Polymers and inorganic nanoparticles: A winning combination towards assembled nanostructures for cancer imaging and therapy

Inorganic nanoparticles show unique physical properties (e.g., optical, electronic, magnetic and catalytical properties), and highly tunable appearance characteristics (e.g., size, shape, morphology, and surface). Unlike inorganic nanomaterials, organic polymers generally have good biocompatibility, stability and processability, as well as highly tailorable degradability and responsiveness to external stimuli (e.g., light, heat, pH, acoustic wave and biological signals). Nanosized assemblies derived from polymers and inorganic nanoparticles naturally combine the complementary strengths of both parties to exhibit synergistically improved properties that are often not readily accessible from their single constituent parts. These properties have enabled the emerging applications of polymer-inorganic nanoparticle assemblies (PINAs) in biology and medicine, especially in cancer imaging and therapy. This review summarizes recent advances in the development of nanosized PINAs with synergistically enhanced properties from polymers and inorganic nanoparticles for cancer imaging and therapy. We start with an introduction of the field in Section Introduction and a brief discussion of physicochemically relevant structural parameters of PINAs in Section Structural parameters of PINAs. We then elaborate on reviewing the design and implementation of PINAs for cancer imaging in Section Cancer imaging. Several major imaging modalities we discussed include emission-based imaging, photothermal/photoacoustic imaging, magnetic resonance imaging, computed tomography imaging and multi-modal imaging. Section Cancer therapy is focused on the design and use of PINAs for various therapeutic strategies of cancers, such as hypothermia, photodynamic therapy and controlled drug delivery. The review is ended with a discussion of our perspectives on future research in the field.