Non-viral Chemical Delivery Systems for CRISPR-based Mammalian Genome Editing

Abstract

Non-viral delivery of CRISPR-based agents has risen to a widely studied field. While CRISPR has revolutionized mammalian genome editing with its easiness, the delivery platforms hinder further clinical utilization. Safe and efficient delivery is needed in order to achieve effective genome editing. The adaptivity and extensive modification options of chemical delivery systems could solve the ongoing issues in delivery. However, they face numerous obstacles of their own that are in critical need of tackling. Especially in vivo application has proven to be difficult and usually stumbles to premature degradation.

This thesis reviews the currently promising chemical delivery systems. The delivery is explored through describing the significant obstacles to non-viral chemical delivery and introducing the delivery modes that are used for CRISPR-based agents. Current chemical delivery systems are presented by dividing them into lipid, polymer and peptide mediated carriers. For each group both popular and individual examples are selected from the diversity of carriers. The review focuses on the physical characteristics of the carriers and explains how these aspects have managed to obviate the obstacles of delivery. It also highlights the results of the used chemical delivery systems and illustrates the differences between carriers. Possible comparisons between delivery mode results are also presented to show how they can affect the delivery.

On the basis of the studies collected, it can be argued that chemical delivery systems favour multifunctionality. Most of the current carriers are constructed of multiple components that each have their own tasks in the delivery. Various components are needed in order to form a carrier that can counter the obstacles of delivery and deliver CRISPR safely to cells. The thoughtful design in the basis of the carrier enables the conjugation of additional molecules. Furthermore, the design is affected by the chosen delivery mode. Plasmid DNA, messenger RNA and direct ribonucleoprotein complex delivery of CRISPR are each suited for different carriers. It is still unknown whether a specific chemical carrier will rise to be the most optimal for CRISPR-based delivery or if the chemical carriers can be developed further enough to enable effective delivery. However, certain carrier types may be favoured for tissue or cell specific delivery. It is noteworthy that the chemical delivery systems still need additional studies to improve the efficiency of the delivery and to enter clinical trials.