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.