A combinatorial library of unsaturated lipidoids for efficient intracellular gene delivery

Development of ionizable lipid nanoparticles and a lyophilized formulation for potent CRISPR-Cas9 delivery and genome editing

CRISPR-Cas genome editing technology holds great promise for wide-ranging biomedical applications. However, the development of efficient delivery system for CRISPR-Cas components remains challenging. Herein, we synthesized a series of ionizable lipids by conjugation of alkyl-acrylate to different amine molecules and further assembled ionizable lipid nanoparticles (iLNPs) for co-delivery of Cas9 mRNA and sgRNA. Among all the iLNP candidates, 1A14-iLNP with lipids containing spermine as amine head, demonstrated the highest cellular uptake, endosomal escape and mRNA expression in vitro. Co-delivery of Cas9 mRNA and sgRNA targeting EGFP by 1A14-iLNP achieved the highest EGFP knockout efficiency up to 70% in HeLa-EGFP cells. In addition, 1A14-iLNP displayed passive liver-targeting delivery of Cas9 mRNA in vivo with good biocompatibility. Moreover, we developed a simple method of lyophilization-mediated reverse transfection of CRISPR-Cas9 components for efficient genome editing. Therefore, the developed 1A14-iLNP and the lyophilization formulation, represent a potent solution for CRISPR-Cas9 delivery, which might broaden the future of biomedical applications of both mRNA and CRISPR-based therapies.

Intracellular Protein Delivery: Approaches, Challenges, and Clinical Applications

Protein biologics are powerful therapeutic agents with diverse inhibitory and enzymatic functions. However, their clinical use has been limited to extracellular applications due to their inability to cross plasma membranes. Overcoming this physiological barrier would unlock the potential of protein drugs for the treatment of many intractable diseases. In this review, we highlight progress made toward achieving cytosolic delivery of recombinant proteins. We start by first considering intracellular protein delivery as a drug modality compared to existing Food and Drug Administration-approved drug modalities. Then, we summarize strategies that have been reported to achieve protein internalization. These techniques can be broadly classified into 3 categories: physical methods, direct protein engineering, and nanocarrier-mediated delivery. Finally, we highlight existing challenges for cytosolic protein delivery and offer an outlook for future advances.

Exploration of mRNA nanoparticles based on DOTAP through optimization of the helper lipids

Lipid nanoparticles (LNPs) are one of the most efficient carriers for RNA packaging and delivery, and vaccines based on mRNA-LNPs have received substantial attention since the outbreak of the COVID-19 pandemic. LNPs based on 1,2-dioleoyl-3-trimethylammonium propane (DOTAP) have been widely used in preclinical and clinical settings. A novel non-viral gene delivery system called LNP3 was previously developed, which was composed of DOTAP, 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), and cholesterol. One of the helper lipids in this carrier was DOPE, which belongs to phospholipids. Given that substituting DOPE with non-phospholipids as helper lipids can increase the delivery efficiency of some LNPs, this study aimed to examine whether non-phospholipids can be formulated with DOTAP as helper lipids. It was found that monoglycerides with C14:0, C16:0, C18:0, C18:1, and C18:2 mediated mRNA transfection, and the transfection efficiency varied between C18:0, C18:1, and C18:2. Furthermore, substituting of the glycerol with other moieties such as the cholesterol or the ethanolamine similarly mediated mRNA transfection. The introduction of cholesterol can further improve the transfection capacity of some DOTAP-based LNPs. One of the best-performing formulations, LNP3-MO, was used to mediate luciferase-mRNA expression in vivo, and the luminescence signal was found to be mainly enriched in the lung and spleen. In addition, the level of SARS-CoV-2 spike antibody in the serum increased after three doses of LNP3-MO mediated SARS-CoV-2 spike mRNA. Altogether, this study demonstrates that non-phospholipids are promising helper lipids that can be formulated with DOTAP to facilitate efficient delivery of mRNAs in vitro and in vivo with organ-specific targeting.

Multiple Routes to Bicontinuous Cubic Liquid Crystal Phases Discovered by High-Throughput Self-Assembly Screening of Multi-Tail Lipidoids

Bicontinuous cubic phases offer advantageous routes to a broad range of applied materials ranging from drug delivery devices to membranes. However, a priori design of molecules that assemble into these phases remains a technological challenge. In this article, a high-throughput synthesis of lipidoids that undergo protonation-driven self-assembly (PrSA) into liquid crystalline (LC) phases is conducted. With this screening approach, 12 different multi-tail lipidoid structures capable of assembling into the bicontinuous double gyroid phase are discovered. The large volume of small-angle X-ray scattering (SAXS) data uncovers unexpected design criteria that enable phase selection as a function of lipidoid headgroup size and architecture, tail length and architecture, and counterion identity. Surprisingly, combining branched headgroups with bulky tails forces lipidoids to adopt unconventional pseudo-disc conformations that pack into double gyroid networks, entirely distinct from other synthetic or biological amphiphiles within bicontinuous cubic phases. From a multitude of possible applications, two examples of functional materials from lipidoid liquid crystals are demonstrated. First, the fabrication of gyroid nanostructured films by interfacial PrSA, which are rapidly responsive to the external medium. Second, it is shown that colloidally-dispersed lipidoid cubosomes, for example, for drug delivery, are easily assembled using top-down solvent evaporation methods.

Tailoring combinatorial lipid nanoparticles for intracellular delivery of nucleic acids, proteins, and drugs

Lipid nanoparticle (LNP)-based drug delivery systems have become the most clinically advanced non-viral delivery technology. LNPs can encapsulate and deliver a wide variety of bioactive agents, including the small molecule drugs, proteins and peptides, and nucleic acids. However, as the physicochemical properties of small- and macromolecular cargos can vary drastically, every LNP carrier system needs to be carefully tailored in order to deliver the cargo molecules in a safe and efficient manner. Our group applied the combinatorial library synthesis approach and in vitro and in vivo screening strategy for the development of LNP delivery systems for drug delivery. In this Review, we highlight our recent progress in the design, synthesis, characterization, evaluation, and optimization of combinatorial LNPs with novel structures and properties for the delivery of small- and macromolecular therapeutics both in vitro and in vivo. These delivery systems have enormous potentials for cancer therapy, antimicrobial applications, gene silencing, genome editing, and more. We also discuss the key challenges to the mechanistic study and clinical translation of new LNP-enabled therapeutics.

Reactive Oxygen Species─Responsive Lipid Nanoparticles for Effective RNAi and Corneal Neovascularization Therapy

Corneal neovascularization (CNV) is a common disease that affects the vision ability of more than 1 million people annually. Small interfering RNA (siRNA) delivery nanoparticle platforms are a promising therapeutic modality for CNV treatment. However, the efficient delivery of siRNA into cells and the effective release of siRNA from delivery vehicles in a particular cell type challenge effective RNAi clinical application for CNV suppression. This study reports the design of a novel reactive oxygen species (ROS)-responsive lipid nanoparticle for siRNA delivery into corneal lesions for enhanced RNAi as a potential CNV treatment. We demonstrated that lipid nanoparticles could efficiently deliver siRNA into human umbilical vein endothelial cells and release siRNA for enhanced gene silencing by using the upregulated ROS of CNV to promote lipid nanoparticle degradation. Moreover, the subconjunctival injection of siRNA nanocomplexes into corneal lesions effectively knocked down vascular endothelial growth factor expression and suppressed CNV formation in an alkali burn model. Thus, we believe that the strategy of using ROS-responsive lipid nanoparticles for enhanced RNAi in CNV could be further extended to a promising clinical therapeutic approach to attenuate CNV formation.

Lung-selective mRNA delivery of synthetic lipid nanoparticles for the treatment of pulmonary lymphangioleiomyomatosis

Safe and efficacious systemic delivery of messenger RNA (mRNA) to specific organs and cells in vivo remains the major challenge in the development of mRNA-based therapeutics. Targeting of systemically administered lipid nanoparticles (LNPs) coformulated with mRNA has largely been confined to the liver and spleen. Using a library screening approach, we identified that N-series LNPs (containing an amide bond in the tail) are capable of selectively delivering mRNA to the mouse lung, in contrast to our previous discovery that O-series LNPs (containing an ester bond in the tail) that tend to deliver mRNA to the liver. We analyzed the protein corona on the liver- and lung-targeted LNPs using liquid chromatography-mass spectrometry and identified a group of unique plasma proteins specifically absorbed onto the surface that may contribute to the targetability of these LNPs. Different pulmonary cell types can also be targeted by simply tuning the headgroup structure of N-series LNPs. Importantly, we demonstrate here the success of LNP-based RNA therapy in a preclinical model of lymphangioleiomyomatosis (LAM), a destructive lung disease caused by loss-of-function mutations in the Tsc2 gene. Our lung-targeting LNP exhibited highly efficient delivery of the mouse tuberous sclerosis complex 2 (Tsc2) mRNA for the restoration of TSC2 tumor suppressor in tumor and achieved remarkable therapeutic effect in reducing tumor burden. This research establishes mRNA LNPs as a promising therapeutic intervention for the treatment of LAM.

Developing Biodegradable Lipid Nanoparticles for Intracellular mRNA Delivery and Genome Editing

Since the U.S. Food and Drug Administration (FDA) granted emergency use authorization for two mRNA vaccines against SARS-CoV-2, mRNA-based technology has attracted broad attention from the scientific community to investors. When delivered intracellularly, mRNA has the ability to produce various therapeutic proteins, enabling the treatment of a variety of illnesses, including but not limited to infectious diseases, cancers, and genetic diseases. Accordingly, mRNA holds significant therapeutic potential and provides a promising means to target historically hard-to-treat diseases. Current clinical efforts harnessing mRNA-based technology are focused on vaccination, cancer immunotherapy, protein replacement therapy, and genome editing. The clinical translation of mRNA-based technology has been made possible by leveraging nanoparticle delivery methods. However, the application of mRNA for therapeutic purposes is still challenged by the need for specific, efficient, and safe delivery systems.This Account highlights key advances in designing and developing combinatorial synthetic lipid nanoparticles (LNPs) with distinct chemical structures and properties for in vitro and in vivo intracellular mRNA delivery. LNPs represent the most advanced nonviral nanoparticle delivery systems that have been extensively investigated for nucleic acid delivery. The aforementioned COVID-19 mRNA vaccines and one LNP-based small interfering RNA (siRNA) drug (ONPATTRO) have received clinical approval from the FDA, highlighting the success of synthetic ionizable lipids for in vivo nucleic acid delivery. In this Account, we first summarize the research efforts from our group on the development of bioreducible and biodegradable LNPs by leveraging the combinatorial chemistry strategy, such as the Michael addition reaction, which allows us to easily generate a large set of lipidoids with diverse chemical structures. Next, we discuss the utilization of a library screening strategy to identify optimal LNPs for targeted mRNA delivery and showcase the applications of the optimized LNPs in cell engineering and genome editing. Finally, we outline key challenges to the clinical translation of mRNA-based therapies and propose an outlook for future directions of the chemical design and optimization of LNPs to improve the safety and specificity of mRNA drugs. We hope this Account provides insight into the rational design of LNPs for facilitating the development of mRNA therapeutics, a transformative technology that promises to revolutionize future medicine.

Osteogenic effects of microRNA-335-5p/lipidoid nanoparticles coated on titanium surface

OBJECTIVE

In this study, we aimed to investigate the therapeutic potential of miR-335-5p lipidoid nanocomplexes coated on Titanium (Ti) SLActive surface by lyophilization.

DESIGN

In our model, we coated miR-335-5p/Lipidoid nanoparticles on titanium implant, seeded GFP-labelled mouse bone marrow stromal cells (BMSCs) onto the functionalized Ti implant surface, and analyzed the transfection efficiency, cell adhesion, proliferation, and osteogenic activity of the bone-implant interface.

RESULTS

The Ti SLActive surface displayed a suitable hydrophilicity ability and provided a large surface area for miRNA loading, enabling spatial retention of the miRNAs within the nanopores until cellular delivery. We demonstrated a high transfection efficiency of miR-335-5p lipidoid nanoparticles in BMSCs seeded onto the Ti SLActive surface, even after 14 days. Alkaline phosphatase (ALP) activity and cell vitality were significantly increased in BMSCs transfected with miR-335-5p at 7 and 14 days as opposed to cells transfected with negative controls. When miR-335-5p transfected BMSCs were induced to undergo osteogenic differentiation, we detected increased mRNA expression of osteogenic markers including Alkaline phosphatase (ALP), collagen I (COL1), osteocalcin (OCN) and bone sialoprotein (BSP) at 7 and 14 days as compared with negative controls.

CONCLUSION

MiR-335-5p lipidoid nanoparticles could be used as a new cost-effective methodology to increase the osteogenic capacity of biomedical Ti implants.

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.

Computational and Experimental Approaches to Investigate Lipid Nanoparticles as Drug and Gene Delivery Systems

Lipid nanoparticles (LNPs) have been widely applied in drug and gene delivery. More than twenty years ago, DoxilTM was the first LNPs-based drug approved by the US Food and Drug Administration (FDA). Since then, with decades of research and development, more and more LNP-based therapeutics have been used to treat diverse diseases, which often offer the benefits of reduced toxicity and/or enhanced efficacy compared to the active ingredients alone. Here, we provide a review of recent advances in the development of efficient and robust LNPs for drug/gene delivery. We emphasize the importance of rationally combining experimental and computational approaches, especially those providing multiscale structural and functional information of LNPs, to the design of novel and powerful LNP-based delivery systems.

Combinatorial Synthesis of a Lipidoid Library by Thiolactone Chemistry: In Vitro Screening and In Vivo Validation for siRNA Delivery

Transcriptional inhibition by small interfering RNA (siRNA) delivery using synthetic transfection agents eliminates the subsequent risk of introducing mutations in relevant genes, as opposed to viral vectors. However, synthetic vectors with comparable transfection efficiency to that of viral vectors are yet to be developed. Hence, synthesizing new transfection vehicles with low toxicity is important. In this study, a library of lipid-like molecules (lipidoids) was synthesized by thiolactone chemistry. This library facilitated nonviral delivery of siRNA to mammalian cells, inducing sequence-specific knockdown of a target gene. The liposomal nanoparticles complexed with anti-green fluorescent protein (GFP) siRNA were successfully screened for transfection efficiency using a HeLa-GFP cell line. The five best-performing lipidoids identified in the screening were found to exhibit superior GFP-knockdown efficiency compared with commercially available transfection reagents. The efficiency of siRNA delivery by one of these lipidoids with minimal toxicity was further successfully evaluated in vivo using Kdrl:EGFP zebrafish embryos as a model system. Our study would be important as a facile synthetic route of efficient nonviral nucleic acid delivery to live cells and organisms.

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.

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

A combinatorial library of cationic lipidoids were used as nanocarriers for intracellular delivery of the CRISPR/Cas9 ribonucleoprotein complex.

Current Progress on MicroRNA-Based Gene Delivery in the Treatment of Osteoporosis and Osteoporotic Fracture

Emerging evidence demonstrates that microRNAs, as important endogenous posttranscriptional regulators, are essential for bone remodeling and regeneration. Undoubtedly, microRNA-based gene therapies show great potential to become novel approaches against bone-related diseases, including osteoporosis and associated fractures. The major obstacles for continued advancement of microRNA-based therapies in clinical application include their poor in vivo stability, nonspecific biodistribution, and unwanted side effects. Appropriate chemical modifications and delivery vectors, which improve the biological performance and potency of microRNA-based drugs, hold the key to translating miRNA technologies into clinical practice. Thus, this review summarizes the current attempts and existing deficiencies of chemical modifications and delivery systems applied in microRNA-based therapies for osteoporosis and osteoporotic fractures to inform further explorations.

Intracellular delivery of the PTEN protein using cationic lipidoids for cancer therapy

The phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is a tumor suppressor, mutated or inactive in a large percentage of human cancers. Restoring PTEN activity in cancer cells through gene therapy has shown to inhibit cell growth and induce apoptosis, particularly in cells with a PTEN deficiency. Gene therapy, however, comes with some inherent risks such as triggering an immune response and permanent off target effects. Nanoparticle assisted protein delivery could mitigate these liabilities while maintaining therapeutic integrity. In this report, we evaluated the use of cationic lipid-like (lipidoid) materials to intracellularly deliver the PTEN protein. We synthesized a small library of cationic lipidoid materials and screened for the delivery of PTEN based on cell viability. The lipidoid material EC16-80 was selected for high efficacy and the subsequent lipidoid-protein complex was characterized using DLS, zeta potential, and TEM. Intracellular delivery of PTEN with EC16-80 to the PTEN deficient prostate cancer cell line PC-3 resulted in a significant decrease in activated AKT and induced apoptosis. Interestingly, delivery of PTEN to PTEN deficient prostate cancer cell lines PC-3 and LNCaP compared to the breast cancer cell line, MCF-7 with endogenous PTEN, resulted in significantly lower IC₅₀ values in PC-3 and LNCaP cells indicating that the treatment is predominantly specific to PTEN-deficient cells. Altogether, these results demonstrate the first intracellular delivery of recombinant PTEN using a synthetic delivery vehicle and highlight the potential of intracellular PTEN protein delivery as a potential targeted cancer therapy.

Immunogenicity Testing of Lipidoids In Vitro and In Silico: Modulating Lipidoid-Mediated TLR4 Activation by Nanoparticle Design

Therapeutics based on small interfering RNA (siRNA) have promising potential as antiviral and anti-inflammatory agents. To deliver siRNA across cell membranes to reach the RNAi pathway in the cytosol of target cells, non-viral nanoparticulate delivery approaches are explored. Recently, we showed that encapsulation of siRNA in lipid-polymer hybrid nanoparticles (LPNs), based on poly(DL-lactic-co-glycolic acid) (PLGA) and cationic lipid-like materials (lipidoids), remarkably enhances intracellular delivery of siRNA as compared to siRNA delivery with LPNs modified with dioleoyltrimethylammoniumpropane (DOTAP) as the lipid component. However, the potential immune modulation by these cationic lipids remains unexplored. By testing lipidoids and DOTAP for innate immune-receptor-activating properties in vitro, we found that neither lipidoids nor DOTAP activate human Toll-like receptor (TLR) 2, 3, 7, and 9. However, in contrast to DOTAP, lipidoids are strong agonists for TLR4 and activate murine antigen-presenting cells in vitro. This agonistic effect was further confirmed in silico using a prediction model based on crystal structures. Also, lipidoids formulated as lipoplexes or as stable nucleic acid lipid particles, which was the reference formulation for siRNA delivery, proved to activate TLR4. However, by combining lipidoids with PLGA into LPNs, TLR4 activation was abrogated. Thus, lipidoid-mediated TLR4 activation during siRNA delivery may be modulated via optimization of the formulation design.

A novel Lipidoid-MicroRNA formulation promotes calvarial bone regeneration

Specific microRNAs (miRs) and the Wnt signaling pathway play critical roles in regulating bone development and homeostasis. Our previous studies revealed the ability of miR-335-5p to promote osteogenic differentiation by downregulating Wnt antagonist Dickkopf-1 (DKK1). The purpose of this study was to use nano-materials to efficiently deliver miR-335-5p into osteogenic cells for tissue engineering applications. We synthesized and screened a library of 12 candidate nano-lipidoids，of which L8 was identified as the preferred biodegradable lipidoid for miRNA molecule delivery into cells. We then investigated whether a lipidoid-miRNA formulation of miR-335-5-p (LMF-335) could successfully deliver miR-335-5-p into cells to promote osteogenesis in vitro and calvarial bone healing in vivo. Transfection of C3H10T1/2 cells and bone marrow stromal cells (BMSCs) with LMF-335 led to decreased expression of DKK1 and increased expression of the key osteogenic genes. LMF-335 and LMF-335-transfected BMSCs were then used in combination with silk scaffolds to evaluate healing of critical-size calvarial bone defects in mice. The results revealed significant new bone formation in the defects in LMF-335 groups as compared with control groups. In conclusion, this first report supports the notion that lipidoid delivery of miRNA can be used to induce osteogenic differentiation of stem cells and bone regeneration.

One-Pot Parallel Synthesis of Lipid Library via Thiolactone Ring Opening and Screening for Gene Delivery

Efficient delivery of nucleic acids into cells is of great interest in the field of cell biology and gene therapy. Despite a lot of research, transfection efficiency and structural diversity of gene-delivery vectors are still limited. A better understanding of the structure-function relationship of gene delivery vectors is also essential for the design of novel and intelligent delivery vectors, efficient in "difficult-to-transfect" cells and in vivo clinical applications. Most of the existing strategies for the synthesis of gene-delivery vectors require multiple steps and lengthy procedures. Here, we demonstrate a facile, three-component one-pot synthesis of a combinatorial library of 288 structurally diverse lipid-like molecules termed "lipidoids" via a thiolactone ring opening reaction. This strategy introduces the possibility to synthesize lipidoids with hydrophobic tails containing both unsaturated bonds and reducible disulfide groups. The whole synthesis and purification are convenient, extremely fast, and can be accomplished within a few hours. Screening of the produced lipidoids using HEK293T cells without addition of helper lipids resulted in identification of highly stable liposomes demonstrating ∼95% transfection efficiency with low toxicity.

Cationic Polypeptoids with Optimized Molecular Characteristics toward Efficient Nonviral Gene Delivery

The rational design of gene vectors relies on the understanding of their structure-property relationship. Polypeptoids, which are structural isomers of natural polypeptides, hold great potential as gene delivery vectors due to their facile preparation, structural tunability, and most importantly, their desirable proteolytic stability. We herein designed a library of polypeptoids with different cationic side-chain terminal groups, degree of polymerizations (DPs), side-chain lengths, and incorporated aliphatic side chains, to unravel the structure-property relationships so that gene delivery efficiency can be maximized and cytotoxicity can be minimized. In HeLa cells, a polypeptoid bearing a primary amine side-chain terminal group exhibited remarkably higher transfection efficiency than that of its analogues containing secondary, tertiary, or quaternary amine groups. Elongation of the polypeptoid backbone length (from 28 to 251 mer) led to enhanced DNA condensation as well as cellular uptake levels, however it also caused higher cytotoxicity. Upon a proper balance between DNA uptake and cytotoxicity, the polypeptoid with a DP of 46 afforded the highest transfection efficiency. Elongating the aliphatic spacer between the backbone and side amine groups enhanced the hydrophobicity of the side chains, which resulted in notably increased membrane activities and transfection efficiency. Further incorporation of hydrophobic decyl side chains led to an improvement in transfection efficiency of ∼6 fold. The top-performing material identified, P11, mediated successful gene transfection under serum-containing conditions, outperforming the commercial transfection reagent poly(ethylenimine) by nearly 4 orders of magnitude. Reflecting its excellent serum-resistant properties, P11 further enabled effective transfection in vivo following intratumoral injection to melanoma-bearing mice. This study will help the rational design of polypeptoid-based gene delivery materials, and the best-performing material identified may provide a potential supplement to existing gene vectors.

Preparation and Optimization of Lipid-Like Nanoparticles for mRNA Delivery

Lipid-like nanoparticles (LLNs) have shown great promise for nucleic acid delivery. Recently, we have developed N ¹,N ³,N ⁵-tris(2-aminoethyl)benzene-1,3,5-tricarboxamide (TT) derived lipid-like compounds, formulated them into TT LLNs for mRNA delivery, and applied an orthogonal array design to facilitate formulation optimization. This chapter focuses on the following contents relevant to lipid-like nanoparticles: formulation method, particle characterization, orthogonal array design, and in vitro assays.

Galactosylated Lipidoid Nanoparticles for Delivery of Small Interfering RNA to Inhibit Hepatitis C Viral Replication In Vivo

Small interfering RNA (siRNA) delivery can provide an effective therapy for treating viral diseases by silencing genes involved in viral replication. In this study, a liver-targeting formulation of lipidoid nanoparticle for delivery of siRNA that targets protein kinase C-related kinase 2 (PRK2) to inhibit hepatitis C virus (HCV) replication is reported. The most effective, minimally cytotoxic lipidoid for siRNA delivery to hepatic cells is identified from a small library of alkyl epoxide-polyamine conjugates. In vitro transfection of PRK2 siRNA (siPRK2) using this lipidoid induces significant silencing of PRK2 (≈80%), suppressing HCV replication in human hepatic cells transfected with the HCV subgenomic replicon. Systemic administration of siPRK2 using the lipidoid nanoparticles results in significant reduction of host PRK2 in the mouse liver (≈60%). This treatment significantly suppresses HCV replication in an HCV-xenograft mouse model. siRNA delivery to the liver is further improved via galactosylation of the lipidoid. Compared with the unmodified lipidoid formulation, galactosylated lipidoids induce greater silencing of host PRK2 in mouse livers (≈80%) and more rapid suppression of HCV replication in an HCV-xenograft mouse. This study suggests that galactosylated lipidoid nanoparticles could provide a treatment for hepatitis C by mediating delivery of anti-viral RNA interference therapeutics to the liver.

Non-viral delivery of genome-editing nucleases for gene therapy

Manipulating the genetic makeup of mammalian cells using programmable nuclease-based genome-editing technology has recently evolved into a powerful avenue that holds great potential for treating genetic disorders. There are four types of genome-editing nucleases, including meganucleases, zinc finger nucleases, transcription activator-like effector nucleases and clustered, regularly interspaced, short palindromic repeat-associated nucleases such as Cas9. These nucleases have been harnessed to introduce precise and specific changes of the genome sequence at virtually any genome locus of interest. The therapeutic relevance of these genome-editing technologies, however, is challenged by the safe and efficient delivery of nuclease into targeted cells. Herein, we summarize recent advances that have been made on non-viral delivery of genome-editing nucleases. In particular, we focus on non-viral delivery of Cas9/sgRNA ribonucleoproteins for genome editing. In addition, the future direction for developing non-viral delivery of programmable nucleases for genome editing is discussed.

Superhydrophilic-Superhydrophobic Patterned Surfaces as High-Density Cell Microarrays: Optimization of Reverse Transfection

High-density microarrays can screen thousands of genetic and chemical probes at once in a miniaturized and parallelized manner, and thus are a cost-effective alternative to microwell plates. Here, high-density cell microarrays are fabricated by creating superhydrophilic-superhydrophobic micropatterns in thin, nanoporous polymer substrates such that the superhydrophobic barriers confine both aqueous solutions and adherent cells within each superhydrophilic microspot. The superhydrophobic barriers confine and prevent the mixing of larger droplet volumes, and also control the spreading of droplets independent of the volume, minimizing the variability that arises due to different liquid and surface properties. Using a novel liposomal transfection reagent, ScreenFect A, the method of reverse cell transfection is optimized on the patterned substrates and several factors that affect transfection efficiency and cytotoxicity are identified. Higher levels of transfection are achieved on HOOC- versus NH₂ -functionalized superhydrophilic spots, as well as when gelatin and fibronectin are added to the transfection mixture, while minimizing the amount of transfection reagent improves cell viability. Almost no diffusion of the printed transfection mixtures to the neighboring microspots is detected. Thus, superhydrophilic-superhydrophobic patterned surfaces can be used as cell microarrays and for optimizing reverse cell transfection conditions before performing further cell screenings.

Lipidoid nanoparticle mediated silencing of Mcl-1 induces apoptosis in mantle cell lymphoma

Conventional chemo-immunotherapy fails to cure the majority of mantle cell lymphoma patients and causes substantial toxicity. Resistant mantle cell lymphoma cells commonly overexpress and are dependent on the anti-apoptotic protein, Mcl-1, for survival. In this study, we use potent lipidoid nanoparticles to deliver siRNA to silence Mcl-1 expression. Studies were conducted using two different mantle cell lymphoma cell lines, a normal (JeKo-1) and an aggressive (MAVER-1) line, to assess the ability of lipidoid nanoparticles to be used broadly in the treatment of mantle cell lymphoma. Mcl-1 mRNA silencing and protein knockdown was observed as early as one day after treatment and the lipidoid nanoparticles achieved sustained silencing of Mcl-1 mRNA for at least four days in both JeKo-1 and MAVER-1 cells. Eighty percent silencing was achieved at three days post-transfection in JeKo-1 cells while 50% silencing was achieved in MAVER-1 cells, which are more resistant to transfection. Interestingly, silencing of Mcl-1 induced apoptosis in nearly 30% of both JeKo-1 and MAVER-1 cells three days post-transfection. Additionally, Mcl-1 silencing and the resultant apoptosis in mantle cell lymphoma cells were dose dependent. These data suggest that lipidoid nanoparticles siRNA therapy targeting Mcl-1 has potential as a new treatment modality for mantle cell lymphoma and many other cancers that overexpress Mcl-1. The combination of anti-Mcl-1 lipidoid nanoparticles with other forms of targeted therapy offers hope for reducing or replacing cytotoxic chemotherapy as standard treatment for mantle cell lymphoma.

Efficient delivery of genome-editing proteins using bioreducible lipid nanoparticles

A central challenge to the development of protein-based therapeutics is the inefficiency of delivery of protein cargo across the mammalian cell membrane, including escape from endosomes. Here we report that combining bioreducible lipid nanoparticles with negatively supercharged Cre recombinase or anionic Cas9:single-guide (sg)RNA complexes drives the electrostatic assembly of nanoparticles that mediate potent protein delivery and genome editing. These bioreducible lipids efficiently deliver protein cargo into cells, facilitate the escape of protein from endosomes in response to the reductive intracellular environment, and direct protein to its intracellular target sites. The delivery of supercharged Cre protein and Cas9:sgRNA complexed with bioreducible lipids into cultured human cells enables gene recombination and genome editing with efficiencies greater than 70%. In addition, we demonstrate that these lipids are effective for functional protein delivery into mouse brain for gene recombination in vivo. Therefore, the integration of this bioreducible lipid platform with protein engineering has the potential to advance the therapeutic relevance of protein-based genome editing.

Combinatorial Approach to Nanoarchitectonics for Nonviral Delivery of Nucleic Acids

Nanoparticles based on cationic polymers, lipids or lipidoids are of great interest in the field of gene delivery applications. The research on these nanosystems is rapidly growing as they hold promise to treat wide variety of human diseases ranging from viral infections to genetic disorders and cancer. Recently, combinatorial design principles have been adopted for rapid generation of large numbers of chemically diverse polymers and lipids capable of forming multifunctional nanocarriers for the use in gene delivery applications. At the same time, current high-throughput screening systems as well as convenient cell assays and readout techniques allow for fast evaluation of cell transfection efficiencies and toxicities of libraries of novel gene delivery agents. This allows for a rapid evaluation of structure-function relationship as well as identification of novel efficient nanocarriers for cell transfection and gene therapy. Here, the recent contribution of high-throughput synthesis to the development of novel nanocarriers for gene delivery applications is described.

Combinatorial library strategies for synthesis of cationic lipid-like nanoparticles and their potential medical applications

The past two decades have witnessed the high efficiency and efficacy of cationic lipids and liposomal formations for drug delivery. The tedious synthesis of conventional lipids and the inefficiency in studying structure-activity relationships, however, have hindered the clinical translation of lipid nanoparticle delivery systems. Combinatorial synthesis of lipid-like nanoparticles ('lipidoids') has recently emerged as an approach to accelerate the development of these delivery platforms. Utilizing a high-throughput screening strategy, the libraries of lipidoids are sorted and prime candidates for the delivery in the intended application can be identified and optimized for the next generation. In this review, we outline methods used for combinatorial lipidoid synthesis, the application of high-throughput screening, and the current medical applications of candidate lipidoids.

Long-term storage of lyophilized liposomal formulations

Because aqueous liposomal formulations containing multiply unsaturated lipids are susceptible to chemical degradation, these formulations are often lyophilized. Despite their limited chemical stability, interest in the use of multiply unsaturated lipids to promote intracellular delivery has increased considerably in recent years. The goal of the current study was to examine the long-term storage stability of lyophilized formulations containing lipids with increasing levels of unsaturation, and various strategies that can be employed to improve stability. Aqueous lipid-trehalose formulations containing 1,2-dilinolenoyl-sn-glycero-3-phosphocholine (DLPC), 1,2-dilinoleoyl-sn-glycero-3-phosphocholine (DLinPC), or 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) were lyophilized and stored at temperatures ranging from 4°C to 60°C. We observed that the lipid degradation rate increased as the storage temperature and unsaturation level were increased. Even the cleanest sugars, which are available commercially, contain iron contaminants, and it was observed that the chelation of these iron contaminants significantly improved the stability of DLPC during storage. However, the glass transition temperature of the sugar that was included in the formulation, the reduction of the oxygen in the aqueous sample prior to lyophilization, the inclusion of helper lipids (i.e., cholesterol), and the rate of freezing did not significantly improve stability.

Engineered nanoparticles for drug delivery in cancer therapy

In medicine, nanotechnology has sparked a rapidly growing interest as it promises to solve a number of issues associated with conventional therapeutic agents, including their poor water solubility (at least, for most anticancer drugs), lack of targeting capability, nonspecific distribution, systemic toxicity, and low therapeutic index. Over the past several decades, remarkable progress has been made in the development and application of engineered nanoparticles to treat cancer more effectively. For example, therapeutic agents have been integrated with nanoparticles engineered with optimal sizes, shapes, and surface properties to increase their solubility, prolong their circulation half-life, improve their biodistribution, and reduce their immunogenicity. Nanoparticles and their payloads have also been favorably delivered into tumors by taking advantage of the pathophysiological conditions, such as the enhanced permeability and retention effect, and the spatial variations in the pH value. Additionally, targeting ligands (e.g., small organic molecules, peptides, antibodies, and nucleic acids) have been added to the surface of nanoparticles to specifically target cancerous cells through selective binding to the receptors overexpressed on their surface. Furthermore, it has been demonstrated that multiple types of therapeutic drugs and/or diagnostic agents (e.g., contrast agents) could be delivered through the same carrier to enable combination therapy with a potential to overcome multidrug resistance, and real-time readout on the treatment efficacy. It is anticipated that precisely engineered nanoparticles will emerge as the next-generation platform for cancer therapy and many other biomedical applications.

Reactive oxygen species-responsive protein modification and its intracellular delivery for targeted cancer therapy

Herein we report a convenient chemical approach to reversibly modulate protein (RNase A) function and develop a protein that is responsive to reactive oxygen species (ROS) for targeted cancer therapy. The conjugation of RNase A with 4-nitrophenyl 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl) benzyl carbonate (NBC) blocks protein lysine and temporarily deactivates the protein. However, the treatment of RNase A-NBC with hydrogen peroxide (one major intracellular ROS) efficiently cleaves the NBC conjugation and restores the RNase A activity. Thus, RNase A-NBC can be reactivated inside tumor cells by high levels of intracellular ROS, thereby restoring the cytotoxicity of RNase A for cancer therapy. Due to higher ROS levels inside tumor cells compared to healthy cells, and the resulting different levels of RNase A-NBC reactivation, RNase A-NBC shows a significant specific cytotoxicity against tumor cells.

Enhanced intracellular siRNA delivery using bioreducible lipid-like nanoparticles

A new library of lipid-like nanoparticles (lipidoids) comprising disulfide bond is developed for siRNA delivery. Bioreducible lipidoids deliver siRNA with greater efficiency than nonbioreducible lipidoids with similar chemical structures. A siRNA release investigation, as well as an intracellular siRNA trafficking study, reveals that the degradation of bioreducible lipidoid in a strongly reductive intracellular environment boosts siRNA release and enhances siRNA gene knockdown efficiency.

Lyophilization of a triply unsaturated phospholipid: effects of trace metal contaminants

As liquid liposomal formulations are prone to chemical degradation and aggregation, these formulations often require freeze drying (e.g., lyophilization) to achieve sufficient shelf-life. However, liposomal formulations may undergo oxidation during lyophilization and/or during prolonged storage. The goal of the current study was to characterize the degradation of 1,2-dilinolenoyl-sn-glycero-3-phosphocholine (DLPC) during lyophilization and to also probe the influence of metal contaminants in promoting the observed degradation. Aqueous sugar formulations containing DLPC (0.01 mg/ml) were lyophilized, and DLPC degradation was monitored using HPLC/UV and GC/MS methods. The effect of ferrous ion and sucrose concentration, as well as lyophilization stage promoting lipid degradation, was investigated. DLPC degradation increased with higher levels of ferrous ion. After lyophilization, 103.1 ± 1.1%, 66.9 ± 0.8%, and 28.7 ± 0.7% DLPC remained in the sucrose samples spiked with 0.0 ppm, 0.2 ppm, and 1.0 ppm ferrous ion, respectively. Lipid degradation predominantly occurs during the freezing stage of lyophilization. Sugar concentration and buffer ionic strength also influence the extent of lipid degradation, and DLPC loss correlated with degradation product formation. We conclude that DLPC oxidation during the freezing stage of lyophilization dramatically compromises the stability of lipid-based formulations. In addition, we demonstrate that metal contaminants in sugars can become highly active when lyophilized in the presence of a reducing agent.