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.

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New controlled drug-delivery systems are being explored to overcome the disadvantages of conventional dosage forms. For example, stimulated drug-delivery has been used to overcome the tolerance problems that occur with a constant delivery rate, to mimic the physiological pattern of hormonal concentration and to supply drugs on demand. Stimuli-sensitive polymers, which are potentially useful for pulsed drug delivery, experience changes in either their structure or their chemical properties in response to changes in environmental conditions. Environmental stimuli include temperature, pH, light (ultraviolet or visible), electric field or certain chemicals. Volume changes of stimuli-sensitive gel networks are particularly responsive to external stimuli, but swelling is slow to occur. As well as being useful in the controlled release of drugs, such systems also provide insight into intermolecular interactions. Here we report on a novel polymeric system, which rapidly changes from a solid state to solution in response to small electric currents, by disintegration of the solid polymer complex into two water-soluble polymers. We show that the modulated release of insulin, and by extension other macromolecules, can be achieved with this polymeric system.

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Advances in nanotechnology have contributed to the development of novel nanoparticles that enable the tumor‐specific delivery of imaging probes and therapeutic agents in cancer imaging and therapy. Nanobiotechnology combines nanotechnology with molecular imaging, which has led to the generation of new multifunctional nanoparticles for cancer imaging and therapy. Multifunctional nanoparticles hold great promise for the future of cancer treatment because they can detect the early onset of cancer in each individual patient and deliver suitable therapeutic agents to enhance therapeutic efficacy. The combination of tumor‐targeted imaging and therapy in an all‐in‐one system provides a useful multimodal approach in the battle against cancer. Novel multifunctional nanoparticles thus offer a new avenue in the application of personalized medicine in the near future. Herein, new trends and the significance of novel multifunctional nanoparticles in cancer imaging and therapy are reviewed.

Tumor targetability and site-specific drug release of therapeutic nanoparticles are key factors for effective cancer therapy. In this study, poly(ethylene glycol) (PEG)-conjugated hyaluronic acid nanoparticles (P-HA-NPs) were investigated as carriers for anticancer drugs including doxorubicin and camptothecin (CPT). P-HA-NPs were internalized into cancer cells (SCC7 and MDA-MB-231) via receptor-mediated endocytosis, but were rarely taken up by normal fibroblasts (NIH-3T3). During in vitro drug release tests, P-HA-NPs rapidly released drugs when incubated with cancer cells, extracts of tumor tissues, or the enzyme Hyal-1, which is abundant in the intracellular compartments of cancer cells. CPT-loaded P-HA-NPs (CPT-P-HA-NPs) showed dose-dependent cytotoxicity to cancer cells (MDA-MB-231, SCC7, and HCT 116) and significantly lower cytotoxicity against normal fibroblasts (NIH-3T3) than free CPT. Unexpectedly, high concentrations of CPT-P-HA-NPs demonstrated greater cytotoxicity to cancer cells than free CPT. An in vivo biodistribution study indicated that P-HA-NPs selectively accumulated into tumor sites after systemic administration into tumor-bearing mice, primarily due to prolonged circulation in the blood and binding to a receptor (CD44) that was overexpressed on the cancer cells. In addition, when CPT-P-HA-NPs were systemically administrated into tumor-bearing mice, we saw no significant increases in tumor size for at least 35 days, implying high antitumor activity. Overall, P-HA-NPs showed promising potential as a drug carrier for cancer therapy.

Although sonodynamic therapy (SDT) has emerged as a potential alternative to conventional photodynamic therapy, the low quantum yield of the sonosensitizer such as TiO nanoparticles (NPs) is still a major concern. Here, we have developed hydrophilized Au-TiO nanocomposites (HAu-TiO NCs) as sonosensitizers for improved SDT. The physicochemical properties of HAu-TiO NCs were thoroughly studied and compared with their counterparts without gold deposition. Upon exposure of HAu-TiO NCs to ultrasound, a large quantity of reactive oxygen species (ROS) were generated, leading to complete suppression of tumor growth after their systemic administration in vivo. Overall, it was evident that the composites of gold with TiO NPs significantly augmented the levels of ROS generation, implying their potential as SDT agents for cancer therapy.