Phototherapy, including photodynamic therapy and photothermal therapy, has the potential to treat several types of cancer.

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.

Identification of bacterial strains is critical for the theranostics of bacterial infections and the development of antibiotics. Many organic fluorescent probes have been developed to overcome the limitations of conventional detection methods. These probes can detect bacteria with “off-on” fluorescence change, which enables the real-time imaging and quantitative analysis of bacteria in vitro and in vivo. In this review, we outline recent advances in the development of fluorescence-based dyes capable of detecting bacteria. Detection strategies are described, including specific interactions with bacterial cell wall components, bacterial and intracellular enzyme reactions, and peptidoglycan synthesis reactions. These include theranostic probes that allow simultaneous bacterial detection and photodynamic antimicrobial effects. Some examples of other miscellaneous detections in bacteria have also been described. In addition, this review demonstrates the validation of these fluorescent probes using a variety of biological models such as gram-negative and -positive bacteria, antibiotic-resistant bacteria, infected cancer cells, tumor-bearing, and infected mice. Prospects for future research are outlined by presenting the importance of effective in vitro and in vivo detection of bacteria and development of antimicrobial agents.

Hydrazide-linked naphthalimides undergo copper ion-selective hydrolysis with concomitant ratiometric fluorescence change. In addition, probe 1 is biocompatible and mainly localized to the endoplasmic reticulum (ER) in live HeLa cells. It thus can be used for imaging copper accumulation in the ER of live cells, as implied in copper-overloaded situations.