Plasmids are circular double stranded DNA molecules that can autonomously replicate outside of chromosomes, mainly used in fields such as genetic engineering, protein expression, and gene therapy. The core of plasmids is the ability to autonomously replicate and screen for markers.

The main applications of plasmids include:

Gene cloning and vector construction: as a basic vector, carrying the target gene into host cells (such as Escherichia coli) for gene amplification, sequencing, or functional research.

Protein expression system: Construct expression plasmids (such as prokaryotic pET series, eukaryotic pcDNA series) to induce the production of recombinant proteins (enzymes, antibodies, vaccine antigens, etc.) in bacteria and mammalian cells.

Gene function and regulation research: Knocking down/knocking out/editing genes in cell models through overexpression, RNA interference (shRNA plasmid), or CRISPR-Cas9 plasmid to analyze biological functions.

Cell screening and labeling: Carrying resistance genes (such as ampicillin, puromycin, etc.) facilitates stable screening of transfected cells; Or fuse fluorescent protein genes to achieve live cell imaging and subcellular localization.

Gene therapy and vaccine development: In clinical practice, modified plasmids (such as DNA vaccines and CAR-T spare plasmids) are used to deliver therapeutic genes or editing elements.

Plasmids have become a core tool in life science experiments for studying proteins, producing proteins, and modifying cells.