Pure silver and gold nanoclusters have been studied widely in recent years for their size- and shape-dependent catalytic and optical properties. With straightforward synthesis, light scattering ability and potential for high stability, gold nanoparticles also lend themselves to molecular biology. Alternatively, the implementation of silver nanoparticles in consumer products due to their anti-bacterial activity has stirred investigation into their effects on the environment and on human health. Bimetallic gold-silver nanoparticles are currently being investigated for their feasibility as next-generation catalysts and sensors, whose properties are subject to fine tuning of the gold to silver ratio. Due to the rise in applications for these nanoparticles and potential increase in human exposure, it is critical to have an atomic-level understanding of the reactivity of nanoparticles in biological milieu, especially their reaction mechanism with bio-molecules. While the interaction of noble metal clusters with DNA has been studied extensively, to date, the reactivity studies of these metal nanoparticles with neurotransmitters have not been reported. In this presentation, we discuss results of our recent DFT-based computational study on the reactivity of size-selected Aun, Agn, AuxAgy (n = 8, 10; x + y = n) nanoclusters with dopamine. We address the effects of size, shape, and alloying on the reactivity, stability, and optical properties of these clusters. We also address the solvent effects on the interactions between these nanoclusters and dopamine.