Disruption of Model Membranes by PAMAM Dendrimers and Quantitative Nanoscale Analysis of Type I Collagen.

Abstract

erionic DPPC in the gel phase. Generation 5 and 7 Poly(amidoamine) dendrimers preferentially disrupt the fluid layer. For the first time, dendrimer can be observed collecting on top of the lipid preceding removal. The location of the dendrimer is verified by phase imaging. Molecular Dynamics simulations also support that dendrimers are on top of the bilayer. These simulations show that the dendrimer deforms more when interacting with a fluid lipid bilayer. This increase in deformation is observed in AFM images through an analysis of the edge profiles of the dendrimer adhered to the surface. Finally, following removal, no dendrimer is adhered to the mica substrate. This observation, coupled with observations of the dendrimer on top of the lipid, supports that disruption is due to lipid encapsulating dendrimer and not a disruption of the interaction of lipid and substrate. Turning to the second part of the thesis, collagen fibrils exhibit a characteristic banding pattern roughly 67 nm in spacing. A 2D Fast Fourier Transform technique has been developed to measure both the spacing and orientation of fibrils within AFM images. Computer simulations and experimental data show at least 9 D-Period repeats must be measured to minimize the potential for error. The resolution limit of the 2D-FFT technique is 0.8 nm. Large populations of fibrils from Ovine samples, exhibit a distribution of fibril spacing—significantly larger than the resolution limit—around a central mean. A distribution of spacings also exists in electron microscope images. X-Ray scattering data also shows similar sized distributions in spacing. Finally, statistical comparisons show a significant change in the distribution caused by estrogen depletion in Ovine samples.