Micropartículas de quitosana como suporte para bioativos: síntese, caracterização, atividade antimicrobiana e formulação cosmética

Abstract

Microplastics present in cosmetic products and cleaning agents, combined with improper disposal, have generated large amounts of environmental waste that are resistant to degradation. Thus, biopolymers are being used as an alternative to plastics due to their non-toxicity and shorter degradation time compared to synthetic polymers. Chitosan is a biopolymer synthesized from chitin, which is purified from exoskeletons, such as shrimp shells. This polymer contains functional groups that allow for modifications and crosslinking with bioactives, such as vanillin and gallic acid, in order to maintain and/or enhance the biological properties of each component. The aim of this study was the synthesis, characterization, and antimicrobial evaluation of chitosan microparticles crosslinked with bioactives, to create a product with sustainable properties, providing alternatives to the use of microplastics in cosmetic hygiene and cleaning formulations. The microparticles were synthesized using the gelation method, employing chitosan previously synthesized by the group. The chemical and physical crosslinking processes of chitosan in the microparticles were performed with the use of a reflux system and non-toxic solvents for 5 hours for vanillin and 24 hours for gallic acid. Chemical, physical, and biological characterizations were carried out. The microparticles ME-1V showed a retention of 26.5% with vanillin, while the ME-1V AG microparticles showed a retention of 23.7% with gallic acid, as determined by quantification using a developed UV-vis spectroscopy method. The ME-1V and ME-1V AG microparticles were predominantly stable in water, with different pH values (2.0; 7.0; 10.0). In the oil/water emulsion (cosmetic base), no swelling was observed in the ME-1V and ME-1V AG microparticles. The swelling degree of ME-1V was 97.4%, and of ME-1V AG was 142%. Infrared spectroscopy analysis showed the characteristic bands of chemical crosslinking of vanillin, with the formation of the imine (C=N) bond in the ME-1V microparticles, and physical crosslinking with gallic acid in the ME-1V AG microparticles, through hydrogen bonds, which were absent in the spectrum of the ME-1 microparticles containing only chitosan. Scanning electron microscopy images revealed well-defined, predominantly spherical shapes, with a smooth and homogeneous surface. The particle diameter ranged from 692-940 μm. Energy dispersive spectroscopy analysis indicated the main atomic constituents C, N, O present in chitosan, vanillin, and gallic acid. Thermal analyses demonstrated the stability of the crosslinked microparticles, with a particular emphasis on the thermal stability of the ME-1V AG microparticles, which showed 49.35% residue at 500ºC. Regarding antimicrobial potential, only ME-1V AG and the precursor bioactives (chitosan, vanillin, and gallic acid) exhibited this capacity, particularly against the Gram-negative bacterium Escherichia coli. Thus, both ME-1V and ME-1V AG microparticles demonstrated suitable characteristics for alternative use in cosmetic hygiene and cleaning formulations, as replacements for microplastics. Finally, it is concluded that the results obtained in this study align with the principles of sustainability defined by the sustainable development goals, while also adding value to the raw materials in the development of new materials.