Nanoparticles at Interfaces

Nowadays the interest in the research of Nanoparticles–polymer composite materials is continuously growing due to their multiple potential applications especially in the biomedical field: As carriers for drugs across biological barriers, as imaging agents in biological systems, as probes to investigate interfacial phenomena and so on.
In this area, our study is dedicated to two different Nanoparticles–polymer systems: Fe3O4-copolymer-NPs (cooperation with Dr. Dayang Wang, Interface Department of our institute) and Chitosan-coated PLGA-NPs (Prof. M. Schneider, Biopharmaceutics and Pharmaceutical Technology, Saarland University, Saarbrücken, Germany).
The first system, the magnetic Fe3O4 nanoparticles, capped with biocompatible copolymers (MEO2MA and OEGMA), were designed and synthesised in our institute. Due to the fact that the magnetic-core is functionalised with stimuli-responsive polymers, these NPs exhibit an extraordinary surface wettability. Indeed, the NPs form highly stable colloidal dispersions in both aqueous and organic media and can be transferred from one phase to another under certain conditions. The ability of crossing interfaces, hence crossing possibly biological barriers, highlighted by their multifunctionality (magnetic properties, fluorescence) make them very promising candidates for applications in biomedicine. Therefore, our study is focused on a better understanding of the adsorption properties, the stability and the characterization of the NPs at the water/air and water/oil interfaces. In this respect, the dynamic and equilibrium interfacial tensions and the dilatational viscoelasticity of the adsorption layer, the aging and the aggregation behavior, the thickness and the roughness, the stability and the structure of the NPs layer at the interfaces are investigated. Due to the envisaged biological applications, the interaction of the Fe3O4-copolymer-NPs with cellular membrane models it is a very important aspect of our study.
The cationically modified poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles have recently been proved as tunable and efficient carriers for antisense oligonucleotides (2′-O-methyl-RNA) to lung cancer cells. The binding experiments showed that the addition of oligonucleotides to the NPs caused a reduction in the surface charge, indicating electrostatic binding of the negatively charged oligonucleotides to the positively charged NPs. The aim of our collaboration is to analyze and elucidate the biophysical interactions of these cationically modified NPs with negatively charged model membranes (in different phase state). These experiments will allow us to establish a correlation between the binding interactions, the effect on the phospholipid monolayer and the cellular uptake of the NPs.

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