Photodynamic therapy (PDT) is a therapeutic modality that has shown effectiveness in the inactivation of cancer cell lines and microorganisms. Treatment consists of activating the photosensitizer (PS) upon light irradiation of adequate wavelength. After reaching the excited state, the PS can handle the intersystem conversion through energy transfer to the molecular oxygen, generating reactive oxygen species. This especially applies to singlet oxygen (O), which is responsible for the selective destruction of the sick tissue. Photosensitizing compounds (chlorophylls and derivatives) existing in the spinach extract have applicability for PDT. This study aimed to develop and characterize the thermoresponsive bioadhesive system composed of Pluronic F127 20.0%- and Carbopol 934P 0.2% (w/w) (FC)-containing chlorophyll-based extract 0.5% (w/w) (FC-Chl). Mechanical and rheological properties, in vitro release, sol-gel transition temperature, and ex vivo permeability of the spinach extract PS components (through pig ear skin) were investigated. Furthermore, photodynamic activity of the system was accessed through uric acid and time-solved measurements. The sol-gel transition temperature obtained for the FC-Chl system was 28.8 ± 0.3 °C. Rheological and texture properties of the platform were suitable for use as a dermatological system, exhibiting easy application and good characteristics of retention in the place of administration. In vitro release studies showed the presence of two distinct mechanisms that reasonably obey the zero-order and first-order kinetics models. PS components presented skin permeability and reached a permeation depth of 830 μm (between the epidermis and dermis). The photodynamic evaluation of the FC-Chl system was effective in the degradation of uric acid. The quantum yield (ΦO) and life time (τO) of singlet oxygen showed similar values for the spinach extract and the isolated chlorophyll a species in ethanol. These results allowed for the classification of the FC-Chl platform as potentially useful for the delivery of the chlorophyll-based extract in the topic PDT, suggesting that it is worthy for in vivo evaluation.

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In this work, a novel renewable taurine-based ionic liquid (IL), [TauIm][HSO 4 ], was synthesized via the Debus− Radziszewski reaction. The synthesized IL was then used to produce ethyl levulinate (EL) from several lignocellulosic substrates under microwave irradiation. Experimental conditions (temperature, time, and IL quantity) for EL production from a model substrate (microcrystalline cellulose, MCC) were first investigated by design of experiment (DoE) using a central composite design (CCD). The highest EL yields (over 80%) in MCC were achieved at the upper limits of all factors (190 °C; 60 min; 10 equiv of IL). Computational studies revealed that the IL−cellobiose interaction is stronger than the IL itself at the reaction temperature (190 °C), indicating the efficiency of the IL in interacting with cellulose in the optimal reaction conditions. Moreover, the formation of the IL− cellobiose complex was mediated by the hydrogen sulfate anion, while the cation worked as a spacer. Optimized conditions from DoE were also applied to sugarcane bagasse and straw, elephant grass leaves and stems, rice husks and straw, and corn biomass. EL production yields from 12 to 59% were obtained from these biomasses using this novel imidazolium IL, with the highest EL yields obtained with raw sugarcane bagasse (SCB) without any pretreatments. The superior performance of SCB was associated with the higher content of hemicelluloses in its composition compared to that of the other biomasses. Together, these results presented herein open new possibilities for increasing biomass valorization using renewable and straightforward routes.

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