Functionalized organic nanotubes as tubular nonviral gene transfer vector

Fabrication, modification and application of lipid nanotubes

The potential application of high aspect-ratio nanomaterials motivates the development of the fabrication and modification of lipid nanotubes(LNTs). To date, diverse fabricate processes and elaborate template procedures have produced suitable tubular architectures with definite dimensions and complex structures for expected functions and applications. Herein, we comprehensively summarize the fabrication of LNTs in vitro and discuss the progress made on the micro/nanomaterials fabrication using LNTs as a template, as well as the functions and possible application of a wide range of LNTs as fundamental or derivative material. In addition, the characteristics, advantages, and disadvantages of different fabrication, modification methods, and development prospects of LNTs were briefly summarized.

Stimuli-Responsive Transformable Supramolecular Nanotubes

Supramolecular nanotubes produced by self-assembly of organic molecules can have unique structural features such as a one-dimensional morphology with no branching, distinguishable inner and outer surfaces and membrane walls, or a structure that is hollow and has a high aspect ratio. Incorporation of functional groups that respond to external chemical or physical stimuli into the constituent organic molecules of supramolecular nanotubes allows us to drastically change the structure of the nanotubes by applying such stimuli. This ability affords an array of controllable approaches for the encapsulation, storage, and release of guest compounds, which is expected to be useful in the fields of physics, chemistry, biology, and medicine. In this article, I review the supramolecular nanotubes developed by our group that exhibit morphological transformations in response to pH, chemical reaction, light, temperature, or moisture.

A highly sensitive fluorescence method for the detection of T4 polynucleotide kinase phosphatase based on polydopamine nanotubes

T4 polynucleotide kinase phosphatase (T4 PNKP) plays a critical role in various cellular events, such as DNA damage repair, replication, and recombination. Here, we have described a novel biosensor to detect the activity of T4 PNKP based on polydopamine nanotubes (PDANTs) mediated fluorescence resonance energy transfer (FRET). A FAM-labelled (6-carboxyl-fluorescein) hairpin DNA probe with 3'-phosphoryl terminal was designed as the substrate for T4 PNKP. With the addition of PDANTs, the fluorescence of FAM-labelled hairpin DNA probe could be quenched because of the high adsorption of hairpin DNA on PDANTs. When T4 PNKP dephosphorylated the DNA probe, a double-stranded DNA (dsDNA) product was obtained by Klenow fragment polymerase (KF polymerase) on its 3'-hydroxyl terminal, which could retain most of the fluorescence due to the week adsorption of dsDNA on PDANTs. The developed method demonstrates the sensitivity for T4 PNKP assay in the range from 0.05 to 1.5 U mL^-1 with the detection limit of 0.005 U mL^-1, which endows the proposed strategy with high enough sensitivity for practical detection in cell lysates. With the advantages mentioned above, this novel sensitive strategy has the potential in the study of DNA damage repair mechanisms.

Soft-Matter Nanotubes: A Platform for Diverse Functions and Applications

Self-assembled organic nanotubes made of single or multiple molecular components can be classified into soft-matter nanotubes (SMNTs) by contrast with hard-matter nanotubes, such as carbon and other inorganic nanotubes. To date, diverse self-assembly processes and elaborate template procedures using rationally designed organic molecules have produced suitable tubular architectures with definite dimensions, structural complexity, and hierarchy for expected functions and applications. Herein, we comprehensively discuss every functions and possible applications of a wide range of SMNTs as bulk materials or single components. This Review highlights valuable contributions mainly in the past decade. Fifteen different families of SMNTs are discussed from the viewpoints of chemical, physical, biological, and medical applications, as well as action fields (e.g., interior, wall, exterior, whole structure, and ensemble of nanotubes). Chemical applications of the SMNTs are associated with encapsulating materials and sensors. SMNTs also behave, while sometimes undergoing morphological transformation, as a catalyst, template, liquid crystal, hydro-/organogel, superhydrophobic surface, and micron size engine. Physical functions pertain to ferro-/piezoelectricity and energy migration/storage, leading to the applications to electrodes or supercapacitors, and mechanical reinforcement. Biological functions involve artificial chaperone, transmembrane transport, nanochannels, and channel reactors. Finally, medical functions range over drug delivery, nonviral gene transfer vector, and virus trap.

Supramolecular Self-Assembly into Biofunctional Soft Nanotubes: From Bilayers to Monolayers

The inner and outer surfaces of bilayer-based lipid nanotubes can be hardly modified selectively by a favorite functional group. Monolayer-based nanotubes display a definitive difference in their inner and outer functionalities if bipolar wedge-shaped amphiphiles, so-called bolaamphiphiles, as a constituent of the monolayer membrane pack in a parallel fashion with a head-to-tail interface. To exclusively form unsymmetrical monolayer lipid membranes, we focus herein on the rational molecular design of bolaamphiphiles and a variety of self-assembly processes into tubular architectures. We first describe the importance of polymorph and polytype control and then discuss diverse methodologies utilizing a polymer template, multiple hydrogen bonds, binary and ternary coassembly, and two-step self-assembly. Novel biologically important functions of the obtained soft nanotubes, brought about only by completely unsymmetrical inner and outer surfaces, are discussed in terms of protein refolding, drug nanocarriers, lectin detection, a chiral inducer for achiral polymers, the tailored fabrication of polydopamine, and spontaneous nematic alignment.

Self-Assembled Dendron-Cyclodextrin Nanotubes with a Polyethylenimine Surface and Their Gene Delivery Capability

Self-assembled dendron-cyclodextrin nanotubes (Den-CD-NTs) with selected surface functionalities can serve as templates for the formation of complexes with polymers, and the resulting nanotube-polymer complexes can be utilized as gene carriers. The negatively charged surfaces of Den-CD-NTs were covered with a positively charged polyethylenimine (PEI) layer using electrostatic interactions, and the resulting nanotube-PEI complex, having a positively charged surface exhibited intracellular uptake. Furthermore, the nanotube-PEI complex exhibited the capability for DNA complexation with reduced enzymatic degradation, and also showed higher transfection efficiency and lower cytotoxicity than PEI. Therefore, Den-CD-NTs, in simple complexation with a surface PEI layer, are potentially useful gene delivery vectors.

Imaging fluorescence correlation spectroscopy studies of dye diffusion in self-assembled organic nanotubes

Imaging fluorescence correlation spectroscopy is used to elucidate the rate and mechanism for diffusion of charged molecules within charged, self-assembled organic nanotubes.

Effects of PEGylation on the physicochemical properties and in vivo distribution of organic nanotubes

Application of organic nanotubes (ONTs) into drug nanocarriers ultimately requires validation in live animals. For improving the dispersibility in biological media and in vivo distribution, the outer surface of an ONT was functionalized with polyethylene glycol (PEG) via the coassembly of an ONT-forming lipid with 5-20 mol% of a PEG-tethered lipid analogue (PEG-lipid). Firstly, the effect of PEGylation on the psysicochemical properties of ONTs, such as morphology and dispersibility, was investigated. PEGylation of ONTs slightly reduced the average length and effectively prevented the aggregation in phosphate-buffered saline (PBS). The PEGylated ONTs even showed high thermal stability in aqueous dispersion at least up to 95°C. Secondly, differential scanning calorimetry and powder X-ray diffraction indicated that ~10 mol% of PEG-lipid was completely incorporated into the ONTs, while 20 mol% of PEG-lipid encountered a partial phase separation during coassembly. In the heating differential scanning calorimetry runs, the resultant PEGylated ONTs with 5 mol% PEG-lipid showed no sign of phase separation up to 180°C under lyophilized condition, while those with 10 mol% and 20 mol% PEG-lipid showed some phase separation of the PEG-lipid above 120°C. Finally, PEGylation significantly affected the tissue distribution and prolonged the persistence time in the blood in mice. Non-PEGylated ONTs was quickly cleared from the circulation after intravenous infusion and preferentially accumulated in the lung, while PEGylated ONTs was mainly trapped in the liver and could circulate in the blood up to 24 hours. This study provided valuable information of physicochemical properties and the in vivo distribution behavior of PEGylated ONTs for their potential application into drug nanocarriers.

Hybrid organic nanotubes with dual functionalities localized on cylindrical nanochannels control the release of doxorubicin

A method to control the release of the anti-cancer drug doxorubicin (Dox) from cylindrical nanocapsules, known as organic nanotubes (ONTs), is reported. Co-assembly of a tube-forming glycolipid and its hydrophobized analogue yield novel ONTs with both -COOH and hydrophobic benzyloxycarbonyl groups localized on cylindrical nanochannels. The hydrophobicity of the ONTs nanochannels is easily tunable by adjusting the mixing ratio of the two glycolipids in the co-assembly process. The resultant biologically stable ONTs are able to capture Dox with high efficiency into the cylindrical nanochannels via ion complexation between cationic Dox and anionic -COO(-) , and the release of Dox from hybrid ONTs is effectively controlled by tuning the electrostatic interaction and the hydrophobicity. This controlled release by tuning the hydrophobicity of the ONTs' nanochannels greatly reduces the cytotoxicity of Dox@ONTs for HeLa cells.

Cisplatin-encapsulated organic nanotubes by endo-complexation in the hollow cylinder

A bipolar glycolipid self-assembles into organic nanotubes upon its chelation with an anticancer drug cis-dichlorodiamineplatinum(II) (CDDP). The facile synthesis of glycolipid, chelation-assisted formation of the nanotubes, and efficient loading and prolonged release of CDDP demonstrate a new approach to high-axial supramolecular drug nanocarriers.