Ultra-large stokes shift probe enables SIM super-resolution tracking of lysosomal acidification impairment in Aβ trafficking dysregulation during Alzheimer's disease.

Lysosomal acidification deficits are increasingly recognized as early events in Alzheimer's disease (AD), yet tools for real-time pH monitoring remain limited. Here, we report AHP, a pH-sensitive fluorescent probe with rapid response (ΔpH ≥0.2), high lysosomal specificity, ultra-large Stokes shift (>240 nm), and excellent photostability for long-term imaging. AHP enabled visualization of biphasic Aβ42-induced lysosomal pH dysregulation-initial hyperacidification followed by pathological alkalinization-directly linking acidification failure to impaired Aβ42 clearance. Dual-channel live imaging showed that reduced lysosomal acidity disrupts Aβ42 degradation, leading to cytoplasmic accumulation and increased toxicity.Using AHP-based high-throughput screening, we identified protocatechuic aldehyde as a lysosomal acidification enhancer and validated its efficacy in restoring autophagic flux. As the probe to achieve super-resolution tracking of lysosomal pH in neurodegeneration, AHP connects pH dynamics with AD pathogenesis and offers a powerful tool for mechanistic insight and drug discovery.This work establishes lysosomal pH homeostasis as a critical target in early AD intervention and highlights the broad applicability of AHP in aging-related disorders.