Transfection is the process that allows exogenous nucleic acids to bypass the cell membrane to enter into cells. Exogenous nucleic acids commonly used are plasmid DNA, RNA, siRNA and oligonucleotides. Once delivered into cells, nucleic acids modulate gene expression by driving overexpression or silencing of a gene of interest.

Gene overexpression is an indispensable tool for several applications, from understanding the role of gene of interest (gene studies, high-throughput screening), to the production of biologics such as antibodies (protein production) and recombinant viral particles, particularly for therapeutic purposes (virus production for gene & cell therapy).

Gene silencing is a method used to prevent expression of a gene of interest. The expression of a gene can be partially reduced (gene knockdown) or completely blocked (gene knockout). Because any gene can potentially be targeted, gene silencing is a prevalent technique used to develop gene-based therapies to address monogenic pathologies, cancer and in immunotherapy strategies.

Transfection of nucleic acids is used to transiently or stably modifed cells by overexpressing or silencing specific gene(s). Several methods can be used to performed transfection that are generally divided in two different categories: Chemical and physical. There are several physical methods that exist such as electroporation, sonoporation or microinjection but these processes are complex and relatively toxic for mammalian cells. To solve these issues, chemical-mediated transfection offers a great alternative: easiness of use, high transfection efficiency and excellent cell viability. Chemical transfection are typically performed using cationic polymers or lipids that will protect the anionic nucleic acids.

1. Encapsulation of Genetic Material with Transfection Reagent
Nucleic acids are negatively charged due to their polyphosphate backbone and are thus able to interact with positively charged transfection reagents (polymers or lipids). This results in the formation of transfection complexes or nanoparticles, which protect nucleic acids from degradation by nucleases.

2. Cellular Uptake of Nanoparticle
Most cells express negatively charged heparan sulfate proteoglycans on the external surface of their cell membrane, with which positively charged transfection complexes can interact. This interaction is key to trigger cellular uptake via an endocytosis process.

3. Release into the Cytosol and if Needed Transport into the Nucleus for Transcription
Upon cellular uptake, transfection complexes are sequestrated into intracellular vesicles. Our transfection reagents enable the release of nucleic acids into the cytoplasm through vesicle membrane rupture or fusion. Most nucleic acids (oligonucleotides, siRNA, mRNA, etc) stay in the cytoplasm where they are active. In case of gene transfer, plasmid DNA is transported into the nucleus for transient expression) which can become permanent after genome integration (stable expression).