Percorrer por autor "Correa, Rodolpho Fagundes"
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- Chitosan crosslinking strategies having in view greener microencapsulation processesPublication . Correa, Rodolpho Fagundes; Barreiro, M.F.; Fernandes, Isabel P.; Blanco, Silvia Priscila Dias MonteCurrently, several industrial sectors, including the cosmetic industry, are interested in the development of innovative formulations and microencapsulation can be introduced as a technique to confer stabilization and controlled release to biofunctional principles. In this context, the use of natural or natural-derived polymers as encapsulating materials, such as chitosan (CS), and the application of emerging strategies for their crosslinking, to avoid typical toxic crosslinkers, are of high research interest. Therefore, the use of vanillin (VA) and citric acid (CA) as greener alternatives for CS crosslinking was studied, conjointly with tripolyphosphate (TPP), using the spray-coagulation technique. Firstly, a systematic study was accomplished by atomizing a solution of CS 3% (w/v) in acetic acid 3% (v/v) into different tested TPP concentrations (CTPP: 10, 5 and 3% (w/v)), as the coagulation agent and physical crosslinker. Following, the resulting control microspheres underwent covalent crosslinking with a VA solution of 1% (w/v), testing different reacting conditions: (1) the VA solution was added, under controlled flow, to the coagulation TPP bath containing the microparticles; (2) the microparticles were recovered by vacuum filtration from the coagulation TPP bath, followed by addition into the VA solution. The microparticles were characterized by optical microscopy (OM) to monitor morphology and particle size, Fourier-transform infrared spectroscopy (FTIR) to inspect biopolymeric structure rearrangement, thermogravimetric analysis (TGA) to assess thermal behaviour, scanning electron microscopy (SEM) to check final particle morphology. Moreover, swelling tests in acidic medium were also conducted to check the crosslinking effectiveness. As main results, the OM showed the formation of consolidated spherical micro-sized particles, upon atomization in TPP, due to the physical crosslinking via electrostatic interactions. FTIR analysis confirmed CS structural changes derived from VA crosslinking reaction via Schiff base (C=N) formation and hydrogen bonding. Moreover, TGA thermograms also evidenced CS structural modifications, as the degradation temperature was intermediate to the base CS and VA, and the final residue weight increased. Also, VA lowered microparticle disintegration and swelling degree, granting stabilization to the microsystems. Finally, the microspheres comprised by the use of 5% TPP content and crosslinked via approach (1) was outlined and proposed for microencapsulation of bioactive principals. Preliminary studies using CA as the crosslinker were also performed, showing an alternative to be explored in future works.
- Development of chitosan microspheres through a green dual crosslinking strategy based on tripolyphosphate and vanillinPublication . Correa, Rodolpho Fagundes; Colucci, Giovana; Halla, Noureddine; Pinto, João A.; Santamaria-Echart, Arantzazu; Blanco, Silvia Priscila; Fernandes, Isabel P.; Barreiro, M.F.Microencapsulation procedures have recently focused attention on designing novel mi-crospheres via green synthesis strategies. The use of chitosan (CS) as an encapsulating material has increased interest due to its unique bioactive properties and the various crosslinking possibilities offered by their functional groups. The consolidation of the microspheres by physical crosslinking using sodium tripolyphosphate (TPP) combined with chemical crosslinking using vanillin (VA) open new opportunities in the framework of green dual crosslinking strategies. The developed strategy, a straightforward technique based on an aqueous medium avoiding complex separa-tion/washing steps, offers advantages over the processes based on VA, mostly using water-in-oil emulsion approaches. Thus, in this work, the combination of TPP crosslinking (3, 5, and 10 wt.%) via spray-coagulation technique with two VA crosslinking methods (in situ and post-treatment using 1 wt.% VA) were employed in the preparation of microspheres. The microspheres were characterized concerning morphology, particle size, physicochemical properties, thermal stability, and swelling behavior. Results revealed that the combination of 5 wt.% TPP with in situ VA crosslinking led to microspheres with promising properties, being an attractive alternative for natural bioactives encapsulation due to the green connotations associated with the process.