The kinetics of calcium alginate bead formation connected through light microscopy imaging, microstructure by SAXS and rheological analysis.

BACIGALUPE; AMODEO, GABRIELA; ESTEBAN TUBERT; ANA MERCEDES PERULLINI; ANDRÉS POSBEYIKIAN; PATRICIO SANTAPAGITA

San Luis

Congreso; XLVIII Reunión Anual de la Sociedad de Biofísica, 27 al 29 de Noviembre de 2019, Universidad de San Luis, San Luis.; 2019

SAB

Alginate encapsulation systems have grown in use across many fields, from agriculture to the food industry, medicine, and 3D tissue culture. Basically, alginate consists of linear blocks of alternated mannuronate and guluronate residues which can experience ionotropic gelation when they cross-link in presence of cations (e.g. Ca2+). During this process, the Ca(II)-alginate hydrogel (Ca-Alg) shrinksdue to the expulsion of water from aqueous pores reducing thebead final volume. Our goal was to perform a characterization of the Ca-Alg bead formation by means of complementary tools. First, we employed a video-microscopy set-up to record changes in bead cross-sectional area over time right after bead generation. The analysis of the digitized images was automatized using free distribution software (ImageJ & plug-ins). To improve the bead image contrast we tested fluorophores as well as a clay mineral, kaolinite. Results were compared to manual measurements performed with a caliper. Alginate systems ranging 1.5-3.0 % (w/v) were also tested. Methylene blue dye was used to stain the beads and a method was developed to track the layer of the 'gel front',that forms concentrically from the exterior of the alginate drop towards its interior. To determine the impact of the kaolinite and other dyes on the spatial arrangement of the alginate chains we studied the microstructureof the systems through small-angle X-ray scattering.Kaolinite caused a slight increase in the interconnectivity of the alginate rods at all alginate concentrations, but has no effect on the distance between alginate dimers. Rheological studies showed a correlation between the gelation kinetics andstress resistance.The rapid and convenient experimental design we here propose makes it possible to test a larger range of variables that affect the formationkinetics. Moreover, the characterization of the movement of this 'gel front' is proposed as a new attribute to describe alginate systems, and may reveal featuresregarding the dynamics of ionotropic gelation.Collectively, the described methodology facilitates easier characterization of alginate bead formation dynamics, which provides useful information both for industrial and scientific analysis of these systems.