A new and promising application of gene editing: CRISPR-controlled smart materials for tissue engineering, bioelectronics, and diagnostics

Abstract

A recent study published in the journal Science by Collins et al. proposed a programmable clustered regularly interspaced short palindromic repeats (CRISPR)-responsive smart material containing the CRISPR-associated nuclease, Cas12a, and hydrogels containing DNA to deliver biological information via changes in material properties (English et al., 2019). This dramatically broadens the scope of application of CRISPR systems for tissue engineering, bioelectronics, and diagnostics. Site-specific gene nucleic acid editing is achieved by direct or RNA-guided nucleic acid-protein recognition, wherein the activity of zinc-finger nucleases (Carroll, 2011) and transcription activator-like effector nucleases (Bi and Yang, 2017; Boettcher and McManus, 2015) is based on direct recognition, and the CRISPR toolbox is applied in an RNAguided manner (Ren et al., 2017). The RNA-guided CRISPR system was developed from the adaptive immunity of bacteria (Hsu et al., 2014; Terns and Terns, 2014), and it achieves gene deletion, insertion, and frameshift mutations by Cas endonuclease and single-stranded guide RNA (gRNA), inducing double-strand breaks with higher efficiency, reduced cost, improved flexibility, and a simplified design process (Doudna and Charpentier, 2014; Ren et al., 2017). Non-homologous end-joining and homology-directed repair mechanisms repair double-stranded DNA (dsDNA) with random base insertions or precise modification in the presence of donor DNA templates, respectively (Singh et al., 2017). CRISPR systems have been widely investigated as promising tools for therapeutic genome editing in agricultural (Shen et al., 2017; Wang et al., 2017), biomedical (He et al., 2017), and clinical settings (He et al., 2017; Zhang et al., 2017). Moreover, apart from genome alternation, transcriptional and post-transcriptional modifications can also be regulated by Cas systems to perturb normal activity in organisms (Knott and Doudna, 2018). Furthermore, catalytically inactive Cas9 could be utilized to image specific genomic loci with fluorescent reporters, providing the potential to further investigate the chromosome dynamics and three-dimensional genome organization in live cells (Knight et al., 2018). Nucleic acid detection and diagnosis are achieved by Cas13a and Cas12a, which exhibit a “collateral effect” with disordered ribonuclease activity upon target recognition. The Specific High-Sensitivity Enzymatic Reporter UnLOCKing (SHERLOCK) platform (Gootenberg et al., 2018; Gootenberg et al., 2017) and DNA Endonuclease Targeted CRISPR Trans Reporter (DETECTR) platform (Chen et al., 2018) were also created based on Cas13a and Cas12a systems. It can be concluded that the fundamental principles of these applications are the specific recognition of nucleic acids and Cas-assisted enzymatic cleavage, combined with genetic recombination and fluorescent imaging. These