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Salt-induced disintegration of lysozyme-containing polyelectrolyte complex micelles
Saskia Lindhoud1, Lenny Voorhaar, Renko de Vries
1Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, 6703 HB Wageningen, The Netherlands. saskia.lindhoud@wur.nl
Langmuir : the ACS Journal of Surfaces and Colloids
|August 21, 2009
Summary
The study reveals how salt concentration affects polyelectrolyte complex micelles containing lysozyme. Micelle size and structure change with increasing salt, indicating a shift from electrostatic interactions to other forces driving complex formation.
Area of Science:
- Materials Science
- Polymer Chemistry
- Biophysics
Background:
- Polyelectrolyte complex micelles are self-assembled structures formed by oppositely charged polymers.
- Lysozyme, a protein, can be incorporated into these micelles, influencing their properties.
- Understanding the stability and behavior of these complex micelles under varying conditions is crucial for applications in drug delivery and nanotechnology.
Purpose of the Study:
- To investigate the salt-induced structural changes and disintegration of lysozyme-filled polyelectrolyte complex micelles.
- To determine the critical salt concentrations at which structural rearrangements and complex dissociation occur.
- To elucidate the role of electrostatic interactions versus other forces in maintaining micellar integrity.
Main Methods:
- Dynamic Light Scattering (DLS) to measure hydrodynamic radius (Rh) and monitor changes in micellar size.
- Small-Angle Neutron Scattering (SANS) to probe the internal structure and core radius (Rcore) of the micelles.
- Systematic variation of sodium chloride (NaCl) concentration to induce and observe salt effects.
Main Results:
- Hydrodynamic radius (Rh) and core radius (Rcore) decrease from 0 to 0.2 M NaCl, indicating micellar rearrangement.
- Between 0.2 and 0.4 M NaCl, a different structure forms, evidenced by constant light-scattering intensity and a non-monotonic change in Rh.
- SANS data at 0.3 M NaCl suggest the absence of lysozyme within the core, indicating complex disintegration and formation of a new structure composed of polymers only.
Conclusions:
- The study demonstrates a complex salt-dependent behavior of lysozyme-filled polyelectrolyte complex micelles.
- Lysozyme dissociates from the complex at moderate salt concentrations (around 0.12 M NaCl).
- The driving force for micelle formation shifts from electrostatic interactions to other forces at higher salt concentrations, leading to the formation of polymer-only structures.
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