Development and characterization of nanoparticles as imaging probes for correlative optical and electron microscopy

Nanoparticles of several different compositions and lattice structures that have been characterized by transmission electron microscopy, scanning/transmission electron microscopy, X-ray spectroscopic (EDX) analysis, and diffraction patterns may be conjugated to biological targeting agents for use as labels that can localize and differentiate multiple targets at nanometer resolution in complex biological specimens. Small (most 0.8–3.0 nm) particles composed of iron oxide/carbon, gold, iridium and bismuth/silica may be differentiated by both EDX and diffraction patterns and offer the following advantages over conventional colloidal gold labeling: smaller probe size and faster specimen penetration, higher labeling precision, higher, more consistent labeling density, and nearer quantitative labeling. The combination of small probe size and number of compositions available affords increased multiplexing capability.