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Partial nitrification (PN) in sequencing batch reactors (SBR) was investigated in the presence of cadmium to simulate treatment of landfill leachate containing heavy metals. Different pH conditions were investigated in the SBR to determine the optimum pH to establish PN, which was 7.5. After successful establishment of the PN process, different concentrations of cadmium (Cd) were added into the SBR to evaluate the heavy metal influence on the PN process. The results showed that PN activities were not affected by low concentrations of Cd (

A combination of approaches, including volatile organic compound (VOC) metabolomics, enzymatic activity and morphological investigations, are employed to provide insights on the toxic interactions among carbon-based nanomaterials and fungi. The model fungi investigated are Aspergillus niger and Aspergillus flavus. Their exposure to graphene (G) and graphene oxide (GO) presents 62% reduction in biomass and abnormal hyphae aspect. The stress response of these microorganisms in the presence of these nanomaterials is further determined by overall cell changes through apoptosis analyses and production of reactive oxygen species (ROS) by the fungal hyphae. The ROS production by these microorganisms exposed to the nanomaterials confirms cellular oxidative stress, which explains the apoptotic-like cell death observed in the presence of the nanomaterials. This fungal response is also linked to lower production of several important enzymes involved in the catabolism of nutrients for cell growth, such as acid phosphatase, Naphthol-ASBI phosphohydrolase, β-glucosidase and β-galactosidase. The presence of these nanomaterials also triggers changes in the production of VOC by the fungi. These changes are indicative of stress conditions since these compounds have significant roles in fungal metabolism. Overall, A. niger was more sensitive to GO and A. flavus was more sensitive to G.

The synthesis of biocompatible polymers for coating applications has gained significant attention in recent years due to the increasing spread of infectious diseases via contaminated surfaces. One strategy to combat this problem is to apply antimicrobial coatings to surfaces prone to microbial contamination. This study presents a series of biomimetic polymers that can be used as adhesives to immobilize known antimicrobial agents on the surfaces as coatings. Several polymers containing dopamine methacrylate as co-polymers were synthesized and investigated as adhesives for the deposition of an antimicrobial polymer (polyethyleneimine) and antimicrobial nanoparticles (graphene, graphene oxide and molybdenum trioxide) onto glass surfaces. The results showed that different antimicrobials required different types of adhesives for effective coating. Overall, the coatings fabricated from these composites were shown to inactivate E. coli and B. subtilis within 1 h. These coatings were also effective to prevent biofilm growth and demonstrated to be non-toxic to the human corneal epithelial cell line (htCEpi). Leaching tests of the coatings proved that the coatings were stable under biological conditions.

Graphene’s unique physical structure, as well as its chemical and electrical properties, make it ideal for use in sensor technologies. In the past years, novel sensing platforms have been proposed with pristine and modified graphene with nanoparticles and polymers. Several of these platforms were used to immobilize biomolecules, such as antibodies, DNA, and enzymes to create highly sensitive and selective biosensors. Strategies to attach these biomolecules onto the surface of graphene have been employed based on its chemical composition. These methods include covalent bonding, such as the coupling of the biomolecules via the 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide reactions, and physisorption. In the literature, several detection methods are employed; however, the most common is electrochemical. The main reason for researchers to use this detection approach is because this method is simple, rapid and presents good sensitivity. These biosensors can be particularly useful in life sciences and medicine since in clinical practice, biosensors with high sensitivity and specificity can significantly enhance patient care, early diagnosis of diseases and pathogen detection. In this review, we will present the research conducted with antibodies, DNA molecules and, enzymes to develop biosensors that use graphene and its derivatives as scaffolds to produce effective biosensors able to detect and identify a variety of diseases, pathogens, and biomolecules linked to diseases.

The present study reports two routes to modify reduced graphene oxide (rGO) nanosheets with polysulfone (PSU) brushes via nitrene chemistry. The PSU polymer is bonded to rGO at the extremity (rGO-PSU end) and at the middle of the PSU chain (rGO-PSU mid). The resulting rGO-PSU synthetic products are carefully characterized by Raman and FTIR spectroscopy, XPS, TEM, and thermogravimetric analysis, evidencing the successful grafting of PSU onto rGO surfaces. The long-term stability of these nanosheets is also determined in common solvents. The antibacterial properties of polymer-functionalized rGO against the planktonic Bacilus subtilis and Escherichia coli are also investigated. It is established that the antimicrobial properties of these nanocomposites are due to the production of reactive oxygen species. The results also demonstrate that rGO-PSU mid presents better antimicrobial properties due to shorter polymer chains, which improves the contact of the microorganisms with the graphene surface. This work was financially supported by the Spanish Ministry of Economy and Competitiveness (MAT2014-57557-R), and partially supported by the U.S. National Science Foundation Career Award (NSF Award #104093). R.O. would like acknowledge support from U.S. National Science Foundation (CMMI-1538730 and DUE-CMMI-1538730/1003574). Janire Peña wants to acknowledge mobility grant from Carlos III University and Instituto Tecnológico de Química y Materiales “Alonso Barba”. Authors acknowledge Dr. A. Esteban-Arranz for giving access to ATR equipment.

Nanocomposites containing graphene oxide (GO), polyethyleneimine (PEI), and chitosan (CS) were synthesized for chromium(VI) and copper(II) removal from water. Response surface methodology (RSM) was used for the optimization of the synthesis of the CS–PEI–GO beads to achieve simultaneous maximum Cr(VI) and Cu(II) removals. The RSM experimental design involved investigating different concentrations of PEI (1.0–2.0%), GO (500–1500 ppm), and glutaraldehyde (GLA) (0.5–2.5%), simultaneously. Batch adsorption experiments were performed to obtain responses in terms of percent removal for both Cr(VI) and Cu(II) ions. A second-order polynomial equation was used to model the relationship between the synthesis conditions and the adsorption responses. High R2 values of 0.9848 and 0.8327 for Cr(VI) and Cu(II) removal, respectively, were obtained from the regression analyses, suggesting good correlation between observed experimental values and predicted values by the model. The optimum bead composition contained 2.0% PEI, 1500 ppm GO, and 2.08% GLA, and allowed Cr(VI) and Cu(II) removals of up to 91.10% and 78.18%, respectively. Finally, characterization of the structure and surface properties of the optimized CS–PEI–GO beads was carried out using X-ray diffraction (XRD), porosity and BET surface area analysis, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), which showed favorable adsorbent characteristics as given by a mesoporous structure with high surface area (358 m2 g−1) and plenty of surface functional groups. Overall, the synthesized CS–PEI–GO beads were proven to be effective in removing both cationic and anionic heavy metal pollutants.

This study investigates the acute toxicity of graphene to sludge microbial communities. The acute toxicity was investigated with concentrations varying from low to relatively high concentrations of graphene (between 0 and 300 mg L−1) to understand the impact of different concentrations of graphene on the biological wastewater treatment process. The experiments were performed with a 10 h continuous aeration using batch reactors to simulate the wastewater biological treatment process. Results showed that increasing concentrations of graphene in the reactors led to decreasing COD, BOD5, ammonia and phosphate removals. In addition, abundances of ammonia oxidizing bacteria, ammonia monooxygenase and phosphate accumulating bacteria decreased along with the overall sludge microbial metabolic activity. The 16S rRNA deep sequencing of the sludge microbial community exposed to different concentrations of graphene showed that the abundances of the two most abundant phyla, i.e. Proteobacteria and Bacteriodetes, changed with increasing concentrations of graphene. The results also showed that releases of graphene concentrations at 10 mg L−1 and higher seem to present a short term impact in the wastewater treatment process.

The present study compares for the first time the effects of h-MoO3 and α-MoO3 against two fungal strains: Aspergillus niger and Aspergillus flavus. The h-MoO3 nanoparticles were more toxic to both fungi than α-MoO3. The toxic effects of h-MoO3 were more pronounced toward A. flavus, which presented a growth inhibition of 67.4% at 200 mg L-1. The presence of the nanoparticles affected drastically the hyphae morphology by triggering nuclear condensation and compromising the hyphae membrane. Further analysis of the volatile organic compounds (VOCs) produced by both fungi in the presence of the nanomaterials indicated important metabolic changes related to programmed cell death. These nanomaterials induced the production of specific antifungal VOCs, such as β-Elemene and t-Cadinol, by the fungi. The production of essential enzymes involved in fungal metabolism, such as acid phosphatase, naphthol-As-BI-phosphohydrolase, β-galactosidase, β-glucosidase and N-acetyl-β-glucosaminidase, reduced significantly in the presence of the nanomaterials. The changes in enzymatic production and VOCs corroborate the fact that these nanoparticles, especially h-MoO3, exert changes in the fungal metabolism, triggering apoptotic-like cell death responses in these fungi.

Adhesion of bacteria to interfaces is the first step in pathogenic infection, in biofilm formation, and in bioremediation of oil spills and other pollutants. Bacteria use a variety of surface structures to promote interfacial adhesion, with the level of expression of these structures varying in response to local conditions and environmental signals. Here, we investigated how overexpression of type 1 fimbriae, one such appendage, modifies the ability of Escherichia coli to adhere to solid substrates, via biofilm formation and yeast agglomeration, and to oil/water interfaces, via a microbial adhesion to hydrocarbon assay. A plasmid that enables inducible expression of E. coli MG1655 type 1 fimbriae was transformed into fimbriae-deficient mutant strain MG1655ΔfimA. The level of fimH gene expression in the engineered strain, measured using quantitative real-time PCR, could be tuned by changing the concentration of inducer isopropyl β-d-1-thiogalactopyranoside (IPTG), and was higher than that in strain MG1655. Increasing the degree of fimbriation only slightly modified the surface energy and zeta potential of the bacteria, but enhanced their ability to agglomerate yeast cells and to adhere to solid substrates (as measured by biofilm formation) and to oil/water interfaces. We anticipate that the tunable extent of fimbriation accessible with this engineered strain can be used to investigate how adhesin expression modifies the ability of bacteria to adhere to interfaces and to actively self-assemble there.

The present study investigates the chronic toxicity of graphene (G) and graphene oxide (GO) in activated sludge. Sequencing batch bioreactors were fed with influents containing 0, 1 and 5 mg L−1 of GO or G (12 h cycles) for ten days. Reduction in performance of the bioreactors in relation to chemical oxygen demand, ammonia and phosphate removals was observed after three days in the bioreactors fed with 5 mg L−1 of nanomaterials. After about eight days, these reactors reached a steady state nutrient removal, which corresponded to recovery of certain groups of ammonia oxidizing bacteria and phosphate accumulating bacteria despite the increasing accumulation of nanomaterials in the sludge. These results suggested that biological treatment can be affected transiently by initial exposure to the nanomaterials, but certain groups of microorganisms, less sensitive to these nanomaterials, can potentially strive in the presence of these nanomaterials. Results of 16S rRNA gene deep sequencing showed that G and GO affected differently the microbial communities in the activated sludge. Between the two nanomaterials investigated, GO presented the highest impact in nutrient removal, gene abundance and changes in microbial population structures.

In this work, we demonstrate the non-synthetic surface modification of a co-extruded multilayer poly(methyl methacrylate) (PMMA)/poly(ϵ-caprolactone) (PCL) film with gas barrier properties through electrospinning of polystyrene (PS)/multi-walled carbon nanotube (MWNT) nanofibers. As produced by forced assembly layer multiplying co-extrusion, the heterogeneous nucleating crystallization of PCL was induced using the glassy confinement of the amorphous PMMA thus creating in-plane lamellae crystallization, which is impermeable to most gas molecules. To complement these intrinsic gas barrier properties of the multilayer film, electrospun PS/MWNT nanofibers were deposited onto the surface of the PMMA/PCL film, which increased the surface roughness and resulted in superhydrophobic behavior (water contact angles>150°). Furthermore, the inclusion of the MWNT in the matrix caused an increasing antibacterial efficacy, which was determined to reach 97% inactivation against gram-positive bacteria Bacillus subtilis. The fiber mats were further characterized using scanning electron microscopy (SEM), Raman spectroscopy, and thermogravimetric analysis (TGA).