GaAs/AlGaAs heterostructure based photonic biosensor for rapid detection of Escherichia coli in phosphate buffered saline solution

We have investigated photonic biosensing of bacteria based on photoluminescence (PL) of GaAs/AlGaAs heterostructures. The method takes advantage of the GaAs PL sensitivity to the perturbation of the semiconductor near-surface electric field induced by the charge of bacteria immobilized in its vicinity. Maintaining the balance between device sensitivity and stability in the biosensing (aqueous) environment is one of the key parameters allowing successful biosensing. To immobilize bacteria, we have employed a network of biotinylated antibodies interfaced with biotinylated polyethylene glycol thiols through the link provided by neutravidin. Post-processing of thiolated samples in ammonium sulfide was applied to increase the stability of the biosensing architectures while allowing biosensing at an attractive level of detection. Escherichia coli was detected in phosphate buffered saline solutions at 103 CFU/mL; however, it appears that even greater sensitivity levels are feasible with this technique.