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1.
Nat Commun ; 11(1): 319, 2020 Jan 16.
Artigo em Inglês | MEDLINE | ID: mdl-31949159

RESUMO

Optimal functioning of neuronal networks is critical to the complex cognitive processes of memory and executive function that deteriorate in Alzheimer's disease (AD). Here we use cellular and animal models as well as human biospecimens to show that AD-related stressors mediate global disturbances in dynamic intra- and inter-neuronal networks through pathologic rewiring of the chaperome system into epichaperomes. These structures provide the backbone upon which proteome-wide connectivity, and in turn, protein networks become disturbed and ultimately dysfunctional. We introduce the term protein connectivity-based dysfunction (PCBD) to define this mechanism. Among most sensitive to PCBD are pathways with key roles in synaptic plasticity. We show at cellular and target organ levels that network connectivity and functional imbalances revert to normal levels upon epichaperome inhibition. In conclusion, we provide proof-of-principle to propose AD is a PCBDopathy, a disease of proteome-wide connectivity defects mediated by maladaptive epichaperomes.

2.
Environ Pollut ; 259: 113937, 2020 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-31952101

RESUMO

In recent years, reports of plastic debris in the gastrointestinal (GI) tract of fish have been well documented in the scientific literature. This, in turn, increased concerns regarding human health exposure to microplastics through the consumption of contaminated fish. Most of the available research regarding microplastic toxicity has focused on marine organisms through direct feeding or waterborne exposures at the individual level. However, little is known about the trophic transfer of microplastics through the aquatic food chain. Freshwater zooplankton Daphnia magna (hereafter Daphnia), and the fathead minnow Pimephales promelas (FHM), are well-known model species used in standard toxicological studies and ecological risk assessments that provide a simple model for trophic transfer. The aim of this study was to assess the tissue translocation, trophic transfer, and depuration of two concentrations (20 and 2000-part ml-1) of 6 µm polystyrene (PS) microplastics particles between Daphnia and FHM. Bioconcentration factors (BCF) and bioaccumulation factors (BAF) were determined. Fluorescent microscopy was used to determine the number of particles in the water media and within the organs of both species. Throughout the five days of exposure, PS particles were only found within the GI tract of both species. The BCF for Daphnia was 0.034 ± 0.005 for the low concentration and 0.026 ± 0.006 for the high concentration. The BAF for FHM was 0.094 ± 0.037 for the low concentration and 0.205 ± 0.051 for the high concentration. Between 72 and 96 h after exposure all microplastic particles were depurated from both species. The presence of food had a significant effect on the depuration of microplastic particles from Daphnia but not for FHM. Based on the low BCF and BAF values for both species, rapid depuration rates, and null translocation of microplastic particles to organs and tissues from the GI tract, there is a low probability that microplastics will bioconcentrate and bioaccumulate under environmental conditions.

3.
Clin Neurol Neurosurg ; 188: 105570, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31707290

RESUMO

OBJECTIVE: The Medicaid patient population and health care costs for spine surgeries among these patients have increased since 2010. Hospital length of stay (LOS) contributes appreciably to hospital costs for patients undergoing primary lumbar spine surgery (PLSS). The aim of this study was to identify independent risk factors for increased LOS in patients undergoing PLSS. PATIENTS AND METHODS: In a single-center retrospective study, we reviewed demographic and clinical data from electronic medical records for 181 consecutive adult patients who underwent PLSS involving 1-3 levels from July 2014 to July 2017. We performed regression analyses to identify independent risk factors for increased LOS and to quantify their effects as percent changes in LOS. RESULTS: Among 181 patients who underwent PLSS, the mean LOS was 3.57 days. Based on the Charlson Comorbidity Index (CCI) and American Society of Anesthesiologist (ASA) classification, patients with Medicaid insurance were healthier than non-Medicaid patients (mean CCI: 0.34 versus 0.65; p = 0.041, ASA: 1.71 versus 1.91; p = 0.046) yet Medicaid patients had a longer LOS compared with non-Medicaid patients (mean LOS: 4.03 versus 3.30 days; p = 0.047). There was no significant difference in discharge disposition between Medicaid and non-Medicaid patients (Home = 82.35 % versus 79.65 %; p = 0.855). Medicaid patients also had significantly less spinal levels involved in their surgery (1.44 versus 1.67; p = 0.027). Multivariable regression modeling identified independent risk factors positively associated with increased LOS as age (+1.0 % per year; p = 0.007), Medicaid insurance status (+28.7 %; p = 0.007), and CCI (10.1 % per increment in CCI; p = 0.030). Fusion surgery also was an independent risk factor for increased LOS when compared with laminectomy (-54.1 %; p < 0.001) or discectomy (-51.3 %; p < 0.001). CONCLUSIONS: Increasing age, Medicaid insurance status, higher CCI, and fusion surgery were independently associated with increased LOS after PLSS. This information is useful for preoperative patient counseling, shared decision-making, and risk stratification and may help to further ongoing discussion regarding contributors to rising health care costs. Findings of increased LOS among Medicaid patients will help direct efforts to identify factors that contribute to this health care expense.

4.
J Colloid Interface Sci ; 560: 581-588, 2020 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-31679786

RESUMO

HYPOTHESIS: Self-assembled graphene hydrogels are notable in the field of electrochemical energy storage for their unique combination of excellent specific surface area, high porosity, and electrically conductive continuous network. However, graphene hydrogels suffer from poor mechanical integrity compared to layered architectures like graphene buckypapers, limiting their applications in practical devices. We propose the use of high strength, Kevlar®-derived polymeric nanofillers, aramid nanofibers (ANFs) as structural fillers to enhance graphene hydrogel's shear modulus in the context of multifunctional (mechanical and electrochemical) architectures. EXPERIMENTS: Graphene hydrogels are fabricated using sol-gel self-assembly of graphene oxide (GO) nanosheets in presence of ammonium hydroxide. Colloidal dispersion of ANFs and GO are integrated using a novel combination of solvent exchange and dialysis approach to fabricate GO-ANF hydrogels with 0-15 wt.% of ANFs loading (dry weight basis). Shear modulus and electrochemical properties of resulting hydrogel composites are evaluated using rheology and symmetric supercapacitor cell. FINDINGS: The addition of 2 wt.% ANFs resulted in an 80% improvement in shear modulus compared to neat graphene hydrogel. Addition of ANFs resulted in gradual reduction of specific capacitance, with the specific capacitance of 190 F/g for neat graphene hydrogel, reducing to 128 F/g for an ANF loading of 15 wt.% (dry weight basis). This work shows the broader concept that adding high-strength nanofibers to a nanomaterial gel can add reinforcement provided that the gelation process itself is not disrupted.

5.
Cancer Cell ; 36(5): 559-573.e7, 2019 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-31668946

RESUMO

Alterations in protein-protein interaction networks are at the core of malignant transformation but have yet to be translated into appropriate diagnostic tools. We make use of the kinetic selectivity properties of an imaging probe to visualize and measure the epichaperome, a pathologic protein-protein interaction network. We are able to assay and image epichaperome networks in cancer and their engagement by inhibitor in patients' tumors at single-lesion resolution in real time, and demonstrate that quantitative evaluation at the level of individual tumors can be used to optimize dose and schedule selection. We thus provide preclinical and clinical evidence in the use of this theranostic platform for precision medicine targeting of the aberrant properties of protein networks.

6.
World Neurosurg ; 134: 518-531, 2019 Sep 19.
Artigo em Inglês | MEDLINE | ID: mdl-31542444

RESUMO

Aneurysm clips are indispensable tools in the armamentarium of vascular neurosurgeons. The history of the development of aneurysm clips is witness to ingenuity and tenacity in treating a potentially devastating disease. Few know the stories of their innovators and the inspiration behind their designs. Hence, we present this historical vignette in an attempt to shed more light on the pioneers who shaped the evolution of aneurysm clips as we know them. A comprehensive literature search was performed using PubMed, Google Scholar, Google Books, and library historical archives, as well as personal communications with relatives, colleagues, and institutions of the surgeon-designers. We present the following aneurysm clip innovators and chronicle their biographies and contributions: Herbert Olivecrona (1891-1980), Frank Mayfield (1908-1991), Charles Drake (1920-1998), Joseph McFadden (1920-present), Thoralf Sundt Jr. (1930-1992), William M. Lougheed (1923-2004), William B. Scoville (1906-1984), Milton D. Heifetz (1921-2015), Gazi Yasargil (1925-present), Kenichiro Sugita (1932-1994), and Robert Spetzler (1944-present). Although this compilation of eponymous clips is by no means complete, we hope that it provides an informative historical perspective and an inspiration for aspiring neurosurgeons. The history of aneurysm surgery, an entity once deemed inoperable, teaches us the importance of innovation in medicine.

7.
Pediatr Neurosurg ; 54(2): 75-84, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30844793

RESUMO

BACKGROUND: Occipitocervical distraction injuries (OCDI) in children occur on a wide spectrum of severity, and decisions about treatment suffer from a lack of rigorous guidelines and significant inter-institutional variability. While clear cases of frank atlanto-occipital dislocation (AOD) are treated with surgical stabilization, the approach for less severe cases of OCDI is not standardized. These patients require a careful assessment of both radiographic and clinical criteria, as part of a complex risk-benefit analysis, to establish whether occipitocervical fusion (OCF) is indicated. Here, we performed a systematic review of the literature that describes traumatic OCDI in children < 18 years of age. SUMMARY: We performed a systematic review, according to PRISMA guidelines, of children < 18 years of age presenting with traumatic etiologies of OCDI. We searched PubMed to identify papers congruent with these criteria. Exclusion criteria included (1) reports on atraumatic causes of OCDI and (2) studies with insufficient clinical and radiographic details on individual patients. We identified 16 reports describing a total of 144 patients treated for pediatric traumatic OCDI. Based on the synthesis of these findings and the collective experience of the authors, we present the demographic, clinical, and radiographic factors that underlie OC instability, which we hope will serve as components of a grading system in the future. We considered various clinical and radiographic findings including: (1) the mechanism of injury, (2) the patient's age, (3) CT/CT angiography of head and neck findings and parameters, (4) MRI findings, and (5) neurological exam, for the purpose of determining the severity of the OCDI and offering treatment guidelines based on the summative risk of underlying OC instability. Key Messages: OCDI is a potentially devastating injury, especially in children. Although missing the diagnosis can have potentially catastrophic consequences, reverting to surgical fixation in less severe cases can subject children to unnecessary operative risk and permanently reduce their range of motion. After reviewing all the available reports of pediatric traumatic OCDI in the neurosurgical literature, we propose an outline of clinical and radiographic factors influencing underlying OC instability that could be incorporated into a grading scale to guide treatment. We hope this study stimulates discussion on the standardization of treatment for pediatric OCDI.


Assuntos
Vértebras Cervicais/lesões , Vértebras Cervicais/cirurgia , Luxações Articulares/cirurgia , Osso Occipital/lesões , Osso Occipital/cirurgia , Vértebras Cervicais/diagnóstico por imagem , Criança , Humanos , Luxações Articulares/diagnóstico por imagem , Osso Occipital/diagnóstico por imagem
8.
BMC Plant Biol ; 18(1): 380, 2018 Dec 29.
Artigo em Inglês | MEDLINE | ID: mdl-30594150

RESUMO

BACKGROUND: Increasing the productivity of rapeseed as one of the widely cultivated oil crops in the world is of upmost importance. As flowering time and plant architecture play a key role in the regulation of rapeseed yield, understanding the genetic mechanism underlying these traits can boost the rapeseed breeding. Meristem identity genes are known to have pleiotropic effects on plant architecture and seed yield in various crops. To understand the function of one of the meristem identity genes, APETALA1 (AP1) in rapeseed, we performed phenotypic analysis of TILLING mutants under greenhouse conditions. Three stop codon mutant families carrying a mutation in Bna.AP1.A02 paralog were analyzed for different plant architecture and seed yield-related traits. RESULTS: It was evident that stop codon mutation in the K domain of Bna.AP1.A02 paralog caused significant changes in flower morphology as well as plant architecture related traits like plant height, branch height, and branch number. Furthermore, yield-related traits like seed yield per plant and number of seeds per plants were also significantly altered in the same mutant family. Apart from phenotypic changes, stop codon mutation in K domain of Bna.AP1.A02 paralog also altered the expression of putative downstream target genes like Bna.TFL1 and Bna.FUL in shoot apical meristem (SAM) of rapeseed. Mutant plants carrying stop codon mutations in the COOH domain of Bna.AP1.A02 paralog did not have a significant effect on plant architecture, yield-related traits or the expression of the downstream targets. CONCLUSIONS: We found that Bna.AP1.A02 paralog has pleiotropic effect on plant architecture and yield-related traits in rapeseed. The allele we found in the current study with a beneficial effect on seed yield can be incorporated into rapeseed breeding pool to develop new varieties.


Assuntos
Brassica napus/genética , Genes de Plantas/genética , Proteínas de Domínio MADS/genética , Proteínas de Plantas/genética , Sementes/crescimento & desenvolvimento , Brassica napus/crescimento & desenvolvimento , Brassica napus/fisiologia , Códon/genética , Flores/crescimento & desenvolvimento , Regulação da Expressão Gênica de Plantas/genética , Genes de Plantas/fisiologia , Proteínas de Domínio MADS/fisiologia , Proteínas de Plantas/fisiologia , Característica Quantitativa Herdável , Reação em Cadeia da Polimerase em Tempo Real , Sementes/genética , Alinhamento de Sequência , Homologia de Sequência , Transcriptoma
9.
J Neurosurg Pediatr ; 23(3): 333-342, 2018 12 07.
Artigo em Inglês | MEDLINE | ID: mdl-30544335

RESUMO

OBJECTIVE In this clinical trial report, the authors analyze safety and infusion distribution of IL13-Pseudomonas exotoxin, an antitumor chimeric molecule, administered via intratumoral convection enhanced delivery (CED) in pediatric patients with diffuse intrinsic pontine glioma (DIPG). METHODS This was a Phase I single-institution, open-label, dose-escalation, safety and tolerability study of IL13-PE38QQR infused via single-catheter CED into 5 pediatric DIPG patients. IL13-PE38QQR was administered to regions of tumor selected by radiographic findings. Two escalating dose levels were evaluated: 0.125 µg/mL in cohort 1 and 0.25 µg/mL in cohort 2. Real-time MRI was performed during intratumoral infusions, and MRI and MR spectroscopy were performed before and after the infusions. Clinical evaluations, including parent-reported quality of life (QOL), were assessed at baseline and 4 weeks post-infusion. RESULTS Direct infusion of brainstem tumor with IL13-PE using the CED technique in patients with DIPG produced temporary arrest of disease progression in 2 of 5 patients, both of whom subsequently received a second infusion. All 5 patients showed signs of disease progression by 12 weeks after initial infusion. Two patients experienced transient cranial nerve deficits and lethargy after infusion, and these deficits resolved with corticosteroid treatment in both cases. No patient had radiographic evidence of acute or long-term treatment toxicity. Parent-reported QOL was consistent with medical outcomes. CONCLUSIONS Even though IL13-PE delivered by CED did not reach the entire MRI-defined tumor volume in any patient, short-term radiographic antitumor effects were observed in 2 of the 5 patients treated. The patients' performance status did not improve. Drug delivery using multiple catheters may produce improved outcomes. Clinical trial registration no.: NCT00088061 (clinicaltrials.gov) ABBREVIATIONS CED = convection-enhanced delivery; DIPG = diffuse intrinsic pontine glioma; IL-13 = interleukin 13; IL13R = IL-13 receptor; IPI = Impact of Pediatric Illness; KPS = Karnofsky Performance Status; LPS = Lansky Performance Status; MRS = MR spectroscopy; NAA = n-acetyl aspartate; QOL = quality of life; Vd = volume of distribution; Vi = volume of infusion.


Assuntos
Neoplasias do Tronco Encefálico/terapia , Exotoxinas/administração & dosagem , Exotoxinas/efeitos adversos , Glioma/terapia , Interleucina-13/administração & dosagem , Interleucina-13/efeitos adversos , Proteínas Recombinantes de Fusão/administração & dosagem , Proteínas Recombinantes de Fusão/efeitos adversos , Neoplasias do Tronco Encefálico/diagnóstico por imagem , Criança , Progressão da Doença , Glioma/diagnóstico por imagem , Humanos , Infusões Intralesionais/métodos , Imagem por Ressonância Magnética Intervencionista/métodos , Espectroscopia de Ressonância Magnética , Pseudomonas , Qualidade de Vida , Retratamento , Fatores de Tempo
10.
Nat Commun ; 9(1): 4345, 2018 10 19.
Artigo em Inglês | MEDLINE | ID: mdl-30341316

RESUMO

Environmental and genetic risk factors contribute to Parkinson's Disease (PD) pathogenesis and the associated midbrain dopamine (mDA) neuron loss. Here, we identify early PD pathogenic events by developing methodology that utilizes recent innovations in human pluripotent stem cells (hPSC) and chemical sensors of HSP90-incorporating chaperome networks. We show that events triggered by PD-related genetic or toxic stimuli alter the neuronal proteome, thereby altering the stress-specific chaperome networks, which produce changes detected by chemical sensors. Through this method we identify STAT3 and NF-κB signaling activation as examples of genetic stress, and phospho-tyrosine hydroxylase (TH) activation as an example of toxic stress-induced pathways in PD neurons. Importantly, pharmacological inhibition of the stress chaperome network reversed abnormal phospho-STAT3 signaling and phospho-TH-related dopamine levels and rescued PD neuron viability. The use of chemical sensors of chaperome networks on hPSC-derived lineages may present a general strategy to identify molecular events associated with neurodegenerative diseases.


Assuntos
Neurônios Dopaminérgicos/metabolismo , Proteínas de Choque Térmico HSP90/metabolismo , Mesencéfalo/metabolismo , Técnicas Biossensoriais , Proteínas de Choque Térmico HSP90/fisiologia , Mesencéfalo/patologia , NF-kappa B/metabolismo , Fator de Transcrição STAT3/metabolismo , Estresse Fisiológico
11.
Sci Rep ; 8(1): 14525, 2018 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-30266957

RESUMO

Electrochemical exfoliation is a promising bulk method for producing graphene from graphite; in this method, an applied voltage drives ionic species to intercalate into graphite where they form gaseous species that expand and exfoliate individual graphene sheets. However, a number of obstacles have prevented this approach from becoming a feasible production route; the disintegration of the graphite electrode as the method progresses is the chief difficulty. Here we show that if graphite powders are contained and compressed within a permeable and expandable containment system, the graphite powders can be continuously intercalated, expanded, and exfoliated to produce graphene. Our data indicate both high yield (65%) and extraordinarily large lateral size (>30 µm) in the as-produced graphene. We also show that this process is scalable and that graphene yield efficiency depends solely on reactor geometry, graphite compression, and electrolyte transport.

12.
World Neurosurg ; 119: e922-e927, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30099188

RESUMO

BACKGROUND: Decompressive hemicraniectomy to control medically refractory intracranial hypertension and cerebral edema and evacuate mass lesions in traumatic brain injury is a widely accepted treatment paradigm. However, the critical specifications of the bone flap size necessary to control the intracranial pressure (ICP) and provide improved patient outcomes is unknown. We assessed the effect of craniectomy size on the outcomes in surgical decompression for traumatic brain injury. METHODS: From 2003 to 2011, 58 cases of decompressive hemicraniectomy were performed for evacuation of hematoma and treatment of refractory ICP in adult patients with traumatic brain injury. The surface area of the decompressive bone flaps was calculated from the postoperative computed tomography scans and correlated with the ICP and Glasgow Coma Scale scores immediately postoperatively and during long-term follow-up. RESULTS: Decompressive craniectomy led to a statistically significant continued reduction in the preoperative ICP values (24.5 mm Hg; range, 5-30 mm Hg) compared with the postoperative ICP (16.7 mm Hg; range, 1-30; P = 0.006). However, no significant improvement in the preoperative Glasgow Coma Scale (7.47 mm Hg; range, 3-15; vs. 7.50 mm Hg; range, 3-15; P = 0.96) was observed with hemicraniectomy. CONCLUSION: For surface areas of 7000-16,000 mm2, size was an independent factor in ICP reduction but not for the overall neurologic outcome.


Assuntos
Lesões Encefálicas Traumáticas/cirurgia , Craniectomia Descompressiva/métodos , Retalhos Cirúrgicos , Adolescente , Adulto , Idoso , Transplante Ósseo/métodos , Feminino , Escala de Coma de Glasgow , Humanos , Hipertensão Intracraniana/cirurgia , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Resultado do Tratamento , Adulto Jovem
13.
Langmuir ; 34(29): 8550-8559, 2018 07 24.
Artigo em Inglês | MEDLINE | ID: mdl-29950094

RESUMO

Graphene oxide (GO)-based gels are attractive because of their ability to retain individual nanosheet properties in a three-dimensional (3D) bulk material. The final morphology and properties of these 3D gel networks depend strongly on the type and density of cross-links, and these gels can be dried and annealed to form aerogels with both high conductivity (560 S/m) and high surface area (1700 m2/g). The results show that both ammonia content and the parent nanosheet morphology (crumpled vs flat) have a strong influence on the cross-linked structure and composition; notably, nitrogen is found in the gels, suggesting that ammonia actively participates in the reaction rather than as a mere catalyst. The GO nanosheet morphology may be altered using spray-drying to obtain crumpled GO (cGO) nanosheets and form cGO gels; this allows for an additional handle in the creation of GO-based gels with tunable density, electrical conductivity, and surface area.

14.
Plant Cell Environ ; 41(8): 1935-1947, 2018 08.
Artigo em Inglês | MEDLINE | ID: mdl-29813173

RESUMO

Rapeseed (Brassica napus L.), one of the most important sources of vegetable oil and protein-rich meals worldwide, is adapted to different geographical regions by modification of flowering time. Rapeseed cultivars have different day length and vernalization requirements, which categorize them into winter, spring, and semiwinter ecotypes. To gain a deeper insight into genetic factors controlling floral transition in B. napus, we performed RNA sequencing (RNA-seq) in the semiwinter doubled haploid line, Ningyou7, at different developmental stages and temperature regimes. The expression profiles of more than 54,000 gene models were compared between different treatments and developmental stages, and the differentially expressed genes were considered as targets for association analysis and genetic mapping to confirm their role in floral transition. Consequently, 36 genes with association to flowering time, seed yield, or both were identified. We found novel indications for neofunctionalization in homologs of known flowering time regulators like VIN3 and FUL. Our study proved the potential of RNA-seq along with association analysis and genetic mapping to identify candidate genes for floral transition in rapeseed. The candidate genes identified in this study could be subjected to genetic modification or targeted mutagenesis and genotype building to breed rapeseed adapted to certain environments.


Assuntos
Brassica napus/genética , Flores/crescimento & desenvolvimento , Genes de Plantas/genética , Brassica napus/crescimento & desenvolvimento , Brassica napus/fisiologia , Mapeamento Cromossômico , Flores/genética , Flores/fisiologia , Perfilação da Expressão Gênica , Regulação da Expressão Gênica de Plantas/genética , Genes de Plantas/fisiologia , Estações do Ano , Análise de Sequência de RNA , Transcriptoma
15.
Sci Adv ; 4(3): eaaq0118, 2018 03.
Artigo em Inglês | MEDLINE | ID: mdl-29536044

RESUMO

Stretchable, bendable, and foldable conductive coatings are crucial for wearable electronics and biometric sensors. These coatings should maintain functionality while simultaneously interfacing with different types of surfaces undergoing mechanical deformation. MXene sheets as conductive two-dimensional nanomaterials are promising for this purpose, but it is still extremely difficult to form surface-agnostic MXene coatings that can withstand extreme mechanical deformation. We report on conductive and conformal MXene multilayer coatings that can undergo large-scale mechanical deformation while maintaining a conductivity as high as 2000 S/m. MXene multilayers are successfully deposited onto flexible polymer sheets, stretchable poly(dimethylsiloxane), nylon fiber, glass, and silicon. The coating shows a recoverable resistance response to bending (up to 2.5-mm bending radius) and stretching (up to 40% tensile strain), which was leveraged for detecting human motion and topographical scanning. We anticipate that this discovery will allow for the implementation of MXene-based coatings onto mechanically deformable objects.

16.
Environ Sci Technol ; 52(2): 794-800, 2018 01 16.
Artigo em Inglês | MEDLINE | ID: mdl-29261302

RESUMO

The increase in use of nanomaterials such as multiwalled carbon nanotubes (MWCNTs) presents a need to study their interactions with the environment. Trophic transfer was measured between Daphnia magna and Pimephales promelas (fathead minnow, FHM) exposed to MWCNTs with different outer diameter (OD) sizes (MWCNT1 = 8-15 nm OD and MWCNT2 = 20-30 nm OD) in the presence and absence of copper. Pristine FHM were fed D. magna, previously exposed for 3 d to MWCNT1 or MWCNT2 (0.1 mg/L) and copper (0.01 mg/L), for 7 d. D. magna bioaccumulated less MWCNT1 (0.02 µg/g) than MWCNT2 (0.06 µg/g), whereas FHM accumulated more MWCNT1 (0.81 µg/g) than MWCNT2 (0.04 µg/g). In the presence of copper, MWCNT bioaccumulation showed an opposite trend. Mostly MWCNT1 (0.03 µg/g) bioaccumulated in D. magna, however less MWCNT1 (0.21 µg/g) than MWCNT2 (0.32 µg/g) bioaccumulated in FHM. Bioaccumulation factors were higher for MWCNT1s than MWCNT2. However, an opposite trend was observed when copper was added. Plasma metallothionein-2 was measured among treatments; however concentrations were not statistically different from the control. This study demonstrates that trophic transfer of MWCNTs is possible in the aquatic environment and further exploration with mixtures can strengthen the understanding of MWCNT environmental behavior.


Assuntos
Cyprinidae , Nanotubos de Carbono , Poluentes Químicos da Água , Animais , Cobre , Daphnia , Íons
17.
ACS Appl Mater Interfaces ; 9(36): 30797-30804, 2017 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-28816428

RESUMO

We investigate the π-π stacking of polyaromatic hydrocarbons (PAHs) with graphene surfaces, showing that such interactions are general across a wide range of PAH sizes and species, including graphene quantum dots. We synthesized a series of graphene quantum dots with sulfonyl, amino, and carboxylic functional groups and employed them to exfoliate and disperse pristine graphene in water. We observed that sulfonyl-functionalized graphene quantum dots were able to stabilize the highest concentration of graphene in comparison to other functional groups; this is consistent with prior findings by pyrene. The graphene nanosheets prepared showed excellent colloidal stability, indicating great potential for applications in electronics, solar cells, and photonic displays which was demonstrated in this work.

18.
Environ Toxicol Chem ; 36(8): 2199-2204, 2017 08.
Artigo em Inglês | MEDLINE | ID: mdl-28160491

RESUMO

The use of carbon-based nanomaterials (CNMs) such as multiwalled carbon nanotubes (MWCNTs), graphene, and graphene oxide (GO) is increasing across many applications because of their unique and versatile properties. These CNMs may enter the aquatic environment through many pathways, creating the potential for organism exposure. The present study addresses the bioaccumulation and toxicity seen in Daphnia magna exposed to CNMs dispersed in sodium dodecyl benzene sulfonate (SDBS). In study I, D. magna were exposed to varying outer diameters of MWCNTs for 24 h in moderately hard or hard freshwater. Bioaccumulation of MWCNT was found in all treatments, with the highest concentrations (0.53 ± 0.27 µg/g) in D. magna exposed in hard freshwater (p < 0.005). The median lethal concentration (LC50) was determined for D. magna exposed to CNMs in moderately hard and hard freshwater. In study II, D. magna were exposed to CNMs for 72 h in moderately hard freshwater to assess swimming velocity and generation of reactive oxygen species (ROS) detected by dichlorofluorescein fluorescence. An overall decrease was seen in D. magna swimming velocity after exposure to CNMs. The generation of ROS was significantly higher (1.54 ± 0.38 dichlorofluorescein mM/mg dry wt) in D. magna exposed to MWCNTs of smaller outer diameters than in controls after 72 h (p < 0.05). These results suggest that further investigation of CNM toxicity and behavior in the aquatic environment is needed. Environ Toxicol Chem 2017;36:2199-2204. © 2017 SETAC.


Assuntos
Daphnia/efeitos dos fármacos , Grafite/toxicidade , Nanotubos de Carbono/toxicidade , Poluentes Químicos da Água/toxicidade , Animais , Benzenossulfonatos/toxicidade , Daphnia/metabolismo , Monitoramento Ambiental , Água Doce/química , Grafite/metabolismo , Dose Letal Mediana , Óxidos , Espécies Reativas de Oxigênio/metabolismo , Natação , Poluentes Químicos da Água/metabolismo
19.
Nanotechnology ; 27(50): 505601, 2016 Dec 16.
Artigo em Inglês | MEDLINE | ID: mdl-27855123

RESUMO

Scalable production of graphene through liquid-phase exfoliation has been plagued by low yields. Although several recent studies have attempted to improve graphene exfoliation technology, the problem of separating colloidal nanosheets from unexfoliated parent material has received far less attention. Here we demonstrate a scalable method for improving nanosheet yield through a facile washing process. By probing the sedimentation of liquid-phase exfoliated slurries of graphene nanosheets and parent material, we found that a portion of exfoliated graphene is entrapped in the sediment, but can be recovered by repeatedly washing the slurry of nanosheet and parent material with additional solvent. We found this process to significantly increase the overall yield of graphene (graphene/parent material) and recover a roughly constant proportion of graphene with each wash. The cumulative amount of graphene recovered is only a function of total solvent volume. Moreover, we found this technique to be applicable to other types of nanosheets such as boron nitride nanosheets.

20.
Adv Mater ; 28(40): 8796-8818, 2016 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-27546380

RESUMO

Recent developments in the exfoliation, dispersion, and processing of pristine graphene (i.e., non-oxidized graphene) are described. General metrics are outlined that can be used to assess the quality and processability of various "graphene" products, as well as metrics that determine the potential for industrial scale-up. The pristine graphene production process is categorized from a chemical engineering point of view with three key steps: i) pretreatment, ii) exfoliation, and iii) separation. How pristine graphene colloidal stability is distinct from the exfoliation step and is dependent upon graphene interactions with solvents and dispersants are extensively reviewed. Finally, the challenges and opportunities of using pristine graphene as nanofillers in polymer composites, as well as as building blocks for macrostructure assemblies are summarized in the context of large-scale production.

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