Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 966
Filtrar
1.
Plant Sci ; 335: 111791, 2023 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-37451549

RESUMO

The greatest threat to profitable peach production is cold damage to reproductive tissues. To better understand and mitigate cold damage in peach accurate and efficient assessment of floral bud cold hardiness (Hc) is critical. Differential thermal analysis (DTA) was optimized for efficient and precise detection of low-temperature exotherms (LTE) created by the freezing of supercooled intracellular water in peach floral primordia to determine Hc weekly during the dormant season. DTA-estimated lethal temperatures (LT) were validated against the standard oxidative browning method (OB) and in situ field damage following three freezing events. Chilling (0-7.2 °C) accumulation tracked throughout the dormant season to determine DTA-related changes across dormancy phase transitions. LTEs showed rapid acclimation of 'Redhaven' peach floral buds following the first frost of the dormant season (Tmin=-6.8 °C on November 18, 2016) and maintained similar Hc levels for 45 days through maximum Hc (LT50 =-23.9 °C recorded on January 9, 2017) and until the accumulation of 868 chilling hours was reached. Following this milestone, a significant 55% loss of LTEs upon the accumulation of the first growing degree day (Tbase=7 °C) was recoded on February 7, 2017. An LTE recovery approach, pre-exposing buds to a non-freezing low temperature (-2°C) for a period of 12 h, more than doubled the number of LTEs detected for another 27 days extending DTA use for LT prediction. The results presented herein confirm that the use of DTA is efficient and accurate to determine Hc in peach floral buds, and suggest that the LTE loss in early spring may be a signature response related to the shift from endo- into ecodormancy following two environmental temperature cues, chilling satisfaction and the first heat accumulation post chilling satisfaction.


Assuntos
Prunus persica , Temperatura , Temperatura Baixa , Água , Análise Diferencial Térmica
2.
Int J Biometeorol ; 66(5): 987-994, 2022 May.
Artigo em Inglês | MEDLINE | ID: mdl-35124758

RESUMO

The frequency and severity of spring frosts increase during the budburst in many regions of the world as global warming increases. Variability in the freezing resistance of sweet cherry flower organs during the active growing period has been rarely documented, especially in regard to the sepal, pedicel, receptacle, petal, stamen, and pistil organs of flower at the deacclimation stage. The freezing resistance of flower organs of six sweet cherry cultivars was investigated at regular intervals from the first white stage through the full bloom stage using differential thermal analysis (DTA) for 2019-2020. For most of the cultivars, petal and stamen organs of flower exhibited higher freezing resistance than other flower organs. There were significant differences in frost tolerance among cultivars, and 'Van' and 'Wild Genotype' had a lower level of low temperature exotherms or critical temperatures (LT50 values) in both stages, whereas 'Merton Late' was more sensitive to frost than other cultivars. Additionally, an increase in LT50 values in all cultivars was observed with the progression of the budburst. The results in the present study can increase the certainty of decision-making regarding the timing and methods to increase the air temperature in orchards during spring frost events to prevent frost damage. Larger data sets are required to further validate our results, and future efforts should thus be focused on determining the critical temperatures of flower organs using different measurement techniques.


Assuntos
Prunus avium , Temperatura Baixa , Análise Diferencial Térmica , Flores , Temperatura
3.
J Fluoresc ; 32(2): 613-627, 2022 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-35020114

RESUMO

Six crimson samarium (III) complexes based on ß-ketone carboxylic acid and ancillary ligands were synthesized by adopting the grinding technique. All synthesized complexes were investigated via elemental analysis, infrared, UV-Vis, NMR, TG/DTG and photoluminescence studies. Optical properties of these photostimulated samarium (III) complexes exhibit reddish-orange luminescence due to 4G5/2 → 6H7/2 electronic transition at 606 nm of samarium (III) ions. Further, energy bandgap, color purity, CIE color coordinates, CCT and quantum yield of all complexes were determined accurately. Replacement of water molecules by ancillary ligands enriched these complexes (S2-S6) with decay time, quantum yield, luminescence, energy bandgap and biological properties than parent complex (S1). Interestingly, these efficient properties of complexes may find their applications in optoelectronics and lighting systems. In addition to these, the antioxidant and antimicrobial assays were also investigated to explore the applications in biological assays.


Assuntos
Complexos de Coordenação/síntese química , Equipamentos e Provisões , Luminescência , Dispositivos Ópticos , Samário/química , Anti-Infecciosos/farmacologia , Antioxidantes/farmacologia , Colorimetria , Complexos de Coordenação/química , Análise Diferencial Térmica , Transferência de Energia , Samário/farmacologia , Análise Espectral
4.
Eur J Pharm Biopharm ; 169: 125-133, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34655768

RESUMO

Understanding drug miscibility in pharmaceutically relevant systems is essential for the development and optimisation of pharmaceutical dosage forms. This is particularly true for film forming systems which are designed to become supersaturated with drug, following application on the skin surface, whilst maintaining the physical stability of the drug for a suitable period to enhance drug delivery. For such formulations, chemical penetration enhancers as well as the drug are absorbed from the formulation into the skin, making understanding drug delivery from the films challenging. This study investigated the use of an optical differential scanning calorimetry (DSC) to understand drug miscibility in polymeric film forming systems and explain drug transport behaviour from film forming formulations, containing ibuprofen, a copolymer based on dimethylaminoethyl methacrylate, butyl methacrylate, and methyl methacrylate (Eudragit® E, EuE), a copolymer based on ethyl acrylate, methyl methacrylate and methacrylic acid ester with quaternary ammonium groups (Eudragit® RS, EuRS) and a copolymer based on methacrylic acid and methyl methacrylate (Eudragit® S, EuS), with and without the chemical penetration enhancer propylene glycol, across a model membrane. The optical DSC enabled the rapid screening of not only drug-polymer miscibility, but also drug-vehicle miscibility, while considering both the melting-point depression and melting enthalpy of the drug due to the presence of the polymer/polymer-based vehicle, obtained via thermal analysis by structural characterisation (TASC) and DSC analysis, respectively. The results obtained enable the polymers studied to be ranked in the order of EuE > EuRS > EuS, with EuE being more miscible with ibuprofen, and the incorporation of a penetration enhancer in the film forming system formulation was found to increase ibuprofen solubility in EuE- and EuRS- based films. The drug-polymer/vehicle miscibility information obtained via optical DSC provided understanding of drug transport from film forming systems with the higher miscibility of ibuprofen with EuE reducing drug transport through decreasing drug saturation in the film. The higher drug transport from films containing EuRS and EuS could also be linked to drug miscibility with the polymer and showed dependence on ibuprofen loading in the formulation. Overall optical DSC has been demonstrated to be a valuable tool for determining drug-vehicle miscibility for pharmaceutical product development.


Assuntos
Varredura Diferencial de Calorimetria/métodos , Sistemas de Liberação de Medicamentos/métodos , Ibuprofeno/farmacologia , Ácidos Polimetacrílicos/farmacologia , Administração Tópica , Anti-Inflamatórios não Esteroides/farmacologia , Química Farmacêutica/métodos , Análise Diferencial Térmica/métodos , Composição de Medicamentos/métodos , Liberação Controlada de Fármacos , Humanos , Absorção Cutânea/efeitos dos fármacos , Solubilidade
5.
Pak J Pharm Sci ; 34(2(Supplementary)): 657-663, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-34275799

RESUMO

Risperidone is an atypical antipsychotic agent clinically used to treat schizophrenia, bipolar diseases, and autism. Usually, the frequency of doses is twice daily. In the present study, risperidone controlled release matrices formulated using hydrophilic and hydrophobic polymers. The tablets were prepared by direct compression. The pre-compression and post-compression properties were assessed, along with swelling studies. The morphology of particles observed using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). The stability study on the drug was performed using thermal gravimetric analysis (TGA) and differential thermal analysis (DTA). The optimized formulation was prepared with the help of hydrophilic polymer K100M (40% ratio). Furthermore, release kinetics had investigated. The release pattern of optimized formulation FT5 fitted best to zero-order kinetics and showed excellent release characteristics. The model-independent approach had been used, formulations FT6 and FT8 showed resemblance with FT5 in all three media, respectively. The once daily formulation of risperidone could be beneficial for schizophrenia patients and their caregivers and will improve patient compliance.


Assuntos
Antipsicóticos/uso terapêutico , Risperidona/uso terapêutico , Esquizofrenia/tratamento farmacológico , Antipsicóticos/administração & dosagem , Antipsicóticos/farmacocinética , Preparações de Ação Retardada , Análise Diferencial Térmica , Liberação Controlada de Fármacos , Estabilidade de Medicamentos , Humanos , Cinética , Microscopia Eletrônica de Varredura , Risperidona/administração & dosagem , Risperidona/farmacocinética , Espectroscopia de Infravermelho com Transformada de Fourier , Comprimidos , Termogravimetria
6.
Int J Biometeorol ; 65(7): 1125-1135, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-33611681

RESUMO

Many studies to date on the response of cherry flower buds to frost have focused on visual evaluations by observing tissue browning after frost event in the orchard and laboratory conditions but only little knowledge is available on the consequences of intracellular ice formation on cellular ultrastructure that underlies exothermic reactions during bud burst stages. In this study, the differential thermal analysis (DTA) method was used to investigate critical frost temperatures for the sweet cherry cultivars '0900-Ziraat', 'Erzincan Macar', 'Lambert', 'Vista', 'Stella', and 'Early Burlat' under laboratory-based freeze assays. In the course of our experimental study, frost tolerance or cell death points (CDPs) of flowers of six cherry cultivars were investigated in consecutive phenological stages from the start to the end of blooming, for 2 years. The frost tolerance of flower buds changed according to different developmental stages and cherry cultivars. Our results of frost tolerance tests performed on the cherry blooming stages are rather controversial. Our findings have shown that at the open cluster stage, the frost tolerance of the flower buds is very sensitive (mCDP = -1.18°C for 'Lambert'), while the first white stage has revealed an important increase (mCDP= -9.96°C for '0900-Ziraat') in the frost tolerance of those. Averaged over 2 years, the temperatures causing 50% frost damage for flower buds were -2.08 to -3.76°C at the side green stage, -1.49 to -3.22°C at the green tip stage, -1.18 to -1.98°C at the open cluster stage, -7.92 to -9.96°C at the first white stage, and -6.29 to -9.36°C at the full bloom stage in the range of six cultivars. Based on our test results, '0900-Ziraat' and 'Vista' were regularly classified as frost-tolerant cultivars. The flower buds of 'Lambert' and 'Early Burlat' have been regularly the most sensitive, while 'Erzincan Macar' and 'Stella' were ranked into the group of medium sensitivity. These results can help farmers to estimate possible frost damages on sweet cherry flower buds due to frost events at the investigated phenological stages.


Assuntos
Prunus avium , Análise Diferencial Térmica , Flores , Congelamento , Temperatura
7.
ACS Appl Bio Mater ; 4(2): 1369-1380, 2021 02 15.
Artigo em Inglês | MEDLINE | ID: mdl-35014488

RESUMO

In this paper, three different mass fractions of sodium carbonate were used for degumming to obtain different degrees of damaged silk fibroin fibers, which were then treated with formic acid to shrink and bond them into 3D scaffolds. The structure and performance of silk fibroin fibers and silk fibroin 3D scaffolds were characterized by scanning electron microscopy, infrared spectroscopy, X-ray diffraction, a differential thermal scanner, a universal materials testing machine, and laser confocal microscopy, and the degradation performance was tested by protease degradation. The results showed that an excessive mass fraction of sodium carbonate would cause partial hydrolysis of fibroin fibers, decrease the mechanical properties of fibroin fiber, increase the surface roughness of fibroin fibers, and make mouse embryonic fibroblasts easier to adhere and grow. Silk fibroin fibers were slightly dissolved, shrunk, and dispersed in formic acid. The mass fraction of sodium carbonate can adjust the enzymatic degradation rate of the silk fibroin 3D scaffolds. With the extension of the degradation time, minerals will be deposited on the surface of the scaffolds. The results show that the silk fibroin 3D scaffolds have biocompatibility, mechanical properties, and degradability, which provides a good material for a barrier biofilm in the future.


Assuntos
Fibroínas/química , Teste de Materiais , Tecidos Suporte/química , Células 3T3 , Animais , Carbonatos , Sobrevivência Celular , Cirurgia da Córnea a Laser , Análise Diferencial Térmica , Camundongos , Microscopia Eletrônica de Varredura , Peptídeo Hidrolases/metabolismo , Espectrofotometria Infravermelho , Difração de Raios X
8.
Artigo em Inglês | LILACS, BBO - Odontologia | ID: biblio-1287496

RESUMO

Abstract Objective: To evaluate the reliability of infrared (IR) thermal camera connected to smartphones, already used in medicine for diagnostic purposes, as an easy tool for access screening to pediatric dentistry services. Material and Methods: After the preventive telephone triage, thirty orthodontic patients (7-13 years) underwent temperature measurement in the office with two no-contact IR devices: forehead digital thermometer and thermal-camera connected to a smartphone (reference areas: forehead, inner canthi, ears). Measurements were compared and differences were statistically investigated with T student's test (p<0.01). Results: Forehead digital thermometer temperatures were superimposable to those recorded in ear areas and inner canthi with the thermal camera connected to a smartphone. Differences were not statistically significant even in comparison between the sexes. Forehead temperature values detected with a thermal camera are lower than those detected with a digital forehead thermometer. Conclusion: Thermal camera on a smartphone could be reliable in measuring body temperature. Mobile thermographic values of ears and inner canthi areas can be used as an alternative to forehead digital thermometer measurements. Further applications in pediatric dentistry of thermography on smartphones should be examined.


Assuntos
Humanos , Masculino , Feminino , Criança , Temperatura Corporal , Termografia/instrumentação , Odontopediatria , Análise Diferencial Térmica/instrumentação , COVID-19 , Interpretação Estatística de Dados , Smartphone , Itália/epidemiologia
9.
Molecules ; 25(24)2020 Dec 17.
Artigo em Inglês | MEDLINE | ID: mdl-33348597

RESUMO

Epoxy resins (EP) have been used as a thermos-setting material in the field of coating, casting, bonding agent, and laminating. However, a major drawback associated with its use is the lack of good flaming properties, and it is responsible for heavy smoke along with hazardous gases considerably limiting its uses in various fields. In this study, N-ethanolamine triazine-piperizine, a melamine polymer (ETPMP), was established as a new charring-foaming agent and was successfully synthesized with ethanolamine, piperizine, cyanuric chloride, and melamine as precursor molecules via the nucleophilic substitution reaction method. Elemental analysis and Fourier transform infrared (FTIR) spectroscopy analysis were applied to approve the synthesis of ETPMP and confirmation of its structure and characterization. The epoxy coating of intumescent flame retardant (IFR) was equipped by introducing ETPMP, ammonium polyphosphate (APP), and copper oxide (CuO) in multiple composition ratios. CuO was loaded at various amounts into the IFR-coating system as a synergistic agent. The synergistic action of CuO on IFR coatings was scientifically examined by using different analytical tests such as vertical burning test (UL-94V), limited oxygen index (LOI), thermal gravimetric analysis (TGA), cone calorimeter, and scanning electron microscope (SEM). The results showed that small changes in the amount of CuO expressively amplified the LOI results and enhanced the V-0 ratings in the UL-94V test. The TGA data clearly demonstrate that the inclusion of CuO can transform the thermal deprivation behavior of coatings with a growing char slag proportion with elevated temperatures. Information from cone calorimeter data affirmed that CuO can decrease the burning factors by total heat release (THR) together with peak heat release rate (PHRR). The SEM images indicated that CuO can enrich the power and compression of the intumescent char that restricts the movement of heat and oxygen. Our results demonstrate a positive influence of CuO on the epoxy-headed intumescent flame retardant coatings.


Assuntos
Cobre/química , Resinas Epóxi/química , Retardadores de Chama/síntese química , Piperazinas/síntese química , Polímeros/química , Compostos Benzidrílicos/química , Calorimetria , Análise Diferencial Térmica , Fenóis/química , Piperazinas/química , Espectroscopia de Infravermelho com Transformada de Fourier , Triazinas/química
10.
Drug Des Devel Ther ; 14: 4303-4313, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33116417

RESUMO

PURPOSE: To enhance the solubility and dissolution profile of simvastatin (SIM) through co-crystallization with varying ratios of nicotinamide (NIC) using various co-methods. MATERIALS AND METHODS: Twelve SIM:NIC co-crystal formulations (F01-F12) were prepared using dry grinding, slurry, liquid-assisted grinding, and solvent-evaporation methods, and their properties compared. Optimized formulations were selected on the basis of dissolution profiles and solubility for in vivo studies. The angle of repose, Carr Index and Hausner ratio were calculated to evaluate flow properties. Differential light scattering (DLS) was used to estimate particle-size distribution. Scanning electron microscopy (SEM) was employed to evaluate surface morphology. Thermal analyses and Fourier-transform infrared (FTIR) spectroscopy were used to determine the ranges of thermal stability and physical interaction of formulated co-crystals. X-ray powder diffraction (XPD) spectroscopy was used to determine the crystalline nature. Solubility and dissolution studies were undertaken to determine in vitro drug-release behaviors. RESULTS: Micromeritic analyses revealed the good flow properties of formulated co-crystals. DLS showed the particle size of co-crystals to be in the nanometer range. SEM revealed that the co-crystals were regular cubes. Thermal studies showed the stability of co-crystals at >300°C. FTIR spectroscopy revealed minor shifts of various peaks. XPD spectroscopy demonstrated co-crystal formation. The formulations exhibited an improved dissolution profile with marked improvements in solubility. In vivo studies showed a 2.4-fold increase in Cmax whereas total AUC(0-∞) was increased 4.75-fold as compared with that of SIM tablets. CONCLUSION: Co-crystallization with NIC improved the solubility and dissolution profile and, hence, the bioavailability of the poorly water-soluble drug SIM.


Assuntos
Inibidores de Hidroximetilglutaril-CoA Redutases/química , Inibidores de Hidroximetilglutaril-CoA Redutases/farmacologia , Niacinamida/química , Niacinamida/farmacologia , Sinvastatina/química , Sinvastatina/farmacologia , Complexo Vitamínico B/química , Complexo Vitamínico B/farmacologia , Animais , Cristalização , Cristalografia por Raios X , Análise Diferencial Térmica , Composição de Medicamentos , Liberação Controlada de Fármacos , Estabilidade de Medicamentos , Inibidores de Hidroximetilglutaril-CoA Redutases/farmacocinética , Luz , Niacinamida/farmacocinética , Tamanho da Partícula , Coelhos , Espalhamento de Radiação , Sinvastatina/farmacocinética , Solubilidade , Espectroscopia de Infravermelho com Transformada de Fourier , Complexo Vitamínico B/farmacocinética
11.
Molecules ; 25(17)2020 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-32883012

RESUMO

A series of nineteen amino acid analogues of amantadine (Amt) and rimantadine (Rim) were synthesized and their antiviral activity was evaluated against influenza virus A (H3N2). Among these analogues, the conjugation of rimantadine with glycine illustrated high antiviral activity combined with low cytotoxicity. Moreover, this compound presented a profoundly high stability after in vitro incubation in human plasma for 24 h. Its thermal stability was established using differential and gravimetric thermal analysis. The crystal structure of glycyl-rimantadine revealed that it crystallizes in the orthorhombic Pbca space group. The structure-activity relationship for this class of compounds was established, with CoMFA (Comparative Molecular Field Analysis) 3D-Quantitative Structure Activity Relationships (3D-QSAR) studies predicting the activities of synthetic molecules. In addition, molecular docking studies were conducted, revealing the structural requirements for the activity of the synthetic molecules.


Assuntos
Adamantano/análogos & derivados , Adamantano/farmacologia , Antivirais/farmacologia , Simulação por Computador , Orthomyxoviridae/efeitos dos fármacos , Relação Quantitativa Estrutura-Atividade , Adamantano/síntese química , Adamantano/química , Animais , Antivirais/síntese química , Antivirais/química , Sítios de Ligação , Morte Celular/efeitos dos fármacos , Cristalografia por Raios X , Análise Diferencial Térmica , Cães , Estabilidade de Medicamentos , Humanos , Ligação de Hidrogênio , Análise dos Mínimos Quadrados , Células Madin Darby de Rim Canino , Conformação Molecular , Simulação de Acoplamento Molecular , Domínios Proteicos , Rimantadina/sangue , Rimantadina/química , Temperatura , Proteínas da Matriz Viral/química
12.
Methods Mol Biol ; 2156: 23-31, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32607972

RESUMO

Frost tolerance is an important factor influencing plant growth, plant species distribution and competitive balance among plant species in the face of climate change. Traditional methods for estimating frost tolerance are often time consuming and require a large sample size, limiting the temporal and spatial resolutions. Differential thermal analysis (DTA) can be advantageous compared to other methods used to determine frost tolerance, most importantly by (1) increasing the number of tested species, tissue types and sampling dates, (2) allowing to test frost tolerance in situ, and (3) more realistically testing the influence of freezing rate and duration. Here, we discuss a typical procedure for DTA, compare its use to other frost tolerance methods and point out its limitations.


Assuntos
Adaptação Biológica , Análise Diferencial Térmica , Congelamento , Fenômenos Fisiológicos Vegetais , Estações do Ano , Análise Diferencial Térmica/métodos , Especificidade de Órgãos , Fenótipo
13.
Methods Mol Biol ; 2156: 33-41, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32607973

RESUMO

Infrared thermal analysis is an invaluable technique to study the plant freezing process. In the differential mode, infrared thermal analysis (IDTA) allows to localize ice nucleation and ice propagation in whole plants or plant samples at the tissue level. Ice barriers can be visualized and supercooling of cells, tissues, and organs can be monitored. Places where ice masses are accommodated in the apoplast can be identified. Here, we describe an experimental setting developed in our laboratory, give detailed information on the practical procedure and preconditions, and give additionally an idea of the problems that would be encountered and how they may be overcome.


Assuntos
Análise Diferencial Térmica , Congelamento , Fenômenos Fisiológicos Vegetais , Espectrofotometria Infravermelho , Análise de Dados , Análise Diferencial Térmica/métodos , Folhas de Planta/fisiologia , Espectrofotometria Infravermelho/métodos
14.
Int J Biol Macromol ; 163: 79-86, 2020 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-32603728

RESUMO

A simple and efficient separation method of carrier-free 47Sc from neutron irradiated titanium target using a novel chitosan-acrylic acid/multiwalled carbon nanotubes (CS-AA/MWCNTs) composite was established. The synthesis of the CS-AA/MWCNTs composite was achieved using gamma radiation-induced template polymerization. The grafting efficiency (GE%) of AA on CS onto the surface of f-MWCNTs reached a maximum of~84% under the optimized conditions (30 wt% CS, 1.0 wt% AA, 0.15 wt% f-MWCNTs, >0.2 wt% N,N'-Methylenebisacrylamide (NMBA), and irradiation dose ~25 kGy). Different analyses (FT-IR, SEM, TGA and DTA) were examined for confirming the structural morphology and mechanical properties of the new synthesized composite. Interestingly, the CS-AA/MWCNTs composite depicted a selective adsorption of Sc(III) rather than Ti(IV) ions at pH 5 with adsorption efficiency of ~93.93%. The ionic exchange separation of no-carrier-added (NCA)47Sc(III) from irradiated TiO2 target on CS-AA/MWCNTs composite packed column efficiently eluted 47Sc(III) by 91 ± 0.8% using 1 M HCl solution. The quality control tests (radionuclidic, radiochemical, and chemical purities) for the eluted 47Sc(III) clarified its high purity and validity for cancer theranostics.


Assuntos
Acrilatos/química , Quitosana/química , Resinas Compostas/síntese química , Nanotubos de Carbono/química , Nêutrons , Radioisótopos/isolamento & purificação , Escândio/isolamento & purificação , Titânio/química , Adsorção , Cromatografia Líquida , Resinas Compostas/química , Análise Diferencial Térmica , Concentração de Íons de Hidrogênio , Microscopia Eletrônica de Varredura , Nanotubos de Carbono/ultraestrutura , Polimerização , Medicina de Precisão , Radioisótopos/análise , Radioisótopos/química , Escândio/análise , Escândio/química , Espectroscopia de Infravermelho com Transformada de Fourier , Propriedades de Superfície , Termogravimetria , Titânio/efeitos da radiação
15.
AAPS PharmSciTech ; 21(5): 152, 2020 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-32440782

RESUMO

The present study investigates concomitant processes of solid-state disordering and oxidation of simvastatin during milling. The separate dry ball milling of crystalline and amorphous powders of simvastatin were conducted at ambient temperature for 10 and 60 min each. The relative crystallinity was determined using X-ray scattering and oxidative degradation was analyzed using liquid chromatography. The physical and chemical transformations in the milled powder were evaluated using modulated differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy. The disordering during milling of the crystalline powder was found to progressively decrease the crystallinity. For the amorphous starting material, milling for 10 min induced a large extent of recrystallization, while milling for 60 min largely re-amorphized the powder. This solid-state disordering and/or ordering were accompanied by progressive air oxidation during milling. The infrared spectroscopic analysis revealed the molecular manifestations associated with the physicochemical transformations in the disordered solid states. The melting point of simvastatin depressed systematically with the increase in the degree of disorder as well as the degradation. The in situ cooling in DSC of milled samples from their molten state led to the formation of the co-amorphous phase between the drug and degradation products, which showed a consistent increase in glass transition temperature with the increase in the content of degradation products. The study overall demonstrates the solid-state re-ordering and disordering of crystalline and amorphous simvastatin accompanied by chemical degradation as the consequence of the mechano-activation.


Assuntos
Inibidores de Hidroximetilglutaril-CoA Redutases/química , Sinvastatina/química , Varredura Diferencial de Calorimetria , Análise Diferencial Térmica , Composição de Medicamentos , Inibidores de Hidroximetilglutaril-CoA Redutases/administração & dosagem , Luz , Transição de Fase , Pós , Espalhamento de Radiação , Sinvastatina/administração & dosagem , Espectrofotometria Infravermelho , Raios X
16.
Int J Biol Macromol ; 156: 80-93, 2020 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-32294497

RESUMO

Biopolymer blend interactions influence the physical, mechanical and barrier properties of edible packaging. Starch (rice and hydroxypropyl cassava starch mixture), agar and maltodextrin were formulated to control the solubility of edible films. Blend materials were characterized for fluid rheology, solid microstructure, mechanical barrier and physical properties. Agar enhanced solid behavior and governed low temperature gelation of the blends, giving improved film forming ability and hydrophobicity. Flexibility of the films highly depended on integrity of polymer networks. Agar formed continuous networks entangled in starch matrices. Conversely, maltodextrin acted as a filler that reduced mechanical strength at high concentration (>40%) due to interruption of network integrity. Interaction between starch and agar led to poor water solubility that was insignificantly impacted by agar concentration (10% to 30%) due to identical molecular bonding. Maltodextrin produced highly miscible and plasticized starch-agar films and led to reduced mechanical relaxation temperature and shriveling of film structures after mold dipping. Solubility increased linearly with higher maltodextrin concentration. Molecular interaction between maltodextrin and starch/agar matrices insignificantly influenced solubility, while strong interaction between starch and agar highly controlled solubility. Findings clarified the interaction mechanisms and behavior of biological macromolecule materials in fluids and solid matrices for manufacture of edible packaging.


Assuntos
Ágar/química , Filmes Comestíveis , Polissacarídeos/química , Solubilidade , Amido/química , Suspensões/análise , Suspensões/química , Ácidos/química , Biopolímeros/química , Análise Diferencial Térmica , Interações Hidrofóbicas e Hidrofílicas , Manihot/química , Fenômenos Mecânicos , Microscopia Eletrônica de Varredura , Oryza/química , Plastificantes/química , Reologia , Espectroscopia de Infravermelho com Transformada de Fourier , Água/química
17.
J Microencapsul ; 37(4): 314-323, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32149534

RESUMO

Aims: Microcapsules comprising of a poly(methyl methacrylate) (PMMA) shell and friction modifier (FM) core were prepared to reduce the friction and extend the service life of engine lubricating oil.Methods: Microcapsules containing both organic FM and molybdenum FM were produced via solvent evaporation technique. The friction coefficient, thermal stability, and chemical composition of microcapsules were investigated.Results: The incorporation of microcapsules in lubricating oil dramatically reduced the friction coefficient to be lower than that of virgin FM. Organic FM and molybdenum FM are compatible during the encapsulation process. The release of the FM inside the microcapsules was controllable by thermal degradation of polymeric shell at 150 °C or mechanical rupture at room temperature.Conclusions: This study provided a novel approach to improve the tribological properties of lubricating oil with long service life, facile fabrication and low cost and will find potential applications in lubrication industry for internal combustion engines.


Assuntos
Cápsulas/química , Polimetil Metacrilato/química , Análise Diferencial Térmica , Excipientes , Fricção , Lubrificantes , Lubrificação , Molibdênio/química , Óleos , Tamanho da Partícula , Solventes , Espectroscopia de Infravermelho com Transformada de Fourier
18.
J Pharm Biomed Anal ; 181: 113065, 2020 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-32032919

RESUMO

Thermal shift assay is a fluorescence dye based biochemical method to determine the melting point of a protein. It can be used to investigate the ligand-induced stabilization of proteins and helps to increase the likelihood of crystallization in biological samples. Dimeric proteins like soluble guanylyl cyclase (sGC) have specific structural and functional properties which may pose a challenge in thermal shift measurements. In this paper, thermal shift assay was used to examine ligand-induced thermostabilization of the dimeric heme-containing protein soluble guanylyl cyclase. Adjustment of the parameters buffer solution, pH, protein / dye ratio and protein amount per well yielded a one-phase melting curve of sGC with a sharp transition and high reproducibility. We found that thermal shift measurement is not affected by heme state or heme content of the enzyme preparation. We used the method to investigate the thermostabilization of sGC induced by the heme-mimetic activator drugs cinaciguat, BAY 60-2770 and BR 11257 in combination with non-hydrolyzable nucleotides. Measurements with the dicarboxylic drugs cinaciguat and BAY 60-2770 yielded steep melting curves with high amplitudes. In contrast, in the presence of the monocarboxylic sGC activator BR 11257, melting curves appear flattened in the dye-based measurements. In the present paper, we show that activity-based thermostability measurements are superior to dye-based measurements in detecting the thermostabilizing influence of sGC activator drugs.


Assuntos
Análise Diferencial Térmica/métodos , Estabilidade Enzimática/efeitos dos fármacos , Guanilil Ciclase Solúvel/química , Benzoatos/farmacologia , Compostos de Bifenilo/farmacologia , Hidrocarbonetos Fluorados/farmacologia , Ligantes , Nucleotídeos/farmacologia , Temperatura de Transição
19.
Int J Biol Macromol ; 147: 53-66, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31887386

RESUMO

There are numerous better applications of fibre reinforced polymer composites today, when compared with metals and alloys. Many studies have been conducted to further improve the inherent mechanical and thermal properties of the composite materials, especially with sustainable, environmental friendly, recyclable and biodegradable reinforcements. Consequently, in this current study, the composites were prepared by combining bio solid waste (date seed filler) and vinyl ester to enhance the properties of polymer composites. The date seed filler reinforced vinyl ester (DSF-VE) composites were prepared by using conventional compression moulding technique with varying fillers loadings from 5% to 50%. The mechanical (tensile, flexural, impact and hardness), water absorption and thermal (heat deflection temperature and thermo-gravimetric analysis) properties of the DSF-VE composites were experimentally evaluated. Scanning electron microscopic analysis was carried out to analyse the surface characteristics and fractured surface of the DSF-VE composites. It was evident from the results obtained that 30 wt% of the DSF-VE composites exhibited the highest mechanical properties: impact, tensile, hardness and flexural of 17.03 KJ/m2, 40.3 MPa, 51 and 149 MPa, respectively, among the fabricated composites. Similarly, the heat deflection temperatures of DSF-VE composites increased by 58.49%, when compared with the neat, pure vinyl ester resin. The thermo-gravimetric analysis showed that the natural filler-based (DSF-VE) composites possessed thermal stability up to 400.2 °C, which was within the polymerisation process temperature. Furthermore, the DSF-VE composites have been successfully utilized for various potential applications, such as fabrication of a table fan blade, an engine guard for two-wheelers and self-motor guard for four wheelers.


Assuntos
Celulose/química , Ésteres/química , Fenômenos Mecânicos , Phoeniceae/química , Sementes/química , Temperatura , Cloreto de Vinil/química , Absorção Fisico-Química , Análise Diferencial Térmica , Teste de Materiais , Resistência à Tração , Termogravimetria , Água/química
20.
Int J Mol Sci ; 20(20)2019 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-31640225

RESUMO

The main phospholipid (MPL) of Thermoplasma acidophilum DSM 1728 was isolated, purified and physico-chemically characterized by differential scanning calorimetry (DSC)/differential thermal analysis (DTA) for its thermotropic behavior, alone and in mixtures with other lipids, cholesterol, hydrophobic peptides and pore-forming ionophores. Model membranes from MPL were investigated; black lipid membrane, Langmuir-Blodgett monolayer, and liposomes. Laboratory results were compared to computer simulation. MPL forms stable and resistant liposomes with highly proton-impermeable membrane and mixes at certain degree with common bilayer-forming lipids. Monomeric bacteriorhodopsin and ATP synthase from Micrococcus luteus were co-reconstituted and light-driven ATP synthesis measured. This review reports about almost four decades of research on Thermoplasma membrane and its MPL as well as transfer of this research to Thermoplasma species recently isolated from Indonesian volcanoes.


Assuntos
Fosfolipídeos/metabolismo , Thermoplasma/metabolismo , Proteínas Arqueais/química , Proteínas Arqueais/metabolismo , Varredura Diferencial de Calorimetria , Simulação por Computador , Análise Diferencial Térmica , Glicosilação , Lipossomos/metabolismo , Fosfolipídeos/química
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...