534 research outputs found
Recursive Least Squares Filtering Algorithms for On-Line Viscoelastic Characterization of Biosamples
The mechanical characterization of biological samples is a fundamental issue in biology
and related fields, such as tissue and cell mechanics, regenerative medicine and diagnosis of diseases.
In this paper, a novel approach for the identification of the stiffness and damping coefficients
of biosamples is introduced. According to the proposed method, a MEMS-based microgripper
in operational condition is used as a measurement tool. The mechanical model describing the
dynamics of the gripper-sample system considers the pseudo-rigid body model for the microgripper,
and the Kelvin–Voigt constitutive law of viscoelasticity for the sample. Then, two algorithms based
on recursive least square (RLS) methods are implemented for the estimation of the mechanical
coefficients, that are the forgetting factor based RLS and the normalised gradient based RLS
algorithms. Numerical simulations are performed to verify the effectiveness of the proposed approach.
Results confirm the feasibility of the method that enables the ability to perform simultaneously two
tasks: sample manipulation and parameters identification
Understanding poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogel as a multifunctional membrane in microfluidic cell culture platform
Cell culture technology developed at the turn of 20th century using Petri dish, which is not able to consider the microenvironment that the cells experience in vessels, has remained virtually unchanged for almost a century. However, such microenvironment associated with cell culture which usually consists of soluble factors, extracellular matrix cues, and cellular networks is difficult to reproduce experimentally with the traditional approach. In order to further elaborate complex mechanisms of cell biology through mimicking such microenvironment in vivo, the technical approaches together with developed microdevices are highly demanded within such a context. Microfluidic devices have been extensively developed and used for cell culture in the last two decades, which offer numerous advantages and a great potential for accurate and efficient control of the complex culturing microenvironment at cellular length scale. However, these devices are relatively complex in their fabrication and integration to fulfil multifunctional tasks for cell culture and drug testing simultaneously, which for example requires a membrane between the culture chamber and drug delivery reservoir to control microenvironment at cellular scale. This thesis is to primarily focus on the feasibility and reliability in the attempt of using poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogel as an inserted membrane, based on its permeable and flexible tissue-like properties. PHEMA membrane is able to serve dual purposes in the microfluidic systems in cell culture: i) exchanging nutrients between culture chamber and drug delivery reservoir; and ii) sealing the microchannel circuits.</div
Cell migration through 3D confining pores: speed accelerations by deformation and recoil of the nucleus
Directional cell migration in dense three-dimensional (3D) environments critically depends upon shape adaptation and is impeded depending on the size and rigidity of the nucleus. Accordingly, the nucleus is primarily understood as a physical obstacle, however, its pro-migratory functions by step-wise deformation and reshaping remain unclear. Using atomic force spectroscopy, timelapse fluorescence microscopy and shape change analysis tools, we determined nuclear size, deformability, morphology and shape change of HT1080 fibrosarcoma cells expressing the Fucci cell cycle indicator or being pre-treated with chromatin-decondensating agent TSA. We show oscillating peak accelerations during migration through 3D collagen matrices and microdevices that occur during shape reversion of deformed nuclei (recoil), and increase with confinement. During G1 cell cycle phase, nucleus stiffness was increased and yielded further increased speed fluctuations together with sustained cell migration rates in confinement as compared to interphase populations, or to periods of intrinsic nuclear softening in the S/G2 cell cycle phase. Likewise, nuclear softening by pharmacological chromatin decondensation or after lamin A/C depletion reduced peak oscillations in confinement. In conclusion, deformation and recoil of the stiff nucleus contributes to saltatory locomotion in dense tissues
Force Spectroscopy Imaging and Constriction Assays Reveal the Effects of Graphene Oxide on the Mechanical Properties of Alginate Microcapsules
Microencapsulation of cells in hydrogel-based porous matrices is an approach that has demonstrated great success in regenerative cell therapy. These microcapsules work by concealing the exogenous cells and materials in a robust biomaterial that prevents their recognition by the immune system. A vast number of formulations and additives are continuously being tested to optimize cell viability and mechanical properties of the hydrogel. Determining the effects of new microcapsule additives is a lengthy process that usually requires extensive in vitro and in vivo testing. In this paper, we developed a workflow using nanoindentation (i.e., indentation with a nanoprobe in an atomic force microscope) and a custom-built microfluidic constriction device to characterize the effect of graphene oxide (GO) on three microcapsule formulations. With our workflow, we determined that GO modifies the microcapsule stiffness and surface properties in a formulation-dependent manner. Our results also suggest, for the first time, that GO alters the conformation of the microcapsule hydrogel and its interaction with subsequent coatings. Overall, our workflow can infer the effects of new additives on microcapsule surfaces. Thus, our workflow can contribute to diminishing the time required for the validation of new microcapsule formulations and accelerate their clinical translation
Toward mass production of microtextured microdevices: linking rapid prototyping with microinjection molding
The possibility of manufacturing textured materials and devices, with surface properties controlled from the design stage, instead of being the result of machining processes
or chemical attacks, is a key factor for the incorporation of advanced functionalities to a wide set of micro and nanosystems. Recently developed high-precision additive manufacturing technologies, together with the use of fractal models linked to computer-aided design tools, allow for a precise definition and control of final surface properties for a wide set of applications, although the production of larger series based on these resources is still an unsolved challenge. However, rapid prototypes, with controlled surface topography, can be used as original masters for obtaining micromold inserts for final large-scale series manufacture of replicas using microinjection molding. In this study, an original procedure is presented, aimed at connecting rapid prototyping with microinjection molding, for the mass production of two different microtextured microsystems, linked to tissue engineering tasks, using different thermoplastics as ultimate materials
Analysis of methods for physical and biological characterization and validation of microphysiological systems (MPSs)
Microphysiological systems (MPSs), also known as 'Organ-On-a-Chip' (OCC), have revolutionized the way
of understanding biology. These systems, which include three-dimensional co-culture and microfluidic
technology, aim to mimic human physiology with in-vitro culture systems. Their purpose is to increase the
knowledge of biological processes, as well as to provide an effective diagnostic tool for the analysis of
different drugs.
Standardization of MPSs implies the robustness and reproducibility of these devices and is desirable for
their industrialization, production and regularization. However, due to the early stage of academic and
commercial development of this technology, no standardization procedure exists in the literature to date.
Therefore, experts recommend focusing on the characterization or qualification of these devices. This
characterization and qualification of microphysiological systems involves testing the different elements
that make up the device to ensure that their configuration mimics the physiology of the human structures
represented, behaving and providing values as similar as possible to those of the tissues in vivo.
It is in this context that this thesis attempts to develop a characterization protocol applicable to any
'Organ-On-a-Chip' system based on the tests carried out and compiled in the literature of devices in the
experimental or commercialization phase. Specifically, a characterization and qualification procedure is
presented in which the membrane permeability is monitored in real time depending on device elements
such as the presence or not of cell culture, the application or not of microfluids, among others.
The choice of the assays to be performed, from among those described in the protocol, will depend on
the elements of the OCC to be characterized.Els sistemes microfisiològics (MPSs), també coneguts com a "Organ-On-a-Chip" (OCC), han revolucionat la
manera d'entendre la biologia. Aquests sistemes, que inclouen el co-cultiu tridimensional i la tecnologia
microfluídica, pretenen imitar la fisiologia humana amb els sistemes de cultiu in-vitro. El seu objectiu és
augmentar el coneixement dels processos biològics, així com proporcionar una eina de diagnòstic eficaç
per a l'anàlisi de diferents fàrmacs.
L'estandardització de MPSs implica la robustesa i reproductibilitat d'aquests dispositius i és desitjable per
a la seva industrialització, producció i regularització. No obstant això, a causa de la primera etapa del
desenvolupament acadèmic i comercial d'aquesta tecnologia, no existeix cap procediment
d'estandardització en la literatura fins a data d’avui. Per tant, els experts recomanen centrar-se en la
caracterització o qualificació d'aquests dispositius. Aquesta caracterització i qualificació de sistemes
microfisiològics implica provar els diferents elements que componen el dispositiu per assegurar que la
seva configuració imiti la fisiologia de les estructures humanes representades, comportant-se i
proporcionant valors el més similars possible als dels teixits in-vivo.
És en aquest context que aquesta tesi intenta desenvolupar un protocol de caracterització aplicable a
qualsevol sistema "Organ-On-a-Chip" basat en les proves realitzades i compilades en la literatura de
dispositius en la fase experimental o de comercialització. Concretament, es presenta un procediment de
caracterització i qualificació en el qual la permeabilitat de la membrana es controla en temps real
depenent dels elements del dispositiu com la presència o no del cultiu cel·lular, l'aplicació o no de
microfluids, entre d'altres.
L'elecció dels assaigs a realitzar, d'entre els descrits en el protocol, dependrà dels elements de l'OCC que
el caracteritzin.Los sistemas microfisiológicos (MPSs), también conocidos como "Organ-On-a-Chip" (OCC), han
revolucionado la forma de entender la biología. Estos sistemas, que incluyen el co-cultivo tridimensional
y la tecnología microfluídica, pretenden imitar la fisiología humana con sistemas de cultivo in vitro. Su
finalidad es aumentar el conocimiento de los procesos biológicos, así como proporcionar una herramienta
de diagnóstico eficaz para el análisis de diferentes fármacos.
La estandarización de los MPSs implica la robustez y reproducibilidad de estos dispositivos y es deseable
para su industrialización, producción y regularización. Sin embargo, debido a la temprana etapa de
desarrollo académico y comercial de esta tecnología, hasta la fecha no existe en la literatura ningún
procedimiento de estandarización. Por ello, los expertos recomiendan centrarse en la caracterización o
cualificación de estos dispositivos. Esta caracterización y cualificación de los sistemas microfisiológicos
implica probar los diferentes elementos que componen el dispositivo para asegurar que su configuración
imita la fisiología de las estructuras humanas representadas, comportándose y proporcionando valores lo
más similares posibles a los de los tejidos in vivo.
Es en este contexto en el que esta tesis trata de desarrollar un protocolo de caracterización aplicable a
cualquier sistema 'Organ-On-a-Chip' basado en las pruebas realizadas y recopiladas en la literatura de
dispositivos en fase experimental o de comercialización. En concreto, se presenta un procedimiento de
caracterización y cualificación en el que se monitoriza en tiempo real la permeabilidad de la membrana
en función de elementos del dispositivo como la presencia o no de cultivo celular, la aplicación o no de
microfluidos, entre otros.
La elección de los ensayos a realizar, de entre los descritos en el protocolo, dependerá de los elementos
del OCC a caracterizar.Outgoin
Nat Rev Drug Discov
Improving the effectiveness of preclinical predictions of human drug responses is critical to reducing costly failures in clinical trials. Recent advances in cell biology, microfabrication and microfluidics have enabled the development of microengineered models of the functional units of human organs - known as organs-on-chips - that could provide the basis for preclinical assays with greater predictive power. Here, we examine the new opportunities for the application of organ-on-chip technologies in a range of areas in preclinical drug discovery, such as target identification and validation, target-based screening, and phenotypic screening. We also discuss emerging drug discovery opportunities enabled by organs-on-chips, as well as important challenges in realizing the full potential of this technology.1DP2HL127720-01/DP/NCCDPHP CDC HHS/United StatesDP2 HL127720/HL/NHLBI NIH HHS/United StatesP30 ES013508/ES/NIEHS NIH HHS/United States2016-04-09T00:00:00Z25792263PMC482638
Application of sequential cyclic compression on cancer cells in a flexible microdevice
Mechanical forces shape physiological structure and function within cell and tissue microenvironments, during which cells strive to restore their shape or develop an adaptive mechanism to maintain cell integrity depending on strength and type of the mechanical loading.
While some cells are shown to experience permanent plastic deformation after a repetitive
mechanical tensile loading and unloading, the impact of such repetitive compression on
deformation of cells is yet to be understood. As such, the ability to apply cyclic compression
is crucial for any experimental setup aimed at the study of mechanical compression taking
place in cell and tissue microenvironments. Here, we demonstrate such cyclic compression
using a microfluidic compression platform on live cell actin in SKOV-3 ovarian cancer cells.
Live imaging of the actin cytoskeleton dynamics of the compressed cells was performed for
varying pressures applied sequentially in ascending order during cell compression. Additionally, recovery of the compressed cells was investigated by capturing actin cytoskeleton and
nuclei profiles of the cells at zero time and 24 h-recovery after compression in end point
assays. This was performed for a range of mild pressures within the physiological range.
Results showed that the phenotypical response of compressed cells during recovery after
compression with 20.8 kPa differed observably from that for 15.6 kPa. This demonstrated
the ability of the platform to aid in the capture of differences in cell behaviour as a result of
being compressed at various pressures in physiologically relevant manner. Differences
observed between compressed cells fixed at zero time or after 24 h-recovery suggest that
SKOV-3 cells exhibit deformations at the time of the compression, a proposed mechanism
cells use to prevent mechanical damage. Thus, biomechanical responses of SKOV-3 ovarian cancer cells to sequential cyclic compression and during recovery after compression
could be revealed in a flexible microdevice. As demonstrated in this work, the observation of
morphological, cytoskeletal and nuclear differences in compressed and non-compressed
cells, with controlled micro-scale mechanical cell compression and recovery and using livecell imaging, fluorescent tagging and end point assays, can give insights into the mechanics
of cancer cells
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