Dendrimer as a multifunctional capping agent for metal nanoparticles for use in bioimaging, drug delivery and sensor applications

Advances in nanoparticle research, particularly in the domain of surface-engineered, function-oriented nanoparticles, have had a profound effect in many areas of scientific research and aided in bringing unprecedented developments forward, particularly in the biomedical field. Surface modifiers/capping agents have a direct bearing on the major properties of metal nanoparticles (MNPs), ranging from their physico-chemical properties to their stability and functional applications. Among the different classes of capping agents, dendrimers have gained traction as effective multifunctional capping agents for MNPs due to their unique structural qualities, dendritic effect and polydentate nature. Dendrimer-coated metal nanoparticles (DC-MNPs) are typically produced by both (i) a one-pot strategy, where metal ions are reduced in the presence of dendrimer molecules and (ii) a multi-pot strategy, where a sequence of reactions involving the reduction of metal ions, activation, conjugation and purification steps are involved. These DC-MNPs have shown remarkable ability to stabilize MNPs by means of electrostatic interactions, coordination chemistry or covalent attachment, due to them entailing a large number of sites at which further molecular moieties can be conjugated. This review article is an attempt to consolidate the on-going work, particularly over the last five years, in the field of the synthesis of dendrimer-coated MNPs and their potential applications in bioimaging, drug delivery and biochemical sensors.