Optical Bioimaging and Therapy

In 1665, Britain physicist Robert Hooke first observed the plant cells upon a cork slice. Since then, scientists have never stopped pursuing more advanced technology for optical bioimaging, facilitating progress in biological and medical fields. In the 21st century, optical bioimaging has become a more important analytical tool in the research of life science and created multiple breakthroughs on the field which were awarded the Nobel Prize, such as super-resolution fluorescence microscopy (2014) and the applications of green fluorescent protein for bioimaging (2008). In recent years, along with the flourishment of nanotechnology and nanomaterials, enormous promotion on optical cancer theranostics has been produced. First published in 2013, Advanced Optical Materials is an interdisciplinary journal for top quality research in photonics, plasmonics, metamaterials, and more. Up till now, over 5,000 scientific articles have been reported in Advanced Optical Materials for their great contributions to the development of the fields in optical materials science. To celebrate the 10th anniversary of the Advanced Optical Materials publication and witness the great achievements, this special issue on “Optical Bioimaging and Therapy” includes 20 articles to highlight the recent research progresses in the flourishing field of optical bioimaging and cancer phototherapy. In recent years, the near-infrared (NIR) between 700 and 1,700 nm has been regarded as the “tissue-transparent” window in biomedical field. Till now, various advanced biomaterials have been developed for high-efficiency of NIR light energy conversion for optical bioimaging and therapy, such as down/up-conversion nanomaterials, long-lasting phosphors, semiconductor quantum dots, carbon dots and polymer (carbonized) dots, organic phosphors, etc. Even with such great success, so far, new materials are still being exploited. For example, two kinds of ytterbium dimers were prepared by the Loïc J. Charbonnière group (see article 2202307), which exhibit two-photon cooperative luminescence upconversion. Various material-decorated photosynthetic microorganisms with intrinsic oxygenation and autofluorescence have been reported for a variety of biological applications (Bengang Xing et al., see article 2203038). Apart from the innovation in material, the other key concern is surface modification of materials, which affects their colloidal dispersibility, stability and fluorescence intensity in water and physiological buffers. Hence, Haichun Liu et al. summarized the latest advances on how to adapt lanthanide-doped luminescent nanoparticles (LNPs) to an aqueous medium, ways to utilize the interaction between the LNPs and their medium, and particularly focusing on advances in nanomedicine applications (see article 2200513). Optical bioimaging can provide visualization results for many biological parameters or events, and thus possesses broad application prospects. For instance, Daniel Jaque and co-workers achieved reliable intranuclear thermal measurements by utilizing green fluorescence protein (GFP) based thermometers (see article 2201664). The Ka-Leung Wong group reported a Eu(III)-based complex as a small-molecule optical imaging agent which shows off–on luminescence and realized real-time quantitative analysis for the progress of the bioorthogonal reaction (see article 2203057). In recent years, in vivo optical imaging in the second-near-infrared window (NIR-II, 1000–1700 nm) with reduced photon scattering and autofluorescence received an increasing attention, which allows high spatiotemporal resolution and imaging depth. Niko Hildebrandt et al. prepared NIR-II-emitting ultrasmall gold nanoclusters encapsulated polymer nanoparticles to accomplish 3.8 × 106 M–1 cm–1 of brightnesses (see article 2201474). Furthermore, the themes about near-infrared windows I and II phosphors for theranostic applications (Ru-Shi Liu et al., see article 2202061) and NIR-II lanthanide luminescent nanocrystals for improved biomedical application (Fan Zhang et al., see article 2202039) are reviewed, respectively, having a significant meaning for further application of NIR-II bioimaging. Persistent luminescence also attracted a wide range of research interests, with the exception of NIR-II bioimaging. For instance, Bruno Viana et al. presented persistent luminescence at 700 nm after charging with a 980 nm laser, which helps increase rechargeability capacity as the excitation wavelength is fully inside the biological window (see article 2201468). In addition, the Piaoping Yang group highlighted the recent progress in inorganic afterglow materials, containing mechanisms, persistent luminescent properties, modulating methods, and bioimaging applications (see article 2202382). Similarly, a comprehensive overview of the recent advances in the development of semiconducting polymer nanoparticles in the NIR-II region for biomedical imaging and therapeutics are presented by Changfeng Wu and his co-workers (see article 2202052). Cancer phototherapy is a method that uses NIR light to achieve noninvasive tumor treatment and usually includes photothermal therapy (PTT), photodynamic therapy (PDT) and light controlled drug release. Due to its low energy requirements and deeper penetration of NIR light in comparison with visible light, NIR light guided cancer phototherapy possesses better biosecurity and lower tissue damage. In this special issue, 5 research articles about tumor phototherapy are prominently displayed, including bismuth-based nanoparticles (Chuanbin Mao et al., see article 2201482), manganese-silicon nanocomposite (Jun Lin et al., see article 2202022), metal-organic frameworks (Yanli Zhao et al., see article 2201043), upconversion nanoparticles (UCNPs) (Chunxia Li et al., see article 2202060) and copper peroxide nanomaterials (Ping'an Ma et al., see article 2202040). As a representative NIR light responsive nanomaterials, UCNPs can modify the NIR irradiation to visible light through a multiple-photon process, which has been widely applied in imaging, drug delivery, and antitumor therapy. Here, 3 review articles about UCNPs for biomedical applications are also recommended, such as NIR-to-ultraviolet UCNPs (Feng Wang et al., see article 2201716), heterostructures combining UCNPs and metal-organic framework (Guanying Chen et al., see article 2202122) and bacteria-targeted UCNPs (Xueyuan Chen et al., see article 2202386). Moreover, thanks to the noninvasive character, NIR light responsive materials for diagnosis and treatment of brain diseases are also summarized (Yinghui Wang et al., see article 2202888). This special issue highlights the advance in synthetic technology of high-quality optical nanomaterials for cancer theranostics. By means of the efficient energy transfer process and suitable surface modification, the bioimaging or labeling with light-triggered drug release, sensing, therapy and so on have been integrated to form multifunctional theranostic platform within one single item. These improvements are promising to exceed the cellular level and preclinical trials, further to be applied in the clinical translation. In summary, this special issue is in honor of the 10th anniversary of the Advanced Optical Materials publication which greatly promoted the development of optical nanomaterials science especially in biomedical field in last decade. In addition, we would like to express our gratitude to all authors for their supports and contributions. We also wish that all readers can derive enjoyment and inspiration from this themed issue. Jun Lin received B.S. and M.S. degrees in Jilin University, and a Ph.D. degree in Changchun Institute of Applied Chemistry (1995). His postdoctoral studies were performed at the City University of Hong Kong (1996), Institute of New Materials (Germany, 1997), Virginia Commonwealth University (USA, 1998), and University of New Orleans (USA, 1999). He has been working as a Professor at CIAC since 2000. His research interests include bulk- and nanostructured luminescent materials and multifunctional composite materials, together with their applications in display, lighting, and biomedical fields. Bengang Xing received his Ph.D. degree from Nanjing University in 2000, after which he did his postdoctoral studies in HKUST, UCLA, and Stanford University. He joined Nanyang Technological University (NTU) in 2006. Currently, he is a full professor in the School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, Singapore. His research interest is at the interfaces of bio-fluorescence imaging, chemical biology and nano-medicines, mainly focusing on the development of “smart” small molecules, peptides, and nanoprobes for biological process monitoring and diagnosis. Dayong Jin obtained his PhD from Macquarie University in 2007. At Macquarie, he was promoted to Lecturer in 2010, Senior Lecturer in 2013, Associate Professor in 2014, and Professor in 2015. He joined UTS in 2015, as a Chair Professor, and was promoted to Distinguished Professor in 2017. He established the Australian Industry Transformation Research Hub (ARC IDEAL Hub), and the UTS Institute for Biomedical Materials & Devices (IBMD), to transform advances in phonics and materials into disruptive biotechnologies. He is a Clarivate Highly Cited Researcher, a fellow of the Australian Academy of Technology and Engineering, and an ARC Laureate Fellow, with expertise covering biomedical engineering, nanotechnology, microscopy, microfluidics, and analytical chemistry, to enable rapid detection of cells and molecules.