Physical Properties and Stability of Soft Gelled Chitosan‐Based Nanoparticles

We addressed the role of the degree of acetylation (DA) and of M w of chitosan (CS) on the physical characteristics and stability of soft nanoparticles obtained through either ionic cross‐linking with sodium tripolyphosphate (TPP), or reverse emulsion/gelation. Each of these methods affords nanoparticles (NPs) or nanogels (NGs), respectively. The size of CS–TPP NPs comprising CS of high M w (≈123–266 kDa) increases with DA (≈1.6%–56%), while it do not change for CS of low M w (≈11–13 kDa); the zeta potential (ζ) decreases with DA regardless of M w (ζ ≈+34.6 ± 2.6 to ≈+25.2 + 0.6 mV) and the NPs appear as spheres in transmission electron microscopy. Stability in various cell culture media (pH 7.4 at 37 °C) is greater for NPs made with CS of DA ≥ 27%. In turn, NGs exhibit larger sizes (520 ± 32 to 682 ± 27 nm) than do CS–TPP NPs, and can only be formed with CS of DA < 30%. The average diameter size for these NGs shows a monotonic increase with CS's M w . The physical properties and stability of these systems in biological media depend mostly on the DA of CS and its influence on the balance between hydrophilic/hydrophobic interactions.