Engenharia Química
URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/25
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8 resultados
Resultados da Pesquisa
- DSC analysis of the influence of time and concentration of Stryphnodendron adstringens extract on corneal cross-linking(2022-11-11) BERSANETTI, P. A.; MARQUINI, A. A.; Andreia de Araújo Morandim Giannetti© 2022, Akadémiai Kiadó, Budapest, Hungary.Keratoconus is an ectasia that leads to reduced stiffness of the cornea, which acquires a conical shape. Many studies are being carried out aiming at new treatments that lead to the recovery of these cross-links. Therefore, the efficiency of the Stryphnodendron adstringens butanolic extract in promoting cross-linking in corneal stroma of porcine eyes was analyzed. The influence of concentration of this plant extract to form cross-links was analyzed, as well as the influence of the contact time. The denaturation temperature results obtained for corneas treated with 1, 2, or 4% of the barbatimão butanolic extract show an increase of 3.84, 11.37, and 33.23%, respectively. These results suggest a rise in the number of cross-links. As for the contact time of the cornea with the 2% solution of the butanolic extract, it appears that the ideal time was 60 min. Enzymatic digestion assays confirm a decrease of 39% and 59% in the relative area and relative mass of corneas in the control group, while for the group treated with the barbatimão extract, these values were close to 0% and 9%, respectively. Therefore, it was possible to verify the efficiency of the barbatimão butanolic extract in modifying the stroma of porcine corneas, which promoted an increase in resistance to thermal and enzymatic degradation.
- DSC evaluation of cross-link development induced by laccases in corneas(2022-11-25) Andreia de Araújo Morandim Giannetti; CARVALHO, T. S.; DE ANDRADE NETO, J. C.; BERSANETTI, P. A.© 2022, Akadémiai Kiadó, Budapest, Hungary.Several studies have been developed aiming at new treatments for ophthalmological problems such as keratoconus, an eye disease that leads to the reduction of cross-links between the corneal collagen fibrils. Corroborating these studies, this work evaluated the increase of cross-linking in enucleated porcine eyes treated with catechin in the presence of laccase. The ideal conditions for the treatment of the cornea to promote the development of cross-links were determined through the application of a design of experiments. The input variables were the concentration of laccase and the reaction temperature, and the output variable was the enthalpy of corneal denaturation. The DSC results show that the ideal laccase concentration was 8.0 mg mL−1 and the temperature was 36.0 °C. The catechin concentration used was 5.0 mg mL−1. This condition led to a 10.8% increase in the denaturation temperature and a 110.3% increase in the denaturation enthalpy. Enzymatic degradation tests showed that within 24 h of digestion the group treated with laccase in the presence of catechin was more resistant compared to the control group. A decrease of 34.7 and 55.6% in the relative area and relative mass of corneas in the control group was verified, while for the group treated with laccase these values were 41.7 and 8.5%, respectively.
- High-pressure densities and derived properties of binary {methyl tert-butyl ether (MTBE) + alcohols} mixtures(2018) Hauk D.B.; Torres R.B.© 2017, Akadémiai Kiadó, Budapest, Hungary.In this study, density of binary liquid mixtures of {methyl tert-butyl ether (MTBE) + ethanol, or + 1-propanol, or + 1-butanol} has been determined as a function of composition at temperature 290 K and pressure up to 35 MPa. Densities data were measured using an Anton Paar DMA 4500 vibrating tube densimeter coupled to an external Anton Paar DMA HP high-pressure cell. A Tait equation was used to correlate experimental densities with pressure. The experimental results have been used to calculate the derived volumetric properties such as excess molar volumes (VmE), apparent molar volumes (Vϕ i), partial molar volume (V¯ i) and isothermal compressibility (κT). The thermodynamic results suggest that the structural effects and intermolecular interactions must outweigh other possible effects present in the mixtures studied.
- Thermodynamic properties of binary mixtures of n-butylammonium-based ionic liquids with ethanol at T = (293.15–313.15) K(2019) Bittencourt S.S.; Hoga H.E.; Torres R.B.; d'Angelo J.V.H.© 2018, Akadémiai Kiadó, Budapest, Hungary. In this study, density, speed of sound and viscosity of binary mixtures of ionic liquids + ethanol have been measured as a function of composition at T = (293.15–313.15) K and atmospheric pressure. The ionic liquids studied were: {n-butylammonium acetate (N4Ace), n-butylammonium propanoate (N4Pro), n-butylammonium hexanoate (N4Hex), and n-butylammonium decanoate (N4Dec)}. Excess molar volume, VmE, deviation in isentropic compressibility, Δ κ S , deviation in viscosity, Δ η, and excess Gibbs energy of activation of viscous flow, Δ G ∗ E , were obtained from experimental results and correlated with the Redlich–Kister polynomial equation. Ionic liquids were synthesized and characterized using 1 H-NMR, 13 C-NMR and FTIR spectroscopy techniques. For all systems studied, the values of VmE, Δ κ S and Δ η were negative over the entire composition range, whereas Δ G ∗ E values were positive over the entire composition range. The results obtained were discussed in terms of structural effects and intermolecular interactions between like and unlike molecules.
- DSC characterization of enzymatic digestion of corneas treated with plant extracts rich in polyphenols(2019) Bersanetti P.A.; da Cruz L.G.I.; Carlstron R.; Schor P.; Morandim-Giannetti A.A.© 2019, Akadémiai Kiadó, Budapest, Hungary.Keratoconus is a progressive disease that affects patients’ quality of life by producing corneal irregular astigmatism and low vision as the cornea becomes thinner and presents a conical protrusion. Inducing cross-linking in keratoconic corneal stroma is the current preventive intervention that effectively blocks the progression of this ectasia. As a result of this process, there is an increase in biomechanical strength and resistance of the cornea. In this context, two plant extracts rich in polyphenols (Euterpe oleracea and Stryphnodendron adstringens) have been tested in this study to compact and stiffen the tissue, and its effect was evaluated by enzymatic digestion of porcine corneas. Thermal analysis by DSC was employed to verify the corneal resistance to degradation induced by the plant extracts. The values of temperature and enthalpy of denaturation at the initial time were: 65.6 ± 0.3 °C/3.8 ± 0.3 J g−1; 79.4 ± 0.5 °C/5.5 ± 0.4 J g−1; and 93.1 ± 1.2 °C/8.0 ± 0.6 J g−1, respectively, for the control, E. oleracea, and S. adstringens groups. After 24 h of collagenase digestion, these values were: 60.1 ± 0.8 °C/1.3 ± 0.1 J g−1; 78.1 ± 1.0 °C/5.6 ± 0.6 J g−1; and 93.2 ± 0.6 °C/8.1 ± 0.06 J g−1, respectively. These results show that there was no decrease in temperature and enthalpy of denaturation (p < 0.01) in corneas of the groups treated with the E. oleracea or S. adstringens extracts. However, in the control group, the temperature and the enthalpy decreased by approximately 8% and 65%, respectively. Therefore, this work demonstrated for the first time that plant extracts rich in polyphenols were efficient in decreasing the digestion and increasing the denaturation temperature of corneas.
- Attainment and characterization of carboxymethyl chitosan hydrogels by enzymatic cross-linking(2019) Morandim-Giannetti A.A.; Wecchi P.O.; Silverio P.A.; Carlstron R.; Bersanetti P.A.© 2019, Akadémiai Kiadó, Budapest, Hungary.In this study, carboxymethyl chitosan hydrogels (CMCH) cross-linked with catechin in the presence of laccase (CMCH-C-L) were obtained. The synthesis and characterization of CMCH were carried out from chitosan (CH) and its cross-linking with catechin (C) in the presence of laccase (L). DSC, ATR-FTIR, and rheological analyses of the CMCH solution and CMCH-C-L hydrogel were carried out. Three main thermal events were observed in the DSC characterization with temperatures and enthalpies related to each event for CMCH: 167.2 °C/+ 523.3 J g−1, 269.1 °C/− 35.0 J g−1, and 333.3 °C/− 17.6 J g−1, possibly referring to these processes: polymerization, breaking of electrostatic interactions, and decomposition of the material, respectively. The CMCH-C-L hydrogel presented values of 165.2 °C/+ 376.6 J g−1, 266.7 °C/− 47.8 J g−1, and 333.3 °C/− 31.5 J g−1. Conversely, the chitosan presented only one thermal event of decomposition at 302.5 °C and enthalpy of − 258.5 J g−1. Rheological properties of the hydrogels (viscosities, consistency values, and flow indices) showed non-Newtonian pseudoplastic rheological behavior and that the viscosity increased approximately 150% after the reaction (134.25 mPa s for CMCH and 342.85 mPa s in CMCH-C-L) confirming the formation of cross-links after the addition of catechin and laccase. Morphological analyses of CMCH and CMCH-C-L films via SEM showed the modification of the material after the reaction with the catechin in the presence of laccase and corroborated with the results, confirming the presence of cross-links.
- DSC characterization of rabbit corneas treated with Stryphnodendron adstringens (Mart.) Coville extracts(2018) da Cruz L.G.I.; Moraes G.A.; Nogueira R.F.; Morandim-Giannetti A.A.; Bersanetti P.A.© 2017, Akadémiai Kiadó, Budapest, Hungary.Keratoconus is an eye ectasia that affects the cornea causing distortion of vision. Corneal crosslinking promoted by riboflavin photo-stimulated at 365 nm is a treatment used successfully to block the keratoconus progression. In this study, we characterize rabbit corneas subjected to enhanced crosslinking using different vegetable extracts prepared from Stryphnodendron adstringens (Mart.) Coville bark by differential scanning calorimetry. The extracts tested in this study were: aqueous, ketonic, ethanolic, ethyl acetate and hydroalcoholic, which revealed high levels of polyphenols, such as proanthocyanidins. The corneas, obtained from the slaughter rabbits, were divided into groups: control (consisting of untreated corneal samples) and S. adstringens, where the samples were subjected to 4% vegetable extracts for 2 h. The DSC profiles of the corneas were obtained in nitrogen atmosphere. The results showed that temperature and enthalpy of denaturation of the corneal samples treated with S. adstringens were higher than the control group. The control group presents temperature and enthalpy values of 59.8 ± 1.1 °C and 24.6 ± 2.7 J g−1, respectively. After crosslinking with ketone extract, the values were 90.1 ± 1.1 °C and 39.9 ± 2.7 J g−1. These results show that S. adstringens is efficient to increment the crosslinking level of the corneas.
- Thermodynamic and spectroscopic study of binary mixtures of n-butylammonium oleate ionic liquid + alcohol at T = 288.15–308.15 K(2018) Olivieri G.V.; da Cunha C.S.; dos Santos Martins L.; Paegle P.A.M.; Nuncio S.D.; de Araujo Morandim-Giannetti A.; Torres R.B.© 2017, Akadémiai Kiadó, Budapest, Hungary.In this study, experimental data of density and speed of sound have been measured for binary liquid mixtures containing {n-butylammonium oleate (N4Ol) ionic liquid + 1-propanol, or + 1-butanol, or + 1-pentanol, or + 1-hexanol}, over the entire range of composition at temperatures from T = 288.15–308.15 K and atmospheric pressure. Excess molar volume, VmE, and deviation in isentropic compressibility, Δκ, were calculated using the experimental data and were fit to a Redlich–Kister type polynomial. In order to elucidate possible intermolecular interactions between the chemical species present in solution, FT-IR and 1H-NMR spectroscopic analyses were carried out. The results for all systems studied suggest that structural effects and dispersion-type interactions must predominate other possible effects.