Thesis subject

MSc - Nanoparticulate species in biogels

Due to the increasing production of nanomaterials worldwide, their release into the environment and impact on ecological and human health are issues of great concern. Their high specific surface area, higher reactivity, and other nanoscale features affect the transport, persistence, bioavailability, and toxicity of nanoparticles.

Because of the physicochemical interaction with other components of the natural waters such as metal ions, organic pollutants and microorganisms there is a large variety of nanoparticulate species. Here, our focus will be on the interaction of nanoparticulate metal complex species in alginate gels as model biogel systems. Biogels are uniquitous in environmental compartments. They appear in forms such as biofilms and cell walls of organisms. Nanoparticulate metal species inside the biogel may differ greatly from those in the surrounding medium. Detailed physicochemical knowledge of distributions of nanoparticulate species in the biogel is a prerequisite in understanding their bioavailability and bioaccumulation.

The goal of this project is to obtain physicochemical speciation data for charged biogel phases, i.e. information on the various physicochemical forms in which they occur. The gels should be representative for the types of environments that typically surround microorganisms (i.e., cell walls, mucosal layers). Gel permeation and interaction of silica nanoparticle-metal complexes with the model biogel will be analysed, using dynamic microelectrodic sensors and other techniques for in-situ speciation analysis.

The study of the physicochemistry of nanoparticulate metal complexes at biointerfaces represents an important part of quantifying, modelling and assessing the risks related to nanoparticle/metal contamination of our environment. The laboratory of Physical Chemistry and Colloid Science has been studying metal speciation dynamics in different media in the past years. Chemodynamic principles for metal ions themselves and in nanoparticulate ligand dispersions have recently been described and discussed [1-3]. To elaborate on this, the present project will investigate the behaviour of nanoparticulate metal complexes in an alginate biogel.

Supervisor: Katarzyna Zielinska

Experimental techniques:

Theoretical framework:

  1. Dynamic speciation in homogeneous solutions.
  2. Dynamic speciation in colloidal ligand systems.
  3. Gel stability and swelling behaviour.

Experimental techniques:

  1. Preparation of model biogels.
  2. Immobilization of nanoparticle-metal ion complex in gel network
  3. Potentiometric titration.
  4. Voltammetry.
  5. Inductively coupled plasma-atomic emission spectrometry (ICP-AES).
  6. Dynamic light scattering (DLS).

References:

1. T.A. Davis, E.J.J. Kalis, J.P. Pinheiro, R.M. Town, H.P. van Leeuwen, Cd(II) Speciation in alginate gels. Environ. Sci. Technol. 42 (2008) 7242-7247.
2. J.P. Pinheiro, R.F. Domingos, M. Minor, H.P. van Leeuwen, Metal speciation dynamics in colloidal ligand dispersions. Part Lability features of steady-state systems, J. Electroanal. Chem. 596 (2006) 57-64

3. J.F.L. Duval, J.P. Pinheiro, H.P. van Leeuwen, Metal speciation dynamics in monodisperse soft colloidal ligand suspensions.J. Phys. Chem. A 112 (2008) 7137-7151.