Performance enhancement of real-time detection of protozoan parasite, Cryptosporidium oocyst by a modified surface plasmon resonance (SPR) biosensor

Surface plasmon resonance (SPR) biosensor based on mixed self-assembled monolayers (SAMs) was developed for real-time detection of Cryptosporidium oocyst. The flow type SPR biosensor consisting of subsequent binding of antibody and oocyst in flowing buffer system was able to detect Cryptosporidium parvum oocyst in real-time with a detection limit of 1 × 106 oocyst/ml. To enhance the sensitivity of real-time detection, the modified flow type SPR biosensor was developed, which consisted of the immunoreaction step between the biotin-antibody and oocysts followed by the binding step of antibody bound oocysts onto the sensor surface. Not only was the immunoreaction yield with batch immune reaction improved, but the accessibility of analytes to the sensor surface was also enhanced since the binding event for SPR signal generation was exchanged to biotin–streptavidin binding with high affinity. Consequently, the real-time detection limit of 1 × 102 oocyst/ml was obtained in the modified flow type biosensor.