(197i) Comparison of Chitosan Particles Produced By Ionic Gelation and By Supercritical Assisted Atomization

Chitosan is a biodegradable, biocompatible, biological polymer with low toxicity, antimicrobial activity and mucoadhesive properties. Such characteristics make it interesting for use as a controlled release system for a wide variety of drugs. The production of pure chitosan particles or incorporating active compounds can be performed by different methods. In the conventional techniques, for example emulsion, there are some disadvantage such as the difficulty of controlling the particles size and the use of organic solvents, requiring post-processing steps of the particles. Due to these limitations, new techniques such as supercritical technologies, which have the advantage of obtaining particles with greater purity, the possibility of processing thermosensitive molecules and the exemption or drastic reduction in the amount of organic solvents used in production. In this work, a comparison of the particles obtained by ionic gelation methods with the use of TPP obtained (sodium tripolyphosphate) and SAA (Supercritical assisted atomization) technique is carried out. The particles were prepared by ionic gelation, according to the method established by Calvo et al. (1997) where acid solutions of chitosan (0.5-2.0 mg/ml) (low molar mass, deacetylation grade of 93.1%) are mixed with TPP solution by HPLC pump. Stirring was maintained at 11000 rpm (Ultraturrax). The preparation of the particles by SAA was based on the techniques of Reverchon (2006) and Wu et al. (2015). This process is based on the use of a saturator (filled with glass beads) with a temperature ranging from 40-90°C, where the solution of ethanol
(50% v/v), chitosan (0.5-2.0 mg/ml) in acid medium contacts a supercritical CO₂ stream for a period of time to ensure saturation. This mixture is atomized by a capillary tube and sprayed on the precipitator (CO₂ velocity 4.0-9.6 cm³/min with CO₂ / solution ration of 1.8) together with nitrogen (at high temperature), which has an auxiliary purpose in the evaporation of the used solvent. The characterization of the chitosan particles produced by ionic gelling and SAA were carried out by Dynamic Light Scattering (DLS) analysis and Scanning Electron Microscope (SEM). The particles had zeta potential at least +30 mV, preventing aggregation of the particles. Particles of smaller sizes were obtained by the ionic gelation process at low concentrations of chitosan, the increase of the particle size with the decrease of the zeta potential was also observed. In SAA, the smallest particles were obtained in lower concentrations of chitosan, where it was observed the predominance of the nucleation process in detriment to the growth process.

References:

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3. Calvo, P., Remuñán-Lopez, C., Vila-Jato, J.L., Alonso, M.J. Novel hydrophilic chitosan-polyethylene oxide nanoparticles as protein carriers. International Applied Polymers Science, 63, 125-132, 1997.