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1.
Clin Transl Gastroenterol ; 13(10): e00526, 2022 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-36007177

RESUMO

INTRODUCTION: Continuous left ventricular assist devices (LVADs) offer hemodynamic support in advanced and decompensated heart failure but are often complicated by gastrointestinal bleeding (GIB) in medically fragile patients. METHODS: We performed a retrospective analysis of 475 consecutive patients who underwent LVAD implantation at the Massachusetts General Hospital and Tufts Medical Center from 2008 to 2019 and identified 128 patients with clinically significant GIB. Clinical characteristics of each bleeding event, including procedures and interventions, were recorded. We examined LVAD patients with overt and occult presentations to determine diagnostic endoscopic yield and analyzed predictors of recurrent GIB. RESULTS: We identified 128 unique patients with LVAD implantation complicated by GIB. No significant difference was observed based on study center, underlying cardiomyopathy, race/ethnicity, serum indices, and medications used. Overt bleeders presented more commonly during LVAD implantation admission ( P = 0.001) than occult bleeders. Occult bleed presentations had only 1 lower and no middle GI bleed source identified, despite similar workups to overt bleeds. Destination therapy (e.g., among nontransplant candidates) LVAD implantation (odds ratio 2.38, 95% confidence interval 1.05-5.58) and a history of GIB (odds ratio 3.85, 95% confidence interval 1.29-12.7) were independently associated with an increased risk of recurrent GIB-related hospitalization. DISCUSSION: Our findings confirm a high rate of GIB, especially in destination LVAD patients, and show a low diagnostic yield for colonoscopy and middle GI bleed assessments in LVAD patients with occult bleeds. Overt bleeding was more common and associated with vascular malformations. Although endoscopic interventions stopped active hemorrhage, GIB often recurred.


Assuntos
Insuficiência Cardíaca , Coração Auxiliar , Humanos , Coração Auxiliar/efeitos adversos , Estudos Retrospectivos , Hemorragia Gastrointestinal/diagnóstico , Hemorragia Gastrointestinal/etiologia , Hemorragia Gastrointestinal/terapia , Insuficiência Cardíaca/terapia , Insuficiência Cardíaca/complicações , Hemodinâmica
2.
ACG Case Rep J ; 8(11): e00689, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34849377

RESUMO

Waldenstrom macroglobulinemia is an uncommon mature B-cell lymphoma characterized by monoclonal immunoglobulin M protein in peripheral blood and lymphoplasmacytic cells in bone marrow and/or extramedullary sites. The gastrointestinal tract is a rare site of involvement. The diagnosis is based on clinicopathologic findings, although somatic mutations, such as MYD88, can aid in the diagnosis. We present a patient with irregular stools diagnosed with Waldenstrom macroglobulinemia involving the rectosigmoid colon by histopathology and immunohistochemistry on colonic biopsies, immunoglobulin M protein in serum, clonal plasma cells in bone marrow, and MYD88 mutation in colonic and bone marrow specimens.

4.
Cureus ; 12(5): e7928, 2020 May 02.
Artigo em Inglês | MEDLINE | ID: mdl-32499973

RESUMO

Colonic Dieulafoy's lesions are an exceptionally rare cause of lower gastrointestinal (GI) bleeding. These lesions are almost exclusively found in the upper GI tract based on previous reviews. We present a case of an 81-year-old man who presented with melena progressing to hematochezia and was found to have a cecal Dieulafoy's lesion on colonoscopy. Hemostasis with clipping was achieved and allowed for the resumption of anticoagulation. This case demonstrates the importance of considering this diagnosis in lower GI bleeding when evidence of more common causes may not be present, especially considering these lesions amenability to endoscopic therapy.

5.
J Theor Biol ; 500: 110309, 2020 09 07.
Artigo em Inglês | MEDLINE | ID: mdl-32387284

RESUMO

It is well known that tornadoes passing over fields can cause significant damage to crops, and tornado tracks of fallen, or lodged, crops can extend for many hundreds of metres. An examination of photographic evidence of such events suggests that, at least for low speed EF0/EF1 events, lodging occurs beneath tornadoes primarily due to a strong radial flow (rather than circumferential flow) at the canopy surface. In order to investigate this effect further, a simple model of a tornado has been developed which, whilst fully satisfying the three dimensional Euler equations, models a circumferential flow at the edge of the tornado boundary layer near the ground, which becomes a radial flow as the ground is approached. This model is then used in a generalised model of lodging to predict lodging track widths and crop fall directions. It is shown that, when expressed in a suitably normalised form, both lodging width and crop fall direction are functions of a normalised translational velocity and a normalised crop lodging velocity. The lodging patterns are of two forms - a forward convergence (FC) where the cropfall converges on the tornado track in a forward direction, and a backward convergence (BC) where the convergence is in the opposite direction to tornado translations. Regions of FC and BC in the normalised parameter plane are calculated. These patterns are very similar to those observed in the field, which gives some confidence in the nature of the model. The model is then used to investigate the sensitivity of lodging width to crop and tornado parameters, and also to carry out a risk analysis to determine the probability distributions of lodging width for specified distributions of crop and tornado parameters.


Assuntos
Tornados , Produtos Agrícolas , Probabilidade , Medição de Risco
6.
Cureus ; 12(1): e6594, 2020 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-32064176

RESUMO

Dubin-Johnson syndrome is a rare, benign disorder that results in conjugated hyperbilirubinemia. The disease manifests as intermittent jaundice without long-term hepatic or other clinical complications. This article reports a case of Dubin-Johnson syndrome, which was identified during cardiac transplant evaluation for cardiomyopathy secondary to a polyglycogen storage disease. The patient successfully underwent an orthotopic heart transplant. Postoperatively, her conjugated hyperbilirubinemia increased as compared to her baseline but resolved after several weeks. This report briefly reviews the hepatic manifestations in patients with Dubin-Johnson syndrome undergoing major surgery and highlights urinary coproporphyrin as a useful diagnostic test for Dubin-Johnson syndrome.

7.
Dig Dis Sci ; 65(11): 3316-3323, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-31916085

RESUMO

AIM: In previous studies, the 5-year progression rate of gastric intestinal metaplasia to gastric adenocarcinoma has varied substantially. We investigated the incidence rate of dysplasia and gastric adenocarcinoma and the rate of progression among a cohort of patients with non-dysplastic gastric intestinal metaplasia. METHODS: This is a single-center, single-cohort retrospective study. Patients who had undergone an EGD with biopsies from 01/01/1993 to 12/31/2013 were included. The primary outcome of interest was the composite of low-grade dysplasia, high-grade dysplasia, or adenocarcinoma. Time to progression and risk factor subgroup analyses were performed. RESULTS: A total of 1628 subjects were screened, of whom 358 met the inclusion criteria. A total of 21 first-time events were recorded. The annual incidence rate of low-grade dysplasia was 2.1 (95% CI 1.3-3.5) cases per 1000 person-years, 0.5 (95% 0.2-1.3) per 1000 person-years for high-grade dysplasia, and 0.8 (95% CI 0.3-1.6) cases per 1000 person-years for gastric adenocarcinoma. The historical control group had an annual adenocarcinoma incidence rate of 0.07 per 1000 person-years. The event rate in Asians was also noted to be significantly higher between years 0-8 as compared with patients of non-Asian race, and extensive intestinal metaplasia was an independent risk factor (HR = 4.06 (95% CI 1.45-11.34), p = 0.007). CONCLUSIONS: Patients with non-dysplastic gastric intestinal metaplasia may progress to dysplasia and gastric adenocarcinoma. The incidence rate of gastric adenocarcinoma is higher than that of the historical control population (0.07 per 1000 person-years). The presence of extensive intestinal metaplasia was a risk factor for progression of disease. Triennial EGD may be warranted in patients with non-dysplastic gastric intestinal metaplasia.


Assuntos
Adenocarcinoma/patologia , Lesões Pré-Cancerosas/patologia , Neoplasias Gástricas/patologia , Adenocarcinoma/epidemiologia , Biópsia , Estudos de Casos e Controles , Progressão da Doença , Feminino , Humanos , Incidência , Masculino , Massachusetts/epidemiologia , Metaplasia , Pessoa de Meia-Idade , Gradação de Tumores , Lesões Pré-Cancerosas/epidemiologia , Estudos Retrospectivos , Fatores de Risco , Neoplasias Gástricas/epidemiologia
8.
JOP ; 20(5): 121-124, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32104166

RESUMO

BACKGROUND: Carcinoma of unknown primary represents a therapeutic challenge in oncological practice. Evidence lacks to support particular chemotherapy selection and empirical therapies are commonly extrapolated from data on patients where primary tumor site is known. Gemcitabine, Oxaliplatin, Leucovorin and 5-Fluorouracil was previously developed to treat pancreatic cancer. These agents have also demonstrated activities in other gastrointestinal malignancies. Considering promising anti-tumor effects of GOLF, we performed a retrospective study to investigate anti-tumor activity and safety of a simplified Gemcitabine, Oxaliplatin, Leucovorin and 5-Fluorouracil in patients with Carcinoma of unknown primary in whom immunohistostaining was suggestive of either upper gastrointestinal cancers or pancreatobiliary cancers. METHODS: This retrospective study included 18 patients recorded to have a diagnosis of Carcinoma of unknown primary between Aug 2010-Dec 2015, who received biweekly G 1000 mg/m2, O 85 mg/m2, L 200 mg/m2 and F 2400 mg/m2 over 46-h on day 1 with pegfilgrastim on day 3 every 14 days. IHC staining pattern favored upper GI origin, including stomach, bile duct or pancreas. Tumor assessments were repeated every 8 weeks. RESULTS: Median age was 67 years (range: 46-76), with ECOG PS<2, and 50% were women. Median number of cycles was 4 (range: 3-14). 7 partial responses were obtained (RR: 39%) and 7 achieved stable disease with overall disease control of 78%. Median time to tumor progression was 4 months (range: 2-9). 8 (44%) patients received liver-directed therapy and 1 underwent HIPEC (5%). Median survival time was 10.5 months (range: 6.7-14.5) and 1-year overall survival rate was 35%. Grade 3-4 toxicities included neutropenia, febrile neutropenia, thrombocytopenia, nausea, diarrhea, mucositis and oxaliplatin-induced neuropathy. CONCLUSION: Simplified Gemcitabine, Oxaliplatin, Leucovorin and 5-Fluorouracil regimen appears to be feasible with promising activity for Carcinoma of unknown primary and deserves to be evaluated in future trials.

9.
Anticancer Drugs ; 29(7): 597-612, 2018 08.
Artigo em Inglês | MEDLINE | ID: mdl-29782352

RESUMO

Pancreatic neuroendocrine tumors (PNETs) are a rare and heterogeneous group of neoplasia and differ in their clinical presentation, behavior, and prognosis based on both histological features and cancer stage at the time of diagnosis. Although small-sized tumors can be surgically resected, locally advanced and metastatic tumors confer a poor prognosis. In addition, only limited treatment options are available to the latter group of patients with PNETs, such as hormonal analogs, cytotoxic agents, and targeted therapy. In selected patients, liver-directed therapies are also used. As expected, clinicians taking care of these patients are challenged to develop an effective and comprehensive treatment strategy for their patients amid a wide variety of treatment modalities. Targeted therapy for PNETs is limited to sunitinib and everolimus. Presently, a number of clinical studies are ongoing to assess the efficacy of newer targeted agents alone and in combination with previous agents for the treatment of advanced PNETs. The authors reviewed the current treatment and also discussed the emerging agents and emphasized the need to identify biomarkers.


Assuntos
Antineoplásicos/uso terapêutico , Biomarcadores Tumorais , Neovascularização Patológica/prevenção & controle , Tumores Neuroendócrinos/tratamento farmacológico , Neoplasias Pancreáticas/tratamento farmacológico , Antineoplásicos/administração & dosagem , Biomarcadores Tumorais/genética , Biomarcadores Tumorais/metabolismo , Everolimo/administração & dosagem , Everolimo/uso terapêutico , Humanos , Terapia de Alvo Molecular , Estadiamento de Neoplasias , Tumores Neuroendócrinos/irrigação sanguínea , Tumores Neuroendócrinos/diagnóstico por imagem , Neoplasias Pancreáticas/irrigação sanguínea , Neoplasias Pancreáticas/diagnóstico por imagem , Prognóstico , Sunitinibe/administração & dosagem , Sunitinibe/uso terapêutico
10.
Cureus ; 10(2): e2242, 2018 Feb 27.
Artigo em Inglês | MEDLINE | ID: mdl-29719744

RESUMO

This report describes a case of primary hepatic diffuse large B-cell lymphoma (DLBCL) in a 64-year-old male who presented with constitutional symptoms, jaundice, abdominal swelling, and right upper quadrant pain. The diagnosis was confirmed on percutaneous liver biopsy. Notably, there was no evidence of extra-hepatic involvement. The patient received methylprednisolone and cyclophosphamide with good response but was lost to follow-up upon being transferred. This case highlights the importance of considering primary hepatic DLBCL in patients with unexplained abnormal liver tests and atypical imaging without solitary or discrete lesions, as this rare malignancy can present furtively.

11.
J Med Internet Res ; 17(10): e234, 2015 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-26475634

RESUMO

BACKGROUND: Symptom monitoring is a cornerstone of asthma self-management. Conventional methods of symptom monitoring have fallen short in producing objective data and eliciting patients' consistent adherence, particularly in teen patients. We have recently developed an Automated Device for Asthma Monitoring (ADAM) using a consumer mobile device as a platform to facilitate continuous and objective symptom monitoring in adolescents in vivo. OBJECTIVE: The objectives of the study were to evaluate the validity of the device using spirometer data, fractional exhaled nitric oxide (FeNO), existing measures of asthma symptoms/control and health care utilization data, and to examine the sensitivity and specificity of the device in discriminating asthma cases from nonasthma cases. METHODS: A total of 84 teens (42 teens with a current asthma diagnosis; 42 without asthma) aged between 13 and 17 years participated in the study. All participants used ADAM for 7 consecutive days during which participants with asthma completed an asthma diary two times a day. ADAM recorded the frequency of coughing for 24 hours throughout the 7-day trial. Pearson correlation and multiple regression were used to examine the relationships between ADAM data and asthma control, quality of life, and health care utilization at the time of the 7-day trial and 3 months later. A receiver operating characteristic (ROC) curve analysis was conducted to examine sensitivity and specificity based on the area under the curve (AUC) as an indicator of the device's capacity to discriminate between asthma versus nonasthma cases. RESULTS: ADAM data (cough counts) were negatively associated with forced expiratory volume in first second of expiration (FEV1) (r=-.26, P=.05), forced vital capacity (FVC) (r=-.31, P=.02), and overall asthma control (r=-.41, P=.009) and positively associated with daily activity limitation (r=.46, P=.01), nighttime (r=.40, P=.02) and daytime symptoms (r=.38, P=.02), and health care utilization (r=.61, P<.001). Device data were also a significant predictor of asthma control (ß=-.48, P=.003), quality of life (ß=-.55, P=.001), and health care utilization (ß=.74, P=.004) after 3 months. The ROC curve analysis for the presence of asthma diagnosis had an AUC of 0.71 (95% CI 0.58-0.84), which was significantly different from chance (χ(2) 1=9.7, P=.002), indicating the device's discriminating capacity. The optimal cutoff value of the device was 0.56 with a sensitivity of 51.3% and a specificity of 72.7%. CONCLUSIONS: This study demonstrates validity of ADAM as a symptom-monitoring device in teens with asthma. ADAM data reflect the current status of asthma control and predict asthma morbidity and quality of life for the near future. A monitoring device such as ADAM can increase patients' awareness of the patterns of cough for early detection of worsening asthma and has the potential for preventing serious and costly future consequences of asthma.


Assuntos
Asma/diagnóstico , Testes Respiratórios/instrumentação , Tosse/terapia , Monitorização Ambulatorial/instrumentação , Adolescente , Testes Respiratórios/métodos , Feminino , Volume Expiratório Forçado , Humanos , Masculino , Monitorização Ambulatorial/métodos , Qualidade de Vida , Reprodutibilidade dos Testes
12.
Comput Math Methods Med ; 2015: 527815, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26120354

RESUMO

We propose a new algorithm to predict the outcome of direct-current electric (DCE) cardioversion for atrial fibrillation (AF) patients. AF is the most common cardiac arrhythmia and DCE cardioversion is a noninvasive treatment to end AF and return the patient to sinus rhythm (SR). Unfortunately, there is a high risk of AF recurrence in persistent AF patients; hence clinically it is important to predict the DCE outcome in order to avoid the procedure's side effects. This study develops a feature extraction and classification framework to predict AF recurrence patients from the underlying structure of atrial activity (AA). A multiresolution signal decomposition technique, based on matching pursuit (MP), was used to project the AA over a dictionary of wavelets. Seven novel features were derived from the decompositions and were employed in a quadratic discrimination analysis classification to predict the success of post-DCE cardioversion in 40 patients with persistent AF. The proposed algorithm achieved 100% sensitivity and 95% specificity, indicating that the proposed computational approach captures detailed structural information about the underlying AA and could provide reliable information for effective management of AF.


Assuntos
Fibrilação Atrial/diagnóstico , Sistemas de Apoio a Decisões Clínicas , Eletrocardiografia , Idoso , Algoritmos , Fibrilação Atrial/patologia , Bases de Dados Factuais , Cardioversão Elétrica , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Modelos Estatísticos , Recidiva , Reprodutibilidade dos Testes , Risco , Sensibilidade e Especificidade , Processamento de Sinais Assistido por Computador , Software
14.
Case Rep Gastrointest Med ; 2015: 924532, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-25705529

RESUMO

Background. Autoimmune pancreatitis (AIP) is an atypical chronic inflammatory pancreatic disease that appears to involve autoimmune mechanisms. In recent years, AIP has presented as a new clinical entity with its protean pancreaticobiliary and systemic presentations. Its unique pathology and overlap of clinical and radiological features and absence of serological markers foster the disease's unique position. We report a case of diffuse type 1 autoimmune pancreatitis with obstructive jaundice managed with biliary sphincterotomy, stent placement, and corticosteroids. A 50-year-old Caucasian woman presented to our hospital with epigastric pain, nausea, vomiting, and jaundice. Workup showed elevated liver function tests (LFT) suggestive of obstructive jaundice, MRCP done showed diffusely enlarged abnormal appearing pancreas with loss of normal lobulated contours, and IgG4 antibody level was 765 mg/dL. EUS revealed a diffusely hypoechoic and rounded pancreatic parenchyma with distal common bile duct (CBD) stricture and dilated proximal CBD and common hepatic duct (CHD). ERCP showed tight mid to distal CBD stricture that needed dilatation, sphincterotomy, and placement of stent that led to significant improvement in the symptoms and bilirubin level. Based on clinical, radiological, and immunological findings, a definitive diagnosis of AIP was made. Patient was started on prednisone 40 mg/day and she clinically responded in 4 weeks.

15.
J Med Eng ; 20142014.
Artigo em Inglês | MEDLINE | ID: mdl-25506590

RESUMO

The development of an Automated System for Asthma Monitoring (ADAM) is described. This consists of a consumer electronics mobile platform running a custom application. The application acquires an audio signal from an external user-worn microphone connected to the device analog-to-digital converter (microphone input). This signal is processed to determine the presence or absence of cough sounds. Symptom tallies and raw audio waveforms are recorded and made easily accessible for later review by a healthcare provider. The symptom detection algorithm is based upon standard speech recognition and machine learning paradigms and consists of an audio feature extraction step followed by a Hidden Markov Model based Viterbi decoder that has been trained on a large database of audio examples from a variety of subjects. Multiple Hidden Markov Model topologies and orders are studied. Performance of the recognizer is presented in terms of the sensitivity and the rate of false alarm as determined in a cross-validation test.

16.
JMIR Mhealth Uhealth ; 2(2): e27, 2014 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-25100184

RESUMO

BACKGROUND: Many adolescents suffer serious asthma related morbidity that can be prevented by adequate self-management of the disease. The accurate symptom monitoring by patients is the most fundamental antecedent to effective asthma management. Nonetheless, the adequacy and effectiveness of current methods of symptom self-monitoring have been challenged due to the individuals' fallible symptom perception, poor adherence, and inadequate technique. Recognition of these limitations led to the development of an innovative device that can facilitate continuous and accurate monitoring of asthma symptoms with minimal disruption of daily routines, thus increasing acceptability to adolescents. OBJECTIVE: The objectives of this study were to: (1) describe the development of a novel symptom monitoring device for teenagers (teens), and (2) assess their perspectives on the usability and acceptability of the device. METHODS: Adolescents (13-17 years old) with and without asthma participated in the evolution of an automated device for asthma monitoring (ADAM), which comprised three phases, including development (Phase 1, n=37), validation/user acceptability (Phase 2, n=84), and post hoc validation (Phase 3, n=10). In Phase 1, symptom algorithms were identified based on the acoustic analysis of raw symptom sounds and programmed into a popular mobile system, the iPod. Phase 2 involved a 7 day trial of ADAM in vivo, and the evaluation of user acceptance using an acceptance survey and individual interviews. ADAM was further modified and enhanced in Phase 3. RESULTS: Through ADAM, incoming audio data were digitized and processed in two steps involving the extraction of a sequence of descriptive feature vectors, and the processing of these sequences by a hidden Markov model-based Viterbi decoder to differentiate symptom sounds from background noise. The number and times of detected symptoms were stored and displayed in the device. The sensitivity (true positive) of the updated cough algorithm was 70% (21/30), and, on average, 2 coughs per hour were identified as false positive. ADAM also kept track of the their activity level throughout the day using the mobile system's built in accelerometer function. Overall, the device was well received by participants who perceived it as attractive, convenient, and helpful. The participants recognized the potential benefits of the device in asthma care, and were eager to use it for their asthma management. CONCLUSIONS: ADAM can potentially automate daily symptom monitoring with minimal intrusiveness and maximal objectivity. The users' acceptance of the device based on its recognized convenience, user-friendliness, and usefulness in increasing symptom awareness underscores ADAM's potential to overcome the issues of symptom monitoring including poor adherence, inadequate technique, and poor symptom perception in adolescents. Further refinement of the algorithm is warranted to improve the accuracy of the device. Future study is also needed to assess the efficacy of the device in promoting self-management and asthma outcomes.

17.
ACG Case Rep J ; 1(4): 196-8, 2014 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-26157874

RESUMO

Renal cell carcinoma (RCC) is a rare adult malignancy, and one-third of cases present with distant metastases at the time of diagnosis. Early gastric metastasis is exceedingly rare. We describe an adult male with synchronous gastric metastasis of RCC at the time of diagnosis in the absence of gastrointestinal symptoms. We report the fifth case of RCC with synchronous gastric metastasis and the only case with early presentation in the absence of gastrointestinal symptoms.

18.
Artigo em Inglês | MEDLINE | ID: mdl-25571239

RESUMO

External electrical cardioversion has been used as a therapeutic option to terminate atrial fibrillation (AF) and restore sinus rhythm (SR). However, identifying patients who would benefit from this therapy is still an active area of research. In this study, we develop new time-frequency features to characterize the atrial activity (AA) and to predict the success of electrical cardioversion therapy by identifying the AF patients who will maintain SR in the long term. New features are extracted from the surface AA using a matching pursuit (MP) decomposition with various combinations of wavelet families. The performance of the features is validated using a dataset of AF patients who underwent electrical cardioversion therapy. Results indicate that the developed features are significantly (p-value <; 0.05) correlated with SR maintenance which suggests that the MP decomposition captures detailed morphological information of AA that may potentially be used to guide the therapy of AF patients.


Assuntos
Fibrilação Atrial/diagnóstico , Fibrilação Atrial/fisiopatologia , Fibrilação Atrial/terapia , Cardioversão Elétrica , Átrios do Coração/fisiopatologia , Humanos , Contração Miocárdica , Recidiva , Processamento de Sinais Assistido por Computador
20.
Chemosphere ; 90(2): 410-6, 2013 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-22967928

RESUMO

Nanoparticles are a major product from the nanotechnology industry and have been shown to have a potentially large environmental exposure and hazard. In this study, sterically stabilised polyvinyl pyrrolidone (PVP) 7 nm gold nanoparticles (NPs) were produced and characterised as prepared by surface plasmon resonance (SPR), size and aggregation, morphology and surface charge. Changes in these properties with changes in environmentally relevant conditions (pH, ionic strength, Ca concentration and fulvic acid presence) were quantified. These sterically stabilised NPs showed no aggregation with changes in pH or inorganic ions, even under high (0.1 M) Ca concentrations. In addition, the presence of fulvic acid resulted in no observable changes in SPR, size, aggregation or surface chemistry, suggesting limited interaction between the PVP stabilised nanoparticles and fulvic acid. Due to the lack of aggregation and interaction, these NPs are expected to be highly mobile and potentially bioavailable in the environment.


Assuntos
Ouro/química , Nanopartículas Metálicas/química , Povidona/análise , Benzopiranos , Concentração de Íons de Hidrogênio , Concentração Osmolar , Povidona/química , Ressonância de Plasmônio de Superfície
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