Single-Domain Antibody Functionalized CdSe/ZnS Quantum Dots for Cellular Imaging of Cancer Cells

Photoluminescent (PL) semiconductor nanocrystals, when spherical in shape also termed as quantum dots (QDs), have attracted significant attention in biolabeling and bioimaging applications. Usually, such bio-oriented applications require targeting to the site of interest, and the use of antibodies is acknowledged as one common strategy for specific and compelling targeting. Conventional antibodies and some of their derivatives have been tested as targeting agents; to the best of our knowledge, the present study is the first with the use of single-domain antibodies (sdAbs) to overcome some disadvantages related to issues such as stability, aggregation, and production cost. Our sdAbs, which are small but fully functional recognition proteins and derived from camelid species, are superior to all of the above antibody choices. This manuscript addresses our efforts on the synthesis and targeting of bioconjugated PL QDs with a sdAb named EG2, which binds strongly to epidermal growth factor receptor (EGFR), a protein of which is widely known as a tumor marker. PEGylation was performed at the same time. The entity of our PEGylated-and-sdAb-conjugated QDs, presented as proof of principle, is robust in. specific labeling of EGFR on in vitro grown SK-BR3 and MDA-MB468 human breast-cancer cells.