The Interaction of Targeted and Non-Targeted Nanoparticles with Cells and Model Membranes.

Abstract

The first component of the thesis examines the binding of a multivalent, folic acid (FA) receptor targeted, generation 5 (G5) PAMAM dendrimer using force pulling spectroscopy. This targeted nanoparticle, when conjugated to the therapeutic methotrexate and then acetylated to form a neutral complex, has been shown to be effective at reducing FA-receptor expressing KB cell tumors. Surface plasmon resonance (SPR) showed a 100,000-fold decrease in the dissociation rate of the G5-FAn from a model FA receptor surface, folate binding protein (FBP), as the number of FAs (n) increased from 1-12. Force pulling spectroscopy was then used to compare the force required to rupture the interaction between the FBP and a single G5-FAn taken from a solution of G5-FAn where n = 0, 4.7, 2.7, and 7.2. A difference in rupture force was measured but due to the heterogeneity of the number of FAs per G5-FAn within a given solution, it was not possible to assign the measured forces to a specific number of FA-FBP interactions.

The second component of this thesis examines the interaction of a variety of non-targeted, charged nanoparticles with cells and model membranes. Five polycationic polymers (G5 and G7 PAMAM dendrimer, branched polyethylenimine (PEI), poly-L-lysine (PLL) and diethylaminoethyl-dextran (DEAE-DEX)) were shown to induce nanoscale hole formation in cells as measured by enzyme and dye diffusion assays, as well as in dimyristoylphosphatidylcholine (DMPC) supported lipid bilayers (SLB) as measured by atomic force microscopy (AFM). In contrast, neutral polymers polyethylene glycol and polyvinyl alcohol did not induce nanoscale hole formation in cells or DMPC SLBs. This suggests that a possible mechanism for polycationic polymer internalization and/or nanoparticle-induced cytotoxicity of cells is through nanoscale hole formation. The interaction between SLBs and a variety of other charged nanoparticles (MSI-78, Au-NH2, G3-NH2 PAMAM dendron, and silica-NH2 were also investigated using the AFM-SLB assay. The general trend taken from the AFM-SLB studies is that surface area of the polycationic nanoparticles is the largest contributing factor to membrane disruption. In addition, micelles of charged detergents cetyl trimethylammonium bromide bromide (CTAB) and sodium dodecyl sulfate (SDS) were also shown to induce hole formation in SLBs.