Magnetic gold nanoparticles as a vehicle for fluorescein isothiocyanate and DNA delivery into plant cells

Magnetic gold nanoparticles (mGNPs) with uniform size and morphology synthesized by our sonication treatment method were covalently bound with fluorescein isothiocyanate (FITC) molecules. Driven by an external magnetic field, FITC-labelled nanoparticles were delivered into plant cells with and without cell walls, evident from sectional transmission electron microscopy images. Confocal images further indicate that the green fluorescence in canola protoplasts and walled cells indeed came from the FITC molecules, instead of the chloroplasts' autofluorescence. FITC-labelled nanoparticles had a delivery efficiency of 95% based on confocal images. In further study, plasmids were covalently bound with mGNPs, and delivered into canola cells with and without cell walls. After culturing for 48 h followed by staining with 5-bromo-4-chloro-3-indolyl-beta-D-glucuronic acid (X-Gluc), blue colour appeared in the protoplasts, while the walled canola cells showed a green colour that can be interpreted as the combination of blue and yellow from the suspension cells themselves. The presence of the blue colour indicates the expression of the GUS gene; therefore, the plasmids were successfully delivered into the canola cells. Furthermore, on examination, mGNPs were considered to be noncytotoxic by fluorescein diacetate staining.