Features of CRISPR-Gold?

Why is gold un-reactive enough to be used as nanoparticles?

Why do cells preform endocytosis upon detection of the gold delivery system? What are the chemical receptors active?

Why is does it cause less genetic damage than doing it virally?

Is this system partly designed to change the DNA of stem cells so that the physiology of the organism changes?

Here is a link

https://www.genengnews.com/gen-news-highlights/crispr-nanoparticles-repair-duchenne-muscular-dystrophy-gene/81255009?q=murthy

Scientists have developed a gold nanoparticle technology for delivering the CRISPR/Cas9 gene-editing system to cells that, when tested in the mdx mouse model of Duchenne muscular dystrophy (DMD), repaired the faulty DMD gene, leading to improved strength and agility and reduced fibrosis. Professor Niren Murthy, Ph.D., the University of California, Berkeley (UC Berkeley) researcher who led development of the CRISPR-Gold platform, suggested to GEN that human clinical gene-editing trials using the system could feasibly start within the next few years.

CRISPR-Gold uses gold nanoparticles to encapsulate all of the elements needed for CRISPR/Cas9 gene editing and deliver them directly to cells. Initial tests in mice achieved levels of gene correction that could demonstrate significant clinical benefit if they can be reproduced in humans, professor Murthy told GEN. “We think a clinical trial for therapeutic gene editing with CRISPR-Gold and its derivatives could happen within 5 years.” However, he added, its not clear whether initial trials will be in DMD, or another disease. “DMD is a very compelling first clinical application of the CRISPR-Gold technology, however there are several others, and it is still too soon to say what the first clinical application will be.”
 
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Thanks for sharing this interesting article.
 

Ygggdrasil

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Here's a link to the peer-reviewed scientific article being discussed:
Lee et al. 2017 Nanoparticle delivery of Cas9 ribonucleoprotein and donor DNA in vivo induces homology-directed DNA repair. Nat Biomed Eng 1: 889
https://www.nature.com/articles/s41551-017-0137-2

Abstract:
Clustered regularly interspaced short palindromic repeats (CRISPR)–CRISPR associated protein 9 (Cas9)-based therapeutics, especially those that can correct gene mutations via homology-directed repair, have the potential to revolutionize the treatment of genetic diseases. However, it is challenging to develop homology-directed repair-based therapeutics because they require the simultaneous in vivo delivery of Cas9 protein, guide RNA and donor DNA. Here, we demonstrate that a delivery vehicle composed of gold nanoparticles conjugated to DNA and complexed with cationic endosomal disruptive polymers can deliver Cas9 ribonucleoprotein and donor DNA into a wide variety of cell types and efficiently correct the DNA mutation that causes Duchenne muscular dystrophy in mice via local injection, with minimal off-target DNA damage.
Why is gold un-reactive enough to be used as nanoparticles?
Gold is considered a Noble Metal because its d-subshell is completely filled. While other transition metals with unfilled d-subshells can participate in redox chemistry using those unpaired d-electrons, gold will not easily undergo such reactions.

Why do cells preform endocytosis upon detection of the gold delivery system? What are the chemical receptors active?
The nanoparticles are functionalized with a cationic polymer, poly(N-(N-(2-aminoethyl)-2-aminoethyl) aspartamide) (PAsp(DET)). The positively-charged polymer can bind to the negatively-charged plasma membrane to aid in endocytosis. AFAIK, the paper did not look at the type of receptor used for endocytosis.

Why is does it cause less genetic damage than doing it virally?
The amount of off-target DNA cleavage caused by CRISPR is thought to increase with the concentration of CRISPR-Cas9 inside of the cells and the amount of time the cells are exposed. The most common methods of viral delivery introduces genes into infected cells that cause the cells to produce large amounts of CRISPR-Cas9 over a prolonged period of time (though one could probably design better viral methods to decrease the extent of CRISPR-Cas9 expression). The nanoparticle method described in the article delivers only the CRISPR-Cas9 protein-RNA complex rather than the DNA genes used to produce the associated protein and RNA. This should reduce the amount of CRISPR-Cas9 inside of the cells as well as the time of exposure, which could decrease the amount of off-target damage (see https://elifesciences.org/articles/04766 for more discussion). However, the authors do not directly compare the method to viral transfection.

Is this system partly designed to change the DNA of stem cells so that the physiology of the organism changes?
The authors tested the ability of the nanoparticles to edit genes in stem cells. The editing rate is quite low, so more work would need to be done for the method to be very practical in altering the physiology or organisms.
 

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