Coumarins are a very large family of compounds containing the unique 2H-chromen-2-one motif, as it is known according to IUPAC nomenclature. Coumarin derivatives are widely found in nature, especially in plants and are constituents of several essential oils. Up to now, thousands of coumarin derivatives have been isolated from nature or produced by chemists. More recently, the coumarin platform has been widely adopted in the design of small-molecule fluorescent chemosensors because of its excellent biocompatibility, strong and stable fluorescence emission, and good structural flexibility. This scaffold has found wide applications in the development of fluorescent chemosensors in the fields of molecular recognition, molecular imaging, bioorganic chemistry, analytical chemistry, materials chemistry, as well as in the biology and medical science communities. This review focuses on the important progress of coumarin-based small-molecule fluorescent chemosensors during the period of 2012− 2018. This comprehensive and critical review may facilitate the development of more powerful fluorescent chemosensors for broad and exciting applications in the future.

Photodynamic therapy (PDT) has been extensively investigated for decades for tumor treatment because of its non-invasiveness, spatiotemporal selectivity, lower side-effects, and immune activation ability.

Both chronic and acute neurodegenerative diseases have been associated with high morbidity and mortality, along with the death of neurons in different areas of the brain, and there are few or no effective curative therapy options for treatment of patients. [3,4] These disorders are a major cause of concern for the health and quality of life in the aging society, since age is the greatest risk factor for neurodegenerative disease. [5] The World Health Organization has predicted that in next 20 years neurodegenerative disease will become the second most common cause of mortality after cardiovascular disease. [6] Neurodegenerative processes begin long before their clinical symptoms are evident, and evolve for years slowly and irreversibly. Hence, there is an urgent need to diagnose neurodegenerative disease as early as possible and to distinguish between different neurodegenerative disorders with shared and unique symptoms to facilitate decision making regarding choice of treatment. Timely diagnosis is important for the adoption of therapeutic modalities in clinical trials prior to moderate dementia exhibition, to appraise and apply antidotes to maximally preserve the cognitive functions or to slow down the course of these disorders. The ability to analyze and identify risk factors for cognitive deficit would represent an extraordinary advancement in the field of dementia. [5] The main modern diagnostic technologies for the early examination of neurodegenerative disease pathology, neuroimaging techniques, include radioligandsbased positron emission tomography (PET), 3D single-photon emission-computed tomography (SPECT), and structural magnetic resonance imaging (MRI). Although PET and SPECT are the most used imaging techniques for neurodegenerative diseases, their application is limited by high cost, involvement of hazardous radiolabeled compounds, need for sophisticated instruments, and application of complex data acquisition and analysis protocols. The MRI technique has relatively low spatial resolution as well as intrinsically poor sensitivity to distinguish morphological differences between disease biomarkers and the surrounding tissue. Recently, fluorescence diagnosis technology has become an attractive and potential alternative to diagnose and probe the progression of neurodegenerative diseases, because of being rapid, noninvasive, sensitive, simple, real-time, low-cost, and high-resolution in nature. [7] There are several uses for Neurodegenerative diseases are debilitating disorders that feature progressive and selective loss of function or structure of anatomically or physiologically associated neuronal systems. Both chronic and acute neurodegenerative diseases are associated with high morbidity and mortality along with the death of neurons in different areas of the brain; moreover, there are few or no effective curative therapy options for treating these disorders. There is an urgent need to diagnose neurodegenerative disease as early as possible, and to distinguish between different disorders with overlap...

Characteristics of CSCs targeted for developing therapeutic and bio-imaging agents.