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The tailor-made character of deep eutectic solvents (DES) turns them very attractive to be used in several applications, including in health-related areas such as pharmaceutical, nutraceutical, and cosmetic industries. However, although DES has been touted as “green” solvents, several works proved that their potential toxicity should not be neglected. Using the premise of DES applicability in the cosmetic and pharmaceutical sectors, we chose two cell lines to work as a skin model (keratinocytes HaCaT and tumor melanocytes MNT-1), to assess DES cytotoxicity. The effect of three different hydrogen bond acceptors (HBA) ([Chol]Cl, [N 1111 ]Cl and [N 4444 ]Cl) and three different hydrogen bond donors (HBD) (hexanoic and butanoic acid, ethylene glycol, 1-propanol and urea) were evaluated through a common viability assay (MTT assay). Results were promising since [Chol]Cl and [N 1111 ]Cl- based DES showed good biocompatibility for the tested cells. [N 4444 ]Cl-based DES, however, showed cytotoxicity for both cell lines, with the HBA being the driver of the toxicity. Interestingly, some compounds increased cell viability in the HaCaT cell line, namely [Chol]Cl, ethylene glycol, hexanoic acid, urea, and all [Chol]Cl and [N 1111 ]Cl-based DES and should be considered as targets for future studies. These results highlight their possible use in cosmetic or pharmaceutical formulations.

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Chitin is a natural biomass resource with high potential for a wide variety of applications. However, it remains poorly explored because of its solubility issues. In this work, a large range of acidic deep eutectic solvents (aDESs), combining different hydrogen bond acceptors [betaine (Bet), urea (U), and cholinium chloride (CC)] and hydrogen bond donors [formic acid (FA), acetic acid (AA) propanoic acid (PA), and lactic acid (LA)], were investigated. First, the ability of the aDESs to dissolve commercial chitin was compared and then, based on the solubility data obtained, the most efficient aDESs were chosen to extract chitin directly from red crayfish shell wastes. Considering that up to 10 wt % of commercial chitin was dissolved in the aDES CC:LA 1:2 and Bet:LA 1:2, these were further applied to extract chitin from crayfish shell wastes. Using these aDES as solvents, a high-quality chitin was obtained with a crystallinity index >80%, and a degree of acetylation >90%. The findings demonstrated the suitability of aDESs to enhance dissolution and hence to efficiently extract chitin from different raw biomass without compromising the polymer structural integrity.

The Internet of Things (IoT) fosters the development of smart city systems for sustainable living and increases comfort for people. One of the current challenges for sustainable buildings is the optimization of energy management. Temperature monitoring in buildings is of prime importance, as heating account for a great part of the total energy consumption. Here, a solar optical temperature sensor is presented with a thermal sensitivity of up to 1.23% °C−1 based on sustainable aqueous solutions of enhanced green fluorescent protein and C‐phycocyanin from biological feedstocks. These photonic sensors are presented under the configuration of luminescent solar concentrators widely proposed as a solution to integrate energy‐generating devices in buildings, as windows or façades. The developed mobile sensor is inserted in IoT context through the development of a self‐powered system able to measure, record, and send data to a user‐friendly website.