Artigos
URI permanente para esta coleçãohttps://repositorio.fei.edu.br/handle/FEI/800
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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.
- 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.