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Please provide up to five keywords (plural, lowercase, separated by commas) Even after more than two decades of intense studies, the research on self-assembly processes involving supramolecular interactions between nanoparticles (NPs) are continuously expanding. Plasmonic NPs have attracted particular attention due to strong optical, electrical, biological, and catalytic effects they are accompanied with. Surface plasmon resonances characteristic of plasmonic NPs and their assemblies enable fine-tuning of these effects with unprecedented dynamic range. In turn, the uniquely high polarizability of plasmonic nanostructures and related optical effects exemplified by surface-enhanced Raman scattering and red-blue color changes gave rise to their application to biosensing. Since supramolecular interactions are ubiquitous in nature, scientists have found a spectrum of biomimetic properties of individual and assembled NPs that can be regulated by the layer of surface ligands coating all NPs. This paradigm has given rise to multiple studies from the design of molecular containers and enzyme-like catalysts to chiroplasmonic assemblies. Computational and theoretical advances in plasmonic effects for geometrically complex structures have made possible the nanoscale engineering of NPs, assemblies, and supramolecular complexes This article is protected by copyright. All rights reserved. 3 with biomolecules. It is anticipated that further studies in this area will be expanded toward chiral catalysis, environmental monitoring, disease diagnosis, and therapy.

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Noninvasive and precise stem cell tracking after transplantation in living subject is very important to monitor both stem cell destinations and their in vivo fate, which is closely related to their therapeutic efficacy. Herein, we developed bicyclo[6.1.0]­nonyne (BCN)-conjugated glycol chitosan nanoparticles (BCN-NPs) as a delivery system of dual-modal stem cell imaging probes. Near-infrared fluorescent (NIRF) dye Cy5.5 was chemically conjugated to the BCN-NPs, and then oleic acid-coated superparamagnetic iron oxide nanoparticles (OA-Fe3O4 NPs) were encapsulated into BCN-NPs, resulting in Cy5.5-labeled and OA-Fe3O4 NP-encapsulated BCN-NPs (BCN-dual-NPs). For bioorthogonal labeling of human adipose-derived mesenchymal stem cells (hMSCs), first, hMSCs were treated with tetra-acetylated N-azidoacetyl-d-mannosamine (Ac4ManNAz) for generating azide (−N3) groups onto their surface via metabolic glycoengineering. Second, azide groups on the cell surface were successfully chemically labeled with BCN-dual-NPs via bioorthogonal click chemistry in vitro. This bioorthogonal labeling of hMSCs could greatly increase the cell labeling efficiency, safety, and imaging sensitivity, compared to only nanoparticle-derived labeling technology. The dual-modal imaging-guided precise tracking of bioorthogonally labeled hMSCs was tested in the photothrombotic stroke mouse model via intraparenchymal injection. Finally, BCN-dual-NPs-labeled hMSCs could be effectively tracked by their migration from the implanted site to the brain stroke lesion using NIRF/T 2-weighted magnetic resonance (MR) dual-modal imaging for 14 days. Our observation would provide a potential application of bioorthogonally labeled stem cell imaging in regenerative medicine by providing safety and high labeling efficiency in vitro and in vivo.