What is the role of NaCl in this preparation? And did you use any pH adjustment for preparation of Chitosan Nanoparticles?
Article Effects of ionic strength on the size and compactness of chi...
Charge screening with electrolytes such as NaCl weakens charge repulsion between the chitosan molecules and leads to shrinkage of nanoparticles and NaCl even effect diffusion, particle size and zeta potential of CH-TPP nanoparticles. At a critical low pH, most of the amino groups of chitosan are protonated, enabling the chitosan molecule with an extension confirmation due to strong charge repulsion. The TPP molecule is also protonated, leading to lower charging density of the molecule. In this case, the chitosan molecules cannot be sufficiently cross-linked by TPP to form stable particles. Along with increase of the pH value, the deprotonation degree of TPP is increased gradually, while the protonation degree of chitosan is less influenced when the pH value is below 5. At a proper pH such as pH 3.5, the charge interaction between these two molecules becomes strong enough, thus stable chitosan nanoparticles are obtained with a relatively larger size. At a still higher pH value, the charging degree of TPP molecule is enhanced again, which neutralizes the chitosan to a greater extent. Consequently, the particles shrink their size again.
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it is neutral salt it will use for mimic buffer composition similar to in-vivo and their is no significant affect on pH. For chitosan nanoparticles for pH adjustment use NaoH or HCl in my work i used NaoH but you should add carefully it effect on protonation of chitosan and most interestingly the suitable pH for monodisperse chitosan nanoparticle was 3-4.5.
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Charge screening with electrolytes such as NaCl weakens charge repulsion between the chitosan molecules and leads to shrinkage of nanoparticles and NaCl even effect diffusion, particle size and zeta potential of CH-TPP nanoparticles. At a critical low pH, most of the amino groups of chitosan are protonated, enabling the chitosan molecule with an extension confirmation due to strong charge repulsion. The TPP molecule is also protonated, leading to lower charging density of the molecule. In this case, the chitosan molecules cannot be sufficiently cross-linked by TPP to form stable particles. Along with increase of the pH value, the deprotonation degree of TPP is increased gradually, while the protonation degree of chitosan is less influenced when the pH value is below 5. At a proper pH such as pH 3.5, the charge interaction between these two molecules becomes strong enough, thus stable chitosan nanoparticles are obtained with a relatively larger size. At a still higher pH value, the charging degree of TPP molecule is enhanced again, which neutralizes the chitosan to a greater extent. Consequently, the particles shrink their size again.
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One basic point was mentioned by Sheetu. Without electrolytes, dissociated (like charged) groups of the macromolecules repel each other and counteract attractive forces between hydrophobic parts of the macromolecules. Therefore the macromolecules have an extended conformation. Adding electrolyte the reach of electrostatic repulsion is reduced and the attractive intramolecular forces gain importance leading to a collapsed conformation. This means you get more compact particles.
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