Drug Delivery using CRISPR
CRISPR adapted for hydrogel control
Svetlana Yastrebova, N+1
The ability of the popular CRISPR/Cas genome editing technology to cut DNA strands was used to control the movements of hydrogel beads that were in a network of deoxyribonucleic acid molecules. When changing the configuration of the networks caused by the action of CRISPR, the position of the balls also changed. In the future, CRISPR-controlled hydrogels can be used for targeted drug release and remote triggering of various other processes, according to an article published in Science (English et al., Programmable CRISPR-responsive smart materials).
Cas proteins and short Palindromic repeats (Clustered Regularly Interspaced Short Palindromic Repeats) in DNA, with which these proteins bind, were first discovered in bacteria in 1987, and soon they were discovered in archaea. It turned out that Cas are able to cut single- and double-stranded deoxyribonucleic acid molecules in certain places. This was adopted by American and French biologists led by Jennifer Dudna and tried to assign CRISPR/Cas targets themselves to create breaks in DNA. The technology was refined and tested in the cells of prokaryotes and various eukaryotes: fungi, animals, plants. Now, with the help of CRISPR/Cas, RNA can also be edited, and for a specific purpose, they select their own Cas protein (however, most often it is Cas9).
James Collins and his colleagues from The Massachusetts Institute of Technology and Harvard University went further and applied the ability of CRISPR/Cas to cut nucleic acid molecules for the operation of inanimate systems. They introduced a system with the Cas12a protein into DNA hydrogel, a system of polymer beads forming a colloidal solution in water and separated by DNA strands. Single-stranded bridges formed between these strands, and the task of CRISPR/Cas was to cut them.
The Cas12 protein cuts the bonds between DNA strands, and the particles that were in its networks are released, being able to move (Ewen Callaway / Nature, 2019).
Cutting single-stranded DNA changed the structure of the hydrogel: the surviving double-stranded strands shifted and the network that holds the beads disintegrated, after which they could move freely. Controlled changes in the properties of the hydrogel can be used for targeted delivery of various molecules and cells: to release them where necessary, at the right moment. In one series of experiments, a DNA hydrogel and CRISPR/Cas were placed in a microfluidic chamber. When a methicillin-resistant genetic Staphylococcus aureus (Staphylococcus aureus) or Ebola virus passed through this chamber, the Cas12a protein "noticed" it, the state of the hydrogel changed and the system thereby signaled the presence of foreign DNA.
The researchers tested several types of hydrogel with different particles: polyacrylamide, polyethylene glycol and carbon black. Some of them are more suitable for use in bioelectronics, since they conduct electricity, some are for the release of drugs, since they are capable of decomposing. Also, live cells can be used instead of polymers.
Dan Luo, bioengineer from Cornell University, which was not involved in the study, notes that previously DNA hydrogels could not be controlled using enzymes: they either cut too few molecules, or made incisions in unplanned places. Therefore, creating a system using CRISPR/Cas in this case is a significant step forward.
It is not the first time that CRISPR has been tried to be combined with various specialized materials. If the current study suggests using the system to deliver drugs, cells, nanoparticles and the like, then a year earlier it itself was transported to the desired organs – the brain and liver – using gold and iron oxide nanoparticles.
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