Selective protein transport through ultra-thin suspended reduced graphene oxide nanopores

Rechargeable Multifunctional Anti-Bacterial AEMs for Electrodialysis: Improving Anti-Biological Performance via Synergistic Antibacterial Mechanism

Constructing a functional layer on the surface of commercial membrane (as a substrate) to inhibit the formation of biofilms is an efficient strategy to prepare an antibacterial anion exchange membrane (AEM). Herein, a rechargeable multifunctional anti-biological system is reported by utilizing the mussel-inspired L-dopa connection function on commercial AEMs. Cobalt nanoparticles (Co NPs) and N-chloramine compounds are deposited on the AEM surface by a two-step modification procedure. The anti-biofouling abilities of the membranes are qualitatively and quantitatively analyzed by adopting common Gram-negative (E. coli) and Gram-positive (S. aureus & Bacillus) bacteria as model biofouling organisms. The optimized membrane exhibits a high stability concerning the NaCl solution separation performance within 240 min. Meantime, the mechanism of the anti-adhesion is un-veiled at an atomic level and molecular dynamics (MD) simulation are conducted to measure the interaction, adsorption energy and average loading by using lipopolysaccharide (LPS) of E. coli. In view of the superior performance of antibacterial surfaces, it is believed that this work could provide a valuable guideline for the design of membrane materials with resistance to biological contamination.

From nanohole to ultralong straight nanochannel fabrication in graphene oxide with swift heavy ions

Porous architectures based on graphene oxide with precisely tailored nm-sized pores are attractive for biofluidic applications such as molecular sieving, DNA sequencing, and recognition-based sensing. However, the existing pore fabrication methods are complex, suffer from insufficient control over the pore density and uniformity, or are not scalable to large areas. Notably, creating vertical pores in multilayer films appears to be particularly difficult. Here, we show that uniform 6-7 nm-sized holes and straight, vertical nanochannels can be formed by simply irradiating graphene oxide (GO) films with high-energy heavy ions. Long penetration depths of energetic ions in combination with localized energy deposition and effective self-etching processes enable the creation of through pores even in 10 µm-thick GO films. This fully scalable fabrication provides a promising possibility for obtaining innovative GO track membranes.

Experimental study on single biomolecule sensing using MoS2-graphene heterostructure nanopores

Solid-state nanopores play an important role in sensing single-biomolecules such as DNA and proteins. However, an ultra-short translocation time hinders nanopores from acquiring more detailed information about biomolecules, and further applications such as sequencing and molecular structure analysis are limited. Related studies have shown that MoS₂ has no obvious impediment to biomolecule translocation while graphene may cause obstacles to this process. By combining these two-dimensional materials, nanopores might slow the biomolecule passage. Herein, we fabricated sub-10 nm ultra-thin MoS₂-graphene heterostructure nanopores with high stability and tested both dsDNA and native protein (BSA) at the single-molecule level in experiments for the first time. Some special signals with advanced order are observed, which may reflect the shape change of the BSA molecules during the slow translocation process. The results show that the translocation time of BSA is slowed down up to more than 100 ms and the signal length and form are determined by the extent of interaction between the BSA and the heterostructure nanopore. The weak interaction between the BSA and the MoS₂ layer increases the translocation probability, and meanwhile, the strong interaction of the graphene layer to BSA slows down the translocation and changes its structure. Therefore, our findings indicate the possibilities of slowing down the single-biomolecule translocation and the capability of acquiring more detailed information about biomolecules using MoS₂-graphene heterostructure nanopores.

Nanodiagnostics: A review of the medical capabilities of nanopores

Modern diagnostics strive to be accurate, fast, and inexpensive in addition to properly identifying the presence of a disease, infection, or illness. Early diagnosis is key; catching a disease in its early stages can be the difference between fatality and treatment. The challenge with many diseases is that detectability of the disease scales with disease progression. Since single molecule sensors, e.g., nanopores, can sense biomolecules at low concentrations, they have the potential to become clinically relevant in many of today's medical settings. With nanopore-based sensing, lower volumes and concentrations are required for detection, enabling it to be clinically beneficial. Other advantages to using nanopores include that they are tunable to an enormous variety of molecules and boast low costs, and fabrication is scalable for manufacturing. We discuss previous reports and the potential for incorporating nanopores into the medical field for early diagnostics, therapeutic monitoring, and identifying relapse/recurrence.

Transfer of printed electronic structures using graphene oxide and gelatin enables reversible and biocompatible interface with living cells

We present a low-cost, easy-to-implement platform for printing materials and interfacing them with eukaryotic cells. We show that thermal or chemical reduction of a graphene oxide thin film allows water-assisted delamination of the film from glass or plastic. The chemical and physical properties and permeability of the resulting film are dependent on the method of reduction and deposition of the graphene oxide, with thermal reduction removing more oxidized carbon functionality than chemical reduction. We also developed a method to attach the films onto cell surfaces using a thin layer of gelatin as an adhesive. In general, the films are highly impermeable to nutrients and we observed a significant amount of cell death when gelatin was not used; gelatin enables diffusion of nutrients for sustained cell viability. The combination of nanoscale membranes with a low melting point biopolymer allows us to reversibly interface cells with cargo transferred by graphene oxide while maintaining cell viability. To demonstrate delivery of electronic structures, we modified a commercial off-the-shelf printer to print a silver-based ink directly onto the reduced graphene oxide films which we then transferred to the surface of the cells.

Self-assembled membrane composed of amyloid-like proteins for efficient size-selective molecular separation and dialysis

The design and scalable construction of robust ultrathin protein membranes with tunable separation properties remain a key challenge in chemistry and materials science. Here, we report a macroscopic ultrathin protein membrane with the potential for scaled-up fabrication and excellent separation efficiency. This membrane, which is formed by fast amyloid-like lysozyme aggregation at air/water interface, has a controllable thickness that can be tuned to 30–250 nm and pores with a mean size that can be tailored from 1.8 to 3.2 nm by the protein concentration. This membrane can retain > 3 nm molecules and particles while permitting the transport of small molecules at a rate that is 1~4 orders of magnitude faster than the rate of existing materials. This membrane further exhibits excellent hemodialysis performance, especially for the removal of middle-molecular-weight uremic toxins, which is 5~6 times higher in the clearance per unit area than the typical literature values reported to date.

Membrane separation is important for a range of industrial and medical applications. Here, the authors report on the formation of self-assembled protein membranes for size selective separation and demonstrate application in the separation of dyes, nanoparticles and in hemodialysis.

Single-File Protein Translocations through Graphene-MoS2 Heterostructure Nanopores

Successfully threading unfolded protein molecules through nanopores whose sizes are comparable to that of an amino acid is a prerequisite for the nanopore-based protein sequencing method that promises to be high-throughput and low-cost. While the electric driving method can be effective for a homogeneously charged DNA molecule, it fails to drive an unfolded protein through a nanopore because the net charge of a protein fragment inside of the pore (where the electric field exists) can be positive, negative, or neutral. Here we propose and demonstrate by molecular dynamics simulations protein transport through a nanopore in a quasi-two-dimensional heterostructure stacked together by graphene and molybdenum disulfide (MoS₂) nanosheets. Thanks to different van der Waals interactions ( U) between a protein molecule and different 2D surfaces, it is energetically favorable for protein to progressively move from the MoS₂ surface to the graphene surface (more negative U) through a nanopore in the heterostructure.

Water-Soluble Metalated Covalent Organic Nanobelts with Improved Bioavailability for Protein Transportation

An available pathway to prepare the ionized covalent organic nanosheets (iCONs) has been proposed by a metal-assisted aqueous-phase exfoliation route from covalent organic frameworks. The soluble and belt-shaped iCONs could immobilize a large quantity of proteins (2.73 mg/mg, BSA/iCONs) and hence serve as transporters to enhance the protein uptake by cancer cells. Meanwhile, their energy-dependent endocytosis pathway via clathrin-coated pits has been proved as well.

A new paradigm on the chemical potentials of components in multi-component nano-phases within multi-phase systems

A new paradigm is offered claiming that the thermodynamic nano-effect in multi-component and multiphase systems is proportional to the increased surface areas of the phases and not to their increased curvatures (as the Kelvin paradigm claims).