Electrochemical-repaired porous graphene membranes for precise ion-ion separation.

The preparation of atom-thick porous lattice hosting Å-scale pores is attractive to achieve a large ion-ion selectivity in combination with a large ion flux. Graphene film is an ideal selective layer for this if high-precision pores can be incorporated, however, it is challenging to avoid larger non-selective pores at the tail-end of the pore size distribution which reduces ion-ion selectivity. Herein, we develop a strategy to overcome this challenge using an electrochemical repair strategy that successfully masks larger pores in large-area graphene. 10-nm-thick electropolymerized conjugated microporous polymer (CMP) layer is successfully deposited on graphene, thanks to a strong π-π interaction in these two materials. While the CMP layer itself is not selective, it effectively masks graphene pores, leading to a large Li+/Mg2+ selectivity from zero-dimensional pores reaching 300 with a high Li+ ion permeation rate surpassing the performance of reported materials for ion-ion separation. Overall, this scalable repair strategy enables the fabrication of monolayer graphene membranes with customizable pore sizes, limiting the contribution of nonselective pores, and offering graphene membranes a versatile platform for a broad spectrum of challenging separations.

Advancing Molecular Sieving via Å-Scale Pore Tuning in Bottom-Up Graphene Synthesis.

Porous graphene films are attractive as a gas separation membrane given that the selective layer can be just one atom thick, allowing high-flux separation. A favorable aspect of porous graphene is that the pore size, essentially gaps created by lattice defects, can be tuned. While this has been demonstrated for postsynthetic, top-down pore etching in graphene, it does not exist in the more scalable, bottom-up synthesis of porous graphene. Inspired by the mechanism of precipitation-based synthesis of porous graphene over catalytic nickel foil, we herein conceive an extremely simple way to tune the pore size. This is implemented by increasing the cooling rate by over 100-fold from -1 °C min-1 to over -5 °C s-1. Rapid cooling restricts carbon diffusion, resulting in a higher availability of dissolved carbon for precipitation, as evidenced by quantitative carbon-diffusion simulation, measurement of carbon concentration as a function of nickel depth, and imaging of the graphene nanostructure. The resulting enhanced grain (inter)growth reduces the effective pore size which leads to an increase of the H2/CH4 separation factor from 6.2 up to 53.3.

Bottom-up synthesis of graphene films hosting atom-thick molecular-sieving apertures.

Incorporation of a high density of molecular-sieving nanopores in the graphene lattice by the bottom-up synthesis is highly attractive for high-performance membranes. Herein, we achieve this by a controlled synthesis of nanocrystalline graphene where incomplete growth of a few nanometer-sized, misoriented grains generates molecular-sized pores in the lattice. The density of pores is comparable to that obtained by the state-of-the-art postsynthetic etching (1012 cm-2) and is up to two orders of magnitude higher than that of molecular-sieving intrinsic vacancy defects in single-layer graphene (SLG) prepared by chemical vapor deposition. The porous nanocrystalline graphene (PNG) films are synthesized by precipitation of C dissolved in the Ni matrix where the C concentration is regulated by controlled pyrolysis of precursors (polymers and/or sugar). The PNG film is made of few-layered graphene except near the grain edge where the grains taper down to a single layer and eventually terminate into vacancy defects at a node where three or more grains meet. This unique nanostructure is highly attractive for the membranes because the layered domains improve the mechanical robustness of the film while the atom-thick molecular-sized apertures allow the realization of large gas transport. The combination of gas permeance and gas pair selectivity is comparable to that from the nanoporous SLG membranes prepared by state-of-the-art postsynthetic lattice etching. Overall, the method reported here improves the scale-up potential of graphene membranes by cutting down the processing steps.

Highly efficient enrichment and identification of pathogens using a herringbone microfluidic chip and by MALDI-TOF mass spectrometry.

Bacterial infections cause considerable morbidity and expensive healthcare costs. The prescription of broad-spectrum antimicrobial drugs results in failure of treatment or overtreatment and exacerbates the spread of multidrug-resistant pathogens. There is an emergent demand for rapid and accurate methods to identify pathogens and conduct personalized therapy. Here, we develop a herringbone microfluidic chip integrated with vancomycin modified magnetic beads (herringbone-VMB microchip) to enrich pathogens. The enriched pathogens are identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry. The herringbone-VMB microchip applies passive mixing of bacterial samples by generating microvortices, which significantly enhances the interaction between bacteria and vancomycin modified magnetic beads and leads to more efficient enrichment compared to in-tube extraction. Four common pathogens in urinary tract infections are utilized to validate the method, and the capture efficiency of the bacteria from urine is up to 90%. The whole procedure takes 1.5 hours from enrichment to identification. This method shows potential in shortening the turnaround time in the clinical diagnosis of bacterial infections.

Direct MALDI-TOF profiling of gingival crevicular fluid sediments for periodontitis diagnosis.

Periodontitis is a widespread stomatological disease and represents one of the main causes of tooth loss in adults. Traditional diagnosis of periodontitis relies on the judgment by professional periodontists that cannot reveal its progression at the early stage. In this work, we characterized the gingival crevicular fluid (GCF) sediments of patients with periodontitis and healthy volunteers by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Potential protein biomarkers were selected based on the multivariate statistical analysis of the MALDI-TOF mass spectra, followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) identification. Twelve potential protein biomarkers were identified from 17 patients compared to 7 healthy volunteers, including 5 microbial proteins and 7 human proteins, indicating the microbial composition and host response components related to the etiology of periodontitis. The panel of biomarkers was then verified with the GCF samples of another 11 patients. The 12 biomarkers also showed potential value in the early diagnosis of periodontitis. This work developed a rapid assay to screen periodontitis among populations. It can be popularized to non-periodontal specialists such as community general practitioners, benefiting the early and accurate monitoring of periodontitis. The identification of the potential biomarkers can also help in the understanding of the pathogenesis of periodontitis.

Magnetic targeted drug delivery carriers encapsulated with pH-sensitive polymer: synthesis, characterization and in vitro doxorubicin release studies.

Targeted and efficient delivery of drug to tumor is one of the crucial issues in cancer therapy. In this work, we have successfully designed and prepared the pH-sensitive magnetic nanoparticles (MNPs) as targeted anticancer drug carriers, in which the MNPs were coated by poly(acrylic acid) (PAA) and the obtained PAA@MNPs exhibited a size within 100 nm, good stability, and superparamagnetic responsibility (Ms 45.97 emu/g). Doxorubicin (DOX) can be successfully loaded onto MNPs via electrostatic interaction, and the drug loading content and loading efficiency are 26.4 and 88.1%, respectively. Moreover, the release studies showed that the drug-loaded carriers (MNPs-DOX) had excellent pH sensitivity, 75.6% of the loaded DOX was released at pH 4.0 within 48 h. Importantly, MTT assays in HUVEC and MCF-7 cells demonstrated that MNPs-DOX exhibited high anti-tumor activity, while the PAA@MNPs were practically nontoxic. Thus, our results revealed that PAA@MNPs would be a competitive candidate for biomedical application and MNPs-DOX could be used in targeted cancer therapy.

Facile preparation of a pH-sensitive nano-magnetic targeted system to deliver doxorubicin to tumor tissues.

We have developed a drug-loaded, pH-sensitive, nano-magnetic targeted system (DPNTS) for delivering doxorubicin (DOX) to tumor tissues through a facile route. Iron oxide (Fe3O4) nanoparticles were used as magnetically-responsive carriers, polyethyleneglycol (PEG) as the surface-modifying agent, and polyethyleneimine (PEI) as the drug-loading site whose primary amine reacts with the 13-carbonyl of DOX. The prepared DPNTS was within 20 nm and had good stability in dispersion and superparamagnetic properties. DOX was grafted to PEG/PEI@Fe3O4 at up to 85%. During in vitro release studies, nearly 81% DOX was released from DPNTS within 72 h at pH 4.5, compared with only 28% at pH 7.4.