Application of biomimetically synthesized magnetic nanoparticles to the improvement of biosensor detection in soils contaminated with metal(loid)s

Co-contamination of soils is an increasingly severe environmental issue, requiring rapid, effect-based tools to assess ecological risks in complex soils. In this study, we developed a high-performance magnetic nano-biosensor by assembling biomimetically synthesized Fe 3 O 4 @Mms6 nanoparticles with the marine, luminescent bacterium, Photobacterium phosphoreum ( P. phosphoreum ), and its proof of concept by the toxicity of metal(loid)s mixtures. Fe 3 O 4 @Mms6 exhibited favorable properties for biosensor construction, including a uniform size (16.05 nm), high magnetic responsiveness (74 emu g −1 ), and minimal toxicity to P. phosphoreum. These attributes enabled enhanced luminescence (approximately 2800 mV) and stable magnetic recovery of the assembled biosensor. Compared with free P. phosphoreum , the biosensor showed greater sensitivity, reducing the EC 50 for Hg 2+ -induced luminescence inhibition from 1.29 to 0.93 mg kg −1 and lowering the coefficient of variation (CV) from 13.02% to 8.39%. Dose–response relationships further confirmed sensitivity to Hg 2+ and Zn 2+ . Optimal biosensor performance was achieved at a salinity of 2.98%, pH 7.01, and a soil-to-water ratio of 0.039 g mL −1 with a 30 min incubation. Field application at a coal chemical site revealed a significant correlation between biosensor responses and the comprehensive potential ecological hazard index (HI) (Pearson r 2 = 0.81, p  < 0.01). Overall, this study provides a robust and field-applicable approach for assessing the toxic potential of contaminated soils.