Facile synthesis of gold–silver alloy nanoparticles for application in metal enhanced bioluminescence†
In the present study we explored metal enhanced bioluminescence in luciferase enzymes for the first time. For this purpose a simple and reproducible one pot synthesis of gold–silver alloy nanoparticles was developed. By changing the molar ratio of tri-sodium citrate and silver nitrate we could synthesize spherical Au–Ag colloids of sizes ranging from 10 to 50 nm with a wide range of localized surface plasmon resonance (LSPR) peaks (450–550 nm). The optical tunability of the Au–Ag colloids enabled their effective use in enhancement of bioluminescence in a luminescent bacterium Photobacterium leiognathi and in luciferase enzyme systems from fireflies and bacteria. Enhancement of bioluminescence was 250% for bacterial cells, 95% for bacterial luciferase and 52% for firefly luciferase enzyme. The enhancement may be a result of energy transfer or plasmon induced enhancement. Such an increase can lead to higher sensitivity in detection of bioluminescent signals with potential applications in bio-analysis.