|Johannes Sitterberg, Jens Schäfer, and Udo Bakowsky
Department of Pharmaceutical Technology and Biopharmaceutics, University of Marburg, Ketzerbach 63, 35037 Marburg, Germany
Nanoscale drug carriers have shown to be promising tools for delivery of active pharmaceutical substances into tissues and cells. Due to their biodegradability, nanoparticles made of polyesters like PLGA are interesting systems for systemic delivery. Unfortunatelly, they show poor immune tolerance and unspecific adhesion to organs or tissues. Liposomes, on the other hand, which show low toxicity and low unspecific interactions, cannot be stored for long times and show only a moderate stability, esspecially under shear stress conditions.
We reasoned that a combination of these two nanoscale carrier systems should have advantages over each of the systems alone. Therefore, we developed lipid coated nanoparticles, synergizing advantages of both the carrier systems. In the present study, we tested the lipid coating for its adhesion properties. We investigated the adhesion of uncoated and lipid coated nanoparticles to lipid model membranes and living cells using atomic force spectroscopy. Nanoparticles were immobilized at the apex of commercial AFM-tips. The adhesion of attached nanoparticles to surfaces was determined by approaching the nanoparticle to the surface and allowing it to adhere. The force needed to dissociate the particle from the surface (either cell surface or model membrane) was analysed. These data were correlated with classical cell adhesion measurements. A549 cells were incubated with fluorescently labelled nanoparticles and washed several times. The amount of adhered nanoparticles was determined using fluorescence spectroscopy.