Development of CRISPR/Cas Delivery Systems for In Vivo Precision Genome Editing

ConspectusClustered, regularly interspaced, short palindromic repeat (CRISPR)/associated protein 9 (CRISPR/Cas9) is emerging as a powerful genome-editing tool, enabling precise and targeted modifications of virtually any genomic sequence in living cells. These technologies have potential therapeutic applications for cancers, metabolic diseases, and genetic disorders. However, several major challenges hinder the full realization of their potential. Specifically, CRISPR-Cas9 gene editors, whether delivered as plasmid DNA, mRNA/sgRNA, or ribonucleoprotein (RNP), exhibit poor membrane permeability, restricting their access to the intracellular genome, where the editing occurs. Additionally, these editors lack tissue or organ specificity, raising concerns about off-target editing at the tissue level that causes unwanted genotoxicity. Though a range of delivery carriers has been developed to deliver Cas9 editors, their effectiveness is often limited by a number of barriers at both the extracellular and intracellular levels. Moreover, the prolonged activity of Cas9 increases the risk of off-target editing at the genomic level. Therefore, it is crucial to develop efficient delivery vectors, along with molecular switches to safely regulate Cas9 activity.In this Account, we summarize our recent achievements in developing different types of materials that can efficiently deliver the plasmid DNA encoding Cas9 protein and single-guide RNA (sgRNA), or Cas9 RNP into cells to highlight the design considerations of carriers for safe and efficient delivery in vitro and in vivo. After elucidating the chemical and physical factors that are responsible for encapsulating and delivering these biomacromolecules, we further elucidate how we design the biodegradable polymeric carriers using dynamic disulfide chemistry, emphasize their safe and efficient delivery features for genome-editing biomacromolecules, and also introduce the integration of the intracellular delivery of genome-editing biomacromolecules with microneedle-based transdermal delivery to promote therapeutic genome editing for inflammatory skin disorders. Finally, we review how we exploit optical, chemical, and genetic switches to control the Cas9 activity in conjunction with targeted delivery to address the spatiotemporal specificity of gene editing in vivo and demonstrate their precision therapy against cancer and colitis treatment as proof-of-concept examples. In the final part, we will summarize the progress we have made and propose the future directions that may impact the field based on our own research outcomes.