Ag2S quantum dot theragnostics

Abstract

Silver sulfide quantum dots (Ag₂S QDs) as a theragnostic agent have received much attention because they provide excellent optical and chemical properties to facilitate diagnosis and therapy simultaneously. Ag₂S QDs possess brightness and photostability suitable for intense and stable bioimaging. It has been verified via in vitro and in vivo studies that Ag₂S QDs do not cause serious toxicity, unlike the first generation of widely used heavy metal-based (cadmium or lead) QDs. In particular, Ag₂S QDs emit in the near infrared-II region (NIR-II window) that enables deep tissue penetration and imaging. Furthermore, various chemotherapeutic agents and targeting moieties can be efficiently conjugated to the surface of Ag₂S QDs due to advanced technologies in the relevant surface chemistry using covalent bonding, high affinity, and electrostatic interaction. In addition, Ag₂S QDs themselves exhibit an anticancer activity based on the photothermal effect. Consequently, Ag₂S QDs can function as both a therapeutic agent and an imaging agent in imaging-based diagnosis concurrently, which led to the creation of Ag₂S theragnostic nanomaterials. In this review, the synthetic methods, physicochemical properties, bioconjugations, and bioapplications of Ag₂S QD theragnostic nanomaterials are discussed in detail.