Cu2+-assisted fluorescent probe with large stokes shift for specific imaging the accumulation of thiram in vitro and in vivo

Thiram residue poses significant ecological and health risk due to its bioaccumulation and long-term environmental toxicity. Thus, developing specific and sensitive detection method is critical for risk assessment of thiram. Herein, a series fluorescent probes based on 2-(benzo[d]thiazol-2-yl)-4-methylphenol, which further modified with formyl, 4-methylpyridine (4), 4-methylpyridinium salt (5) and 3-methyl-2-methylbenzo [d] thiazole-3-onium iodide (6) were designed (named HBTH, HBTB, HBTP and HBTS, respectively). The four probes displayed maximum emission at 550 nm, 600 nm, 650 nm and 680 nm, respectively, and respond rapidly to Cu²⁺ within 2 s to forming a non-fluorescent complex (HBTR-Cu²⁺, R = H, B, P, S), further for detecting thiram with “light up” ability. Notably, HBTP displayed superior anti-wash capability over other three probes, thus successfully applied to identify Cu²⁺ in vitro and in vivo. Finally, HBTP-Cu²⁺ has achieved the first in vivo visualization of thiram accumulation and distribution to our knowledge, providing a direct and visualized strategy to assess pesticide residue risks.