Monoolein-based nanodispersions for cutaneous co-delivery of methylene blue and metformin: Thermal and structural characterization and effects on the cutaneous barrier, skin penetration and cytotoxicity.

This study evaluated the potential of monoolein (MO)-based nanodispersions to promote the cutaneous co-delivery of metformin (MET) and methylene blue (MB) for the treatment of non-melanoma skin cancer. MO-based nanodispersions were obtained using Kolliphor® P407 (KP) and/or sodium cholate (CH), and characterized concerning the structure, thermal stability, ability to disrupt the skin barrier, cutaneous permeation and retention of MB and MET. Additionally, the cytotoxic effect of MO nanodispersions-mediated combination therapy using MET and MB in A431 cells was evaluated. The nanodispersions exhibited nanometric size (<200 nm) and thermal and physical stability. Small angle X-ray scattering studies revealed multiple structures depending on composition. They were able to interact with stratum corneum lipid structure, increasing its fluidity. The effect of MO-nanodispersions on topical/transdermal delivery of MB and MET was composition-dependent. Nanodispersions with low MO content (5 %) and stabilized with KP and CH (0.05-0.10 %) were the most promising, enhancing the cutaneous delivery of MB and MET by 1.9 to 2.2-fold and 1.4 to 1.7-fold, respectively, compared to control. Cytotoxic studies revealed that the most promising MO nanodispersion-mediated combination therapy using MET and MB (1:1) reduced the IC50 by 24-fold, compared to MB solution, and a further reduction (1.5-fold) was observed by MB photoactivation.

Development of a Nanotechnology Matrix-Based Citronella Oil Insect Repellent to Obtain a Prolonged Effect and Evaluation of the Safety and Efficacy.

Mosquito-borne diseases affect millions of people worldwide each year, and the use of a topically applied insect repellent is an economically viable preventative health practice. The general objective of this work was to encapsulate citronella oil (CO) in a nanostructured lipid carrier (NLC) to formulate a topical repellent with a long duration of efficacy on the skin and a good safety profile based on minimizing skin penetration. In the studied CO, the main chemical constituents of geraniol, citronellal, and citronellol were identified and subsequently used as markers for the in vitro skin permeation testing (IVPT). An optimal NLC encapsulating CO formulation was developed and had an average particle size of 350 nm. The NLC was then formulated in combination with CO at ratios of 2:1, 1:1, and 1:2 CO:NLC-CO as oil-in-water (O/W) emulsions and compared to CO in the same O/W emulsion base (all at 10% CO in the final O/W topical formulation). The markers geraniol, citronellol, and citronellal were detected in all samples tested F1 (10% CO in O/W emulsion) and F3 (10% CO/NLC-CO 1:1 in O/W emulsion). Even the percentages of F3 markers were higher than F1. The recovery of the percentage balance (based on the total remaining on the skin surface, on the skin, and penetrated through the skin to the receptor) of geraniol, citronellol, and citronellal markers for F1 and F3 was 7.70% and 11.96%; 25.51% and 31.89%; and 5.09% and 4.40%, respectively. The nanoparticle lipid solid forms a repellent reservoir on the skin surface, releasing the active ingredients slowly through volatilization, extending the repellent action, and reducing permeation through the skin. It is possible to assume that the remaining 92.30% and 88.03%; 74.49% and 68.11%; and 94.10% and 95.60% of geraniol, citronellol, and citronellal markers of F1 and F3, respectively, were lost to evaporation. In the in vivo efficacy test carried out with the Aedes aegypti mosquito, F3 was the optimal formulation, providing the greatest repellent action compared to free oil in O/W emulsion. Thermal analysis showed that the NLC-CO raised the boiling point of the encapsulated CO compared to the free oil, suggesting that the controlled release of the CO was a possible mechanism for its prolonged effect. We concluded that the nanocarriers developed with CO were stable and provided improved mosquito-repellent efficacy with minimal skin penetration of the CO actives over 24 h. Indeed, regardless of whether the CO was applied as free oil, a 1:1 mixture of CO (pure/free oil) or NLC-CO applied in an O/W emulsion can be considered safe for topical application due to minimal skin penetration.

Mineral sorbents for ammonium recycling from industry to agriculture.

In tropical environments, nutrient-poor soils are commonly found, leading to high fertilizers application rates to support agricultural activities. In contrast, anthropogenic activities generate large amounts of effluents containing nitrogen. In this study, two minerals (natural zeolite and vermiculite) were tested to remove NH4+ from an industrial effluent with high pH and contents in Na+ and K+. Afterwards, they were tested as an alternative slow-release fertilizer in the soil. To verify the best conditions to adsorb NH4+, batch tests were conducted using synthetic solutions and an industrial effluent. In general, the efficiency of both minerals in removing NH4+ was high (85% for zeolite and almost 70% for vermiculite) as well as the ability to decrease the industrial effluent pH. In this process, more NH4+ and K+ ions were removed in comparison with Na+, which remained in solution. These minerals were tested as slow-release fertilizers by leaching with distilled water (both minerals releasing 2 mg L-1 NH4+) and with an acid solution (releasing 10 mg L-1 NH4+ from zeolite and 50 mg L-1 NH4+ from vermiculite-corresponding only to 12% of total NH4+ retained by zeolite and 29% by vermiculite). During the test of soil incubation with zeolite-NH4+, the NH4+ ions of the exchangeable sites were retained for a longer period, minimizing their loss by leaching and biological nitrification. Consequently, soil acidification was prevented. Therefore, both minerals showed high efficiency in removing NH4+ from solution which can then be slowly released as a nutrient in the soil.

Urea incorporated into ordered mesoporous silica for potential cosmetic application

Urea's thermal instability and burning on sensitive skin can cause problems for cosmetic formulations. To overcome these drawbacks, urea was incorporated into ordered mesoporous silica (SBA-15). SBA-15 was synthesized using tetraethyl orthosilicate and Pluronic® P123 in an acid medium. Urea (20 wt.%) was incorporated into calcined SBA-15 by the incipient wetness impregnation method. Several techniques were used to characterize the samples. Skin hydration and transepidermal water loss were measured using Corneometer® CM 825 PC and Tewameter® 300 TM. Results showed that the structural properties of SBA-15Urea were similar to pure SBA-15, indicating that SBA-15 remained structured even after urea incorporation. Nitrogen physisorption data showed the volume and surface area of the pores in SBA-15Urea were much lower than those in SBA-15, demonstrating that urea was deposited inside the mesopores. In vivo moisturization studies revealed that SBA-15Urea was not able to reduce transepidermal water loss compared to the other products and control, while forming a non-occlusive surface film on the skin. We conclude that incorporation of urea in the pores of the inorganic SBA-15 matrix is a promising approach to enhancing its stability and providing a prolonged moisturizing effect.