Colloid and Polymer Science

, Volume 286, Issue 4, pp 365–376 | Cite as

Structural and dynamical characterization of poly-gamma-glutamic acid-based cross-linked nanoparticles

  • Judit Éva Fleischer Radu
  • Levente Novak
  • John F. Hartmann
  • Neda Beheshti
  • Anna-Lena Kjøniksen
  • Bo Nyström
  • János BorbélyEmail author
Original Contribution


This work describes the formation of water-soluble hydrophilic nanoparticles from biosynthetic poly-γ-glutamic acid (PGA). Nanoparticles were formed by cross-linking using 2,2′-(ethylenedioxy) diethylamine in the presence of water-soluble carbodiimide. The structure was determined by nuclear magnetic resonance spectroscopy and the particle size by transmission electron microscopy (TEM), size exclusion chromatography (SEC), and dynamic light-scattering (DLS) measurements. The results from TEM, SEC, and DLS reveal that the particle size depends on the ratio of cross-linking. Particle size values measured by TEM were between 20 and 90 nm. Formation of cross-linked nanoparticles results in a dramatic viscosity drop compared to the viscosity of the corresponding solution of the parent PGA. The viscosity and DLS experiments disclose an intriguing interplay between intrachain and interchain cross-linking of the polymer chains, depending on the cross-linker density and polymer concentration. The SEC measurements show that the retention time of the major portion of particles increase because of the higher cross-linking ratio. At moderate cross-linker concentration, intramolecular cross-linking is the dominant process, whereas at higher cross-linker densities, the interpolymer cross-linking plays an important role. As a result, large clusters are also formed.


Poly-gamma-glutamic acid Nanoparticles Cross-linking DLS Rheology 



This work was supported by RET (Grant of Regional University Knowledge Center) contract numbers (RET-06/423/2004 and RET-06/432/2004) and in part by ElizaNor Polymer LLC, USA. B. N. gratefully acknowledges support from the Norwegian Research Council through a NANOMAT project (158550/431). Authors acknowledge the fermentation facilities of Dr. Levente Karaffa (Department of Genetics, University of Debrecen).


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Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  • Judit Éva Fleischer Radu
    • 1
  • Levente Novak
    • 1
  • John F. Hartmann
    • 2
  • Neda Beheshti
    • 3
  • Anna-Lena Kjøniksen
    • 3
  • Bo Nyström
    • 3
  • János Borbély
    • 1
    • 4
    Email author
  1. 1.Department of Colloid and Environmental ChemistryUniversity of DebrecenDebrecenHungary
  2. 2.ElizaNor Polymer LLCPrincetonUSA
  3. 3.Department of ChemistryUniversity of OsloOsloNorway
  4. 4.BBS NanotechnologyDebrecenHungary

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