We design, simulate, and experimentally characterize the effects of gold nanoparticle geometry on plasmonic nanosensing performance. Gold nanorods, nanospheres, and nanobipyramids of consistent shape were synthesized using a seed-mediated growth method and characterized using electron microscopy. The plasmonic resonance features and sensitivity of these exact nanoparticles were studied using electromagnetic simulation. Good concordance was found between resonance features, wavelength location, and qualitative plasmonic sensitivity between experiment and simulation. In both simulation and experiment, we found that the synthesized nanobipyramids had the highest plasmonic sensitivity, which carried through from bulk refractive index testing through to synthetic circulating tumor DNA screening. We demonstrated sequence-specific capture of clinically relevant sequences from the KRAS gene using these novel nanoparticle geometries. This paper puts forth a methodology for iterative rational design of plasmonic nanocarriers using electromagnetic simulation and experiment.