Significance In recent years, there has been significant progress in the development and application of nanomaterials in the field of bio-optics. These advancements have led to benefits for medical diagnosis and treatment, such as biosensing, bioimaging, cell tracking, and phototherapy. Nanomaterials possess unique properties that allow for advances in targeting, precision, resolution, real- time and non-invasive detection for bio-optical applications. Among a large number of luminescent nanomaterials, organic semiconducting polymer dots (Pdots) have attracted extensive attention due to their large absorption cross sections, high brightness, stable photostability, excellent biocompatibility, and tunable spectra. Compared to traditional luminescent dyes, which have weak photostability, low brightness, and short lifetime, Pdots have smaller sizes and higher photophysical properties, which contribute to better conversion efficiency and detection results. Pdots have been widely used in the bio-optical field, including in biosensing, bioimaging, and phototherapy applications, which are of great significance for point-of-care testing, in vivo imaging, and tumor therapy. Point-of-care testing based on biosensing technology enables the specific and rapid detection of analytes, which contain significant physiological information. This promotes patient self-management of health. The outstanding sensitivity, response time, selectivity, and reversibility of Pdots make it possible to ensure the convenience and speed of detection while maintaining the same accuracy as laboratory testing. Apart from biosensing, bioimaging technology realizes the visualization of internal structure of organisms and achieves functional imaging for significant medical signals, offering accurate and reliable information for disease diagnosis and treatment. Pdots used as optical probes usually provide near-infrared imaging, which has deeper penetration and lower background interference compared to conventional contrast agents. More importantly, the excellent specificity and tumor targeting capabilities of Pdots enable more effective medical images for in vivo tumor imaging. With their multimodal imaging ability, Pdots have been applied in the field of multimodal imaging, serving as fluorescent probes while giving other imaging signals such as photoacoustic imaging (PAI), magnetic resonance imaging, or computed tomography, which simultaneously provide location and physiological signals of the detection region. In addition, cancer phototherapy depends on energy transfer to damage or kill the tumor cells while avoiding damage to normal tissue, including photothermal therapy (PTT), photodynamic therapy (PDT), and photoimmunotherapy. Traditional therapeutic agents have limited therapeutic efficacy and are prone to cause damage to normal tissue. In contrast, Pdots possess the ability to be easily modified and have high conversion efficiency, resulting in enhanced tumor targeting and smoother drug delivery to the tumor area, which can improve treatment results. The numerous advantages of Pdots make them suitable for bio-optical applications in complex physiological environments, which are highly valuable in biomedical research. Pdots have become one of the crucial materials for biosensing, bioimaging, and optical therapy, aiding in the diagnosis and treatment of diseases, especially in cancer treatment. Progress The luminescence mechanisms of Pdots are summarized, including fluorescence, phosphorescence, and thermally activated delayed fluorescence (Fig. 2). Moreover, this section presents the properties and methods of preparation, modification, and functionalization of Pdots, which are fundamental to their bio-optical applications as specific functional groups enhance the performance of Pdots and extend their range of applications (Fig. 3). Firstly, the biosensing applications of Pdots are introduced to demonstrate their potential in the field of point-of-care testing. NADH-sensitive Pdots bound to specific enzymes were used to detect the concentration of metabolites oxidized by NAD+ or reduced by NADH, including phenylalanine (Fig. 4), lactate, and glutamate. Similarly, oxygen-sensitive Pdots were coupled with glucose oxidase to achieve blood glucose concentration detection for diabetic self-management (Fig. 5). Different modification and functionalization strategies of Pdots enable diverse biosensing applications, including nucleic acids (Fig. 6), tumor markers (Fig. 7) and enzyme activity (Fig. 8). Subsequently, the bioimaging applications of Pdots are presented to show the advantages of Pdots-based probes compared to traditional dyes. Pdots as fluorescence probes ensured in vivo tumor imaging and vascular imaging of mice with a higher signal-to-background ratio and penetration depth (Fig. 9). Pdots-based contrast agents have been successfully applied in PAI for brain tumor imaging, thanks to their efficient metabolizable capacity and excellent biocompatibility (Fig. 10). Furthermore, Pdots that emitted fluorescent and photoacoustic signals have combined fluorescence imaging with PAI to yield dual-modal imaging. Similar principles were extended to other multimodal imaging (Fig. 11). Finally, phototherapy applications demonstrate the capability of Pdots in cancer treatment. Pdots-based PTT agents provided high photothermal conversion efficiency and biosafety to accomplish accurate and effective treatment (Fig. 12). The extraordinary energy transfer efficiency and tumor targeting capability of Pdots compensated for the shortcomings of conventional photosensitizers, resulting in inhibited tumor growth in mice (Fig. 13). In addition, the use of photoimmunotherapy agents in combination with Pdots enhanced the immune response in the tumor area which suppressed tumor growth and metastasis (Fig. 14). Conclusions and Prospects Pdots have been widely used in bio-optical applications such as biosensing, bioimaging, and optical therapeutics. The excellent properties of Pdots allow them to be applied to a wide range of subjects and environments with good results in detection and treatment. In the future, Pdots can be further enhanced in terms of preparation and functionalization, and combined with emerging technologies to achieve intelligent detection and treatment.
