Gold Based Nanocomposites: Fabrication Strategies, Properties, And Tumor Theranostic Applications

Gold nanoparticles (AuNPs) have been widely applied in the biomedical field due to their tunable localized surface plasmon resonance (LSPR) properties, versatile surface modifiability, and favorable biocompatibility. With the in-depth study, individual AuNPs cannot meet the requirements for multifunctional biological applications. By combining AuNPs with other inorganic materials, material scientists and chemists have successfully prepared various gold-based nanocomposites (AuNCs), such as Au-metals, Au-semiconductors, Au-magnetic nanocomposites, etc. Furthermore, despite their compositions being the same, products with different topological morphologies (i.e. core@shell, yolk@shell, core-satellite, and Janus) can be fabricated by sophisticated chemistry. Based on their special collective properties and synergetic effects, multifunctional AuNCs have been proposed for tumor theranostic applications; their parts exhibit impressive imaging/therapeutic performances and present tremendous application perspectives for basic research and at a pre-clinical stage. For example, when Au is combined with porous drug carriers, its photothermal properties can promote drug release, which can be useful for developing intelligent drug delivery platforms. In addition, Au and magnetic material hybrids can be used in multimodal imaging and combination therapy, depending on the integration of its optical and magnetic properties. Moreover, when Au is combined with semiconductor material, either LSPR coupling effects or nonradiative energy transfer occurs between them, causing enhanced photothermal or photodynamic therapy. Therefore, in this review, we have highlighted the fabrication approaches of AuNCs including the one-step method, seed-mediated growth method, ex situ assembly method, etc. For the one-step method, we emphasize that Au and other components nucleate and grow concurrently, which is frequently employed for the preparation of Au based alloys. The key to synthesizing AuNCs by seed-mediated growth method is the degree of lattice matching between the different components and the interactions of their heterogeneous interfaces; if the crystal lattices are well-matched, AuNCs can be obtained by direct epitaxial growth. Furthermore, approaches including the introduction of a ligand/surfactant, intermediate layer, and molecular weak interactions into the heterogeneous interfaces can regulate the two components' interaction and fabricate various AuNCs. For the ex situ assembly method, prefabricated AuNPs and other nanoparticles can be assembled into AuCNs by electrostatic attraction, host-guest reaction, bio-recognition, covalent binding, etc. We also summarize the recent achievements of typical AuNCs (i.e. Au-MOF, Au-Fe3O4, and Au-Cu2-xS) in tumor theranostic applications based on their collective properties and/or synergetic effects, respectively. Finally, the main problems and the future developments of this research field are also discussed.