Unveiling the Role of Fractionated Graphene Oxide in Nitric Oxide Scavenging

The feasibility of saturating aqueous anoxic solutions with in situ-generated high-purity nitric oxide (NO) is shown herein. A methemoglobin assay estimated the average nitric oxide concentration to be ca. 20 ± 3 µM. Graphene oxide aqueous dispersions were prepared by ultrasound-assisted extra exfoliation. These dispersions, including unpurified (pristine) samples and samples purified from transition metal impurities (bulk) fractions (bulkGO) and (nano) separated fractions (nanoGO) in a range of 0.5 to 14 kDa were prepared with ppm level concentrations. A robust and reproducible chemiluminescence (CL) assay validated the interaction between graphene oxide and NO in a luminol-based system. The results showed a significant increase in NO scavenging activity within the bulkGO fractions to nanofractions ranging from 14 to 3.5 kDa. The different reaction pathways underlying the transformation of nitric oxide are being evaluated, focusing on understanding how its presence or absence affects these processes. Our kinetic model suggests a significant difference in nitric oxide regulation; nanoGO demonstrates an interception rate seventy-times higher than that achieved through CL quenching.

Goharshadi E, Boghossian AA. Micropreparative Gel Electrophoresis for Purification of Nanoscale Bioconjugates

Conventional techniques for purifying macromolecular conjugates often require complex and costly installments that are inaccessible to most laboratories. In this work, we develop a one-step micropreparative method based on a trilayered polyacrylamide gel electrophoresis (MP-PAGE) setup to purify biological samples, synthetic nanoparticles, as well as biohybrid complexes. We apply this method to recover DNA from a ladder mixture with yields of up to 90%, compared to the 58% yield obtained using the conventional crush-and-soak method. MP-PAGE was also able to isolate enhanced yellow fluorescence protein (EYFP) from crude cell extract with 90% purity, which is comparable to purities achieved through a more complex two-step purification procedure involving size exclusion and immobilized metal-ion affinity chromatography. This technique was further extended to demonstrate size-dependent separation of a commercial mixture of graphene quantum dots (GQDs) into three different fractions with distinct optical properties. Finally, MP-PAGE was used to isolate DNA-EYFP and DNA-GQD bioconjugates from their reaction mixture of DNA and EYFP and GQD precursors, samples that otherwise could not be effectively purified by conventional chromatography. MP-PAGE thus offers a rapid and versatile means of purifying biological and synthetic nanomaterials without the need for specialized equipment.

Water desalination using stainless steel meshes coated with layered double hydroxide/graphene oxide nanocomposite

Coated stainless steel meshes with layered double hydroxides and graphene oxide nanocomposites (LDH/GO) were used as desalination membranes. The nature of stainless steel mesh allows a greater amount of sorbent to be coated on the surface using sol-gel technique and increases the adsorption capacity of ions and the efficiency of desalination. These substrates improve the contact surface area so that approximately 5 min is required for the desalination process. The LDH/GO stainless steel mesh exhibited excellent corrosion resistance and tensile strength of 99.9% and 112 MPa, respectively. To achieve the best desalination efficiency, different parameters were optimized, including the ratio of GO to LDH in the nanocomposites, the number of mesh layers, NaCl concentrations, and process cycles. The maximum adsorption capacity for the NaCl was 555.5 mg g-1 . The results revealed that LDH/GO nanocomposite was able to remove (94.3 ± 0.5) % of the NaCl under the optimum conditions. The proposed method was used to successfully remove Na+ , Mg+2 , Ca+2 , and K+ cations from seawater, with the yields of 92.3%, 92.5%, 91.2%, and 90.2%, respectively. PRACTITIONER POINTS: The salts are removed via interaction between salt ions and functional groups on the LDH/GO nanocomposite surface. A high amount of adsorbent loaded on the surface of steel mesh leads to an improvement in the adsorption capacity. The sol-gel technique strengthens the LDH/GO nanocomposites on the surface of steel mesh.

Post-administration labeling with Palladium(II) ions enables ICP-MS-based determination of the biodistribution of carbonized nanogels

Carbonized nanogels (CNGs) are carbon-based nanomaterials possessing excellent antibacterial and antiviral activities for treating infectious diseases. Thus, investigations of the biodistribution of CNGs are crucial in ensuring their biosafety for in vivo applications. In this study, we combined a labeling scheme, employing tetrachloropalladate (PdCl₄^2-) ions to selectively label the administered CNGs in solubilized tissue samples, and an automatic sample pretreatment scheme, using a knotted reactor to effectively separate the PdCl₄^2--labeled CNGs from the free PdCl₄^2- ions and the tissue matrices, to enable reliable and interference-free quantification of CNGs through measuring the signal intensities of Pd using inductively coupled plasma mass spectrometry (ICP-MS). After optimizing the labeling conditions and the separation scheme, we observed that the PdCl₄^2- ions bound strongly to the CNGs (dissociation constant: 23.0 nM), with the method's detection limits reaching 1.6 fg L^-1 and 0.9 μg L^-1 within working ranges from 10^-4 to 1 μg L^-1 and from 1 to 1000 μg L^-1, respectively. We verified the reliability and applicability of this analytical method through spike analyses of solubilized rat liver, spleen, kidney, lung, brain, and blood samples (recoveries ranging from 96 to 102%) and through analyses of these rat organ and tissue samples after giving rats an intravenous dose of CNGs (2.5 mg kg^-1 body weight). The biodistribution data indicated that these administered CNGs deposited mainly in the liver, lung, and spleen at 10 min and 1 h post-administration. Our study revealed that this post-administration labeling scheme coupled with ICP-MS allows accurate determination of the biodistribution of carbonized nanomaterials.

A Mechanically Flexible Superhydrophobic Rock Wool Modified with Reduced Graphene Oxide-Chloroperene Rubber for Oil-Spill Clean-Up

The leakage of industrial oil and organic wastewater discharge has caused serious damage to the natural environment and ecology. Therefore, implementation of a low-cost and high-performance adsorbent material is of great significant. This work reports the preparation of superhydrophobic rock wool (RW) for efficient clean-up of oil and organic solvents. The modified RW is prepared by coating a commercial RW with reduced graphene oxide (RGO) nanosheets under hydrothermal treatment. To improve the adhesion between the RGO nanosheets and RW, a film of chloroperene rubber is deposited on the RW surface followed by modification with RGO. The modified RW possesses superhydrophobicity and superoleophilicity with a water contact angle of 152.4°, and it is used for separation of oil-water mixture. The modified RW exhibits excellent mechanical elasticity and durability when compared with commercial one, and the adsorbed oils are recycled by simple squeezing. Its oil adsorption capacities are maintained above 95%, after several compression cycles. Importantly, the modified RW exhibits excellent photothermal properties which are beneficial for the separation of high-viscosity oils. Owing to low costs, versatility, and scalability in production, the modified RW can be regarded as a suitable choice for large-scale oil/water separation.

Photoluminescent Nanoparticles for Chemical and Biological Analysis and Imaging

Research related to the development and application of luminescent nanoparticles (LNPs) for chemical and biological analysis and imaging is flourishing. Novel materials and new applications continue to be reported after two decades of research. This review provides a comprehensive and heuristic overview of this field. It is targeted to both newcomers and experts who are interested in a critical assessment of LNP materials, their properties, strengths and weaknesses, and prospective applications. Numerous LNP materials are cataloged by fundamental descriptions of their chemical identities and physical morphology, quantitative photoluminescence (PL) properties, PL mechanisms, and surface chemistry. These materials include various semiconductor quantum dots, carbon nanotubes, graphene derivatives, carbon dots, nanodiamonds, luminescent metal nanoclusters, lanthanide-doped upconversion nanoparticles and downshifting nanoparticles, triplet-triplet annihilation nanoparticles, persistent-luminescence nanoparticles, conjugated polymer nanoparticles and semiconducting polymer dots, multi-nanoparticle assemblies, and doped and labeled nanoparticles, including but not limited to those based on polymers and silica. As an exercise in the critical assessment of LNP properties, these materials are ranked by several application-related functional criteria. Additional sections highlight recent examples of advances in chemical and biological analysis, point-of-care diagnostics, and cellular, tissue, and in vivo imaging and theranostics. These examples are drawn from the recent literature and organized by both LNP material and the particular properties that are leveraged to an advantage. Finally, a perspective on what comes next for the field is offered.

Biodistribution of Graphene Oxide Determined through Postadministration Labeling with DNA-Conjugated Gold Nanoparticles and ICPMS

Recent research has revealed the use of graphene oxide (GO) and its derivatives as a potential biomaterial because of their attractive physicochemical characteristics and functional properties. However, if GO and related derivatives are to become useful materials for biomedical applications, it will be necessary to evaluate their biodistribution for health and safety considerations. To obtain a more accurate biodistribution for GO, we (i) developed a postadministration labeling strategy employing DNA-conjugated gold nanoparticles (DNA-AuNPs) to selectively label administered GO in Solvable-treated tissue samples and (ii) constructed an automatic sample pretreatment scheme (using a C₁₈-packed minicolumn) to effectively separate the DNA-AuNP-labeled GO from the unbound DNA-AuNPs and the dissolved tissue matrices, thereby enabling ultrasensitive, interference-free quantification of GO through measurement (inductively coupled plasma mass spectrometry) of the Au signal intensities. The DNA-AuNPs can bind to GO in a concentration- and time-dependent manner. After optimizing the labeling conditions (DNA length, incubation pH, DNA-AuNP concentration, and incubation time) and the separation scheme (sample loading flow rate, rinsing volume, and eluent composition), we found that A₂₀R₂₀-AuNPs (R₂₀: random DNA sequence including A, T, C, and G) had the strongest binding affinity for labeling of the administered GO (dissociation constant: 36.0 fM) and that the method's detection limit reached 9.3 ag L^-1 with a calibration curve having a working range from 10^-1 to 10¹⁰ fg L^-1. Moreover, this approach revealed that the intravenously administered GO accumulated predominantly in the liver and spleen at 1 and 12 h post administration, with apparent discrepancies in the concentrations measured using pre- and postadministration labeling strategies.

Enhanced electrophoretic separation of proteins by tethered SiO2 nanoparticles in an SDS-polyacrylamide gel network

Nanoparticles (NPs) are able to improve the separation efficiency of proteins in SDS-polyacrylamide gel electrophoresis (SDS-PAGE) due to their capability of enhancing heat dissipation during electrophoresis. However, the intrinsic surface charges of NPs (at buffer pH or charge induced due to the SDS coating) make them acquire electrophoretic mobility and movement in the gel. Such a movement leads to viscosity and temperature gradients in the gel and deteriorates the separation. In this work, we proposed a novel method by using tethered NPs in the gel. Silica NPs, as the model NPs, were prepared and their surfaces were modified using 3-[(methacryloxy)propyl] trimethoxysilane (MPS) which locks the NPs in the gel via covalent bonds (M-SiO₂/PA (polyacrylamide)). SiO₂ NPs were embedded into the gel (SiO₂/PA) as the positive control, while pure PA gel was chosen as the negative control. The results showed that at a relatively high voltage of 250 V, although the Joule heat generated during electrophoresis disturbed the separation in the pure gel, the SiO₂/PA and M-SiO₂/PA nanocomposite gels showed better performances. In comparison with the pure PA gel, the resolution increased by 3 and 32% for SiO₂/PA and M-SiO₂/PA, respectively, in a relatively short separation time of 35 min. The gel with tethered NPs presented a more efficient separation in terms of band broadening and resolution compared with the gel with free NPs probably due to the movement of free charged particles in the gel. Evidently, the migration speed of protein bands in the gels decreased especially for larger proteins in the presence of the NPs compared to the pristine gel due to the steric hindrance of the NPs. Finally, we separated E. coli proteins, as a real sample. Among the three gels (pure PA, SiO₂/PA, and M-SiO₂/PA), the gel containing M-SiO₂ showed the best performance.