Percorrer por autor "Namba, Danillo Yuji"
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- Microencapsulation involving chitosan enzyme-induced crosslinkingPublication . Namba, Danillo Yuji; Barreiro, M.F.; Santamaria-Echart, Arantzazu; Marin, PricilaMicroencapsulation techniques are known to be applied in several industrial fields. Nevertheless, the recent concern about avoiding methodologies that involve hazardous chemicals, generally associated with environmental impacts and adverse effects on human’s health, has focused attention on alternative sustainable approaches. In this context, the objective of the work focused on using chitosan (CS), combined with gelatin (GE) through the emerging enzyme-induced crosslinking approach, in particular, transglutaminase (TGase) to consolidate the particles, avoiding traditionally used chemical crosslinking routes. This approach was also complemented with the physical crosslinking strategy with tripolyphosphate (TPP). Thus, through the dripping technique, the preparation of the particles was consolidated by an external physical crosslinking, being later subjected to an internal covalent crosslinking to reinforce their structure. The synthesis conditions and particles composition were optimized by a design of experiments approach, specifically through a central composite rotatable design (CCRD). The gelatin content (x1, % wt), TGase concentration (x2, U/ggel) and reticulation time (x3, min) variables were analysed, considering as the evaluating responses, the water content after particles production (Y1, %wt), the swelling degree (SD) at pH 3 for 2 h (Y2, %wt), SD at pH 7 for 6 h (Y3, %wt) and SD in continuous, i.e. subjecting the same sample at pH 3 followed by 7 for 2 h and 6 h (Y4, %wt). The selected pHs and corresponding swelling times, namely pH 3 (2 h) and pH 7 (6 h), were determined to simulate gastrointestinal digestion conditions. It was pursued to determine the most suitable formulation with potential to be loaded with bioactive compounds in later steps, providing them protection during the gastric digestion and to be released later in the intestine. Apart from the simulated gastrointestinal conditions through swelling degree (SD) tests, the particles were also characterized by means of optical microscopy (OM) and by Fourier-transform infrared spectroscopy (FTIR), aiming at monitoring the particle’s morphology and structure variations during the digestion process, as well as to identify the functional groups and interactions and analyse their evolution in the SD tests. Since the responses Y2, Y3 and Y4 did not fit to determine their predictive model in a first experimental design (CCRD1), it was required to develop a second one (CCRD2) considering the increase in the study interval of variables x2 and x3 responsible for the chemical crosslinking. The results of CCRD2 allowed to obtain valid models for Y1, Y2 and Y4 responses. Therefore, based on the models, an optimized formulation (5%wt gelatin; 36 U/ggel of TGase, and 60 min of TGase crosslinking) was defined and prepared to validate the predicted models and to verify its potential to be later loaded with bioactive compounds. Concurrently, the OM images confirmed the consolidation of the particles as well as their changes in the simulated gastrointestinal conditions, while the FTIR analyses confirmed the structural changes in CS (and GE) due to the physical and chemical crosslinking through TPP and TGase, respectively. In view of the need of novel environmentally friendly methodologies, the present work has shown the potential of developing strategies to comply with sustainable goals, while providing a promising natural biomaterial for the protection and delivery of bioactive compounds in specific conditions.