Mechanistic study of the nucleation and conformational changes of polyamines in presence of phosphate ions

Patrizia Andreozzi, Caterina Ricci, Joaquin Emiliano Martinez Porcel, Paolo Moretti, Desirè Di Silvio, Heinz Amenitsch, Maria Grazia Ortore*, Sergio E. Moya

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Polyamine Phosphate Nanoparticles (PANs) have great potential for the delivery of large therapeutics, such as plasmids and/or siRNAs. The formation of PANs by complexation of Poly(allylamine hydrochloride) (PAH) and phosphate ions from Phosphate Buffer (PB) was studied here, and how it is affected by the presence of phosphate ions from PB and ionic strength. From Transmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS) the critical PB concentration for PANs formation was determined. Below this critical point, Small Angle X-ray Scattering (SAXS) studies revealed that small PAH-phosphate aggregates coexist with not complexed or weakly complexed polymer chains in solution and that the presence of the phosphate ions increases the Kuhn length of the polymer chains until that only spherical aggregates are present in solution. TEM, DLS and SAXS showed the increase of PANs size with ionic strength up to 250 mM NaCl. At higher NaCl concentrations, PANs disassemble into smaller aggregates. Isothermal Titration Calorimetry (ITC) showed that PAN formation is an exothermic process and the association of phosphates below the critical PB concentration is entropically controlled.

Original languageEnglish
Pages (from-to)335-342
Number of pages8
JournalJournal of Colloid and Interface Science
Publication statusPublished - 1 May 2019


  • DLS
  • Nanoparticles nucleation
  • Polyamine phosphate interactions
  • SAXS
  • Self-assembled nanoparticles

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Surfaces, Coatings and Films
  • Colloid and Surface Chemistry


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