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Celluloseacetate (CA)/graphene oxide (GO) nanocomposite membraneswere generated by an assisted phase inversion process, based on theuse of SC–CO2as nonsolvent, operating at 200 barand 40 °C; loadings of GO up to 9% w/w were tested. The structuresmaintained the cellular morphology, characteristics of CA membranes,also at the highest GO loadings used, with a porosity of about 80%,but the presence of GO influenced the pore sizes, that ranged betweenabout 9 and 16 μm. The starting GO and the nanocomposite structureswere characterized by the combination of various techniques that evidenceas sulfur and chlorinated impurities, that were present in the startingGO material, were completely eliminated by the interaction with SC–CO2during structures formation; moreover, a partial reductionof GO to graphene was also observed. [ABSTRACT FROM AUTHOR]

Tissue regeneration is aimed at producing biological or synthetic scaffolds to be implanted in the body for regenerate functional tissues. Several techniques and materials have been used to obtain biodegradable synthetic scaffolds, on which adhesion, growth, migration and differentiation of human cells has been attempted. Scaffolds for tendon regeneration have been less frequently proposed, because they have a complex hierarchical structure and it is very difficult to mimic their peculiar mechanical properties. In this review, we critically analyzed the proposed materials and fabrication techniques for tendon tissue engineering and we indicated new preparation processes, based on the use of supercritical fluids, to produce scaffolds with characteristics very similar to the native tendon structure. [ABSTRACT FROM AUTHOR]

A supercritical CO2 drying process was used to prepare an innovative nanocomposite, formed by a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF HFP) aerogel loaded with RuO2 nanoparticles. The produced nanocomposites, at 10% and 60% w/w of RuO2, were tested for the electrochemical oxidation of model tannery wastewaters. The effect of the electrochemical oxidation parameters, like pH, temperature, and current density, on tannic acid, intermediates, and chemical oxygen demand (COD) removal, was investigated. In particular, the electrolysis of a simulated real tannery wastewater, using PVDF HFP_RuO2 60, was optimized working at pH 10, 40 °C, and setting the current density at 600 A/m2. Operating in this way, surfactants, sulfides, and tannins oxidation was achieved in about 2.5 h, ammonium nitrogen oxidation in 3 h, and COD removal in 5 h. When chloride-containing solutions were tested, the purification was due to indirect electrolysis, related to surface redox reactions generating active chlorine. Moreover, sulfide ions were converted into sulfates and ammonium nitrogen in gaseous N2. [ABSTRACT FROM AUTHOR]

In this work, Class 2 and Class 3 solvents contained in two corticosteroids, flunisolide (Fluni) and fluticasone propionate (Fluti), were reduced to a few ppm by supercritical CO2 extraction. The process was carried out at pressures from 80 to 200 bar, temperatures of 40 °C and 80 °C, and at a fixed CO2 flow rate of 0.7 kg/h. The results demonstrated that CO2 density is the key parameter influencing the extraction kinetics and the solvent final residue. In particular, in the range investigated, optimal pressure and temperature conditions for the extraction of residual organic solvents were found working at 200 bar and 40 °C, which corresponds to a CO2 density of 0.840 g/cm3. Operating in this way, total organic solvent residues were reduced from 13,671 ppm and 326 ppm to 12 ppm and 10 ppm for Fluni and Fluti, respectively. [ABSTRACT FROM AUTHOR]

Co-crystallization of amorphous poly(2,6-dimethyl-1,4-phenylene) oxide (PPO) films, as induced by sorption at different temperatures of many liquid guest molecules, is explored. Both for co-crystalline (CC) and corresponding nanoporous-crystalline (NC) films, kinds of and degree of planar orientation, which are relevant for their properties and applications, can be controlled by the guest sorption procedure. In particular, crystalline polymer chain orientation preferentially perpendicular to the film plane is favored by bulky guest molecules and by low guest sorption temperatures, i.e. by slow guest uptakes. Guest sorption kinetics and Scanning Electron Microscopy (SEM) support a simple mechanism that rationalizes the kinds of planar orientation of crystalline PPO chains. Slow guest uptakes imply polymer co-crystallization in spatial confinement, producing lamellae that are oriented flat-on to the film surface and hence polymer chain axes preferentially perpendicular to the film plane (c ⊥ orientation). Fast guest uptakes imply polymer co-crystallization leading to fibrils that are parallel to the film surface and hence to polymer chain axes being preferentially parallel to the film plane (c // orientation). [Display omitted] • Guest induced co-crystallization of amorphous PPO films can lead to two kinds of crystalline planar orientation (c // and c ⊥). • Guest sorption rate is the main factor determining the kind of planar orientation in PPO films. • Fast guest uptake leads to crystalline fibrils, with orientation preferentially parallel to the film surface (c //). • Slow guest uptake implies CC in spatial confinement, leading to flat-on orientation of crystalline lamellae (c ⊥). [ABSTRACT FROM AUTHOR]

• SC-CO 2 assisted drying was used to prepare RuO 2 loaded PVDF HFP aerogels. • RuO 2 nanoparticles were uniformly distributed in the polymeric matrix. • This supercapacitor exhibited a specific capacitance of 149.3 F/g and a Coulombic efficiency of 98%. • Doubling the current density, the specific capacitance reduced only of about 20%. [Display omitted] The use of a supercritical CO 2 assisted drying process for the preparation of RuO 2 nanoparticles loaded PVDF HFP aerogels is reported in this work. Morphological, mechanical, and electrochemical analyses were performed on the obtained nanocomposites, to ascertain their performance as supercapacitor devices. The supercritical process allowed a homogeneous distribution of the additive in the polymeric matrix and avoided gel shrinkage. Cycling voltammetry and charge/discharge measurements demonstrated an excellent behavior for the nanocomposites. The supercapacitor, at 60% w/w RuO 2 , exhibited a specific capacitance of 149.3 F/g at a scan rate of 10 mVs−1, and a Coulombic efficiency of 98%. Through the integration of the discharge curves, the specific capacitances were also calculated. In particular, doubling the current density, e.g., from 1.0 A/g to 2.0 A/g, the specific capacitance only reduced of about 20%. [ABSTRACT FROM AUTHOR]

• CA-Lap composite membranes were produced by scCO 2 phase inversion. • Laponite increased more than six times cellular adhesion on these CA membranes. • Laponite increased CA membranes elasticity modulus up to 4 MPa. Supercritical phase inversion was used to prepare new polymeric membranes, based on cellulose acetate and Laponite®, for tissue engineering applications. These composite membranes were characterized by a porous structure (porosity around 85%) with an average pore size ranging from about 9 to 13 μm depending on the initial weight ratio cellulose acetate/Laponite. This ratio also controlled thermal and mechanical properties of these membranes: Laponite modified membrane decomposition step and increased the membrane elasticity modulus up to 4 MPa while decreasing the percentage elongation at break from 240% to 180%. Laponite also increased material cells adhesion: thanks to its homogeneous inclusion into the membranes, a remarkable cells adhesion of around 80%, six times higher than the original material, was obtained. [ABSTRACT FROM AUTHOR]

A new nanodevice based on gold nanoparticles (AuNPs) capped with poly(diethylvinylphosphonate) (PDEVP) has been synthesized, showing interesting photophysical and thermoresponsive properties. The synthesis involves a properly designed Yttriocene catalyst coordinating the vinyl-lutidine (VL) initiator active in diethyl vinyl phosphonate polymerization. The unsaturated PDEVP chain ending was thioacetylated, deacetylated, and reacted with tetrachloroauric acid and sodium borohydride to form PDEVP-VL-capped AuNPs. The NMR, UV-Vis, and ESI-MS characterization of the metal nanoparticles confirmed the formation of the synthetic intermediates and the expected colloidal systems. AuNPs of subnanometric size were determined by WAXD and UV-Vis analysis. UV-Vis and fluorescence analysis confirmed the effective anchoring of the thiolated PDEVP to AuNPs. The formation of 50-200 nm globular structures was assessed by SEM and AFM microscopy in solid state and confirmed by DLS in aqueous dispersion. Hydrodynamic radius studies showed colloidal contraction with temperature, demonstrating thermoresponsive behavior. These properties suggest potential biomedical applications for the photoablation of malignant cells or controlled drug delivery induced by light or heat for the novel PDEVP-capped AuNP systems.

Theranostics is a growing field that matches diagnostics and therapeutics. In this approach, drugs and techniques are uniquely coupled to diagnose and treat medical conditions synergically or sequentially. By integrating diagnostic and treatment functions in a single platform, the aim of theranostics is to improve precision medicine by tailoring treatments based on real-time information. In this context, lipid-based nanocarriers have attracted great scientific attention due to their biodegradability, biocompatibility, and targeting capabilities. The present review highlights the latest research advances in the field of lipid-based nanocarriers for cancer theranostics, exploring several ways of improving in vivo performance and addressing associated challenges. These nanocarriers have significant potential to create new perspectives in the field of nanomedicine and offer promise for a significant step towards more personalized and precise medicine, reducing side effects and improving clinical outcomes for patients. This review also presents the actual barriers to and the possible challenges in the use of nanoparticles in the theranostic field, such as regulatory hurdles, high costs, and technological integration. Addressing these issues through a multidisciplinary and collaborative approach among institutions could be essential for advancing lipid nanocarriers in the theranostic field. Such collaborations can leverage diverse expertise and resources, fostering innovation and overcoming the complex challenges associated with clinical translation. This approach will be crucial for realizing the full potential of lipid-based nanocarriers in precision medicine.

Cannabigerol's (CBG) therapeutic effects are limited by its poor water solubility and low dissolution rate. To improve these properties, supercritical CO 2 -assisted atomization (SAA) was applied to produce coprecipitates, i.e., CBG nanoparticles coprecipitated in polyvinylpyrrolidone (PVP) microparticles. The experiments were performed by varying the CBG/PVP mass ratio (R) and the overall concentration of solutes CBG+PVP to study the influence of these parameters on particle morphology, particle size, and size distribution. Periodic dynamic light scattering (DLS) analysis was performed at regular time intervals to measure the size of CBG nanoparticles in PVP microparticles. It showed that CBG nanoparticles down to 105 nm were successfully produced through SAA. Dissolution tests were used to verify that a reduction of CBG particle size significantly increased its dissolution rate. In the liquid medium adopted, untreated CBG powder was released in 210 min, whereas CBG nanoparticles of 105 nm were completely dissolved in only 15 min.

Bone tissue engineering (BTE) is the most promising strategy to repair bones injuries and defects. It relies on the utilization of a temporary support to host the cells and promote nutrient exchange (i.e., the scaffold). Supercritical CO 2 assisted drying can preserve scaffold nanostructure, crucial for cell attachment and proliferation. In this work, agarose aerogels, loaded with hydroxyapatite were produced in view of BTE applications. Different combinations of agarose concentration and hydroxyapatite loadings were tested. FESEM and EDX analyses showed that scaffold structure suffered from partial closure when increasing filler concentration; hydroxyapatite distribution was homogenous, and Young's modulus improved. Looking at BTE applications, the optimal combination of agarose and hydroxyapatite resulted to be 1% w / w and 10% w / v , respectively. Mechanical properties showed that the produced composites could be eligible as starting scaffold for BTE, with a Young's Modulus larger than 100 kPa for every blend.

Niosomes are arousing significant interest thanks to their low cost, high biocompatibility, and negligible toxicity. In this work, a supercritical CO 2 -assisted process was performed at 100 bar and 40 °C to produce niosomes at different Span 80/Tween 80 weight ratios. The formulation of cholesterol and 80:20 Span 80/Tween 80 was selected to encapsulate vancomycin, used as a model active compound, to perform a drug release rate comparison between PEGylated and non-PEGylated niosomes. In both cases, nanometric vesicles were obtained, i.e., 214 ± 59 nm and 254 ± 73 nm for non-PEGylated and PEGylated niosomes, respectively, that were characterized by a high drug encapsulation efficiency (95% for non-PEGylated and 98% for PEGylated niosomes). However, only PEGylated niosomes were able to prolong the vancomycin release time up to 20-fold with respect to untreated drug powder, resulting in a powerful strategy to control the drug release rate.

One of the most effective strategies to fight viruses and handle health diseases is vaccination. Recent studies and current applications are moving on antigen, DNA and RNA-based vaccines to overcome the limitations related to the conventional vaccination strategies, such as low safety, necessity of multiple injection, and side effects. However, due to the instability of pristine antigen, RNA and DNA molecules, the use of nanocarriers is required. Among the different nanocarriers proposed for vaccinal applications, three types of nanovesicles were selected and analysed in this review: liposomes, transfersomes and niosomes. PubMed, Scopus and Google Scholar databases were used for searching recent papers on the most frequently used conventional and innovative methods of production of these nanovesicles. Weaknesses and limitations of conventional methods (i.e., multiple post-processing, solvent residue, batch-mode processes) can be overcome using innovative methods, in particular, the ones assisted by supercritical carbon dioxide. SuperSomes process emerged as a promising production technique of solvent-free nanovesicles, since it can be easily scaled-up, works in continuous-mode, and does not require further post-processing steps to obtain the desired products. As a result of the literature analysis, supercritical carbon dioxide assisted methods attracted a lot of interest for nanovesicles production in the vaccinal field. However, despite their numerous advantages, supercritical processes require further studies for the production of liposomes, transfersomes and niosomes with the aim of reaching well-defined technologies suitable for industrial applications and mass production of vaccines., (© 2024. The Author(s).)

Exopolysaccharides, obtained from microorganisms as fermentation products, are interesting candidates for biomedical applications as scaffolds: they are biocompatible, nontoxic, antimicrobial, antitumor materials. To produce exopolysaccharide-based scaffolds, sol-gel technology could be used, which ends with the removal of the liquid phase from the polymeric network (i.e., the drying step). The aim of this review is to point out the most relevant strengths and weaknesses of the different drying techniques, focusing attention on the production of exopolysaccharide-based porous structures. Among these drying processes, supercritical carbon dioxide-assisted drying is the most promising strategy to obtain dried gels to use in the biomedical field: it produces highly porous and lightweight devices with outstanding surface areas and regular microstructure and nanostructure (i.e., aerogels). As a result of the analysis carried out in the present work, it emerged that supercritical technologies should be further explored and applied to the production of exopolysaccharide-based nanostructured scaffolds. Moving research towards this direction, exopolysaccharide utilization could be intensified and extended to the production of high added-value devices.

A global release model is proposed to study the drug release from porous materials for pharmaceutical applications. This model is defined by implementing a compartmental model where the release profile could be explained as the combination of mass transfer phenomena through three compartments as well as a desorption process or dissolution process from the support. This model was validated with five different systems produced with supercritical CO 2 (aerogels, membranes, and fibers), showing different release processes. Numerical results indicate that this compartmental approach can be useful to determine adsorption and desorption constants as well as mass transfer resistances within the material. Likewise, this model can predict lag phases and imbibition phenomena. Therefore, the development of compartmental models can be an alternative to traditional models to successfully predict the drug profile of porous materials, achieving a complete understanding of the involved phenomena regardless of the material characteristics., (Copyright © 2022 The Author(s). Published by Elsevier B.V. All rights reserved.)

In this work, the effect of two processes, i.e., freeze-drying and supercritical CO 2 (SC-CO 2 ) drying, on the final morphology of agarose-based porous structures, was investigated. The agarose concentration in water was varied from 1 wt% up to 8 wt%. Agarose cryogels were prepared by freeze-drying using two cooling rates: 2.5 °C/min and 0.1 °C/min. A more uniform macroporous structure and a decrease in average pore size were achieved when a fast cooling rate was adopted. When a slower cooling rate was performed instead, cryogels were characterized by a macroporous and heterogenous structure at all of the values of the biopolymer concentration investigated. SC-CO 2 drying led to the production of aerogels characterized by a mesoporous structure, with a specific surface area up to 170 m 2 /g. Moreover, agarose-based aerogels were solvent-free, and no thermal changes were detected in the samples after processing.

Chitosan aerogels were obtained after using supercritical carbon dioxide to dry physical hydrogels, studying the effect of the rheological behavior of hydrogels and solutions on the final aerogels properties. An increase on the solutions pseudoplasticity increased the subsequent hydrogels physical entanglement, without showing a significant effect on aerogels morphology (nanoporous) and textural properties (pores of about 10 nm). However, an increase of hydrogel physical entanglement promoted the formation of aerogels with a higher compressive strength (from 0.2 to 0.80 MPa) and higher thermal decomposition range, while decreasing the porosity (from 90 % to 94 %). Aerogels stress-strain responses were also successfully fitted using a hyperelastic equation with three adjustable parameters (Yeoh), showing that this type of models must be taken into account when large stresses are studied., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Antimicrobial composite membranes, formed by cellulose acetate loaded with AgNO 3 particles, were produced by supercritical phase inversion. Different cellulose acetate concentrations were tested (15%, 20%, 30%( w / w )), whereas the active agent (i.e., silver nitrate) concentration was fixed at 0.1%( w / w ) with respect to the quantity of polymer used. To determine the influence of the process parameters on membranes morphology, the pressure and temperature were varied from 150 to 250 bar and from 55 to 35 °C, respectively. In all cases, regularly porous membranes were produced with a uniform AgNO 3 distribution in the membrane matrix. Silver release rate depended on membrane pore size, covering a time interval from 8 to 75 h.

Energy density, safety, and simple and environmentally friendly preparation methods are very significant aspects in the realization of a compact supercapacitor. Herein we report the use of a supercritical CO 2 -assisted gel drying process (SC-CO 2 ) for the preparation of porous electrodes containing dispersed graphene in a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) binder membrane to sandwich in a new portable supercapacitor based on graphene oxide (GO). A GO loading of 60 wt.% was found to give the best combination of factors (porosity, wettability, mechanical and electrochemical properties). Cycling voltammetry and charge/discharge studies showed an excellent capacitance behaviour and stability in an ionic liquid electrolyte, suggesting SC-CO 2 processing as a promising platform to produce highly bulky and porous films for supercapacitors. The supercapacitor device delivers a very high energy density of 79.2 Wh kg -1 at a power density of 0.23 KW kg -1 (current density 0.5 A g -1 , specific capacitance 36.2 F g -1 ) while that of steel remains at 50.3 Wh kg -1 at a power density of 2.8 KW kg -1 (current density 6 A g -1 , specific capacitance 23.5 F g -1 ).