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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. [ABSTRACT FROM AUTHOR]

As sucrose esters (SEs) are natural and biodegradable excipients with excellent drug dissolution and drug absorption/permeation in controlled release systems, we firstly incorporated SE into liposomes for gene delivery in this article. A peptide-based lipid (CDO14), Gemini-based quaternary ammonium-based lipid (CTA14), and mono-head quaternary ammonium lipid (CPA14), and SE as helper lipid, were prepared into liposomes which could enhance the interactions between liposomes and pDNA. Most importantly, the liposomes with helper lipid SE showed higher transfection and lower cytotoxicity than those without SE in Hela and A549 cells. It was also found that the transfection efficiency increased with the increase of SE content. The selected liposome, CDO14/SE, was able to deliver siRNA against luciferase for silencing gene in lung tumors of mice, with little in vivo toxicity. The results convincingly demonstrated SEs could be highly desirable candidates for gene delivery systems. [ABSTRACT FROM AUTHOR]

To use siRNA (small interfering RNA) for gene therapy, a gene delivery system is often necessary to overcome several challenging requirements including rapid excretion, low stability in blood serum, non-specific accumulation in tissues, poor cellular uptake and inefficient intracellular release. Active and/or passive targeting should help the delivery system to reach the desired tissue or cell, to be internalized, and to deliver siRNA to the cytoplasm so that siRNA can inhibit protein synthesis. This review covers conjugates of small targeting molecules and non-viral delivery systems for the mediation of siRNA, with a focus on their transfection properties in order to help the development of new and efficient siRNA delivery systems, as the therapeutic solutions of tomorrow. Statement of Significance The delivery of siRNA into cells or tissues remains to be a challenge for its applications, an alternative strategy for siRNA delivery systems is direct conjugation of non-viral vectors with targeting moieties for cellular delivery. In comparison to macromolecules, small targeting molecules have attracted great attention due to their many potential advantages including significant simplicity and ease of production, good repeatability and biodegradability. This review will focus on the most recent advances in the delivery of siRNA using conjugates of small targeting molecules and non-viral delivery systems. Based the editor’s suggestions, we hope the revised manuscript could provide more profound understanding to the conjugates of targeting molecules to vectors for mediation of siRNA. [ABSTRACT FROM AUTHOR]

Abstract: Though the delivery of siRNA into cells, tissues or organs remains to be a big obstacle for its applications, recently siRNA therapeutics has developed rapidly and already there are clinical trials ongoing or planned. Some non-viral vectors have attracted much more attention and shown the great potential for combating the delivery obstacle. As a novel class of lipid like materials lipidoids have the advantages of easy synthesis and large library of compounds. Cell penetrating peptides and chitosans have been used for the delivery of bioactive molecules for many years, but they are showing great promise for the delivery of siRNA. The hybrids of inorganic particles and the conjugates of siRNA have indicated the complex utilization different materials may provide another solution to the delivery problem. The most exciting thing is some clinical trials are undergoing, which provokes the hope of real curing method by using RNAi mediated by some non-viral vectors. [Copyright &y& Elsevier]

• The cationic peptide liposome can deliver IGF-1R-siRNA to inhibit tumor growth. • The liposome exhibited limited toxicity when used at normal dosages. • The study strengthens the use of peptide liposomes as a gene delivery vehicle. • The study correlated the lipid headgroup structures and toxicology. The toxicology of cationic liposomes was explored to advance clinical trials of liposome-mediated gene therapy through the analysis of a peptide cationic liposome with DOTAP as a positive control. We first investigated the delivery of luciferase siRNA by several peptide liposomes in mice bearing lung cancer A549 cell xenografts. Of these, a cationic liposome (CDO14) was selected for further investigation. CDO14 efficiently mediated IGF-1R-siRNA delivery and inhibited the growth of the A549 cell xenografts. The in vivo toxicity and toxicological mechanisms of the selected liposome were evaluated to assess its potential utility for gene delivery. Specifically, the effects of CDO14 on mouse body weight, hematology, urine, serum biochemical indices, and histopathology were measured in acute toxicity and subchronic toxicity tests. CDO14 showed limited toxicological effects at low dosages although it induced pulmonary inflammation and liver injury at higher dosages. The toxicity of CDO14 was lower than that of DOTAP, and the toxicity of CDO14 did not change when complexed with siRNA. The pulmonary inflammation induced by CDO14 occurred via expressional up-regulation of the pro-inflammatory cytokines TNF-α and IL-6, and expressional down-regulation of the anti-inflammatory cytokine IL-10. Liver injury induced by CDO14 was mediated by the JAK2-STAT3 signaling pathway. Lastly, CDO14 did not affect the expression of apoptosis-related proteins in normal liver cells, suggesting that it did not induce apoptosis of normal cells. The toxicological results demonstrate that peptide-based headgroups in lipids are superior to those with quaternary ammonium headgroups that are used as gene vectors for cancer therapy. [ABSTRACT FROM AUTHOR]

[Display omitted] • Four pH-responsive and ionizable lipids were synthesized. • Liposomes showed remarkable siRNA condensation and pH-responsiveness. • EDM liposome exhibited efficient DNA and siRNA delivery to A549 cells. • EDM liposome could deliver IGF-1R siRNA to inhibit A549 tumor growth in mice. 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 p K 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. [ABSTRACT FROM AUTHOR]

In this paper, two novel carbamate-linked quaternary ammonium lipids (MU18: a lipid with a mono-ammonium head; GU18: a lipid with a Gemini-ammonium head) containing unsaturated hydrophobic chains were designed and synthesized. The chemical structures of the synthetic lipids were characterized by infrared spectrum, ESI-MS, 1 H NMR, 13 C NMR, and HPLC. For investigating the effect of unsaturation on gene delivery, the previous reported saturated cationic liposomes (MS18 and GS18) were used as comparison. Cationic liposomes were prepared by using these cationic lipids and neutral lipid DOPE at the molar ratio of 1:1. Particle sizes and zeta potentials of the cationic liposomes were studied to show that they were suitable for gene transfection. The binding abilities of the cationic liposomes were investigated by gel electrophoresis at various N/P ratios from 0.5/1 to 8/1. The results indicated that the binding ability of GU18 was much better than MU18 and the saturated cationic liposomes (MS18 and GS18). DNA transfection of these liposomes comparable to commercially available reagent (DOTAP) was achieved in vitro against Hela, HepG-2 and NCI-H460 cell lines. GU18 showed higher transfection at the N/P ratio of 3/1 than other cationic liposomes and the positive control, DOTAP. All of the liposomes presented a relatively low cytotoxicity, which was measured by MTT. Therefore, the synthetic lipids bearing unsaturated hydrophobic chains and Gemini-head could be promising candidates for gene delivery. [ABSTRACT FROM AUTHOR]

Cationic lipids have become known as one of the most versatile tools for the delivery of DNA, RNA and many other therapeutic molecules, and are especially attractive because they can be easily designed, synthesized and characterized. Most of cationic lipids share the common structure of cationic head groups and hydrophobic portions with linker bonds between both domains. The linker bond is an important determinant of the chemical stability and biodegradability of cationic lipid, and further governs its transfection efficiency and cytotoxicity. Based on the structures of linker bonds, they can be grouped into many types, such as ether, ester, amide, carbamate, disulfide, urea, acylhydrazone, phosphate, and other unusual types (carnitine, vinyl ether, ketal, glutamic acid, aspartic acid, malonic acid diamide and dihydroxybenzene). This review summarizes some research results concerning the nature (such as the structure and orientation of linker groups) and density (such as the spacing and the number of linker groups) of linker bond for improving the chemical stability, biodegradability, transfection efficiency and cytotoxicity of cationic lipid to overcome the critical barriers of in vitro and in vivo transfection. [ABSTRACT FROM AUTHOR]

A series of carbamate-linked cationic lipids containing saturated or unsaturated hydrocarbon chains and quaternary ammonium head were designed and synthesized. After recrystallization, carbamate-linked cationic lipids with high purity (over 95%) were obtained. The structures of these lipids were proved by IR spectrum, HR-ESI-MS, HPLC, 1 H NMR and 13 C NMR. The liposomes were prepared by using these cationic lipids and neutral lipid DOPE. Particle size and zeta-potential were studied to show that they were suitable for gene transfection. The DNA-bonding ability of C12:0, C14:0 and C18:1 cationic liposomes was much better than others. The results of transfection showed that hydrophobic chains of these lipids have great effects on their transfection activity. The lipids bearing C12:0, C14:0 saturated chains or C18:1 unsaturated chain showed relatively higher transfection efficiency and lower cytotoxicity. So these cationic lipids could be used as non-viral gene carriers for further studies. [ABSTRACT FROM AUTHOR]

Highlights: [•] Three new carbamate-linked cationic lipids with hydroxyl headgroup were synthesized. [•] These lipids are easy to produce starting from environmentally friendly materials. [•] These liposomes exhibit relatively high transfection efficiency and low toxicity. [•] The inclusion of hydroxyl group in the headgroup can improve transfection efficiency. [ABSTRACT FROM AUTHOR]

Abstract: We have introduced a convenient synthesis method for carbamate-linked cationic lipids. Two cationic lipids N-[1-(2,3-didodecylcarbamoyloxy)propyl]-N,N,N-trimethylammonium iodide (DDCTMA) and N-[1-(2,3-didodecyl carbamoyloxy)propyl]-N-ethyl-N,N-dimethylammonium iodide (DDCEDMA), with identical length of hydrocarbon chains, alternative quaternary ammonium heads, carbamate linkages between hydrocarbon chains and quaternary ammonium heads, were synthesized for liposome-mediated gene delivery. Liposomes composed of DDCEDMA and DOPE in 1:1 ratio exhibited a lower zeta potential as compared to those made of pure DDCEDMA alone, which influences their DNA-binding ability. pGFP-N2 plasmid was transferred by cationic liposomes formed from the above cationic lipids into Hela and Hep-2 cells, and the transfection efficiency of some of cationic liposomes was superior or parallel to that of two commercial transfection agents, Lipofectamine2000 and DOTAP. Combined with the results of the agarose gel electrophoresis and transfection experiment, the DNA-binding ability of cationic lipids was too strong to release DNA from complex in the transfection, which could lead to relative low transfection efficiency and high cytotoxicity. [Copyright &y& Elsevier]