Gold nanoparticles (size 10 nm) were designed to store and release nitric oxide (NO), by functionalizing their surfaces with functional polymers modified with NO-donor molecules. Firstly, block copolymer chains consisting of poly(oligoethylene glycol methyl ether methacrylate)-b-poly(vinyl benzyl chloride) (P(OEGMA)-b-PVBC)) were prepared using RAFT polymerization. The chloro-functional groups were then reacted with hexylamine, to introduce secondary amine groups to the copolymer chains. The block copolymers were then grafted onto the surface of gold nanoparticles, exploiting the end-group affinity for gold-attaining grafting densities of 0.6 chain per nm2. The secondary amine functional groups were then converted to N-diazeniumdiolate NO donor molecules via exposure to NO gas at high pressure (5 atm). The NO-bearing, gold nanoparticles were characterized using a range of techniques, including transmission electron microscopy, dynamic light scattering (DLS), thermal gravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The nanoparticles displayed slow release of the nitric oxide in biological media. Proof of potential utility was then demonstrated in two different application areas: Pseudomonas aeruginosa biofilm dispersal and cancer cell cytotoxicity.