Novel nanocomposites consisting of in vivo-biotinylated bacterial magnetic particles and quantum dots for magnetic separation and fluorescent labeling of cancer cells

Novel nanocomposites consisting of nano-sized bacterial magnetic particles (BacMPs) and semiconductor quantum dots (QD) were developed for use in targeting and identifying cancer cells. BacMPs are synthesized by magnetotactic bacterium, Magnetospirillum magneticum AMB-1 and can display functional proteins using gene fusion techniques. In this study, two functional proteins, biotin carboxyl carrier protein (BCCP), derived from AMB-1 and protein G, derived from Streptococcus were displayed on BacMPs. BCCP was biotinylated in AMB-1 cells by endogenous biotin ligase. After purification of in vivo-biotinylated BacMPs, streptavidin and antibodies were immobilized on protein G-BCCP-displaying BacMPs (protein G-BCCP-BacMPs) via biotin and protein G, respectively. Furthermore, multi-color labeling of the protein G-BCCP-BacMPs was achieved with streptavidin-labeled QD. Using streptavidin-QD/protein G-BCCP-BacMP nanocomposites, we successfully demonstrated magnetic manipulation and fluorescent labeling of lung cancer cells.