RESUMO
The aims of this work were to evaluate the antibacterial and antiproliferative potential in vitro of the metal complex with 4-aminobenzoic acid (Ag-pABA) and a drug delivery system based on bacterial cellulose (BC-Ag-pABA). The Ag-pABA complex was characterized by elemental analysis, high resolution mass spectrometry and single-crystal X-ray diffraction techniques, which indicated a 1:2 metal/pABA composition plus a nitrate ion coordinated to silver by the oxygen atom, with the coordination formula [Ag (C7H7NO2)2(NO3)]. The coordination of pABA to the silver ion occurred by the nitrogen atom. The in vitro antibacterial activity of the complex evaluated by minimum inhibitory concentration assays demonstrated the effective growth inhibitory activity against Gram-positive, Gram-negative biofilm producers and acid-alcohol resistant Bacillus. The antiproliferative activities against a panel of eight tumor cells demonstrated the activity of the complex with a significant selectivity index (SI). The DNA interaction capacity and the Ames Test indicated the absence of mutagenicity. The BC-Ag-pABA composite showed an effective capacity of sustained release of Ag-pABA. The observed results validate further studies on its mechanisms of action and the conditions that mediate the in vivo biological effects using animal models to confirm its safety and effectiveness for treatment of skin and soft tissues infected by bacterial pathogens, urinary tract infections and cancer.
Assuntos
Ácido 4-Aminobenzoico/química , Antibacterianos/farmacologia , Bactérias/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Celulose/química , Prata/farmacologia , Antibacterianos/química , Preparações de Ação Retardada , Testes de Sensibilidade Microbiana , Prata/químicaRESUMO
Osmium pyridine-bipyridine redox centers have been tethered to Au electrodes by chemical modification through Au-S and Au-C bonds respectively. 4-Mercapto benzoic acid and the reduction product of the aryl diazonium salt of 4-amino benzoic acid were reacted on Au surfaces, with further post-functionalization by chemical reaction of the osmium complex amino-pyridine derivative with the surface carboxylates. The resulting modified Au surfaces were characterized by polarization modulated infrared reflection absorption spectroscopy (PM-IRRAS), scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), resonant raman spectroscopy and cyclic voltammetry.
Assuntos
Ouro/química , Osmio/química , Piridinas/química , Ácido 4-Aminobenzoico/química , Eletroquímica , Eletrodos , Microscopia de Tunelamento , Estrutura Molecular , Oxirredução , Espectroscopia Fotoeletrônica , Análise Espectral Raman , Propriedades de SuperfícieRESUMO
OBJECTIVES: To evaluate the influence of different tertiary amines on degree of conversion (DC), shrinkage-strain, shrinkage-strain rate, Knoop microhardness, and color and transmittance stabilities of experimental resins containing BisGMA/TEGDMA (3:1wt), 0.25wt% camphorquinone, 1wt% amine (DMAEMA, CEMA, DMPT, DEPT or DABE). Different light-curing protocols were also evaluated. METHODS: DC was evaluated with FTIR-ATR and shrinkage-strain with the bonded-disk method. Shrinkage-strain-rate data were obtained from numerical differentiation of shrinkage-strain data with respect to time. Color stability and transmittance were evaluated after different periods of artificial aging, according to ISO 7491:2000. Results were evaluated with ANOVA, Tukey, and Dunnett's T3 tests (α=0.05). RESULTS: Studied properties were influenced by amines. DC and shrinkage-strain were maximum at the sequence: CQAssuntos
Bis-Fenol A-Glicidil Metacrilato/química
, Resinas Compostas/química
, Polietilenoglicóis/química
, Ácidos Polimetacrílicos/química
, Substâncias Redutoras/química
, Ácido 4-Aminobenzoico/química
, Compostos de Anilina/química
, Cor
, Dureza
, Humanos
, Luz
, Metacrilatos/química
, Fotoiniciadores Dentários/química
, Polimerização
, Espectroscopia de Infravermelho com Transformada de Fourier
, Estresse Mecânico
, Terpenos/química
, Fatores de Tempo
, Toluidinas/química
, para-Aminobenzoatos
RESUMO
Potentially bioactive N-(aminoalkyl)lactamic amino acids and esters were synthesized in satisfactory to good yields by S(N)Ar reactions of aromatic acids with N-(3-aminopropyl)lactams followed by esterification with tertiary amino alcohols. The addition-elimination S(N)Ar mechanism was confirmed by NMR and MS measurements.
Assuntos
Ácido 4-Aminobenzoico/síntese química , Aminoácidos/síntese química , Ésteres/síntese química , Ácido 4-Aminobenzoico/química , Aminoácidos/química , Esterificação , Ésteres/química , Estrutura MolecularRESUMO
Folic acid, or pteroyl-l-glutamic acid (PteGlu), is a precursor of coenzymes involved in the metabolism of nucleotides and amino acids. PteGlu is composed of three moieties: a 6-methylpterin (Mep) residue, a p-aminobenzoic acid (PABA) residue, and a glutamic acid (Glu) residue. Accumulated evidence indicates that photolysis of PteGlu leads to increased risk of several pathologies. Thus, a study of PteGlu photodegradation can have significant ramifications. When an air-equilibrated aqueous solution of PteGlu is exposed to UV-A radiation, the rate of the degradation increases with irradiation time. The mechanism involved in this "auto-photo-catalytic" effect was investigated in aqueous solutions using a variety of tools. Whereas PteGlu is photostable under anaerobic conditions, it is converted into 6-formylpterin (Fop) and p-aminobenzoyl-l-glutamic acid (PABA-Glu) in the presence of oxygen. As the reaction proceeds and enough Fop accumulates in the solution, a photosensitized electron-transfer process starts, where Fop photoinduces the oxidation of PteGlu to Fop, and H(2)O(2) is formed. This process also takes place with other pterins as photosensitizers. The results are discussed with the context of previous mechanisms for processes photosensitized by pterins, and their biological implications are evaluated.
Assuntos
Ácido Fólico/metabolismo , Fotólise , Fármacos Fotossensibilizantes/química , Pterinas/química , Ácido 4-Aminobenzoico/química , Ácido Fólico/química , Ácido Fólico/efeitos da radiação , Glutamatos/química , Glutamatos/metabolismo , Peróxido de Hidrogênio/química , Oxirredução , Fármacos Fotossensibilizantes/metabolismo , Fármacos Fotossensibilizantes/efeitos da radiação , Pterinas/metabolismo , Pterinas/efeitos da radiação , Oxigênio Singlete/química , Fatores de Tempo , Raios UltravioletaRESUMO
AIM: To evaluate the radiopacity, degree of conversion (DC) and flexural strength of an experimental dental cement, with several added radiopaque substances. METHODOLOGY: Titanium dioxide, quartz, zirconia, bismuth oxide, barium sulphate and ytterbium trifluoride were added to the experimental cement in five different concentrations. Radiopacity was evaluated with a phosphor plate system, and the radiodensity of specimens was compared with an aluminium step-wedge. DC was evaluated with FT-infrared spectroscopy following 20 s of photo-activation. Specimens with dimensions of 12 x 2 x 2 mm were used for the flexural strength test. Data were analysed with two-way anova and Tukey's post hoc test. RESULTS: Radiopacity of the experimental dental cements with barium sulphate and bismuth oxide at 40% and ytterbium fluoride at 30% and 40% showed no significant differences in comparison with 3 mm of Al (181, 96). CONCLUSIONS: The experimental dental cements with at least 30% added ytterbium trifluoride had satisfactory radiopacity without influencing other properties.
Assuntos
Meios de Contraste/química , Cimentos Dentários/química , Fluoretos/química , Itérbio/química , Ácido 4-Aminobenzoico/química , Absorciometria de Fóton , Alumínio/química , Sulfato de Bário/química , Materiais Biocompatíveis/química , Bismuto/química , Bis-Fenol A-Glicidil Metacrilato/química , Cânfora/análogos & derivados , Cânfora/química , Humanos , Teste de Materiais , Metacrilatos/química , Transição de Fase , Processos Fotoquímicos , Maleabilidade , Polietilenoglicóis/química , Ácidos Polimetacrílicos/química , Quartzo/química , Espectroscopia de Infravermelho com Transformada de Fourier , Estresse Mecânico , Fatores de Tempo , Titânio/química , Ítrio/química , Zircônio/química , para-AminobenzoatosRESUMO
PURPOSE: To determine the influence of rate of polymerization, degree of conversion and volumetric shrinkage on stress development by varying the amount of photoinitiators in a model composite. METHODS: Volumetric shrinkage (with a mercury dilatometer), degree of conversion, maximum rate of reaction (RPmax) (with differential scanning calorimetry) and polymerization stress (with a controlled compliance device) were evaluated. Bis-GMA/TEGDMA (equal mass ratios) were mixed with a tertiary amine (EDMAB) and camphorquinone, respectively, in three concentrations (wt%): high = 0.8/1.6; intermediate = 0.4/0.8 and low = 0.2/0.4. 80 wt% filler was added. Composites were photoactivated (400 mW/cm2 x 40 seconds; radiant exposure = l6 J/cm2). A fourth experimental group was included in which the low concentration formulation was exposed for 80 seconds (32 J/cm2). RESULTS: For the same radiant exposure, conversion, RPmax and stress increased with photoinitiator concentration (P < 0.001). When the low concentration group exposed to 32 J/cm2 was compared with the high and intermediate groups (exposed to 16 J/cm2), RPmax still increased with the photoinitiator concentration between all levels (P < 0.001) but conversion and stress did not vary (P > 0.05). Shrinkage did not vary regardless of the photoinitiator concentration or radiant exposure. For the photoinitiator concentrations used in this study. Polymerization stress was influenced by conversion but not by rate of reaction.
Assuntos
Resinas Compostas/química , Materiais Dentários/química , Ácido 4-Aminobenzoico/química , Bis-Fenol A-Glicidil Metacrilato/química , Varredura Diferencial de Calorimetria , Fenômenos Químicos , Química Farmacêutica , Complacência (Medida de Distensibilidade) , Lâmpadas de Polimerização Dentária , Humanos , Cinética , Teste de Materiais , Processos Fotoquímicos , Polietilenoglicóis/química , Polímeros/química , Ácidos Polimetacrílicos/química , Doses de Radiação , Estresse Mecânico , Propriedades de Superfície , Terpenos/química , Fatores de Tempo , para-AminobenzoatosRESUMO
OBJECTIVE: The aim of this study was to compare the photobleaching rate of CQ in different dental resins. METHODS: The photodecomposition rate of CQ/amine system in bis-GMA/TEGDMA, bis-EMA and UDMA polymerizing monomers was evaluated at different light intensities. The photobleaching of the CQ was studied by monitoring the decrease in light absorption as a function of continuous irradiation time. The absorption changes were assessed by recording the transmitted light that passed through samples of monomers containing CQ/amine. RESULTS: Complete photobleaching of CQ was observed in all the monomer tested and the rate constant for the photobleaching was proportional to the radiation intensity. Hydrogen abstraction from amines by the excited CQ state via electron transfer and direct hydrogen abstraction from monomer structures were involved in the CQ photoreduction. CQ was photobleached in the absence of coinitiator in a dimethacrylate monomer containing a carbamate functional group (UDMA). This behavior was attributed to the presence of labile hydrogen atoms in the UDMA monomer. The CQ photobleaching rate constant in UDMA containing CQ/amine was similar to that in UDMA in the absence of amine. Moreover, the efficiency of CQ to photoinitiate the polymerization of UDMA in the absence of amine demonstrated that the radicals derived from the UDMA monomer via hydrogen abstraction are highly reactive toward double bonds. SIGNIFICANCE: CQ photoinitiates the polymerization of the UDMA monomer in the absence of amine and the efficiency of this process is comparable to that of traditional bis-GMA and bis-EMA monomers activated with CQ/amine.
Assuntos
Resinas Compostas/química , Materiais Dentários/química , Metacrilatos/química , Terpenos/efeitos da radiação , Ácido 4-Aminobenzoico/química , Ácido 4-Aminobenzoico/efeitos da radiação , Absorção , Algoritmos , Bis-Fenol A-Glicidil Metacrilato/química , Bis-Fenol A-Glicidil Metacrilato/efeitos da radiação , Resinas Compostas/efeitos da radiação , Materiais Dentários/efeitos da radiação , Transferência de Energia , Humanos , Hidrogênio/química , Hidrogênio/efeitos da radiação , Luz , Teste de Materiais , Metacrilatos/efeitos da radiação , Polietilenoglicóis/química , Polietilenoglicóis/efeitos da radiação , Polímeros/química , Polímeros/efeitos da radiação , Ácidos Polimetacrílicos/química , Ácidos Polimetacrílicos/efeitos da radiação , Poliuretanos/química , Poliuretanos/efeitos da radiação , Doses de Radiação , Substâncias Redutoras/química , Substâncias Redutoras/efeitos da radiação , Terpenos/química , Fatores de Tempo , para-AminobenzoatosRESUMO
OBJECTIVES: To evaluate the effect of amine ratio (ethyl 4-dimethylaminobenzoate, EDMAB) on the maximum rate of polymerization (R(p)(max)), degree of conversion (DC), Knoop hardness (KH), water sorption (Wsp), water solubility (Wsl) and color changes (DeltaE) over time of resin composites formulated with the photoinitiators camphorquinone (CQ), phenylpropanedione (PPD) and CQ-PPD in combination. MATERIALS AND METHODS: Experimental resin composites were made with photoinitiator:amine ratios of 2:1, 1:1, 1:1.5 and 1:2 by weight. R(p)(max) was evaluated with differential scanning calorimetry (DSC), DC with DSC and Fourier transformed infrared (FTIR) spectroscopy, KH with Knoop indentation, Wsp and Wsl adapted from ISO 4049; and color with a chromameter. The results were analyzed with two-way ANOVA/Tukey's multiple comparison test (p<0.05). RESULTS: The higher the amine ratio in the composite, the higher was DC, R(p)(max), and KH, and the lower was Wsl, regardless of the photoinitiator type. The use of PPD alone resulted in poorer properties than CQ and CQ-PPD. Many factors seem to affect the color changes and the b-axis data revealed that the higher the amine ratio, the higher was the +b value (yellowing) for CQ and CQ-PPD formulations. CONCLUSIONS: Higher amine ratios led to improved polymer properties, but also produced more yellowing in resin composites with CQ and CQ-PPD. The use of PPD alone was not advantageous for producing good final properties when compared to CQ and CQ-PPD.
Assuntos
Chalconas/química , Resinas Compostas/química , Materiais Dentários/química , Terpenos/química , Ácido 4-Aminobenzoico/química , Absorção , Adsorção , Bis-Fenol A-Glicidil Metacrilato/química , Varredura Diferencial de Calorimetria , Fenômenos Químicos , Cor , Dureza , Humanos , Teste de Materiais , Polietilenoglicóis/química , Polímeros/química , Ácidos Polimetacrílicos/química , Solubilidade , Espectroscopia de Infravermelho com Transformada de Fourier , Propriedades de Superfície , Água/química , para-AminobenzoatosRESUMO
OBJECTIVES: To evaluate the degree of conversion (DC), maximum rate of polymerization (Rpmax), Knoop hardness (KHN) and yellowing (b-value) of resin composites formulated with phenylpropanedione (PPD), camphorquinone (CQ), or CQ/PPD at different concentrations. The hypotheses tested were (i) PPD or CQ/PPD would produce less Rpmax and yellowing than CQ alone without affecting DC and KHN, and (ii) Rpmax, DC, and KHN would be directly related to the absorbed power density (PDabs). METHODS: CQ/amine, PPD/amine and CQ/PPD/amine were used at low, intermediate and high concentrations in experimental composites. Photoinitiator absorption and halogen-light emission were measured using a spectrophotometer, Rp with differential scanning calorimetry (DSC), DC with DSC and FTIR, KHN with Knoop indentation; and color with a chromameter. The results were analyzed with two-way analysis of variance (ANOVA)/Student-Newman-Keul's test (p<0.05). Correlation tests were carried out between PDabs and each of DC, Rpmax and KHN. RESULTS: The PDabs increased with photoinitiator concentration and PPD samples had the lowest values. In general, maximum DC was comparable at intermediate concentration, while Rpmax and KHN required higher concentrations. DC was similar for all photoinitiators, but Rpmax was lower with PPD and CQ/PPD. PPD produced the lowest KHN. Yellowing increased with photoinitiator concentration. PPD did not reduce yellowing at intermediate and/or high concentrations, compared to CQ-formulations. PDabs showed significant correlations with DC, Rpmax and KHN. CONCLUSION: PPD or CQ/PPD reduced Rpmax in experimental composites without affecting the DC. The use of PPD did not reduce yellowing, but reduced KHN. DC, Rpmax and KHN were dependent on PDabs.
Assuntos
Resinas Compostas/química , Materiais Dentários/química , Ácido 4-Aminobenzoico/química , Ácido 4-Aminobenzoico/efeitos da radiação , Absorção , Bis-Fenol A-Glicidil Metacrilato/química , Bis-Fenol A-Glicidil Metacrilato/efeitos da radiação , Varredura Diferencial de Calorimetria , Chalconas/química , Chalconas/efeitos da radiação , Cor , Resinas Compostas/efeitos da radiação , Materiais Dentários/efeitos da radiação , Dureza , Humanos , Teste de Materiais , Polietilenoglicóis/química , Polietilenoglicóis/efeitos da radiação , Polímeros/química , Polímeros/efeitos da radiação , Ácidos Polimetacrílicos/química , Ácidos Polimetacrílicos/efeitos da radiação , Doses de Radiação , Espectrofotometria Ultravioleta , Espectroscopia de Infravermelho com Transformada de Fourier , Terpenos/química , Terpenos/efeitos da radiação , para-AminobenzoatosRESUMO
A new procedure was developed for the in situ characterization of the lability of metal species in aquatic systems by using a system equipped with a diffusion membrane and cellulose organomodified with p-aminobenzoic acid groups (DM-Cell-PAB). To this end, the DM-Cell-PAB system was prepared by adding cellulose organomodified with p-aminobenzoic acid groups (Cell-PAB) to pre-purified cellulose bags. After the DM-Cell-PAB system was sealed, it was examined in the laboratory to evaluate the influence of complexation time, mass of exchanger, pH, metal ions (Cu, Cd, Fe, Mn, and Ni), and concentration of organic matter on the relative lability of metal species. It was found that the pH and kinetics strongly influence the process of metal complexation by the DM-Cell-PAB system. At all pH levels, Cd, Mn, and Ni showed lower complexation with Cell-PAB resin than Cu and Fe metals. Note that relative lability of metals complexed to aquatic humic substances (AHS) in the presence of Cell-PAB resin showed the following order: Cu approximately or = Fe>>Ni>Mn=Cd. The results presented here also indicate that increasing the AHS concentration decreases the lability of metal species by shifting the equilibrium to AHS-metal complexes. Our results indicate that the system under study offers an interesting alternative that can be applied to in situ experiments for differentiation of labile and inert metal species in aquatic systems.
Assuntos
Ácido 4-Aminobenzoico/química , Celulose/química , Metais Pesados/análise , Metais Pesados/química , Concentração de Íons de Hidrogênio , Íons/química , Cinética , Fatores de Tempo , Água/análiseRESUMO
OBJECTIVES: To evaluate the efficiency of the photopolymerization of dental resins it is necessary to know to what extent the light emitted by the light curing units is absorbed by the photoinitiators. On the other hand, the efficiency of the absorbed photons to produce species that launch the polymerization process is also of paramount importance. Therefore, the previously determined PAE (photon absorption efficiency) is used in conjunction with the polymerization quantum yields for the photoinitiators, in order to be able to compare the total process on an equivalent basis. This parameter can be used to identify the best performance for the photochemical process with specific photoinitiators. METHODS: The efficiency of LED (Ultrablue IS) and QTH (Optilux 401) lamps were tested comparing their performances with the photoinitiators camphorquinone (CQ); phenylpropanedione (PPD); monoacylphosphine oxide (Lucirin TPO); and bisacylphosphine oxide (Irgacure 819). The extent of photopolymerization per absorbed photon was determined from the polymerization quantum yields obtained by using the photoinitiators to polymerize methyl methacrylate, and afterwards combined with the previously determined PAEs. RESULTS: Although CQ presents a rather low polymerization quantum yield, its photopolymerization efficiency is practically the highest when irradiated with the Ultrablue LED. On the other hand, Lucirin is much more efficient than the other photoinitiators when irradiated with a QTH lamp, due to its high quantum yield and the overlap between its absorption spectrum and the output of the visible lamp light. SIGNIFICANCE: Difference in photopolymerization efficiencies arise when combinations of photoinitiators are used, and when LED sources are used in preference to QTH. Mechanistic understanding is essential to optimal initiator formulation.