Chemical Modification of Proteins and Their Intracellular Delivery Using Lipidoid Nanoparticles.

Protein-based therapeutics are a class of drugs considered to be one of most safe and straightforward approaches for manipulating cell function and treating diseases. However, in contrast to traditional small-molecule drugs, most protein drugs cannot easily pass through biological membrane barriers due to their large size and surface chemistry. Consequently, most of the current FDA approved protein pharmaceuticals target secreted domains or cell surface-bound receptors, for which the drug does not need to pass through the cell membrane. Effective delivery systems that can transport functionally intact protein molecules to their intracellular targets can contribute to further expanding the therapeutic modalities of protein-based drugs. Furthermore, proteins themselves can be engineered, either to facilitate their interaction with the delivery system, or to improve their specificity and efficacy upon intracellular delivery. Both physical and biochemical methods have been developed for intracellular protein delivery and each strategy has its own advantages and drawbacks. We describe here the methods of chemical modification of therapeutic proteins in combination of the lipid-like molecules or lipidoids to enhance their intracellular delivery efficiency.

In situ cancer vaccination using lipidoid nanoparticles.

In situ vaccination is a promising strategy for cancer immunotherapy owing to its convenience and the ability to induce numerous tumor antigens. However, the advancement of in situ vaccination techniques has been hindered by low cross-presentation of tumor antigens and the immunosuppressive tumor microenvironment. To balance the safety and efficacy of in situ vaccination, we designed a lipidoid nanoparticle (LNP) to achieve simultaneously enhancing cross-presentation and STING activation. From combinatorial library screening, we identified 93-O17S-F, which promotes both the cross-presentation of tumor antigens and the intracellular delivery of cGAMP (STING agonist). Intratumor injection of 93-O17S-F/cGAMP in combination with pretreatment with doxorubicin exhibited excellent antitumor efficacy, with 35% of mice exhibiting total recovery from a primary B16F10 tumor and 71% of mice with a complete recovery from a subsequent challenge, indicating the induction of an immune memory against the tumor. This study provides a promising strategy for in situ cancer vaccination.

Lipid nanoparticle-mediated codelivery of Cas9 mRNA and single-guide RNA achieves liver-specific in vivo genome editing of Angptl3.

Loss-of-function mutations in Angiopoietin-like 3 (Angptl3) are associated with lowered blood lipid levels, making Angptl3 an attractive therapeutic target for the treatment of human lipoprotein metabolism disorders. In this study, we developed a lipid nanoparticle delivery platform carrying Cas9 messenger RNA (mRNA) and guide RNA for CRISPR-Cas9-based genome editing of Angptl3 in vivo. This system mediated specific and efficient Angptl3 gene knockdown in the liver of wild-type C57BL/6 mice, resulting in profound reductions in serum ANGPTL3 protein, low density lipoprotein cholesterol, and triglyceride levels. Our delivery platform is significantly more efficient than the FDA-approved MC-3 LNP, the current gold standard. No evidence of off-target mutagenesis was detected at any of the nine top-predicted sites, and no evidence of toxicity was detected in the liver. Importantly, the therapeutic effect of genome editing was stable for at least 100 d after a single dose administration. This study highlights the potential of LNP-mediated delivery as a specific, effective, and safe platform for Cas9-based therapeutics.

mRNA Delivery Using Bioreducible Lipidoid Nanoparticles Facilitates Neural Differentiation of Human Mesenchymal Stem Cells.

Mesenchymal stem cells (MSCs) are widely used in regenerative medicine and tissue engineering and delivering biological molecules into MSCs has been used to control stem cell behavior. However, the efficient delivery of large biomolecules such as DNA, RNA, and proteins into MSCs using nonviral delivery strategies remains an ongoing challenge. Herein, nanoparticles composed of cationic bioreducible lipid-like materials (lipidoids) are developed to intracellularly deliver mRNA into human mesenchymal stem cells (hMSCs). The delivery efficacy to hMSCs is improved by adding three excipients including cholesterol, 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-polyethylene glycol (DSPE-PEG) during lipidoid nanoparticle formulation. Using an optimized lipidoid formulation, Cas9 mRNA and single guide RNA (sgRNA) targeting neuron restrictive silencing factor (NRSF) are delivered to hMSCs, leading to successful neural-like differentiation as demonstrated by the expression of synaptophysin (SYP), brain-derived neurotrophic factor (BDNF), neuron-specific enolase (NSE), and neuron-specific growth-associated protein (SCG10). Overall, a synthetic lipid formulation that can efficiently deliver mRNA to hMSCs is identified, leading to CRISPR-based gene knockdown to facilitate hMSCs transdifferentiation into neural-like lineage.

Enhanced protein degradation by intracellular delivery of pre-fused PROTACs using lipid-like nanoparticles.

Proteolysis-targeting chimaera (PROTAC) technology is an emerging approach for achieving targeted degradation of a protein of interest (POI) intracellularly. However, the cell permeability of PROTACs is limited by their high molecular weight and total polar surface area. Moreover, the activation of the proteasome-mediated degradation by PROTAC requires the formation of a ternary (three-component) complex, composed of the PROTAC, the POIs, and E3-ligases related proteins (E3Ps). Simplifying the three-component system to two-component system could theoretically increase the efficiency of the formation of ternary complex and enhance the protein degradation efficiency. Herein, we demonstrate that pre-fusion of PROTACs with E3Ps (called "pre-fused PROTACs") before administration could transform the original PROTAC system to two-component system. After delivery by lipid nanoparticles, the degradation of POI by pre-fused PROTACs was dramatically increased and accelerated compared with standard PROTACs. Moreover, we demonstrated that this approach could be generalized to another hydrophobic tag (HyT) degrader by demonstrating the improved targeted protein degradation after pre-fusion the HyT degrader with heat shock protein 70 (HSP70).

Neurotransmitter-derived lipidoids (NT-lipidoids) for enhanced brain delivery through intravenous injection.

Safe and efficient delivery of blood-brain barrier (BBB)-impermeable cargos into the brain through intravenous injection remains a challenge. Here, we developed a previously unknown class of neurotransmitter-derived lipidoids (NT-lipidoids) as simple and effective carriers for enhanced brain delivery of several BBB-impermeable cargos. Doping the NT-lipidoids into BBB-impermeable lipid nanoparticles (LNPs) gave the LNPs the ability to cross the BBB. Using this brain delivery platform, we successfully delivered amphotericin B (AmB), antisense oligonucleotides (ASOs) against tau, and genome-editing fusion protein (-27)GFP-Cre recombinase into the mouse brain via systemic intravenous administration. We demonstrated that the NT-lipidoid formulation not only facilitates cargo crossing of the BBB, but also delivery of the cargo into neuronal cells for functional gene silencing or gene recombination. This class of brain delivery lipid formulations holds great potential in the treatment of central nervous system diseases or as a tool to study the brain function.

Imidazole-Based Synthetic Lipidoids for In†Vivo mRNA Delivery into Primary T Lymphocytes.

Engineering T lymphocytes is an emerging approach in a variety of biomedical applications. However, delivering large biologics to primary T lymphocytes directly in vivo is technically challenging due to the low transfection efficacy. Herein, we investigated a library of synthetic lipid-like molecules (lipidoids) for their capability of delivering mRNA into primary T lymphocytes both ex vivo and in vivo. We initially screened a library with a large structural variety of lipidoids ex vivo and identified imidazole-containing lipidoids that are particularly potent in T lymphocytes transfection. We further optimized lipidoid structures by constructing and screening a detailed lipidoid library containing imidazole or imidazole analogues to perform a structure-activity correlation analysis. Using the lead lipidoid as a delivery vehicle for Cre mRNA in vivo through intravenous injection, we achieved 8.2 % gene recombination in mouse T lymphocytes.

Protein and mRNA Delivery Enabled by Cholesteryl-Based Biodegradable Lipidoid Nanoparticles.

Developing safe and efficient delivery systems for therapeutic biomacromolecules is a long-standing challenge. Herein, we report a newly developed combinatorial library of cholesteryl-based disulfide bond-containing biodegradable cationic lipidoid nanoparticles. We have identified a subset of this library which is effective for protein and mRNA delivery in vitro and in vivo. These lipidoids showed comparable transfection efficacies but much lower cytotoxicities compared to the Lpf2k in vitro. In vivo studies in adult mice demonstrated the successful delivery of genome engineering protein and mRNA molecules in the skeletal muscle (via intramuscular injection), lung and spleen (via intravenous injection), and brain (via lateral ventricle infusion).

Ex vivo cell-based CRISPR/Cas9 genome editing for therapeutic applications.

The recently developed CRISPR/Cas9 technology has revolutionized the genome engineering field. Since 2016, increasing number of studies regarding CRISPR therapeutics have entered clinical trials, most of which are focusing on the ex vivo genome editing. In this review, we highlight the ex vivo cell-based CRISPR/Cas9 genome editing for therapeutic applications. In these studies, CRISPR/Cas9 tools were used to edit cells in vitro and the successfully edited cells were considered as therapeutics, which can be introduced into patients to treat diseases. Considering a large number of previous reviews have been focused on the CRISPR/Cas9 delivery methods and materials, this review provides a different perspective, by mainly introducing the targeted conditions and design strategies for ex vivo CRISPR/Cas9 therapeutics. Brief descriptions of the history, functionality, and applications of CRISPR/Cas9 systems will be introduced first, followed by the design strategies and most significant results from previous research that used ex vivo CRISPR/Cas9 genome editing for the treatment of conditions or diseases. The last part of this review includes general information about the status of CRISPR/Cas9 therapeutics in clinical trials. We also discuss some of the challenges as well as the opportunities in this research area.

In Vitro and In Vivo Study of Amphotericin B Formulation with Quaternized Bioreducible Lipidoids.

Invasive fungal infections are well-known causes of morbidity and mortality in immunocompromised patients. Amphotericin B (AmB) is a polyene fungicidal agent with excellent properties of the broad antifungal spectrum, high activity, and relatively rare drug resistance. However, significant toxicities limit the clinical application of AmB and its conventional formulation AmB deoxycholate (Fungizone). Here we investigated nanoparticle formulations of AmB using synthetic biodegradable lipidoids and evaluated their stability, in vitro antifungal efficacy, and in vivo toxicity and pharmacokinetics. We found that the AmB formulated using a mixture of quaternized lipidoid (Q78-O14B) and DSPE-PEG2000 has the size around 70-100 nm and is stable during storage. The formulation showed no hemotoxicity to red blood cells (RBCs) in vitro. It also possesses the highest antifungal activity (in vitro) and lowest toxicity (both in vitro and in vivo). These metrics are significantly superior to the commercial antifungal product Fungizone. Meanwhile, AmB/Q78-O14B-P exhibited prolonged blood circulation in comparison to Fungizone in vivo. In AmB/Q78-O14B-P formulation, AmB was still detectable in the liver, spleen, and lung tissues with a concentration above the minimum inhibitory concentrations 72 h after low-dose intravenous injection. Based on these results, AmB in lipidoid nanoparticle formulation may produce sustained antifungal activity against blood-borne and systemic organ infections. Moreover, the new AmB formulation showed low nephrotoxicity and hepatotoxicity in rats even at high doses, allowing a dramatically wider and safer therapeutic window than Fungizone. This method provides a means to develop much needed antifungal agents that will be more therapeutically efficacious, more affordable (than AmBisome), and less toxic (than Fungizone) for the treatment of systemic fungal infections.

Nonviral Nanoparticles for CRISPR-Based Genome Editing: Is It Just a Simple Adaption of What Have Been Developed for Nucleic Acid Delivery?

Genome-editing technologies hold tremendous potential for treating genetic diseases. However, the efficient and safe delivery of genome-editing elements to the location of interest, and the achievement of specific targeted gene correction without off-target side effect remains a big challenge. In this Perspective, we highlight recent developments and discuss the challenges of nonviral nanoparticles for the delivery of genome-editing tools. Finally, we will propose promising strategies to improve the delivery efficacy and advance the clinical translation of gene-editing technology.

Intracellular delivery and biodistribution study of CRISPR/Cas9 ribonucleoprotein loaded bioreducible lipidoid nanoparticles.

CRISPR/Cas9 ribonucleoprotein (RNP) complexes with transient therapeutic activity and minimum off-target effects have attracted tremendous attention in recent years for genome editing and have been successfully employed in diverse targets. One ongoing challenge is how to transport structurally and functionally intact Cas9 protein and guide RNA molecules into cells efficiently and safely. Here we report a combinatorial library of disulfide bond-containing cationic lipidoid nanoparticles (LNPs) as carrier systems for intracellular Cas9/sgRNA delivery and subsequent genome editing. Nanoparticles with high efficacies of targeted gene knockout as well as relatively low cytotoxicities have been identified through in vitro screening. The in vivo biodistribution profiles were studied utilizing fluorescent dye labeled and RNP complexed LNPs. Results from this study may shed some light on the design of effective cationic lipidoids for intracellular delivery of genome editing platforms, as well as optimizing the nanoparticle formulations for further disease modeling and therapeutic applications.

Integrating Combinatorial Lipid Nanoparticle and Chemically Modified Protein for Intracellular Delivery and Genome Editing.

The use of protein to precisely manipulate cell signaling is an effective approach for controlling cell fate and developing precision medicine. More recently, programmable nucleases, such as CRISPR/Cas9, have shown extremely high potency for editing genetic flow of mammalian cells, and for treating genetic disorders. The therapeutic potential of proteins with an intracellular target, however, is mostly challenged by their low cell impermeability. Therefore, a developing delivery system to transport protein to the site of action in a spatiotemporal controlled manner is of great importance to expand the therapeutic index of the protein. In this Account, we first summarize our most recent advances in designing combinatorial lipid nanoparticles with diverse chemical structures for intracellular protein delivery. By designing parallel Michael addition or ring-opening reaction of aliphatic amines, we have generated a combinatorial library of cationic lipids, and identified several leading nanoparticle formulations for intracellular protein delivery both in vitro and in vivo. Moreover, we optimized the chemical structure of lipids to control lipid degradation and protein release inside cells for CRISPR/Cas9 genome-editing protein delivery. In the second part of this Account, we survey our recent endeavor in developing a chemical approach to modify protein, in particular, coupled with the nanoparticle delivery platform, to improve protein delivery for targeted diseases treatment and genome editing. Chemical modification of protein is a useful tool to modulate protein function and to improve the therapeutic index of protein drugs. Herein, we mostly summarize our recent advances on designing chemical approaches to modify protein with following unique findings: (1) chemically modified protein shows selective turn-on activity based on the specific intracellular microenvironment, with which we were able to protein-based targeted cancer therapy; (2) the conjugation of hyaluronic acid (HA) to protein allows cancer cell surface receptor-targeted delivery of protein; (3) the introduction of nonpeptidic boronic acid into protein enabled cell nucleus targeted delivery; this is the first report that a nonpeptidic signal can direct protein to subcellular compartment; and (4) the fusion of protein with negatively supercharged green fluorescent protein (GFP) facilitates the self-assembly of protein with lipid nanoparticle for genome-editing protein delivery. At the end of the Account, we give a perspective of expanding the chemistry that could be integrated to design biocompatible lipid nanocarriers for protein delivery and genome editing in vitro and in vivo, as well as the chemical approaches that we can harness to modulate protein activity in live cells for targeted diseases treatment.

Combinatorial library of chalcogen-containing lipidoids for intracellular delivery of genome-editing proteins.

Protein based therapeutics with high specificities and low off-target effects are used for transient and accurate manipulation of cell functions. However, developing safe and efficient carriers for intracellular delivery of active therapeutic proteins is a long-standing challenge. Here we report a combinatorial library of chalcogen (O, S, Se) containing lipidoid nanoparticles (LNPs) as efficient nanocarriers for intracellular delivery of negatively supercharged Cre recombinase ((-30)GFP-Cre) and anionic Cas9:single-guide RNA (Cas9:sgRNA) ribonucleoprotein (RNP) for genome editing. The structure-activity relationship between the lipidoids and intracellular protein delivery efficiencies was explored and it was demonstrated that the newly developed LNPs are effective for gene recombination in vivo.

Engineering the Delivery System for CRISPR-Based Genome Editing.

Clustered regularly interspaced short palindromic repeat-CRISPR-associated protein (CRISPR-Cas) systems, found in nature as microbial adaptive immune systems, have been repurposed into an important tool in biological engineering and genome editing, providing a programmable platform for precision gene targeting. These tools have immense promise as therapeutics that could potentially correct disease-causing mutations. However, CRISPR-Cas gene editing components must be transported directly to the nucleus of targeted cells to exert a therapeutic effect. Thus, efficient methods of delivery will be critical to the success of therapeutic genome editing applications. Here, we review current strategies available for in vivo delivery of CRISPR-Cas gene editing components and outline challenges that need to be addressed before this powerful tool can be deployed in the clinic.

Nanoparticles for CRISPR-Cas9 delivery.

The DNA mutation that causes Duchenne muscular dystrophy in mice can be corrected, with minimal off-target effects, by gold nanoparticles carrying the CRISPR components.

Altered Hippocampal Neurogenesis and Amygdalar Neuronal Activity in Adult Mice with Repeated Experience of Aggression.

Repeated experience of winning in a social conflict setting elevates levels of aggression and may lead to violent behavioral patterns. Here, we use a paradigm of repeated aggression and fighting deprivation to examine changes in behavior, neurogenesis, and neuronal activity in mice with positive fighting experience. We show that for males, repeated positive fighting experience induces persistent demonstration of aggression and stereotypic behaviors in daily agonistic interactions, enhances aggressive motivation, and elevates levels of anxiety. When winning males are deprived of opportunities to engage in further fights, they demonstrate increased levels of aggressiveness. Positive fighting experience results in increased levels of progenitor cell proliferation and production of young neurons in the hippocampus. This increase is not diminished after a fighting deprivation period. Furthermore, repeated winning experience decreases the number of activated (c-fos-positive) cells in the basolateral amygdala and increases the number of activated cells in the hippocampus; a subsequent no-fight period restores the number of c-fos-positive cells. Our results indicate that extended positive fighting experience in a social conflict heightens aggression, increases proliferation of neuronal progenitors and production of young neurons in the hippocampus, and decreases neuronal activity in the amygdala; these changes can be modified by depriving the winners of the opportunity for further fights.

Informing tendon tissue engineering with embryonic development.

Tendon is a strong connective tissue that transduces muscle-generated forces into skeletal motion. In fulfilling this role, tendons are subjected to repeated mechanical loading and high stress, which may result in injury. Tissue engineering with stem cells offers the potential to replace injured/damaged tissue with healthy, new living tissue. Critical to tendon tissue engineering is the induction and guidance of stem cells towards the tendon phenotype. Typical strategies have relied on adult tissue homeostatic and healing factors to influence stem cell differentiation, but have yet to achieve tissue regeneration. A novel paradigm is to use embryonic developmental factors as cues to promote tendon regeneration. Embryonic tendon progenitor cell differentiation in vivo is regulated by a combination of mechanical and chemical factors. We propose that these cues will guide stem cells to recapitulate critical aspects of tenogenesis and effectively direct the cells to differentiate and regenerate new tendon. Here, we review recent efforts to identify mechanical and chemical factors of embryonic tendon development to guide stem/progenitor cell differentiation toward new tendon formation, and discuss the role this work may have in the future of tendon tissue engineering.

Calorie restriction alleviates the age-related decrease in neural progenitor cell division in the aging brain.

Production of new neurons from stem cells is important for cognitive function, and the reduction of neurogenesis in the aging brain may contribute to the accumulation of age-related cognitive deficits. Restriction of calorie intake and prolonged treatment with rapamycin have been shown to extend the lifespan of animals and delay the onset of the age-related decline in tissue and organ function. Using a reporter line in which neural stem and progenitor cells are marked by the expression of green fluorescent protein (GFP), we examined the effect of prolonged exposure to calorie restriction (CR) or rapamycin on hippocampal neural stem and progenitor cell proliferation in aging mice. We showed that CR increased the number of dividing cells in the dentate gyrus of female mice. The majority of these cells corresponded to nestin-GFP-expressing neural stem or progenitor cells; however, this increased proliferative activity of stem and progenitor cells did not result in a significant increase in the number of doublecortin-positive newborn neurons. Our results suggest that restricted calorie intake may increase the number of divisions that neural stem and progenitor cells undergo in the aging brain of females.