Novel Spermine-Derivative Cationic Lipids as an Effective Gene Carrier In Vitro

In the present study, nonionic surfactant vesicles (niosomes) formulated with Span 20, cholesterol, and novel synthesized spermine-based cationic lipids with four hydrocarbon tails in a molar ratio of 2.5:2.5:1 were investigated as a gene carrier. The effects of the structure of the cationic lipids, such as differences in the acyl chain length (C14, C16, and C18) of the hydrophobic tails, as well as the weight ratio of niosomes to DNA on transfection efficiency and cell viability were evaluated in a human cervical carcinoma cell line (HeLa cells) using pDNA encoding green fluorescent protein (pEGFP-C2). The niosomes were characterized both in terms of morphology and of size and charge measurement. The formation of complexes between niosomes and DNA was verified with a gel retardation assay. The transfection efficiency of these cationic niosomes was in the following order: spermine-C18 > spermine-C16 > spermine-C14. The highest transfection efficiency was obtained for transfection with spermine-C18 niosomes at a weight ratio of 10. Additionally, no serum effect on transfection efficiency was observed. The results from a cytotoxicity and hemolytic study showed that the cationic niosomes were safe in vitro. In addition, the cationic niosomes showed good physical stability for at least 1 month at 4°C. Therefore, the cationic niosomes offer an excellent prospect as an alternative gene carrier.(Gene therapy has been widely endorsed as a promising therapeutic approach for many incurable diseases related to gene function, such as genetic diseases, cancer, cardiovascular diseases, and autoimmune diseases. Successful gene therapy requires not only therapeutically suitable genes but also a safe and efficient gene carrier. To avoid severe side effects resulting from viral vectors, such as immunogenicity, mutagenesis, and carcinogenesis, nonviral vectors offer an attractive alternative. Cationic liposomes, a vesicular system widely investigated as effective gene carriers, are one of the preferred nonviral vectors. In addition, several studies have reported on the use of another vesicular system, nonionic surfactant vesicles (niosomes), as a gene carrier that can potentially be substituted for liposomes.Niosomes are nonionic surfactant vesicles formed by the self-assembly of nonionic amphiphiles into a bilayer structure in an aqueous medium. The nonionic surfactants preferably used to prepare niosomes include alkyl ethers and alkyl glyceryl ethers (Brij), sorbitan fatty acid esters (Span), and polyoxyethylenefatty acid esters (Tween). However, niosomes have several advantages over liposomes, including low production costs, high purity, uniform content, greater stability, and the ease of storing nonionic surfactants. Cationic niosomes used as gene carriers are usually composed of nonionic surfactants (i.e., Tween and Span), cholesterol, and cationic lipids. One of the major factors affecting gene transfection mediated by cationic niosomes is niosome composition, including the types of surfactants and cationic lipids used.
The cationic lipids used as transfection reagents usually contain three parts: a hydrophobic group, a linker group, and a positively charged head group that can interact with DNA and cause DNA condensation. The polyamines furnish one of the most effective cationic lipid head groups. Among the polyamines, spermine, a well-known polyamine consisting of a tetraamine with two primary and two secondary amino groups, plays an important role as a gene carrier. Spermine-derivative cationic lipids commercially available for gene delivery applications include dioctadecylamidoglycylspermine (DOGS) and dipalmitoylphosphatidyl ethanolamidospermine (DPPES). In the present study, cationic niosomes formulated with Span, cholesterol, and novel synthesized spermine-based cationic lipids with four hydrocarbon tails, namely, Tetra-(N1,N1,N14,N14-myristeroyloxyethyl)-spermine (spermine-C14), Tetra-(N1,N1,N14,N14-palmitoyloxyethyl)-spermine (spermine-C16), and Tetra-(N1,N1,N14,N14-steroyloxyethyl)-spermine (spermine-C18), in a molar ratio of 2.5:2.5:1 were investigated as gene carriers. Factors affecting transfection efficiency and cell viability, including cationic lipid structure (i.e., differences in the acyl chain length (C14, C16, and C18) of the hydrophobic tails as well as the weight ratio of niosomes to DNA) were evaluated in a human cervical carcinoma cell line (HeLa cells) using pDNA-encoded green fluorescent protein (pEGFP-C2). The morphology, size, and charge of these niosomes/DNA complexes were characterized, and agarose gel electrophoresis was performed. Moreover, the physical stability of these cationic niosomes was evaluated with size and charge measurements.) (AAPS PharmSciTech. 2014 Jun; 15(3): 722–730.)

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