Quantum dot nanocrystals (QDs) offer the possibility of a universal marker system suitable for correlative light and electron microscopy (CLEM) studies. Cadmium and selenium (CdSe) nanoparticles (i) may be stimulated to emit light for fluorescence studies, (ii) may be visualised by transmission electron microscopy (TEM) due to their atomic weight (iii) have an elemental signature suitable for EDS detection and mapping by contemporary field emission scanning electron microscopy (FESEM).
Antibody and streptavidin conjugated QDs were used for multiplexed immunohistochemistry studies of archival human pathology tissue. The same probes were also applied to etched epoxy sections for CLEM studies employing widefield epiflourescence, super-resolution (N-SIM) light microscopy and transmission electron microscopy (TEM).
QDs are reliable alternatives to organic fluorophores for use in immunohistochemistry, immunocytochemistry and in-situ hybridisation studies. Their brightness and stability under excitation by 365 nm light was useful for prolonged imaging by epifluorescence or super-resolution light microscopy. Their electron density was adequate for TEM observation but was lower than that of more traditional colloidal gold probes [1]. Facilitation of CLEM studies and convenient evaluation of labelling patterns prior to ultrastructural examination were significant benefits.
Nanoparticle conjugates offer diverse functionality that can be exploited for use as marker systems for immunocytochemistry and CLEM studies. These probes allow functional protein labelling to be seen in structural context at the cell and tissue level. Correlation of different microscopy modalities with use of multiplex marker systems is useful to pathology through maximisation of data available from single biopsy samples.
1. Killingsworth MC et al. J Histochem Cytochem. 2012;60(11):832-843