Synthesis of gold-coated magnetic conglomerate nanoparticles with a fast magnetic response for bio-sensing.

The versatile qualities of gold coated magnetic nanoparticles for both optical and electrochemical detection, as well as the separation of analytes, make them an excellent choice for ultrasensitive biosensing applications. The challenge with such nanoparticles however is that strongly magnetic nanoparticles that reach the magnet rapidly are prone to aggregation, whilst superparamagnetic nanoparticles that are stable against aggregation reach the magnet slowly. Here, we report a conglomerate nanostructure consisting of superparamagnetic nanoparticles coated with gold that provides a rapid magnetic response while exhibiting colloidal stability in solution. The performance of these gold coated magnetic nanoparticles for both bio-separation and biosensing was demonstrated for application in biosensors, dispersible electrodes for detecting microRNA and surface-enhanced Raman scattering. [ABSTRACT FROM AUTHOR]