Selective staining of actin in live human dermal fibroblast cells using quantum dots

Semiconductor quantum dots (QD) are nanometer size fluorophores with improved brightness, resistance against photobleaching and narrow emission bands. These properties make QDs ideal for ultrasensitive imaging of biomolecules in living cells, in multiplexed format. By conjugating QDs with a delivery agent such as TAT peptide and a target-recognition element such as an antibody, we have delivered and imaged target-specific fluorescent probes in living cells. In this work, we demonstrate staining of actin filaments in living Human Dermal Fibroblast (HDF) cells using QD probes functionalized with monoclonal actin antibody. Actin probes were developed by coupling streptavidin coated QDs (λ _em = 605 nm, QDC Corp.) to biotinylated monoclonal β-actin antibody. Antibody molecules on QDs were conjugated with the TAT peptide. Finally, HDF cells were incubated with the QD-actin antibody-TAT construct. As expected, the characteristic fine streaks of actin filaments were observed in the cells and on the periphery of the cells, similar to phalloidin staining of actin filaments in fixed cells. Using a similar approach, one may image cellular components, proteins or nucleic acids, in a living cell, in real time.