This week, I was lucky enough to be invited to hear an impromptu talk from Joel A Pedersen of the Environmental Chemistry and Technology Program at the University of Wisconsin, Madison. Dr Pedersen was in the UK to attend ‘Prion 2007’, and dropped by the IOM to give us a summary of his work on transformation of engineered nanoparticles in the environment, something I knew little about before his visit.
To start, we were given an introduction to the complex interfacial interactions to which nanoparticles are subject, including the Extended Derjaguin Landau Verney Overbeek (XDLVO) theory and interactions such as the Electrostatic Double Layer, Lifshitz van der Waals and Polar Interactions. In addition, Dr Pedersen gave an eloquent description of the confounding influence steric reactions, surface roughness and functionalization could bring, the effect each of these has on Nanoparticle behaviour, and the inherent difficulties these multiple simultaneous interactions present for making accurate quantitative predictions of nanoparticle behaviour in the environment.
He then moved on to focus on the actual lifecycle of nanoparticles, and changes in their surface that may occur during this lifecycle. Dr Pedersen described acquisition and biomodification of NP coatings, and gave laboratory-based and real-life examples of both. He then discussed chemical models for microbially mediated NP transformation, including oxidation, reduction and ligand –assisted dissolution of nanoparticles – the area his group are currently investigating. His laboratory had carried out an elegant experiment using an in vitro biomimetic oxidative assay which made use of lignolytic funghi. The group had applied this assay to polyethylene glycol (PEG) functionalised Quantum Dots, colloidal NPs that have undergone development as organic dyes and fluorescent markers in living cells amongst other applications. They found that that Quantum Dot transformation is possible within oxidative environments, and that Cadmium was released from within the core of the QDs they used.
Despite the huge complexity of the concepts Dr Pedersen was conveying (a lot to take on board if you’re as new to the topic as I am!), his talk and research was incredibly interesting. In addition, the results he has collected so far clearly have possible wide-ranging implications for the use of such Quantum Dots in living organisms given that substances which make up the core of QD’s are often intrinsically toxic in nature. It also reminded me of the enormity of the puzzle that scientists investigating nanotechnology are facing, and what a tiny proportion of this we have tackled so far.