A Wash-Free Fluorescent Probe with Synergistic Signal Amplification for Sperm Microenvironment Evaluation and Asthenospermia Detection

Sperm quality assessment is critical for the diagnosis of male infertility. However, conventional methods mainly focus on kinematic parameters and fail to real-time monitor the dynamic intracellular microenvironment of sperm. Single-parameter detection also suffers from insufficient sensitivity and specificity under complex interference, making it difficult to accurately identify functionally impaired sperm. Herein, we designed and synthesized two near-infrared fluorescent probes, QSi-BA and QSi-OBA, based on silicon-xanthene scaffolds via a one-step modification. QSi-OBA shows a remarkable synergistic fluorescence enhancement response to acidic and high-viscosity microenvironments, together with high photostability and excellent anti-interference ability. The probe enables wash-free, real-time imaging of dynamic microenvironmental changes in human sperm. Using drug-induced stimulation models, we verified its capability to monitor pH and viscosity perturbations. More importantly, QSi-OBA can effectively distinguish asthenospermic sperm from healthy samples, without relying on normal routine semen parameters. This probe provides a powerful and reliable molecular imaging tool for precise sperm function evaluation, auxiliary diagnosis of male infertility, and related reproductive pathological studies.