Labeling and intracellular tracking of functionally active plasmid DNA with semiconductor quantum dots

Area of Science:

• Biotechnology
• Nanotechnology
• Cell Biology

Background:

• Semiconductor nanocrystal quantum dots (QDs) offer high photostability for long-term cellular imaging.
• Existing QD biolabeling methods target proteins, peptides, and oligonucleotides.
• Intracellular and intranuclear tracking of plasmid DNA remains a challenge.

Purpose of the Study:

• To develop QD-decorated plasmid DNA for long-term intracellular and intranuclear tracking.
• To investigate the conjugation of QDs to plasmid DNA using a PNA linker.
• To assess the expression efficiency of QD-DNA conjugates in cells.

Main Methods:

• Conjugation of phospholipid-coated QDs to plasmid DNA via a peptide nucleic acid (PNA) linker.
• Structural confirmation using gel electrophoresis, confocal microscopy, and atomic force microscopy (AFM).
• Transfection of Chinese hamster ovary (CHO-K1) cells with QD-DNA conjugates to evaluate reporter protein expression.

Main Results:

• Successful conjugation of QDs to plasmid DNA was confirmed by gel electrophoresis and microscopy.
• AFM imaging showed QDs clustered at PNA-reactive sites on the plasmid DNA.
• QD-DNA conjugates achieved approximately 62% reporter protein expression in CHO-K1 cells, comparable to unconjugated DNA.

Conclusions:

• QD-decorated plasmid DNA is a viable tool for long-term intracellular and intranuclear tracking.
• The PNA-linker strategy enables efficient QD conjugation to plasmid DNA.
• QD-DNA conjugates maintain transfection efficiency and reporter gene expression, demonstrating their potential in gene delivery and bioimaging.