Multifunctional polydopamine-based nanoparticles: Synthesis, physico-chemical properties and applications for bimodal photothermal/photodynamic therapy of cancer

Polydopamine (PDA) is a mussel-inspired and a melanin-mimicking material that has attracted considerable attention during the recent years. This polymer displays diverse promising properties, like its simple preparation procedures, easy functionalization, free radicals scavenging activity, outstanding photothermal and photoacoustic performance, and its great biocompatibility and biodegradability. A remarkable feature of PDA is its ability to form colloidal nanosized particles or nanoscaled coatings, allowing the preparation of various nanoparticulate structures. The first studies into PDA mainly explored the polymerization mechanisms of this material and the development of controlled preparation protocols. Later works focused on the investigation of these nanomaterials for the design and development of multifunctional platforms and their implementation in multiple biomedical fields, particularly in cancer treatment and bio-imaging. The purpose of this review is to (a) give a detailed overview about the synthesis methods of PDA and the formation mechanisms proposed so far in the literature, (b) outline the remarkable physico-chemical and functional properties of PDA nanomaterials, and (c) summarize the application of PDA-derived nanosystems in cancer theranostics and particularly in drug delivery and light-mediated cancer therapy with a special emphasis on the different strategies that can be used for the design of smart nanosystems with bimodal photothermal/photodynamic properties. Finally, a comparison of physicochemical properties and biomedical applications between PDA and other catecholamine derivatives is made. © 2021 IOP Publishing Ltd.