Indicator displacement assays (IDAs) offer a unique and innovative approach to molecular sensing. IDAs can facilitate the detection of a range of biologically/environmentally important species, provide a method for the detection of complex analytes or for the determination and discrimination of unknown sample mixtures. These attributes often cannot be achieved by traditional molecular sensors i.e. reaction-based sensors/chemosensors. The IDA pioneers Inouye, Shinkai, and Anslyn inspired researchers worldwide to develop various extensions of this idea. Since their early work, the field of indicator displacement assays has expanded to include: enantioselective indicator displacement assays (eIDAs), fluorescent indicator displacement assays (FIDAs), reaction-based indicator displacement assays (RIAs), DimerDye disassembly assays (DDAs), intramolecular indicator displacement assays (IIDAs), allosteric indicator displacement assay (AIDAs), mechanically controlled indicator displacement assays (MC-IDAs), and quencher displacement assays (QDAs). The simplicity of these IDAs, coupled with low cost, high sensitivity, and ability to carry out high-throughput automation analysis (i.e., sensing arrays) has led to their ubiquitous use in molecular sensing, alongside the other common approaches such as reaction-based sensors and chemosensors. In this review, we highlight the various design strategies that have been used to develop an IDA, including the design strategies for the newly reported extensions to these systems. To achieve this, we have divided this review into sections based on the target analyte, the importance of each analyte and then the reported IDA system is discussed. In addition, each section includes details on the benefit of the IDAs and perceived limitations for each system. We conclude this Tutorial Review by highlighting the current challenges associated with the development of new IDAs and suggest potential future avenues of research.

Transition metal chelators and ionophores have shown promise as alternative chemotherapeutic strategies by selectively altering the concentrations of iron, copper, and zinc in cancer cells.

Central nervous system (CNS) neurodegeneration is defined by a complex series of pathological processes that ultimately lead to death. The precise etiology of these disorders remains unknown. Recent efforts show that a mechanistic understanding of the malfunctions underpinning disease progression will prove requisite in developing new treatments and cures. Transition metals and lanthanide ions display unique characteristics (i.e., magnetism, radioactivity, and luminescence), often with biological relevance, allowing for direct application in CNS focused imaging modalities. These techniques include positron emission tomography (PET), single-photon emission computed tomography (SPECT), magnetic resonance imaging (MRI), and luminescent-based imaging (LumI). In this Tutorial Review, we have aimed to highlight the various metal-based imaging techniques developed in the effort to understand the pathophysiological processes associated with neurodegeneration. Each section has been divided so as to include an introduction to the particular imaging technique in question. This is then followed by a summary of key demonstrations that have enabled visualization of a specific neuropathological biomarker. These strategies have either exploited the high binding affinity of a receptor for its corresponding biomarker or a specific molecular transformation caused by a target species, all of which produce a concomitant change in diagnostic signal. Advantages and disadvantages of each method with perspectives on the utility of molecular imaging agents for understanding the complexities of neurodegenerative disease are discussed.

Herein, we report a protein-based hybridization strategy that exploits the host–guest chemistry of HSA (human serum albumin) to solubilize the otherwise cell impermeable ONOO ⁻ fluorescent probe Pinkment-OAc .