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Cremes hidratantes faciais anti-idade: uma revisão dos mecanismos de ação dos diferentes ativos disponíveis no mercado

Thu, 30 Jul 2026 00:00:00 GMT

Title: Cremes hidratantes faciais anti-idade: uma revisão dos mecanismos de ação dos diferentes ativos disponíveis no mercado Abstract: Skin aging is a complex and inevitable biological process driven by intrinsic factors, such as genetics and metabolism, and extrinsic factors, with exposure to ultraviolet radiation (UV), pollution, and lifestyle standing out as the primary accelerators of extracellular matrix degradation. This study conducted a literature review on the process of cutaneous senescence and analyzed the efficacy of active ingredient classes, mechanisms of action, and formulations used to prevent and treat its signs. Skin physiology reveals that the depletion of structural components, such as collagen, elastin, and glycosaminoglycans, combined with the collapse of the calcium ion gradient, underlies the development of wrinkles and skin laxity. Analysis of the active ingredients demonstrated that the efficacy of these cosmeceuticals depends on crucial variables, such as active ingredient concentration, vehicle formulation, and chemical stability in the presence of oxidizing species. Anti-aging actives, including humectants, retinoids, alpha-hydroxy acids, peptides, and antioxidants, function through hydration, cell signaling, epidermal renewal, and free radical neutralization. However, many formulations require the combination of photoprotection and encapsulation technologies to maximize delivery and skin tolerability. Given the growing market driven by contemporary aesthetic pressures, the pursuit of anti-aging treatments should be grounded in a scientific understanding of their chemical mechanisms and conscious consumer choices, avoiding the unnecessary or inappropriate use of potent products while promoting skin health and consumer safety.

Desenvolvimento de método para determinação de glicerol livre em biodiesel a partir da extração em barra de agitação revestida com celulose e quantificação por HPLC-DAD

Wed, 27 May 2026 00:00:00 GMT

Title: Desenvolvimento de método para determinação de glicerol livre em biodiesel a partir da extração em barra de agitação revestida com celulose e quantificação por HPLC-DAD Abstract: An analytical method based on stir-bar sorptive extraction (SBSE), using monolithic cellulose coated rods, coupled with high-performance liquid chromatography (HPLC), was developed for the determination of free glycerol in biodiesel. The sorbent phases were obtained by reprecipitation of cellulose acetate, followed by in situ deacetylation, resulting in a hierarchically porous structure with high surface area and high affinity for glycerol, mainly attributed to hydrogen bonding interactions between the hydroxyl groups of cellulose and the analyte. Structural characterization by FTIR, N2 adsorption/desorption isotherms, and BET/BJH analyses confirmed the efficient conversion of the precursor and the formation of a mesoporous structure suitable for adsorption and mass transfer processes. The extraction and desorption conditions in the SBSE technique were optimized using a multivariate design via the Doehlert Matrix. The extracts obtained were derivatized with benzoyl chloride, producing glyceryl tribenzoate, a species highly absorbent of UV radiation at 239 nm. Monolithic cellulose rods, 10 mm long, showed better analytical performance, with recoveries close to 100% and low variability in response during glycerol extraction. The maximum adsorption capacity was estimated at 63.0 μg g-1, consistent with the Langmuir model. The method was validated according to document SANTE 11312/2021.v2026, showing linearity between 0.00002 and 0.02000 % (w/w) (r = 0.9991), limits of detection and quantification of 7.8 × 10-6 and 2.4 × 10-5 % (w/w), respectively, as well as satisfactory precision (RSD < 7.5 %) and recovery rates between 94.7 and 113.9 %. The proposed method was successfully applied to the determination of free glycerol in biodiesels obtained from different raw material sources, with results in accordance with ASTM D6751 and EN 14214 standards. Compared to the official AOCS Ca 14 56 method, the proposed method showed greater analytical sensitivity and lower limits of detection. The sorbent bars demonstrated good stability after multiple reuse cycles, while the AGREEprep (0.77) and BAGI (75) metrics evidenced the reduced environmental impact of the methodology. Thus, the developed SBSE-HPLC method constitutes a simple, sensitive, selective, and environmentally sustainable alternative for the determination of free glycerol in biodiesel.

Eletrodos baseados em grafeno obtidos por gravação a laser: eletroanálise de amostras ambientais, biológicas e de alimento

Fri, 31 Jul 2026 00:00:00 GMT

Title: Eletrodos baseados em grafeno obtidos por gravação a laser: eletroanálise de amostras ambientais, biológicas e de alimento Abstract: Laser engraving has emerged as a promising technique for the rapid, simple, and low-cost fabrication of electrochemical sensors. In this thesis, laser-induced graphene (LIG) electrodes were fabricated through the direct engraving of polyimide using a CO₂ laser, aiming at the development of electrochemical methods for applications in food, environmental, and biological samples. To achieve this goal, the work was conducted in three stages. Initially, using unmodified LIG electrodes, a method was developed for the determination of total antioxidant capacity (TAC) in tea samples through the quantification of the consumption of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, employing batch injection analysis (BIA) with amperometric detection. The method exhibited a linear range from 2 to 900 μmol L⁻¹, a limit of detection (LOD) of 0.6 μmol L⁻¹, and high precision (relative standard deviation, RSD < 4.0%). The TAC of the samples followed the order: mixed tea < black tea < green tea < green tea with hibiscus, in agreement with the conventional spectrophotometric method. In a second stage, the applicability of these unmodified devices was extended to the determination of chloramphenicol in honey samples by adsorptive stripping differential pulse voltammetry (AdSDPV). This method showed linearity in the range of 10 to 160 μmol L⁻¹, an LOD of 1.0 μmol L⁻¹, and recovery values ranging from 86% to 109%. Finally, it was demonstrated, for the first time, that the application of only 3.0 μL of dimethyl sulfoxide (DMSO) onto the surface of LIG electrodes significantly enhances the electrochemical activity of the material. Physicochemical and electrochemical characterizations revealed changes in the chemical composition, structure, and surface morphology of LIG, including an increased concentration of oxygen-containing functional groups, structural reorganization favoring the formation of graphitic domains, enhanced hydrophilicity, increased surface roughness, and reduced charge-transfer resistance. Based on this surface modification strategy, a method was developed for the determination of sulfanilamide in water and synthetic urine samples using differential pulse cathodic stripping voltammetry (DPCSV). The method exhibited a linear response in the range of 0.3 to 9.0 μmol L⁻¹, an LOD of 0.09 μmol L⁻¹, and recovery values ranging from 90% to 104%. Overall, the results demonstrate that LIG-based electrodes constitute a versatile, efficient, and low-cost analytical platform. Furthermore, surface treatment with DMSO proved to be a simple and effective strategy for enhancing the electrochemical performance of LIG, thereby expanding its potential for the development of electrochemical sensors.

Desenvolvimento de monolitos compósitos hierarquicamente porosos de acetato de celulose funcionalizados com TiO₂ para remoção de corantes em soluções aquosas por adsorção e fotocatálise

Thu, 14 May 2026 00:00:00 GMT

Title: Desenvolvimento de monolitos compósitos hierarquicamente porosos de acetato de celulose funcionalizados com TiO₂ para remoção de corantes em soluções aquosas por adsorção e fotocatálise Abstract: The contamination of aquatic systems by organic dyes constitutes an important environmental problem due to the high chemical stability and low biodegradability of these compounds. In this work, hierarchically porous cellulose acetate monoliths (CAM), both pure and functionalized with TiO₂, were developed aiming at the removal of methylene blue and Rhodamine B dyes through combined adsorption and photocatalysis processes. The materials were obtained by non-solvent-induced phase separation, using DMF and 1-octanol, with the incorporation of different TiO₂ contents. The characterizations confirmed the formation of porous monolithic structures and the incorporation of the inorganic phase into the polymeric matrix. The presence of TiO₂ promoted morphological changes and a significant increase in the specific surface area, with the composites containing 2% and 11% TiO₂ standing out, presenting areas of 54.61 and 57.82 m² g⁻¹, respectively, compared to 23.17 m² g⁻¹ for the pure monolith. In the methylene blue adsorption assays, the materials showed a removal capacity influenced by the composition and porous structure of the monoliths. The kinetic data showed the best fit to the pseudo-second-order model, indicating that the adsorption process is mainly associated with interactions between the dye and the active sites present in the matrix, with contributions from surface area, porosity, and TiO₂ incorporation. In the cyclic adsorption/photocatalysis assays with methylene blue and Rhodamine B, the TiO₂-containing composites showed greater stability in removal capacity over four cycles, evidencing the contribution of photocatalysis to the partial regeneration of the adsorbent sites. Despite the observed diffusional limitations and structural heterogeneity, the results demonstrate that TiO₂-functionalized monoliths have potential for application in wastewater treatment processes, combining a renewable polymeric support, a hierarchically porous structure, and integrated photocatalytic activity.