Integrated detection and recovery of light/medium rare earth elements using Hans-LanM-based fluorescent probe and...

Rare earth elements (REEs) are emerging bioaccumulative contaminants threatening health and ecosystems. However, current detection and recovery technologies face three key bottlenecks: poor selectivity between light and heavy REEs, costly multi-step adsorbents, and a lack of visualized adsorption platforms. Here, we develop a bifunctional platform based on REE-responsive Hans-LanM. Inserting Hans-LanM into sfGFP yields a sensitive probe (sfGFP-LanM) with picomolar affinity, 2 nM detection limit for Sm³ ⁺, excellent selectivity for light/medium REEs, reversibility, and long-term stability. Mechanistically, REE-induced conformational ordering of LanM enhances sfGFP fluorescence by stabilizing its chromophore and increasing the radiative rate. Displaying this fusion protein on E. coli creates a whole-cell adsorption system. The engineered strain achieves 81.5% (Nd³⁺) and 72.6% (Sm³⁺) adsorption vs. 32% (Y³⁺) at 500 μM, an equilibrium capacity of 150 mg/g for Sm³ ⁺, and rapid equilibrium within 30 min. Notably, it maintains selective REE adsorption (55%-70%) in a real soil leachate containing a 10⁶-fold excess of competing ions. Its fluorescence signal linearly correlates with adsorbed amount, enabling real-time monitoring and quantification. The system is efficiently regenerated (>85% desorption at pH 2.3) and maintains > 60% efficiency after 5 cycles. Adsorption kinetics follow a quasi-second-order model, indicating monolayer chemical adsorption, consistent with the molecular recognition mechanism of the probe in solution. Multidimensional characterization reveals that Hans-LanM mediates specific adsorption via synergistic coordination of carboxylate, hydroxyl, and amide groups. This study provides a new strategy with both theoretical depth and application potential for the highly sensitive detection and green recovery of rare earth resources.