PLLA Scaffold with Gradient pore size in microphysiological tissue system bioreactor for Osteochondral regeneration

Cartilage and bone tissues in the joints are intimately linked and form the osteochondral unit. A better understanding of both disease and regenerative processes of bone and cartilage requires the study of both tissues together, as part of the osteochondral unit to account for their mutual interactions. However, the production of scaffolds for osteochondral tissue regeneration is a challenging task, since scaffolds must mimic the differents morphologies of cartilage and bone. Thermally Induced Phase Separation (TIPS) is one of the most adaptable techniques to produce porous scaffold for Tissue Engineering applications. A wide range of morphologies in terms of both pore size and distribution…

A Poly-L-Lactide scaffold with continuous gradient pore size for osteochondral regeneration validated in a microphysiological tissue system bioreactor

A microphysiological tissue system (MPS) bioreactor has been developed to replicate in vitro the in vivo OC physiological conditions. The MPS allows separate control of the chondral and osseous environment while permitting communication between chondrocytes and osteoblasts across the OC junction, similar to the conditions of OC tissue in vivo. We have used here our MPS system to validate the TIPS -generated pore-gradient PLLA scaffold.

Crystallization kinetics of a PBT/PET blend according to a Continuous Cooling Transformation (CCT) approach

CRYSTALLIZATION OF PBT/PET BLENDS UNDER LOW AND HIGH COOLING RATES: THERMODYNAMICS AND KINETICS CONSIDERATIONS

Modeling and experimental approaches for the characterization of phase equilibria in polymer solutions

Anisotropic scaffold for Bone Tissue Engineering

Polyactide Biodegradable Scaffolds for Tissue Engineering Applications: Phase Separation-Based Techniques

One of the most reliable techniques for the preparation of biodegradable scaffolds suitable for tissue engineering applications (e.g. regeneration of wounded/damaged tissues) is based on liquid/liquid phase separation of ternary solvent/antisolvent/polymer solutions. In particular, two phase separation protocols are examined here: Thermally Induced Phase Separation (TIPS) and Diffusion Induces Phase Separation (DIPS). According to the former protocol, a thermodynamically stable polymeric ternary solution is brought below its metastability/instability point (spinodal/binodal curve) by quench in a cooling medium: under opportune conditions, a foam-like structure is formed by nucleation and 3-…

Theoretical Predictions and experimental determination of cloud point curves for polymeric solutions: an application to the ternary system Poly-lactic-acid (PLLA)-dioxane-water

The lattice fluid model with specific interactions was applied to the ternary system Poly-L-lactic-acid (PLLA)-dioxane-water. Model parameters were determined by fitting experimental data. The as-obtained parameters were used to calculate the complete phase diagram. An experimental apparatus for cloud point measurements, which is under construction, is presented.

A survey on models for the prediction of phase equilibria in polymer solutions

Membrane porose in PLLA per la rigenerazione di mucosa bronchiale umana ottenute mediante DIPS

An Innovative Method to Produce Scaffolds with a Pore Size Gradient for Tissue Engineering Applications

Thermally Induced Phase Separation (TIPS) is a technique for the production of porous scaffold for Tissue Engineering applications. A wide range of microporous morphologies, in terms of pore size and distribution, can be obtained by tuning TIPS processing parameters, especially thermal history. The production of scaffolds for bone tissue regeneration is a challenging target: as a matter of fact, scaffolds must mimic the bone morphology, thus requiring a gradient of pore dimension and morphology along one dimension. To attain this goal, an experimental apparatus capable to impose different thermal histories on the two sides of a sample was designed, set up and tested. The sample (35x35 mm su…

The concept and the application of no-flow temperature (NFT) in simulation of injection moulding

Determination of the crystallization kinetics of a PBT/PET blend in relation to the behaviour of the constituents

PLLA scaffolds based on thermally induced phase separation: morphology, cell seeding and proliferation

Blending PLLA with PLA so as to tune the biodegradabilty of polymeric scaffolds for soft tissue engineering

SOLIDIFICATION BEHAVIOUR OF PBT/PET BLENDS UNDER PROCESSING CONDITIONS

Synthesis of PLLA scaffolds for tissue engineering via phase separation

AN EXPERIMENTAL APPARATUS TO CHARACTERIZE PHASE SEPARATION IN POLYMER SOLUTIONS

Solidification of sindiotactic polystyrene (sPS) under drastic conditions by CCT

CLOUD POINT MEASUREMENTS IN MEMBRANE FORMING SYSTEMS

Structure and Morphology Control in Polymer Forming Through the Thermal History

Two examples of the application of the Continuous Cooling Transformation (CCT) method for investigating polymer solidification under processing conditions are illustrated. One example concerns the solidification behaviour of syndiotactic polystyrene (sPS) from the melt, showing an anomalous trend of density versus cooling rate, exhibiting a minimum around 1 °C/s. Once phase composition is obtained from WAXD deconvolution, density can be closely predicted, its minimum depending on the competition among crystalline phases upon increasing cooling rate. Another example regards the formation of Poly-Left Lactic Acid (PLLA) foams via Thermally Induced Phase Separation (TIPS) by starting from ther…

Studio della solidificazione durante lo stampaggio ad iniezione mediante un test di indentazione

Il concetto di "no-flow temperature" e il problema della solidificazione in flusso durante lo stadio di riempimento nel processo di stampaggio ad iniezione

Durante la fase di riempimento del processo di stampaggio ad iniezione, il flusso del materiale polimerico può fermarsi a causa della sua elevata viscosità, nonostante non sia avvenuta la solidificazione tramite transizione vetrosa o cristallizzazione. La no-flow temperature (NFT) è un parametro che rappresenta la "temperatura di solidificazione reologica" di un polimero, ed è utilizzata in molti software di simulazione del processo di stampaggio ad iniezione. L'estrapolazione della viscosità a basse temperature tramite modelli reologici può introdurre errori considerevoli nelle simulazioni, poichè le misure di viscosità sono usualmente effettuate ad alte temperature: in tal modo, i modelli…

Pre-vascularized PLLA scaffolds: A new approcah to develop deep tissue regeneration

Scaffolds biodegradabili in PLLA con gradiente di porosità per rigenerazione ossea

PLLA biodegradable scaffolds for Vascular Tissue Engineering (VTE) applications via dip drawing and Diffusion Induced Phase Separation (DIPS)

Temperature influence on the morphology of porous structures prepared via Thermally Induced Phase Separation (TIPS)

TISSUE ENGINEERING FOR THE DEVELOPMENT OF THREE-DIMENSIONAL INVITRO MODELS OF HUMAN MUCOSAE

Traditional two-dimensional (2D) cell cultures only partially reflect the morpho-molecular pattern of human cells in tissues, and they are also unable to fully mimic the complexity of the in vivo microenvironment. Cell development in in vivo systems differs significantly from classical 2D cell culture models, especially with regard to the morphology, growth kinetics, gene expression and the degree of differentiation. Tissue engineering allows the reproduction of tissues by cell seeding on biocompatible scaffolds, to form a homogenous ...

PLA/PLLA scaffold for vascular tissue engineering applications

A critical obstacle encountered by tissue engineering is the inability to maintain large masses of living cells upon transfer from the in vitro culture conditions to host in vivo. Capillaries, and the vascular system, are required to supply essential nutrients, including oxygen, remove waste products and provide a biochemical communication “highway”. Another task in this research field is the possibility to tune the biodegradability of the scaffold. After implantation, the scaffold must be gradually populated by cells and replaced by extra cellular matrix; with this respect, it is crucial that this replacement takes place with appropriate dynamics and a well-defined timescale. A premature d…

PLLA scaffolds for tissue engineering prepared via thermally induced phase separation

Solidification of Syndiotactic Polistyrene (sPS) under Pressure and High Cooling Rate

Supercritical carbon dioxide induces sterilization of PLLA scaffolds contaminated by E. coli.

The common sterilization techniques are based on physical processes that involve, for example, the use of autoclaves or systems to radiation such as γ-rays that can cause a structural change of the polymer treated. Therefore, the use of supercritical carbon dioxide (scCO2) is an excellent alternative, as it does not induce any variation of biomaterials treated (Perrut M., 2012). It's a good candidate because is readily available at low cost, non-toxic and non-flammable, it has an easily accessible critical point (7.38 MPa and 304.2 K) and excellent transport properties and wettability (White A. et al., 2005). We report the development of a supercritical CO2 based process capable of steriliz…

Use of Modified 3D Scaffolds to Improve Cell Adhesion and Drive Desired Cell Responses.

In the most common approach of tissue engineering, a polymeric scaffold with a well-defined architecture has emerged as a promising platform for cells adhesion and guide their proliferation and differentiation into the desired tissue or organ. An ideal model for the regeneration should mimic clinical conditions of tissue injury, create a permissive microenvironment for diffusion of nutrients, gases and growth factors and permit angiogenesis. In this work, we used a 3D support made of synthetic resorbable polylactic acid (PLLA), which has considerable potential because of its well-known biocompatibility and biodegradability. One of the factors that influence cell adhesion to the scaffold is …

Solidification of Polypropylene Under Processing Conditions – Relevance of Cooling Rate, Pressure and Molecular Parameters

A6 stem cells culture into a biodegradable PLLA scaffold

Solidification of sindiotactic polystyrene (sPS) under drastic conditions by Continuous Cooling Transformation (CCT)

Peltier cells as temperature control elements: Experimental characterization and modelling

Poly lactic acid based scaffolds as graft for small-diameter arterial replacement.

Vascular Tissue engineering (VTE) has emerged as a promising approach to develop blood vessel substitutes. Investigators have explored the use of arterial tissue cells combined with various types of natural and synthetic scaffolds to make tubular constructs in order to develop a functional small-diameter arterial replacement graft. The grafts must mimic the unique viscoelastic nature of an artery and be non-disruptive to blood ?ow. Moreover, after implantation, the scaffold must be gradually populated by cells and replaced by extra cellular matrix; with this respect, it is crucial that this replacement takes place with a well-defined timescale. In this work tubular scaffolds for VTE were pr…

Characterization of commercial polymeric membranes for membrane distillation processes

POROUS SCAFFOLDS BASED ON PLLA/FUNCTIONALISED POLYMERS BLENDS PRODUCED BY THERMALLY INDUCED PHASE SEPARATION

Synthesis of a porous and biodegradable PLLA scaffold for application of tissue engineering

Heat Transfer and Crystallization During Fast Cooling of Thin Polymer Film

Migration of brain capillary endothelial cells inside poly (lactic acid) 3D scaffolds

The brain capillary endothelial cells (BCECs) form the blood brain barrier (BBB) under the effects of the brain microenvironment. BCECs are sealed together by tight junctions (TJs) that are responsible for the barrier phenotype. In these junctions, molecules such as JAM (junctional adhesion molecules), occludin and claudins are present. Threedimensional scaffolds are used to grow cells in order to obtain in vitro engineered tissues. On the base of these considerations, the aim of this work was to understand whether the endothelial cells were able to grow and survive on a new three-dimensional structure. If yes, indeed, this system could be further enriched and used to set a three-dimensiona…

Effect of pressure and high cooling rates on the solidification behaviour of sindiotactic polystryrene (sPS)

An Innovative Method to Produce Scaffolds with a Pore Size Gradient for Tissue Engineering

Measurement of cloud point temperature in polymer solutions

Ultra-fast-prototyping of PMMA structures for micro-engineering applications: Choosing the right material

Machining of poly(methyl methacrylate) (PMMA) by laser has been extensively studied in engineering research for several applications including microfluidic manufacturing and rapid prototyping. However, very few investigations have taken into consideration the wide range of physico-chemical characteristics of commercially available PMMA that can often affect the quality of the laser-machined structures. These characteristics are often ignored, with many manufacturing publications focusing on a single source of PMMA. To understand the different bonding strengths and laser-cut qualities in the context of our ultra-fast prototyping technique, four types of PMMA have been examined. Molecular wei…

Hydrophobic polymeric membranes: experimental characterization for membrane distillation applications

Nonisothermal Crystallization Kinetic of Syndiotactic Polystyrene/Clay Nanocomposites

The solidification behavior of a PBT/PET blend over a wide range of cooling rate

In recent years, much attention has been paid to the development of high-performance polyester blends, among which blends of polybutylene terephtha- late/polyethylene terephthalate (PBT/PET) are expected to exhibit remarkable prop- erties as far as their crystallization behavior is concerned. Through trial and error, appropriate commercial compositions have been chosen which could not be otherwise explained by a suitable interpretation of the mechanisms determining their solidifica- tion behavior. The solidification behavior of a 60/40 w/w PBT/PET blend was studied in a wide range of cooling conditions, according to a continuous cooling transforma- tion (CCT) procedure developed previously,…

Preparation and characterization of PLLA-HA scaffolds for bone tissue engineering

In this work, the possibility to produce composite - Poly-L-lactic acid (PLLA) and Hydroxyapatite (HA) - porous scaffolds via Thermally Induced Phase Separation for bone tissue engineering applications was investigated. Several PLLA/HA ratios were tested (70/30, 50/50, 30/70 and 20/80 wt/wt) and the as-obtained scaffolds were characterized via Scanning Electron Microscopy (SEM), Wide Angle X-Ray Diffraction (WAXD) and compression test. The results showed that the presence of HA does not influence the phase separation process. Morphological analysis revealed an open structure with interconnected pores and HA embedded in the polymer matrix. This evidence was confirmed by WAXD analysis; where …

Porous PLLA scaffolds are optimal substrates for internal colonization by A6 mesoangioblasts and immunocytochemical analyses

In the present paper, mouse mesoangioblasts were seeded onto bidimensional matrices and within three-dimensional porous scaffolds of poly(L-lactic acid) (PLLA), in the presence or absence of type I collagen coating, observed under the scanning electron microscope, and tested for their adhesion, survival and proliferation. Immunolocalization of Hsp70, an abundant and ubiquitous intracellular protein in these cells, was also performed in sectioned cell-containing scaffolds under the confocal fluorescence microscope to check whether "in situ" analysis of intracellular constituents was feasible. The data obtained show that PLLA films allow direct cell adhesion and represent an optimal support f…

Crystallization behaviour of PBT-rich PBT/PET blends according to a Continuous Cooling Transformation (CCT) protocol

Microscopic evidence of the primary astrocytes' morphological differentiation and migration inside porous Poly-L-lactic acid 3D‑scaffolds

Tissue engineering is an emerging multidisciplinary field that aims at reproducing in vitro and/or in vivo tissues with morphological and functional features similar to the biological tissue of the human body [1]. In the attempt to construct suitable tissue models, a critical step is the setting of 3D scaffolds that mimic the supportive structures of a natural extracellular matrix microenvironment into which cells are normally embedded. In this context, the generation of 3D cultures of brain cells is of particular interest. For instance, the poly L‐lactic acid (PLLA) polymer is wildly used because of its biocompatible and biodegradable potential; the PLLA scaffold topography simulates the n…

Solidification during the filling stage of injection molding: a simulation-oriented study

Composites poly-lactic acid - hydroxyapatite scaffolds prepared via Thermally Induced Phase Separation

Membrane biodegradabili in PLLA preparate mediante DIPS (Diffusion Induced Phase Separation) come supporto per la rigenerazione di mucosa bronchiale umana

PREPARATION AND HYDROLYTIC DEGRADATION OF POLY LACTIC ACID BASED SCAFFOLDS

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Comparison of the solidification of a commercial PBT-PET blend with the behaviour of the constituents

The use of Diffusion Induced Phase Separation (DIPS) technique for the preparation of biodegradable scaffolds for angiogenesis

Membrane Distillation for a solar powered desalination pilot unit

Injection molding of syndiotactic polystyrene/organophilic clay nanocomposite

A study via simulation of solidification during injection molding

The final properties of an injection-molded part are strictly dependent on the solidification dynamics occurring during the processing. The experimental derivation of information about polymer solidification throughout the injection molding cycle is still an open challenge. To overcome the practical issues, the process simulation is proposed as a mean to derive useful data, and especially for identifying the most influencing parameters. The no-flow temperature (NFT) is a parameter used in most of injection molding simulation packages as a mean to determine whether the polymer flows or it is solid. With this simple parameter it is possible to take into account the rheological solidification …

Tissue engineered vascular grafts based on poly-lactic acid blends

A great deal of research has been pursued in the last decade with the goal of developing blood vessel substitutes. Tissue engineering has emerged as a promising approach to address the shortcomings of current options. One of the major tasks in this research field is the possibility to tune the biodegradability of the implantable devices (scaffolds). After implantation, the scaffold has to be replaced by extra cellular matrix; with this respect, it is crucial that this replacement takes place with appropriate dynamics and a well-defined timescale. In this work tissue-engineered vascular graft were produced, utilizing several PLLA/PLA blends (100/0, 90/10, 75/25 wt/wt) in order to tune their …