Localized surface plasmon resonance (LSPR) of polyelectrolyte-functionalized gold-nanoparticles for bio-sensing

Gold-nanoparticles can be used as a robust tool for bio-sensing based on localized surface plasmon resonance (LSPR). Both local refractive index change and self-assembly of the nanoparticles can lead to some spectral shifts of the LSPR extinction peak. Using different mechanisms of LSPR peak shifts, two types of transducers are set up to detect the streptavidin concentration through the specific recognition with biotin moleculars, which are conjugated to gold-nanoparticles. One is based on the self-assembly of gold-nanoparticles in solution, and the other is based on the increase of the local refractive index near the surface of the immobilized gold-nanoparticles after streptavidin–biotin binding. The sensitivity and efficiency of the two transducers are compared. Gold-nanoparticles are functionalized with polyelectrolyte, which can improve significantly the stability of the nanoparticles and reduce the unspecific binding of streptavidin. Polyelectrolyte functionalization also provides a simple way to conjugate gold-nanoparticles with charged molecules such as biotin and BSA–biotin.