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  • Artigo
    Biodiesel production from vegetal oil and ethanol via transesterification in supercritical conditions
    (2023-08-03) SIDI NETO, V.; DERENZO, S.; MARIN, M. P. DE A.; Luis Novazzi; João Guilherme Rocha Poço
    © 2023, The Author(s) under exclusive licence to Associação Brasileira de Engenharia Química.Biodiesel, which is derived from renewable feedstock, has potential to replace fossil diesel. In this study, biodiesel production was carried out through the transesterification of soybean oil with ethanol (anhydrous and hydrated) under supercritical conditions in a batch reactor, with a temperature range of 280–340 °C and an oil/alcohol molar ratio of 1:40. The effects of both anhydrous and hydrated ethanol on the reaction were evaluated, as well as the direct esterification of oleic acid to produce ethyl ester. A first-order reversible kinetic model was proposed to describe the transesterification process. The results showed a good agreement between experimental data and the model. It was observed that temperature has an important effect on ester yield and hydrated ethanol improved this yield. After 120 min of reaction time at 310 °C with hydrated ethanol, transesterification led to 89.7% of ethyl ester. When compared to anhydrous ethanol, forward rate constants of hydrated ethanol suggested that water may have a catalytic effect on transesterification. Although the transesterification of soybean oil and ethanol under supercritical conditions is nearly irreversible at 280 °C, the reaction is limited by equilibrium at temperatures equal to or higher than 310 °C.
  • Artigo
    Intraspecific variability of dihydrochalcone, chromenes and benzoic acid derivatives in leaves of Piper aduncum L. (Piperaceae)
    (2009-05-18) Andreia de Araújo Morandim Giannetti; KATO, M. J.; CAVALHEIRO, A. J.; FURLAN, M.
    Chemical analysis carried out in leaves of 18 specimens of Piper aduncum L. (Piperaceae) occurring at Ripasa Reserve, Araraquara, SP, Brazil indicated two distinct populations when investigated over a period of 14 months (January 2000 to February 2001) and then submitted to cluster analysis. The two groups were characterized by accumulation of prenylated benzoic acids, chromenes and dihydrochalcone, respectively. A total of seven compounds were identified by HPLC analysis and compared with standards including two prenylated benzoic acid [aduncumene (1) and 3-(3′-7′-dimethyl-2′-6′-octadienyl)- 4-methoxy-benzoic acid (5)], four chromenes [methyl 2,2-dimethyl-8-(3′- methyl-2′-butenyl)-2H-1-chromene-6-carboxylate (4), methyl 2,2-dimethyl-2H-1-chromene-6-carboxylate (2b), methyl 8-hydroxy-2,2-dimethyl-2H- 1-chromene-6-carboxylate (3) and 2,2-dimethyl-2H-1-chromene-6-carboxylic acid (2a)] and one dihydrochalcone [2′,6′-dihydroxy-4′-methoxy- dihydrochalcone (6)]. © 2009 Academic Journals.
  • Artigo
    Development of highly resistant fibers for use in solid phase micro extraction (SPME)
    (2010-01-05) RODRIGUES, J. C.; LEITE, D. W.; LANCAS, F. M.
    The commercially available fibers for solid-phase microextraction (SPME) made of optical fibers are fragile and can be easily broken. Thus, there is a clear need for the development of efficient, simple and highly resistant SPME fibers. This work describes the preparation of highly resistant fibers in which a polymer is coated onto an open tubular fused silica capillary tubing (0.360 mm O.D.) fitted with a stainless steel wire (0.200 mm O.D.) previously inserted and cemented into the capillary tube opening to guarantee higher mechanical resistance. The fiber was coated with 70-μm poly (dimethyl siloxane) (PDMS) and evaluated for the extraction of polycyclic aromatic hydrocarbons.
  • Artigo
    Composition and screening of antifungal activity against Cladosporium sphaerospermum and Cladosporium cladosporioides of essential oils of leaves and fruits of Piper species
    (2010-09-05) Andreia de Araújo Morandim Giannetti; PIN, A. R.; PIETRO, N. A. S.; ALECIO, A. C.; KATO, M. J.; YOUNG, C. M.; OLIVEIRA, J. E. DE; FURLAN, M.
    This study investigated the composition and antifungal activity against Cladosporium sphaerospermum and Cladosporium cladosporioides of essential oils of leaves of Piper cernuum, Piper diospyrifolium, Piper crassinervium, Piper solmsianum and Piper umbelata and fruits of P. cernuum and P. diospyrifolium. The essentials oils were analyzed by GC-MS and submitted of the antifungal activity tests. The essential oils of fruits from P. cernuum and leaves of P. crassinervium and P. solmsianum showed potential antifungal activity against C. sphaerospermum and C. cladosporioides. In addition, this is the first report of the composition of essential oils of fruits of P. cernuum and P. diospyrifolium. © 2010 Academic Journals.
  • Artigo
    Composition and antifungal activity against candida albicans, candida parapsilosis, candida krusei and cryptococcus neoformans of essential oils from leaves of piper and peperomia species
    (2010-09-04) Andreia de Araújo Morandim Giannetti; PIN, A. R.; PIETRO, N. A. S.; OLIVEIRA, H. C. DE; MENDES-GIANNINI, M. J. S.; ALECIO, A. C.; KATO, M. J.; OLIVEIRA, J. E. DE; FURLAN, M.
    This study was addressed to investigate the composition and antifungal activity of essential oils from leaves of Piperaceae species (Piper aduncum, Piper amalago, Piper cernuum, Piper diospyrifolium, Piper crassinervium, Piper gaudichaudianum, Piper solmsianum, Piper regnellii, Piper tuberculatum, Piper umbelata and Peperomia obtusifolia) against Candida albicans, C. parapsilosis, C. krusei and Cryptococcus neoformans. The essential oils from P. aduncum, P. gaudichaudianum and P. solmsianum showed the highest antifungal activity against Cryptococcus neoformans with the MIC of 62.5, 62.5 and 3.9 mg.mL-1, respectively. The oil from P. gaudichaudianum showed activity against C. krusei with MIC of 31.25 mg.mL-1. © 2010 Academic Journals.
  • Artigo
    Study of salmonella typhimurium mutagenicity assay of (z)-piplartine by the ames test
    (2011-06-15) Andreia de Araújo Morandim Giannetti; Cotinguiba F.; REGASINI, L. O.; FRIGIERI, M. C.; VARANDA, E. A.; COQUEIRO, A.; KATO, M. J.; BOLZANI, V. S.; FURLAN, M.
    Phytochemical studies carried out with Piperaceae species have shown great diversity of secondary metabolites among which are several displayed considerable biological activities. The species Piper tuberculatum has been intensively investigated and a series of amides have been described. For instance, (E)-piplartine showed significant cytotoxic activity against tumor cell lines, especially human leukemia cell lines; antifungal activity against Cladosporium species; trypanocidal activity and others. Considering the popular use of P. tuberculatum and the lack of pharmacological studies regarding this plant species, the mutagenic and antimutagenic effect of (Z)-piplartine was evaluated by the Ames test, using the strains TA97a, TA98, TA100 and TA102 of Salmonella typhimurium. No mutagenic activity was observed for this compound. © 2011 Academic Journals.
  • Artigo
    Effects of caramelization and Maillard reaction products on the physiology of Saccharomyces cerevisiae
    (2023-01-05) ELIODORO, K. P.; PENNACCHI, C.; DE GOIS E CUNHA, G. C.; Andreia de Araújo Morandim Giannetti; GIUDICI, R.; BASSO, T. O.
    © 2023 British Mycological SocietyThe thermal treatment the sugarcane juice undergoes during its processing alters the medium's chemical composition through the so-called Maillard reactions and its products, which can affect the alcohol-producing yeast's physiology in steps following the processing. This study aims to describe and characterize the reactivity of the primary amino acids present in sugarcane with sucrose, as well as demonstrate the physiological effects of the reaction's products on the yeast Saccharomyces cerevisiae. The main amino acids in sugarcane (glutamine, asparagine, and aspartic acid) were chosen to be reacted with sucrose under similar conditions to the industrial sugarcane processing (pH 5 and temperature 100–120 °C). The physiological effect of Maillard and caramelization reaction on the S. cerevisiae CEN.PK-122 and PE-2 strains were tested in microplate experiments using a modified mineral media containing both the reacted and unreacted amino acid-sucrose systems and four modified synthetic molasses media. The results have shown that the presence of any amino acids drastically increases product formation. Furthermore, among the amino acids, aspartic acid was the most reactive. Meanwhile, asparagine and glutamine had similar results. In S. cerevisiae physiology, aspartic acid had the most significant effect on culture growth by reducing the maximum specific growth rate and optical density. The increase in the Maillard product concentration for synthetic molasses also evidenced the inhibitory effect on yeast growth compared to media in the absence of these products. We conclude that this initial investigation clarifies the inhibitory effect of the Maillard products on yeast physiology.
  • Artigo
    Direct oxidation of 3-picoline (3-methyl-pyridine) to nicotinic acid with pure HNO3
    (2023-07-17) GOMES, E. L.; FREITAS, D. A. DE; Rodrigo Condotta; João Guilherme Rocha Poço
    © 2023, The Author(s) under exclusive licence to Associação Brasileira de Engenharia Química.Nicotinic acid (NA) was synthesized by directly oxidizing 3-methylpyridine (3MP) with nitric acid. The reaction was performed in an instrumented PARR reactor. The effect of temperature (165 to 195 °C) and the molar composition of the initial reactive mixture were studied. Molar conversions of 3-methylpyridine ranged from 36 to 90%, with a yield of NA ranging from 31 to 62%. Better selectivities occur at low-time reactions and low conversion rates. At the same time, the HNO3 excess and temperature considerably affect 3MP conversion rate and NA yield rather than selectivity, especially at 180 °C, whereas an invariable selectivity of 80% was observed.
  • Artigo
    Measurement and correlation of high-pressure volumetric properties of binary mixtures of 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][NTf2]) with alcohols
    (2023-10-05) HAUK, D. B.; Ricardo Torres; DANGELO, J. V. H.
    © 2023 Elsevier LtdNew experimental data for density-pressure–temperature measurements of binary mixtures of {1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][NTf2]) + methanol, or + ethanol or + 1-propanol} have been measured using a vibrating tube densimeter at temperatures from T = (298.15 to 308.15) K and pressure range p= (0.1 – 40) MPa. The experimental density results have been correlated by the Tait-Tammann equation with the temperature and composition dependence parameters. The effects of the increase in the alkyl chains of the alcohols, temperature, and pressure on the density and volumetric properties have been analyzed. Moreover, the Extended Real Associated Solution Model (ERAS Model) has been used to correlate the experimental behavior of the excess molar volume of the studied systems.
  • Artigo
    Fe3O4 nanoparticles and Rhizobium inoculation enhance nodulation, nitrogen fixation and growth of common bean plants grown in soil
    © 2020 Elsevier B.V.The effects of Fe3O4 nanoparticles (NPs) and Rhizobium inoculation on nodulation, nitrogen fixation and plant growth of common bean (cv. Red Guama, Phaseolus vulgaris) plants were investigated in growth chambers. Plants were exposed to: Fe3O4 NPs (2000 mg/L) (T1), Rhizobium inoculation (T2) and Fe3O4 NPs + Rhizobium inoculation (T3); non-treated plants were considered as controls. Harvested 35-day-old treated plants showed improved symbiotic performance including increased nitrogenase activity (51.2–90.7%), nodule leghaemoglobin (44.8–80.9%) and iron content (83.4–84.2%), number of active nodules per plant (58.7–122%) and nodule dry weight (40.2–70.6%). This resulted in enhanced symbiotic nitrogen fixation,and increased shoot (26.5–50.2%) and root (24.1–48.2%) total nitrogen content in treated plants in comparison with the controls. The best result was obtained using treatment T3. Furthermore, Fe3O4 NPs were taken up by bean plants in treatments T1 and T3, and these accumulated in their organs, including in nodules. All treatments led to an increase in root (51.9–79.8%) and shoot (27.5–52.7%) lengths, in leaf area (10.9–16.8%) and in root (10.1–17.8%), stem (9.8–12.7%) and leaf dry weight (8–17.3%) compared to control plants. Thus applied treatments have the potential to improve common bean plant growth through enhancement of nodulation and nitrogen fixation during vegetative growth.This study also provides strong evidence that the presence Fe3O4 NPs in nodules improves the symbiotic performance between Rhizobium (leguminosarum CF1 strain) and the common bean plant, due to enhanced nodulation and nitrogen fixation.
  • Artigo
    Heterogeneous catalyzed isomerization of turpentine oil by ordered mesoporous materials like M41S structures
    (2022-07-05) SOUSA, L. B. DE; SPERANZA, J. T.; Rodrigo Condotta; Rodrigo Cella
    © 2022 Canadian Society for Chemical Engineering.Herein, the synthesis of a structure with a porous system similar to that of molecular sieves, MCM-41 and 48 types, with the incorporation of heteroatoms in their synthesis, is reported. The catalytic activity of these materials was tested in the isomerization reaction of turpentine oil to obtain camphene. The best results were obtained with Zn-Al-Si-MCM, a mesoporous material, with a conversion of up to 96% and selectivities of 31% and 22% to camphene and 4-carene, respectively, both of which are bicyclic products. The recycling of the catalyst was also tested, and after three cycles, no significant loss of activity was observed.
  • Artigo
    Biocompatibility of polyvinyl alcohol/trisodium trimetaphosphate as vitreous substitute in experimental vitrectomy model in rabbits
    (2022-02-05) OLIVEIRA, R. A. DE; MURALHA, F. P.; GRUPENMACHER, A. T.; Andreia de Araújo Morandim Giannetti; BERSANETTI, P. A.; MAIA, M.; MAGALHÃES JUNIOR, O.
    © 2021 Wiley Periodicals LLC.Synthetic hydrogels have been proposed as vitreous substitutes recently. This study aims to evaluate the biocompatibility of polyvinyl alcohol (PVA) crosslinked with trisodium trimetaphosphate (SMTP) hydrogel in rabbit vitrectomized eyes. Seven animals were submitted to pars plana vitrectomy and the vitreous was replaced by PVA/SMTP hydrogel. Optical coherence tomography, fluorescein angiogram, clinical, and electrophysiological (ERG) examinations were analyzed at baseline, on postoperative days 7 and 30. The fellow eye was used as the control group. Hydrogel opacification was observed and ERG recordings were reduced in the hydrogel group in rod response, b-wave cone response and flicker. A histological analysis showed retinal disorganization, presence of multinucleated cells, and intraretinal hydrogel particles. The PVA/SMTP hydrogel showed poor biocompatibility. Novel biomaterials compounds should be analyzed in vivo.
  • Artigo
    Experimental study and correlation of the excess molar volume of binary liquid solutions of (amines + water) at different temperatures and atmospheric pressure
    (2022-03-05) MUNOZ, P. A. R.; OLIVIERI, G. V.; Ronaldo Santos; Ricardo Torres
    © 2021, Associação Brasileira de Engenharia Química.Experimental data of density have been measured for binary liquid mixtures containing {amines (n-butylamine, or s-butylamine, or t-butylamine, or diethylamine, or propylamine) + water}, over the entire range of composition at temperatures between 283.15 and 303.15 K, and atmospheric pressure. The density values enabled the determination of the thermal expansion coefficients. The excess molar volume, VmE, was calculated using the experimental data, from which a Redlich–Kister type polynomial was fit, enabling the determination of the partial molar volumes, the excess partial molar volumes, the apparent molar volumes and the excess partial molar volumes at infinite dilution. The VmE values were also used to test the applicability of the Extended Real Associated Solution Model (ERAS Model). The results for the studied systems suggest that structural effects and chemical interactions must predominate over other possible effects. The magnitude of VmE for the studies systems led to the following order: n-butylamine > propylamine > s-butylamine > diethylamine > t-butylamine.
  • Artigo
    Synthesis of carboxymethylcellulose from corn straw waste: comparison between pre-treatments with sodium hydroxide and low-cost ionic liquid
    (2022-03-05) BESSA, B. G.; SANTOS, H. P. DOS; MURAKAMI, V. T.; FANTIM, W. M.; BERGAMO, Y. DE. C.; Andreia de Araújo Morandim Giannetti
    © 2021, Iran Polymer and Petrochemical Institute.In this work, the possibility of using corn straw to obtain carboxymethylcellulose (CMC) was verified. However, to obtain CMC from lignocellulosic residues, it is necessary to carry out initial treatments to reduce the levels of lignin and hemicellulose. In this context, studies have been conducted to enable the use of an ionic liquid (IL). The n-butylammonium acetate was used to treat the straw instead of the pulping stage for the subsequent attainment of CMC. For comparison, we determined the composition of the resulting material after the stages of NaOH pulping (NaP) or treatment with the IL (at 80 °C—ILP80 and 120 °C—ILP120) and bleaching, to analyze the purity of the cellulose obtained. It was also possible to verify that the treatment at 120 °C was more effective to remove inorganic materials and lignin, leading to cellulose with 91.45 ± 0.11% purity when compared with its treatment at 80 °C. CMC was successfully synthesized and presented similar morphologies accordingly. Consequently, the attainment of CMC was confirmed by analyzing the data obtained via FTIR, NMR, and XRD techniques, as well as the analyses of degree of substitution. It was also possible to recover the ionic liquid at a purity of 95.93%. Graphical abstract: [Figure not available: see fulltext.]
  • Artigo
    Spectrophotometric Analysis of Different Polymethyl Methacrylate Filters and their Importance in the Implantation of Corneal Rings
    (2023-04-24) RODRIGUES, P. F.; MOSCOVICI, B. K.; HOEHNE, J. L.; CAMPOS, M. S. D. Q.; Andreia de Araújo Morandim Giannetti; BERSANETTI, P. A.; NOSE, W.
    © 2023 Taylor & Francis Group, LLC.Purpose: This study evaluated the luminous behavior applied to materials used in intraocular surgeries. Methods: Discs of the different products were delivered in 19.00 mm × 3.00 mm. Each sample was fixed on support keeping it perpendicular to the spectrophotometer beam. Later, their analyses were carried out in the air/PMMA ratio. The graphs of individual profiles of the measurements along the length were constructed according to each of the filters from the spectrophotometric analysis. In addition, descriptive statistics of transmittance and absorbance for each wavelength presented were correlated for each filter. Results: It is possible to observe that the minimum absorption measure was found in the Red Filter, especially in the blue and green light spectrum. Conclusion: Using filters in PMMA materials appears to improve visual quality in corneal implants, especially the red filter, due to greater absorbance of light leading to fewer light scattering phenomena through corneal rings. However, further studies comparing the effects of different filters on Intracorneal rings should be carried out to elucidate this field of study.
  • Artigo de evento
    Safety Related Development of a PEM Fuel Cell Supply and Control System
    (2023-02-05) BRUNO, B. F.; IBUSUKI, U.; URIEL, G. J.; Gerhard Ett (ETT, G.)
    © 2021 SAE International.Although the proton exchange membrane fuel cell (PEMFC) is still attracting enormous R&D interest because of its high energy density, its commercialization is hampered by many challenges including cutting cost, improving performance and increasing durability. While they could be solved by material selection, the durability of PEMFC is also affected by voltage reversals and fuel starvation. [1] Despite the problems related to the construction of the fuel cell, there are also problems in terms of safety. In the development chain of a technology, it is essential to take into account the origin of the materials used for their maintenance / after-sales. Knowing that hydrogen is a gas that has several peculiarities and among them the high combustion power, great attention is needed when handling it and therefore there is a sequence of good practices and standards to be respected from which will be discussed in this article.
  • Artigo de revisão
    Metal–organic frameworks as catalysts and biocatalysts for methane oxidation: The current state of the art
    (2023-04-05) ANDRADE, L. S.; LIMA, H. H.L. B.; SILVA, C. T. P.; AMORIM, W. L. N.; João Guilherme Rocha Poço; LOPEZ-CASTILLO, A.; KIRILLOVA, M. V.; CARVALHO, W. A.; KIRILLOV, A. M.; MANDELLI, D.
    © 2023 Elsevier B.V.As the main component of natural and shale gas, seabed clathrates, and biogas, methane (CH4) is an abundant C1 resource for added-value chemicals. CH4 is of critical importance to society as a universal and renewable (biogas) fuel, but it is also a potent greenhouse gas that causes global warming and climate change. Given such a multifaceted occurrence and uses of CH4, the research on its chemical transformations with environmental and sustainability significance represents a frontier direction of modern chemistry that can address many societal challenges. Metal-organic frameworks (MOFs) and derived materials received outstanding attention because of unique features such as structural versatility and tunability, low density, high porosity, and giant specific surface area, which all contributed to their auspicious applications in heterogeneous catalysis. With regard to methane, MOFs are unique and very promising materials for CH4 storage, separation, sensing, and various types of catalytic transformations. The main goal of this work consisted in surveying all the existing literature on the heterogeneous selective oxidation of methane catalyzed by MOFs, aiming at describing the current state of the art and highlighting other aspects, challenges, and perspectives closely relevant to this research area. This review thus focuses on the application of MOFs and their bioinspired or biomimetic analogs (bioMOFs) as heterogeneous catalysts for the selective oxidation of methane. The review is divided into logical sections: (i) methane sources, (ii) current status in methane oxidation, (iii) natural biochemical and enzymatic methane oxidation reactions and their relevance for inspiring the design of advanced catalysts as bioMOFs, (iv) methane oxidation reactions mediated by enzyme-mimicking bioMOFs, (v) MOFs as porous supports for catalytically active species and their catalytic use in methane oxidation, and (vi) computational chemistry toward unveiling MOF-catalyzed methane oxidation mechanisms and predicting prospective catalytic systems. This study will contribute to the advancement and future development of new MOF-based catalytic systems for various methane reactions as a frontier direction of modern chemistry and sustainable catalysis.
  • Artigo
    Molecular interactions of (ionic liquid butylammonium methanoate + alcohols) at several temperatures. Part II: sec-Butylammonium methanoate (S4Met)
    (2023-04-05) HOGA, H. E.; FERNANDES, R. L.; OLIVIERI, G. V.; Ricardo Torres
    © 2022 Elsevier LtdVolumetric and acoustic properties were obtained by density (ρ) and speed of sound (u) experimental values for the binary liquid systems containing the protic ionic liquid (IL) sec-butylammonium methanoate (S4Met) + alcohols (ethanol, 1-propanol, 1-butanol and 1-pentanol) over the whole composition range at different temperatures (293.15–313.15) K and ambient pressure (p = 92.3 kPa). A neutralization reaction was carried out under controlled temperature to synthesize S4Met, which underwent spectroscopic analyses to guarantee its formation. All the excess properties, namely excess molar volume,VmE, excess partial molar volumes,V¯iE, and deviation in isentropic compressibility,ΔκS, presented negative values. Other volumetric properties such as partial molar volumes,V¯i, apparent molar volumes, Vϕi and infinite dilution volumes,V¯i∞, were determined. In addition to the thermodynamic approach, spectroscopy techniques essentially 1H NMR, 13C NMR, FTIR were useful in order to elucidate intermolecular interactions among the species in solutions. Lastly, the Peng-Robinson-Stryjek-Vera equation of state (PRSV EOS) was used to correlate the excess molar volumes.
  • Artigo
    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.
  • Artigo
    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.