Search

The search for new synthesis methodologies based on the principles of green chemistry has led to various studies for the production of silver nanoparticles (AgNPs) using extracts from different parts of plants. Based on this, the present study aims to carry out green synthesis (biosynthesis), characterization, and antibacterial evaluation of reduced and stabilized silver nanoparticles (AgNPs) with aqueous extracts of Minthostachys acris in a simple, ecological, and environmentally safe manner. The extraction process of the organic components is performed using two methods: immersion and the agitation of the leaves of Minthostachys acris Schmidt Lebuhn (Muña) at 0.1% for different times (0.5, 1, 3, 6, and 10 min). Compounds such as hydroxycinnamic acid derivatives, quinic, caffeic, rosmarinic acids, and flavonols present in the Muña extract facilitate the formation of AgNPs; this compounds act as a coating and stabilizing agent. The bioactive components from natural resources facilitate the formation of AgNPs, partially or completely replacing the contaminating and toxic elements present in chemical reagents. The biosynthesis is carried out at room temperature for pH 7 and 8. The synthesized AgNPs are characterized by UV-visible spectroscopy to identify the surface plasmon resonance (SPR) band, which shows an absorption peak around 419 nm and 423 nm for pH 7 and p.H 8, respectively, and Fourier-transform infrared spectroscopy (FTIR) to identify the possible biomolecules responsible for bioreduction and stabilization, with a peak at 1634 cm−1. Dynamic light scattering (DLS) shows the hydrodynamic size of the colloidal nanoparticles between 11 and 200 nm, and scanning electron microscopy (SEM) reveals monodisperse AgNPs of different morphologies, mostly nanospheres, while Laser-Induced Breakdown Spectroscopy (LIBS) demonstrates the presence of Ag in the colloidal solution. The evaluation of the bactericidal activity of the AgNPs using the disk diffusion method against Escherichia coli (E. coli) and Staphylococus aureus (S.aureus) shows that the synthesized AgNPs have effective antibacterial activity against E. coli for the extracts obtained at 6 min for both the immersion and agitation methods, respectively. The significance of this work lies in the use of bioactive components from plants to obtain AgNPs in a simple, rapid, and economical way, with potential applications in biomedical fields.

Modern consumption patterns have led to a surge in waste glass accumulating in municipal landfills, contributing to environmental pollution, especially in countries that do not have well-established recycling standards. While glass itself is 100% recyclable, the logistics and handling involved present significant challenges. Flint and amber-colored glass, often found in high quantities in municipal waste, can serve as valuable sources of raw materials. We propose an affordable route that requires just a thermal treatment of glass waste to obtain glass-based antimicrobial materials. The thermal treatment induces crystallized nanoregions, which are the primary factor responsible for the bactericidal effect of waste glass. As a result, coarse particles of flint waste glass that undergo thermal treatment at 720 °C show superior antimicrobial activity than amber waste glass. Glass-ceramic materials from flint waste glass, obtained by thermal treatment at 720 °C during 2 h, show antimicrobial activity against Escherichia coli after just 30 min of contact time. Laser-induced breakdown spectroscopy (LIBS) was employed to monitor the elemental composition of the glass waste. The obtained glass-ceramic material was structurally characterized by transmission electron microscopy, enabling the confirmation of the presence of nanocrystals embedded within the glass matrix.

Skin lesions are an important health concern, exposing the body to infection risks. Utilizing natural products containing chamomile (Chamomilla recutita L.) holds promise for curative purposes. Additionally, hyaluronic acid (HA), an active ingredient known for its tissue regeneration capacity, can expedite healing. In this study, we prepared and characterized an extract of C. recutita and integrated it into a nanoemulsion system stabilized with HA, aiming at harnessing its healing potential. We assessed the impact of alcoholic strength on flavonoid extraction and chemically characterized the extract using UHPLC/MS while quantifying its antioxidant and antimicrobial capacity. We developed a nanoemulsion loaded with C. recutita extract and evaluated the effect of HA stabilization on pH, droplet size, polydispersity index (PDI), zeta potential, and viscosity. Results indicated that 70% hydroalcoholic extraction yielded a higher flavonoid content. The extract exhibited antioxidant capacity in vitro, a desirable trait for skin regeneration, and demonstrated efficacy against key microbial strains (Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli, and Pseudomonas aeruginosa) associated with skin colonization and infections. Flavonoids spireoside and apiin emerged as the most abundant bioactives. The addition of HA led to increased viscosity while maintaining a suitable pH for topical application. Zeta potential, droplet size, and PDI met acceptable criteria. Moreover, incorporating C. recutita extract into the nanoemulsion enhanced its antimicrobial effect. Hence, the nanoemulsion system loaded with C. recutita and HA stabilization exhibits favorable characteristics for topical application, showing promise in aiding the healing processes.

The oxidation of primary and secondary alcohols to their respective aldehydes/ketones is one of the most important reactions in fine chemistry due to the industrial application of these products. Based on this, a large number of new catalysts and oxidants have been tested using this reaction as a catalytic model, mainly looking for a process that ensures high aldehyde selectivity. In this paper, we have used moisture stable borophosphate glass doped with 10 mol% Al2O3 as a heterogeneous catalyst in the oxidation of sodium hypochlorite, an effective, greener, and low-cost oxidant, using acetonitrile as solvent under mild conditions. The glass catalyst mass and the particle size were evaluated, as were the reaction temperature and oxidant amount, to determine the ideal reaction conditions where the conversions achieved 87.0 mol% for 1-phenylethanol to acetophenone and 79.4 mol% for benzyl alcohol to benzaldehyde, with benzaldehyde selectivity above 95%. Although sodium hypochlorite is a strong oxidant, benzaldehyde was the main product of the oxidation of benzyl alcohol due to the formation of a biphasic organic-aqueous system that protects the aldehyde from oxidation and allows the reaction to occur without the use of a phase transfer catalyst (PTC). HPLC analysis of both phases showed that alcohols, aldehyde, and ketone were mostly present in the organic phase (concentrations above 98.7%). During the reaction, a small amount of alcohol is transferred to the aqueous phase, where the oxidation took place. Once formed, the products are transferred back to the organic phase. ICP-OES analysis indicates that borophosphate glass acts in the reaction by partially releasing phosphate-based groups, reducing the pH of hypochlorite to 9. In this sense, borophosphate glasses prove to be a simple and inexpensive alternative for the development of new catalysts.

Due to the clinkerization process during the Portland cement production, large amounts of CO2 are emitted, increasing the effects related to climate change (approximately 5-10% of global CO2 emissions come from cement production), consequently, the seek for alternatives to mitigate these high emissions are necessary. The use of supplementary cementitious materials (SCM) to partial replace of Portand clinker/cement has been the subject of different research, including the use of LC3 cements (Limestone Calcined Clay Cements), where up to 50% of Portland clinker can be replaced, however, cement industry has already used other supplementary cementitious materials with pozzolanic activities in commercial cements. In this sense, this work evaluates the performance of concretes containing LC3 mixtures with the presence of different SCM (silica fume, fly ash, sugarcane bagasse ash and açaí stone ash) regarding durability issues by carbonation. The results showed that all concretes with LC3 presented higher carbonation fronts in relation to the reference concrete, with Portland cement, due to the lower availability of calcium to react with the CO2 that penetrates into the concrete pores, so the adoption of curing procedures and coatings are recommended.

The association between population increase and the exploitation of natural resources and climate change influences the demand for food, especially in semi-arid regions, highlighting the need for technologies that could provide cultivated species with better adaptation to agroecosystems. Additionally, developing cultivation technologies that employ waste materials is highly desirable for sustainable development. From this perspective, this study aimed to evaluate whether seed priming with glass waste microparticles used as a silicon source under red light irradiation mitigates the effects of thermal and water stress on seedlings of Moringa oleifera. The experimental design was set up in randomized blocks using a 2 × 2 × 2 factorial arrangement consisting of seed priming (NSP—no seed priming, and SPSi—seed priming with glass microparticles under red light irradiation), soil water replenishment (W50—50%, and W100—100% of crop evapotranspiration—ETc), and temperature change (TC30°—30 °C day/25 °C night and TC40°—40 °C day/35 °C night). Seed priming with glass microparticles under red light irradiation mitigated the effects of thermal and water stress on seedlings of Moringa oleifera seedlings through the homeostasis of gas exchange, leaf water status, osmotic adjustment, and the antioxidant mechanism.

A Kappaphycus alvarezii é a quinta macroalga mais cultivada do mundo e tem sido comercialmente cultivada no Estado de Santa Catarina desde 2020. Seu cultivo atualmente tem se voltado à produção de biofertilizante, todavia, a validação deste produto ainda é uma necessidade do setor. Assim, nesse estudo, objetivou-se analisar as respostas morfológica e bioquímica do uso do biofertilizante de K. alvarezii em plantas de manjericão (Ocimum basilicum) cultivadas em sistema hidropônico de produção. Utilizando as concentrações de 1%, 3%, 5% e 7%, com aplicação foliar semanal, constatou-se na análise morfológica que o biofertilizante, nas concentrações 3% e 5%, foi capaz de incrementar o número de nós, diferindo do controle. Além disso, a matéria seca da raiz também foi incrementada quando aplicado 5% do biofertilizante. Na análise bioquímica, observou-se incremento do teor de clorofila (1% e 5%), de açúcares solúveis totais (5% e 7%), do amido total (3%, 5% e 7%), de carboidratos totais (5% e 7%) e aminoácidos totais (5% e 7%) quando comparada ao controle. Esses resultados indicam que o biofertilizante de K. alvarezii pode ser uma alternativa promissora para o setor agrícola.

Kappaphycus alvarezii is a red seaweed used globally in various biotechnological processes. To ensure the content and stability of its bioactive compounds postharvest, suitable drying protocols must be adopted to provide high-quality raw materials for industrial use. This study aimed to analyze the influence of freeze-drying and oven-drying on the total phenolic content (TPC), total flavonoid content (TFC), antioxidant activity (FRAP and DPPH assays), total carotenoid content (TC), and lipase (LA) and protease activity (PA) of K. alvarezii samples collected over the seasons in sea farms in southern Brazil. The freeze-drying technique was found to be more effective regarding superior contents of TPC (39.23 to 127.74 mg GAE/100 g) and TC (10.27 to 75.33 μg/g), as well as DPPH (6.12 to 8.91 mg/100 g). In turn, oven-drying proved to be the best method regarding the TFC (4.99 to 12.29 mg QE/100 g) and PA (119.50 to 1485.09 U/g), with better performance in the FRAP (0.28 to 0.70 mmol/100 g). In this way, it appears that the drying process of the algal biomass can be selected depending on the required traits of the biomass for the intended industrial application. In terms of cost-effectiveness, drying the biomass using oven-drying can be considered appropriate.