Involvement of Ca²⁺ and ATP in enhanced gene delivery by bubble liposomes and ultrasound exposure

Carrier-Free Cellular Transport of CRISPR/Cas9 Ribonucleoprotein for Genome Editing by Cold Atmospheric Plasma

Simple Summary

CRISPR/Cas9 system as a potential gene editing platform has been widely applied in biological engineering and disease therapies. To achieve precise gene targeting, active CRISPR/Cas9 components must be efficiently transported to targeted cells. As a simple and effective strategy, Cold Atmospheric Plasma (CAP) treatment has been demonstrated for the transmembrane delivery of various exogenous materials. In comparison with carrier-dependent delivery methods, this carrier-free platform provides a promising alternative to circumvent the obstacles of biosafety and complicated preparation processes. In this work, a CAP-based CRISPR/Cas9 carrier-free delivery platform has been established and corresponding mechanism related to efficient transportation has been explored. Briefly, the efficient production of bioactive species in culture media after CAP treatment alters cell membrane potential and permeability, which facilitates cytosolic delivery of active CRISPR/Cas9 components via passive diffusion and ATP-dependent endocytosis pathways, resulting in efficient genome editing and gene silencing. This carrier-free strategy using CAP-based transportation may also be extended to other active biomolecules in drug delivery and gene therapy.

Abstract

A carrier-free CRISPR/Cas9 ribonucleoprotein delivery strategy for genome editing mediated by a cold atmospheric plasma (CAP) is described. The CAP is promising in many biomedical applications due to efficient production of bioactive ionized species. The MCF-7 cancer cells after CAP exposure exhibit increased extracellular reactive oxygen and nitrogen species (RONS) and altered membrane potential and permeability. Hence, transmembrane transport of Ca²⁺ into the cells increases and accelerates ATP hydrolysis, resulting in enhanced ATP-dependent endocytosis. Afterwards, the increased Ca²⁺ and ATP contents promote the release of cargo into cytoplasm due to the enhanced endosomal escape. The increased membrane permeability also facilitates passive diffusion of foreign species across the membrane into the cytosol. After CAP exposure, the MCF-7 cells incubated with Cas9 ribonucleoprotein (Cas9-sgRNA complex, Cas9sg) with a size of about 15 nm show 88.9% uptake efficiency and 65.9% nuclear import efficiency via passive diffusion and ATP-dependent endocytosis pathways. The efficient transportation of active Cas9sg after the CAP treatment leads to 21.7% and 30.2% indel efficiencies in HEK293T and MCF-7 cells, respectively. This CAP-mediated transportation process provides a simple and robust alternative for the delivery of active CRISPR/Cas9 ribonucleoprotein. Additionally, the technique can be extended to other macro-biomolecules and nanomaterials to cater to different biomedical applications.

Non-viral nanoparticles for RNA interference: Principles of design and practical guidelines

Ribonucleic acid interference (RNAi) is an innovative treatment strategy for a myriad of indications. Non-viral synthetic nanoparticles (NPs) have drawn extensive attention as vectors for RNAi due to their potential advantages, including improved safety, high delivery efficiency and economic feasibility. However, the complex natural process of RNAi and the susceptible nature of oligonucleotides render the NPs subject to particular design principles and requirements for practical fabrication. Here, we summarize the requirements and obstacles for fabricating non-viral nano-vectors for efficient RNAi. To address the delivery challenges, we discuss practical guidelines for materials selection and NP synthesis in order to maximize RNA encapsulation efficiency and protection against degradation, and to facilitate the cytosolic release of oligonucleotides. The current status of clinical translation of RNAi-based therapies and further perspectives for reducing the potential side effects are also reviewed.

Laminin-derived peptides: Applications in drug delivery systems for targeting

Recently, the development of drug delivery systems (DDSs) for clinical application of anticancer drugs and gene therapy has rapidly progressed. In particular, DDS carriers used for chemotherapy and gene therapy are required to selectively deliver drugs and genes to cancer cells. Both the carrier and the molecule must in combination be highly selective in most cases. Possible candidate targeting molecules are the laminins, major basement membrane proteins that interact with various cells through their multiple constituent active peptide sequences. Laminin-derived peptides bind to various cellular receptors and have been used for DDSs as a targeting moiety. Here, we review the progress in laminin-derived peptide-conjugated DDSs. Drug and gene carriers as well as ultrasound diagnostic contrast agents utilizing laminin-derived peptides for selective targeting are useful components of DDSs and play important roles in cancer and in the neovasculature.

Reversible Covalent Cross-Linked Polycations with Enhanced Stability and ATP-Responsive Behavior for Improved siRNA Delivery

Cationic polyplex as commonly used nucleic acid carriers faced several shortcomings, such as high cytotoxicity, low serum stability, and slow cargo release at the target site. The traditional solution is covering a negative charged layer (e.g., hyaluronic acid, HA) via electrostatic interaction. However, it was far from satisfactory for the deshielding by physiological anions in circulation (e.g., serum proteins, phosphate). In this study, we proposed a new strategy of reversible covalent cross-linking to enhance stability in circulation and enable stimuli-disassembly of polyplexes in tumor cells. Here, 25k polyethylenimine (PEI) was chosen as model polycations for veriying the hypothesis. HA-PEI conjugation was formed by the cross-linking of adenosine triphosphate grafted HA (HA-ATP) with phenylboronic acid grafted PEI (PEI-PBA) via the chemical reaction between PBA and ATP. Compared with noncovalent polyplex by electrostatic interaction (HA/PEI), HA-PEI exhibited much better colloidal stability and serum stability. The covered HA-ATP layer on PEI-PBA could maintain stable in the absence of physiological anions, while HA layer on PEI in HA/PEI group showed obvious detachment after anion's competition. More importantly, the covalent cross-linking polyplex could selectively release siRNA in the ATP rich environment of cytosol and significantly improve siRNA silence. Besides, the covalent cross-linking with HA-ATP could effectively reduce the cytotoxicity of cationic polyplex, improve the uptake by B61F10 cells and promote the endosomal escape. Consequently, this strategy of HA-PEI conjugation significantly enhanced the siRNA transfection in the absence or presence of FBS (fetal bovine serum) on B16F10 cells and CHO cells. Taken together, the reversible covalent cross-linking approach shows obvious superiority compared with the noncovalent absorption strategy. It held great potential to be developed to polish up the performance of cationic polyplex on reducing the toxicity, enhancing the serum tolerance and achieving controlled release of siRNA at target site.

Nonviral gene delivery systems by the combination of bubble liposomes and ultrasound

The combination of therapeutic ultrasound (US) and nano/microbubbles is an important system for establishing a novel and noninvasive gene delivery system. Genes are delivered more efficiently using this system compared with a conventional nonviral vector system such as the lipofection method, resulting in higher gene expression. This higher efficiency is due to the gene being delivered into the cytosol and bypassing the endocytosis pathway. Many in vivo studies have demonstrated US-mediated gene delivery with nano/microbubbles, and several gene therapy feasibility studies for various diseases have been reported. In addition, nano/microbubbles can deliver genes site specifically by the control of US exposure site. In the present review, we summarize the gene delivery systems by the combination of nano/microbubbles and US, describe their properties, and assess applications and challenges of US theranostics.

Polymer-coated echogenic lipid nanoparticles with dual release triggers

Although lipid nanoparticles are promising drug delivery vehicles, passive release of encapsulated contents at the target site is often slow. Herein, we report contents release from targeted, polymer-coated, echogenic lipid nanoparticles in the cell cytoplasm by redox trigger and simultaneously enhanced by diagnostic frequency ultrasound. The lipid nanoparticles were polymerized on the external leaflet using a disulfide cross-linker. In the presence of cytosolic concentrations of glutathione, the lipid nanoparticles released 76% of encapsulated contents. Plasma concentrations of glutathione failed to release the encapsulated contents. Application of 3 MHz ultrasound for 2 min simultaneously with the reducing agent enhanced the release to 96%. Folic acid conjugated, doxorubicin-loaded nanoparticles showed enhanced uptake and higher cytotoxicity in cancer cells overexpressing the folate receptor (compared to the control). With further developments, these lipid nanoparticles have the potential to be used as multimodal nanocarriers for simultaneous targeted drug delivery and ultrasound imaging.

Ultrasound enhanced matrix metalloproteinase-9 triggered release of contents from echogenic liposomes

The extracellular enzyme matrix metalloproteinase-9 (MMP-9) is overexpressed in atherosclerotic plaques and in metastatic cancers. The enzyme is responsible for rupture of the plaques and for the invasion and metastasis of a large number of cancers. The ability of ultrasonic excitation to induce thermal and mechanical effects has been used to release drugs from different carriers. However, the majority of these studies were performed with low frequency ultrasound (LFUS) at kilohertz frequencies. Clinical usage of LFUS excitations will be limited due to harmful biological effects. Herein, we report our results on the release of encapsulated contents from substrate lipopeptide incorporated echogenic liposomes triggered by recombinant human MMP-9. The contents release was further enhanced by the application of diagnostic frequency (3 MHz) ultrasound. The echogenic liposomes were successfully imaged employing a medical ultrasound transducer (4-15 MHz). The conditioned cell culture media from cancer cells (secreting MMP-9) released the encapsulated dye from the liposomes (30-50%), and this release is also increased (50-80%) by applying diagnostic frequency ultrasound (3 MHz) for 3 min. With further developments, these liposomes have the potential to serve as multimodal carriers for triggered release and simultaneous ultrasound imaging.