Seminarios y Eventos

Seminars and Events

Jornadas Jóvenes Investigadores


Coordinadores: Iñigo Bretos y Lidia Martínez


04 November 2019, 12:30 h. Salón de Actos

Cantilever dynamics in high-speed AFM single-molecule force spectroscopy

Manuel Ralph Uhlig


AFM Force spectroscopy is enhancing our understanding of single-molecule, single-cell, and nanoscale biophysical and mechanical properties [1-3]. The well-known Hooke’s law postulates the proportionality between the interaction force and the instantaneous probe deflection. By studying the probe dynamics through numerical simulations [4], we demonstrated that the total force has two additional contributions: the hydrodynamic one (tip speed – dependent) and the inertial one (acceleration – dependent). The amplitudes of these Newton dynamics contributions depend on the ratio between the pulling speed at which the interaction is measured and the resonance frequency of the cantilever. Neglecting these additional forces requires the use of low frequency ratios χ, imposing a high-speed limit up to which forces can be accurately quantified.
In this talk, we will show AFM single-molecule force spectroscopy measurements (SMFS) performed on the well-characterized Avidin-Biotin system. At high frequency ratios (χ above 10), we demonstrate the underestimation of the unbinding forces in comparison with the Bell-Evans prediction. We develop an equation to incorporate the Newton dynamics effects into the Bell-Evans theory. We provide a correction factor for the measured forces. This allows to perform faithful AFM SMFS at every rate and, hence, to extract the kinetic parameters of the dissociation process.

[1] E. L. Florin, V. T. Moy, H. E. Gaub, Science 264, 415−417 (1994)
[2] P. Hinterdorfer et al., PNAS 93, 3477−3481 (1996)
[3] D. Alsteens et al., Nat. Nanotech.12, 177-183 (2017)
[4] C. A. Amo, R. Garcia, ACS Nano 10, 7117−7124 (2016)


04 November 2019, 12:00 h. Salón de Actos

Mapping nanomechanical properties of proteins and polymers with bimodal AFM

Simone Benaglia


Fast, high-resolution mapping of the viscoelastic properties of soft matters, represents a major goal of atomic force microscopy (AFM) [1]. Bimodal AM-FM AFM is a suitable method for this purpose, since it allows the simultaneous acquisition of nanomechanical properties without losing in resolution and acquisition speed. This multifrequency configuration combines the robustness and simplicity of an amplitude modulation (AM) feedback in the first mode, with the sensitivity and a high signal-to-noise ratio of a frequency modulation (FM) feedback in the second mode. Finally, through the use of the appropriate contact mechanics model, it is possible to determine elastic and viscous properties of the analyzed sample [2].
Here we show how bimodal AM-FM is applied to extract the elastic properties of soft samples, such as proteins and polymers. Specifically, we characterize the elastic properties of a single protein in liquid, the 20S proteasome which in living organism plays a proteolytic role [3], and the viscoelastic properties of a polymeric assembly, a poly(styrene-block-methylmethacrylate) (PS-b-PMMA) copolymer sample [4].

[1] C. A. Amo, A. P. Perrino, A. F. Payam, and R. Garcia, ACS Nano 11, 8650 (2017).
[2] E. T. Herruzo, A. P. Perrino, and R. Garcia, Nat. Commun. 5, 3126 (2014).
[3] S. Benaglia, V. G. Gisbert, A.P. Perrino, C. A. Amo R. Garcia, Nat. Protoc. 13, 2890 (2018).
[4] S. Benaglia, C. A. Amo, R. Garcia, Nanoscale 11, 15289–15297 (2019).


14 October 2019, 12:00 h. Salón de Actos

Biomimetic engineering of nanofibers for tissue regeneration

André Girão
Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC)


Biomimetics has recently emerged as a pivotal concept in regenerative medicine, particularly in tissue engineering (TE) applications, since it is consistently boosting the development of advanced healthcare platforms - scaffolds - able to recreate specific natural biological processes towards the regeneration of damaged tissues. As the repair of each cellular microenvironment presents different challenges after injury, it is indispensable that the scaffold could provide an architecture and chemical composition similar to the healthy tissue. In fact, such resemblance with the endogenous extracellular matrix (ECM) should lead to the generation of cell-material interactions capable of accurately inducing a cell behaviour proficient to enhance anatomical and functional recovery. Following this trend, biocompatible systems composed by nanofibers are continuously being explored as candidates for mimicking the arrangement and fibrillar configuration of the ECM components, even though there is a current scarcity of design and fabrication methodologies appropriate to construct complex 3D fibrous architectures. Therefore, this talk will briefly cover promising scaffolding strategies that not only suggest possible routes to build hierarchical organized nanofibrous networks, but also explore the potential of graphene-based materials to induce complementary biochemical and biomechanical cues suitable to upgrade the bioactivity of such TE scaffolds.


14 October 2019, 12:30 h. Salón de Actos

Nanopartículas magneto-plasmónicas como plataformas de detección y tratamiento de células cancerígenas

Dr. Jesús García Ovejero
Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC)


La combinación de propiedades ópticas como los plasmones de superficie con propiedades magnéticas ha abierto un nuevo campo de exploración en la ciencia de materiales. La posibilidad de crear nanoestructuras biocompatibles que combinen estas dos respuestas permite desarrollar nanoagentes multifuncionales para aplicaciones como la detección y el tratamiento de células cancerígenas.
Las nanoestructuras desarrolladas en este estudio, combinan nanocilindros de Au y nanoesferas de óxido de Fe embebidas en una matriz de silice que actúa como espaciador entre fases. El ajuste de la geometría de los cilindros de oro así como el típo de ferrita escogido ofrecen una gran versatilidad en el diseño de las propiedades plasmónicas y magneticas de sus componentes. Sin embargo, resulta crucial analizar los efectos de interacción entre las fases tras su hibridación, ya que la respuesta magneto-plasmónica global pueden verse significativamente modificada. En este aspecto, la matriz de sílice juega un papel fundamental como atenuador de posibles interferencias.
Para poder hacer uso de estas nanoestructuras en el ambito biomédico existe además un número de condiciones que deben cumplir: una alta estabilidad coloidal, una baja interacción con proteinas séricas, un tamaño hidrodinámico de <200 nm, etc. Por este motivo, las nanoestructuras desarrolladas fueron funcionalizadas con un glicopolímero de baja electronegatividad que favorce su estabilidad coloidal tanto en medio acuoso como en serum de proteinas bovinas.
Las estructuras desarolladas demostraron su potencial como agentes de acumulación magnética para la detección fotoacustica de células tumorales circulantes y como agentes de hipertermia óptica y magnética.


   

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