Novel imidazole-functionalized cyclen cationic lipids: Synthesis and application as non-viral gene vectors

Trehalose-polyamine/DNA nanocomplexes: impact of vector architecture on cell and organ transfection selectivity

A novel family of precision-engineered gene vectors with well-defined structures built on trehalose and trehalose-based macrocycles (cyclotrehalans) comprising linear or cyclic polyamine heads have been synthesized through procedures that exploit click chemistry reactions. The strategy was conceived to enable systematic structural variations and, at the same time, ensuring that enantiomerically pure vectors are obtained. Notably, changes in the molecular architecture translated into topological differences at the nanoscale upon co-assembly with plasmid DNA, especially regarding the presence of regions with short- or long-range internal order as observed by TEM. In vitro and in vivo experiments further evidenced a significant impact on cell and organ transfection selectivity. Altogether, the results highlight the potential of trehalose-polyamine/pDNA nanocomplex monoformulations to achieve targeting transfection without the need for any additional cell- or organ-sorting component.

Lipid nanovehicles overcome barriers to systemic RNA delivery: Lipid components, fabrication methods, and rational design

Lipid nanovehicles are currently the most advanced vehicles used for RNA delivery, as demonstrated by the approval of patisiran for amyloidosis therapy in 2018. To illuminate the unique superiority of lipid nanovehicles in RNA delivery, in this review, we first introduce various RNA therapeutics, describe systemic delivery barriers, and explain the lipid components and methods used for lipid nanovehicle preparation. Then, we emphasize crucial advances in lipid nanovehicle design for overcoming barriers to systemic RNA delivery. Finally, the current status and challenges of lipid nanovehicle-based RNA therapeutics in clinical applications are also discussed. Our objective is to provide a comprehensive overview showing how to utilize lipid nanovehicles to overcome multiple barriers to systemic RNA delivery, inspiring the development of more high-performance RNA lipid nanovesicles in the future.

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.

Targeted Liposomes: A Nonviral Gene Delivery System for Cancer Therapy

Cancer is the second most frequent cause of death worldwide, with 28.4 million new cases expected for 2040. Despite de advances in the treatment, it remains a challenge because of the tumor heterogenicity and the increase in multidrug resistance mechanisms. Thus, gene therapy has been a potential therapeutic approach owing to its ability to introduce, silence, or change the content of the human genetic code for inhibiting tumor progression, angiogenesis, and metastasis. For the proper delivery of genes to tumor cells, it requires the use of gene vectors for protecting the therapeutic gene and transporting it into cells. Among these vectors, liposomes have been the nonviral vector most used because of their low immunogenicity and low toxicity. Furthermore, this nanosystem can have its surface modified with ligands (e.g., antibodies, peptides, aptamers, folic acid, carbohydrates, and others) that can be recognized with high specificity and affinity by receptor overexpressed in tumor cells, increasing the selective delivery of genes to tumors. In this context, the present review address and discuss the main targeting ligands used to functionalize liposomes for improving gene delivery with potential application in cancer treatment.

Lipophilic Polyamines as Promising Components of Liposomal Gene Delivery Systems

Gene therapy requires an effective and safe delivery vehicle for nucleic acids. In the case of non-viral vehicles, including cationic liposomes, the structure of compounds composing them determines the efficiency a lot. Currently, cationic amphiphiles are the most frequently used compounds in liposomal formulations. In their structure, which is a combination of hydrophobic and cationic domains and includes spacer groups, each component contributes to the resulting delivery efficiency. This review focuses on polycationic and disulfide amphiphiles as prospective cationic amphiphiles for gene therapy and includes a discussion of the mutual influence of structural components.

Cationic lipids for gene delivery: many players, one goal

Lipid-based carriers represent the most widely used alternative to viral vectors for gene expression and gene silencing purposes. This class of non-viral vectors is particularly attractive for their ease of synthesis and chemical modifications to endow them with desirable properties. Despite combinatorial approaches have led to the generation of a large number of cationic lipids displaying different supramolecular structures and improved behavior, additional effort is needed towards the development of more and more effective cationic lipids for transfection purposes. With this review, we seek to highlight the great progress made in the design of each and every constituent domain of cationic lipids, that is, the chemical structure of the headgroup, linker and hydrophobic moieties, and on the specific effect on the assembly with nucleic acids. Since the complexity of such systems is known to affect their performances, the role of formulation, stability and phase behavior on the transfection efficiency of such assemblies will be thoroughly discussed. Our objective is to provide a conceptual framework for the development of ever more performing lipid gene delivery vectors.

Zn-Promoted gene transfection efficiency for non-viral vectors: a mechanism study

Mechanism studies revealed that a Zn coordination to cyclen-based cationic polymer may effectively improve the buffering capacity and endosomal escape ability.

Zinc(ii)-cyclen coordinative amphiphiles for enhanced gene delivery

In this study, we developed coordinative amphiphiles for use as novel non-viral DNA vectors. As a modification of a conventional cationic lipid structure, we replaced the cationic head with a zinc(ii)-1,4,7,10-tetraazacyclododecane (Zn-cyclen) complex as a phosphate-directing group, and used biocompatible skeletons (α-tocopherol or cholesterol) as hydrophobic tails. The structure-activity relationship (SAR) was systematically investigated to study the effect of Zn-coordination on the gene transfection between cyclen-based traditional head-tail lipids and Zn(ii)-cyclen coordinative amphiphiles. The results reveal that both Zn-free lipids and Zn-containing amphiphiles could condense DNA into nano-sized particles with appropriate size and zeta-potentials. Agarose gel retardation assay and MTS-based cell viability assays demonstrated that the Zn(ii)-cyclen complex exhibited slightly lower DNA binding ability and much lower cytotoxicity compared to liposome analogues, respectively. Most importantly, in vitro transfection studies showed that the coordination of zinc(ii) to cyclen may dramatically increase the transfection efficiency of the conventional cationic lipid, and α-tocopherol-containing coordinative amphiphile Zn-Cyc-Toc gives the best transfection efficiency, which was enhanced 24.4 times after coordination and was 6.1 times higher than commercial transfection reagent lipofectamine 2000. Mechanism studies confirmed that the DNA complex formed from Zn-Cyc-Toc might induce higher cellular uptake and better endosomal escape ability than the lipoplexes formed from Zn-free lipid Cyc-Toc. This study not only demonstrates that these coordinative amphiphiles might be promising non-viral gene vectors, but also presents a novel strategy to enhance the gene transfection efficiency and biocompatibility of cyclen-based cationic lipids.

Zn-coordination could dramatically enhance the gene transfection efficiency and reduce the cytotoxicity of conventional cyclen-based cationic liposomes.

Cationic cholesterol derivative efficiently delivers the genes: in silico and in vitro studies

The aims of the research work were to synthesize ethyl(cholesteryl carbamoyl)-L-arginate (ECCA), an arginine-conjugated cholesterol derivative, and to evaluate its application as a gene delivery vector. The interactions of ECCA with DNA duplex were studied using molecular dynamics (MD) simulations. It was found that the guanidine group of ECCA could interact with the phosphate group of DNA through ionic interactions as well as hydrogen bonds. The structure of DNA was stable throughout the simulation time. Liposomes were formulated using ECCA and soya phosphatidylcholine (SPC) by a thin-film hydration method. They had the particle size of ~ 150 nm and the zeta potential of + 51 mV. To ensure the efficient binding of DNA to the liposomes, the ratio of DNA to ECCA was optimized using gel retardation assay. Further, serum stability, haemolysis and cytotoxicity studies were carried out to determine the stability and safety of the lipoplexes. Circular dichroism spectroscopy was used to determine the interaction of DNA and cationic liposomes. Cellular uptake pathway was determined by studying the uptake of coumarin-loaded lipoplexes at 4 °C and in the presence of uptake inhibitors, i.e. genistein, chlorpromazine and methyl-β-cyclodextrin. Transfection studies were carried out to evaluate the transfection efficacy of the ECCA-loaded lipoplexes. The binding of DNA and lipoplexes was found to be stable in the presence of serum, and no degradation of DNA was observed. The lipoplexes showed low haemolysis and cytotoxicity. The uptake of coumarin-loaded liposomes was decreased up to ~ 20% in the presence of clathrin- and caveola-mediated uptake inhibitors, indicating a role of both the pathways in the uptake of the inhibitors. Satisfactory transfection efficiency was obtained compared to Lipofectamine^®. Thus, cationic cholesterol derivative is a useful tool for gene delivery vector.

Zn(ii) coordination to cyclen-based polycations for enhanced gene delivery

Zn²⁺ coordination greatly improved the gene transfection efficiency of cyclen-based polycations.

Functionalized Asymmetric Bola-Type Amphiphiles for Efficient Gene and Drug Delivery

The studies of bolaamphiphile-based nanoparticles as delivery vectors are still rudimentary and under development. In this study, several asymmetric bolaamphiphiles containing lysine and another moiety with special functions, such as pH-sensitive or cell-targeting property, were designed and synthesized. The potentials of these bolaamphiphile-based nanoparticles as versatile vectors for both nucleic acids and chemical drugs were studied. With the presence of 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), these amphiphiles could be prepared into bolasomes, which showed good DNA binding ability and could condense plasmid DNA into nanoparticles with appropriate size and surface potential. Lys-His, which has a pH-sensitive histidine on one head, exhibited higher transfection efficiency than the symmetric counterpart and comparable efficiency to commercially available transfection reagent. Mechanism studies confirmed that the bolaplexes formed from Lys-His might induce the highest cellular uptake and the best endosomal escape ability. On the other hand, these bolaamphiphiles also exhibited good drug loading ability. The self-assembly vesicles could efficiently encapsulate the hydrophobic anti-cancer drug doxorubicin (DOX) in aqueous solution with high drug loading content and encapsulation efficiency. Confocal laser scanning microscopy (CLSM) experiment and cell viability assay exhibited a controlled release of the drug with the assistance of bolasomes. It was shown that such bolaamphiphiles have great potential as nano-vectors for both drug and gene or their co-delivery.

pH and reduction dual-responsive dipeptide cationic lipids with α-tocopherol hydrophobic tail for efficient gene delivery

A series of tocopherol-based cationic lipid 3a-3f bearing a pH-sensitive imidazole moiety in the dipeptide headgroup and a reduction-responsive disulfide linkage were designed and synthesized. Acid-base titration of these lipids showed good buffering capacities. The liposomes formed from 3 and co-lipid 1, 2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) could efficiently bind and condense DNA into nanoparticles. Gel binding and HPLC assays confirmed the encapsulated DNA could release from lipoplexes 3 upon addition of 10 mM glutathione (GSH). MTT assays in HEK 293 cells demonstrated that lipoplexes 3 had low cytotoxicity. The in vitro gene transfection studies showed cationic dipeptide headgroups clearly affected the transfection efficiency (TE), and arginine-histidine based dipeptide lipid 3f give the best TE, which was 30.4 times higher than Lipofectamine 3000 in the presence of 10% serum. Cell-uptake assays indicated that basic amino acid containing dipeptide cationic lipids exhibited more efficient cell uptake than serine and aromatic amino acids based dipeptide lipids. Confocal laser scanning microscopy (CLSM) studies corroborated that 3 could efficiently deliver and release DNA into the nuclei of HeLa cells. These results suggest that tocopherol-based dipeptide cationic lipids with pH and reduction dual-sensitive characteristics might be promising non-viral gene delivery vectors.

1,8-naphthalimide modified [12]aneN₃ compounds as selective and sensitive probes for Cu²⁺ ions and ATP in aqueous solution and living cells

A new fluorescent probe 1 featuring one 1,8-naphthalimide and two [12]aneN3 units was synthesized. In the presence of Cu(2+) ions, the fluorescence emission of 1 was quenched by a factor of 127-fold and no interference by other metal ions was observed under physiological conditions. By means of titration and a Job's plot it was established that 1 forms a complex with Cu(2+) ions in a 1:2 ratio. The fluorescence of the 1-Cu(2+) complex was recovered by the addition of Adenosine-5'-triphosphate (ATP) in aqueous solution. Due to its low cytotoxicity, good water solubility, and high sensitivity, probe 1 was successfully applied in the sequential recognition of Cu(2+) and ATP in aqueous solution and HeLa cells. The highly selective and sensitive ability of 1-Cu(2+) complex to detect ATP even enables its bio-analytical applications in real-time imaging in living cells.

Structure–activity relationship studies of symmetrical cationic bolasomes as non-viral gene vectors

Bolalipids based on lysine or cyclen headgroups were synthesized and their structure–activity relationship as gene delivery vectors was studied.

Next generation macrocyclic and acyclic cationic lipids for gene transfer: Synthesis and in vitro evaluation

Previously we reported the synthesis and in vitro evaluation of four novel, short-chain cationic lipid gene delivery vectors, characterized by acyclic or macrocyclic hydrophobic regions composed of, or derived from, two 7-carbon chains. Herein we describe a revised synthesis of an expanded library of related cationic lipids to include extended chain analogues, their formulation with plasmid DNA (pDNA) and in vitro delivery into Chinese hamster ovarian (CHO-K1) cells. The formulations were evaluated against each other based on structural differences in the hydrophobic domain and headgroup. Structurally the library is divided into four sets based on lipids derived from two 7- or two 11-carbon hydrophobic chains, C7 and C11 respectively, which possess either a dimethylamine or a trimethylamine derived headgroup. Each set includes four cationic lipids based on an acyclic or macrocyclic, saturated or unsaturated hydrophobic domain. All lipids were co-formulated with the commercial cationic lipid 1,2-dimyristoyl-sn-glycero-3-ethylphosphocholine (EPC) in a 1:1 molar ratio, along with one of two distinct neutral co-lipids, cholesterol or 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) in an overall cationic-to-neutral lipid molar ratio of 3:2. Binding of lipid formulations with DNA, and packing morphology associated with the individual lipid-DNA complexes were characterized by gel electrophoresis and small angle X-ray diffraction (SAXD), respectively. As a general trend, lipoplex formulations based on mismatched binary cationic lipids, composed of a shorter C7 lipid and the longer lipid EPC (C14), were generally associated with higher transfection efficiency and lower cytotoxicity than their more closely matched C11/EPC binary lipid formulation counterparts. Furthermore, the cyclic lipids gave transfection levels as high as or greater than their acyclic counterparts, and formulations with cholesterol exhibited higher transfection and lower cytotoxicity than those formulated with DOPE. A number of the lipid formulations with cholesterol as co-lipid performed as well as, or better than Lipofectamine 2000™ and EPC, the two positive controls employed in these studies. These results suggest that our novel cyclic and acyclic cationic lipid vectors are effective nonviral gene transfer agents that warrant further investigation.

Enabling cytoplasmic delivery and organelle targeting by surface modification of nanocarriers

Nanocarriers are designed to specifically accumulate in diseased tissues. In this context, targeting of intracellular compartments was shown to enhance the efficacy of many drugs and to offer new and more effective therapeutic approaches. This is especially true for therapies based on biologicals that must be encapsulated to favor cell internalization, and to avoid intracellular endosomal sequestration and degradation of the payload. In this review, we discuss specific surface modifications designed to achieve cell cytoplasm delivery and to improve targeting of major organelles; we also discuss the therapeutic applications of these approaches. Last, we describe some integrated strategies designed to sequentially overcome the biological barriers that separate the site of administration from the cell cytoplasm, which is the drug's site of action.

Cyclen-based cationic lipids containing a pH-sensitive moiety as gene delivery vectors

Imidazole-functionalized cationic lipids with a cyclen headgroup were synthesized, and the structure–activity relationship in gene delivery mediated by these lipids was discussed.

Small cyclen-imidazolium-containing molecules and their interactions with DNA

Three small organic molecules containing different numbers of cyclen and imidazolium units were synthesized. Their interactions with plasmid DNA and their potential for gene delivery vectors were investigated. Agarose gel retardation and ethidium bromide exclusion assays revealed that these molecules can effectively condense DNA, and compounds with higher molecular weights are needed to lower w/w ratio for full condensation. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) indicated that these compounds may form nanosized spherical particles with DNA. Furthermore, the complex formed from 10, i.e., 10/DNA, can partially release DNA from compact state at a relatively higher concentration of NaCl (200 mM). In the presence of the lipid 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), 10 could transfer plasmid DNA into BEL-7402 cells. In addition, these compounds exhibited much lower cytotoxicity than PEI 25 kDa.

Synthesis and gene transfection activity of cyclen-based cationic lipids with asymmetric acyl-cholesteryl hydrophobic tails

Novel cyclen-based cationic lipids with asymmetric acyl-cholesteryl hydrophobic tails were synthesized and applied as non-viral gene vectors.

Cationic gemini lipids with cyclen headgroups: interaction with DNA and gene delivery abilities

Eleven Gemini cationic lipids and one mono counterpart were synthesized, and their structure–activity relationship as non-viral gene vectors was studied.

Serum-resistant complex nanoparticles functionalized with imidazole-rich polypeptide for gene delivery to pulmonary metastatic melanoma

To enhance serum-resistance and overcome the lysosomal barrier are effective and feasible strategies to increase the transfection efficiency of non-viral gene delivery system. For the systemic delivery of therapeutic gene, we previously developed self-assemble carboxymethyl poly(l-histidine) (CM-PLH)/poly(β-amino ester) (PbAE)/pDNA ternary complex nanoparticles based on electrostatic coating as an effective pDNA carrier. Recharging cationic PbAE/pDNA polyplexes with CM-PLH was a promising method to reduce the cytotoxicity and enhance the stability in vivo of positive charged polyplexes. In the present study, the transfection activities of ternary complex nanoparticles were further evaluated in vitro and in vivo. The transfection efficiency of ternary complex nanoparticles showed significant serum-resistance (CM-PLH-containing (51.9±4.35)% in 50% FBS>CM-PLH-free (14.7±5.66)% in 50% FBS), cell line dependent (HEK293>MCF-7>COS7>B16F10>A549>Hela>SPC-A1>CHO>SKOV3) and incubation period dependent (24 h, 20 h, 16 h>12 h>8 h>4 h>2 h>1 h>0.5 h). After transfected with ternary complex nanoparticles loading pGV240-MDA-7/IL-24, the B16F10 cells exhibited significant apoptosis and proliferation inhibition due to the expression of IL-24. Moreover, in the pulmonary metastatic melanoma model, ternary complex nanoparticles loading pGV240-MDA-7/IL-24 showed significant antitumor therapeutic efficacy in vivo. These results suggested that CM-PLH/PbAE/pDNA ternary complex nanoparticles were promising and challenging gene vector for practical application.