Multifunctional envelope-type nano device (MEND) as a non-viral gene delivery system

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Abstract

In this review, we describe a key role of octaarginine (R8) in developing our new concept of “Programmed Packaging”, by which we succeeded in creating a multifunctional envelope-type nano device (MEND) as a non-viral gene-delivery system. This concept can be applied not only to nuclear targeting of plasmid DNA (pDNA) but also to cytosolic delivery of functional nucleic acids such as oligonucleotides or siRNA. This concept has been extended to other organelles such as mitochondria as a foundation for innovative nanomedicine. Finally, we discuss the rate-limiting step in gene delivery by comparing non-viral and viral gene delivery systems, which clearly indicates the importance of nuclear disposition of pDNA for efficient transfection.

Introduction

A successful gene delivery system requires a rational strategy for overcoming many biological barriers such as membrane and enzymatic barriers. When plasmid DNA (pDNA) packaged in a delivery system is internalized via endocytosis, it must escape from endosomes before lysosomal degradation. The pDNA also must pass through the nuclear membrane before it can be transcribed in the nucleus. Therefore, the ideal gene delivery system should be equipped with a variety of functional devices to overcome these barriers, such as ligands for specific targeting, pH-sensitive fusogenic peptides, and a nuclear localization signal (NLS) [1], [2], [3], [4], [5]. Most non-viral vectors developed to date contain some of these devices [1], [2], [3], [4], [5]; however, it is difficult to integrate all of them into a single delivery system and to have each function exerted according to a specific program to overcome the barriers. Simple mixing of these nano devices is not sufficient for developing such an “artificially intelligent” nano device. Therefore, a new concept was required to develop a non-viral gene delivery system which can compete with viral ones in terms of efficiency. We succeeded in developing a multifunctional envelope-type nano device (MEND) as a non-viral gene delivery system based on a new concept, “Programmed Packaging”. In this review, we describe how we developed this concept and how we construct the MEND by focusing on the function of octaarginine as a key molecular component of the MEND.

Section snippets

Importance of topology control

Since the R8 peptide was found to be taken up via a nonclassical endocytic pathway [6], which can circumvent lysosomal degradation, R8 was proposed as a functional device for efficient intracellular trafficking of nanoparticles, such as liposomes. Thus, the mechanism of uptake of nanoparticles tagged with R8 peptide was confirmed using nano-size complexes of pDNA encoding luciferase and complexed with either R8 peptide or stearylated R8 (STR-R8) [7]. The transfection activity of the STR-R8/DNA

A new concept: programmed packaging

Recently, a novel non-viral gene delivery system was developed based on a new packaging concept termed “Programmed Packaging”, and was named the MEND [17]. Programmed Packaging was proposed to develop rational non-viral gene delivery systems equipped with various functional devices, including ligands for specific receptors, pH-sensitive fusogenic peptides for endosomal escape, and a NLS for enhanced nuclear delivery [5] to overcome several barriers in the process of gene delivery to the nucleus

MEND for oligonucleotides

The R8-MEND was suggested to be a useful delivery system for antisense oligodeoxynucleotides (ODN), which can inhibit the function of mRNA in the cytosolic space, since R8-MEND showed high efficacy in pDNA delivery, as mentioned above. For delivery of ODN, ODN-encapsulated R8-MEND (ODN-MEND) was developed [20], [21]. Three types of R8-MENDs were constructed by co-encapsulation of luciferase-encoding pDNA and anti-luciferase ODN condensed by three polycations – STR-R8, PLL and protamine – and

Drug carriers for mitochondrial drug therapy

Mitochondrial dysfunction has recently been implicated in a variety of diseases, including neurodegenerative and neuromuscular disorders, obesity and diabetes mellitus, ischemia-reperfusion injury, cancer and inherited mitochondrial diseases [25], [26]. Although therapies for these diseases are desired, strategies designed to complement mitochondrial dysfunction are rare [27], [28]. To enable drug delivery targeted to mitochondria, we first need to establish a method to encapsulate various

Quantitative analytical method CIDIQ

As described above, we control the intracellular trafficking of pDNA, ODN, siRNA and proteins using nano particles developed based on the concept of Programmed Packaging. For the development of new-generation gene-delivery vectors, a more rational strategy is required, based on feedback information for intracellular trafficking. This information would enable us to better recognize which of the barriers need to be overcome to improve the gene-delivery activity. Recently, we proposed a novel

Conclusion

MEND has been developed based on the concept of Programmed Packaging and applied to not only pDNA but also to ODN, siRNA and other molecules. A comparative analysis between viral and non-viral gene vectors indicated that post-nuclear delivery process is the rate-limiting step in transfection mediated by non-viral gene delivery systems. Therefore, further efforts should be directed at optimizing the intranuclear disposition of MEND. At the same time, MEND can be extended not only to nuclear

Acknowledgement

The authors wish to thank Dr. Daryl Henderson for his helpful advice in writing the English manuscript.

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    This review is part of the Advanced Drug Delivery Reviews theme issue on “Membrane Permeable Peptide Vectors: Chemistry and Functional Design for the Therapeutic Applications”.

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    Present address: Kyoto Pharmaceutical University, Japan.

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