Introduction

The undeniable side effects of traditional approaches have been implemented for cancer therapy such as surgery, chemotherapy and radiotherapy, which lead to valuable research in the field of gene therapy to avoid killing some normal cells, DNA damaging, emergence of secondary cancer, etc. Small particles are sent to tumor cells based on selective treatment to repair and modify missing cellular functions and genes, which prevent the expression of unwanted genes production before translation and regulate proteins [1-3].
The ideal gene delivery system must comprise fundamental criteria. First, attending to the importance of cellular uptake of nanocarriers and prevention of charge repulsion in the delivery process, polycations should be able to neutralize negative charge of DNA due to negative charges of plasma membrane [4, 5]. The relationship of cellular clearance and size of nanoparticles could be assumed as a second parameter. Additionally, biocompatibility and immunogenicity are other substantial parameters. Therefore, nanoparticles should be stabled enough in the biological conditions not only before reaching the targeted-tumor cells, but also in the process of expression in the nucleus [1, 6]. Moreover, opsonization based on the surface characteristics of nanoparticles, is deemed as a crucial factor in their stabilization [7].
The carriers are classified into two major groups of viral and non-viral vectors, which each represent the gene delivery process as transduction and transfection, respectively [8]. Although the efficiency of viral vectors have been shown in clinical research, it is hard to elicit an effective therapeutic response due to their inherited substantial disadvantages like difficult production process, risk of mutagenesis and limited cargo capacity [9]. Furthermore, immunogenic responses to viruses will intensively suppress the effect of viral vectors and subsequently restrict the rate of transduced vectors to targeted cells [10]. Non-viral vectors are able to circumvent some of delivery-associated limitations of viral vectors with some constructive biological advantages such as low immune responses, affordable cost of production in large scale, safety or non-cytotoxicity, and also more targeted transfection through designed-surface ligands. However, in vivo transfection efficiency of non-viral vectors is lower than viral vectors [3, 11].
Polymeric and cationic lipids as non-viral carriers condense the string-like DNA into nanoscale dimension to become appropriate for cellular uptake [12]. Polycations like polysaccharides have possible opportunities in the changing or improving physicochemical attributes of their efficacy through power of binding, reaching the least toxicity and impressive cellular release [1, 13]. The polycations are all polyamines that contain the first, second, third, or fourth amine groups [1]. Polymeric macromolecules with high cationic charges can operate as an endosomal buffering system in gene delivery which suppresses the endosomal enzymes activity and prevents degradation and accumulation of trapped-DNA molecules in cytosol [1, 14].
Dextran is a linear and non-polyelectrolytes polysaccharide, consists of ɑ-1,6 glycosidic linkages and also few branch of ɑ-1, 3 glycosidic linkages [15-17]. Additionally, the presence of this neutral surface alongside other properties like low immunogenicity, water-solubility, lower rate of plasma protein absorption and more specific cellular uptake lead to their widespread usage in the different gene transfection of tumor targeted-therapy [15, 18]. Spermine is known as a natural tetra-amine, which involves in two primary and two secondary amino groups [19]. Azzam et al., shown that only polycations of dextran grafted with spermine has high efficiency in the in vitro cells transfection between 300 cationic polysaccharides in different molecular weights [20].
The serum medium has high inhibitory effects on the transfection rate of water-soluble dextran-spermine–DNA polymer up to 95% based on high hydrophilic property. Moreover, covalent attachment of hydrophobic residues to some dextran–spermine NH2 moieties could ameliorate the transfection efficiency in the serum containing media [3, 21]. In addition, based on the resemblance of structure of hydrophobic molecules with the plasma membrane, amphiphilic modifications of polycations tend to enhance or even ease carriers’ cellular uptake via endocytosis [21]. Stearic acid is a saturated-fatty acid, with appropriate biocompatibility and lower cytotoxicity has been utilized a lot in delivery systems. Amphiphilic dextran-stearic acid-spermin (DSASP) preparation takes place through esterification between the carboxyl group of stearic acid and hydroxyl group of the glucose units in dextran [15, 22].
Magnetofection is known as an effective approach for transfection to overcome restrictions like inactivation of some carriers under cell culture conditions and acceleration of diffusion [8, 23]. Superparamagnetic iron oxide (Fe3O4) nanoparticles are cubic inverse spin structures with well discretion in original solvent that are considered assubstantial magnetic materials based on widespread usage in various biomedical applications. These often undergo surface changes or are coated with polymers to become more appropriate in biological conditions to be prolonged in physical conditions and reduction of complex agglomeration [17, 24-26].
In this study, we have investigated the aspects of magnetic DSASP polymers based on magnetofection for gene delivery in the HEK 293T cells (Fig. 1 ). Fe3O4 nanoparticles are encapsulated inside two amphiphilic DSASP polymers with different grafted rates of stearic acid and spermine, which condensed pDNA well. Our findings show that interaction of DSASP@pDNA with Fe3O4 represents a novel biodegradable and biocompatible non-viral carrier which can be utilized for gene delivery.