Surface-enhanced Raman Scattering (SERS) is a promising technique for biosensing due to its high sensitivity at low concentration of analytes of interest. Via this technique, Raman signals of detected molecules are significantly enhanced on the surface of metal or metallic nanostructures. Metallic nanoparticles are widely used for biosensors based on SERS due to their optical and physical properties, generating high enhancement factor. The enhancement factor of SERS is not only dependent on the materials but also dependent on the size, shape and architecture of the substrates. Biosilica diatoms make good candidates that are attractive for plasmonic composite since they show natural nanostructures with a great diversity, which lead to their unique mechanical and optical properties. Therefore, in this work, diatoms and metallic nanoparticles are combined as a novel biocomposite material for potential applications as biosensors. Silver nanoparticles (AgNPs) were self-assembled with diatoms and then deposited on adhesive office tapes. With the prepared substrate, bacteria and proteins at low concentration were measured with Raman spectroscopy. The results indicated although the substrate based the nanocomposite consisting of AgNPs, diatoms and office tapes is particularly suitable for biological particles at nano- to micro-meter scale, showing better performance on identifying different types or strains of bacteria from each other compared to protein identification due to their larger sizes.