Effect of starch xero‐ and aerogels preparation on the supercritical CO₂ impregnation of thymol

Abstract

In this study, for the first time, the supercritical solvent impregnation (SSI) technique has been used to test the incorporation of thymol into starch gels. Corn and tapioca starch hydrogels prepared at different temperatures (70–100°C) were converted to the acetogels and subsequently dried with supercritical CO2 or air to obtain aero‐ or xerogels, respectively. Starch xero‐ and aerogels were impregnated with thymol in a high pressure view cell using supercritical CO2 at 15.5 MPa and 35°C during 24 h. The influence of the botanical origin of starch, temperature for hydrogels preparation (Tgel‐h) and drying method on the gel morphology and thymol impregnation yields was discussed. Determined thymol SSI yields were in the range of 1.15–4.02% for the corn and 0.58–3.63% for the tapioca starch gels. Xerogels had higher thymol loading capacities (1.76–4.02%) than aerogels (0.58–3.31%) at given SSI conditions. Gel morphology and thymol SSI yields were positively affected by the Tgel‐h increase. The xerogel obtained from the corn starch hydrogel prepared at 100°C had the largest specific surface area (5.52 m2/g) and thymol loading capacity (4.02%) at given SSI conditions. These results, along with a simple and low‐cost production, indicated the great potential of the corn starch xerogel for commercial use as a carrier in pharmaceuticals and nutraceuticals.

Cellulose Acetate Based Material with Antibacterial Properties Created by Supercritical Solvent Impregnation

“…Process of supercritical solvent impregnation (SSI) implies dissolution of an additive in supercritical fluid and its subsequent incorporation into a polymer matrix [1,2] which leads to formation of an added-value polymeric material. Reportedly, supercritical carbon dioxide (scCO 2 ) can be used to load polymeric carriers with antimicrobial substances [2][3][4][5][6][7][8][9][10][11][12], vitamins [13], drugs [14,15], dyes [16,17], and so on.…”

“…The first one involves simple deposition of an additive which is soluble in supercritical fluid into the polymer matrix due to decompression of the system. The second one involves impregnation of additives that have higher affinity towards the polymer and then to the supercritical fluid (due to chemical interaction between the additive and polymer) [1,2]. SSI is advantageous over conventional impregnation methods because it excludes the use of organic solvents as well as the drying step.…”

Supercritical CO2 deposition and foaming process for fabrication of biopolyester–ZnO bone scaffolds

“…Process of SCFD of Zn(TTA) 2 into PLA was performed in a high pressure unit represented schematically by Figure . The polymer (P) (0.24 ± 0.04 g) and the precursor (PR) samples (15 mg) were placed in the separate open glass receipts inside the high pressure view cell previously elsewhere . The cell was filled with CO 2 and pressurized to 30 MPa and 110 °C.…”

Desenvolvimento de aerogéis baseados em amidos para a impregnação de óleo de café verde

“…Por outro lado, Milovanovic et al (2015) produziram filmes de amido de amido de milho que exibiram baixa área superficial (0,019 m 2 /g). Estes materiais foram obtidos através de um longo processo de desidratação em acetona (5 dias) seguido por secagem supercrítica a 200 bar, 50 °C e fluxo CO2 de 0,76 L/h durante 5 horas (MILOVANOVIC et al, 2015).…”

“…Estes autores obtiveram uma eficiência de 40% para impregnação de óleo de linho em monólitos de amido de cevada β-glucano (COMIN; TEMELLI; SALDAÑA, 2012a).Por outro lado,Garcia-Gonzales et al (2015) mostraram eficiência de impregnação de 12,8% para cetoprofeno e 21,5% para ácido benzoico em microesferas de aerogel de amido de milho(GARCÍA-GONZÁLEZ et al, 2015).Outro bom exemplo foi publicado porLovskaya, Lebedev e Menshutina (2015). Estes autores mostrara, para microesferas de amido de milho uma eficiência de 30% para a impregnação de ibuprofeno e uma eficiência de 21,6% para Rifabutina (LOVSKAYA; LEBEDEV;MENSHUTINA, 2015).Em outro exemplo com uma matriz diferente,Milovanovic et al (2015) mostraram, para monólitos tipo filmes, uma eficiência de impregnação do 4% para Timol.Como resultado o fluido supercrítico apresenta uma densidade semelhante e uma difusividade maior ao do líquido e uma viscosidade semelhante ao gás, ou seja, eles têm o poder de solvatação dos líquidos e as propriedades de transporte e penetração dos gases. Por ter viscosidade mais baixa e difusividade mais alta em relação aos líquidos, a transferência de massa dos solutos da matriz sólida para o solvente supercrítico nas extrações é significativamente mais alta que nas extrações com solventes líquidos(SCHNEIDER, 1983).Assim os fluidos supercríticos são considerados solventes especiais, e uma alternativa muito atrativa para os processos de extração de matrizes sólidas.…”