Cationic lipids from multi-component Passerini reaction for non-viral gene delivery: A structure-activity relationship study

Although many types of cationic lipids have been developed as efficient gene vectors, the construction of lipid molecules with simple procedures remains challenging. Passerini reaction, as a classic multicomponent reaction, could directly give the α-acyloxycarboxamide products with biodegradable ester and amide bonds. Herein, two series of novel cationic lipids with heterocyclic pyrrolidine and piperidine as headgroups were synthesized through Passerini reaction (P-series) and amide condensation (A-series), and relevant structure-activity relationships on their gene delivery capability was studied. It was found that although both of the two series of lipids could form lipid nanoparticles (LNPs) which could effectively condense DNA, the LNP derived from P-series lipids showed higher transfection efficiency, serum tolerance, cellular uptake, and lower cytotoxicity. Unlike the A-series LNPs, the P-series LNPs showed quite different structure-activity relationship, in which the relative site of the secondary amine had significant effect on the transfection performance. The othro-isomers of the P-series lipids had lower cytotoxicity, but poor transfection efficiency, which was probably due to their unstable nature. Taken together, this study not only validated the feasibility of Passerini reaction for the construction of cationic lipids for gene delivery, but also afforded some clues for the rational design of effective non-viral lipidic gene vectors.

Organic Phase-Soluble Nanomagnetically Cationic Phospholipid: Synthesis, Characterization, and In Vitro Transfection Activity

The presented work describes the synthesis and characterization of a novel magnetic cationic phospholipid (MCP) system with a stable dopamine anchor as well as its transfection activity study. The synthesized architectural system increases the biocompatibility of iron oxide and promises applications of magnetic nanoparticles in living cells. The MCP system is soluble in organic solvents and can be easily adapted to prepare magnetic liposomes. We created complexes with liposomes containing MCP and other functional cationic lipids and pDNA as gene delivery tools, which possessed the ability to enhance the efficiency of transfection, particularly the process of interaction with cells by inducing a magnetic field. The MCP is able to create iron oxide nanoparticles and has the potential for the materials to prepare the system for site-specific gene delivery with the application of an external magnetic field.

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.

mRNA Lipoplexes with Cationic and Ionizable α-Amino-lipophosphonates: Membrane Fusion, Transfection, mRNA Translation and Conformation

Cationic liposomes are attractive carriers for mRNA delivery. Here, mRNA lipoplexes (LX) were prepared with the cationic lipids α-aminolipophosphonate (3b) or imidazolium lipophosphoramidate (2) associated with various α-aminolipophosphonates co-lipids comprising protonable groups (imidazole or pyridine) and DOPE. Physicochemical parameters of liposomes and their membrane fusion activity were measured. LXs comprising either 3b- or 2- allowed transfection of ~25% and 40% of dendritic cells with low cytotoxicity, respectively; the efficiency increased up to 80% when 2 was combined with the imidazole-based co-lipid 1. The transfections were high with 3b/1, 3b/DOPE, 2/1 and 2/DOPE LXs. We observed that the transfection level was not well correlated with the acid-mediated membrane fusion activity of liposomes supposed to destabilize endosomes. The mRNA release from LXs and its translation capacity after release were studied for the most efficient LXs. The results showed that the more mRNA was condensed, the poorer the translation efficiency after release was. In contrast to DNA, circular dichroism performed on mRNA complexed with 2/DOPE revealed the presence of denatured mRNA in LXs explaining this lack of translation efficiency. This is an important parameter that should be stressed for the preparation of mRNA LXs with a conserved mRNA translation activity.

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.

Cancer Stem Cell-Targeted Gene Delivery Mediated by Aptamer-Decorated pH-Sensitive Nanoliposomes

A new pH-responsive cationic co-liposomal formulation was prepared in this study using the twin version of the amphiphile palmitoyl homocysteine, TPHC; natural zwitterionic lipid, DOPE; and cholesterol-based twin cationic lipid, C5C, at specified molar ratios. This co-liposome was further decorated with a newly designed fluorescently tagged, cholesterol-tethered EpCAM-targeting RNA aptamer for targeted gene delivery. This aptamer-guided nanoliposomal formulation, C5C/DOPE/TPHC at 8:24:1 molar ratio, could efficiently transport the genes in response to low pH of cellular endosomes selectively to the EpCAM overexpressing cancer stem cells. This particular observation was extended using siRNA against GFP to validate their transfection capabilities in response to EpCAM expression. Overall, the aptamer-guided nanoliposomal formulation was found to be an excellent transfectant for in vitro siRNA gene delivery.

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.

Effects of sucrose ester structures on liposome-mediated gene delivery

Sucrose esters (SEs) have great potential applications in gene delivery because of their low toxicity, excellent biocompatibility, and biodegradability. By using tripeptide-based lipid (CDO) as a model lipid and SEs as helper lipids, a series of liposomes were prepared. The SEs with hydrophilic-lipophilic balance (HLB) values of 1, 6, 11, or 16 and the fatty acids of laurate, stearate, or oleate were used in the liposomes. We investigated the effect of HLB values of SEs and fatty acid types on gene transfection efficiency and toxicity of liposomes. The results showed that transfection efficiencies of the liposomes containing SEs with HLB value of 6 were superior to other liposomes in HeLa, MCF-7, NCI-H460, and A549 tumor cells. For the same HLB value, liposomes of laurate SEs were preferable to transfect cells compared to SEs of stearate and oleate. The liposomes with SEs showed higher cellular uptake than liposome without SEs (LipoCDO). LipoL12-6/Luc-siRNA treatment on tumor-bearing mice exhibited about 60% in vivo gene silencing of luciferase, and LipoL12-6 could mediate IGF-1R siRNA to greatly inhibit tumor growth. Moreover, liposomes with SEs revealed remarkably low toxicity in vitro and in vivo. The illustration of SE structures on gene delivery will promote the use of SEs for clinical trials of liposomes.

STATEMENT OF SIGNIFICANCE

This article is the first to study the effects of various chain lengths and hydrophilic-lipophilic balance (HLB) of sucrose esters (SEs) on gene transfection efficiency and safety of liposomes for gene delivery. The in vitro delivery of pDNA and siRNA by lipoplexes against HeLa, MCF-7, NCI-H460, and A549 tumor cells showed that the lipoplexes could lead to better transfection and lower cytotoxicity after the addition of SEs. SEs with shorter chain and a median HLB value could provide the liposomes with much higher gene transfection efficiency than others. The in vivo delivery of siRNA to tumor-bearing mice further confirmed that liposome containing laurate SE (LipoL12-6) could be a potential therapeutic vector, as it delivered siRNA to silence nearly 60% of the luciferase in tumors and also greatly inhibited the tumor growth. Therefore, the addition of SEs to liposomes proved to be relatively safe in vitro and in vivo. These preliminary results demonstrated that SEs show great potential for constructing controlled-release systems for gene delivery. The readers will get insights into a series of gene vectors and deepen their understanding about gene delivery.

A reduction-responsive liposomal nanocarrier with self-reporting ability for efficient gene delivery

In the past few decades, although various reduction-responsive nanocarriers have been designed and explored for gene delivery, it is difficult to directly detect or monitor the reduction capability of these carriers, especially under intracellular conditions. Taking advantage of the generated fluorescence signal in the reduction process of the naphthalimide-sulfonamide (NS) group, we developed a novel liposomal nanocarrier, FNSL, which showed reduction-sensitive property and self-reporting character. As a new reduction-responsive site in a gene delivery system, the NS group in FNSL is capable of responding to glutathione (GSH) and simultaneously emitting green fluorescence at 500 nm in both extra- and intracellular circumstances. Hence, it will be very convenient to assess the reducibility of this carrier and monitor the stimuli-responsive gene release via fluorescence signal. FNSL has high affinity for DNA and can condense it into nanoparticles with a proper nano-size and zeta potential. Compared with the non-reducible FNAL, FNSL showed enhanced gene release capability, higher transfection efficiency (TE), and lower cytotoxicity. Furthermore, treatment of FNSL-mediated transfection with slightly exogenous GSH greatly improved the TE of FNSL in HepG2 cells, and its TE was even higher than that of Lipofectamine 2000. These results demonstrate that FNSL possesses great potential for efficient and low-toxicity gene delivery, and this study on a bioreducible liposome with self-reporting ability would be a guide for further research on the development of biodegradable gene carriers.

Transfection efficiencies of α-tocopherylated cationic gemini lipids with hydroxyethyl bearing headgroups under high serum conditions

Liposomal gene transfection under high serum conditions.