Percorrer por autor "Alsayyed, Rahaf Marwan"
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- Polyelectrolyte complexes from chitosan and carrageenan: optimization by response surface methodology and method validationPublication . Alsayyed, Rahaf Marwan; Grenha, Ana Margarida MoutinhoPolyelectrolyte complexes (PECs) are important emerging materials in the pharmaceutical industry, especially because they are easily prepared in mild conditions, devoid of organic solvents and other harsh conditions. So far, a large number of scientific articles has been published reporting the possible applications of PECs as drug carriers. Polyelectrolytes own unique features, as they join the properties of polymers and electrolytes. These features turn PECs sensitive to the surrounding environment, such as salt concentration, that can considerably alter their formation and characteristics. Therefore, this work encompassed establishing an experimental design to optimize the formation of PECs from two polyelectrolytes, chitosan (CS) and carrageenan (CRG), in the absence and presence of NaCl in different concentrations. For that, preliminary studies were conducted to determine the solubility of CS and CRG in NaCl solutions, as well as the isoelectric point of PECs. Afterwards, an experimental design was established using response surface methodology to predict the size and zeta potential of the PECs, as well as the yield (measured as turbidity) of the obtained colloid. The design was constructed over a range of CS, CRG and NaCl concentrations that varied from 0 to 2 mM, 0 to 1.67 mM, and 0 to 0.06 M, respectively. Response surfaces and contour diagrams that represent the variations of size and zeta potential with the variation of the concentrations of CS, CRG and NaCl were obtained. Under the tested conditions, nanoparticles ranging in 280 - 700 nm and showing ±49 mV of zeta potential were obtained. The design was later validated and was found to predict with high desirability the size and zeta potential of PECs, but unfortunately failed to predict the yield. As a conclusion, PECs formation from CS and CRG in NaCl solutions can be optimized using the experimental design from this study, which resulted in a model that can predict with high credibility the conditions leading to the formation of particles with specific size and zeta potential.