Efficient gene transfection in the neurotypic cells by star-shaped polymer consisting of β-cyclodextrin core and poly(amidoamine) dendron arms

Click Synthesis of Size- and Shape-Tunable Star Polymers with Functional Macrocyclic Cores for Synergistic DNA Complexation and Delivery

The architectural perfection and multivalency of dendrimers have made them useful for biodelivery via peripheral functionalization and the adjustment of dendrimer generations. Modulation of the core-forming and internal matrix-forming structures offers virtually unlimited opportunities for further optimization, but only in a few cases this has been made compatible with strict diastereomeric purity over molecularly diverse series, low toxicity, and limited synthetic effort. Fully regular star polymers built on biocompatible macrocyclic platforms, such as hyperbranched cyclodextrins, offer advantages in terms of facile synthesis and flexible compositions, but core elaboration in terms of shape and function becomes problematic. Here we report the synthesis and characterization of star polymers consisting of functional trehalose-based macrocyclic cores (cyclotrehalans, CTs) and aminothiourea dendron arms, which can be efficiently synthesized from sequential click reactions of orthogonal monomers, display no cytotoxicity, and efficiently complex and deliver plasmid DNA in vitro and in vivo. When compared with some commercial cationic dendrimers or polymers, the new CT-scaffolded star polymers show better transfection efficiencies in several cell lines and structure-dependent cell selectivity patterns. Notably, the CT core could be predefined to exert Zn(II) complexing or molecular inclusion capabilities, which has been exploited to synergistically boost cell transfection by orders of magnitude and modulate the organ tropism in vivo.

Recent advances in siRNA delivery

In the 1990s an unexpected gene-silencing phenomena in plants, the later called RNA interference (RNAi), perplexed scientists. Following the proof of activity in mammalian cells, small interfering RNAs (siRNAs) have quickly crept into biomedical research as a new powerful tool for the potential treatment of different human diseases based on altered gene expression. In the past decades, several promising data from ongoing clinical trials have been reported. However, despite surprising successes in many pre-clinical studies, concrete obstacles still need to be overcome to translate therapeutic siRNAs into clinical reality. Here, we provide an update on the recent advances of RNAi-based therapeutics and highlight novel synthetic platforms for the intracellular delivery of siRNAs.

Low Molecular Weight PEI-Based Vectors via Acid-Labile Ortho Ester Linkage for Improved Gene Delivery

A series of novel pH-sensitive gene delivery vectors (POEI 1, 2, and 3) are synthesized through Michael addition from low molecular weight PEI (LMW PEI) via acid-labile ortho ester linkage with terminal acrylates (OEAc) by various feed molar ratios. The obtained POEI 1 and POEI 2 can efficiently condense plasmid DNA into nanoparticles with size range of 200-300 nm and zeta-potentials of about +15 mV while protecting DNA from enzymatic digestion compared with POEI 3. Significantly, ortho ester groups of POEI main-chains can make an instantaneous degradation-response to acidic endosomal pH (≈5.0), resulting in accelerated disruption of polyplexes and intracellular DNA release. MTT assay reveals that all POEIs exhibit much lower cytotoxicity in different cells than branched PEI (25 KDa). As expected, POEI 1 and POEI 2 perform improved gene transfection in vitro, suggesting that such polycations might be promising gene vectors based on overcoming toxicity-efficiency contradiction.

Tailoring the dendrimer core for efficient gene delivery

Dendrimers have been widely used as non-viral gene vectors due to well-defined chemical structures, high density of cationic charges and ease of surface modification. Although a large number of studies have reported the important roles of dendrimer architecture, component, generation and surface functionality in gene delivery, the effect of dendrimer core on this issue still remains unclear. Recent literatures suggest that a slight alternation in dendrimer core has a profound effect in the transfection efficacy and biocompatibility. In this review, we will discuss the transfection mechanism of dendrimers with different types of cores in respect of flexibility, hydrophobicity and functionality. We hope to open a possibility of designing efficient dendrimers for gene delivery by choosing a proper dendrimer core.

STATEMENT OF SIGNIFICANCE

As a branch of researches on dendrimers and dendritic polymers, the design of biocompatible and high efficient polymeric gene carriers has attracted increasing attentions during these years. Although the effect of dendrimer generation, species, architecture and surface functionality on gene delivery have been widely reported, the effect of dendrimer core on this issue still remains unclear. Recent literatures suggest that a minor variation on the dendrimer core has a profound effect in the transfection efficacy and biocompatibility. This critical review summarized the dendrimers with different types of cores and discussed the transfection mechanism with particular focus on the flexibility, hydrophobicity, and functionality. It is hoped to provide a new insight to design efficient and safe dendrimer-based gene vectors by choosing a proper core. To the best of our knowledge, this is the first review on the effect of dendrimer core on gene delivery. The findings obtained in this filed are of central importance in the design of efficient polymeric gene vectors. This article will appeal a wide readership such as physical chemist, dendrimer chemist, biological chemist, pharmaceutical scientist, and biomaterial researchers. We hope that this review article can be published by Acta Biomaterialia, a top journal that publishes important reviews in the field of biomaterials science.

The influence of polymer architecture on in vitro pDNA transfection

In the field of polymer-based gene delivery, the tuning potential of polymers by using different architectures like graft- and star-shaped polymers as well as self-assembled block copolymers is immense. In the last years numerous new polymer designs showed enhanced transfections properties in combination with a good biocompatibility.

Small, stable and biocompatible gold nanoparticles capped with a β-cyclodextrin polymer

Gold nanoparticles capped with a β-cyclodextrin epichlorohydrin polymer resulted to be smaller than 5 nm, stable in physiological fluid and biocompatible, features that denote their capability as scaffold for future applications in nanomedicine.

Cationic Polysaccharides in Gene Delivery

Approval of Glybera®, a gene therapy to treat lipoprotein lipase deficiency, by the European Union Marketing Authorization, and more than 1800 clinical trials in over 31 countries for the treatment of many incurable diseases, narrates the successful journey of gene therapy in the biomedical field. However, the undesired side effects of gene therapy using viral and other vectors have overshadowed the success story of gene therapy. Non-viral vectors, and more particularly cationic polysaccharides due to their non-toxicity, water solubility, biodegradability and excellent compatibility with body systems, provide an excellent alternative for gene delivery. This chapter highlights significant contributions made by cationic polysaccharides in gene delivery.

Star-shaped cyclodextrin-poly(l-lysine) derivative co-delivering docetaxel and MMP-9 siRNA plasmid in cancer therapy

A new cyclodextrin derivative (CD-PLLD) consisting of a β-cyclodextrin core and poly(l-lysine) dendron arms was prepared by the click conjugation of per-6-azido-b-cyclodextrin with propargyl focal point poly(l-lysine) dendron of third generation, and then used for docetaxel (DOC) and the best siRNA plasmid targeting MMP-9 (pMR3) co-delivery. Different from commonly used amphiphilic copolymers with cationic character, the as obtained cyclodextrin derivative may be used directly for the combinatorial delivery of nucleic acid and lipophilic anticancer drugs without a complicated micellization process. It was found that CD-PLLD/pMR3 nanocomplex showed a good gene transfection efficiency in vitro, and could mediate the reduce of MMP-9 protein in HNE-1 cells. For co-delivery analysis, the obtained CD-PLLD/DOC/pMR3 complexes could induce a more significant apoptosis than DOC or pMR3 used only, and decreased invasive capacity of HNE-1 cells. Moreover, the star-shaped copolymer exhibited better blood compatibility and lower cytotoxicity compared to PEI-25k in the hemolysis and MTT assays, which should be encouraged in nasopharyngeal cancer therapy.

Cyclodextrins in non-viral gene delivery

Cyclodextrins (CDs) are naturally occurring cyclic oligosaccharides. They consist of (α-1,4)-linked glucose units, and possess a basket-shaped topology with an "inner-outer" amphiphilic character. Over the years, substantial efforts have been undertaken to investigate the possible use of CDs in drug delivery and controlled drug release, yet the potential of CDs in gene delivery has received comparatively less discussion in the literature. In this article, we will first discuss the properties of CDs for gene delivery, followed by a synopsis of the use of CDs in development and modification of non-viral gene carriers. Finally, areas that are noteworthy in CD-based gene delivery will be highlighted for future research. Due to the application prospects of CDs, it is anticipated that CDs will continue to emerge as an important tool for vector development, and will play significant roles in facilitating non-viral gene delivery in the forthcoming decades.