Receptor-Mediated Delivery of CRISPR-Cas9 Endonuclease for Cell-Type-Specific Gene Editing

Efficient Direct Cytosolic Protein Delivery via Protein-Linker Co-engineering

Protein therapeutics have enormous potential for transforming the treatment of intracellular cell disorders, such as genetic disorders and cancers. Due to proteins' cell-membrane impermeability, protein-based drugs against intracellular targets require efficient cytosolic delivery strategies; however, none of the current approaches are optimal. Here, we present a simple approach to render proteins membrane-permeable. We use arginine-mimicking ligand N,N'-dimethyl-1,3-propanediamine (DMPA) to functionalize the surface of a few representative proteins, varying in isoelectric point and molecular weight. We show that when these proteins have a sufficient number of these ligands on their surface, they acquire the property of penetrating the cell cytosol. Uptake experiments at 37 and 4 °C indicate that one of the penetration pathways is energy independent, with no evidence of pore formation, with inhibition assays indicating the presence of other uptake pathways. Functional tests demonstrate that the modified proteins maintain their main cellular function; specifically, modified ovalbumin (OVA) leads to enhanced antigen presentation and modified cytochrome C (Cyto C) leads to enhanced cell apoptosis. We modified bovine serum albumin (BSA) with ligands featuring different hydrophobicity and end group charges and showed that, to confer cytosolic penetration, the ligands must be cationic and that some hydrophobic content improves the penetration efficiency. This study provides a simple strategy for efficiently delivering proteins directly to the cell cytosol and offers important insights into the design and development of arginine-rich cell-penetrating peptide mimetic small molecules for protein transduction.

Precisely Targeted Nanoparticles for CRISPR-Cas9 Delivery in Clinical Applications

Clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9 (CRISPR-Cas9), an emerging gene-editing technology, has recently gained rapidly increasing attention. However, the lack of efficient delivery vectors to deliver CRISPR-Cas9 to specific cells or tissues has hindered the translation of this biotechnology into clinical applications. Chemically synthesized nanoparticles (NPs), as attractive non-viral delivery platforms for CRISPR-Cas9, have been extensively investigated because of their unique characteristics, such as controllable size, high stability, multi-functionality, bio-responsive behavior, biocompatibility, and versatility in chemistry. In this review, the key considerations for the precise design of chemically synthesized-based nanoparticles include efficient encapsulation, cellular uptake, the targeting of specific tissues and cells, endosomal escape, and controlled release. We discuss cutting-edge strategies to integrate chemical modifications into non-viral nanoparticles that guide the CRISPR-Cas9 genome-editing machinery to specific edits. We also highlighted the rationale of intelligent nanoparticle design. In particular, we have summarized promising functional groups and molecules that can effectively optimize carrier function. In addition, this review focuses on advances in the widespread application of NPs delivery in the biomedical fields to promote the development of safe, specific, and efficient NPs for delivering CRISPR-Cas9 systems, providing references for accelerating their clinical translational applications.

Hairpin Internal Nuclear Localization Signals in CRISPR-Cas9 Enhance Editing in Primary Human Lymphocytes

The incorporation of nuclear localization signal (NLS) sequences at one or both termini of CRISPR enzymes is a widely adopted strategy to facilitate genome editing. Engineered variants of CRISPR enzymes with diverse NLS sequences have demonstrated superior performance, promoting nuclear localization and efficient DNA editing. However, limiting NLS fusion to the CRISPR protein's termini can negatively impact protein yield via recombinant expression. Here we present a distinct strategy involving the installation of hairpin internal NLS sequences (hiNLS) at rationally selected sites within the backbone of CRISPR-Cas9. We evaluated the performance of these hiNLS Cas9 variants by editing genes in human primary T cells following the delivery of ribonucleoprotein enzymes via either electroporation or co-incubation with amphiphilic peptides. We show that hiNLS Cas9 variants can improve editing efficiency in T cells compared with constructs with terminally fused NLS sequences. Furthermore, many hiNLS Cas9 constructs can be produced with high purity and yield, even when these constructs contain as many as nine NLS. These hiNLS Cas9 constructs represent a key advance in optimizing CRISPR effector design and may contribute to improved editing outcomes in research and therapeutic applications.

Emerging Role of Noncovalent Interactions and Disulfide Bond Formation in the Cellular Uptake of Small Molecules and Proteins

Intracellular delivery of proteins and small molecules is an important barrier in the development of strategies to deliver functional proteins and therapeutics into the cells to realize their full potential in biotechnology, biomedicine, cell-based therapies, and gene editing protein systems. Most of the intracellular protein delivery strategies involve the conjugation of cell penetrating peptides to enable the permeability of plasma membrane of mammalian cells to allow proteins to enter cytosol. The conjugations of small molecules such as (p-methylphenyl) glycine, pyrenebutyrate and cysteines are used for the same purpose. Molecular level interactions are governed mostly by ionic (cationic/anionic), covalent and noncovalent interactions with various molecular entities of glycocalyx matrix on plasma membrane lipid bilayer. Although the role of noncovalent interactions in cellular uptake is not fully understood, several recent advances have focused on the noncovalent interaction-based strategies of intracellular delivery of small molecules and proteins into mammalian cells. These are achieved by simple modification of protein surfaces with chemical moieties which can form noncovalent interactions other than hydrogen bonding. In this review, we describe the recent advances and the mechanistic aspects of intracellular delivery and role of noncovalent interactions in the cellular uptake of proteins and small molecules.

Peptide-enabled ribonucleoprotein delivery for CRISPR engineering (PERC) in primary human immune cells and hematopoietic stem cells

Peptide-enabled ribonucleoprotein delivery for CRISPR engineering (PERC) is a new approach for ex vivo genome editing of primary human cells. PERC uses a single amphiphilic peptide reagent to mediate intracellular delivery of the same pre-formed CRISPR ribonucleoprotein enzymes that are broadly used in research and therapeutics, resulting in high-efficiency editing of stimulated immune cells and cultured hematopoietic stem and progenitor cells (HSPCs). PERC facilitates nuclease-mediated gene knockout, precise transgene knock-in and base editing. The protocol involves mixing the CRISPR ribonucleoprotein enzyme with peptide and then incubating with cultured cells. For efficient transgene knock-in, adeno-associated virus (AAV) homology-directed repair template (HDRT) DNA may be included. In contrast to electroporation, PERC is appealing because it needs no dedicated hardware and has less impact on cell phenotype and viability. Because of the gentle nature of PERC, delivery can be performed multiple times without substantial impact to cell health or phenotype. Editing efficiencies can surpass 90% when using either Cas9 or Cas12a in primary T cells or HSPCs. After 3 h dedicated to reagent preparation, the PERC delivery step can be completed in 1 h, with the associated cell culture steps taking 3-7 d total. Because the protocol calls for only three readily available reagents (protein, RNA and peptide) and does not require dedicated hardware for any step, PERC demands no special expertise and is exceptionally straightforward to adopt. The inherent compatibility of PERC with established cell engineering pipelines makes the protocol appealing for rapid deployment in research and clinical settings.

Dynamic sampling of a surveillance state enables DNA proofreading by Cas9

CRISPR-Cas9 has revolutionized genome engineering applications by programming its single-guide RNA, where high specificity is required. However, the precise molecular mechanism underscoring discrimination between on/off-target DNA sequences, relative to the guide RNA template, remains elusive. Here, using methyl-based NMR to study multiple holoenzymes assembled in vitro, we elucidate a discrete protein conformational state which enables recognition of DNA mismatches at the protospacer adjacent motif (PAM)-distal end. Our results delineate an allosteric pathway connecting a dynamic conformational switch at the REC3 domain, with the sampling of a catalytically competent state by the HNH domain. Our NMR data show that HiFi Cas9 (R691A) increases the fidelity of DNA recognition by stabilizing this "surveillance state" for mismatched substrates, shifting the Cas9 conformational equilibrium away from the active state. These results establish a paradigm of substrate recognition through an allosteric protein-based switch, providing unique insights into the molecular mechanism which governs Cas9 selectivity.

Hepatocyte targeting via the asialoglycoprotein receptor

This review highlights the potential of asialoglycoprotein receptor (ASGPR)-mediated targeting in advancing liver-specific treatments and underscores the ongoing progress in the field. First, we provide a comprehensive examination of the nature of ASGPR ligands, both natural and synthetic. Next, we explore various drug delivery strategies leveraging ASGPR, with a particular emphasis on the delivery of therapeutic nucleic acids such as small interfering RNAs (siRNAs) and antisense oligonucleotides (ASOs). An in-depth analysis of the current status of RNA interference (RNAi) and ASO-based therapeutics is included, detailing approved therapies and those in various stages of clinical development (phases 1 to 3). Afterwards, we give an overview of other ASGPR-targeted conjugates, such as those with peptide nucleic acids or aptamers. Finally, targeted protein degradation of extracellular proteins through ASGPR is briefly discussed.

Nature Inspired Delivery Vehicles for CRISPR-Based Genome Editing

The advent of Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-based genome editing technologies has opened up groundbreaking possibilities for treating a wide spectrum of genetic disorders and diseases. However, the success of these technologies relies heavily on the development of efficient and safe delivery systems. Among the most promising approaches are natural and synthetic nanocarrier-mediated delivery systems, including viral vectors, extracellular vesicles (EVs), engineered cellular membrane particles, liposomes, and various nanoparticles. These carriers enhance the efficacy of the CRISPR system by providing a unique combination of efficiency, specificity, and reduced immunogenicity. Synthetic carriers such as liposomes and nanoparticles facilitate CRISPR delivery with high reproducibility and customizable functions. Viral vectors, renowned for their high transduction efficiency and broad tropism, serve as powerful vehicles for delivering CRISPR components to various cell types. EVs, as natural carriers of RNA and proteins, offer a stealth mechanism to evade immune detection, allowing for the targeted delivery of genome editors with minimal off-target effects. Engineered cellular membrane particles further improve delivery by simulating the cellular environment, enhancing uptake, and minimizing immune response. This review explores the innovative integration of CRISPR genome editors with various nanocarrier systems, focusing on recent advancements, applications, and future directions in therapeutic genome editing.

Rational design of diblock copolymer enables efficient cytosolic protein delivery

Polymer-mediated cytosolic protein delivery demonstrates a promising strategy for the development of protein therapeutics. Here, we propose a new designed diblock copolymer which realizes efficient cytosolic protein delivery both in vitro and in vivo. The polymer contains one protein-binding block composed of phenylboronic acid (PBA) and N-(3-dimethylaminopropyl) (DMAP) pendant units for protein binding and endosomal escape, respectively, followed by the response to ATP enriched in the cytosol which triggers the protein release. The other block is PEG designed to improve particle size control and circulation in vivo. By optimizing the block composition, sequence and length of the copolymer, the optimal one (BP20) was identified with the binding block containing 20 units of both PBA and DMAP, randomly distributed along the chain. When mixed with proteins, the BP20 forms stable nanoparticles and mediates efficient cytosolic delivery of a wide range of proteins including enzymes, toxic proteins and CRISPR/Cas9 ribonucleoproteins (RNP), to various cell lines. The PEG block, especially when further modified with folic acid (FA), enables tumor-targeted delivery of Saporin in vivo, which significantly suppresses the tumor growth. Our results shall inspire the design of novel polymeric vehicles with robust capability for cytosolic protein delivery, which holds great potential for both biological research and therapeutic applications.

Highly efficient CRISPR-mediated genome editing through microfluidic droplet cell mechanoporation

Clustered regularly interspaced short palindromic repeats (CRISPR)-based editing tools have transformed the landscape of genome editing. However, the absence of a robust and safe CRISPR delivery method continues to limit its potential for therapeutic applications. Despite the emergence of various methodologies aimed at addressing this challenge, issues regarding efficiency and editing operations persist. We introduce a microfluidic gene delivery system, called droplet cell pincher (DCP), designed for highly efficient and safe genome editing. This approach combines droplet microfluidics with cell mechanoporation, enabling encapsulation and controlled passage of cells and CRISPR systems through a microscale constriction. Discontinuities created in cell and nuclear membranes upon passage facilitate the rapid CRISPR-system internalization into the nucleus. We demonstrate the successful delivery of various macromolecules, including mRNAs (~98%) and plasmid DNAs (~91%), using this platform, underscoring the versatility of the DCP and leveraging it to achieve successful genome engineering through CRISPR-Cas9 delivery. Our platform outperforms electroporation, the current state-of-the-art method, in three key areas: single knockouts (~6.5-fold), double knockouts (~3.8-fold), and knock-ins (~3.8-fold). These results highlight the potential of our platform as a next-generation tool for CRISPR engineering, with implications for clinical and biological cell-based research.

Peptide-enabled ribonucleoprotein delivery for CRISPR engineering (PERC) in primary human immune cells and hematopoietic stem cells

Peptide-enabled ribonucleoprotein delivery for CRISPR engineering (PERC) is a new approach for ex vivo genome editing of primary human cells. PERC uses a single amphiphilic peptide reagent to mediate intracellular delivery of the same pre-formed CRISPR ribonucleoprotein enzymes that are broadly used in research and therapeutics, resulting in high-efficiency editing of stimulated immune cells and cultured hematopoietic stem and progenitor cells (HSPCs). PERC facilitates nuclease-mediated gene knockout, precise transgene knock-in, and base editing. PERC involves mixing the CRISPR ribonucleoprotein enzyme with peptide and then incubating the formulation with cultured cells. For efficient transgene knock-in, adeno-associated virus (AAV) bearing homology-directed repair template DNA may be included. In contrast to electroporation, PERC is appealing as it requires no dedicated hardware and has less impact on cell phenotype and viability. Due to the gentle nature of PERC, delivery can be performed multiple times without substantial impact to cell health or phenotype. Here we report methods for improved PERC-mediated editing of T cells as well as novel methods for PERC-mediated editing of HSPCs, including knockout and precise knock-in. Editing efficiencies can surpass 90% using either Cas9 or Cas12a in primary T cells or HSPCs. Because PERC calls for only three readily available reagents - protein, RNA, and peptide - and does not require dedicated hardware for any step, PERC demands no special expertise and is exceptionally straightforward to adopt. The inherent compatibility of PERC with established cell engineering pipelines makes this approach appealing for rapid deployment in research and clinical settings.

Towards targeted Cas9 (CRISPR-Cas) delivery: Preparation of IgG antibody-Cas9 conjugates using a split intein

The CRISPR-Cas9 system has revolutionized the field of genetic engineering, but targeted cellular delivery remains a central problem. The delivery of the preformed ribonuclease-protein (RNP) complex has the advantages of fewer side effects and avoidance of potential permanent effects. We reasoned that an internalizing IgG antibody as a targeting device could address the delivery of Cas9-RNP. We opted for protein trans-splicing mediated by a split intein to facilitate posttranslational conjugation of the two large protein entities. We recently described the cysteine-less CL split intein that efficiently performs under oxidizing conditions and does not interfere with disulfide bonds or thiol bioconjugation chemistries. Using the CL split intein, we report for the first time the ligation of monoclonal IgG antibody precursors, expressed in mammalian cells, and a Cas9 precursor, obtained from bacterial expression. A purified IgG-Cas9 conjugate was loaded with sgRNA to form the active RNP complex and introduced a double-strand break in its target DNA in vitro. Furthermore, a synthetic peptide variant of the short N-terminal split intein precursor proved useful for chemical modification of Cas9. The split intein ligation procedure reported here for IgG-Cas9 provides the first step towards a novel CRISPR-Cas9 targeting approach involving the preformed RNP complex.

GalNAc- or Mannose-PEG-Functionalized Polyplexes Enable Effective Lectin-Mediated DNA Delivery

A cationic, dendrimer-like oligo(aminoamide) carrier with four-arm topology based on succinoyl tetraethylene pentamine and histidines, cysteines, and N-terminal azido-lysines was screened for plasmid DNA delivery on various cell lines. The incorporated azides allow modification with various shielding agents of different polyethylene glycol (PEG) lengths and/or different ligands by copper-free click reaction, either before or after polyplex formation. Prefunctionalization was found to be advantageous over postfunctionalization in terms of nanoparticle formation, stability, and efficacy. A length of 24 ethylene oxide repetition units and prefunctionalization of ≥50% of azides per carrier promoted optimal polyplex shielding. PEG shielding resulted in drastically reduced DNA transfer, which could be successfully restored by active lectin targeting via novel GalNAc or mannose ligands, enabling enhanced receptor-mediated endocytosis of the carrier system. The involvement of the asialoglycoprotein receptor (ASGPR) in the uptake of GalNAc-functionalized polyplexes was confirmed in the ASGPR-positive hepatocarcinoma cell lines HepG2 and Huh7. Mannose-modified polyplexes showed superior cellular uptake and transfection efficacy compared to unmodified and shielded polyplexes in mannose-receptor-expressing dendritic cell-like DC2.4 cells.

Targeted nonviral delivery of genome editors in vivo

Cell-type-specific in vivo delivery of genome editing molecules is the next breakthrough that will drive biological discovery and transform the field of cell and gene therapy. Here, we discuss recent advances in the delivery of CRISPR-Cas genome editors either as preassembled ribonucleoproteins or encoded in mRNA. Both strategies avoid pitfalls of viral vector-mediated delivery and offer advantages including transient editor lifetime and potentially streamlined manufacturing capability that are already proving valuable for clinical use. We review current applications and future opportunities of these emerging delivery approaches that could make genome editing more efficacious and accessible in the future.

Minimization of the E. coli ribosome, aided and optimized by community science

The ribosome is a ribonucleoprotein complex found in all domains of life. Its role is to catalyze protein synthesis, the messenger RNA (mRNA)-templated formation of amide bonds between α-amino acid monomers. Amide bond formation occurs within a highly conserved region of the large ribosomal subunit known as the peptidyl transferase center (PTC). Here we describe the step-wise design and characterization of mini-PTC 1.1, a 284-nucleotide RNA that recapitulates many essential features of the Escherichia coli PTC. Mini-PTC 1.1 folds into a PTC-like structure under physiological conditions, even in the absence of r-proteins, and engages small molecule analogs of A- and P-site tRNAs. The sequence of mini-PTC 1.1 differs from the wild type E. coli ribosome at 12 nucleotides that were installed by a cohort of citizen scientists using the on-line video game Eterna. These base changes improve both the secondary structure and tertiary folding of mini-PTC 1.1 as well as its ability to bind small molecule substrate analogs. Here, the combined input from Eterna citizen-scientists and RNA structural analysis provides a robust workflow for the design of a minimal PTC that recapitulates many features of an intact ribosome.

Receptor-Targeted Dual pH-Triggered Intracellular Protein Transfer

Protein therapeutics are of widespread interest due to their successful performance in the current pharmaceutical and medical fields, even though their broad applications have been hindered by the lack of an efficient intracellular delivery approach. Herein, we fabricated an active-targeted dual pH-responsive delivery system with favorable tumor cell entry augmented by extracellular pH-triggered charge reversal and tumor receptor targeting and pH-controlled endosomal release in a traceless fashion. As a traceable model protein, the enhanced green fluorescent protein (eGFP) bearing a nuclear localization signal was covalently coupled with a pH-labile traceless azidomethyl-methylmaleic anhydride (AzMMMan) linker followed by functionalization with different molar equivalents of two dibenzocyclooctyne-octa-arginine-cysteine (DBCO-R8C)-modified moieties: polyethylene glycol (PEG)-GE11 peptide for epidermal growth factor receptor-mediated targeting and melittin for endosomal escape. The cationic melittin domain was masked with tetrahydrophthalic anhydride revertible at mild acidic pH 6.5. At the optimally balanced ratio of functional units, the on-demand charge conversion at tumoral extracellular pH 6.5 in combination with GE11-mediated targeting triggered enhanced electrostatic cellular attraction by the R8C cell-penetrating peptides and melittin, as demonstrated by strongly enhanced cellular uptake. Successful endosomal release followed by nuclear localization of the eGFP cargo was obtained by taking advantage of melittin-mediated endosomal escape and rapid traceless release from the AzMMMan linker. The effectiveness of this multifunctional bioresponsive system suggests a promising strategy for delivery of protein drugs toward intracellular targets. A possible therapeutic relevance was indicated by an example of cytosolic delivery of cytochrome c initiating the apoptosis pathway to kill cancer cells.

Extracellular vesicle-mediated delivery of CRISPR/Cas9 ribonucleoprotein complex targeting proprotein convertase subtilisin-kexin type 9 (Pcsk9) in primary mouse hepatocytes

The loss-of-function of the proprotein convertase subtilisin-kexin type 9 (Pcsk9) gene has been associated with significant reductions in plasma serum low-density lipoprotein cholesterol (LDL-C) levels. Both CRISPR/Cas9 and CRISPR-based editor-mediated Pcsk9 inactivation have successfully lowered plasma LDL-C and PCSK9 levels in preclinical models. Despite the promising preclinical results, these studies did not report how vehicle-mediated CRISPR delivery inactivating Pcsk9 affected low-density lipoprotein receptor recycling in vitro or ex vivo. Extracellular vesicles (EVs) have shown promise as a biocompatible delivery vehicle, and CRISPR/Cas9 ribonucleoprotein (RNP) has been demonstrated to mediate safe genome editing. Therefore, we investigated EV-mediated RNP targeting of the Pcsk9 gene ex vivo in primary mouse hepatocytes. We engineered EVs with the rapamycin-interacting heterodimer FK506-binding protein (FKBP12) to contain its binding partner, the T82L mutant FKBP12-rapamycin binding (FRB) domain, fused to the Cas9 protein. By integrating the vesicular stomatitis virus glycoprotein on the EV membrane, the engineered Cas9 EVs were used for intracellular CRISPR/Cas9 RNP delivery, achieving genome editing with an efficacy of ±28.1% in Cas9 stoplight reporter cells. Administration of Cas9 EVs in mouse hepatocytes successfully inactivated the Pcsk9 gene, leading to a reduction in Pcsk9 mRNA and increased uptake of the low-density lipoprotein receptor and LDL-C. These readouts can be used in future experiments to assess the efficacy of vehicle-mediated delivery of genome editing technologies targeting Pcsk9. The ex vivo data could be a step towards reducing animal testing and serve as a precursor to future in vivo studies for EV-mediated CRISPR/Cas9 RNP delivery targeting Pcsk9.

CRISPR/Cas gene editing and delivery systems for cancer therapy

CRISPR/Cas systems stand out because of simplicity, efficiency, and other superiorities, thus becoming attractive and brilliant gene-editing tools in biomedical field including cancer therapy. CRISPR/Cas systems bring promises for cancer therapy through manipulating and engineering on tumor cells or immune cells. However, there have been concerns about how to overcome the numerous physiological barriers and deliver CRISPR components to target cells efficiently and accurately. In this review, we introduced the mechanisms of CRISPR/Cas systems, summarized the current delivery strategies of CRISPR/Cas systems by physical methods, viral vectors, and nonviral vectors, and presented the current application of CRISPR/Cas systems in cancer clinical treatment. Furthermore, we discussed prospects related to delivery approaches of CRISPR/Cas systems. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Application of the CRISPR/Cas9 Gene Editing Method for Modulating Antibody Fucosylation in CHO Cells

Genetic engineering plays an essential role in the development of cell lines for biopharmaceutical manufacturing. Advanced gene editing tools can improve both the productivity of recombinant cell lines as well as the quality of therapeutic antibodies. Antibody glycosylation is a critical quality attribute for therapeutic biologics because the glycan patterns on the antibody fragment crystallizable (Fc) region can alter its clinical efficacy and safety as a therapeutic drug. As an example, recombinant antibodies derived from Chinese hamster ovary (CHO) cells are generally highly fucosylated; the absence of α1,6-fucose significantly enhances antibody-dependent cell-mediated cytotoxicity (ADCC) against cancer cells. This chapter describes a protocol applying clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated protein 9 (Cas9) approach with different formats to disrupt the α-1,6-fucosyltransferase (FUT8) gene and subsequently inhibit α-1,6 fucosylation on antibodies expressed in CHO cells.

Fire Burn and Cauldron Bubble: What Is in Your Genome Editing Brew?

Genome editing is a rapidly evolving biotechnology with the potential to transform many sectors of industry such as agriculture, biomanufacturing, and medicine. This technology is enabled by an ever-growing portfolio of biomolecular reagents that span the central dogma, from DNA to RNA to protein. In this paper, we draw from our unique perspective as the National Metrology Institute of the United States to bring attention to the importance of understanding and reporting genome editing formulations accurately and promoting concepts to verify successful delivery into cells. Achieving the correct understanding may be hindered by the way units, quantities, and stoichiometries are reported in the field. We highlight the variability in how editing formulations are reported in the literature and examine how a reference molecule could be used to verify the delivery of a reagent into cells. We provide recommendations on how more accurate reporting of editing formulations and more careful verification of the steps in an editing experiment can help set baseline expectations of reagent performance, toward the aim of enabling genome editing studies to be more reproducible. We conclude with a future outlook on technologies that can further our control and enable our understanding of genome editing outcomes at the single-cell level.

Multivalent Targeting of the Asialoglycoprotein Receptor by Virus-Like Particles

The asialoglycoprotein receptor (ASGPR) is expressed in high density on hepatocytes. Multivalent variants of galactosyl carbohydrates bind ASGPR with high affinity, enabling hepatic delivery of ligand-bound cargo. Virus-like particle (VLP) conjugates of a relatively high-affinity ligand were efficiently endocytosed by ASGPR-expressing cells in a manner strongly dependent on the nature and density of ligand display, with the best formulation using a nanomolar-, but not a picomolar-level, binder. Optimized particles were taken up by HepG2 cells with greater efficiency than competing small molecules or the natural multigalactosylated ligand, asialoorosomucoid. Upon systemic injection in mice, these VLPs were rapidly cleared to the liver and were found in association with sinusoidal endothelial cells, Kupffer cells, hepatocytes, dendritic cells, and other immune cells. Both ASGPR-targeted and nontargeted particles were distributed similarly to endothelial and Kupffer cells, but targeted particles were distributed to a greater number and fraction of hepatocytes. Thus, selective cellular trafficking in the liver is difficult to achieve: even with the most potent ASGPR targeting available, barrier cells take up much of the injected particles and hepatocytes are accessed only approximately twice as efficiently in the best case.

Current status and prospect of ZIF-based materials for breast cancer treatment

Breast cancer, one of the three most life-threatening cancers in modern times, must be explored for treatments with low side effects and practical efficacy. Metal organic framework materials (MOFs) is made by metal ions as the center for point and organic ligands as a bridge connecting a new type of porous nano-materials, among them, the zinc base zeolite imidazole skeleton material series (ZIFs) because of its excellent biocompatibility and pH slow controlled release ability, is widely used in the tumor microenvironment in basic research and achieved remarkable curative effect. Inspired by this, in this review, we focus on the recent research progress on the application of ZIFs in the treatment of breast cancer, mainly studying the structure of ZIFs such as ZIF-8, ZIF-90 and ZIF-67 and their application in novel therapies for breast cancer treatment, such as targeted drug delivery, photothermal therapy, immunotherapy and gene therapy.We will more fully demonstrate the potential of zif in breast cancer treatment, hoping to provide an avenue for exploring breast cancer treatment.

Amphipathic Cell-Penetrating Peptide-Aided Delivery of Cas9 RNP for In Vitro Gene Editing and Correction

The therapeutic potential of the CRISPR-Cas9 gene editing system in treating numerous genetic disorders is immense. To fully realize this potential, it is crucial to achieve safe and efficient delivery of CRISPR-Cas9 components into the nuclei of target cells. In this study, we investigated the applicability of the amphipathic cell-penetrating peptide LAH5, previously employed for DNA delivery, in the intracellular delivery of spCas9:sgRNA ribonucleoprotein (RNP) and the RNP/single-stranded homology-directed repair (HDR) template. Our findings reveal that the LAH5 peptide effectively formed nanocomplexes with both RNP and RNP/HDR cargo, and these nanocomplexes demonstrated successful cellular uptake and cargo delivery. The loading of all RNP/HDR components into LAH5 nanocomplexes was confirmed using an electrophoretic mobility shift assay. Functional screening of various ratios of peptide/RNP nanocomplexes was performed on fluorescent reporter cell lines to assess gene editing and HDR-mediated gene correction. Moreover, targeted gene editing of the CCR5 gene was successfully demonstrated across diverse cell lines. This LAH5-based delivery strategy represents a significant advancement toward the development of therapeutic delivery systems for CRISPR-Cas-based genetic engineering in in vitro and ex vivo applications.

A potential paradigm in CRISPR/Cas systems delivery: at the crossroad of microalgal gene editing and algal-mediated nanoparticles

Microalgae as the photosynthetic organisms offer enormous promise in a variety of industries, such as the generation of high-value byproducts, biofuels, pharmaceuticals, environmental remediation, and others. With the rapid advancement of gene editing technology, CRISPR/Cas system has evolved into an effective tool that revolutionised the genetic engineering of microalgae due to its robustness, high target specificity, and programmability. However, due to the lack of robust delivery system, the efficacy of gene editing is significantly impaired, limiting its application in microalgae. Nanomaterials have become a potential delivery platform for CRISPR/Cas systems due to their advantages of precise targeting, high stability, safety, and improved immune system. Notably, algal-mediated nanoparticles (AMNPs), especially the microalgae-derived nanoparticles, are appealing as a sustainable delivery platform because of their biocompatibility and low toxicity in a homologous relationship. In addition, living microalgae demonstrated effective and regulated distribution into specified areas as the biohybrid microrobots. This review extensively summarised the uses of CRISPR/Cas systems in microalgae and the recent developments of nanoparticle-based CRISPR/Cas delivery systems. A systematic description of the properties and uses of AMNPs, microalgae-derived nanoparticles, and microalgae microrobots has also been discussed. Finally, this review highlights the challenges and future research directions for the development of gene-edited microalgae.

Biomaterials-mediated CRISPR/Cas9 delivery: recent challenges and opportunities in gene therapy

The use of biomaterials in delivering CRISPR/Cas9 for gene therapy in infectious diseases holds tremendous potential. This innovative approach combines the advantages of CRISPR/Cas9 with the protective properties of biomaterials, enabling accurate and efficient gene editing while enhancing safety. Biomaterials play a vital role in shielding CRISPR/Cas9 components, such as lipid nanoparticles or viral vectors, from immunological processes and degradation, extending their effectiveness. By utilizing the flexibility of biomaterials, tailored systems can be designed to address specific genetic diseases, paving the way for personalized therapeutics. Furthermore, this delivery method offers promising avenues in combating viral illnesses by precisely modifying pathogen genomes, and reducing their pathogenicity. Biomaterials facilitate site-specific gene modifications, ensuring effective delivery to infected cells while minimizing off-target effects. However, challenges remain, including optimizing delivery efficiency, reducing off-target effects, ensuring long-term safety, and establishing scalable production techniques. Thorough research, pre-clinical investigations, and rigorous safety evaluations are imperative for successful translation from the laboratory to clinical applications. In this review, we discussed how CRISPR/Cas9 delivery using biomaterials revolutionizes gene therapy and infectious disease treatment, offering precise and safe editing capabilities with the potential to significantly improve human health and quality of life.

Bioorthogonal CRISPR/Cas9-Drug Conjugate: A Combinatorial Nanomedicine Platform

Bioconjugation of proteins can substantially expand the opportunities in biopharmaceutical development, however, applications are limited for the gene editing machinery despite its tremendous therapeutic potential. Here, a self-delivered nanomedicine platform based on bioorthogonal CRISPR/Cas9 conjugates, which can be armed with a chemotherapeutic drug for combinatorial therapy is introduced. It is demonstrated that multi-functionalized Cas9 with a drug and polymer can form self-condensed nanocomplexes, and induce significant gene editing upon delivery while avoiding the use of a conventional carrier formulation. It is shown that the nanomedicine platform can be applied for combinatorial therapy by incorporating the anti-cancer drug olaparib and targeting the RAD52 gene, leading to significant anti-tumor effects in BRCA-mutant cancer. The current development provides a versatile nanomedicine platform for combination treatment of human diseases such as cancer.

Synthetic nanoparticles for the delivery of CRISPR/Cas9 gene editing system: classification and biomedical applications

Gene editing has great potential in biomedical research including disease diagnosis and treatment. Clustered regularly interspaced short palindromic repeats (CRISPR) is the most straightforward and cost-effective method. The efficient and precise delivery of CRISPR can impact the specificity and efficacy of gene editing. In recent years, synthetic nanoparticles have been discovered as effective CRISPR/Cas9 delivery vehicles. We categorized synthetic nanoparticles for CRISPR/Cas9 delivery and discribed their advantages and disadvantages. Further, the building blocks of different kinds of nanoparticles and their applications in cells/tissues, cancer and other diseases were described in detail. Finally, the challenges encountered in the clinical application of CRISPR/Cas9 delivery materials were discussed, and potential solutions were provided regarding efficiency and biosafety issues.

Recent Progress of Rational Modified Nanocarriers for Cytosolic Protein Delivery

Therapeutic proteins garnered significant attention in the field of disease treatment. In comparison to small molecule drugs, protein therapies offer distinct advantages, including high potency, specificity, low toxicity, and reduced carcinogenicity, even at minimal concentrations. However, the full potential of protein therapy is limited by inherent challenges such as large molecular size, delicate tertiary structure, and poor membrane penetration, resulting in inefficient intracellular delivery into target cells. To address these challenges and enhance the clinical applications of protein therapies, various protein-loaded nanocarriers with tailored modifications were developed, including liposomes, exosomes, polymeric nanoparticles, and nanomotors. Despite these advancements, many of these strategies encounter significant issues such as entrapment within endosomes, leading to low therapeutic efficiency. In this review, we extensively discussed diverse strategies for the rational design of nanocarriers, aiming to overcome these limitations. Additionally, we presented a forward-looking viewpoint on the innovative generation of delivery systems specifically tailored for protein-based therapies. Our intention was to offer theoretical and technical support for the development and enhancement of nanocarriers capable of facilitating cytosolic protein delivery.

Peptide-mediated delivery of CRISPR enzymes for the efficient editing of primary human lymphocytes

CRISPR-mediated genome editing of primary human lymphocytes is typically carried out via electroporation, which can be cytotoxic, cumbersome and costly. Here we show that the yields of edited primary human lymphocytes can be increased substantially by delivering a CRISPR ribonucleoprotein mixed with an amphiphilic peptide identified through screening. We evaluated the performance of this simple delivery method by knocking out genes in T cells, B cells and natural killer cells via the delivery of Cas9 or Cas12a ribonucleoproteins or an adenine base editor. We also show that peptide-mediated ribonucleoprotein delivery paired with an adeno-associated-virus-mediated homology-directed repair template can introduce a chimaeric antigen receptor gene at the T-cell receptor α constant locus, and that the engineered cells display antitumour potency in mice. The method is minimally perturbative, does not require dedicated hardware, and is compatible with multiplexed editing via sequential delivery, which minimizes the risk of genotoxicity. The peptide-mediated intracellular delivery of ribonucleoproteins may facilitate the manufacturing of engineered T cells.

Cytogel: A Cell-Crosslinked Thermogel

Hydrogels are a three-dimensional network material with a high equilibrium water content where chemical, physical, or biomolecular crosslinking systems have been used for the network formation. In this study, we report a thermosensitive cytogel of lactobionic acid/butanoic acid-conjugated poly(ε-l-lysine) (PKLC4). The thermogelation of the aqueous PKLC4 solution (3.5 wt %) was induced by partial dehydration accompanying a random coil-to-β-sheet transition of the polymer. During the sol-to-gel transition, the modulus increased from <0.05 Pa at <10 °C to 1300-1360 Pa at 37 °C. When HepG2 cells were incorporated into the PKLC4 solution, the gel modulus at 37 °C increased to 2300-2670 Pa. Moreover, the gel modulus was significantly affected by the cell type, population of the HepG2 cells, and live/dead states of the HepG2 cells. The cells proliferate better in the biointeractive PKLC4 thermogel than in the bioinert PEG-PA thermogel. To conclude, by combining thermosensitivity and specific binding of the receptor to the substrate, the hydrogel attained a high modulus without delay in gel time. This study provides new insights into hydrogel preparation in that substrate-receptor binding can be utilized as a crosslinking system to control the hydrogel modulus as well as a design principle for three-dimensional cache that improves cytocompatibility for cells.

Biodegradable silica nanocapsules enable efficient nuclear-targeted delivery of native proteins for cancer therapy

Cell nucleus is the desired subcellular organelle of many therapeutic drugs. Although numerous nanomaterial-based methods have been developed which could facilitate nuclear-targeted delivery of small-molecule drugs, few are known to be capable of delivering exogenous native proteins. Herein, we report a convenient and highly robust approach for effective nuclear-targeted delivery of native proteins/antibodies by using biodegradable silica nanocapsules (BSNPs) that were surface-modified with different nuclear localization signals (NLS) peptides. We found that, upon gaining entry to mammalian cells via endocytosis, such nanocapsules (protein@BSNP-NLS) could effectively escape from endolysosomal vesicles with the assistance of an endosomolytic peptide (i.e., L17E), accumulate in cell nuclei and release the encapsulated protein cargo with biological activities. Cloaked with HeLa cell membrane, DNase@BSNP-NLS/L17E-M (with L17E encapsulated) homologously delivered functional proteins to cancer cell nuclei in tumor-xenografted mice. In vitro and in vivo anti-tumor properties, such as long blood circulation time and effective tumor growth inhibition, indicate that the nuclear-targeted cell-membrane-cloaked BSNPs (DNase@BSNP-NLS/L17E-M) platform is a promising therapeutic approach to nuclear related diseases.

TAxI-peptide targeted Cas12a ribonuclease protein nanoformulations increase genome editing in hippocampal neurons

Gene therapy approaches that utilize Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) ribonucleases have tremendous potential to treat human disease. However, CRISPR therapies delivered by integrating viral vectors are limited by potential off-target genome editing caused by constitutive activation of ribonuclease functions. Thus, biomaterial formulations are being used for the delivery of purified CRISPR components to increase the efficiency and safety of genome editing approaches. We previously demonstrated that a novel peptide identified by phage display, TAxI-peptide, mediates delivery of recombinant proteins into neurons. In this report we utilized NeutrAvidin protein to formulate neuron-targeted genome-editing nanoparticles. Cas12a ribonucleases was loaded with biotinylated guide RNA and biotinylated TAxI-peptide onto NeutrAvidin protein to coordinate the formation a targeted ribonuclease protein (RNP) complex. TAxI-RNP complexes are polydisperse with a 14.3 nm radius. The nanoparticles are stable after formulation and show good stability in the presence of normal mouse serum. TAxI-RNP nanoparticles increased neuronal delivery of Cas12a in reporter mice, resulting in induced tdTomato expression after direct injection into the dentate gyrus of the hippocampus. TAxI-RNP nanoparticles also increased genome editing efficacy in hippocampal neurons versus glia. These studies demonstrate the ability to assemble RNP nanoformulations with NeutrAvidin by binding biotinylated peptides and gRNA-loaded Cas12a ribonucleases into protein nanoparticles that target CRISPR delivery to specific cell-types in vivo. The potential to deliver CRISPR nanoparticles to specific cell-types and control off-target delivery to further reduce deleterious genome editing is essential for the creation of viable therapies to treat nervous system disease.

CRISPR technology: A decade of genome editing is only the beginning

The advent of clustered regularly interspaced short palindromic repeat (CRISPR) genome editing, coupled with advances in computing and imaging capabilities, has initiated a new era in which genetic diseases and individual disease susceptibilities are both predictable and actionable. Likewise, genes responsible for plant traits can be identified and altered quickly, transforming the pace of agricultural research and plant breeding. In this Review, we discuss the current state of CRISPR-mediated genetic manipulation in human cells, animals, and plants along with relevant successes and challenges and present a roadmap for the future of this technology.

Directing the Way-Receptor and Chemical Targeting Strategies for Nucleic Acid Delivery

Nucleic acid therapeutics have shown great potential for the treatment of numerous diseases, such as genetic disorders, cancer and infections. Moreover, they have been successfully used as vaccines during the COVID-19 pandemic. In order to unfold full therapeutical potential, these nano agents have to overcome several barriers. Therefore, directed transport to specific tissues and cell types remains a central challenge to receive carrier systems with enhanced efficiency and desired biodistribution profiles. Active targeting strategies include receptor-targeting, mediating cellular uptake based on ligand-receptor interactions, and chemical targeting, enabling cell-specific delivery as a consequence of chemically and structurally modified carriers. With a focus on synthetic delivery systems including polyplexes, lipid-based systems such as lipoplexes and lipid nanoparticles, and direct conjugates optimized for various types of nucleic acids (DNA, mRNA, siRNA, miRNA, oligonucleotides), we highlight recent achievements, exemplified by several nucleic acid drugs on the market, and discuss challenges for targeted delivery to different organs such as brain, eye, liver, lung, spleen and muscle in vivo.

Folate Receptor-Mediated Delivery of Cas9 RNP for Enhanced Immune Checkpoint Disruption in Cancer Cells

The clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) system offers great opportunities for the treatment of numerous diseases by precise modification of the genome. The functional unit of the system is represented by Cas9/sgRNA ribonucleoproteins (RNP), which mediate sequence-specific cleavage of DNA. For therapeutic applications, efficient and cell-specific transport into target cells is essential. Here, Cas9 RNP nanocarriers are described, which are based on lipid-modified oligoamino amides and folic acid (FolA)-PEG to realize receptor-mediated uptake and gene editing in cancer cells. In vitro studies confirm strongly enhanced potency of receptor-mediated delivery, and the nanocarriers enable efficient knockout of GFP and two immune checkpoint genes, PD-L1 and PVR, at low nanomolar concentrations. Compared with non-targeted nanoparticles, FolA-modified nanocarriers achieve substantially higher gene editing including dual PD-L1/PVR gene disruption after injection into CT26 tumors in vivo. In the syngeneic mouse model, dual disruption of PD-L1 and PVR leads to CD8+ T cell recruitment and distinct CT26 tumor growth inhibition, clearly superior to the individual knockouts alone. The reported Cas9 RNP nanocarriers represent a versatile platform for potent and receptor-specific gene editing. In addition, the study demonstrates a promising strategy for cancer immunotherapy by permanent and combined immune checkpoint disruption.

CRISPR Spherical Nucleic Acids

The use of CRISPR/Cas9 systems in genome editing has been limited by the inability to efficiently deliver the key editing components to and across tissues and cell membranes, respectively. Spherical nucleic acids (SNAs) are nanostructures that provide privileged access to both but have yet to be explored as a means of facilitating gene editing. Herein, a new class of CRISPR SNAs are designed and evaluated in the context of genome editing. Specifically, Cas9 ProSNAs comprised of Cas9 cores densely modified with DNA on their exteriors and preloaded with single-guide RNA were synthesized and evaluated for their genome editing capabilities in the context of multiple cell lines. The radial orientation of the DNA on the Cas9 protein surface enhances cellular uptake, without the need for electroporation or transfection agents. In addition, the Cas9 proteins defining the cores of the ProSNAs were fused with GALA peptides on their N-termini and nuclear localization signals on their C-termini to facilitate endosomal escape and maximize nuclear localization and editing efficiency, respectively. These constructs were stable against protease digestion under conditions that fully degrade the Cas9 protein, when not transformed into an SNA, and used to achieve genome editing efficiency between 32 and 47%. Taken together, these novel constructs and advances point toward a way of significantly broadening the scope of use and impact of CRISPR-Cas9 genome editing systems.

A novel dual-targeting delivery system for specific delivery of CRISPR/Cas9 using hyaluronic acid, chitosan and AS1411

A facile method was designed that can specifically deliver CRISPR/Cas9 into target cells nuclei and reduce the off-target effects. A multifunctional delivery vector for FOXM1 knockout was composed by integration of cell targeting polymer (hyaluronic acid) and cell and nuclear targeting group (AS1411 aptamer) on the surface of nanoparticles formed by genome editing plasmid and chitosan (CS) as the core (Apt-HA-CS-CRISPR/Cas9). The data of cytotoxicity experiment and western blot confirmed this issue. The results of flow cytometry analysis and fluorescence imaging demonstrated that Apt-HA-CS-CRISPR/Cas9 was significantly internalized into target cells (MCF-7, SK-MES-1, HeLa) but not into nontarget cells (HEK293). Furthermore, the in vivo studies displayed that the Apt-HA-CS-CRISPR/Cas9 was strongly rendered tumor inhibitory effect and delivered efficiently CRISPR/Cas9 into the tumor with no detectable distribution in other organs compared with naked plasmid. This approach provides an avenue for specific in vivo gene editing therapeutics with the lowest side effect.

Development of non-viral vectors for neuronal-targeted delivery of CRISPR-Cas9 RNA-proteins as a therapeutic strategy for neurological disorders

The aging population contributes to an increase in the prevalence of neurodegenerative diseases, such as Parkinson's disease (PD). Due to the progressive nature of these diseases and an incomplete understanding of their pathophysiology, current drugs are inefficient, with a limited efficacy and major side effects. In this study, CRISPR-Cas9 RNA-proteins (RNP) composed of a Cas9 nuclease and single-guide RNA were delivered with a non-viral targeted delivery system to rescue the PD-associated phenotype in neuronal cells. Here, we fused the cell-penetrating amphipathic peptide, PepFect14 (PF14), with a short fragment of the rabies virus glycoprotein (C2) previously shown to have an affinity towards nicotinic acetylcholine receptors expressed on neuronal cells and on the blood-brain barrier. The resultant peptide, C2-PF14, was used to complex with and deliver RNPs to neuronal cells. We observed that RNP/C2-PF14 complexes formed nanosized, monodispersed, and nontoxic nanoparticles that led to a specific delivery into neuronal cells. α-Synuclein (α-syn) plays a major role in the pathology of PD and is considered to be a target for therapy. We demonstrated that CRISPR/Cas9 RNP delivered by C2-PF14 achieved α-syn gene (SNCA) editing in neuronal cells as determined by T7EI assay and western blotting. Furthermore, RNP/C2-PF14 relieved PD-associated toxicity in neuronal cells in vitro. This is a proof-of-concept towards simple and safe targeted genome-editing for treating PD and other neurological disorders.

Closing the Door with CRISPR: Genome Editing of CCR5 and CXCR4 as a Potential Curative Solution for HIV

Human immunodeficiency virus (HIV) infection can be controlled by anti-retroviral therapy. Suppressing viral replication relies on life-long medication, but anti-retroviral therapy is not without risks to the patient. Therefore, it is important that permanent cures for HIV infection are developed. Three patients have been described to be completely cured from HIV infection in recent years. In all cases, patients received a hematopoietic stem cell (HSC) transplantation due to a hematological malignancy. The HSCs were sourced from autologous donors that expressed a homozygous mutation in the CCR5 gene. This mutation results in a non-functional receptor, and confers resistance to CCR5-tropic HIV strains that rely on CCR5 to enter host cells. The Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/CRISPR-associated (Cas) system is one of the methods of choice for gene editing, and the CRISPR/Cas system has been employed to target loci of interest in the context of HIV. Here, the current literature regarding CRISPR-mediated genome editing to render cells resistant to HIV (re)-infection by knocking out the co-receptors CCR5 and CXCR4 is summarized, and an outlook is provided regarding future (research) directions.

Preparation of Cas9 Ribonucleoproteins for Genome Editing

Genome editing by the delivery of pre-assembled Cas9 ribonucleoproteins (Cas9 RNP) is an increasingly popular approach for cell types that are difficult to manipulate genetically by the conventional plasmid and viral methods. Cas9 RNP editing is robust, precise, capable of multiplexing, and free of genetic materials. Its transient presence in cells limits residual editing activity. This protocol describes the preparation of recombinant Streptococcus pyogenes Cas9 (SpCas9) protein by heterologous expression and purification from Escherichia coli, and the synthesis of CRISPR guide RNA by in vitro transcription and PAGE purification. SpCas9 is the first CRISPR Cas9 discovered ( Jinek et al., 2012 ) and is also one of the most characterized Cas enzymes for genome editing applications. Using this formulation of Cas9 RNP, we have demonstrated highly efficient genome editing in primary human T and natural killer (NK) cells by electroporation, and in fungi and plants by polyethylene glycol-mediated transformation. Our protocol of Cas9 RNP preparation is consistent and straightforward to adopt for genome editing in other cell types and organisms. Graphical abstract.

Carrier strategies boost the application of CRISPR/Cas system in gene therapy

Emerging clustered regularly interspaced short palindromic repeat/associated protein (CRISPR/Cas) genome editing technology shows great potential in gene therapy. However, proteins and nucleic acids suffer from enzymatic degradation in the physiological environment and low permeability into cells. Exploiting carriers to protect the CRISPR system from degradation, enhance its targeting of specific tissues and cells, and reduce its immunogenicity is essential to stimulate its clinical applications. Here, the authors review the state-of-the-art CRISPR delivery systems and their applications, and describe strategies to improve the safety and efficacy of CRISPR mediated genome editing, categorized by three types of cargo formats, that is, Cas: single-guide RNA ribonucleoprotein, Cas mRNA and single-guide RNA, and Cas plasmid expressing CRISPR/Cas systems. The authors hope this review will help develop safe and efficient nanomaterial-based carriers for CRISPR tools.

Rapid Assessment of CRISPR Transfection Efficiency and Enrichment of CRISPR Induced Mutations Using a Dual-Fluorescent Stable Reporter System

The nuclease activity of the CRISPR-Cas9 system relies on the delivery of a CRISPR-associated protein 9 (Cas9) and a single guide RNA (sgRNA) against the target gene. CRISPR components are typically delivered to cells as either a Cas9/sgRNA ribonucleoprotein (RNP) complex or a plasmid encoding a Cas9 protein along with a sequence-specific sgRNA. Multiple transfection reagents are known to deliver CRISPR-Cas9 components, and delivery vectors are being developed for different purposes by several groups. Here, we repurposed a dual-fluorescence (RFP-GFP-GFP) reporter system to quantify the uptake level of the functional CRISPR-Cas9 components into cells and compare the efficiency of CRISPR delivery vectors. Using this system, we developed a novel and rapid cell-based microplate reader assay that makes possible real-time, rapid, and high throughput quantification of CRISPR nuclease activity. Cells stably expressing this dual-fluorescent reporter construct facilitated a direct quantification of the level of the internalized and functional CRISPR-Cas9 molecules into the cells without the need of co-transfecting fluorescently labeled reporter molecules. Additionally, targeting a reporter gene integrated into the genome recapitulates endogenous gene targeting. Thus, this reporter could be used to optimize various transfection conditions of CRISPR components, to evaluate and compare the efficiency of transfection agents, and to enrich cells containing desired CRISPR-induced mutations.

Targeted intracellular delivery of Cas13 and Cas9 nucleases using bacterial toxin-based platforms

Targeted delivery of therapeutic proteins toward specific cells and across cell membranes remains major challenges. Here, we develop protein-based delivery systems utilizing detoxified single-chain bacterial toxins such as diphtheria toxin (DT) and botulinum neurotoxin (BoNT)-like toxin, BoNT/X, as carriers. The system can deliver large protein cargoes including Cas13a, CasRx, Cas9, and Cre recombinase into cells in a receptor-dependent manner, although delivery of ribonucleoproteins containing guide RNAs is not successful. Delivery of Cas13a and CasRx, together with guide RNA expression, reduces mRNAs encoding GFP, SARS-CoV-2 fragments, and endogenous proteins PPIB, KRAS, and CXCR4 in multiple cell lines. Delivery of Cre recombinase modifies the reporter loci in cells. Delivery of Cas9, together with guide RNA expression, generates mutations at the targeted genomic sites in cell lines and induced pluripotent stem cell (iPSC)-derived human neurons. These findings establish modular delivery systems based on single-chain bacterial toxins for delivery of membrane-impermeable therapeutics into targeted cells.

Tricyclic cell-penetrating peptides for efficient delivery of functional antibodies into cancer cells

The intracellular environment hosts a large number of cancer- and other disease-relevant human proteins. Targeting these with internalized antibodies would allow therapeutic modulation of hitherto undruggable pathways, such as those mediated by protein-protein interactions. However, one of the major obstacles in intracellular targeting is the entrapment of biomacromolecules in the endosome. Here we report an approach to delivering antibodies and antibody fragments into the cytosol and nucleus of cells using trimeric cell-penetrating peptides (CPPs). Four trimers, based on linear and cyclic sequences of the archetypal CPP Tat, are significantly more potent than monomers and can be tuned to function by direct interaction with the plasma membrane or escape from vesicle-like bodies. These studies identify a tricyclic Tat construct that enables intracellular delivery of functional immunoglobulin-G antibodies and Fab fragments that bind intracellular targets in the cytosol and nuclei of live cells at effective concentrations as low as 1 μM.

Smart Strategies for Precise Delivery of CRISPR/Cas9 in Genome Editing

The emergence of CRISPR/Cas technology has enabled scientists to precisely edit genomic DNA sequences. This approach can be used to modulate gene expression for the treatment of genetic disorders and incurable diseases such as cancer. This potent genome-editing tool is based on a single guide RNA (sgRNA) strand that recognizes the targeted DNA, plus a Cas nuclease protein for binding and processing the target. CRISPR/Cas has great potential for editing many genes in different types of cells and organisms both in vitro and in vivo. Despite these remarkable advances, the risk of off-target effects has hindered the translation of CRISPR/Cas technology into clinical applications. To overcome this hurdle, researchers have devised gene regulatory systems that can be controlled in a spatiotemporal manner, by designing special sgRNA, Cas, and CRISPR/Cas delivery vehicles that are responsive to different stimuli, such as temperature, light, magnetic fields, ultrasound (US), pH, redox, and enzymatic activity. These systems can even respond to dual or multiple stimuli simultaneously, thereby providing superior spatial and temporal control over CRISPR/Cas gene editing. Herein, we summarize the latest advances on smart sgRNA, Cas, and CRISPR/Cas nanocarriers, categorized according to their stimulus type (physical, chemical, or biological).

Antibody-mediated delivery of CRISPR-Cas9 ribonucleoproteins in human cells

The CRISPR genome editing technology holds great clinical potential for the treatment of monogenetic disorders such as sickle cell disease. The therapeutic in vivo application of the technology relies on targeted delivery methods of the Cas9 and gRNA complex to specific cells or tissues. However, such methods are currently limited to direct organ delivery, preventing clinical application. Here, we show that monoclonal antibodies can be employed to deliver the Cas9/gRNA complex directly into human cells via cell-surface receptors. Using the SpyCatcher/SpyTag system, we conjugated the Fab fragment of the therapeutic antibodies Trastuzumab and Pertuzumab directly to the Cas9 enzyme and observed HER2-specific uptake of the ribonucleoprotein in a human HER2 expressing cell line. Following cellular uptake in the presence of an endosomolytic peptide, modest gene editing was also observed. This finding provides a blueprint for the targeted delivery of the CRISPR technology into specific cells using monoclonal antibodies.

Tailoring Hyperbranched Poly(β-amino ester) as a Robust and Universal Platform for Cytosolic Protein Delivery

Cytosolic protein delivery is a prerequisite for protein-based biotechnologies and therapeutics on intracellular targets. Polymers that can complex with proteins to form nano-assemblies represent one of the most important categories of materials, because of the ease of nano-fabrication, high protein loading efficiency, no need for purification, and maintenance of protein bioactivity. Stable protein encapsulation and efficient intracellular liberation are two critical yet opposite processes toward cytosolic delivery, and polymers that can resolve these two conflicting challenges are still lacking. Herein, hyperbranched poly(β-amino ester) (HPAE) with backbone-embedded phenylboronic acid (PBA) is developed to synchronize these two processes, wherein PBA enhanced protein encapsulation via nitrogen-boronate (N-B) coordination while triggered polymer degradation and protein release upon oxidation by H₂ O₂ in cancer cells. Upon optimization of the branching degree, charge density, and PBA distribution, the best-performing A2-B3-C2-S₂ -P₂ is identified, which mediates robust delivery of various native proteins/peptides with distinct molecular weights (1.6-430 kDa) and isoelectric points (4.1-10.3) into cancer cells, including enzymes, toxins, antibodies, and CRISPR-Cas9 ribonucleoproteins (RNPs). Moreover, A2-B3-C2-S₂ -P₂ mediates effective cytosolic delivery of saporin both in vitro and in vivo to provoke remarkable anti-tumor efficacy. Such a potent and universal platform holds transformative potentials for protein pharmaceuticals.

New approaches to moderate CRISPR-Cas9 activity: Addressing issues of cellular uptake and endosomal escape

CRISPR-Cas9 is rapidly entering molecular biology and biomedicine as a promising gene-editing tool. A unique feature of CRISPR-Cas9 is a single-guide RNA directing a Cas9 nuclease toward its genomic target. Herein, we highlight new approaches for improving cellular uptake and endosomal escape of CRISPR-Cas9. As opposed to other recently published works, this review is focused on non-viral carriers as a means to facilitate the cellular uptake of CRISPR-Cas9 through endocytosis. The majority of non-viral carriers, such as gold nanoparticles, polymer nanoparticles, lipid nanoparticles, and nanoscale zeolitic imidazole frameworks, is developed with a focus toward optimizing the endosomal escape of CRISPR-Cas9 by taking advantage of the acidic environment in the late endosomes. Among the most broadly used methods for in vitro and ex vivo ribonucleotide protein transfection are electroporation and microinjection. Thus, other delivery formats are warranted for in vivo delivery of CRISPR-Cas9. Herein, we specifically revise the use of peptide and nanoparticle-based systems as platforms for CRISPR-Cas9 delivery in vivo. Finally, we highlight future perspectives of the CRISPR-Cas9 gene-editing tool and the prospects of using non-viral vectors to improve its bioavailability and therapeutic potential.