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Cellulose aerogels are interesting platforms for biomedical and drug delivery applications, due to their biocompatibility, biodegradability, water absorption capacity, and good textural properties. Supercritical CO 2 drying has been proven as an efficient technology for obtaining aerogels and preserving the porous structure. In this work, the effect of relevant process variables (CO 2 density, depressurization rate, and intermediate depressurization mode) and gel composition on the textural properties of cellulose aerogels is studied. Experiments are performed in batch-mode, and aerogel monoliths are characterized in terms of apparent density, porosity, specific surface area, and crystalline morphology. Water uptake in different buffer solutions is also evaluated. The use of thiourea in the gel formation leads to lower porosity. On the other hand, higher porosity and surface area are obtained when depressurization is slow and the system is only partially depressurized between drying cycles. Aerogels showed a good and fast water uptake capacity, regardless of the pH (200–500 %). [Display omitted] • Lightweight aerogels were obtained by scCO2 drying from cellulose basic solutions. • The use of thiourea in the hydrogel led to lower porosity and specific surface area. • Partial depressurization between drying cycles helped to preserve textural properties. • Aerogels showed good water uptake capacity (200–500 %) regardless of the solution pH. [ABSTRACT FROM AUTHOR]

In this work, low density polyethylene (LDPE) films were loaded by scCO 2 -assisted impregnation with R -(−)-carvone, the main component of M. spicata and A. polystachya essential oils with antimicrobial and insecticidal activity. Impregnation runs were performed in a lab-scale high-pressure cell, and the effect of CO 2 density (240–700 kg m −3 ) and temperature (35–60 °C) on impregnation yield was evaluated. Impregnation yields of 2.0–4.8% (w/w) were obtained, achieving higher values at low CO 2 density. Thermal and mechanical properties of the films, before and after impregnation, were also investigated. The diffusion coefficient of carvone in scCO 2 -swollen films was estimated by impregnating film rolls and modeling the concentration profile through the roll thickness using an analytical solution of second Fick’s law. Release profiles into air were determined, allowing to estimate diffusivity values in non-swollen films at ambient conditions. [ABSTRACT FROM AUTHOR]

In this contribution, supercritical CO 2 -assisted impregnation of LDPE/sepiolite nanocomposite films with two insecticidal terpene ketones (thymoquinone and R -(+)-pulegone) is investigated, as a strategy to enhance the loading capacity compared to pure LDPE. A factorial experimental design was applied in order to evaluate the effect of five process variables at two levels (sepiolite content: 1–10% w/w; initial ketone mole fraction: 0.0017–0.0025; pressure: 9–13 MPa; depressurization rate: 0.5–2.0 MPa/min; time: 2–4 h) on impregnation yield, at 45 °C. ANOVA test of the results indicated that pressure, time and ketone mole fraction significantly affect impregnation yield (ranging between 2.36 ± 0.18 and 8.60 ± 1.66% w/w). Thermal analysis (DSC) and X-ray diffraction (XRD) allowed to investigate the nanocomposite morphology and the modifications induced by the impregnation. The mechanical properties of the films were assessed by stress-strain tests, showing that the impregnation process had a very low impact on the material ductility and strength. [ABSTRACT FROM AUTHOR]

In this work, the supercritical carbon dioxide impregnation of low density polyethylene (LDPE) films with a mixture of two terpenic ketones (thymoquinone and R -(+)-pulegone) with biopesticide activity is investigated, as a strategy for developing a packaging material or delivery device for protecting seeds, kernels and derivatives during storage and transport. Impregnation runs were performed according to a fractional factorial experimental design in order to evaluate the effect of four process variables at two levels (pressure: 10–15 MPa; depressurization rate: 0.5–2.0 MPa/min; time: 2–4 h; initial ketone mole fraction: 0.0017–0.0025) on impregnation yield and selectivity between ketones. Operational temperature was constant for all experiments and equal to 45 °C. The impregnated films were analyzed by infrared spectroscpy (FTIR) in order to confirm the presence of both ketones and determine their relative ratio in the final product. ANOVA test of the results indicate that contact time and ketone concentration are the only factors with significant effects on impregnation yield (ranging between 2.25 and 5.59%), while no factor seems to affect significantly the loading selectivity, with thymoquinone/pulegone ratios in the final product between 0.39 and 0.99. The insecticidal activity of impregnated film samples was evaluated in fumigant assays against corn weevil ( Sitophilus zeamais Motschulsky), a major pest of stored kernels. The films showed a high activity level during the first 2 days (∼100% mortality), which gradually decreased until showing no toxicity after 7 days. [ABSTRACT FROM AUTHOR]

In this work, linear low density polyethylene (LLDPE) films were impregnated with eugenol using supercritical CO 2 impregnation, as a strategy for obtaining a loaded material to be potentially applied in active food packaging. Eugenol, the main component of clove oil, is well known as a natural antioxidant and antimicrobial agent. Impregnation runs were performed in a lab-scale high pressure stirred cell at 45 °C during 4 h, and the effect of pressure (10, 12 and 15 MPa) and depressurization rate (0.5, 1 and 5 MPa/min) on impregnation yield was evaluated. Yields of 1–6% (w/w) were achieved, with higher values at low depressurization rate. Film samples were characterized by infra-red spectroscopy (FTIR) and differential scanning calorimetry (DSC). FTIR analysis suggested that the distribution of eugenol in the films is not totally homogeneous. DSC revealed a decrease in the crystallinity degree in the impregnated samples as well as in films subjected to pressurization with CO 2 but not loaded with eugenol. Changes in mechanical properties were also investigated in a texturometer. A decrease of LLDPE Young modulus and ductility was observed after high pressure impregnation, although tensile strength was not significantly affected. Finally, the antioxidant activity of the eugenol-loaded films was assessed via the DPPH inhibition test. [ABSTRACT FROM AUTHOR]

Biocompatible implants are essential for improving human health and longevity. Incorporating bioactive compounds, such as eugenol, into implant materials can improve biocompatibility and therapeutic efficacy. This study examines the effects of supercritical eugenol impregnation on the physical properties of 3D-printed polylactic acid samples produced by Fused Deposition Modeling. Impregnation was performed using a lab-scale high-pressure system, evaluating the impact of impregnation time on eugenol loading, distribution, and morphology. Fourier Transform Infrared spectroscopy confirmed homogeneous eugenol distribution with impregnation times exceeding 1 h, achieving loadings up to 12 wt%. Eugenol was released slowly over extended periods in a phosphate-buffered solution. Impregnated samples displayed more amorphous thermal behavior, with decreased Tg due to the plasticizing effect of the CO₂-eugenol mixture. Mechanical properties were slightly altered, with reduced stiffness and increased toughness. Microscopic deformations induced by impregnation could potentially enhance cellular adhesion, improving biocompatible material performance. [Display omitted] • Supercritical CO₂ effectively impregnates eugenol into 3D-printed PLA structures. • Eugenol loadings from 6 to 12 wt% were achieved with increased impregnation time. • The process results in a slow and controlled release of eugenol over 2 months. • Impregnation reduces PLA's stiffness up to 40 % and increases its toughness by 67 %. • Surface roughness modifications potentially enhance cell attachment for implants. [ABSTRACT FROM AUTHOR]

• CO 2 and eugenol diffusion in PA6 at supercritical conditions showed Fickian behavior. • Eugenol loading and partition coefficients were enhanced by temperature. • Apparent diffusivities of CO 2 and eugenol were approx. 10-10 and 10−14 m2s-1, respectively. • CO 2 sorption in PA6 was not affected by temperature nor pressure. • Results suggested that eugenol diffuses in an already plasticized polymeric matrix. • The high pressure process had a low impact on the crystallinity degree of PA6 fibers. In this work, mass transfer kinetics of CO 2 and eugenol into polyamide 6 (PA6) fibers under supercritical conditions were investigated in the context of the development of a functional dental floss for dental care applications using scCO 2 -assisted impregnation. The sorption kinetics was evaluated at different temperature (40 and 60 °C) and pressure conditions (10 and 12 MPa), measuring the total amount of CO 2 and eugenol incorporated in PA6 fibers after certain time intervals (from 30 min to 4 h). Equilibrium sorption was determined for all operation conditions, obtaining the highest values at low CO 2 density. Diffusion coefficients of CO 2 and eugenol under different process conditions were estimated fitting the experimental data with analytical solutions of the second Fick's law. In addition, thermal behavior of eugenol-loaded PA6 fibers impregnated at different time intervals was evaluated by differential scanning calorimetry (DSC), observing only small changes in the polymer crystallinity during the high-pressure process. [ABSTRACT FROM AUTHOR]

The loading of polymeric carriers with active pharmaceutical and nutraceutical ingredients using supercritical CO 2 (scCO 2) as solvent and diffusion enhancer has received increasing attention as an alternative for the development of active materials and delivery systems. In this contribution, recent advances in scCO 2 impregnation/deposition in the pharmaceutical, biomedical, and nutraceutical fields are reviewed, covering the period 2015–2021. The main physicochemical phenomena underlying the impregnation/deposition process (phase equilibrium, diffusion, plasticization, sorption, adsorption, etc.) are briefly presented and discussed. Applications are reviewed including drug and botanical drug products, medical devices, and dietary supplements. The effects of different process variables on the impregnation efficiency and some relevant properties of the obtained materials are also critically discussed and compared. [Display omitted] • Advances in scCO2 impregnation in pharmaceutical, biomedical, and nutraceutical fields are reviewed. • The period 2015–2021 was included and critically discussed. • Delivery systems have been mainly focused on enhancing or adjusting the drug solubility. • scCO2-assisted impregnation results useful for preserving valuable food ingredients. • Combined scCO2-based operations to improve manufacturing processes are gaining increasing attention. [ABSTRACT FROM AUTHOR]

In this work, the supercritical CO 2 -assisted impregnation of microcrystalline cellulose (MCC) particles with R -(−)-carvone, an antimicrobial monoterpene, was investigated. The effect of CO 2 density (278–600 kg m−3), temperature (40–60 °C), carvone:MCC mass ratio (0.5–1.0), and depressurization mode (cold–hot), on the impregnation yield was studied. Carvone loadings were obtained in the range of 0.6–3.6 wt%, and the addition of ethanol (2 wt%) as cosolvent enhanced the impregnation yield up to 10 wt%. The high crystallinity of cellulose (81–84%) remained unchanged after the supercritical process, although SEM analysis showed a partial separation of fiber agglomerates. Carvone release in simulated saliva solution from particles impregnated using cosolvent was slightly slower than from the pure CO 2 -impregnated particles. The observed release profile could be useful for pharmaceutical and biomedical applications, such as the prevention of oral cavity infections or their treatment at early stages. [Display omitted] • Carvone loading was influenced by all process variables and some binary interactions. • The addition of cosolvent enhanced ∼2.5-times the carvone impregnation yield. • The high crystallinity of MCC remained unchanged after the supercritical process. • Supercritical impregnation induced the rupture of MCC fibers agglomerates. • Carvone-impregnated MCC showed slower release compared to physical mixture. [ABSTRACT FROM AUTHOR]