Performance comparison of surface plasmon resonance biosensors based on ultrasmall noble metal nanoparticles templated using bovine serum albumin

Due to their excellent chemical stability, biocompatibility, ease of modification and unique optical properties, ultrasmall noble metal nanoparticles (size 1–2 nm) are finding increasing application in the biomedical sector, in particular as cell markers and bioimaging agents. Herein, the unexplored potential of ultrasmall noble metal nanoparticles as sensitizers in surface plasmon resonance (SPR) biosensors is critically examined. Three types of bovine serum albumin (BSA) coated ultrasmall noble metal nanoparticles were synthesized (BSA-Au NPs, BSA-Au/Ag NPs and BSA-Ag NPs), with the effect of these different types of nanoparticles on the sensitivity of a SPR biosensor for the detection of the enzyme papain explored. Results show that the sensitivity of SPR biosensors containing BSA-Au NPs, BSA-Ag NPs or BSA-Au/Ag NPs BSA were 1.9, 2.6 and 3.6 times higher, respectively, than a control SPR biosensor (BSA only). The remarkable sensitizing properties of the ultrasmall noble metal nanoparticles, especially the BSA-Au/Ag NPs, related to their unique size dependent optical properties.