Phosphorescence-based ratiometric probes: Design, preparation and applications in sensing, imaging and biomedicine therapy

Phosphorescence-based ratiometric probes (PRPs) have multiple advantages from dual-signal ratiometric output, intrinsic signal built-in correction and long-lived luminescence, and exhibit great prospects for sensitive, visual and imaging detection of analytes. In terms of rapid development of PRPs currently, this review systemically discusses and summarizes the recent advances of PRPs in design strategies, preparation methods and versatile applications in chemo/bio-sensing, bioimaging and biomedical therapy. Firstly, we summarize design strategies of PRPs, involving dual-phosphorescence, phosphorescence-fluorescence, and other phosphorescence-based dual-signal ratiometric probes. Afterwards, preparation methods are discussed in detail based upon different compositions, microstructures and luminescent features of PRPs. Then, versatile applications of PRPs are analyzed, principally including chemo/bio-sensing and visual detection of analytes in aqueous samples and biological fluids, biosensing and bioimaging of analytes in live cell and small animal levels, combination of PRPs with other bioimaging modes and biomedicine therapy technologies. Besides, we highlight the types of analytes, samples, sensing mechanisms, bio-toxicity and bio-distribution of PRPs in vitro and in vivo, and provide improvement measures for the shortcomings in previous design, preparation and applications of PRPs. Finally, we discuss current state-of-art, challenges and perspectives in the forthcoming studies of PRPs. This timely and comprehensive review is currently deficient and is desirable for researchers from multidisciplinary fields, and promotes the development of biochemical analysis, bioimaging, biomedical therapy, biosensors, intelligently optical and optoelectronic devices.