Recent Advances in Fluorescent Probes for Cancer Biomarker Detection Fluorescent probes have emerged as a powerful tool for detecting cancer biomarkers due to their non-invasive, sensitive, and selective properties. This review summarizes recent advances in the design and application of small-molecule and nano-sized fluorescent probes for cancer biomarker detection. The focus is on the development of fluorescent probes for detecting various biomarkers, including enzymes, reactive oxygen species (ROS), reactive sulfur species (RSS), and the tumor microenvironment. Organic small-molecule fluorescent probes, such as BODIPY, rhodamine, and tetraphenylethylene (TPE), have been widely used for cancer biomarker detection. BODIPY-based probes are known for their high fluorescence quantum yield and biocompatibility, making them suitable for detecting pH changes and specific biomarkers like homocysteine (Hcy), cysteine (Cys), and glutathione (GSH). Rhodamine-based probes are effective for detecting hypochlorous acid (HOCl) and nitroreductase (NTR) activity. TPE-based probes, which utilize aggregation-induced emission (AIE), are useful for detecting cancer biomarkers such as matrix metalloproteinases (MMPs). Nano-fluorescent probes, including metal nanoclusters (MNCs), fluorescent nanoparticles (FNPs), and quantum dots (QDs), have also been developed for cancer biomarker detection. These probes offer advantages such as high sensitivity, stability, and the ability to detect multiple biomarkers simultaneously. For example, MNCs have been used to detect metal ions, ROS, and DNA, while QDs have been applied for in vivo imaging and deep tissue visualization. Fluorescent probes for different enzymes, such as glycosidases and nitroreductases, have been developed to detect enzyme activity in cancer cells. These probes enable real-time monitoring of enzyme functions, which is crucial for understanding cancer progression and treatment efficacy. Additionally, fluorescent probes for ROS/RSS, such as hydrogen peroxide (H2O2) and glutathione (GSH), have been developed to monitor oxidative stress and redox status in cancer cells. Fluorescent probes for cancer microenvironmental factors, including pH and viscosity, have been designed to detect changes in the tumor microenvironment. These probes are essential for cancer diagnosis and treatment monitoring. For example, pH-sensitive probes can detect acidification in tumor tissues, while viscosity-sensitive probes can monitor changes in intracellular viscosity. Despite significant progress, challenges remain in the clinical application of fluorescent probes for cancer diagnosis. These include improving tissue penetration, enhancing probe specificity, and ensuring long-term stability. Future developments in multifunctional fluorescent probes are expected to address these challenges and improve the accuracy of cancer diagnosis.Recent Advances in Fluorescent Probes for Cancer Biomarker Detection Fluorescent probes have emerged as a powerful tool for detecting cancer biomarkers due to their non-invasive, sensitive, and selective properties. This review summarizes recent advances in the design and application of small-molecule and nano-sized fluorescent probes for cancer biomarker detection. The focus is on the development of fluorescent probes for detecting various biomarkers, including enzymes, reactive oxygen species (ROS), reactive sulfur species (RSS), and the tumor microenvironment. Organic small-molecule fluorescent probes, such as BODIPY, rhodamine, and tetraphenylethylene (TPE), have been widely used for cancer biomarker detection. BODIPY-based probes are known for their high fluorescence quantum yield and biocompatibility, making them suitable for detecting pH changes and specific biomarkers like homocysteine (Hcy), cysteine (Cys), and glutathione (GSH). Rhodamine-based probes are effective for detecting hypochlorous acid (HOCl) and nitroreductase (NTR) activity. TPE-based probes, which utilize aggregation-induced emission (AIE), are useful for detecting cancer biomarkers such as matrix metalloproteinases (MMPs). Nano-fluorescent probes, including metal nanoclusters (MNCs), fluorescent nanoparticles (FNPs), and quantum dots (QDs), have also been developed for cancer biomarker detection. These probes offer advantages such as high sensitivity, stability, and the ability to detect multiple biomarkers simultaneously. For example, MNCs have been used to detect metal ions, ROS, and DNA, while QDs have been applied for in vivo imaging and deep tissue visualization. Fluorescent probes for different enzymes, such as glycosidases and nitroreductases, have been developed to detect enzyme activity in cancer cells. These probes enable real-time monitoring of enzyme functions, which is crucial for understanding cancer progression and treatment efficacy. Additionally, fluorescent probes for ROS/RSS, such as hydrogen peroxide (H2O2) and glutathione (GSH), have been developed to monitor oxidative stress and redox status in cancer cells. Fluorescent probes for cancer microenvironmental factors, including pH and viscosity, have been designed to detect changes in the tumor microenvironment. These probes are essential for cancer diagnosis and treatment monitoring. For example, pH-sensitive probes can detect acidification in tumor tissues, while viscosity-sensitive probes can monitor changes in intracellular viscosity. Despite significant progress, challenges remain in the clinical application of fluorescent probes for cancer diagnosis. These include improving tissue penetration, enhancing probe specificity, and ensuring long-term stability. Future developments in multifunctional fluorescent probes are expected to address these challenges and improve the accuracy of cancer diagnosis.