The Headgroup Evolution of Cationic Lipids for Gene Delivery

Development and applications of lipid hydrophilic headgroups for nucleic acid therapy

Nucleic acid therapy is currently the most promising method for treating tumors and genetic diseases and for preventing infectious diseases. However, the biggest obstacle to this therapy is delivery of the nucleic acids to the target site, which requires overcoming problems such as capture by the immune system, the need to penetrate biofilms, and degradation of nucleic acid performance. Designing suitable delivery vectors is key to solving these problems. Lipids-which consist of a hydrophilic headgroup, a linker, and a hydrophobic tail-are crucial components for the construction of vectors. The headgroup is particularly important because it affects the drug encapsulation rate, the vector cytotoxicity, and the transfection efficiency. Herein, we focus on various headgroup structures (tertiary amines, quaternary ammonium salts, peptides, piperazines, dendrimers, and several others), and we summarize and classify important lipid-based carriers that have been developed in recent years. We also discuss applications of cationic lipids with various headgroups for delivery of nucleic acid drugs, and we analyze how headgroup structure affects transport efficiency and carrier toxicity. Finally, we briefly describe the challenges of developing novel lipid carriers, as well as their prospects.

Low-Dose Mildronate-Derived Lipidoids for Efficient mRNA Vaccine Delivery with Minimal Inflammation Side Effects

mRNA vaccines have been revolutionizing disease prevention and treatment. However, their further application is hindered by inflammatory side effects, primarily caused by delivery systems such as lipid nanoparticles (LNPs). In response to this issue, we prepared cationic lipids (mLPs) derived from mildronate, a small-molecule drug, and subsequently developed the LNP (mLNP-69) comprising a low dose of mLP. Compared with the LNP (sLNP) based on SM-102, a commercially available ionizable lipid, mLNP-69 ensures effective mRNA delivery while significantly reducing local inflammation. In preclinical prophylactic and therapeutic B16-OVA melanoma models, mLNP-69 demonstrated successful mRNA cancer vaccine delivery in vivo, effectively preventing tumor occurrence or impeding tumor progression. The results suggest that the cationic lipids derived from mildronate, which exhibit efficient delivery capabilities and minimal inflammatory side effects, hold great promise for clinical application.

An overview of lipid constituents in lipid nanoparticle mRNA delivery systems

mRNA therapeutics have shown great potential for a broad spectrum of disease treatment. However, the challenges of mRNA's inherent instability and difficulty in cellular entry have hindered its progress in the biomedical field. To address the cellular barriers and deliver mRNA to cells of interest, various delivery systems are designed. Among these, lipid nanoparticles (LNPs) stand out as the most extensively used mRNA delivery systems, particularly following the clinical approvals of corona virus disease 2019 (COVID-19) mRNA vaccines. LNPs are comprised of ionizable cationic lipids, phospholipids, cholesterol, and polyethylene glycol derived lipids (PEG-lipids). In this review, we primarily summarize the recent advancements of the LNP mRNA delivery technology, focusing on the structures of four lipid constituents and their biomedical applications. We delve into structure-activity relationships of the lipids, while also exploring the future prospects and challenges in developing more efficacious mRNA delivery systems. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Biology-Inspired Nanomaterials > Lipid-Based Structures Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Nanoplatform-Based In Vivo Gene Delivery Systems for Cancer Therapy

Gene therapy uses modern molecular biology methods to repair disease-causing genes. As a burgeoning therapeutic, it has been widely applied for cancer therapy. Since 1989, there have been numerous clinical gene therapy cases worldwide. However, a few are successful. The main challenge of clinical gene therapy is the lack of efficient and safe vectors. Although viral vectors show high transfection efficiency, their application is still limited by immune rejection and packaging capacity. Therefore, the development of non-viral vectors is overwhelming. Nanoplatform-based non-viral vectors become a hotspot in gene therapy. The reasons are mainly as follows. 1) Non-viral vectors can be engineered to be uptaken by specific types of cells or tissues, providing effective targeting capability. 2) Non-viral vectors can protect goods that need to be delivered from degradation. 3) Nanoparticles can transport large-sized cargo such as CRISPR/Cas9 plasmids and nucleoprotein complexes. 4) Nanoparticles are highly biosafe, and they are not mutagenic in themselves compared to viral vectors. 5) Nanoparticles are easy to scale preparation, which is conducive to clinical conversion and application. Here, an overview of the categories of nanoplatform-based non-viral gene vectors, the limitations on their development, and their applications in cancer therapy.

Growth factors and growth factor gene therapies for treating chronic wounds

Chronic wounds are an unmet clinical need affecting millions of patients globally, and current standards of care fail to consistently promote complete wound closure and prevent recurrence. Disruptions in growth factor signaling, a hallmark of chronic wounds, have led researchers to pursue growth factor therapies as potential supplements to standards of care. Initial studies delivering growth factors in protein form showed promise, with a few formulations reaching clinical trials and one obtaining clinical approval. However, protein-form growth factors are limited by instability and off-target effects. Gene therapy offers an alternative approach to deliver growth factors to the chronic wound environment, but safety concerns surrounding gene therapy as well as efficacy challenges in the gene delivery process have prevented clinical translation. Current growth factor delivery and gene therapy approaches have primarily used single growth factor formulations, but recent efforts have aimed to develop multi-growth factor approaches that are better suited to address growth factor insufficiencies in the chronic wound environment, and these strategies have demonstrated improved efficacy in preclinical studies. This review provides an overview of chronic wound healing, emphasizing the need and potential for growth factor therapies. It includes a summary of current standards of care, recent advances in growth factor, cell-based, and gene therapy approaches, and future perspectives for multi-growth factor therapeutics.

mRNA therapies: Pioneering a new era in rare genetic disease treatment

Rare genetic diseases, often referred to as orphan diseases due to their low prevalence and limited treatment options, have long posed significant challenges to our medical system. In recent years, Messenger RNA (mRNA) therapy has emerged as a highly promising treatment approach for various diseases caused by genetic mutations. Chemically modified mRNA is introduced into cells using carriers like lipid-based nanoparticles (LNPs), producing functional proteins that compensate for genetic deficiencies. Given the advantages of precise dosing, biocompatibility, transient expression, and minimal risk of genomic integration, mRNA therapies can safely and effectively correct genetic defects in rare diseases and improve symptoms. Currently, dozens of mRNA drugs targeting rare diseases are undergoing clinical trials. This comprehensive review summarizes the progress of mRNA therapy in treating rare genetic diseases. It introduces the development, molecular design, and delivery systems of mRNA therapy, highlighting their research progress in rare genetic diseases based on protein replacement and gene editing. The review also summarizes research progress in various rare disease models and clinical trials. Additionally, it discusses the challenges and future prospects of mRNA therapy. Researchers are encouraged to join this field and collaborate to advance the clinical translation of mRNA therapy, bringing hope to patients with rare genetic diseases.

Design, synthesis, and in vitro gene transfer efficacy of novel ionizable cholesterol derivatives

ABSTACTThe medicinal properties of genetic drugs are highly dependent on the design of delivery systems. Ionizable cationic lipids are considered core materials in delivery systems. However, there has not yet been a widespread consensus on the relationship between the wide diversity of lipid structure design and gene delivery efficiency. The aims of the research work were to synthesize ionizable cholesterol derivatives (iChol-lipids) and to evaluate their potential applications as gene delivery vector. A series of iChol-lipids with different head groups were synthesized with carbamate bond spacer. The chemical structures were characterized by 1H NMR, MS, melting range, and pKa. The interactions between iChol-lipids and MALAT1-siRNA were studied by molecular dynamics simulations and compared with market available DC-Chol, which revealed that hydrogen bonds, salt-bridge, and electrostatic interaction were probably involved. The self-assemble behaviors of these lipids were intensively investigated and evaluated by dynamic laser scattering in the presence of different helper lipids and PEGylated lipids. Their plasmid binding ability, transfection efficiency, hemolytic toxicity, and cytotoxicity were fully studied. IZ-Chol-LNPs was proved to be highly potential to effectively complex with DNA, and endosome escape mechanisms mediated by proton sponge effect was verified by pH-sensitive fluorescence probe BCFL.

Impact of Linker Groups on Self-Assembly, Gene Transfection, Antibacterial Activity, and In Vitro Cytotoxicity of Cationic Bolaamphiphiles

Cationic bolaamphiphiles have gained significant attention in various research fields, including materials science, drug delivery, and gene therapy, due to their unique properties and potential applications. The objective of the current research is to develop more effective cationic bolaamphiphiles. Thus, we have designed and synthesized two cationic bolaamphiphiles (-(CH2)12(2,3-dihydroxy-N,N-dimethyl-N-(3-ureidopropyl)propan-1-aminium chloride))2 (C12(DDUPPAC)2)) and (-(CH2)12(N-(3-(carbamoyloxy)propyl)-2,3-dihydroxy-N,N-dimethylpropan-1-aminium chloride)2 (C12(CPDDPAC)2) containing urea and urethane linkages, respectively. We have investigated their self-assembly properties in water using several techniques, including surface tension, electrical conductivity, fluorescence probe, calorimetry, dynamic light scattering, and atomic force microscopy. Their biological applications, e.g., in vitro gene transfection, antibacterial activity, and cytotoxicity, were studied. Both bolaamphiphiles were observed to produce aggregates larger than spherical micelles above a relatively low critical aggregation concentration (cac). The calorimetric experiments suggested the thermodynamically favorable spontaneous aggregation of both bolaforms in water. The results of interaction studies led to the conclusion that C12(CPDDPAC)2 binds DNA with a greater affinity than C12(DDUPPAC)2. Also, C12(CPDDPAC)2 is found to act as a more efficient gene transfection vector than C12(DDUPPAC)2 in 264.7 cell lines. The in vitro cytotoxicity assay using MTT, however, revealed that neither of the bolaamphiphiles was toxic, even at higher quantities. Additionally, both bolaforms show beneficial antibacterial activity.

Chemistry and Art of Developing Lipid Nanoparticles for Biologics Delivery: Focus on Development and Scale-Up

Lipid nanoparticles (LNPs) have gained prominence as primary carriers for delivering a diverse array of therapeutic agents. Biological products have achieved a solid presence in clinical settings, and the anticipation of creating novel variants is increasing. These products predominantly encompass therapeutic proteins, nucleic acids and messenger RNA. The advancement of efficient LNP-based delivery systems for biologics that can overcome their limitations remains a highly favorable formulation strategy. Moreover, given their small size, biocompatibility, and biodegradation, LNPs can proficiently transport therapeutic moiety into the cells without significant toxicity and adverse reactions. This is especially crucial for the existing and upcoming biopharmaceuticals since large molecules as a group present several challenges that can be overcome by LNPs. This review describes the LNP technology for the delivery of biologics and summarizes the developments in the chemistry, manufacturing, and characterization of lipids used in the development of LNPs for biologics. Finally, we present a perspective on the potential opportunities and the current challenges pertaining to LNP technology.

CRISPR-Cas9 Engineered Extracellular Vesicles for the Treatment of Dominant Progressive Hearing Loss

Clinical translation of gene therapy has been challenging, due to limitations in current delivery vehicles such as traditional viral vectors. Herein, we report the use of gRNA:Cas9 ribonucleoprotein (RNP) complexes engineered extracellular vesicles (EVs) for in vivo gene therapy. By leveraging a novel high-throughput microfluidic droplet-based electroporation system (μDES), we achieved 10-fold enhancement of loading efficiency and more than 1000-fold increase in processing throughput on loading RNP complexes into EVs (RNP-EVs), compared with conventional bulk electroporation. The flow-through droplets serve as enormous bioreactors for offering millisecond pulsed, low-voltage electroporation in a continuous-flow and scalable manner, which minimizes the Joule heating influence and surface alteration to retain natural EV stability and integrity. In the Shaker-1 mouse model of dominant progressive hearing loss, we demonstrated the effective delivery of RNP-EVs into inner ear hair cells, with a clear reduction of Myo7ash1 mRNA expression compared to RNP-loaded lipid-like nanoparticles (RNP-LNPs), leading to significant hearing recovery measured by auditory brainstem responses (ABR).

MC3/SAINT-O-Somes, a novel liposomal delivery system for efficient and safe delivery of siRNA into endothelial cells

Increased understanding of chronic inflammatory diseases and the role of endothelial cell (EC) activation herein, have urged interest in sophisticated strategies to therapeutically intervene in activated EC to treat these diseases. Liposome-mediated delivery of therapeutic siRNA in inflammation-activated EC is such a strategy. In this study, we describe the design and characterisation of two liposomal siRNA delivery systems formulated with the cationic MC3 lipid or MC3/SAINT mixed lipids, referred to as MC3-O-Somes (MOS) and MC3/SAINT-O-Somes (MSS). The two formulations showed comparable physicochemical properties, except for better siRNA encapsulation efficiency in the MSS formulation. Antibody-mediated VCAM-1 targeting (AbVCAM-1) increased the association of the targeted MOS and MSS with activated EC, although the targeted MOS showed a significantly higher VCAM-1 specific association than the targeted MSS. AbVCAM-1 MSS containing RelA siRNA achieved significant downregulation of RelA expression, while AbVCAM-1 MOS containing RelA siRNA did not downregulate RelA expression in activated EC. Additionally, AbVCAM-1 MSS containing RelA siRNA showed low cytotoxicity in EC and at the same time prohibited endothelial inflammatory activation by reducing expression of cell adhesion molecules. The AbVCAM-1 MSS formulation is a novel siRNA delivery system based on a combination of the cationic lipids MC3 and SAINT, that shows good physicochemical characteristics, enhanced endothelial cell association, improved transfection activity, low toxicity and significant anti-inflammatory effect, thereby complying with the requirements for future in vivo investigations.

Delivery of gene editing therapeutics

For the past decades, gene editing demonstrated the potential to attenuate each of the root causes of genetic, infectious, immune, cancerous, and degenerative disorders. More recently, Clustered Regularly Interspaced Short Palindromic Repeats-CRISPR-associated protein 9 (CRISPR-Cas9) editing proved effective for editing genomic, cancerous, or microbial DNA to limit disease onset or spread. However, the strategies to deliver CRISPR-Cas9 cargos and elicit protective immune responses requires safe delivery to disease targeted cells and tissues. While viral vector-based systems and viral particles demonstrate high efficiency and stable transgene expression, each are limited in their packaging capacities and secondary untoward immune responses. In contrast, the nonviral vector lipid nanoparticles were successfully used for as vaccine and therapeutic deliverables. Herein, we highlight each available gene delivery systems for treating and preventing a broad range of infectious, inflammatory, genetic, and degenerative diseases. STATEMENT OF SIGNIFICANCE: CRISPR-Cas9 gene editing for disease treatment and prevention is an emerging field that can change the outcome of many chronic debilitating disorders.

Gene Delivery into T-Cells Using Ternary Complexes of DNA, Lipofectamine, and Carboxy-Terminal Phenylalanine-Modified Dendrimers

T-cells play critical roles in various immune reactions, and genetically engineered T-cells have attracted attention for the treatment of cancer and autoimmune diseases. Previously, it is shown that a polyamidoamine dendrimer of generation 4 (G4), modified with 1,2-cyclohexanedicarboxylic anhydride (CHex) and phenylalanine (Phe) (G4-CHex-Phe), is useful for delivery into T-cells and their subsets. In this study, an efficient non-viral gene delivery system is constructed using this dendrimer. Ternary complexes are prepared using different ratios of plasmid DNA, Lipofectamine, and G4-CHex-Phe. A carboxy-terminal dendrimer lacking Phe (G3.5) is used for comparison. These complexes are characterized using agarose gel electrophoresis, dynamic light scattering, and ζpotential measurements. In Jurkat cells, the ternary complex with G4-CHex-Phe at a P/COOH ratio of 1/5 shows higher transfection activity than other complexes, such as binary and ternary complexes with G3.5, without any significant cytotoxicity. The transfection efficiency of the G4-CHex-Phe ternary complexes decreases considerably in the presence of free G4-CHex-Phe and upon altering the complex preparation method. These results suggest that G4-CHex-Phe promotes the cellular internalization of the complexes, which is useful for gene delivery into T-cells.

Dual-Targeted Therapy in HER2-Overexpressing Breast Cancer with Trastuzumab and Novel Cholesterol-Based Nioplexes Silencing Mcl-1

The challenge in HER2-overexpressing breast cancer therapy lies in creating an effective target therapy to overcome treatment resistance. Monoclonal antibodies and target gene silencing by siRNA are two potential strategies that have been widely developed for treating HER2-positive breast cancer. The siRNA delivery system is a crucial factor that influences siRNA therapy's success. In this study, lipid-based nanoparticles (cationic niosomes) composed of different cholesterol-based cationic lipids were formulated and characterized for delivering siRNA into HER2-overexpressing breast cancer cells. Niosomes containing a trimethylammonium headgroup showed the highest siRNA delivery efficiency with low toxicity. The myeloid cell leukemia-1 (Mcl-1) siRNA nioplex treatment significantly decreased mRNA expression and breast cancer cell growth. Dual-targeted therapy, consisting of treatment with an Mcl-1 siRNA nioplex and trastuzumab (TZ) solution, noticeably promoted cell-growth inhibition and apoptosis. The synergistic effect of dual therapy was also demonstrated by computer modeling software (CompuSyn version 1.0). These findings suggest that the developed cationic niosomes were effective nanocarriers for siRNA delivery in breast cancer cells. Furthermore, the Mcl-1 nioplex/TZ dual treatment establishes a synergistic outcome that may have the potential to treat HER2-overexpressing breast cancer.

Self-Assembly, In Vitro Gene Transfection, and Antimicrobial Activity of Biodegradable Cationic Bolaamphiphiles

Bolaamphiphiles or bolaforms have drawn particular interest in drug and gene delivery, and studies of bolaforms have been growing continuously. Bolaforms, due to their unique structure, exhibit specific self-assembly behavior in water. The present work aims to develop biodegradable cationic bolaforms with a better gene transfection ability. In this work, a novel cationic bolaform (Bola-1) with head groups bearing hydroxyl (OH) functionality was designed and synthesized to investigate self-assembly and gene transfection efficiency. The self-assembly behavior of Bola-1 in water was compared with that of the hydrochloride salt (Bola-2) of its precursor molecule to investigate the effect of the -OH functionality on their solution properties. Several techniques, including surface tension, electrical conductivity, fluorescence probe, calorimetry, dynamic light scattering, and atomic force microscopy, were employed for the physicochemical characterization of Bola-1 and Bola-2. Despite the presence of polar urea groups in the spacer chain, both bolaforms were found to form spherical or elongated micelles above a relatively low critical aggregation concentration (CAC). The presence of the OH group was found to significantly affect the CAC value. The results of calorimetric measurements suggested a thermodynamically favorable aggregate formation in salt-free water. Despite stronger binding efficiency with calf thymus DNA, in vitro gene transfection studies performed using adherent cell Hek 293 suggested that both Bola-1 and Bola-2 have gene transfection efficiency comparable to that of turbofectamine standard. Both bolaforms were found to exhibit significant in vitro cytotoxicity at higher concentrations. Also, the bolaforms showed beneficial antibacterial activity at higher concentrations.

Multicomponent Lipid Nanoparticles for RNA Transfection

Despite the wide variety of available cationic lipid platforms for the delivery of nucleic acids into cells, the optimization of their composition has not lost its relevance. The purpose of this work was to develop multi-component cationic lipid nanoparticles (LNPs) with or without a hydrophobic core from natural lipids in order to evaluate the efficiency of LNPs with the widely used cationic lipoid DOTAP (1,2-dioleoyloxy-3-[trimethylammonium]-propane) and the previously unstudied oleoylcholine (Ol-Ch), as well as the ability of LNPs containing GM3 gangliosides to transfect cells with mRNA and siRNA. LNPs containing cationic lipids, phospholipids and cholesterol, and surfactants were prepared according to a three-stage procedure. The average size of the resulting LNPs was 176 nm (PDI 0.18). LNPs with DOTAP mesylate were more effective than those with Ol-Ch. Core LNPs demonstrated low transfection activity compared with bilayer LNPs. The type of phospholipid in LNPs was significant for the transfection of MDA-MB-231 and SW 620 cancer cells but not HEK 293T cells. LNPs with GM3 gangliosides were the most efficient for the delivery of mRNA to MDA-MB-231 cells and siRNA to SW620 cells. Thus, we developed a new lipid platform for the efficient delivery of RNA of various sizes to mammalian cells.

Biodegradable Cationic and Ionizable Cationic Lipids: A Roadmap for Safer Pharmaceutical Excipients

Cationic and ionizable cationic lipids are broadly applied as auxiliary agents, but their use is associated with adverse effects. If these excipients are rapidly degraded to endogenously occurring metabolites such as amino acids and fatty acids, their toxic potential can be minimized. So far, synthesized and evaluated biodegradable cationic and ionizable cationic lipids already showed promising results in terms of functionality and safety. Within this review, an overview about the different types of such biodegradable lipids, the available building blocks, their synthesis and cleavage by endogenous enzymes is provided. Moreover, the relationship between the structure of the lipids and their toxicity is described. Their application in drug delivery systems is critically discussed and placed in context with the lead compounds used in mRNA vaccines. Moreover, their use as preservatives is reviewed, guidance for their design is provided, and an outlook on future developments is given.

DOTAP: Structure, hydration, and the counterion effect

The cationic lipid 1,2-dioleoyl-3-trimethylammonium propane (DOTAP) is one of the original synthetic cationic lipids used for the liposomal transfection of oligonucleotides in gene therapy. The key structural element of DOTAP is its quaternary ammonium headgroup that is responsible for interactions with both nucleic acids and target cell membranes. Because these interactions are fundamental to the design of a major class of transfection lipids, it is important to understand the structure of DOTAP and how it interacts with halide counterions. Here, we use x-ray and neutron diffraction techniques to examine the structure of DOTAP and how chloride (Cl-) and iodide (I-) counterions alter the hydration properties of the DOTAP headgroup. A problem of particular interest is the poor solubility of DOTAP/I- in water solutions. Our results show that the poor solubility results from very tight binding of the I- counterion to the headgroup and the consequent expulsion of water. The structural principles we report here are important for assessing the suitability of DOTAP and its quaternary ammonium derivatives for transfection.

In vitro transfection efficiencies of T-shaped spermine-based cationic lipids with identical and nonidentical tails under high serum conditions

T-shaped spermine-based cationic lipids with identical and nonidentical hydrophobic tails having variable carbon lengths (from C10 to C18) were designed and synthesized. These lipids were characterized, and their structure-activity relationships were determined for DNA binding and transfection ability of these compounds when formulated as cationic liposomes. These liposomes were then applied as non-viral vectors to transfect HEK293T, HeLa, PC3, H460, HepG2, and Calu'3 cell lines with plasmid DNA encoding the green fluorescent protein. ST9, ST12 and ST13 with nonidentical tails could deliver DNA into HEK293T cells up to 60% under serum-free conditions. The lipid ST15 bearing nonidentical tails was found to be a potent gene transfer agent under 40% serum conditions in HEK293T and HeLa cells. Besides their low cytotoxicity, these lipoplexes also exhibited greater transfection efficiency than the commercially available transfection agent, Lipofectamine 3000.

GSH-Activatable Aggregation-Induced Emission Cationic Lipid for Efficient Gene Delivery

The key to gene therapy is the design of biocompatible and efficient delivery systems. In this work, a glutathione (GSH)-activated aggregation-induced-emission (AIE) cationic amphiphilic lipid, termed QM-SS-KK, was prepared for nonviral gene delivery. QM-SS-KK was composed of a hydrophilic biocompatible lysine tripeptide headgroup, a GSH-triggered disulfide linkage, and a hydrophobic AIE fluorophore QM-OH (QM: quinoline-malononitrile) tail. The peptide moiety could not only efficiently compact DNA but also well modulate the dispersion properties of QM-SS-KK, leading to the fluorescence-off state before GSH treatment. The cleavage of disulfide in QM-SS-KK by GSH generated AIE signals in situ with a tracking ability. The liposomes consisted of QM-SS-KK, and 1,2-dioleoylphosphatidylethanolamine (DOPE) (QM-SS-KK/DOPE) delivered plasmid DNAs (pDNAs) into cells with high efficiency. In particular, QM-SS-KK/DOPE had an enhanced transfection efficiency (TE) in the presence of 10% serum, which was two times higher than that of the commercial transfection agent PEI25K. These results highlighted the great potential of peptide and QM-based fluorescence AIE lipids for gene delivery applications.

Potential of siRNA in COVID-19 therapy: Emphasis on in silico design and nanoparticles based delivery

Small interfering RNA (siRNA)-mediated mRNA degradation approach have imparted its eminence against several difficult-to-treat genetic disorders and other allied diseases. Viral outbreaks and resulting pandemics have repeatedly threatened public health and questioned human preparedness at the forefront of drug design and biomedical readiness. During the recent pandemic caused by the SARS-CoV-2, mRNA-based vaccination strategies have paved the way for a new era of RNA therapeutics. RNA Interference (RNAi) based approach using small interfering RNA may complement clinical management of the COVID-19. RNA Interference approach will primarily work by restricting the synthesis of the proteins required for viral replication, thereby hampering viral cellular entry and trafficking by targeting host as well as protein factors. Despite promising benefits, the stability of small interfering RNA in the physiological environment is of grave concern as well as site-directed targeted delivery and evasion of the immune system require immediate attention. In this regard, nanotechnology offers viable solutions for these challenges. The review highlights the potential of small interfering RNAs targeted toward specific regions of the viral genome and the features of nanoformulations necessary for the entrapment and delivery of small interfering RNAs. In silico design of small interfering RNA for different variants of SARS-CoV-2 has been discussed. Various nanoparticles as promising carriers of small interfering RNAs along with their salient properties, including surface functionalization, are summarized. This review will help tackle the real-world challenges encountered by the in vivo delivery of small interfering RNAs, ensuring a safe, stable, and readily available drug candidate for efficient management of SARS-CoV-2 in the future.

Development of a spermine lipid for transient antibody expression

Transient expression is the only way to quickly obtain a small scale of antibodies for biomedical research and therapeutic evaluation. The agents for transfecting the suspension cells, e.g. PEI or commercial agents, either lack efficiency or excessively expensive. Herein, a novel spermine-based lipid was developed and fabricated into a cationic liposome for antibody expression. This new transfection agent, designated as sperminoliposome, is feasible, cheap, and highly effective to produce antibodies. Compared to PEI, a 3 times higher yield of antibody was obtained by sperminoliposome during the transient expression of cetuximab in suspension 293F cells. Characterizations confirmed that the expressed antibody is fully functional and eligible for further research. Our study provides an effective tool for the rapid production of antibodies economically and feasibly.

Recent Advance of Liposome Nanoparticles for Nucleic Acid Therapy

Gene therapy, as an emerging therapeutic approach, has shown remarkable advantages in the treatment of some major diseases. With the deepening of genomics research, people have gradually realized that the emergence and development of many diseases are related to genetic abnormalities. Therefore, nucleic acid drugs are gradually becoming a new boon in the treatment of diseases (especially tumors and genetic diseases). It is conservatively estimated that the global market of nucleic acid drugs will exceed $20 billion by 2025. They are simple in design, mature in synthesis, and have good biocompatibility. However, the shortcomings of nucleic acid, such as poor stability, low bioavailability, and poor targeting, greatly limit the clinical application of nucleic acid. Liposome nanoparticles can wrap nucleic acid drugs in internal cavities, increase the stability of nucleic acid and prolong blood circulation time, thus improving the transfection efficiency. This review focuses on the recent advances and potential applications of liposome nanoparticles modified with nucleic acid drugs (DNA, RNA, and ASO) and different chemical molecules (peptides, polymers, dendrimers, fluorescent molecules, magnetic nanoparticles, and receptor targeting molecules). The ability of liposome nanoparticles to deliver nucleic acid drugs is also discussed in detail. We hope that this review will help researchers design safer and more efficient liposome nanoparticles, and accelerate the application of nucleic acid drugs in gene therapy.

Recent advances in nanotechnology approaches for non-viral gene therapy

Gene therapy has shown great potential in the treatment of many diseases by downregulating the expression of certain genes. The development of gene vectors as a vehicle for gene therapy has greatly facilitated the widespread clinical application of nucleic acid materials (DNA, mRNA, siRNA, and miRNA). Currently, both viral and non-viral vectors are used as delivery systems of nucleic acid materials for gene therapy. However, viral vector-based gene therapy has several limitations, including immunogenicity and carcinogenesis caused by the exogenous viral vectors. To address these issues, non-viral nanocarrier-based gene therapy has been explored for superior performance with enhanced gene stability, high treatment efficiency, improved tumor-targeting, and better biocompatibility. In this review, we discuss various non-viral vector-mediated gene therapy approaches using multifunctional biodegradable or non-biodegradable nanocarriers, including polymer-based nanoparticles, lipid-based nanoparticles, carbon nanotubes, gold nanoparticles (AuNPs), quantum dots (QDs), silica nanoparticles, metal-based nanoparticles and two-dimensional nanocarriers. Various strategies to construct non-viral nanocarriers based on their delivery efficiency of targeted genes will be introduced. Subsequently, we discuss the cellular uptake pathways of non-viral nanocarriers. In addition, multifunctional gene therapy based on non-viral nanocarriers is summarized, in which the gene therapy can be combined with other treatments, such as photothermal therapy (PTT), photodynamic therapy (PDT), immunotherapy and chemotherapy. We also provide a comprehensive discussion of the biological toxicity and safety of non-viral vector-based gene therapy. Finally, the present limitations and challenges of non-viral nanocarriers for gene therapy in future clinical research are discussed, to promote wider clinical applications of non-viral vector-based gene therapy.

Reducible amino acid based cationic lipids with a naphthalimide moiety as non-viral gene vehicles

Three basic amino acid–based cationic lipids bearing a fluorescent naphthalimide moiety and a reducible disulfide linkage are synthesized and applied as non-viral gene vehicles. Their DNA interactions are investigated by agarose-gel retardant and ethidium bromide replacement assays. The sizes and zeta potentials of the liposome/DNA complexes are measured by dynamic light scattering. The cytotoxicities of the liposome/DNA complexes are examined using HeLa and 7702 cell lines by MTT assays. The glutathione-responsive DNA release process is studied through time-dependent fluorescence assays. Luciferase gene expression showed the transfection efficiency of the liposome is dramatically increased in the presence of 10% serum. Confocal laser scanning microscopy studies corroborated that the liposome/DNA complexes are successfully uptaken into HeLa cells. These results demonstrate the promising use of amino acids and naphthalimide-containing lipids for safe and efficient gene delivery.

A critical overview of current progress for COVID-19: development of vaccines, antiviral drugs, and therapeutic antibodies

The novel coronavirus disease (COVID-19) pandemic remains a global public health crisis, presenting a broad range of challenges. To help address some of the main problems, the scientific community has designed vaccines, diagnostic tools and therapeutics for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. The rapid pace of technology development, especially with regard to vaccines, represents a stunning and historic scientific achievement. Nevertheless, many challenges remain to be overcome, such as improving vaccine and drug treatment efficacies for emergent mutant strains of SARS-CoV-2. Outbreaks of more infectious variants continue to diminish the utility of available vaccines and drugs. Thus, the effectiveness of vaccines and drugs against the most current variants is a primary consideration in the continual analyses of clinical data that supports updated regulatory decisions. The first two vaccines granted Emergency Use Authorizations (EUAs), BNT162b2 and mRNA-1273, still show more than 60% protection efficacy against the most widespread current SARS-CoV-2 variant, Omicron. This variant carries more than 30 mutations in the spike protein, which has largely abrogated the neutralizing effects of therapeutic antibodies. Fortunately, some neutralizing antibodies and antiviral COVID-19 drugs treatments have shown continued clinical benefits. In this review, we provide a framework for understanding the ongoing development efforts for different types of vaccines and therapeutics, including small molecule and antibody drugs. The ripple effects of newly emergent variants, including updates to vaccines and drug repurposing efforts, are summarized. In addition, we summarize the clinical trials supporting the development and distribution of vaccines, small molecule drugs, and therapeutic antibodies with broad-spectrum activity against SARS-CoV-2 strains.

pH-sensitive, tail-modified, ester-linked ionizable cationic lipids for gene delivery

Ionizable cationic lipids have great potential for gene delivery, yet the effect of the molecular structure of such lipids on gene delivery efficiency is an ongoing research challenge. To better understand corresponding structure-function activity relationships, we synthesized four ester-linked, pH-responsive, ionizable cationic lipids. The screened DEDM4 lipid, containing 2-ethylenedimethylamine in the headgroup and a branched-chain tail, exhibited a high delivery efficacy of plasmid DNA and siRNA in A549 cells, which was comparable with that of the commercial reagent lipofectamine 3000 (lipo3000). Moreover, because of its pK_a value of 6.35 and pH-sensitivity under acidic conditions, DEDM4 could carry sufficient positive charge in the acidic environment of endosomes and interact with the endosome lumen, leading to destruction of the endomembrane and subsequent release of siRNA into the cytoplasm with endosomal escape. Furthermore, we used DEDM4 to deliver IGF-1R siRNA to induce cancer cell apoptosis, thereby leading to great tumor inhibition. More importantly, it also showed very low toxicity in vivo. These structure-activity data for DEDM4 demonstrate potential clinical applications of DEDM4-mediated gene delivery for cancer.

A Quality by Design Approach in Pharmaceutical Development of Non-Viral Vectors with a Focus on miRNA

Cancer is the leading cause of death worldwide. Tumors consist of heterogeneous cell populations that have different biological properties. While conventional cancer therapy such as chemotherapy, radiotherapy, and surgery does not target cancer cells specifically, gene therapy is attracting increasing attention as an alternative capable of overcoming these limitations. With the advent of gene therapy, there is increasing interest in developing non-viral vectors for genetic material delivery in cancer therapy. Nanosystems, both organic and inorganic, are the most common non-viral vectors used in gene therapy. The most used organic vectors are polymeric and lipid-based delivery systems. These nanostructures are designed to bind and protect the genetic material, leading to high efficiency, prolonged gene expression, and low toxicity. Quality by Design (QbD) is a step-by-step approach that investigates all the factors that may affect the quality of the final product, leading to efficient pharmaceutical development. This paper aims to provide a new perspective regarding the use of the QbD approach for improving the quality of non-viral vectors for genetic material delivery and their application in cancer therapy.

Towards the future exploration of mucosal mRNA vaccines against emerging viral diseases; lessons from existing next-generation mucosal vaccine strategies

The mRNA vaccine platform has offered the greatest potential in fighting the COVID-19 pandemic owing to rapid development, effectiveness, and scalability to meet the global demand. There are many other mRNA vaccines currently being developed against different emerging viral diseases. As with the current COVID-19 vaccines, these mRNA-based vaccine candidates are being developed for parenteral administration via injections. However, most of the emerging viruses colonize the mucosal surfaces prior to systemic infection making it very crucial to target mucosal immunity. Although parenterally administered vaccines would induce a robust systemic immunity, they often provoke a weak mucosal immunity which may not be effective in preventing mucosal infection. In contrast, mucosal administration potentially offers the dual benefit of inducing potent mucosal and systemic immunity which would be more effective in offering protection against mucosal viral infection. There are however many challenges posed by the mucosal environment which impede successful mucosal vaccination. The development of an effective delivery system remains a major challenge to the successful exploitation of mucosal mRNA vaccination. Nonetheless, a number of delivery vehicles have been experimentally harnessed with different degrees of success in the mucosal delivery of mRNA vaccines. In this review, we provide a comprehensive overview of mRNA vaccines and summarise their application in the fight against emerging viral diseases with particular emphasis on COVID-19 mRNA platforms. Furthermore, we discuss the prospects and challenges of mucosal administration of mRNA-based vaccines, and we explore the existing experimental studies on mucosal mRNA vaccine delivery.

Evaluation of pentaerythritol-based and trimethylolpropane-based cationic lipidic materials for gene delivery

The chemical and physical structure of cationic liposomes pays an important effect on their gene transfection efficiency. Investigation on the structure-function relationship of cationic liposomes will guide the design of novel cationic liposomes with high transfection efficiency and biosafety. In this paper, two novel series of lipids based on the backbone of pentaerythritol and trimethylolpropane were discovered, and their gene transfection efficiencies were assayed in vitro. The four lipids 8c, 9c, 14b, and 15b, exhibited much better transfection efficiency in the HEK293 cell lines compared with Lipo2000, lipid 9c also showed good transfection efficiency in the SW480 cell lines. And the structure-efficiency relationship revealed that a hydroxyethyl polar head group boosted transfer potency in trimethylolpropane-type lipids, but reduced in pentaerythritol-type lipids.

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.

Influence of Hydrophobicity in the Hydrophilic Region of Cationic Lipids on Enhancing Nucleic Acid Delivery and Gene Editing

Intracellular delivery of biomolecules using non-viral vectors critically depends on the vectors' ability to allow the escape and release of the contents from the endosomes. Prior findings demonstrated that aromatic/hydrophobic group-containing amino acids such as phenylalanine (F) and tryptophan (W) destabilize cellular membranes by forming pores in the lipid bilayer. Taking cues from these findings, we have developed four α-tocopherol-based cationic amphiphiles by varying the aromatic/hydrophobic amino acids such as glycine (G), proline (P), phenylalanine (F), and tryptophan (W) as head groups and triazole in the linker region to study their impact on endosomal escape for the enhanced transfection efficacy. The lipids tocopherol-triazole-phenylalanine (TTF) and tocopherol-triazole-tryptophan (TTW) exhibited similar potential to commercial transfecting reagents, Lipofectamine (LF) 3000 and Lipofectamine Messenger Max (LFMM), respectively, in transfecting plasmid DNA and messenger RNA in multiple cultured cell lines. The TTW liposome was also found to be effective in delivering Cas9 mRNA and demonstrated equal efficiency of gene editing AAVS1 locus compared to LFMM in CHO, Neuro-2a, and EA.HY926 cell lines. In this current investigation, it is shown that the synthesized cationic lipids with aromatic hydrophobic R group-containing amino acids are safe, economic, and actually more efficient in nucleic acid delivery and genome-editing applications. These findings can be further explored in the genome-editing approach for treating genetic disorders.

Structure-activity relationships of pH-responsive and ionizable lipids for gene delivery

Ionizable lipids are the leading vectors for gene therapy. Understanding the effects of molecular structure on efficient gene delivery is one of the most important challenges for maximizing the utility of such lipid vectors. We synthesized an array of pH-responsive and ionizable lipids to investigate the relationship between lipid structure and activity. The optimized lipid (EDM) has double tertiary amines in the headgroup and an ester linker. EDM exhibited efficient DNA and siRNA delivery to, and gene silencing of, A549 cells. EDM has a pK_a value of 6.67, which enabled it to quickly escape from the endosome after entering the cell; the ester linkages rapidly degraded and enabled gene release into the cytoplasm. EDM also delivered IGF-1R siRNA to inhibit tumor growth and induce cancer cell apoptosis by efficient inhibition of IGF-1R expression in mice. Our study on the structure-activity relationships of ionizable lipids will facilitate clinical applications.

Chitosan-Crosslinked Low Molecular Weight PEI-Conjugated Iron Oxide Nanoparticle for Safe and Effective DNA Delivery to Breast Cancer Cells

Breast cancer has attracted tremendous research interest in treatment development as one of the major threats to public health. The use of non-viral carriers for therapeutic DNA delivery has shown promise in treating various cancer types, including breast cancer, due to their high DNA loading capacity, high cell transfection efficiency, and design versatility. However, cytotoxicity and large sizes of non-viral DNA carriers often raise safety concerns and hinder their applications in the clinic. Here we report the development of a novel nanoparticle formulation (termed NP-Chi-xPEI) that can safely and effectively deliver DNA into breast cancer cells for successful transfection. The nanoparticle is composed of an iron oxide core coated with low molecular weight (800 Da) polyethyleneimine crosslinked with chitosan via biodegradable disulfide bonds. The NP-Chi-xPEI can condense DNA into a small nanoparticle with the overall size of less than 100 nm and offer full DNA protection. Its biodegradable coating of small-molecular weight xPEI and mildly positive surface charge confer extra biocompatibility. NP-Chi-xPEI-mediated DNA delivery was shown to achieve high transfection efficiency across multiple breast cancer cell lines with significantly lower cytotoxicity as compared to the commercial transfection agent Lipofectamine 3000. With demonstrated favorable physicochemical properties and functionality, NP-Chi-xPEI may serve as a reliable vehicle to deliver DNA to breast cancer cells.

Metallohelix vectors for efficient gene delivery via cationic DNA nanoparticles

The design of efficient and safe gene delivery vehicles remains a major challenge for the application of gene therapy. Of the many reported gene delivery systems, metal complexes with high affinity for nucleic acids are emerging as an attractive option. We have discovered that certain metallohelices-optically pure, self-assembling triple-stranded arrays of fully encapsulated Fe-act as nonviral DNA delivery vectors capable of mediating efficient gene transfection. They induce formation of globular DNA particles which protect the DNA from degradation by various restriction endonucleases, are of suitable size and electrostatic potential for efficient membrane transport and are successfully processed by cells. The activity is highly structure-dependent-compact and shorter metallohelix enantiomers are far less efficient than less compact and longer enantiomers.

Optimization of phospholipid chemistry for improved lipid nanoparticle (LNP) delivery of messenger RNA (mRNA)

Lipid nanoparticles (LNPs) have been established as an essential platform for nucleic acid delivery. Efforts have led to the development of vaccines that protect against SARS-CoV-2 infection using LNPs to deliver messenger RNA (mRNA) coding for the viral spike protein. Out of the four essential components that comprise LNPs, phospholipids represent an underappreciated opportunity for fundamental and translational study. We investigated this avenue by systematically modulating the identity of the phospholipid in LNPs with the goal of identifying specific moieties that directly enhance or hinder delivery efficacy. Results indicate that phospholipid chemistry can enhance mRNA delivery by increasing membrane fusion and enhancing endosomal escape. Phospholipids containing phosphoethanolamine (PE) head groups likely increase endosomal escape due to their fusogenic properties. Additionally, it was found that zwitterionic phospholipids mainly aided liver delivery, whereas negatively charged phospholipids changed the tropism of the LNPs from liver to spleen. These results demonstrate that the choice of phospholipid plays a role intracellularly by enhancing endosomal escape, while also driving organ tropism in vivo. These findings were then applied to Selective Organ Targeting (SORT) LNPs to manipulate and control spleen-specific delivery. Overall, selection of the phospholipid in LNPs provides an important handle to design and optimize LNPs for improved mRNA delivery and more effective therapeutics.

Physical-Chemical Characterization of Bilayer Membranes Derived from (±) α-Tocopherol-Based Gemini Lipids and Their Interaction with Phosphatidylcholine Bilayers and Lipoplex Formation with Plasmid DNA

Membrane formation and aggregation properties of two series of (±) α-tocopherol-based cationic gemini lipids without and with hydroxyl functionalities at the headgroup region (TnS n = 3, 4, 5, 6, 8, and 12; THnS n = 4, 5, 6, 8, and 12) with varying polymethylene spacer lengths were investigated extensively while comparing with the corresponding properties of the monomeric counterparts (TM and THM). Liposomal suspensions of each cationic lipid were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), zeta potential measurements, and small-angle X-ray diffraction studies. The length of the spacer and the presence of hydroxyl functionalities at the headgroup region strongly contribute to the aggregation behavior of these gemini lipids in water. The interaction of each tocopherol lipid with a model phospholipid, 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC)-derived vesicles, was thoroughly examined by differential scanning calorimetry (DSC) and 1,6-diphenyl-1,3,5-hexatriene (DPH)-doped fluorescence anisotropy measurements. The binding efficiency of the cationic tocopherol liposomes with plasmid DNA (pDNA) was followed by an ethidium bromide (EB) exclusion assay and zeta potential measurements, whereas negatively charged micellar sodium dodecyl sulfate (SDS)-mediated release of the pDNA from various preformed pDNA-liposomal complexes (lipoplex) was studied by an ethidium bromide (EB) reintercalation assay. The structural transformation of pDNA upon complexation with liposome was characterized using circular dichroism (CD) spectroscopic measurements. Gemini lipid-pDNA interactions depend on both the presence of hydroxyl functionalities at the headgroups and the length of the spacer chain between the headgroups. Succinctly, we performed a detailed physical-chemical characterization of the membranes formed from cationic monomeric and gemini lipids bearing tocopherol as their hydrophobic backbone and describe the role of inserting the -OH group at the headgroup of such lipids.

Serum Compatible Spermine-based Cationic Lipids with Non-identical Hydrocarbon Tails Mediate High Transfection Efficiency

Cationic lipids are widely used as non-viral synthetic vectors for gene delivery as a safer alternative to viral vectors. In this work, a library of L-shaped spermine-based cationic lipids with identical and non-identical hydrophobic chains having variable carbon length (from C10 to C18) was designed and synthesized. These lipids were characterized and the structure-activity relationships of these compounds were determined for DNA binding and transfection ability when formulated as cationic liposomes. The liposomes were then used successfully for the transfection of HEK293T, HeLa, PC3, H460, HepG2, SH-SY5Y and Calu'3 cell lines. The transfection efficiency of lipids with non-identical hydrocarbon chains was greater than the identical analog. These reagents exhibited superior efficiency to the commercial reagent, Lipofectamine3000, under both serum-free and 10-40% serum conditions in HEK293T, HeLa and H460 cell lines. The lipids were also not toxic to the tested cells. The results suggested that L-shaped spermine-based cationic lipids with non-identical hydrocarbon tails could serve as an efficient and safe non-viral vector gene carrier for further in vivo studies.

Ginsenoside as a new stabilizer enhances the transfection efficiency and biocompatibility of cationic liposome

Nucleic acid drugs have emerged as important therapeutics but their clinical application has been greatly limited by their large molecular weight, high polarity, negative charge and short half-life. Cationic liposomes (CLs) have gained wide attention as non-viral vectors for nucleic acid delivery. However, the absolute transfection efficiency of CLs can still be enhanced while their cytotoxicity should be decreased simultaneously. Ginsenosides, obtained from natural plants, possess a similar steroid structure to cholesterol and might be an alternative to cholesterol for acting as a membrane stabilizer of CLs. Herein, seven kinds of ginsenoside-based compounds were utilized to prepare CLs (GCLs) and their efficacy in siRNA delivery was investigated. The particle sizes of the GCLs were 90-300 nm and the siRNA delivery efficiencies were in the range of 23.6%-78.4%. Rg5-based CLs (Rg5-CLs) exhibited the highest transfection efficiency of 81% and the lowest toxicity, with 82% cell viability obtained even at high concentrations. Ginsenosides are shown as promising biomaterials as membrane stabilizers of CLs. Rg5-CLs have been demonstrated as efficient non-viral vectors with high transfection efficiency and good biocompatibility for gene delivery, possessing great potential for gene therapy.

Liposomal nanoparticles based on steroids and isoprenoids for nonviral gene delivery

Natural lipid molecules are an essential part of life as they constitute the membrane of cells and organelle. In most of these cases, the hydrophobicity of natural lipids is contributed by alkyl chains. Although natural lipids with a nonfatty acid hydrophobic backbone are quite rare, steroids and isoprenoids have been strong candidates as part of a lipid. Over the years, these natural molecules (steroid and isoprenoids) have been used to make either lipid-based nanoparticle or functionalize in such a way that it could form nano assembly alone for therapeutic delivery. Here we mainly focus on the synthetic functionalized version of these natural molecules which forms cationic liposomal nanoparticles (LipoNPs). These cationic LipoNPs were further used to deliver various negatively charged genetic materials in the form of pDNA, siRNA, mRNA (nucleic acids), and so on. This article is categorized under: Biology-Inspired Nanomaterials > Lipid-Based Structures.

Lipids and Lipid Derivatives for RNA Delivery

RNA-based therapeutics have shown great promise in treating a broad spectrum of diseases through various mechanisms including knockdown of pathological genes, expression of therapeutic proteins, and programmed gene editing. Due to the inherent instability and negative-charges of RNA molecules, RNA-based therapeutics can make the most use of delivery systems to overcome biological barriers and to release the RNA payload into the cytosol. Among different types of delivery systems, lipid-based RNA delivery systems, particularly lipid nanoparticles (LNPs), have been extensively studied due to their unique properties, such as simple chemical synthesis of lipid components, scalable manufacturing processes of LNPs, and wide packaging capability. LNPs represent the most widely used delivery systems for RNA-based therapeutics, as evidenced by the clinical approvals of three LNP-RNA formulations, patisiran, BNT162b2, and mRNA-1273. This review covers recent advances of lipids, lipid derivatives, and lipid-derived macromolecules used in RNA delivery over the past several decades. We focus mainly on their chemical structures, synthetic routes, characterization, formulation methods, and structure-activity relationships. We also briefly describe the current status of representative preclinical studies and clinical trials and highlight future opportunities and challenges.

Correlation between Biophysical Properties of Niosomes Elaborated with Chloroquine and Different Tensioactives and Their Transfection Efficiency

Lipid nanocarriers, such as niosomes, are considered attractive candidates for non-viral gene delivery due to their suitable biocompatibility and high versatility. In this work, we studied the influence of incorporating chloroquine in niosomes biophysical performance, as well as the effect of non-ionic surfactant composition and protocol of incorporation in their biophysical performance. An exhaustive comparative evaluation of three niosome formulations differing in these parameters was performed, which included the analysis of their thermal stability, rheological behavior, mean particle size, dispersity, zeta potential, morphology, membrane packing capacity, affinity to bind DNA, ability to release and protect the genetic material, buffering capacity and ability to escape from artificially synthesized lysosomes. Finally, in vitro biological studies were, also, performed in order to determine the compatibility of the formulations with biological systems, their transfection efficiency and transgene expression. Results revealed that the incorporation of chloroquine in niosome formulations improved their biophysical properties and the transfection efficiency, while the substitution of one of the non-ionic surfactants and the phase of addition resulted in less biophysical variations. Of note, the present work provides several biophysical parameters and characterization strategies that could be used as gold standard for gene therapy nanosystems evaluation.

Chitosan Oleate Coated PLGA Nanoparticles as siRNA Drug Delivery System

Oligonucleotide therapeutics such as miRNAs and siRNAs represent a class of molecules developed to modulate gene expression by interfering with ribonucleic acids (RNAs) and protein synthesis. These molecules are characterized by strong instability and easy degradation due to nuclease enzymes. To avoid these drawbacks and ensure efficient delivery to target cells, viral and non-viral vectors are the two main approaches currently employed. Viral vectors are one of the major vehicles in gene therapy; however, the potent immunogenicity and the insertional mutagenesis is a potential issue for the patient. Non-viral vectors, such as polymeric nanocarriers, provide a safer and more efficient delivery of RNA-interfering molecules. The aim of this work is to employ PLGA core nanoparticles shell-coated with chitosan oleate as siRNA carriers. An siRNA targeted on HIV-1, directed against the viral Tat/Rev transcripts was employed as a model. The ionic interaction between the oligonucleotide's moieties, negatively charged, and the positive surface charges of the chitosan shell was exploited to associate siRNA and nanoparticles. Non-covalent bonds can protect siRNA from nuclease degradation and guarantee a good cell internalization and a fast release of the siRNA into the cytosolic portion, allowing its easy activation.

Delivery of small interfering RNAs by nanovesicles for cancer therapy

Small interfering ribonucleic acids (siRNAs) are originally recognized as an intermediate of the RNA interference (RNAi) pathway. They can inhibit or silence various cellular pathways by knocking down specific messenger RNA molecules. In cancer cells, siRNAs can suppress the expression of several multidrug-resistant genes, leading to the increased deposition of chemotherapeutic drugs at the tumor site. siRNA therapy can be used to selectively increase apoptosis of cancer cells or activate an immune response to the cancer. However, delivering siRNAs to the targeted location is the main limitation in achieving safe and effective delivery of siRNAs. This review highlights some representative examples of nonviral delivery systems, especially nanovesicles such as exosomes, liposomes, and niosomes. Nanovesicles can improve the delivery of siRNAs by increasing their intracellular delivery, and they have demonstrated excellent potential for cancer therapy. This review focuses on recent discoveries of siRNA targets for cancer therapy and the use of siRNAs to successfully silence these targets. In addition, this review summarizes the recent progress in designing nanovesicles (liposomes or niosomes) for siRNA delivery to cancer cells and the effects of a combination of anticancer drugs and siRNA therapy in cancer therapy.

Gemini Lipopeptide Bearing an Ultrashort Peptide for Enhanced Transfection Efficiency and Cancer-Cell-Specific Cytotoxicity

Cationic gemini lipopeptides are a relatively new class of amphiphilic compounds to be used for gene delivery. Through the possibility of incorporating short peptides with cell-penetrating functionalities, these lipopeptides may be advantageous over traditional cationic lipids. Herein, we report the design, synthesis, and application of a novel cationic gemini lipopeptide for gene delivery. An ultrashort peptide, containing four amino acids, arginine-cysteine-cysteine-arginine, serves as a cationic head group, and two α-tocopherol moieties act as hydrophobic anchoring groups. The new lipopeptide (ATTA) is incorporated into the conventional liposomes, containing 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) and 1,2-dioleoyl-sn-glycerol-3-phosphoethanolamine (DOPE), at different molar ratios. The formulated liposomes are characterized and screened for better transfection efficiency. Transfection activity in multiple human cell lines from cancerous and noncancerous origins indicates that the inclusion of an optimal ratio of ATTA in the liposomes substantially enhances the transfection efficiency, superior to that of a traditional liposome, DOTAP-DOPE. Cytotoxicity of ATTA-containing formulations against multiple cell lines indicates potentially distinct activity between cancer and noncancer cell lines. Furthermore, lipoplexes of the ATTA-containing formulations with anticancer therapeutic gene, plasmid encoding tumor necrosis factor-related apoptosis-inducing ligand (pTRAIL), induce obviously more cytotoxicity than conventional formulations. The results indicate that arginine-rich cationic lipopeptide appears to be a promising ingredient in gene delivery vector formulations to enhance transfection efficiency and cell-selective cytotoxicity.

Key considerations in formulation development for gene therapy products

Gene therapy emerged as an important area of research and led to the success of multiple product approvals in the clinic. The number of clinical trials for this class of therapeutics is expected to grow over the next decade. Gene therapy products are complex and heterogeneous, employ different types of vectors and are susceptible to degradation. The product development process for commercially viable gene-based pharmaceuticals remains challenging. In this review, challenges, stability, and drug product formulation development strategies using viral or non-viral vectors, as well as accelerated regulatory approval pathways for gene therapy products are discussed.

Cationic Liposomes as Vectors for Nucleic Acid and Hydrophobic Drug Therapeutics

Cationic liposomes (CLs) are effective carriers of a variety of therapeutics. Their applications as vectors of nucleic acids (NAs), from long DNA and mRNA to short interfering RNA (siRNA), have been pursued for decades to realize the promise of gene therapy, with approvals of the siRNA therapeutic patisiran and two mRNA vaccines against COVID-19 as recent milestones. The long-term goal of developing optimized CL-based NA carriers for a broad range of medical applications requires a comprehensive understanding of the structure of these vectors and their interactions with cell membranes and components that lead to the release and activity of the NAs within the cell. Structure-activity relationships of lipids for CL-based NA and drug delivery must take into account that these lipids act not individually but as components of an assembly of many molecules. This review summarizes our current understanding of how the choice of the constituting lipids governs the structure of their CL-NA self-assemblies, which constitute distinct liquid crystalline phases, and the relation of these structures to their efficacy for delivery. In addition, we review progress toward CL-NA nanoparticles for targeted NA delivery in vivo and close with an outlook on CL-based carriers of hydrophobic drugs, which may eventually lead to combination therapies with NAs and drugs for cancer and other diseases.