Assessing the efficiency of low-cost cleaning methods for diatoms from intertidal sediment samples.

This study aims to compare the effectiveness of several low-cost reagents in obtaining high-quality diatom slides for microphytobenthos research. We evaluated the performance of eight reagents in sediment samples of beach intertidal zones. For each of the tested reagents, different pre-treatment conditions (pre-washed; non-washed) and three different temperatures (room temperature at 26 °C, 60 °C, and 100 °C) were also evaluated. For each treatment (combinations between reagents, temperatures, and pre-treatment conditions), we counted diatoms cells that met the criteria necessary for taxonomic identification (Whole/Half frustules or valves without cell material) in 30 randomly chosen fields of view in definitive preparations made from the treated samples. We also compared the treatments regarding species richness and diversity observed in the definitive preparations. The reagents influenced more the conditions of diatoms cells than the temperature and pre-treatment. H2O2, HNO3, NaClO were the methods that had the best performance in relation to the number of identifiable items. The six treatments with H2O2 presented similar amounts of identifiable items, regardless of pre-treatment and temperature. HNO3 presented a higher number of identifiable items in non-washed and pre-washed treatments at 60 °C and non-washed at 100 °C. NaClO had its best performance the following treatments: non-washed at room temperature and non-washed and pre-washed at 60 °C. H2O2 and HNO3 also showed better results for diatom species richness and diversity, followed by NaClO. The use of H2O2 was more robust since it obtained good results regardless of temperature and pre-treatments and should be preferred. HNO3 and NaClO should be used only with the appropriate temperatures, and pre-washing should be avoided.

Development of Quercetin Based Nanodispersions.

Polyphenols are a large group of structurally diverse natural products, including flavonoids. One of the most bioactive compounds of this class is the flavonol quercetin, a recognized antioxidant. Despite several studies were carried out aiming to develop nanoformulations with secondary metabolites, to our knowledge, quercetin was not used as raw material for nanodispersion production without coating polymers. This type of nanosize formulation is often prepared using organic solvents and quercetin nanodispersions were prepared by emulsification evaporation technique, using 1(6).2(2) experimental factorial design, ("surfactant type" evaluated at 6 levels, "surfactant amount" and "stirring speed" evaluated at 2 levels). Variance analysis, after one day of nanodispersions preparation, revealed that only the surfactant type was statistically significant on particle size, while none of factors presented statistically significant effect on polydispersity index. Variance analysis after seven days of nanodispersions preparation revealed that either surfactant type and surfactant amount presented significant effect on particle size, while only surfactant type influenced polydispersity index. Some nanodispersions presented small diameter and narrow size distribution, suggesting potential stability of these systems. Special attention was given to nanodispersion prepared with 3 % (w/w) of polyethylene glycol 400 monooleate (expressed as function of surfactant concentration at aqueous phase). It presented mean droplet size of 129.4 ± 0.5 nm and polydispersity index of 0.173 ± 0.018, after 7 days of preparation. Low polydispersity index indicates a high homogeneity concerning particle size distribution and suggests stability of the system. Moreover, absence of coating polymers and utilization of a low energy method would be an advantage in terms of reducing costs for industrial application, without any nanosize impairment.

Development of a larvicidal nanoemulsion with Copaiba (Copaifera duckei) oleoresin

Copaiba (Copaifera duckei Dwyer, Fabaceae) oleoresin is an important Amazonian raw material. Despite its insecticidal potential, poor water solubility remains a challenge for the development of effective and viable products. Nanotechnology has emerged as a promising area to solve this problem, especially oil-in-water nanoemulsions. On this context, the aim of the present study was to develop oil-in-water nanoemulsions using copaiba oleoresin dispersed through a high internal phase; and evaluate its potential insecticidal action against Aedes aegypti larvae. Overall, 31 formulations were prepared, ranging from 11.5 ± 0.2 to 257.3 ± 4.1 nm after one day of manipulation. Some of them reached small mean droplet sizes (< 200 nm) and allowed achievement of a nanoemulsion region. The formulation consisted of 5% (w/w) of copaiba oil, 5% (w/w) of surfactant and 90% (w/w) of water, which presented mean droplet size of 145.2 ±0.9 nm and polidispersity of 0.378 ± 0.009 after one day of manipulation, and these were evaluated for larvicidal potential. According to mortality level (250 ppm - 93.3 after 48 h), this nanoemulsion was classified as a promising insecticidal agent against Aedes aegypti larvae. The present study allowed the development of low-cost ecofriendly green natural-based nanoformulations with potential larvicidal activity, using a nanobiotechnology approach.