1,721,005 research outputs found
Using a 3-steps supercritical fluids assisted process for the generation of nanostructured biopolymeric scaffolds
No full textScaffolds can be used to substitute the extracellular matrix and to favour the generation of tissues and organs. Until now, various processes have been implemented for scaffolds generation, but they are characterized by several limits. Objective: In this work, we tested a supercritical fluids assisted process for the generation of nano-structured biopolymeric scaffolds; it is characterized by three steps: generation of a polymeric gel (loaded with a porogen), drying of the gel using supercritical CO2, waterwashing to remove the porogen. 3D Poly(D,L-lactic acid) scaffolds have been obtained, characterized by very high porosity (> 90%) and surface are (> 200 m2/g), and by a fibrous nanostructure (fibres ranging between 60 and 400 nm) superimposed to a micrometric cellular structure. Conclusion: Moreover, suitable mechanical properties (up to 125 KPa) and very low solvents residue (< 5 ppm) have been obtained
A new tool to generate PVDF-HFP + curcumin biocomposite by supercritical assisted gel drying
No full textIn this work Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) aerogels loaded with curcumin were produced by a supercritical CO2 assisted process. The aim was to create controlled release systems for wound healing applications. Performing the supercritical gel drying at suitable operating conditions (200 bar and 45°C), PVDF-HFP aerogels were generated starting from gels at 5, 10 and 12% w/w PVDF-HFP. They presented interesting morphologies: nanoporous, homogeneous and regular. Then, PVDF-HFP gels were loaded at 3% w/w of curcumin with respect to the polymer and, subsequently, dried by SC-CO2 at the same operative conditions previously tested. Curcumin release tests and DPPH tests were performed on the composite systems, for the determination of the curcumin antioxidant activity. The release test showed that the PVDF-HFP aerogels allowed to obtain a regular and prolonged release of curcumin, up to 45 h; furthermore, DPPH tests confirmed that curcumin still presented an high antioxidant activity (about 77%). All the samples produced were also characterized from a chemical and physical point of view: from the results of DSC and XRD analyses, it was observed that the gel drying process assisted by SC-CO2 did not lead to any change in the properties of the polymer (PVDF-HFP) and of the active agent (curcumin)
Biopolymeric porous structures obtained by supercritical fluids assisted processes
No full textIn the last years, biolpolymeric porous structures have acquired an increasing importance in different fields of engineering, ranging from chemical engineering to tissue engineering. Until now, various processes have been implemented for the generation of porous structures, but they are all characterized by several limits, such as long processing times, traces of organic solvents in the final products, low versatility, etc. In this work, we tested a green process assisted by supercritical fluids for the generation of biopolymeric porous structures: the supercritical phase inversion process. We processed different biopolymers such as Polysulfone, Polymethylmethacrylate and Polyvinyl alcohol, and analyzed the effect of process parameters (pressure, temperature, polymer concentration, kind of solvents) on the final morphology. The results confirmed the advantages of the supercritical fluids assisted process with respect to the traditional ones: indeed, dry porous structures were obtained in few hours; moreover, changing the parameters, it was possible to control the kind of structures obtained (from cellular one to bicontinuous) and the size of the pores and porosity (from 70 to 90%); finally, the structures were characterized by residual solvents amount lower than 5 ppm
Supercritical carbon dioxide techniques for processing microbial exopolysaccharides used in biomedical applications
No full textMicrobial exopolysaccharides are polymers that show a great potential for biomedical applications, such as tissue engineering applications and drug delivery, due to their biocompatibility, biodegradability and their gelling properties. These polysaccharides are obtained from a microorganism culture with a relatively straightforward downstream process thanks to their extracellular character, and can be processed to obtain aerogels, fibers and micro- or nano-particles with conventional techniques. However, these techniques present several disadvantages in that they involve time-consuming processes and the use of toxic solvents. Supercritical carbon dioxide techniques can overcome these drawbacks, but their use for processing microbial exopolysaccharides is not extended in the scientific community. This review describes the most frequently used exopolysaccharides in biomedical applications and how they can be obtained, as well as the different supercritical carbon dioxide techniques that can be used for processing them and their challenges. Specifically, high pressure shows a great potential to process and sterilize exopolysaccharide biomaterials for biomedical applications (e.g. tissue engineering or drug delivery systems) in spite of the disadvantage concerning the hydrophilicity of this type of polymers
Microbial exopolysaccharides as drug carriers
No full textMicrobial exopolysaccharides are peculiar polymers that are produced by living organisms and protect them against environmental factors. These polymers are industrially recovered from the medium culture after performing a fermentative process. These materials are biocompatible and biodegradable, possessing specific and beneficial properties for biomedical drug delivery systems. They can have antitumor activity, they can produce hydrogels with different characteristics due to their molecular structure and functional groups, and they can even produce nanoparticles via a self-assembly phenomenon. This review studies the potential use of exopolysaccharides as carriers for drug delivery systems, covering their versatility and their vast possibilities to produce particles, fibers, scaffolds, hydrogels, and aerogels with different strategies and methodologies. Moreover, the main properties of exopolysaccharides are explained, providing information to achieve an adequate carrier selection depending on the final application
Supercritical fluid processing of polymers
No full textThe use of supercritical fluids instead of organic solvents has attracted the interest of numerous researchers, due to the unique peculiarities of supercritical fluids which are characterized by solvent powers comparable to those of liquid organic solvents, diffusivity comparable to those of gaseous substances and quasi-zero surface tension [...]
Generation of biocompatible PCL foams by supercritical foaming
No full textIn this work, polycaprolactone (PCL) foams were generated by a supercritical CO2 (SC-CO2) assisted process. These foams can find application in tissue engineering as scaffolds, which require specific biological and morphological properties. SC-CO2 foaming process was carried out under different pressure and temperature conditions, in order to study the influence of these operating parameters on the final samples morphology. These polymeric foams were then analyzed by scanning electron microscope (FE-SEM) in order to observe their internal structure. The performed analyses showed the influence of pressure and temperature on the external shape and on the morphology of these polymeric foams, in particular on the pore size. Pressures of 100, 150, 200 and 250 bar and temperatures of 40 and 60°C were tested as operating variables. The PCL foams obtained at 40°C and 200 bar presented the lowest value of the average pores diameter (i.e., 85 ± 24 μm); this value was about 7 times lower than that of the foams produced operating at 40°C and 100 bar (622 ± 62 μm). These results confirmed the high versatility of the SC-CO2 foaming that allowed to generate PCL foams with tunable morphological characteristics
Cellulose acetate and supercritical carbon dioxide: Membranes, nanoparticles, microparticles and nanostructured filaments
No full textCellulose acetate (CA) is a very versatile biocompatible polymer used in various industrial sectors. Therefore, depending on the application, different morphologies are required. Different processes at industrial scale are commonly employed to obtain CA micro or nanoparticles (discontinuous structures) or CA membranes (continuous structures with discontinuities). In this work, two supercritical carbon dioxide (scCO2) based techniques, such as the semi-continuous supercritical antisolvent process (SAS) and the supercritical fluid phase inversion process, in which scCO2 plays the role of antisolvent, were employed. Varying the kind of organic solvent used to prepare the polymeric solution, the polymer concentration, and operating pressure and temperature, it was possible to tune the characteristics of the obtained material. In particular, using acetone as the organic solvent, filaments constituted by nanoparticles, expanded microparticles, nanoparticles with a mean diameter lower than 80 nm, and microporous membranes were obtained, varying the operating conditions. The attainment of spherical micron-sized particles was instead achieved using a mixture of acetone and DMSO as the organic solvent. Therefore, the versatility of the supercritical carbon dioxide-based techniques has been confirmed, and it was possible to obtain, using a single experimental plant, various morphologies of cellulose acetate (with controllable particles' or pores' diameters) by varying the operating conditions
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