| This dissertation describes the development and validation of a technique that uses angle dependent light scattering (ADLS), fractal dimension analysis and gold (Au) nanoparticles towards the detection and characterization of nucleic acids and proteins. Two separate ADLS apparatuses were developed, one that uses a detector mounted on a rotation stage and the other uses a stationary ellipsoidal mirror and a CCD detector. We extracted the fractal dimension (Df) from the ADLS signal from Au-biopolymer aggregates. The nucleic acid measurements showed that the scattering signal and Df of Au-DNA aggregates were sensitive to the concentration and length of small oligonucleotides (21 and 30 bases). Two protein systems were studied, one used the biotin-streptavidin couple where biotin was bound to Au nanoparticles, and the other used antibody modified Au nanoparticles where antibody-antigen interactions were detected. The streptavidin-biotin system showed that the Df of Au-streptavidin aggregates is sensitive to the concentration and structure of streptavidin. The scattering signal of the Au-antibody systems was sensitive to the specific interaction between Au-antibody and its target antigen, and the fractal dimension was sensitive to the cross-reactivity between antibodies and antigens of different species. |
