Wounds in Mexico pose a significant public health challenge. The direct monthly costs for outpatient treatment are estimated to exceed 46 million pesos, while hospitalizations amount to around two billion pesos, placing a considerable financial burden on the country's health sector. The national prevalence of pressure wounds is reported at 12.92%. Furthermore, other types of wounds, such as diabetic foot ulcers, surgical wounds, trauma, burns, and vascular ulcers, are also highly prevalent in the country. Thus, the pursuit of new, sustainable, and cost-effective treatments that expedite healing is an area of ongoing research. The aim of this study was to develop a coating made from gelatin and deep eutectic solvents (DES), incorporated with quercetin and rutin, and to characterize its mechanical and spectroscopic properties. Additionally, we proposed the use of fruit anthocyanins as pH-sensitive molecules to create a colorimetric sensor that indicates pH changes in wounds. To prepare the DES, betaine was used as a hydrogen bond acceptor and glycerol as a donor, mixed in a 1:2 molar ratio, along with 20% (w/w) distilled water. The mixture was heated to 80 °C for 45 min until it became homogeneous and transparent. For the production of the eutectogel, 22% gelatin, 77% of the prepared DES, and 1%, 2.5%, or 5% of quercetin or rutin (with the proportion used subtracted from the DES) were combined. This mixture was again heated to 80 °C with constant stirring for 45 minutes until it clarified, then poured into silicone molds and allowed to cool to 10 °C. Once the eutectogels were formed, they underwent mechanical characterization in both compression and tension using a Zwick-Roell universal testing machine. Functional groups were characterized using FTIR spectroscopy. Thirteen hydrogen bond donors of various chemical natures were employed for anthocyanin extraction, including carboxylic acids, polyols, and sugars. Two hydrogen bond acceptors were also evaluated: choline chloride and betaine. This resulted in a total of 27 different DES created using varying molar ratios. The extraction process was assisted by ultrasound, at 50°C, 45 min and 50 mg/mL utilized freeze-dried blueberry, blackberry, and hibiscus calyx. Quantification of the anthocyanins was performed through UV-Vis spectrophotometry at a wavelength of 535 nm. As results, the eutectogels reached maximum compressive stresses of up to 40 MPa under 90% strain, suggesting that as the concentration of flavonoids increased, the stress also increased due to the formation of a hydrogen bond network. This network was formed between the hydrophilic amino acids present in the gelatin, the hydroxyl groups of the flavonoids, and the hydroxyl groups of glycerol found in the DES. In terms of tensile properties, the eutectogels exhibited a deformation of up to 300%, with stress levels ranging from 300 to 400 kPa. The predominant functional groups identified in the IR spectra were those associated with the DES (-OH, C=O, C-O), while characteristics indicative of gelatin or flavonoids were not observed. Regarding anthocyanin extraction, higher yields were observed from blueberry and hibiscus. Notably, DESs containing carboxylic acids as hydrogen bond donors and choline chloride as a hydrogen bond acceptor yielded the best results. In the next phase of the project, extracts will be incorporated into the eutectogels, and colorimetric changes will be assessed at different pH levels. The mechanical and spectroscopic properties will also be reevaluated to determine any modifications caused by the addition of the extracts. Furthermore, UV-Vis release profiling will be conducted, along with an assessment of the antibacterial properties of the extracts.

We thank M.I. Gerardo Fonseca for his support in carrying out the mechanical tests.