Sensitive detection of C. parvum using near infrared emitting Ag2S@silica core–shell nanospheres

Abstract

An optical immunosensor was developed using anti-oocysts McAb immobilized near-infrared (NIR) emitting Ag₂S@silica core–shell nanospheres for the detection of C. parvum in water. The formation of the core Ag₂S and the SiO₂ shell over the core was confirmed by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). The optical properties of the nanostructures were determined by UV-Vis spectroscopy and photoluminescence (PL) studies. The core–shell Ag₂S@silica nanospheres exhibited an intense emission peak at 896 nm which falls in the biological window. TEM images confirm the presence of a uniform core–shell structure, with a Ag₂S core with an average size of 80 nm, and a silica shell with a thickness of 40–50 nm. The C. parvum antibody anti-oocysts McAb immobilized Ag₂S@silica nanoparticles were used as detector probes and these biosensors exhibited excellent analytical performance toward the detection of C. parvum, with detection limits of 10 oocysts per mL with a minimal assay period.