Plasmonic nanotransducers, methods of preparing plasmonic nanotransducers, and methods for label-free detection of target molecules are disclosed. The plasmonic nanotransducers include hollow nanostructure cores and artificial antibodies. The plasmonic nanotransducers are exposed to a biological sample that can contain the specific target molecules. The plasmonic nanotransducers can be analyzed with surface enhanced Raman scattering techniques and/or localized surface plasmon resonance techniques to quantify the amount of the target molecule in the sample.