RESUMO
Currently, advanced dosimeters like polymer gels are capable of obtaining reliable and accurate 3D dose distributions from correlations with the different polymerization degrees induced by incident radiation. Samples of polymer gel dosimeters are commonly read out using magnetic resonance imaging or optical methods like visible light transmission or laser computed tomography. Alternatively, this work proposes and evaluates the implementation of Raman spectroscopy to provide direct information on the effect of oxygen permeating through the walls of phantoms on the polymerization initiated by irradiation in three types of polymer gel dosimeters, namely NIPAM, ITABIS and PAGAT. The aim of the present study is to provide better and complete interpretations using three different containers, adequate for integral, 2D and 3D dose mapping. Moreover, Raman spectroscopy has been used to analyze the well-known effect of oxygen inhibition on the different polymer gel dosimeters remarking the importance of avoiding air exposition during sample storage and readout. Dose-response curves for different polymer gels were obtained in terms of measurements with a calibrated ionization chamber. Additionally, dedicated Monte Carlo simulations were performed aimed at characterizing dose for different X-ray irradiation setups, providing also suitable information to evaluate oxygen diffusion through the sample wall. The obtained results were contrasted with optical transmission readout as well as Monte Carlo simulations attaining very good agreements for all dosimeter types.
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Graphitic carbon nitride (g-C3N4) was synthesized from a low-cost precursor by means of a thermal process. The product was characterized by several spectroscopic techniques and the crystallinity was analyzed by X-ray diffraction. In the manufacture of the sensor, g-C3N4 was chemically exfoliated and a film was placed on the surface of a Highly Oriented Pyrolytic Graphite (HOPG). We compared the electrocatalytic activities of g-C3N4/HOPG and pristine HOPG surfaces as sensors for H2O2 quantification in buffer solution at pH 7. The results indicate that the surface of g-C3N4/HOPG exhibits striking analytical stability as well as reproducibility, enabling a reliable and sensitive determination within the 0.12-120 µM interval with a detection limit of 0.12 µM. These results suggest that this g-C3N4 film is a really particularly good nano-structured material to be applied as a biosensor. Chemical and physical factors are responsible for the outstanding electrocatalytic activity observed. The N in the g-C3N4 allows huge uptake of H2O2 through the hydrogen-bonding interaction and the change in the electronic structure since the HOPG/g-C3N4 heterojunction favors the charge transfer process through the interface.
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Nanoparticle-cored dendrimers (NCDs) are now offering themselves as versatile carriers because of their colloidal stability, tunable membrane properties and ability to encapsulate or integrate a broad range of drugs and molecules. This kind of hybrid nanocomposite aims to combine the advantages of stimuli-responsive dendritic coatings, in order to regulate the drug release behaviour under different conditions and improve the biocompatibility and in vivo half-time circulation of the inorganic nanoparticles. Size, surface chemistry and shape are key nanocarrier properties to evaluate. Here, we have reviewed the most recent advances of NCDs in drug delivery systems, compared their behaviour with non-dendritic stabilized nanoparticles and highlighted their challenges and promising applications in the future.
Assuntos
Dendrímeros/química , Portadores de Fármacos/química , Nanopartículas/química , Meios de Contraste/química , Humanos , Imageamento por Ressonância Magnética , Microscopia Confocal , PorosidadeRESUMO
The influence of the polymeric morphology of different types of Fe(3+)-containing sorbents and their properties in retention of phosphoamino acids is presented in this paper. Poly(hydroxylated polybutadienic-hydroxyethyl methacrylate) [poly(PB-HEMA)] and poly(ethylene glycol dimethacrylate-hydroxyethyl methacrylate) [poly(EGDMA-HEMA)] base supports were submitted to chemical modifications to attain metal ion-containing sorbents. Properties such as specific surface area, pore volume, equilibrium volume swelling ratios, extent of conversion rate of functional groups, amount of chelated metal ion, ligand occupation, as well as quantity of phosphoamino acid retained, were used as comparative parameters for those different base matrices. Results suggest that Fe(3+) immobilized on poly(EGDMA-HEMA) base support are more efficient as a group-specific sorbent to retain phosphoamino acids than those obtained using poly(PB-HEMA) base support.