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Predloženo tehničko rešenje opisuje tehnološki postupak za dobijanje aerogelova skroba velike poroznosti. Ovim tehničkim rešenjem prevazilaze se ekološki problemistvaranja i akumulacije otpada. Aerogelovi su proizvedeni od biokompatibilnih materijalaiz obnovljivih izvora upotrebom zelenog medujuma (natkritičnog ugljen(IV)-oksida). Zeleni medijum se u potpunosti uklanja iz finalnog proizvoda i može da se reciklira nakon proizvodnje materijala.Predloženim tehnološkim postupkom proizvodnje omogućava se ušteda vremena i energije za proizvodnju polisaharidnih aerogelova koji imaju poroznost do 82%.Dobijeni aerogelovi se mogu upotrebiti u medicini za tretiranje vlažnih rana jer apsorbuju do 420% okolne tečnosti.Vlažne rane proizvode značajnu količinu eksudata ili tečnosti i njihov tretman je ključan za promovisanje pravilnog zarastanja i sprečavanje infekcija. Dodatno,usled biodegradabilnosti skroba korišćenjem proizvedenih aerogelova izbegava se akumulacija otpada nakon upotrebe istog.

Due to the high use and misuse of antibiotics over the years, microbes have developed resistance to a significant number of drugs (so-called antimicrobial resistance - AMR) [1]. Therefore, the necessity for the development of natural antimicrobial agents to overcome growing bacterial resistance against synthetic antibiotics has been recognized. Thymol is a natural monoterpenoid, with proven anti-inflammatory, antioxidant, and antimicrobial properties and it has been recognized as safe by the FDA (it has GRAS status). With the aim to fabricate material with antibacterial activity, supercritical solvent impregnation (SSI) was applied for loading of commercial PLA-based absorbable surgical sutures with thymol in a green medium, supercritical CO2. Operating temperature and pressure were set to 35 °C and 10 MPa, while contact time was varied between 1 and 6 h. The SSI process was performed under mild processing parameters to obtain an effective amount of loaded thymol against tested bacteria keeping in mind the recommended safe content of thymol for human blood cells (in terms of cytotoxicity and mutagen effect) [2]. Selected process conditions enabled thymol loadings of 3.9–5.6% (Fig. 1) [3]. SEM analyses was used to monitor sutures' morphological change from swelling to agglutination induced by the increased amount of thymol in the material. ...

The supercritical fluid extraction (SFE) technique that employs supercritical carbon dioxide (SC-CO2) has been reported to be superior (compared to mechanical and extractions with organic solvents) for the separation of oils from seeds [1]. Current work aims to show that besides oils, additional valuable extracts can be recovered from defatted seeds. For that purpose, seeds of milk thistle, dandelion and chamomile grown in Poland have been tested. Initially, SFE for oil separation from seeds was tested by variation in pressure (from 100 to 450 bar) and temperature (from 40 to 80 °C) [2–4]. The yield and composition of oils indicated optimal conditions for the separation of extracts from defatted seeds using SC-CO2 with ethanol. ...

Predloženo tehničko rešenje opisuje tehnološki postupak za dobijanje antimikrobnih aerogelova skroba. Bioaktivni materijala su proizvedeni primenom ekološki prihvatljivih tehnika upotrebom zelenog medujuma (natkritičnog ugljen(IV)-oksida), biokompatibilnih i biorazgradivih materijala iz obnovljivih izvora i prirodnih bioaktivnih jedinjenja. Zeleni medijum se u potpunosti uklanja iz finalnog proizvoda i može se reciklirati nakon proizvodnje. Proizvedeni aerogelovi skroba sa timolom, eugenolom, karvakrolom i citronelolom (12,815,8 mass%) pokazuju jaku antimikrobnu aktivnost. Dobijeni aerogelovi se mogu upotrebiti u medicini za tretiranje inficiranih rana jer apsorbuju do 265 do 569% okolne tečnosti i inhibiraju rast Gram-negativnih bakterija, Gram-pozitivnih bakterija i gljivica (veličina prečnika zone inhibicije je do 37,5 mm). Predmetno tehničko rešenje pokazuje obećavajući zeleni pristup za proizvodnju bioaktivnih dvokomponentnih materijala na bazi skroba za potencijalnu primenu u lečenju infekcija kože. Ovim rešenjem prevazilaze se ekološki problemi stvaranja otpada prilikom proizvodnje bioaktivnih materijala i korišćenjem proizvedenog materijala izbegava se akumulacija otpada nakon upotrebe.

Aerogels are materials with high specific surface area and high porosity, which can be produced from polysaccharides such as starch [1,2]. Starch is an abundant and low-cost polymer with versatility in processing. Aerogel properties are influenced by the process parameters including starch-to-water ratio, gelatinization temperature (T), selection of non-solvent for water replacement in hydrogels, selection of drying method, drying pressure (P) and T, etc. [1,2]. Supercritical drying, which employs supercritical carbon dioxide (scCO2), is an environmentally friendly process that allows relatively fast production of aerogels. Despite the superior properties of starch aerogels, they do not express biological activity. This can be overcome by the incorporation of bioactive compounds (BCs) into aerogels using the supercritical impregnation (SCI) process [3,4]. SCI implies the dissolution of BCs in scCO2, diffusion of BC-scCO2 solution into a polymer matrix, possible chemical or physical interaction of BC with polymer, and complete removal of scCO2 from the BC-polymer after a decrease of P and T to atmospheric. This process allows one-step production of solvent-free added value materials at relatively low T and the incorporation of high amounts of BC with various biological activities. Aerogels can be impregnated with pharmaceutical drugs but also with natural BCs (single or mixture) such as plant extracts [3,4]. To produce aerogels, 10 g of cornstarch (amylose content 20−30%, HeMoss, Serbia) was mixed with 100 mL of distilled water, gelatinization T was changed from 70 to 100 °C, water contained in hydrogels was replaced with acetone or ethanol during 1 or 5 days, drying P was varied from 8 to 20 MPa while drying T was 35 or 40 °C. Drying of gels was performed in a 25 mL high-pressure view cell while impregnation of aerogels with BCs was performed in a 280 mL high-pressure unit (Eurotechnica GmbH, Germany). Developed aerogels were tested as possible carriers of hemp and

The Polymer group of the Faculty of Technology and Metallurgy University of Belgrade deals with environment-sensitive hydrogel as carriersfor biomedical applications, including drug delivery, wound healing, and regenerative medicine. The first hydrogel generation synthesized in our labs was discs made of polyacrylamide and its derivatives. The synthesis was at higher temperatures (50 °C), with traditional crosslinker, N, N’-methylenebisacrylamide, and persulphate/pyrosulphate as initiator. Due to the growing demands for environmental sustainability, the general approach changed to reduce petrochemical raw materials and prepare eco-friendly materials focusing on 1) renewable polymers, initiators, and crosslinkers and 2) the application of simple, cost-effective, and eco-friendly approaches in hydrogel synthesis. To obtain the second hydrogel generation, we use renewable polymers: polysaccharides, proteins, and polyhydroxyalkanoates [1]. Still, the mechanical strength was weak. Hence, the applicationof carboxylic acids, methacrylic and itaconic, and N-isopropyl acrylamide improves mechanical properties and enhances the environmental stimuli of the carriers. Instead of traditional crosslinkers -organic molecules, we gave the advantage to plant extracts like genipin, sodium tripolyphosphate, citric acid, and calcium chloride. We made beads, microgels, aerogels, discs, films, and cylinders sensitive to pH, temperature, magnetic field, or specific molecules such as glucose. Facing an everyday challenge, improving drug delivery routes, especially for poorly water-soluble drugs, and finding an alternative to traditional antibiotics, encapsulation, and controlled release remain a challenge. Therefore, we used a mild condition (e.g., deep coating) to encapsulate/release traditional water-soluble and poorly water-soluble drugs, proteins, phenolic compounds, or supercritical carbon dioxide (scCO2) for thymol, carvacrol, and eugenol, a promising alternative for traditional antib

Investigations of the process of supercritical fluid extraction (SFE) from dandelion were so far mainly focused on extractions from herb, leaves and root [1-3]. In the work presented here, the extraction process from seeds was investigated on a laboratory and semi-industrial scale equipment. The milled plant material with an average particle size of 0.41 ± 0.02 mm was used in all experiments. All SFEs were conducted with carbon-dioxide in supercritical state (SCCO2) as a solvent on pressure of 450 bar and temperature of 60°C, as these parameters were previously shown to be optimal for obtaining high-value extracts from dandelion seeds [4]. Experiments were conducted on laboratory (dia.=7.7 cm, vol=0.56 l, CO2 flow=11 kg/h) and semiindustrial (dia.=23.5 cm, vol.=397 l, CO2 flow=240 kg/h) scale equipment. On both scales several experiments were conducted with initial mass of the plant material (Ms) being the only variable parameter: laboratory scale Ms=26–104 g; semi-industrial scale Ms=2.2–8.8 kg. Fractions of extract were collected during the extractions in order to obtain data on the kinetics of the SFE processes. The results of the performed experiments are depicted in Figure 1. It can be seen that for both scales the rate of SFE, as well as the final yield, increases with increase of the mass of plant material, indicating that with the selected conditions, namely flowrate of CO2, the residence time was not long enough to allow saturation of the CO2 in the first part of the process, nor to enable extraction of all available extract. Similar trends on both scales can be perceived as a good basis for further investigations aiming at scale-up of the process of SFE from dandelion seeds. Experiments with larger packed bed height, which would enable higher residence times, should be conducted in order to achieve saturation at least in the first part of the SFE process. Mathematical models of the SFE process, supported by models for estimation of the kinetic parameters

Supercritical carbon dioxide (sc-CO2) has remarkable attributes as a processing medium such as high diffusivity, low viscosity, non-flammability, and inertness. In addition, it can be easily and completely separated from the final material, as well as fully recycled. This sets up sc-CO2-assisted technologies apart from conventional methodologies reliant on organic solvents. Some of the most prominent techniques that employ sc-CO2 are supercritical drying and supercritical impregnation for the functionalization of polymeric nanofibers, textiles, films, foams, and aerogels. Supercritical drying can be employed for the separation of liquids from wet polymer gels and the production of highly porous dry aerogels, while supercritical impregnation can be employed for the incorporation of bioactive components into polymer matrices. Overall, sc-CO2 technologies pioneer the development of next-generation materials while meticulous physical and chemical characterizations underpin the scientific journey.

The main aim of this study was to evaluate chamomile seeds as a new source of valuable bioactive compounds. For this purpose, a green extraction technique was employed with supercritical carbon dioxide (sc-CO2) as a solvent and ethanol as a co-solvent. The extracts from chamomile seeds with an average particle size of 0.20 mm were extracted at pressures of 30 and 45 MPa and temperatures of 40 and 60 °C. The composition of extracts was investigated by a gas chromatography-mass spectrometry analytical method as well as Folin−Ciocalteu assay (for total phenolic content) and total flavonoid content test. The antioxidant activity of obtained chamomile extracts was evaluated using DPPH radical. The antimicrobial effect of extracts was tested on yeasts, Gram-positive, and Gram-negative bacteria while the cytotoxic effect was evaluated on normal and cancer cells. The extraction process parameters were evaluated and results showed a significant effect of operating pressure, temperature, and the addition of co-solvent on the amount of separated chamomile extract and its composition. The extraction yield ranged from 2.1 to 5.4% and extracts contained high amounts of unsaturated fatty acids. The addition of ethanol as a co-solvent (40 w/w%) had a slight influence on total phenolic and flavonoid contents increasing their values from 29.1 to 31.5 mg GAE/g and from 2.1 to 4.2 mg QE/g, respectively. The obtained supercritical chamomile extracts showed antioxidant activity achieving values of IC50 around 10 mg/mL. The antimicrobial activity of extracts was most pronounced against Bacillus subtilis. Extracts did not show cytotoxic activity against normal cells. Overall, results indicated a significant potential of extracts from chamomile seeds, produced in an environmentally friendly manner, to be used as a functional food or phytopharmaceuticals.

Green technologies refer to a type of technology that is environmentally friendly based on its production process or its supply chain (i.e resources). Green tech also refers to clean energy production, use of alternative fuels, and processes that are less harmful to the environment compared to ones with fossil fuels. The focus of this presentation is: 1) Processing of polymers obtained from renewable resources that are recyclable and/or biodegradable, 2) Use of environmentally friendly techniques for the preparation of advanced materials (dry porous forms).

Bilberries (Vaccinium myrtillus) have been used in traditional medicine to reduce inflammation and protect against diseases associated with oxidative stress, such as cardiovascular disease, diabetes, and age-related cognitive decline, as well as a remedy for eye conditions. The biological activity of bilberries is ascribed mainly to their high content of anthocyanins, but also to other valuable phytochemicals, including flavonols, phenolic acids, and tannins [1,2]. The enhanced stability and bioavailability of bioactive components from plant material could be accomplished by their incorporation into a polymeric carrier, using the promising integrated processes of supercritical fluid extraction (SFE) and supercritical solvent impregnation (SSI). ...

Natural compounds found in different plant extracts can show numerous biological activities and be used as health promoters. For instance, thymol, carvacrol, citronellol, and eugenol (found in extracts of thyme, oregano, lemongrass, and clove, respectively) can be used as anti-inflammatory, antiviral, and antimicrobial agents [1- 4]. The high volatility of the mentioned natural bioactive compounds (NBCs), which restricts their broader application, can be managed by the incorporation of NBCs into polymer matrices. Therefore, intending to develop devices that release antimicrobial substances in a controlled manner, this study tested the applicability of the supercritical solvent impregnation (SSI) technique for the incorporation of NBCs into starch aerogels. First, the hydrogels were prepared from corn starch. The water in the hydrogels was replaced by ethanol, and the obtained alcogels were dried using the supercritical drying (SCD) technique. The parameters of the aerogels` preparation were optimized previously [5].Later, SSI was performed at 150 bar and 35 °C for 2 h. The obtained materials were analyzed using FTIR, to determine the potential interactions between the NBCs and polymer that could determine the rate of controlled release and antimicrobial activity. Controlled release of NBCs from the aerogels was tested in phosphate-buffered saline solution at 37 °C. ...

Interest in the separation of green tea extracts continues to grow due to its significant bioactivity, wide applicability as well as a large number of green tea spices, variety of extraction techniques, and lack of systematic data. The present early stage work was intended to estimate the effect of temperature and co-solvent addition on an amount of separated constituents from green tea (gunpowder tea variety, China) during the supercritical carbon dioxide (sc-CO2) extraction process. For this purpose, the temperature of the supercritical extraction process was increased up to 90 °C at a constant pressure of 30 MPa. After the selection of appropriate conditions, co-solvents (ethanol, ethanol/water, and water) were added to sc-CO2. Obtained extracts were analyzed regarding total phenolic content (TPC), total flavonoid content (TFC), DPPH radical scavenging activity, total chlorophyll, and total carotenoid content. The results of the supercritical extraction process were compared with the conventional extraction process (extraction using Soxhlet apparatus). The results showed that a linear decrease in the density of neat sc-CO2 led to a linear increase in extraction yields up to 5.5%. The addition of co-solvents had a variable effect on the amount of separated extracts. While it increased extraction yields at a lower temperature, it decreased extraction yields at a higher temperature. An increase in temperature for the extraction process with neat sc- CO2 also decreased TPC, TFC, chlorophylls, and carotenoids content. The addition of co-solvents to sc-CO2 increased amounts of tested compounds in obtained extracts. It was interesting to notice a decrease in the amount of tested compounds with an increase in water content during extractions. The highest values of TPC and TFC detected were 136.5 mg GAE/g and 40.7 mg QE/g, respectively. Extract solutions with a concentration of 20 mg/mL inhibited up to 65% of DPPH radical. Chlorophyll A, chlorophyll B, and carotenoids wer

This review provides a concise overview of up-to-date developments in the processing of neat poly(lactic acid) (PLA), improvement in its properties, and preparation of advanced materials using a green medium (CO2 under elevated pressure). Pressurized CO2 in the dense and supercritical state is a superior alternative medium to organic solvents, as it is easily available, fully recyclable, has easily tunable properties, and can be completely removed from the final material without post-processing steps. This review summarizes the state of the art on PLA drying, impregnation, foaming, and particle generation by the employment of dense and supercritical CO2 for the development of new materials. An analysis of the effect of processing methods on the final material properties was focused on neat PLA and PLA with an addition of natural bioactive components. It was demonstrated that CO2-assisted processes enable the control of PLA properties, reduce operating times, and require less energy compared to conventional ones. The described environmentally friendly processing techniques and the versatility of PLA were employed for the preparation of foams, aerogels, scaffolds, microparticles, and nanoparticles, as well as bioactive materials. These PLA-based materials can find application in tissue engineering, drug delivery, active food packaging, compostable packaging, wastewater treatment, or thermal insulation, among others.

This study investigates pharmaceutical polymers (Soluplus®, HPMCAS, and Eudragit® E100) and supercritical CO2-assisted process for preparation of floating valsartan delivery systems. Tested process (at pressure of 30 MPa and temperature of 100 °C during 2 h) enabled preparation of stable porous valsartan formulations which was confirmed with FESEM and mercury intrusion porosimetry analysis. The bulk density of obtained formulations was lower than 550 kg/m3. FTIR, DSC, and PXRD analysis indicated that there was no chemical interaction between the drug and polymers and that amorphous solid dispersions were obtained. Formulations with Soluplus® and HPMCAS retained its buoyancy in 0.1 M HCl for longer than 24 h, while formulation with Eudragit® E100 retained its buoyancy up to 2 h. Controlled valsartan release was influenced by solubility of polymers in the tested release medium, which was confirmed by UV/VIS spectroscopy. The obtained results provided framework for further development of floating drug delivery system using an environmental friendly process.