Single-Molecule Discrimination of Saccharides Using Carbon Nitride Nanopores.

Structural complexity brings a huge challenge to the analysis of sugar chains. As a single-molecule sensor, nanopores have the potential to provide fingerprint information on saccharides. Traditionally, direct single-molecule saccharide detection with nanopores is hampered by their small size and weak affinity. Here, a carbon nitride nanopore device is developed to discern two types of trisaccharide molecules (LeApN and SLeCpN) with minor structural differences. The resolution of LeApN and SLeCpN in the mixture reaches 0.98, which has never been achieved in solid-state nanopores so far. Monosaccharide (GlcNAcpN) and disaccharide (LacNAcpN) can also be discriminated using this system, indicating that the versatile carbon nitride nanopores possess a monosaccharide-level resolution. This study demonstrates that the carbon nitride nanopores have the potential for conducting structure analysis on single-molecule saccharides.

High Spatial Resolution of Ultrathin Covalent Organic Framework Nanopores for Single-Molecule DNA Sensing.

Ultrathin nanosheets of two-dimensional covalent organic frameworks covered a quartz nanopipette and then acted as a nanopore device for single-molecule DNA sensing. Our results showed that a single DNA homopolymer as short as 6 bases could be detected. The dwell times of 30-mer DNA homopolymers were obviously longer than the times of 10- or 6-mer ones. For different bases, poly(dA)6 showed the slowest transport speed (∼595 µs/base) compared with cytosine (∼355 µs/base) in poly(dC)6 and thymine (∼220 µs/base) in poly(dT)6. Such translocation speeds are the slowest ever reported in two-dimensional material-based nanopores. Poly(dA)6 also showed the biggest current blockade (94.74 pA) compared with poly(dC)6 (79.54 pA) and poly(dT)6 (71.41 pA). However, the present difference in blockade current was not big enough to distinguish the four DNA bases. Our study exhibits the shortest single DNA molecules that can be detected by COF nanopores at the present stage and lights the way for DNA sequencing based on solid-state nanopores.

Facile preparation of magnetic composites based on carbon nanotubes: Utilization for removal of environmental pollutants.

The preparation of multifunctional composites that combine magnetic nanoparticles and supported nanomaterials has attracted great attention for various applications. In this work, a facile method was developed for the preparation of carbon nanotube (CNT)-based magnetic composites through a one-pot oxidation method using K2FeO4 as the oxidant, which was subsequently used as the reagent to generate the Fe3O4 nanoparticles and fabricate the magnetic CNT composites. This strategy could be performed at room temperature, so it is very mild and straightforward. The properties and structure of the as-fabricated CNT-Fe3O4 composites were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and vibrating sample magnetometry. The results suggested that this approach not only generated Fe3O4 magnetic nanoparticles on the surface of the CNTs but also produced a series of functional groups. In addition, the dried CNT-Fe3O4 composites were highly dispersible in water or organic solutions, and they also had a magnetic response that could satisfy the demand for magnetic separation. Finally, we adsorbed copper ions (Cu2+) and methylene blue (MB) using the CNT-Fe3O4 composites as adsorbents. The results indicated that the obtained composites could adsorb both Cu2+ and MB effectively. Taken together, we report a novel strategy for the fabrication of magnetic carbon nanotube composites through a facile oxidation and subsequent deposition procedure. These magnetic composites show great potential for the removal of environmental pollutants.

Injectable hyperbranched poly(ß-amino ester) hydrogels with on-demand degradation profiles to match wound healing processes.

Adjusting biomaterial degradation profiles to match tissue regeneration is a challenging issue. Herein, biodegradable hyperbranched poly(ß-amino ester)s (HP-PBAEs) were designed and synthesized via "A2 + B4" Michael addition polymerization, and displayed fast gelation with thiolated hyaluronic acid (HA-SH) via a "click" thiol-ene reaction. HP-PBAE/HA-SH hydrogels showed tunable degradation profiles both in vitro and in vivo using diamines with different alkyl chain lengths and poly(ethylene glycol) diacrylates with varied PEG spacers. The hydrogels with optimized degradation profiles encapsulating ADSCs were used as injectable hydrogels to treat two different types of humanized excisional wounds - acute wounds with faster healing rates and diabetic wounds with slower healing and neo-tissue formation. The fast-degrading hydrogel showed accelerated wound closure in acute wounds, while the slow-degrading hydrogel showed better wound healing for diabetic wounds. The results demonstrate that the new HP-PBAE-based hydrogel in combination with ADSCs can be used as a well-controlled biodegradable skin substitute, which demonstrates a promising approach in the treatment of various types of skin wounds.

A hybrid injectable hydrogel from hyperbranched PEG macromer as a stem cell delivery and retention platform for diabetic wound healing.

The injectable hydrogel with desirable biocompatibility and tunable properties can improve the efficacy of stem cell-based therapy. However, the development of injectable hydrogel remains a great challenge due to the restriction of crosslinking efficiency, mechanical properties, and potential toxicity. Here, we report that a new injectable hydrogel system was fabricated from hyperbranched multi-acrylated poly(ethylene glycol) macromers (HP-PEGs) and thiolated hyaluronic acid (HA-SH) and used as a stem cell delivery and retention platform. The new HP-PEGs were synthesized via in situ reversible addition fragmentation chain transfer (RAFT) polymerization using an FDA approved anti-alcoholic drug-Disulfiram (DS) as the RAFT agent precursor. HP-PEGs can form injectable hydrogels with HA-SH rapidly via thiol-ene click reaction under physiological conditions. The hydrogels exhibited stable mechanical properties, non-swelling and anti-fouling properties. Hydrogels encapsulating adipose-derived stem cells (ADSCs) have demonstrated promising regenerative capabilities such as the maintenance of ADSCs' stemness and secretion abilities. The ADSCs embedded hydrogels were tested on the treatment of diabetic wound in a diabetic murine animal model, showing enhanced wound healing. STATEMENT OF SIGNIFICANCE: Diabetic wounds, which are a severe type of diabetes, have become one of the most serious clinical problems. There is a great promise in the delivery of adipose stem cells into wound sites using injectable hydrogels that can improve diabetic wound healing. Due to the biocompatibility of poly(ethylene glycol) diacrylate (PEGDA), we developed an in situ RAFT polymerization approach using anti-alcoholic drug-Disulfiram (DS) as a RAFT agent precursor to achieve hyperbranched PEGDA (HP-PEG). HP-PEG can form an injectable hydrogel by crosslinking with thiolated hyaluronic acid (HA-SH). ADSCs can maintain their regenerative ability and be delivered into the wound sites. Hence, diabetic wound healing process was remarkably promoted, including inhibition of inflammation, enhanced angiogenesis and re-epithelialization. Taken together, the ADSCs-seeded injectable hydrogel may be a promising candidate for diabetic wound treatment.