A Novel Fluorescent Nanoparticle for Sensitive Detection of Cry1Ab Protein In Vitro and In Vivo

Here, we report the synthesis and characterization of CoFe 2 O 4 doping Ag 2 S dendrimer-modified nanoparticles (CoFe 2 O 4 -Ag 2 S DMNs) in Cry1Ab protein detection and imaging. The near-infrared Ag 2 S quantum dots were first prepared by using the thermal decomposition method, followed by modification of the water-soluble quantum dots using the method of solvent evaporation and ligand exchange, and finally the fluorescent magnetic bifunctional nanoparticles were obtained by binding with CoFe 2 O 4 . As-prepared CoFe 2 O 4 -Ag 2 S DMNs were characterized by fluorescence (FL) spectroscopy and transmission electron microscopy (TEM). Results showed that Ag 2 S DMNs could sensitively detect Cry1Ab both in vitro and in vivo. In vitro, the enhanced FL intensity as a function of the concentration is notably consistent with the Langmuir binding isotherm equation in the range of 0–200 ng/mL of Cry1Ab proteins. The detection limit of this method was found to be 0.2 ng/mL. Meanwhile, the fluorescence wavelength was extended to the second near-infrared range (NIR-II, 1.0~1.4 μm), which enables in vivo imaging. This study highlights the importance of NIR QDs doping magnetic materials as a new method to trace Bacillus thuringiensis (Bt) in insects and their potential applications in in vivo NIR tissue imaging.