Polyrotaxanes for applications in life science and biotechnology

Targeted gene delivery by new folate-polycationic amphiphilic cyclodextrin-DNA nanocomplexes in vitro and in vivo

AIM

Development and evaluation of a new targeted gene delivery system by first preforming self-assembled nanocomplexes from a polycationic amphiphilic cyclodextrin (paCD) and pDNA and then decorating the surface of the nanoparticles with folic acid (FA).

EXPERIMENTAL SECTION

The cyclodextrin derivative (T2) is a tetradecacationic structure incorporating 14 primary amino groups and 7 thioureido groups at the primary face of a cyclomaltoheptaose (β-CD) core and 14 hexanoyl chains at the secondary face.

RESULTS AND CONCLUSIONS

T2 complexed and protected pDNA (luciferase-encoding plasmid DNA, pCMVLuc) and efficiently mediated transfection in vitro and in vivo with no associated toxicity. The combination of folic acid with CDplexes afforded ternary nanocomplexes (Fol-CDplexes) that enhanced significantly the transfection activity of pCMVLuc in human cervix adenocarcinoma HeLa cells, especially when formulated with 1 μg FA/μg DNA. The observed transfection enhancement was associated to specific folate receptor (FR)-mediated internalization of Fol-CDplexes, as corroborated by employing a receptor-deficient cell line (HepG2) and an excess of free folic acid. The in vivo studies, including luciferase reporter gene expression and biodistribution, indicated that 24h after intravenous administration of the T2-pDNA nanocomplexes, transfection takes part mainly in the liver and partially in the lung. Interestingly, the corresponding Fol-CDplexes lead to an increase in the transfection activity in the lung and the liver compared to non-targeted CDplexes. Folate-CDplexes developed in this study have improved transfection efficiency and although various methods have been used for the preparation of ligand-DNA-complexes, covalent binding is usually needed and insoluble aggregates are formed unless the concentration of the components is minimized. However, the complexes developed by first time in this work were prepared by simple mixing. The synthetic nature of this formulation provides the potential of flexibility in terms of composition and the capability of inexpensive and large-scale production of the complexes. These nanovectors may be an adequate alternative to viral vectors for gene therapy in the future.

Cationic α-cyclodextrin:poly(ethylene glycol) polyrotaxanes for siRNA delivery

RNA interference has broad therapeutic potential due to its high specificity and ability to potentially evade drug resistance. Three cationic α-cyclodextrin:poly(ethylene glycol) polyrotaxanes derived from polymer axles of different sizes (MW 2,000, 3,400, and 10,000) have been synthesized for delivering siRNA. These polyrotaxanes are able to condense siRNA into positively charged particles that are <200 nm in diameter, enabling their facile internalization into mammalian cells. The cationic polyrotaxanes display cytotoxicity profiles that are >10(2)-fold lower than the commercial standard bPEI and gene silencing efficiencies that are comparable to those of both Lipofectamine 2000 and bPEI. Our findings suggest that the cationic polyrotaxanes display a size-activity relationship, wherein the higher molecular weight polyrotaxanes (PEG3,400 and 10,000) are able to condense and deliver siRNA better than the lower molecular weight material (PEG2,000).

Polysiloxane ionic liquids as good solvents for β-cyclodextrin-polydimethylsiloxane polyrotaxane structures

An ionic liquid based on polydimethylsiloxane with imidazolium salt brushes was synthesized as a good solvent for β-cyclodextrin-polydimethylsiloxane rotaxane. As expected the PDMS-Im/Br ionic liquid had a liquid-like non-Newtonian behavior with rheological parameters dependent on frequency and temperature. The addition of rotaxane to the ionic liquid strengthened the non-Newtonian character of the sample and a type of stable liquid-like network was formed due to the contribution of weak ionic interactions. The structure is stable in the 20 to 80 °C domain as proved by the oscillatory and rotational rheological tests.

Molecular daisy chains

This tutorial review summarizes the progress made towards mechanically interlocked daisy chains. Such materials can be seen as a further development in polymer science, where the conventional covalent interlinking bonds are replaced by supramolecular binding concepts. Materials in which the mechanical bond is an integral part of the polymeric backbone are expected to possess unique macroscopic properties and are therefore the synthetic aim in an ever growing research community. After introducing general considerations about daisy chains, the most common analytic methods to get insight into the aggregation behaviour of such self-complementary monomers are presented. Cyclodextrins/aromatic rods, crown ethers/cationic rods and pillararenes/alkyl chains are systems used to achieve daisy chain-like molecular arrays. By comparison of the reported systems, conclusions about an improved structural design are drawn.

New structural insights into mechanically interlocked polymers revealed by ion mobility mass spectrometry

Mechanically interlocked polymers can possess significant additional physical properties, in comparison to those associated with their constituent parts. Their unique properties make them attractive for a range of potential applications, such as as biomaterials and molecular machines. Their efficient and reproducible synthesis is therefore of much interest. Both their synthesis and subsequent characterization are intriguing yet demanding. The properties of mechanically interlocked polymeric systems depend not only on the properties of their individual components but also on the topology of the subsequent product. Here traveling wave ion mobility mass spectrometry has been used to investigate the structural properties of a polyrotaxane system. Ion mobility studies reveal that this system remains linear in form with increase in size. Both ion mobility studies and tandem mass spectrometry studies indicate that the macrocycle preferentially remains associated with the ammonium moiety of the polymeric repeat unit and is impeded from moving freely along the axle. This is consistent with NMR observations of the average structure. Analysis of mechanically interlocked polymers by ion mobility mass spectrometry provides additional structural insights into these systems relating to dynamics, heterogeneity, and topology. This molecule-specific information is vital in order to understand the origin of a system's functional properties.

Polyamidoamine Dendrimer Conjugates with Cyclodextrins as Novel Carriers for DNA, shRNA and siRNA

Gene, short hairpin RNA (shRNA) and small interfering RNA (siRNA) delivery can be particularly used for the treatment of diseases by the entry of genetic materials mammalian cells either to express new proteins or to suppress the expression of proteins, respectively. Polyamidoamine (PAMAM) Starburst^TM dendrimers are used as non-viral vectors (carriers) for gene, shRNA and siRNA delivery. Recently, multifunctional PAMAM dendrimers can be used for the wide range of biomedical applications including intracellular delivery of genes and nucleic acid drugs. In this context, this review paper provides the recent findings on PAMAM dendrimer conjugates with cyclodextrins (CyDs) for gene, shRNA and siRNA delivery.

Polypseudorotaxanes of pegylated α-cyclodextrin/polyamidoamine dendrimer conjugate with cyclodextrins as a sustained release system for DNA

Nonviral gene delivery suffers from a number of limitations including short transgene expression times and low transfection efficiency. In this study, we examined whether polypseudorotaxanes (PPRXs) of polyethylene glycol (PEG, molecular weight: 2,000)-grafted α-cyclodextrin (α-CyD)/polyamidoamine dendrimer conjugate (PEG-α-CDE) with CyDs have the potential for the novel sustained release systems for plasmid DNA (pDNA). The PEG-α-CDE/pDNA complex formed PPRXs with α-CyD and γ-CyD solutions, but not with β-CyD solution. In the PEG-α-CDE/CyDs PPRX systems, 20.6mol of α-CyD and 11.8mol of γ-CyD were involved in the PPRXs formation with one PEG chain by α-CyD and γ-CyD, respectively, consistent with in the PEG-dendrimer/CyDs systems. PEG-α-CDE/pDNA/α-CyD PPRX and PEG-α-CDE/pDNA/γ-CyD PPRX formed hexagonal and tetragonal columnar channels in the crystalline phase, respectively. In addition, the CyDs PPRX provided the sustained release of pDNA from PEG-α-CDE complex with pDNA at least 72 h in vitro. The release of pDNA from CyDs PPRX retarded as the volume of dissolution medium decreased. Furthermore, the PEG-α-CDE/γ-CyD PPRX system showed sustained transfection efficiency after intramuscular injection to mice at least for 14days. These results suggest that the PEG-α-CDE/CyD PPRX systems are useful for novel sustained DNA release systems.