1,721,084 research outputs found
Role of foams in the preparation of highly porous materials
No full textA novel process for the prepn. of highly porous biomaterials by foam templating is illustrated. In detail, this method consists of insufflating under stirring an inert gas into a concd. soln. of a hydrophilic polymer in the presence of a suitable surfactant. In the lecture, the versatility of this approach to the synthesis of porous materials made of both natural and/or synthetic polymers is illustrated as well as their potentiality in the field of tissue engineering
Matrici Polimeriche Porose Biocompatibili e Loro Applicazioni
No full textBrevetto Italiano RM2003A000307, pp. 1-43 (data di deposito 20 giugno 2003
The influence of porogen type on the porosity, surface area and morphology of poly(divinylbenzene) polyHIPE foams
No full textThe type of porogen added to the continuous phase of HIPEs containing divinylbenzene strongly in ̄uences the morphology of the resulting PolyHIPE foam. The cell size was reduced as the solvent became a better cosurfactant, as inferred from surface pressure measurements of ®lms representative of each HIPE continuous phase. In addition, this caused the windows connecting adjacent cells to increase, to such an extent in two cases that the cellular morphology was apparently lost. The surface area increased as the solubility parameter of the solvent approached that of the polymer, however the materials with highest surface areas also had a noncellular morphology and were very weak mechanically. This could be recti®ed by the use of mixtures of the solvents investigated, producing materials with surface areas up to 554 m2 g21, a cellular morphology and good mechanical properties
The Morphology and Surface Area of Emulsion derived (PolyHIPE) Foams Prepared with Oil-phase Solubile Porogenic Solvents 1: Span 80 as Surfactant
No full textPoly(divinylbenzene) emulsion-derived (PolyHIPE) solid foams prepared with porogens (toluene, chlorobenzene, (2-chloroethyl)benzene, 1,2-dichlorobenzene, and 1-chloro-3-phenylpropane) in the oil phase have morphologies and surface areas that are strongly influenced by the nature of the porogen. For the case where the surfactant employed is Span 80, we show that the solid foam structure depends on (i) the ability of the solvent to swell the growing network, (ii) the solvent polarity, and (iii)
the ability of the solvent to adsorb at the emulsion interface. In particular, relatively polar solvents that are able to transport water through the emulsion continuous phase (Ostwald ripening) are shown to produce much lower surface areas than analogous resins prepared by homogeneous solution polymerization of divinylbenzene in the presence of the solvent in question alone. The influence of Ostwald ripening is further suggested by the observation that surface area decreases with increasing emulsion aqueous phase content for relatively polar solvents whereas little variation in surface area with aqueous phase content is observed for more hydrophobic solvents. All PolyHIPEs prepared were characterized by SEM, TEM, N2 sorption analysis, and mercury intrusion porosimetry. The relative merits of TEM and mercuryintrusion porosimetry as techniques for the reliable characterization of the solid foams are discussed
Low Viscous Bioinks for Extrusion-Based 3D Bioprinting
No full text3D bioprinting is an emerging field that can be described as a robotic additive biofabrication technology that has the potential to build tissues or organs. In general, bioprinting uses a computer controlled printing device to accurately deposit cells and biomaterials into precise architectures with the goal of creating on demand organized multicellular tissue structures and eventually intra-organ vascular networks. Progress in bioprinting have been following two interdependent pathways:
1. development of more precise and versatile bioink deposition techniques;
2. development of bioinks that provide a growth and function-supportive medium to the cells and promote their proper organization and function while minimizing the effect of printing on cell viability and without compromising printing fidelity and stability of the construct.
Many bioinks have been formulated for various cells types, but those currently used for 3D printing still have challenges and limitations, mainly low cell viability during printing and limited resolution.
To overcome these limitations, we developed a new concept of extrusion-based bioprinting technique, which implements a microfluidic control in the dispensation of the bioink. The coupling of microfluidic platforms with the dispensing system is made possible by the use of a coaxial extrusion head that induces the solidification of the bioink in the form of a hydrogel simultaneously to its deposition.
In particular, among other components, the bioink contains alginate, whose gelation is induced by exposing it to a crosslinking solution containing calcium ions. The bioink and the crosslinking solution are delivered respectively through the internal and external needles of a coaxial-needles system. At the ending tip of the dispensing head the two solutions meet causing the immediate solidification of the bioink due to the ionic crosslinking of alginate. In this way, it is possible to deposit hydrogel fibers with dimensions ranging between 150 and 300 μm. The printing conditions described above are mild since bioink viscosity is low and crosslinking conditions can be tuned to be harmless toward encapsulated cells.3D bioprinting is an emerging field that can be described as a robotic additive biofabrication technology that has the potential to build tissues or organs. In general, bioprinting uses a computer controlled printing device to accurately deposit cells and biomaterials into precise architectures with the goal of creating on demand organized multicellular tissue structures and eventually intra-organ vascular networks. Progress in bioprinting have been following two interdependent pathways:
1. development of more precise and versatile bioink deposition techniques;
2. development of bioinks that provide a growth and function-supportive medium to the cells and promote their proper organization and function while minimizing the effect of printing on cell viability and without compromising printing fidelity and stability of the construct.
Many bioinks have been formulated for various cells types, but those currently used for 3D printing still have challenges and limitations, mainly low cell viability during printing and limited resolution.
To overcome these limitations, we developed a new concept of extrusion-based bioprinting technique, which implements a microfluidic control in the dispensation of the bioink. The coupling of microfluidic platforms with the dispensing system is made possible by the use of a coaxial extrusion head that induces the solidification of the bioink in the form of a hydrogel simultaneously to its deposition.
In particular, among other components, the bioink contains alginate, whose gelation is induced by exposing it to a crosslinking solution containing calcium ions. The bioink and the crosslinking solution are delivered respectively through the internal and external needles of a coaxial-needles system. At the ending tip of the dispensing head the two solutions meet causing the immediate solidification of the bioink due to the ionic crosslinking of alginate. In this way, it is possible to deposit hydrogel fibers with dimensions ranging between 150 and 300 μm. The printing conditions described above are mild since bioink viscosity is low and crosslinking conditions can be tuned to be harmless toward encapsulated cells
Synthesis and characterization of highly porous polyvinyl alcohol hydrogels crosslinked in different ways
No full textPolyvinylalc. (PVA) is a water sol. synthetic polymer already used in areas such as food chem., pharmaceuticals, medicine and biotechnol. Applications of PVA hydrogels in the biomedical field include contact lenses, wound dressing, coatings for sutures and catheters and as scaffolds for long-term culture of hepatocytes and mesenchimal stem cell. Despite its excellent properties as a film forming and component of gels and scaffolds no attempts other than freeze-drying have been pursued to develop alternative methods for the creation of scaffolds suitable for tissue engineering applications. Here we propose an alternative and novel method based on gas foaming for the prepn. of PVA scaffolds endowed with good mech. properties
Nuovo metodo di stampa 3D di bioinks a bassa viscosità
No full texttecnologia che nell’ambito di quella branca della scienza e tecnologia nota come ingegneria tissutale (TE) si sta imponendo in misura crescente grazie alla potenzialità che offre di replicare la complessità isto-morfologica dei tessuti umani. Il bioprinting rappresenta l’aspetto più moderno delle tecnologie di prototipazione rapida (RP) applicate al TE. Il RP in generale prevede la progettazione dell’oggetto da replicare al computer utilizzando software dedicati e la generazione di un file di istruzioni che viene tradotto nell’oggetto reale attraverso la macchina di prototipazione, strato dopo strato. Lo sviluppo di questa tecnologia sta attualmente seguendo due direttrici strettamente correlate tra di loro: lo sviluppo di nuove tecniche di deposizione che consentano la stampa di nuovi bioink con elevata risoluzione; lo sviluppo di nuovi bioinks che forniscano un mezzo adeguato per l’adesione e proliferazione delle cellule incapsulate e ne promuovano la loro organizzazione tridimensionale minimizzando al tempo stesso gli effetti negativi del processo di stampa sulla sopravvivenza delle cellule.
Molti bioinks sono stati formulati per i vari fenotipi cellulari, ma quelli che sono in uso corrente nella stampa 3D soffrono di bassa risoluzione e garantiscono solo un basso grado di sopravvivenza cellulare spesso a causa della loro elevata viscosità. Per ovviare a questi limiti, recentemente abbiamo sviluppato una nuova tecnologia di estrusione di bioinks caratterizzati da una bassa viscosità ed elevata bioattività. Il dispositivo di deposizione consiste nell’accoppiamento di un sistema microfluidico con un estrusore costituito da due aghi coassiali che consente la manipolazione spazio-temporale del bioink usato e la sua solidificazione sotto forma di un gel contestualmente alla sua deposizione. Il componente essenziale del bioink alla base di questa tecnica di deposizione è rappresentato dall’alginato la cui gelazione è indotta dalla presenza di ioni calcio. In particolare, il bioink contenente alginato, cellule ed altri biopolimeri viene estruso attraverso l’ago interno del sistema di agi coassiali mente la soluzione contenente ioni calcio attraverso quella esterno. Quando le due soluzioni si incontrano all’estremità del sistema di aghi coassiali il bioink gela istantaneamente permettendo la deposizione di una fibra di gel del diametro compreso tra i 150 e 300 mm contenente le cellule. Questa tecnologia è stata applicata con successo nella stampa di strutture simile ai vasi sanguigni, tessuto cartilagineo e muscolare liscio
- …
