The emergence of novel two-dimensional (2D) monoelemental materials (Xenes) has shown remarkable potential for their applications in different fields of technology, as well as addressing new discoveries in fundamental science. Xenes (e.g., borophene, silicene, germanene, stanene, phosphorene, arsenene, antimonene, bismuthene, and tellurene) are of particular interest because they are the most chemically tractable materials for synthetic exploration. Owing to their excellent physical, chemical, electronic and optical properties, Xenes have been regarded as promising agents for biosensors, bioimaging, therapeutic delivery, and theranostics, as well as in several other new bio-applications. In this tutorial review, we summarize their general properties including the classification of Xenes according to their bulk properties. The synthetic and modification methods of Xenes are also presented. Furthermore, the representative Xene nanoplatforms for various biomedical applications are highlighted. Finally, research progress, challenges, and perspectives for the future development of Xenes in biomedicines are discussed.

We report here a mitochondria-targetable pH-sensitive probe that allows for a quantitative measurement of mitochondrial pH changes, as well as the real-time monitoring of pH-related physiological effects in live cells. This system consists of a piperazine-linked naphthalimide as a fluorescence off–on signaling unit, a cationic triphenylphosphonium group for mitochondrial targeting, and a reactive benzyl chloride subunit for mitochondrial fixation. It operates well in a mitochondrial environment within whole cells and displays a desirable off–on fluorescence response to mitochondrial acidification. Moreover, this probe allows for the monitoring of impaired mitochondria undergoing mitophagic elimination as the result of nutrient starvation. It thus allows for the monitoring of the organelle-specific dynamics associated with the conversion between physiological and pathological states.

Biotin is a promising targeting unit for carcinoma cell lines and the avidin–biotin technology is an exceedingly flexible tool for pretargeting and vector targeting. Thus, biotin conjugation is an attractive choice for achieving site-specific sensing, labeling, and delivery.

Theranostic systems are receiving ever-increasing attention due to their potential therapeutic utility, imaging enhancement capability, and promise for advancing the field of personalized medicine, particularly as it relates to the diagnosis, staging, and treatment of cancer. In this Tutorial Review, we provide an introduction to the concepts of theranostic drug delivery effected via use of conjugates that are able to target cancer cells selectively, provide cytotoxic chemotherapeutics, and produce readily monitored imaging signals in vitro and in vivo. The underlying design concepts, requiring the synthesis of conjugates composed of imaging reporters, masked chemotherapeutic drugs, cleavable linkers, and cancer targeting ligands, are discussed. Particular emphasis is placed on highlighting the potential benefits of fluorogenic reaction-based targeted systems that are activated for both imaging and therapy by cellular entities, e.g., thiols, reactive oxygen species and enzymes, which are present at relatively elevated levels in tumour environments, physiological characteristics of cancer, e.g., hypoxia and acidic pH. Also discussed are systems activated by an external stimulus, such as light. The work summarized in this Tutorial Review will help define the role fluorogenic reaction-based, cancer-targeting theranostics may have in advancing drug discovery efforts, as well as improving our understanding of cellular uptake and drug release mechanisms.

A rhodamine-based probe (FS1) was synthesized and its fluorescence properties and application to an iron-overloaded cell line demonstrated. FS1 underwent fluorogenic changes by the Fe³⁺ -catalyzed reaction, even in the presence of other metal cations in vitro. Chemodosimeter FS1 demonstrated selective and sensitive detection of intracellular Fe³⁺ in hepatocytes.