Development of an aptasensor for the detection of outer membrane vesicles derived from Escherichia coli
Rapid and reliable detection of bacterial pathogens is essential for clinical diagnostics and food safety monitoring. This study explores bacterial outer membrane vesicles (OMVs), nanoscale particles naturally released by Gram-negative bacteria such as Escherichia coli, as diagnostic surrogates for intact cells. An E. coli-specific aptamer was conjugated to indium phosphide–zinc sulphide quantum dots to evaluate its ability to recognise vesicles derived from the bacterial outer membrane. Optical measurements together with high-resolution transmission electron microscopy confirmed aptamer-mediated binding of the quantum dot-aptamer conjugates to these vesicles. To investigate biosensing performance, the same aptamer was immobilised on gold electrodes and vesicle recognition was monitored using electrochemical impedance measurements. The resulting sensor showed a concentration-dependent increase in interfacial charge-transfer resistance across a vesicle concentration range of 107−109 vesicles/ml and demonstrated strong selectivity towards E. coli-derived vesicles compared with those from Pseudomonas aeruginosa. These findings demonstrate that aptamer-functionalised nanomaterials can selectively target bacterial OMVs and highlight their potential as stable biomarkers for vesicle-based bacterial detection platforms.