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In recent years, scientific research has faced the numerous problems deriving from the presence of active ingredients in surface and groundwater. Traditional removal methods, such as adsorption and bioremediation, have several disadvantages; thus, in this work, membranes based on cellulose acetate loaded with Fe-N-TiO2, were tested for the photocatalytic degradation of Ceftriaxone Sodium from aqueous solution. The immobilization of the photocatalyst allows to overcome the limits of the photocatalytic process in suspension, which requires expensive and time-consuming post-treatments. Membranes were obtained by supercritical CO2 phase inversion process and were subjected to characterizations such as EDX, TGA, FT-IR, Raman spectroscopy and, subsequently, tested in adsorption tests in the dark and in the presence of visible light, to evaluate their photocatalytic activity. The variations in the concentration of the antibiotic, during the tests conducted, were monitored by HPLC chromatographic analysis. Samples with 10% and 30% by weight of Fe-N-TiO2 demonstrated relatively low adsorption efficiencies of the target contaminant, respectively equal to 22% and 18% in 180 minutes, for reasons related both to the morphology of the samples products, which changes from cellular to finger-like as the photocatalyst load increases, and to the quality of the dispersion. The membrane loaded with 20% by weight of Fe-N-TiO2 allowed a degradation of the model pollutant of 35% in 180 minutes; moreover, the reusability of the membranes was verified. The photocatalytic tests showed that the photocatalytic efficiency was highly correlated to the dispersion of the photocatalyst nanoparticles and to its loading in the polymeric membranes.

Vesicles are intriguing candidates for the topical administration of cosmetics as they can act as skin penetration stimulators, the individual components of the vesicles can impart additional desired properties to cosmetics, and are biodegradable and minimally toxic. Among the vesicular systems proposed for this application, liposomes are widely investigated. They are constituted of an inner aqueous core and an outer lipid bilayer. This configuration allows the encapsulation of both lipophilic and hydrophilic bioactive drugs. However, the traditional processes proposed for the production of these vesicles suffer from several limits: they are batch and time-consuming techniques, require post-treatments for the purification of vesicles from organic solvent residues and/or for reducing their mean size, do not favour a high encapsulation efficiency of drugs. In this work, SuperSomes, a sustainable and continuous process assisted by supercritical CO2, was used to produce nanometric liposomes loaded with ascorbic acid for cosmetic applications. Operating at 100 bar and 40 °C, stable liposomes characterized by a spherical morphology and a mean diameter lower than 250 nm, were obtained. An ascorbic acid encapsulation efficiency of 85% was measured and the supercritical process preserved the antioxidant activity of the drug.

Supercritical CO2 phase inversion is one of the most promising techniques to generate polymeric membranes. In recent years, it has been also tested to generate loaded membranes to be used in several applications such as controlled release, catalysis, tissue engineering, water purification, etc. In this work, membranes of cellulose acetate were generated, loaded with a highly hydrophobic drug with antifungal properties, i.e., quercetin. Different process parameters were tested to verify their effect on the final morphology of the membranes and on the drug distribution along the membranes. In particular, polymer concentration in the starting polymeric solution was varied from 5 to 15% w/w, operative pressure ranged between 100 and 200 bar, operative temperature from 45 to 55 °C. Different membranes structures were obtained: finger-like and cellular-like; the effect of these different morphologies on quercetin release was also analyzed, finding as finger-like structure promoted a faster drug release (i.e., less than 200 min) with respect to cellular structures (i.e., up to 1400 min). Results confirmed the capability of supercritical CO2 phase inversion process to generate loaded polymeric membranes and the high versatility of this process that allowed to generate different morphologies capable to control the drug release rate.

Supercritical-CO2 assisted electrospray is a new process used to produce polymeric micro- and nanoparticles characterized by tunable and regular morphologies. The major innovation consists of the addition of supercritical CO2 to the polymeric solution, obtaining a gas expanded liquid having reduced values of viscosity and surface tension. Due to its biodegradability and biocompatibility, cellulose acetate (CA) was selected as polymeric carrier for microparticles production, that can be used for drug delivery applications. Indeed, CA solutions were loaded with a poorly-water soluble compound, rutin (RUT), to improve its bioavailability. The experiments were performed at different CA concentrations (0.5 and 1 wt%) and different RUT concentration, that was varied from 2.5 to 7.5 wt% with respect to CA; the applied voltage was set at 30 kV. CA/RUT microparticles were successfully produced; working at 140 bar and 30 kV, particles characterized by an average diameter of 980±120 nm and networked fibers were obtained, processing 1 wt% CA solution and using a RUT concentration of 7.5 wt% with respect to CA. IR spectroscopy revealed the physical dispersion of RUT into CA particles.

Supercritical assisted electrospray is an emerging process used for the production of polymeric micro- and nanoparticles of controlled size and distribution. The main innovation consists of the addition of supercritical CO2 to the polymeric solution, with the aim of obtaining an expanded liquid, characterized by reduced viscosity and surface tension. Cellulose acetate (CA) was selected as the model polymer, thanks to its peculiarities, such as low cost, biodegradability and biocompatibility. The experiments were performed at different pressures (from 80 bar to 140 bar) and polymer concentrations (from 0.2% to 1% w/w). CA nanoparticles were successfully produced; working at 140 bar and 30 kV, particles characterized by a mean diameter in the range from 266.7±145 nm to 343.9±120 nm were obtained, processing 0.2% w/w and 1% w/w CA solutions, respectively. These results open the way to the production of biopolymeric sub-microcarriers that, loaded with active molecules, can be used in nutraceuticals.

In 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.

In 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).

A supercritical CO2 (SC-CO2) assisted phase inversion process was tested to load a fructose exopolysaccharide with amphiphilic properties (i.e., levan) in membranes of polyvinylidenefluoride-co-hexafluoropropylene (PVDF-HFP). The aim was to investigate the effect of levan on the morphological and biological properties of PVDF-HFP membranes. Different loadings of levan from 0 to 50% w/w were tested: PVDF-HFP + levan membranes characterized by a foam-like structure were generated, with an increase of overall porosity from 75 to 90%. The effect of levan addition on mechanical and biological characteristics of PVDF-HFP membranes was also studied: a decrease of the mechanical resistance from 12 to 1 MPa and an increase of cells (colon cancer cell line HTC-116) adhesion from 8% to 35% were measured. In conclusion, SC-CO2 assisted process was able to generate composite structures potentially useful for biological applications, characterized by a homogeneous distribution of levan and by improved biological properties.

In 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.

Supercritical phase inversion process was successfully implemented to produce loaded polymeric membranes of cellulose acetate with a synthetic clay mineral (i.e., laponite), to enhance both their mechanical and biological properties. The generated structures presented a microporous structure with a pore size ranging from 8.7 to 12.6 µm, depending on the laponite concentration: the addition of a solid in the starting solution caused a phase separation delay and a consequent pores size increasing. At the same time, the addition of laponite in form of nanodisks improved the mechanical characteristics of the material in terms of Young modulus up to 4.2 MPa. Furthermore, a relevant increase up to 80.9% on cellular adhesion (cell line BT474) was found thanks to the incorporation of laponite inside these membranes. This phenomenon can be attributed to the high surface area and the mineral properties of this clay; therefore, the inclusion of laponite in cellulose acetate membranes produced by supercritical phase inversion, drastically transformed this polymer into a suitable material for tissue engineering applications.

In this work, poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) membranes for water purification were produced by supercritical phase inversion using a mixture of supercritical CO2 (SC-CO2) and ethanol as non-solvent. Different polymer concentrations (from 10 to 20% w/w) and ethanol amount by volume (from 1 to 50% v/v) with respect to SC-CO2 flow rate, were tested in order to study their influence on membranes morphology, surface area and porosity; supercritical processing was performed at a pressure of 200 bar and a temperature of 45 °C. Membranes characterized by a cellular morphology with a nanoporous substructure and/or by an homogeneous nanoporous morphology were obtained, changing the starting polymer concentration and the ethanol amount during the process. In particular, increasing the amount of ethanol from 1 to 50% v/v, an increase of membranes porosity and surface areas was obtained, and the membranes morphology changed from microporous with nanoporous cell walls to completely nanoporous, due to an increase of the non-solvent power that improved the in-situ gelification mechanism during the supercritical phase separation.