ; This work was supported by the European Union's Horizon 2020 research and innovation program under European Research Council Grant 681275-LIQUIDMASS-ERC-CoG-2015, project CELLTANGLE reference RTI2018-099369-B-I00, project MOMPs reference TEC2017-89765-R, Asociación Elena Torres (contract OTR04893) and FERO Foundation (Grant OTR06145). The service from the Micro and Nanofabrication Laboratory (MiNa) and X-SEM Laboratory, is funded by MCIU (CSIC13-4E-1794) and EU (FEDER, FSE). ; Peer reviewed