On the kinetics of chitosan/tripolyphosphate micro- and nanogel aggregation and their effects on particle polydispersity.
Submicron chitosan/tripolyphosphate (TPP) particles are widely investigated as nanocarriers for drugs, genes and vaccines. One of the key particle properties that requires control is their size distribution, which depends on the extent of chitosan/TPP primary nanoparticle aggregation into higher-order submicron colloids. To provide a better understanding of this higher-order aggregation process, this study analyzes the factors that control chitosan/TPP particle aggregation kinetics in the presence of free TPP (such as present during particle formation). The aggregation rates exhibit a sharp power-law decrease with the monovalent salt concentration and a power-law increase with the free TPP concentration. Moreover, the aggregation rates increase with the pH and with the chitosan degree of deacetylation (DD). These variations in aggregation rates reflect the effects of monovalent salt, TPP concentration, pH and chitosan DD on particle bridging by the surface-bound TPP. Furthermore, these aggregation rates are much faster than those predicted based on Derjaguin and Landau, Verwey and Overbeek (DLVO) interaction potentials, which might reflect nonuniformities in particle shape and charge, and/or complications caused by particle softness. Finally, implications of the above aggregation kinetics on the uniformity of chitosan/TPP micro- and nanogel size are analyzed, where we: (1) show how particle polydispersity can be diminished by lowering the chitosan DD; and (2) explain the opposing results on how chitosan/TPP particle polydispersity is affected by monovalent salt.
Department of Chemical and Environmental Engineering, University of Toledo, Toledo, OH 43606, United States.
Yan
Y
Huang
Department of Chemical and Environmental Engineering, University of Toledo, Toledo, OH 43606, United States; School of Green Chemistry and Engineering, University of Toledo, Toledo, OH 43606, United States. Electronic address: yakov.lapitsky@utoledo.edu.
Yakov
Y
Lapitsky
D000107:Acetylation; D048271:Chitosan / Q000737:chemistry*; D005427:Flocculation; D005782:Gels; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D053758:Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D011122:Polyphosphates / Q000737:chemistry*; D012965:Sodium Chloride / Q000737:chemistry*; D055672:Static Electricity
D005782:Gels; D011122:Polyphosphates; D012965:Sodium Chloride; D048271:Chitosan; C005692:triphosphoric acid
Aggregation; Chitosan; Ionic crosslinking; Microgels; Nanoparticles; Polydispersity; Tripolyphosphate