Nanomedicine is the biomedical application of nanoscale materials for diagnosis and therapy of disease. Recent advances in nanotechnology and biotechnology have contributed to the development of multifunctional nanoparticles as representative nanomedicine. They were initially developed to enable the target-specific delivery of imaging or therapeutic agents for biomedical applications. Due to their unique features including multifunctionality, large surface area, structural diversity, and long circulation time in blood compared to small molecules, nanoparticles have emerged as attractive preferences for optimized therapy through personalized medicine. Multimodal imaging and theragnosis are the cutting-edge technologies where the advantages of nanoparticles are maximized. Because each imaging modality has its pros and cons, the integration of several imaging agents with different properties into multifunctional nanoparticles allows precise and fast diagnosis of disease through synergetic multimodal imaging. Moreover, nanoparticles are not only used for molecular imaging but also applied to deliver therapeutic agents to the disease site in order to accomplish the simultaneous imaging and therapy called theragnosis. This tutorial review will highlight the recent advances in the development of multifunctional nanoparticles and their biomedical applications to multimodal imaging and theragnosis as nanomedicine.

Macrophages (Mϕs) critically contribute to wound healing by coordinating inflammatory, proliferative, and angiogenic processes. A proper switch from proinflammatory M1 to anti‐inflammatory M2 dominant Mϕs accelerates the wound healing processes leading to favorable wound‐care outcomes. Herein, an exosome‐guided cell reprogramming technique is proposed to directly convert M1 to M2 Mϕs for effective wound management. The M2 Mϕ‐derived exosomes (M2‐Exo) induce a complete conversion of M1 to M2 Mϕs in vitro. The reprogrammed M2 Mϕs turn Arginase (M2‐marker) and iNOS (M1‐marker) on and off, respectively, and exhibit distinct phenotypic and functional features of M2 Mϕs. M2‐Exo has not only Mϕ reprogramming factors but also various cytokines and growth factors promoting wound repair. After subcutaneous administration of M2‐Exo into the wound edge, the local populations of M1 and M2 Mϕs are markedly decreased and increased, respectively, showing a successful exosome‐guided switch to M2 Mϕ polarization. The direct conversion of M1 to M2 Mϕs at the wound site accelerates wound healing by enhancing angiogenesis, re‐epithelialization, and collagen deposition. The Mϕ phenotype switching induced by exosomes possessing the excellent cell reprogramming capability and innate biocompatibility can be a promising therapeutic approach for various inflammation‐associated disorders by regulating the balance between pro‐ versus anti‐inflammatory Mϕs.