376 research outputs found
hisTOOLogy: an user-friendly tool for quantitative stain detection in histological slices
No full textMetodo e dispositivo CAD/CAM combinato di microfabbricazione e microstrutture micro e nano architettura interna definita
No full textrealizzazione di strutture (S) meso, micro e
nanometriche con architettura interna definita,
secondo i quali un materiale (M) viene lavorato
tramite l’azione combinata di diversi sistemi
lavorazione quali: un sistema a estrusione del
materiale (M) a pressione idraulica attraverso una
siringa terminante con un condotto capillare di
dimensione variabile dal millimetro al micrometro;
o un sistema a estrusione dove il materiale (M)
fuoriesce tramite l’azione di un pistone meccanico;
o un sistema laser altamente focalizzato a potenza
e fascio regolabile incidente sul materiale (M); o
un sistema di fiber spinning dove il materiale (M)
è estruso per applicazione di un campo elettrico
tra il substrato di deposizione e la punta di
estrusione del serbatoio contenente il materiale da
lavorare; o un sistema di deposizione del materiale
(M) tramite testina ink-jet per la lavorazione sia
con viscosità molto basse sia con valori più
elevati; o un sistema dove il materiale (M) è
estruso da una siringa con capillare micrometrico
dopo fusione del materiale stesso per controllo di
temperatura. La posizione relativa dei sistemi di
fabbricazione combinata rispetto al piano di
lavorazione sul quale avviene la deposizione del
materiale (M) è ottenuta movimentando con un
sistema controllato CAD/CAM, in questo modo la
struttura (S) ottenuta con i processi di
fabbricazione presenta una forma tridimensionale
determinata e con una definizione e precisione
molto elevata
VISCOELASTIC CHARACTERISATION OF PIG LIVER IN UNCONFINED COMPRESSION
No full textUnderstanding and modelling liver biomechanics represents a significant challenge due the complex nature of this organ. Several methods and models based on direct measurements on the liver (e.g. rheological, compressive or indentation tests) or image-based techniques (e.g. magnetic resonance or ultrasound-based elastography) are reported in literature to characterise the liver viscoelastic behaviour in-vitro or in-vivo [Marchesseau et al, 2010]. Unfortunately, there is no consensus on liver viscoelastic properties, and results are strongly dependent on adopted testing method, sample type, status and testing conditions. We focused on in-vitro unconfined bulk compressive tests for deriving liver viscoelastic parameters in the linear viscoelastic region (i.e. small strain region). We propose the use of the ε̇M (epsilon dot method) which we developed to address the major drawbacks of standard tests (e.g. step response or dynamic mechanical tests) such as long test duration and initial contact between sample and testing apparatus, that may significantly pre-stress/strain very soft and hydrated samples and alter their status [Tirella et al, submitted]. With the ε̇M, samples are characterised using standard compressive tests at different strain rates (ε̇). Stress-time series collected at various ε̇ are then fitted using a multi curve shared parameter fitting approach. Liver viscoelastic parameters estimated with ε̇M were compared to those obtained using conventional dynamic mechanical (DMA) testing systems
Strain rate viscoelastic analysis of soft and highly hydrated biomaterials.
No full textMeasuring the viscoelastic behavior of highly hydrated biological materials is challenging because of their intrinsic softness and labile nature. In these materials, it is difficult to avoid prestress and therefore to establish precise initial stress and strain conditions for lumped parameter estimation using creep or stress-relaxation (SR) tests. We describe a method ( ɛ˙M or epsilon dot method) for deriving the viscoelastic parameters of soft hydrated biomaterials which avoids prestress and can be used to rapidly test degradable samples. Standard mechanical tests are first performed compressing samples using different strain rates. The dataset obtained is then analyzed to mathematically derive the material's viscoelastic parameters. In this work a stable elastomer, polydimethylsiloxane, and a labile hydrogel, gelatin, were first tested using the ɛ˙M, in parallel SR was used to compare lumped parameter estimation. After demonstrating that the elastic parameters are equivalent and that the estimation of short-time constants is more precise using the proposed method, the viscoelastic behavior of porcine liver was investigated using this approach. The results show that the constitutive parameters of hepatic tissue can be quickly quantified without the application of any prestress and before the onset of time-dependent degradation phenomena
Functionally Graded Materials (FGMs) with Predictable and Controlled Gradient Profiles: Computational Modelling and Realisation
No full textBiological function is intricately linked with structure. Many bio- logical structures are characterised by functional spatially distributed gradients in which each layer has one or more specific functions to perform. Reproducing such structures is challenging, and usually an experimental trial-and-error approach is used. In this paper we investigate how the gravitational sedimentation of discrete solid particles (secondary phase) within a primary fluid phase with a time-varying dynamic viscosity can be used for the realisation of stable and reproducible con- tinuous functionally graded materials (FGMs). Computational models were used to simulate the distribution of a particle phase in a fluid domain. Firstly a model of particle sedimentation was implemented in order to predict the particle gradient profiles. Then the fluid domain was modelled as phase with time dependent viscos- ity. Experiments were then used to validate the computational results. The models show that selected composition gradients can be tailored by controlling fluid and particle properties. Using this method the gradient of a custom two-phase system can be designed and tailored in a simple fashion. Moreover this approach can also be employed for the fabrication of porous structures, using a porogen as settling particle. The method is particularly useful in tissue engineering applications, to first predict and then control biomaterial gradients without the use of complicated rapid prototyping or computer aided manufacturing systems
The PAM2 system: a multilevel approach for fabrication of complex three-dimensional structures
No full textPurpose – The traditional tissue engineering approach employs rapid prototyping systems to realise microstructures (i.e. scaffolds) which recapitulate the function and organization of native tissues. The purpose of this paper is to describe a new rapid prototyping system (PAM-modular micro-fabrication system, PAM2) able to fabricate microstructures using materials with different properties in a controlled environment. Design/methodology/approach – Computer-aided technologies were used to design multi-scale biological models. Scaffolds with specific features were then designed using custom software and manufactured using suitable modules. In particular, several manufacturing modules were realised to enlarge the PAM2 processing material window, controlling physical parameters such as pressure, force, temperature and light. These modules were integrated in PAM2, allowing a precise control of fabrication parameters through a modular approach and hardware configuration. Findings – Synthetic and natural polymeric solutions, thermo-sensitive and photo-sensitive materials can be used to fabricate 3D scaffolds. Both simple and complex architectures with high fidelity and spatial resolution ranging from ^15mm to ^200mm (according to ink properties and extrusion module used) were realised. Originality/value – The PAM2 system is a new rapid prototyping technique which operates in controlled conditions (for example temperature, pressure or light intensity) and integrates several manufacturing modules for the fabrication of complex or multimaterial microstructures. In this paper it is shown how the system can be configured and then used to fabricate scaffolds mimicking the extra-cellular matrix, both in its properties (i.e. physic- chemical and mechanical properties) and architecture
Sensorized squeeze pressure bioreactor for mechanical modulation of cardiomyocyte phenotype
No full text2016_Rios_et_al_AHM_Data.pdf
No full textDataset corresponding to the experiments enclosed in "The CD44-mediated uptake of hyaluronic acid-based carriers in macrophages" by Julio M. Rios de la Rosa, Annalisa
Tirella, Arianna Gennari, Ian J.
Stratford and Nicola Tirelli.</p
Decoupling the role of stiffness from other hydroxyapatite signalling cues in periosteal derived stem cell differentiation.
No full textBone extracellular matrix (ECM) is a natural composite made of collagen and mineral hydroxyapatite (HA). Dynamic cell-ECM interactions play a critical role in regulating cell differentiation and function. Understanding the principal ECM cues promoting osteogenic differentiation would be pivotal for both bone tissue engineering and regenerative medicine. Altering the mineral content generally modifies the stiffness as well as other physicochemical cues provided by composite materials, complicating the "cause-effect" analysis of resultant cell behaviour. To isolate the contribution of mechanical cues from other HA-derived signals, we developed and characterised composite HA/gelatin scaffolds with different mineral contents along with a set of stiffness-matched HA-free gelatin scaffolds. Samples were seeded with human periosteal derived progenitor cells (PDPCs) and cultured over 7 days, analysing their resultant morphology and gene expression. Our results show that both stiffness and HA contribute to directing PDPC osteogenic differentiation, highlighting the role of stiffness in triggering the expression of osteogenic genes and of HA in accelerating the process, particularly at high concentrations
HisTOOLogy: an open-source tool for quantitative analysis of histological sections.
No full textHisTOOLogy is an open-source software for the quantification of digital colour images of histological sections. The simple graphical user interface enables both expert and non-expert users to rapidly extract useful information from stained tissue sections. The software's main feature is a generalizable colour separation algorithm based on k-means clustering which accurately and reproducibly returns the amount of colour per unit area for any stain, thus allowing the quantification of tissue components. Here we describe HisTOOLogy's algorithms and graphical user interface structure, showing how it can be used to separate different dye colours in several classical stains. In addition, to demonstrate how the tool can be employed to obtain quantitative information on biological tissues, the effect of different hepatic tissue decellularization protocols on cell removal and matrix preservation was assessed through image analysis using HisTOOLogy and compared with conventional DNA and total protein content assays. HisTOOLogy's performance was also compared with ImageJ's colour deconvolution plug-in, demonstrating its advantages in terms of ease of use and speed of colour separation
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