Anchoring nanozymes on microneedles via nanotemplate sacrificial synthesis for glutathione detection

Region-specific dysregulation of glutathione (GSH) reflects neuropsychiatric disorders and tumor progression. Microscale precision sampling combined with timely monitoring of GSH provides region-specific molecular information that may aid in disease diagnosis. To enable minimally invasive brain-compatible intraoperative detection of GSH within a limited surgical time window, we designed a 5 mm × 5 mm on-surface microneedle nanozyme sensing platform by adopting a seed-mediated sacrificial template method. The peroxidase (POD)-like nanozyme Prussian blue (PB) probe was grown in situ on a sacrificial ZIF-67 nanotemplate, which was first anchored to the microneedle surface via in situ nucleation to prevent probe detachment in tissue. The dense PB coating substantially increases the immobilization efficiency of GSH aptamers, enabling selective in situ sampling and accumulation of GSH on the nanozyme. This creates a redox antagonistic effect between PB and GSH, which enables the platform to exhibit high selectivity toward GSH over common redox-active interferents. The quantitative concentration range of 271.3-900 μM (R² > 0.99) for GSH is demonstrated in a simulated gelatinous tissue, and GSH levels in brain interstitial fluid could be distinguished within 20 min. Less biopsy tissue and shorter analysis time may help minimize tissue damage and could provide timely intraoperative molecular information, potentially complementing histopathology.