Molecular Information on the Potential of Europium Complexes for Local Recognition of a Nucleoside-Based Drug by Using Nanostructured Interfaces Assembled as Langmuir-Blodgett Films.

The production of nanostructured materials for biological and medical applications may be applied toward the conjugation of adequate substances to boost the stimulus response of sensors and diagnostic probes. In this sense, Langmuir-Blodgett films constituted of bioinspired and biomimetic materials have attracted attention because of the ease of manipulation of the molecular architecture. In this paper, we employed a nucleoside-based drug, which was linked with a sterol hydrophobic moiety (3',4'-acetonide-uridine-succinate-cholesterol conjugate) to provide it an amphiphilic character. The drug was spread on the air-water interface, alone or mixed with stearic acid, forming Langmuir monolayers, and the complex Eu(tta)3(H2O)2 was incorporated in the drug-containing monolayer. Interactions at the air-water interface between stearic acid, the drug, and the europium complex were then investigated with tensiometry, surface potential, infrared spectroscopy, and Brewster angle microscopy. The Langmuir films were transferred to solid supports as Langmuir-Blodgett films, which presented luminescent properties that could be tuned according to the molecular architecture. We believe that these results can serve as a novel approach to characterize and assemble materials organized in the molecular scale for medical applications.

Electrical and mechanical properties of self-supported hydroxypropyl methylcellulose-polyaniline conducting films.

The purpose of this work was to develop a simple method to produce self-supported films composed of hydroxypropyl methylcellulose (HPMC) and polyaniline (PANI) by the direct mixture of aqueous dispersions of both polymers with subsequent drying. The addition of HPMC, a cellulose derivative with an excellent film-forming capacity, was fundamental to overcoming the poor processability of PANI, which impairs its use in many technological applications. All films showed conductivity in the order of 10-2 to 10-3 S cm-1, which is in the range for metals or semiconductors. The typical electroactivity of PANI was also maintained in the hybrid films. The thermal stability and the mechanical properties of the pristine PANI were also improved with the addition of HPMC. Cellulose-containing conducting polymers can be considered a material of the future, with possible applications in several areas, such as smart wallpapers, e-papers, and sensors.

Mechanical, optical, and physicochemical properties of HPMC-based doxazosin mesylate orodispersible films

Abstract In this study, orodispersible films formed from hydroxypropyl methylcellulose (HPMC) E6 (2, 2.5, and 3%) and plasticizers ((glycerin (Gly), propylene glycol (PP), or polyethylene glycol (PEG)), containing doxazosin mesylate, were prepared by the solvent casting method and characterized. Design of experiments (DoE) was used as a statistical tool to facilitate the interpretation of the experimental data and allow the identification of optimal levels of factors for maximum formulation performance. Differential scanning calorimetry (DSC) curves and X-ray powder diffraction (XRPD) diffractograms showed doxazosin mesylate amorphization, probably due to complexation with the polymer (HPMC E6), and the glass transition temperature of the polymer was reduced by adding a plasticizer. Fourier transformed infrared (FTIR) spectroscopy results showed that the chemical structure of doxazosin mesylate was preserved when introduced into the polymer matrix, and the plasticizers, glycerin and PEG, affected the polymer matrix with high intensity. The addition of plasticizers increased the elongation at break and adhesiveness (Gly > PEG > PP), confirming the greater plasticizer effect of Gly observed in DSC and FTIR studies. Greater transparency was observed for the orodispersible films prepared using PP. The addition of citric acid as a pH modifier was fundamental for the release of doxazosin mesylate, and the desirability formulation had a release profile similar to that of the reference product

Interaction of chlorhexidine with biomembrane models on glass ionomer by using the Langmuir-Blodgett technique.

The antimicrobial property of chlorhexidine is believed to be associated with its interaction of bacterium membrane, which calls for research on the identification of membranes sites capable of drug binding. In this study, we investigated the interaction of chlorhexidine digluconate, a known agent with bactericidal and bacteriostatic activities employed in the treatment of periodontal diseases, with bacteria cell model systems by using Langmuir monolayers. The insertion of the drug caused the surface pressure-area isotherms for a mixed protein-lipid monolayer to be shifted to higher lipid molecular areas, which was the first indication of the action of chlorhexidine in the membrane model. Surface infrared spectroscopy pointed to intrinsic interactions of the drug with the hydrophobic part of the lipid, leading to a disruption of the lipid organization at the interface. Also, the secondary structure of the polypeptide model employed in this work has been changed, as a consequence of the drug interactions. Such change in the lipid-protein models could be confirmed when the membrane was transferred to glass ionomer cement as a solid support, which can be considered a model for dental surfaces. Therefore, chlorhexidine interacts with lipid and protein moieties supposed to be present in lipid membranes. This may have important implication in understanding how the drug acts on specific sites of the bacteria membrane.

External polyacrylate-coating as alternative material for preparation of photopolymerized sol-gel monolithic column.

Photopolymerized sol-gel monolithic columns for use in capillary electrochromatography were prepared in 125 microm i.d. polyacrylate-coated fused-silica capillaries. The polyacrylate-coating, unlike the polyimide one, is transparent to the radiation used (approximately 370 nm), and thus, no coating removal is necessary. This is a very important particularity since intrinsic capillary column characteristics, such as flexibility and mechanical resistance, are unchanged. A mixture containing metacryloxypropyltrimethoxysilane (MPTMS) as the polymeric precursor, hydrochloric acid as the catalyst, toluene as the porogen and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (Irgacure 819) as the photoinitiator was irradiated at 370 nm for 20 min inside the capillaries to prepare the columns through sol-gel approach. The versatility and viability of the use of polyacrilate as a new capillary external coating were shown through preparation of two columns under different conditions, which were tested in electrochromatography for separation of standard mixture containing thiourea (marker compound), propylbenzene, phenanthrene and pyrene.

In vitro surface roughness of different glass ionomer cements indicated for ART restorations

Aim: The aim of this in vitro study was to evaluate the surface roughness of three glass ionomer cements (GICs) indicated for ART restorations. Methods: Ten cylindrical specimens of three commercial glass ionomers cements (Vidrion R - S.S. White, Maxxion R - FGM and Vitromolar DFL) were prepared (n=30) without surface finishing or protection. Twenty-four hours after preparation, the surface roughness measurements were obtained as the mean of three readings of the surface of each specimen by profilometry. The roughness values (Ra, ìm) were subjected to one-way ANOVA and Tukey’s test (p<0.05). Results: No statistically significant difference swere observed between Vidrion R (0.18 ± 0.05) and Vitromolar (0.21 ± 0.05), whereas Maxxion R presented significantly higher roughness values than those of the other materials. Conclusions: It may be concluded that characteristics of particle size and composition of the different GICs affected their surface roughness 24 h after preparation.

Estudo das alterações em esmalte de dentes decíduos após exposição a bebidas disponíveis no mercado / Study of the changes in the temporary teeth enamel after exposure to drinks available on the market

O objetivo deste estudo foi avaliar a morfologia e rugosidade superficial do esmalte de dentes decíduos antes e após exposição a cinco diferentes soluções, incluindo bebidas industrializadas, disponíveis no mercado nacional e rotineiramente consumidas por crianças (saliva artificial, Coca-Cola, suco Kapo (sabor morango), suco Del Valle Monsters (sabor pêssego) e Yakult). Aferiu-se o pH das mesmas e 50 caninos decíduos humanos foram distribuídos aleatoriamente em cinco grupos, a face vestibular de cada dente foi delimitada no seu longo eixo, uma parte foi imersa em 50 mL de solução (15 minutos) e lavada com água deionizada (15 segundos). Ambas as faces foram analisadas por meio de perfilômetro (FormTracer ? modelo SV? CS25). A análise estatística não mostrou diferença entre as faces (controle e tratada) e entre as bebidas avaliadas. A análise morfológica pela Microscopia Eletrônica de Varredura mostrou diferentes padrões de perda da estrutura dental, sugerindo maior alteração morfológica quanto maior acidez da bebida. Concluiu-seque as soluções demonstraram potencial erosivo, porém não houve diferenças estatísticas entre as faces dos dentes (controle e tratada) e entre os efeitos causados pelas bebidas na superfície dental.

The purpose of this study was to evaluate the morphology and surface texture of temporary teeth enamel before and after exposure to fi ve different solutions, including industrialized drinks, available in the national market and routinely consumed by children (artifi cial saliva, Coca-Cola,Kapo juice (strawberry fl avor), Del Valle Monsters juice (peach fl avor) and Yakult). The pH of these drinks was measured and fi fty human deciduous canines were randomly distributed intofi ve groups. The vestibular face of each tooth was delimited in its long axis, and part of it was immersed in 50 mL of solution for 15 minutes and rinsed with deionized water for 15 seconds.Both faces were analyzed through perfi lometer (FormTracer – model SV-CS25). The statistical analysis showed no differences between the faces (control and treated) and beverages evaluated. The morphological analysis by Scanning Electron Microscopy showed different dental structure loss patterns, suggesting greater morphological change in more acid beverages. So, it was concludedthat the solutions demonstrated erosive potential, but there were no statistical differences between the faces (control and treated) of human deciduous canines and the effects caused by drinks on the dental enamel surface.