There are various delivery methods available to transport CRISPR components into cells, these include viral and nonviral methods that each have their benefits and disadvantages respectively.
Viral methods include adeno-associated viruses (AAV), adenoviruses, lentiviruses, etc. These may have efficient delivery but there are concerns with the immunogenicity of the virus and whether there is viral integration into the host genome. Furthermore, the choice of virus is important as they have varying carrying capacities that could limit treatment.
Nonviral methods include lipids based methods and nanoparticles that are coated with various substances, these are beneficial as they are virus-free so there is no risk of an immune response but these are not as efficient as viral delivery due to the breakdown of the endosome.
To date, the delivery of CRISPR to specific cell types has been difficult to achieve and ineffective but a study was published in the Journal of The American Chemical Society in which scientists developed a nonviral cancer coated delivery method to transport CRISPR gene-editing components to specific cell types.
Specifically, zeolitic imidazolate frameworks (ZIFs) contained the CRISPR components and this complex was then coated with a cancer membrane (MCF or HELA cell membrane), this was done to mimic the cancer cells.
It was found that there was a higher uptake of the coated delivery method compared to the non coated delivery method in cells. Furthermore, the complex coated with MCF membrane and the complex coated with HELA membrane were taken up significantly by MCF-7 cells and HELA cells respectively. Thereby showing that the specific coating makes the delivery method selective to the target cell type.
In respect to gene editing, researchers wanted to disrupt a fluorescence gene (EGFP), it was found that MCF coated delivery had 3 fold repression in EGFP expression in MCF cells whereas HELA coated delivery had 1 fold repression in EGFP expression in MCF cells, showing that the gene-editing was also more efficient when the coating is specific to the target cell type.
Lastly, the MCF coated delivery was injected into mice, it had accumulated at the tumour site expressing MCF-7 whereas the control did not. Therefore, making the delivery specific for a certain cell type in vivo as well as in vitro.
Coating the delivery method with a cancer membrane directs the complex towards cancerous cells due to a phenomenon called homotypic targeting, whereby cancer cells adhere to each other to form tumours.