High‐Efficiency Gene Transfection of Cells through Carbon Nanotube Arrays

Introducing nucleic acids into mammalian cells is a crucial step to elucidate biochemical pathways, and to modify gene expression and cellular development in immortalized cells, primary cells, and stem cells. Current transfection technologies are time consuming and limited by the size of genetic cargo, the inefficient introduction of test molecules into large populations of target cells, and the cytotoxicity of the techniques. A novel method of introducing genes and biomolecules into tens of thousands of mammalian cells has been developed through an array of aligned hollow carbon nanotubes, manufactured by template‐based nanofabrication processes, to achieve rapid high‐efficiency transfer with low cytotoxicity. The utilization of carbon nanotube arrays for gene transfection overcomes molecular weight limits of current technologies and can be adapted to deliver drugs or proteins in addition to nucleic acids.     

Effective Gene Delivery into Human Stem Cells with a Cell‐Targeting Peptide‐Modified Bioreducible Polymer

Stem cells are poorly permissive to non‐viral gene transfection reagents. In this study, we explored the possibility of improving gene delivery into human embryonic (hESC) and mesenchymal (hMSC) stem cells by synergizing the activity of a cell‐binding ligand with a polymer that releases nucleic acids in a cytoplasm‐responsive manner. A 29 amino acid long peptide, RVG, targeting the nicotinic acetylcholine receptor (nAchR) was identified to bind both hMSC and H9‐derived hESC. Conjugating RVG to a redox‐sensitive biodegradable dendrimer‐type arginine‐grafted polymer (PAM‐ABP) enabled nanoparticle formation with plasmid DNA without altering the environment‐sensitive DNA release property and favorable toxicity profile of the parent polymer. Importantly, RVG‐PAM‐ABP quantitatively enhanced transfection into both hMSC and hESC compared to commercial transfection reagents like Lipofectamine 2000 and Fugene. ～60% and 50% of hMSC and hESC were respectively transfected, and at increased levels on a per cell basis, without affecting pluripotency marker expression. RVG‐PAM‐ABP is thus a novel bioreducible, biocompatible, non‐toxic, synthetic gene delivery system for nAchR‐expressing stem cells. Our data also demonstrates that a cell‐binding ligand like RVG can cooperate with a gene delivery system like PAM‐ABP to enable transfection of poorly‐permissive cells.     

超支化聚合物在炭黑表面接枝改性的研究

以羟甲基化炭黑为中心核,利用其活性羟基与AB3型单体进行缩聚反应,在炭黑的表面原位接枝超支化聚合物。实验表明,炭黑表面接枝超支化聚合物后,粒子间聚集作用减弱,在乙醇中的分散性和稳定性提高,且对PVC有很好的增强、增韧作用。     

Dielectrophoresis‐Assisted Integration of 1024 Carbon Nanotube Sensors into a CMOS Microsystem

Carbon‐nanotube (CNT)‐based sensors offer the potential to detect single‐molecule events and picomolar analyte concentrations. An important step toward applications of such nanosensors is their integration in large arrays. The availability of large arrays would enable multiplexed and parallel sensing, and the simultaneously obtained sensor signals would facilitate statistical analysis. A reliable method to fabricate an array of 1024 CNT‐based sensors on a fully processed complementary‐metal‐oxide‐semiconductor microsystem is presented. A high‐yield process for the deposition of CNTs from a suspension by means of liquid‐coupled floating‐electrode dielectrophoresis (DEP), which yielded 80% of the sensor devices featuring between one and five CNTs, is developed. The mechanism of floating‐electrode DEP on full arrays and individual devices to understand its self‐limiting behavior is studied. The resistance distributions across the array of CNT devices with respect to different DEP parameters are characterized. The CNT devices are then operated as liquid‐gated CNT field‐effect‐transistors (LG‐CNTFET) in liquid environment. Current dependency to the gate voltage of up to two orders of magnitude is recorded. Finally, the sensors are validated by studying the pH dependency of the LG‐CNTFET conductance and it is demonstrated that 73% of the CNT sensors of a given microsystem show a resistance decrease upon increasing the pH value.     

Sustainable Solid‐State Supercapacitors Made of 3D‐Poly(3,4‐ethylenedioxythiophene) and κ‐Carrageenan Biohydrogel

3D‐Poly(3,4‐ethylenedioxythiophene) (PEDOT) electrodes are prepared using the multi‐step template‐assisted approach. Specifically, poly(lactic acid) nano‐ and microfibers collected on a previously polymerized PEDOT film are used as templates for PEDOT nano‐ and microtubes, respectively. Morphological analysis of the samples indicates that 3D‐PEDOT electrodes obtained using a low density of templates, in which nano‐ and microtubes are clearly identified, exhibit higher porosity, and specific surface than conventional 2D‐PEDOT electrodes. However, a pronounced leveling effect is observed when the density of templates is high. Thus, electrodes with microtubes still present a 3D‐morphology but much less marked than those prepared using a low density of PLA microfibers, whereas the morphology of those with nanotubes is practically identical to that of films. Electrochemical studies prove that solid supercapacitors prepared using 3D‐PEDOT electrodes and κ‐carrageenan biohydrogel as electrolytic medium, exhibit higher ability to exchange charge reversibly and to storage charge than the analogues prepared with 2D‐electrodes. Furthermore, solid devices prepared using 3D‐electrodes and κ‐carrageenan biohydrogel exhibit very similar specific capacitances that those obtained using the same electrodes and a liquid electrolyte (i.e., acetonitrile solution with 0.1 M LiClO₄). These results prove that the success of 3D‐PEDOT electrodes is independent of the electrolytic medium.

     

Co-Assembly of Carbon Nanotube Porins into Biomimetic Peptoid Membranes (Small 21/2023)

Robust and cost-effective membrane-based separations are essential to solving many global crises, such as the lack of clean water. Even though the current polymer-based membranes are widely used for separations, their performance and precision can be enhanced by using a biomimetic membrane architecture that consists of highly permeable and selective channels embedded in a universal membrane matrix. Researchers have shown that artificial water and ion channels, such as carbon nanotube porins (CNTPs), embedded in lipid membranes can deliver strong separation performance. However, their applications are limited by the relative fragility and low stability of the lipid matrix. In this work, we demonstrate that CNTPs can co-assemble into two dimension (2D) peptoid membrane nanosheets, opening up a way to produce highly programmable synthetic membranes with superior crystallinity and robustness. A combination of molecular dynamics (MD) simulations, Raman spectroscopy, X-ray diffraction (XRD), and atomic force microscopy (AFM) measurements to verify the co-assembly of CNTP and peptoids are used and show that it does not disrupt peptoid monomer packing within the membrane. These results provide a new option for designing affordable artificial membranes and highly robust nanoporous solids.     

Nanoscale Charge Percolation Analysis in Polymer‐Sorted (7,5) Single‐Walled Carbon Nanotube Networks

The current percolation in polymer‐sorted semiconducting (7,5) single‐walled carbon nanotube (SWNT) networks, processed from solution, is investigated using a combination of electrical field‐effect measurements, atomic force microscopy (AFM), and conductive AFM (C‐AFM) techniques. From AFM measurements, the nanotube length in the as‐processed (7,5) SWNTs network is found to range from ≈100 to ≈1500 nm, with a SWNT surface density well above the percolation threshold and a maximum surface coverage ≈58%. Analysis of the field‐effect charge transport measurements in the SWNT network using a 2D homogeneous random‐network stick‐percolation model yields an exponent coefficient for the transistors OFF currents of 16.3. This value is indicative of an almost ideal random network containing only a small concentration of metallic SWNTs. Complementary C‐AFM measurements on the other hand enable visualization of current percolation pathways in the xy plane and reveal the isotropic nature of the as‐spun (7,5) SWNT networks. This work demonstrates the tremendous potential of combining advanced scanning probe techniques with field‐effect charge transport measurements for quantification of key network parameters including current percolation, metallic nanotubes content, surface coverage, and degree of SWNT alignment. Most importantly, the proposed approach is general and applicable to other nanoscale networks, including metallic nanowires as well as hybrid nanocomposites.     

Highly Selective Dispersion of Carbon Nanotubes by Using Poly(phenyleneethynylene)‐Guided Supermolecular Assembly

Isolation of single‐walled carbon nanotubes (SWNTs) with specific chirality and diameters is critical for achieving optimum performance of SWNTs in various applications. A water‐soluble π‐conjugated polymer, poly[(m‐phenyleneethynylene)‐alt‐(p‐phenyleneethynylene)], 3 , is found to exhibit high selectivity in dispersing SWNT (6,5). The polymer's ability to sort out SWNT (6,5) appears to be related to the carbon–carbon triple bond, whose free rotation allows a unique assembly of chromophores in a helical conformation. The observation is consistently supported by fluorescence, Raman, and UV‐vis‐NIR absorption spectra. The intriguing selectivity of 3 to SWNT (6,5), however, is not observed for the vinylene analogue polymer 1 , showing that the carbon–carbon triple bond could play a unique role in sorting out a specific SWNT. The observed selectivity from 3 could be attributed to a combination of the helical cavity size restrain and electronic interaction associated with the local chromophore arrangement. This strategy could be expanded for efficient SWNT sorting when the helical conformation is further finely tuned.