Molecular Probes for Sulfatase Detection and Bio-Imaging

Sulfatases are critical enzymes regulating the dynamic sulfation states of biomolecules and have profound implications in human physiology and pathology. Abnormal sulfatase activity is strongly connected to various diseases such as hormone-dependent cancers, infectious diseases like tuberculosis, lysosomal storage disorders, and bacterial virulence, making these enzymes emerge as crucial biomarkers and therapeutic targets. This review highlights the advances in small-molecule probes for selectively detecting sulfatase activity through various imaging modalities, such as fluorescence, photoacoustic, in-gel fluorogenic assays, and bioluminescence imaging. Additionally, the enzyme-activatable probes that exploit mechanisms via self-immolative linkers, intramolecular charge transfer (ICT), photoinduced electron transfer (PET), ratiometric sensing, followed by aggregation-induced emission (AIE), to achieve high specificity and sensitivity. Along similar lines, we explored substrate-based and affinity-based designs, covering turn-on, ratiometric, and dual-modal near-infrared fluorescence, chemiluminescence, and photoacoustic (NIRF/PA) probes that enable real-time, noninvasive, and deep-tissue imaging. A special focus is given to activity-based sensing of steroid sulfatases (STS) in hormone-related cancers and on profiling bacterial sulfatases for rapid mycobacterial strain differentiation. Furthermore, emerging strategies using nanoprobes and AIEgens demonstrate potential for image-guided surgery, inhalable diagnostics, and high-throughput screening of enzyme inhibitors. Together, these innovations establish a strong framework for sulfatase activity profiling and offer powerful capabilities for disease diagnostics, inhibitor screening, and therapeutic monitoring by enabling spatiotemporal visualization of sulfatase activity both in vitro and in vivo. This review may inspire the development of novel activatable sensors suited for practical biomedical applications by consolidating recent advances in sulfatase-targeted probe design and imaging strategies.