1 3
Topics in Current Chemistry (2020) 378:13
of these are considered to be promising candidates for the treatment of a wide range
of diseases, including cancer, human immunodeficiency virus, neurological malfunctions such as Parkinson’s disease and Alzheimer’s disease, and cardiovascular
disorders [123].
The efficiency of transfection depends on the delivery of therapeutic agents to
cells, with the consequence of effecting alterations in gene expression by replacing
or silencing defective genetic material. In this process, a DNA carrier, commonly
called as “transfectant,” is needed for the transportation of genes to the cellular compartment. The use of novel nucleic acid delivery systems has not only improved the
pharmacokinetics of DNA-based therapeutics but also achieved an efficiently targeted introduction of these molecules into desired tissues and cells.
DNA delivery techniques are currently classified into three general types, with
varying efficacy [121, 124]: (1) stimuli-mediated techniques; (2) mechanical transfection, (3) and vector-assisted delivery systems. The first two types involve introducing naked DNA into cells via microinjection [125], photoporation, particle bombardment, sonoporation, or electroporation [126, 127], all of which are considered to
be invasive methodologies. Such techniques are very precise, but they are time-consuming and restricted to local delivery in specific areas; moreover, they are rapidly
degraded by serum nucleases. In contrast, the application of vector-assisted delivery
systems is a suitable option for use in clinical trials. Viral vectors are currently the
most effective gene delivery methodology (80–90%), but they are associated with
the potential risk of inserting viral nucleic acid sequences into the host genome
and potentially causing unwelcome effects, such as the inappropriate expression of
genes. Consequently, safety, and immunogenicity concerns limit their usage in the
current clinical scenario [128].
Non-viral vectors have important advantages over viral approaches due to their
demonstrated biosafety in reducing pathogenicity, low cost, and ease of production.
However, this approach is hindered by a lack of efficiency [127]. Non-viral gene
therapy, within its broader context, includes such nucleic acid delivery applications
as, for example, anti-sense or siRNAs, but the techniques used for nucleic acid delivery do not fall within the scope of this review, which we have limited to a specific
focus on other procedures and materials used as non-viral vectors.
As early as around 1990, plasmid DNA (pDNA) has been recognized for having
an enormous potential for applications in gene therapy. Compared to viral and RNAbased vectors, plasmids are easier and cheaper to produce and store, and they have a
much longer shelf life [127–129]. At the molecular level, plasmids employ the DNA
transcription and translation apparatus in the cell to biosynthesize the therapeutic
entity, namely, the protein. Thus, they are able to correct genetic errors that basically
produce functionally incompetent copies of a given protein. In addition to focusing on a high molecular weight double-stranded DNA structure, several research
groups have studied plasmid design [130, 131], with a special focus on the choice
of enhancer, which is the pDNA region(s) that improve production of the targeted
gene. Plasmids have also powered a large number of clinical trials as part of gene
therapy in monogenic and polygenic diseases, such as cystic fibrosis and cancer, and
in infectious diseases [131]. However, the selection of pDNA carrier and the route
to the cell nucleus are possibly the two most challenging issues during transfection.
33
Reprinted from the journal
Topics in Current Chemistry (2020) 378:13
of these are considered to be promising candidates for the treatment of a wide range
of diseases, including cancer, human immunodeficiency virus, neurological malfunctions such as Parkinson’s disease and Alzheimer’s disease, and cardiovascular
disorders [123].
The efficiency of transfection depends on the delivery of therapeutic agents to
cells, with the consequence of effecting alterations in gene expression by replacing
or silencing defective genetic material. In this process, a DNA carrier, commonly
called as “transfectant,” is needed for the transportation of genes to the cellular compartment. The use of novel nucleic acid delivery systems has not only improved the
pharmacokinetics of DNA-based therapeutics but also achieved an efficiently targeted introduction of these molecules into desired tissues and cells.
DNA delivery techniques are currently classified into three general types, with
varying efficacy [121, 124]: (1) stimuli-mediated techniques; (2) mechanical transfection, (3) and vector-assisted delivery systems. The first two types involve introducing naked DNA into cells via microinjection [125], photoporation, particle bombardment, sonoporation, or electroporation [126, 127], all of which are considered to
be invasive methodologies. Such techniques are very precise, but they are time-consuming and restricted to local delivery in specific areas; moreover, they are rapidly
degraded by serum nucleases. In contrast, the application of vector-assisted delivery
systems is a suitable option for use in clinical trials. Viral vectors are currently the
most effective gene delivery methodology (80–90%), but they are associated with
the potential risk of inserting viral nucleic acid sequences into the host genome
and potentially causing unwelcome effects, such as the inappropriate expression of
genes. Consequently, safety, and immunogenicity concerns limit their usage in the
current clinical scenario [128].
Non-viral vectors have important advantages over viral approaches due to their
demonstrated biosafety in reducing pathogenicity, low cost, and ease of production.
However, this approach is hindered by a lack of efficiency [127]. Non-viral gene
therapy, within its broader context, includes such nucleic acid delivery applications
as, for example, anti-sense or siRNAs, but the techniques used for nucleic acid delivery do not fall within the scope of this review, which we have limited to a specific
focus on other procedures and materials used as non-viral vectors.
As early as around 1990, plasmid DNA (pDNA) has been recognized for having
an enormous potential for applications in gene therapy. Compared to viral and RNAbased vectors, plasmids are easier and cheaper to produce and store, and they have a
much longer shelf life [127–129]. At the molecular level, plasmids employ the DNA
transcription and translation apparatus in the cell to biosynthesize the therapeutic
entity, namely, the protein. Thus, they are able to correct genetic errors that basically
produce functionally incompetent copies of a given protein. In addition to focusing on a high molecular weight double-stranded DNA structure, several research
groups have studied plasmid design [130, 131], with a special focus on the choice
of enhancer, which is the pDNA region(s) that improve production of the targeted
gene. Plasmids have also powered a large number of clinical trials as part of gene
therapy in monogenic and polygenic diseases, such as cystic fibrosis and cancer, and
in infectious diseases [131]. However, the selection of pDNA carrier and the route
to the cell nucleus are possibly the two most challenging issues during transfection.
33
Reprinted from the journal