Impedance-based porous silicon biosensor functionalized with an ssDNA aptamer for Escherichia coli recognition

The growing need for alternative bacterial recognition platforms has increased interest in aptamer-functionalized biosensors. This study evaluated a single-stranded DNA (ssDNA) aptamer-functionalized porous silicon platform for the recognition of Escherichia coli under controlled experimental conditions. A previously reported E. coli-binding E1 aptamer was immobilized on porous silicon, and aptamer-bacterium interactions were assessed using fluorescence microscopy and impedance spectroscopy. Fluorescence microscopy demonstrated aptamer binding in 58 of 62 E. coli clinical isolates, while no detectable fluorescence signal was observed with the tested non-target bacterial species, including Klebsiella pneumoniae, Staphylococcus aureus, Enterococcus faecium, and Pseudomonas aeruginosa. Impedance measurements showed distinguishable signal changes after exposure of the aptamer-functionalized porous silicon surface to E. coli suspensions compared with bacteria-free solutions. The fluorescence-based binding rate should be interpreted as supportive evidence for aptamer-cell interaction rather than as a definitive diagnostic performance parameter of the impedance-based biosensor. Overall, these findings support the feasibility of integrating an E. coli-binding ssDNA aptamer with a porous silicon impedance platform. However, the current dataset remains preliminary, and further validation using larger sample sets, mixed bacterial populations, and complex clinical, food, or environmental matrices is required before practical diagnostic or screening applications can be considered.