RESUMO
Cadmium selenide/zinc sulfide (CdSe/ZnS) core-shell quantum dots (QDs) embedded in biocompatible materials were thermally and optically characterized with a thermal lens (TL) technique. Transient TL measurements were performed with a mode-mismatched, dual-beam (excitation and probe) configuration. A thermo-optical study of the CdSe/ZnS QDs was performed for different core diameters (3.5, 4.0, 5.2, and 6.6 nm) in aqueous solution and synthetic saliva, and three different core diameters (2.4, 2.9, and 4.1 nm) embedded in restorative dental resin (0.025% by mass). The thermal diffusivity results are characteristic of the biocompatible matrices. The radiative quantum efficiencies for aqueous solution and biofluid materials are dependent on the core size of the CdSe/ZnS core-shell QDs. The results obtained from the fluorescence spectral measurements for the biocompatible materials support the TL results.
Assuntos
Materiais Biocompatíveis/química , Compostos de Cádmio/química , Pontos Quânticos , Compostos de Selênio/química , Sulfetos/química , Compostos de Zinco/química , Teste de Materiais , Tamanho da Partícula , Resinas Sintéticas , Saliva Artificial , Espectrometria de FluorescênciaRESUMO
Nowadays, the synthetic dyes (as erythrosine, ponceau and tartrazina) and natural colourants (as annatto, paprika, curcuma and anthocyanin) are indispensable in the food, pharmaceutical and cosmetics applications. However, the use of natural colourant has been considered safer for human consumption then synthetic dye. For practical applications of the coloring, optical properties are important for the understanding of the characteristics of them. In this work, we presented the absorption and fluorescence spectroscopic characterizations of annatto extracts obtained from the seeds of the tropical shrub Bixa orellana L. solutions and commercial colourant. The measurements were performed in annatto extracts with acetone and chloroform in different concentrations range (3.5-52.5) µg/mL. The main carotenoids detected in annatto seeds is bixin. The numerical calculus of the absorbance spectra for cis- and trans-bixin conformation is presented. In addition, for commercial colourant, the measurements were performed for six different brands and five lots each one. Modifications in the shape of the colorific fluorescence spectra were observed and it can be an indicative of differences in the industrial methods applied for obtaining annatto pigments powders and/or the possibility of the presence of other impurities added in the commercial powders.
Assuntos
Bixaceae/química , Carotenoides/química , Cor , Óptica e Fotônica , Extratos Vegetais/química , Espectrometria de Fluorescência , Espectrofotometria UltravioletaRESUMO
This study investigated the effect of photodynamic antimicrobial chemotherapy (PACT) using extracts from Alternanthera maritima on the viability of Candida dubliniensis. Human infections constitute a great health problem. Several antifungal drugs are currently available, but their uses are limited by a number of factors, such as low potency, poor solubility, microbial resistance, and drug toxicity. Therefore, the search for new and more effective antimicrobial agents and the development of alternative therapies, such as PACT, are necessary. Crude hexane and ethanol extracts of A. maritima were produced. The prepared extracts presented absorption at 650-700 nm. For bioassays, 50 microL of culture medium, 50 microL of extract (25 mg/mL) or control, and 5 microL of a suspension of the microorganism to be tested (C. dubliniensis ATCC 778157 or ATCC 777, 10(7)CFU/mL) were placed in a sterile 96-well microtiter plate (well cross section=0.38 cm(2)). The contents of each well were irradiated with a 685-nm diode laser with an output power of 35 mW, which was distributed through the well cross section yielding an energy dosage of 28 J/cm(2). In each assay (n=6), one plate was subjected to irradiation, and one was not. For each active sample, the number of colony-forming units per milliliter (CFU/mL) was obtained, and data were analyzed by the Tukey test. The chemical compositions of the extracts were determined by chromatographic and spectroscopic techniques. The results suggest inhibition of the growth of C. dubliniensis when irradiated with a diode laser in the presence of hexane and ethanol extracts from A. maritima as photosensitizers. Laser irradiation alone or crude extracts at 25mg/mL did not significantly reduce the number of CFU/mL. Steroids, triterpenes, and flavonoids were identified in the analyzed extracts. In conclusion, the photoactivation of crude hexane and ethanol extracts of A. maritima by red laser radiation at 685 nm promoted an antimicrobial effect, showing that these natural products can be used as photosensitizers in PACT.
Assuntos
Amaranthaceae/química , Fármacos Fotossensibilizantes/farmacologia , Extratos Vegetais/farmacologia , Candida/efeitos dos fármacos , Candida/efeitos da radiação , Cromatografia Gasosa , Flavonoides/química , Lasers , Testes de Sensibilidade Microbiana , Fotoquimioterapia , Fármacos Fotossensibilizantes/química , Extratos Vegetais/química , Esteroides/química , Triterpenos/químicaRESUMO
OBJECTIVES: We characterized the optical properties, such as absorbance and fluorescence, of dental resins containing quantum dots (QD). We also determined the doping level needed to obtain a broad and nearly flat emission spectrum that provides the perception of white color. METHODS: The samples studied were resin composites from Charisma (Heraeus Kulzer) prepared with CdSe/ZnS core-shell QD (0.05-0.77 mass%). RESULTS: The results showed that the fluorescence of dental resin composites can be tailored by using CdSe/ZnS core-shell quantum dots. CONCLUSION: QD core incorporation into dental resins allows the fabrication of restorative materials with fluorescence properties that closely match those of natural human teeth.