Abstract
Aggregation and coalescence are major drawbacks that contribute to polydispersity in microparticles and nanoparticles fabricated from diverse biopolymers. This study presents the evaluation of a novel method for the direct, electrospray-induced fabrication of small, CaCl2/ethanol-hardened low methoxy pectin/arabinoxylans composite microbeads. The electrospray method was evaluated to control particle size by adjusting voltage, flux, and crosslinking solution content of CaCl2/ethanol. A bead diameter of 1µm was set as reference to test the capability of this method. Insulin was chosen as a model carried molecule. Statistical analysis was a central composite rotatable design (CCRD) with a factorial arrangement of 24. The variables studied were magnitude and particle size dispersion. For the determination of these variables, light diffraction techniques, scanning electron microscopy, transmission electron microscopy, and confocal laser scanning microscopy were used. Major interaction was found for ethanol and CaCl2 as well as flow and voltage. Stable spherical structures of core–shell beads were obtained with neither aggregation nor coalescence for all treatments where ethanol was included in the crosslinking solution, and the average diameter within 1 ± 0.024 μm for 11 KV, 75% ethanol with 11% CaCl2, and flow of 0.97 mL/h.
Highlights
Polysaccharides are widely used as protectors and carriers and are generally considered non-toxic and biocompatible materials
The production of beads by coaxial electrospray was carried out using DTA pectin solutions and AXF-insulin solution
The very low degree of esterification accelerated the nucleation process with calcium, creating an exterior “crust” stable enough to keep droplets from gelling together and maintain the spherical structure of the droplets formed in the electrospray
Summary
Polysaccharides are widely used as protectors and carriers and are generally considered non-toxic and biocompatible materials. The gelling mechanism of pectin depends on the degree of esterification of the galacturonic acid contained in the pectin chain [8]. Low degree of esterification (LDE) pectin gels in the presence of divalent ions (i.e., Ca2+ ) forming a structure called an “egg box” [9]. This mechanism is a fast process, which provides stability and strength to the gel, tough sensitive to pH [10]. Arabinoxylans are commonly found in the cell wall of Poaceae species, like grasses and gramineae [11]. The polymeric chain consists of xylose in β-1,4 with ramifications of Polymers 2018, 10, 108; doi:10.3390/polym10020108 www.mdpi.com/journal/polymers
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