Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 21
Filtrar
Mais filtros

Base de dados
País/Região como assunto
Tipo de documento
Intervalo de ano de publicação
1.
Biochem Biophys Res Commun ; 712-713: 149946, 2024 Jun 18.
Artigo em Inglês | MEDLINE | ID: mdl-38643717

RESUMO

Platelets are small anucleate cells that play a key role in thrombosis and hemostasis. Our group previously identified apolipoprotein A-IV (apoA-IV) as an endogenous inhibitor of thrombosis by competitive blockade of the αIIbß3 integrin on platelets. ApoA-IV inhibition of platelets was dependent on the N-terminal D5/D13 residues, and enhanced with absence of the C-terminus, suggesting it sterically hinders its N-terminal platelet binding site. The C-terminus is also the site of common apoA-IV polymorphisms apoA-IV-1a (T347S) and apoA-IV-2 (Q360H). Interestingly, both are linked with an increased risk of cardiovascular disease, however, the underlying mechanism remains unclear. Here, we generated recombinant apoA-IV and found that the Q360H or T347S polymorphisms dampened its inhibition of platelet aggregation in human platelet-rich plasma and gel-filtered platelets, reduced its inhibition of platelet spreading, and its inhibition of P-selectin on activated platelets. Using an ex vivo thrombosis assay, we found that Q360H and T347S attenuated its inhibition of thrombosis at both high (1800s-1) and low (300s-1) shear rates. We then demonstrate a conserved monomer-dimer distribution among apoA-IV WT, Q360H, and T347S and use protein structure modelling software to show Q360H and T347S enhance C-terminal steric hindrance over the N-terminal platelet-binding site. These data provide critical insight into increased cardiovascular risk for individuals with Q360H or T347S polymorphisms.


Assuntos
Apolipoproteínas A , Plaquetas , Agregação Plaquetária , Trombose , Humanos , Trombose/genética , Trombose/metabolismo , Agregação Plaquetária/efeitos dos fármacos , Agregação Plaquetária/genética , Plaquetas/metabolismo , Plaquetas/efeitos dos fármacos , Polimorfismo Genético , Apoproteína(a)/genética , Apoproteína(a)/metabolismo , Apoproteína(a)/química , Selectina-P/genética , Selectina-P/metabolismo
2.
Ann Vasc Surg ; 105: 1-9, 2024 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-38492727

RESUMO

BACKGROUND: The stroke rate in blunt cerebrovascular injury (BCVI) varies from 25% without treatment to less than 8% with antithrombotic therapy. There is no consensus on the optimal management to prevent stroke BCVI. We investigated the efficacy and safety of oral Aspirin (ASA) 81 mg to prevent BCVI-related stroke compared to historically reported stroke rates with ASA 325 mg and heparin. METHODS: A single-center retrospective study included adult trauma patients who received oral ASA 81 mg for BCVI management between 2013 and 2022. Medical records were reviewed for demographic and injury characteristics, imaging findings, treatment-related complications, and outcomes. RESULTS: Eighty-four patients treated with ASA 81 mg for BCVI were identified. The mean age was 41.50 years, and 61.9% were male. The mean Injury Severity Score and Glasgow Coma Scale were 19.82 and 12.12, respectively. A total of 101 vessel injuries were identified, including vertebral artery injuries in 56.4% and carotid artery injuries in 44.6%. Traumatic brain injury was found in 42.9%, and 16.7% of patients had a solid organ injur. Biffl grade I (52.4%) injury was the most common, followed by grade II (37.6%) and grade III (4.9%). ASA 81 mg was started in the first 24 hours in 67.9% of patients, including 20 patients with traumatic brain injury and 8 with solid organ injuries. BCVI-related stroke occurred in 3 (3.5%) patients with Biffl grade II (n = 2) and III (n = 1). ASA-related complications were not identified in any patient. The mean length of stay in the hospital was 10.94 days, and 8 patients died during hospitalization due to complications of polytrauma. Follow-up with computed tomography angiography was performed in 8 (9.5%) patients, which showed improvement in 5 and a stable lesion in 3 at a mean time of 58 days after discharge. CONCLUSIONS: In the absence of clear guidelines regarding appropriate medication, BCVI management should be individualized case-by-case through a multidisciplinary approach. ASA 81 mg is a viable option for BCVI-related stroke prevention compared to the reported stroke rates (2%-8%) with commonly used antithrombotics like heparin and ASA 325 mg. Future prospective studies are needed to provide insight into the safety and efficacy of the current commonly used agent in managing BCVI.


Assuntos
Aspirina , Traumatismo Cerebrovascular , Inibidores da Agregação Plaquetária , Acidente Vascular Cerebral , Ferimentos não Penetrantes , Humanos , Masculino , Feminino , Estudos Retrospectivos , Resultado do Tratamento , Adulto , Aspirina/efeitos adversos , Aspirina/administração & dosagem , Pessoa de Meia-Idade , Acidente Vascular Cerebral/prevenção & controle , Acidente Vascular Cerebral/etiologia , Acidente Vascular Cerebral/diagnóstico , Inibidores da Agregação Plaquetária/efeitos adversos , Inibidores da Agregação Plaquetária/administração & dosagem , Ferimentos não Penetrantes/diagnóstico por imagem , Fatores de Risco , Traumatismo Cerebrovascular/diagnóstico por imagem , Traumatismo Cerebrovascular/complicações , Fatores de Tempo , Administração Oral , Medição de Risco , Adulto Jovem , Idoso
3.
Oncogene ; 42(40): 2956-2970, 2023 09.
Artigo em Inglês | MEDLINE | ID: mdl-37612524

RESUMO

Lymphatic metastasis is recognized as the leading manner of metastasis in bladder cancer (BLCa), but hematogenous metastasis accounts for a majority of cancer-associated deaths. The past two decades have witnessed tremendous attention in long non-coding RNAs (lncRNAs), which are a new hope for the development of targeted drug therapy for metastatic cancers; however, the underlying mechanism of lncRNAs involved in BLCa hematogenous metastasis remains to be elucidated. Here, we identified BLCa-associated transcript 3 (BLACAT3), a lncRNA, which was aberrantly upregulated in BLCa and corelated with poor prognosis of patients with muscle-invasive bladder cancer. Methodologically, m6A epitranscriptomic microarray, RNA sequencing and mass spectrometry (MS) were used to screen the key molecules of the regulatory axis. Functional assays, animal models and clinical samples were used to explore the roles of BLACAT3 in BLCa in vitro and in vivo. Mechanistically, m6A modification contributes to BLACAT3 upregulation by stabilizing RNA structure. BLACAT3 recruits YBX3 to shuttle into the nucleus, synergistically enhances NCF2 transcription, and promotes BLCa angiogenesis and hematogenous metastasis by activating downstream NF-κB signaling. Our findings will develop prognosis prediction tools for BLCa patients and discover novel therapeutic biological targets for metastatic BLCa.


Assuntos
RNA Longo não Codificante , Neoplasias da Bexiga Urinária , Animais , Humanos , NADPH Oxidases/genética , NF-kappa B/genética , RNA Longo não Codificante/genética , Transdução de Sinais/genética , Regulação para Cima , Neoplasias da Bexiga Urinária/genética , Neoplasias da Bexiga Urinária/patologia , Neovascularização Patológica/genética , Neovascularização Patológica/metabolismo , Metástase Neoplásica/genética
4.
Genes (Basel) ; 14(9)2023 Aug 29.
Artigo em Inglês | MEDLINE | ID: mdl-37761861

RESUMO

BACKGROUND: The immune response in COVID-19 is characterized by the release of alarmin cytokines, which play crucial roles in immune activation and inflammation. The interplay between these cytokines and genetic variations may influence disease severity and outcomes, while sex differences might further contribute to variations in the immune response. METHODS: We measured the levels of alarmin cytokines in a cohort of COVID-19 and non-COVID-19 patients using a sensitive Meso Scale Discovery system. Additionally, we conducted an SNP analysis to identify genetic variations within the IL-33 and TSLP genes. The association between these genetic variations, cytokine production, and COVID-19 severity was examined. RESULTS: Our findings revealed elevated levels of IL-33 and IL-25 in COVID-19-positive patients compared to COVID-19-negative patients (p < 0.05), indicating their potential as therapeutic targets for disease modulation. Moreover, a minor allele within the IL-33 gene (rs3939286) was found to be associated with a protective effect against severe COVID-19 (p < 0.05), and minor alleles of the TSLP gene (rs2289276 and rs13806933) were found to significantly reduce TSLP protein levels in serum (p < 0.05). Sex-specific effects of TSLP and IL-33 SNPs were observed, suggesting a potential influence of sex hormones and genetic variations on the regulation of cytokine production. CONCLUSION: The present study highlights the importance of alarmin cytokines and genetic variations in COVID-19 severity, providing valuable insights into personalized treatment approaches. Our results suggest that targeting alarmin cytokines may offer potential therapeutic benefits in managing COVID-19. Furthermore, the sex-specific effects of genetic variations emphasize the need to consider individual genetic profiles and sex differences when designing targeted interventions.

5.
Research (Wash D C) ; 6: 0124, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37223472

RESUMO

The COVID-19 pandemic caused by SARS-CoV-2 virus is an ongoing global health burden. Severe cases of COVID-19 and the rare cases of COVID-19 vaccine-induced-thrombotic-thrombocytopenia (VITT) are both associated with thrombosis and thrombocytopenia; however, the underlying mechanisms remain inadequately understood. Both infection and vaccination utilize the spike protein receptor-binding domain (RBD) of SARS-CoV-2. We found that intravenous injection of recombinant RBD caused significant platelet clearance in mice. Further investigation revealed the RBD could bind platelets, cause platelet activation, and potentiate platelet aggregation, which was exacerbated in the Delta and Kappa variants. The RBD-platelet interaction was partially dependent on the ß3 integrin as binding was significantly reduced in ß3-/- mice. Furthermore, RBD binding to human and mouse platelets was significantly reduced with related αIIbß3 antagonists and mutation of the RGD (arginine-glycine-aspartate) integrin binding motif to RGE (arginine-glycine-glutamate). We developed anti-RBD polyclonal and several monoclonal antibodies (mAbs) and identified 4F2 and 4H12 for their potent dual inhibition of RBD-induced platelet activation, aggregation, and clearance in vivo, and SARS-CoV-2 infection and replication in Vero E6 cells. Our data show that the RBD can bind platelets partially though αIIbß3 and induce platelet activation and clearance, which may contribute to thrombosis and thrombocytopenia observed in COVID-19 and VITT. Our newly developed mAbs 4F2 and 4H12 have potential not only for diagnosis of SARS-CoV-2 virus antigen but also importantly for therapy against COVID-19.

6.
Nanotechnology ; 23(7): 075102, 2012 Feb 24.
Artigo em Inglês | MEDLINE | ID: mdl-22260928

RESUMO

Understanding the control of the optical and plasmonic properties of unique nanosystems--gold nanostars--both experimentally and theoretically permits superior design and fabrication for biomedical applications. Here, we present a new, surfactant-free synthesis method of biocompatible gold nanostars with adjustable geometry such that the plasmon band can be tuned into the near-infrared region 'tissue diagnostic window', which is most suitable for in vivo imaging. Theoretical modelling was performed for multiple-branched 3D nanostars and yielded absorption spectra in good agreement with experimental results. The plasmon band shift was attributed to variations in branch aspect ratio, and the plasmon band intensifies with increasing branch number, branch length, and overall star size. Nanostars showed an extremely strong two-photon photoluminescence (TPL) process. The TPL imaging of wheat-germ agglutinin (WGA) functionalized nanostars on BT549 breast cancer cells and of PEGylated nanostars circulating in the vasculature, examined through a dorsal window chamber in vivo in laboratory mouse studies, demonstrated that gold nanostars can serve as an efficient contrast agent for biological imaging applications.


Assuntos
Materiais Biocompatíveis , Neoplasias da Mama/diagnóstico , Meios de Contraste , Ouro , Nanoestruturas , Nanotecnologia/métodos , Animais , Materiais Biocompatíveis/síntese química , Materiais Biocompatíveis/química , Linhagem Celular Tumoral , Meios de Contraste/química , Feminino , Ouro/química , Humanos , Luminescência , Medições Luminescentes/métodos , Camundongos , Camundongos Nus , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Aglutininas do Germe de Trigo/química
7.
Nanomedicine ; 8(8): 1355-63, 2012 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-22370335

RESUMO

Gold nanostars offer unique plasmon properties that efficiently transduce photon energy into heat for photothermal therapy. Nanostars, with their small core size and multiple long thin branches, exhibit high absorption cross-sections that are tunable in the near-infrared region with relatively low scattering effect, making them efficient photothermal transducers. Here, we demonstrate particle tracking and photothermal ablation both in vitro and in vivo. Using SKBR3 breast cancer cells incubated with bare nanostars, we observed photothermal ablation within 5 minutes of irradiation (980-nm continuous-wave laser, 15 W/cm2). On a mouse injected systemically with PEGylated nanostars for 2 days, extravasation of nanostars was observed and localized photothermal ablation was demonstrated on a dorsal window chamber within 10 minutes of irradiation (785-nm continuous-wave laser, 1.1 W/cm2). These preliminary results of plasmon-enhanced localized hyperthermia are encouraging and have illustrated the potential of gold nanostars as efficient photothermal agents in cancer therapy. FROM THE CLINICAL EDITOR: Gold nanostars are tunable in the near-infrared region with low scattering, thus enable photothermal therapy. Encouraging preliminary results of plasmon-enhanced localized hyperthermia both in vitro and in vivo demonstrate that Au nanostars may be efficient photothermal agents for cancer therapy.


Assuntos
Neoplasias da Mama/terapia , Ouro , Hipertermia Induzida , Nanopartículas , Animais , Linhagem Celular Tumoral , Feminino , Ouro/química , Ouro/uso terapêutico , Humanos , Camundongos , Nanopartículas/química , Nanopartículas/uso terapêutico , Fototerapia , Ressonância de Plasmônio de Superfície
8.
J Nurs Adm ; 41(7-8): 299-305, 2011.
Artigo em Inglês | MEDLINE | ID: mdl-21799360

RESUMO

OBJECTIVE: : The purpose of this study was to examine how nursing is viewed by the nation's decision makers and opinion leaders. BACKGROUND: : Nurses comprise the largest subgroup of the health and healthcare workforce. The public recognizes nurses' contributions, consistently ranking them highest in honesty and ethics. Yet, significant barriers remain in nurses achieving substantial leadership positions in health and healthcare delivery and policy. METHODS: : The study sampled a broad cross section of American opinion leaders in the public and private sector, academia, and trade organizations. More than 1,500 opinion leaders were interviewed by telephone interviewers. RESULTS: : The opinion leaders viewed government (75%) and health insurance executives (56%) as the groups most likely to exert a great deal of influence on health reform, compared with 14% for nurses. Government respondents were significantly different than all other respondents; 23% of these respondents said nurses have a great deal of influence in healthcare reform, compared with 14% of other individuals. CONCLUSION: : Although nurses are viewed as knowledgeable sources of health information, nurses are not viewed as leaders in the development of healthcare systems and delivery. The opinion leaders' survey identifies barriers to nurses assuming a greater leadership role, including management skills and knowledge.


Assuntos
Reforma dos Serviços de Saúde , Liderança , Papel do Profissional de Enfermagem , Formulação de Políticas , Opinião Pública , Estudos Transversais , Humanos , Estados Unidos
9.
Nanotechnology ; 21(31): 315203, 2010 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-20634565

RESUMO

This report compares COMSOL's finite element method (FEM) algorithm with the Mie theory for solving the electromagnetic fields in the vicinity of a silica-silver core-shell nanoparticle when excited by a radiating dipole. The novelty of this investigation lies in the excitation source of the nanoshell system: an oscillating electric dipole is frequently used as a model for both molecular scattering and molecular fluorescence; moreover, a common classical model of atomic or molecular spontaneous emission is a decaying electric dipole. The radiated power spectra were evaluated both analytically and numerically by integrating the Poynting vector around 20, 60 and 100 nm nanoshells, thereby solving the total and scattered fields generated by a dipole positioned inside the core and in the surrounding air medium, respectively. The agreement was excellent in amplitude, plasmon resonance peak position and full width at half-maximum. The FEM algorithm also generates accurate solutions of the near-field electromagnetics in the spatial domain, where the E-field behavior as a function of polar angle theta for a fixed observation radius was evaluated. The quasistatic approximation, which is valid for small nanoparticles, is also employed to assess its limitations relative to the Mie and FEM algorithms.

10.
J Am Chem Soc ; 131(34): 12032-3, 2009 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-19655747

RESUMO

Size-controlled gallium nanoparticles deposited on sapphire were explored as alternative substrates to enhance Raman spectral signatures. Gallium's resilience following oxidation is inherently advantageous in comparison with silver for practical ex vacuo nonsolution applications. Ga nanoparticles were grown using a simple molecular beam epitaxy-based fabrication protocol, and monitoring their corresponding surface plasmon resonance energy through in situ spectroscopic ellipsometry allowed the nanoparticles to be easily controlled for size. The Raman spectra obtained from cresyl fast violet (CFV) deposited on substrates with differing mean nanoparticle sizes represent the first demonstration of enhanced Raman signals from reproducibly tunable self-assembled Ga nanoparticles. Nonoptimized aggregate enhancement factors of approximately 80 were observed from the substrate with the smallest Ga nanoparticles for CFV dye solutions down to a dilution of 10 ppm.


Assuntos
Gálio/química , Nanopartículas Metálicas/química , Análise Espectral Raman/métodos , Óxido de Alumínio/química , Propriedades de Superfície , Temperatura
11.
AMA J Ethics ; 21(2): E188-191, 2019 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-30794129

RESUMO

In June 2018, the American Medical Association adopted new policy to provide a broad framework for the evolution of artificial intelligence (AI) in health care that is designed to help ensure that AI realizes the benefits it promises for patients, physicians, and the health care community.


Assuntos
Inteligência Artificial/legislação & jurisprudência , Inteligência Artificial/normas , Atenção à Saúde/legislação & jurisprudência , Atenção à Saúde/normas , Guias como Assunto , Formulação de Políticas , Humanos , Estados Unidos
12.
BMJ Open ; 8(7): e022185, 2018 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-30068620

RESUMO

OBJECTIVES: Patients with congestive heart failure (CHF) may be at a higher risk of mortality from sepsis than patients without CHF due to insufficient cardiovascular reserves during systemic infections. The aim of this study is to compare sepsis-related mortality between CHF and no CHF in patients presenting to a tertiary medical centre. DESIGN: A single-centre, retrospective, cohort study. SETTING: Conducted in an academic emergency department (ED) between January 2010 and January 2015. Patients' charts were queried via the hospital's electronic system. Patients with a diagnosis of sepsis were included. Descriptive analysis was performed on the demographics, characteristics and outcomes of patients with sepsis of the study population. PARTICIPANTS: A total of 174 patients, of which 87 (50%) were patients with CHF. PRIMARY AND SECONDARY OUTCOMES: The primary outcome of the study was in-hospital mortality. Secondary outcomes included intensive care unit (ICU) and hospital lengths of stay, and differences in interventions between the two groups. RESULTS: Patients with CHF had a higher in-hospital mortality (57.5% vs 34.5%). Patients with sepsis and CHF had higher odds of death compared with the control population (OR 2.45; 95% CI 1.22 to 4.88). Secondary analyses showed that patients with CHF had lower instances of bacteraemia on presentation to the ED (31.8% vs 46.4%). They had less intravenous fluid requirements in first 24 hours (2.75±2.28 L vs 3.67±2.82 L, p =0.038), had a higher rate of intubation in the ED (24.2% vs 10.6%, p=0.025) and required more dobutamine in the first 24 hours (16.1% vs 1.1%, p<0.001). ED length of stay was found to be lower in patients with CHF (15.12±24.45 hours vs 18.17±26.13 hours, p=0.418) and they were more likely to be admitted to the ICU (59.8% vs 48.8%, p=0.149). CONCLUSION: Patients with sepsis and CHF experienced an increased hospital mortality compared with patients without CHF.


Assuntos
Serviço Hospitalar de Emergência , Insuficiência Cardíaca Sistólica/mortalidade , Insuficiência de Múltiplos Órgãos/mortalidade , Sepse/mortalidade , Centros de Atenção Terciária , Idoso , Idoso de 80 Anos ou mais , Feminino , Insuficiência Cardíaca Sistólica/fisiopatologia , Insuficiência Cardíaca Sistólica/terapia , Mortalidade Hospitalar , Humanos , Líbano/epidemiologia , Tempo de Internação/estatística & dados numéricos , Masculino , Pessoa de Meia-Idade , Insuficiência de Múltiplos Órgãos/fisiopatologia , Insuficiência de Múltiplos Órgãos/terapia , Avaliação de Resultados da Assistência ao Paciente , Estudos Retrospectivos , Sepse/fisiopatologia , Sepse/terapia , Sinais Vitais
13.
J Immunol Sci ; 2(1): 1-8, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-37600154

RESUMO

Cancer has been a significant threat to human health with more than eight million deaths each year in the world. There is an urgent need to develop novel methods to improve cancer management. Biocompatible gold nanostars (GNS) with tip-enhanced electromagnetic and optical properties have been developed and applied for multifunctional cancer diagnostics and therapy (theranostics). The GNS platform can be used for multiple sensing, imaging and treatment modalities, such as surface-enhanced Raman scattering, two-photon photoluminescence, magnetic resonance imaging and computed tomography as well as photothermal therapy and immunotherapy. GNS-mediated photothermal therapy combined with checkpoint immunotherapy has been found to reverse tumor-mediated immunosuppression, leading to the treatment of not only primary tumors but also cancer metastasis as well as inducing effective long-lasting immunity, i.e. an anticancer 'vaccine' effect.

14.
ACS Appl Mater Interfaces ; 8(28): 18157-64, 2016 Jul 20.
Artigo em Inglês | MEDLINE | ID: mdl-27347606

RESUMO

Amplification of optical signals is useful for a wide variety of applications, ranging from data signal transmission to chemical sensing and biomedical diagnostics. One such application in chemical sensing is surface-enhanced Raman scattering (SERS), an important technique for increasing the Raman signal using the plasmonic effect of enhanced electromagnetic fields associated with metallic nanostructures. One of the most important limitations of SERS-based amplification is the difficulty to reproducibly control the SERS signal. Here, we describe the design and implementation of a unique hybrid system capable of producing reversible gating of plasmonic coupling for Raman signal amplification. The hybrid system is composed of two subsystems: (1) colloidal magneto-plasmonic nanoparticles for SERS enhancement and (2) a micromagnet substrate with an externally applied magnetic field to modulate the colloidal nanoparticles. For this proof of concept demonstration, the nanoparticles were labeled with a Raman-active dye, and it was shown that the detected SERS signal could be reproducibly modulated by controlling the externally applied magnetic field. The developed system provides a simple, robust, inexpensive, and reusable device for SERS signal modulation. These properties will open up new possibilities for optical signal amplification and gating as well for high-throughput, reproducible SERS detection.

15.
Lab Chip ; 2(1): 50-5, 2002 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-15100862

RESUMO

We present a method for the ultra rapid prototyping of microfluidic systems using liquid phase photopolymerization, requiring less than 5 min from design to prototype. Microfluidic device fabrication is demonstrated in a universal plastic or glass cartridge. The method consists of the following steps: introduction of liquid prepolymer into the cartridge, UV exposure through a mask to define the channel geometry, removal of unpolymerized prepolymer, and a final rinse. Rapidly fabricated masters for polydimethylsiloxane micromolding are also demonstrated. The master making process is compared to SU-8 50 photoresist processes. Press-on connectors are developed and demonstrated. All materials used are commercially available and low cost. An extension of these methods (mix and match) is presented that allows for maximal design flexibility and integration with a variety of existing fluidic geometries, components, and processes.

16.
J Raman Spectrosc ; 44(2): 234-239, 2013 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-24839346

RESUMO

Plasmonic gold nanostars offer a new platform for Surface-Enhanced Raman Scattering (SERS). However, due to the presence of organic surfactant on the nanoparticles, SERS characterization and application of nanostar ensembles in solution have been challenging. Here we applied our newly developed surfactant-free nanostars for SERS characterization and application. The SERS enhancement factors (EF) of silver spheres, gold spheres and nanostars of similar sizes and concentration were compared. Under 785 nm excitation, nanostars and silver spheres have similar EF, and both are much stronger than gold spheres. Having plasmon matching the incident energy and multiple "hot spots" on the branches bring forth strong SERS response without the need to aggregate. Intracellular detection of silica-coated SERS-encoded nanostars was also demonstrated in breast cancer cells. The non-aggregated field enhancement makes the gold nanostar ensemble a promising agent for SERS bioapplications.

17.
Nanoscale ; 5(21): 10127-40, 2013 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-24056945

RESUMO

This article provides an overview of the development and applications of plasmonics-active nanoprobes in our laboratory for chemical sensing, medical diagnostics and therapy. Molecular Sentinel nanoprobes provide a unique tool for DNA/RNA biomarker detection both in a homogeneous solution or on a chip platform for medical diagnostics. The possibility of combining spectral selectivity and high sensitivity of the surface-enhanced Raman scattering (SERS) process with the inherent molecular specificity of nanoprobes provides an important multiplex diagnostic modality. Gold nanostars can provide an excellent multi-modality platform, combining two-photon luminescence with photothermal therapy as well as Raman imaging with photodynamic therapy. Several examples of optical detection using SERS and photonics-based treatments are presented to illustrate the usefulness and potential of the plasmonic nanoprobes for theranostics, which seamlessly combines diagnostics and therapy.


Assuntos
DNA/análise , Nanoestruturas/química , Neoplasias/diagnóstico , Análise Espectral Raman , Biomarcadores/análise , Técnicas Biossensoriais , Ouro/química , Humanos , Nanoestruturas/uso terapêutico , Neoplasias/tratamento farmacológico , Fotoquimioterapia , Fármacos Fotossensibilizantes/uso terapêutico
18.
J Phys Chem C Nanomater Interfaces ; 116(13): 7534-7545, 2012 Apr 05.
Artigo em Inglês | MEDLINE | ID: mdl-24839506

RESUMO

The "Nanowave" substrate, comprising a close-packed array of nanospheres onto which a thin metal shell of silver or gold is deposited, was first fabricated in our laboratory in 1984 and used as a surface-enhanced Raman scattering (SERS)-active substrate for the sensitive and reproducible detection of analytes. More than twenty-five years after the first experimental demonstration of the effectiveness of this substrate, numerical simulations are sufficiently powerful and versatile to mimic this geometry in three dimensional space and confirm the experimentally measured plasmonic behavior at the substrate's surface. The study confirms that an in-plane polarized incident plane wave generates strong enhancements in the interstitial spaces between individual metal-coated nanospheres, thus producing closely packed arrays of hot spots underlining the strong SERS effect of the Nanowave substrate structures. The surface-averaged SERS enhancement exhibited by the Nanowaves was evaluated and compared for different metal thicknesses. The effect of structural confinement on the plasmonic behavior of the Nanowave structure was investigated by varying the structural confinement of the substrate in the plane parallel to the incident excitation. The Nanowave is an inexpensive, reproducible and effective plasmonics-active substrate that has the potential to be used for SERS studies requiring high detection sensitivity.

19.
J Phys Chem C Nanomater Interfaces ; 114(16): 7480-7488, 2010 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-24839505

RESUMO

This study involves two aspects of our investigations of plasmonics-active systems: (i) theoretical and simulation studies and (ii) experimental fabrication of plasmonics-active nanostructures. Two types of nanostructures are selected as the model systems for their unique plasmonics properties: (1) nanoparticles and (2) nanowires on substrate. Special focus is devoted to regions where the electromagnetic field is strongly concentrated by the metallic nanostructures or between nanostructures. The theoretical investigations deal with dimers of nanoparticles and nanoshells using a semi-analytical method based on a multipole expansion (ME) and the finite-element method (FEM) in order to determine the electromagnetic enhancement, especially at the interface areas of two adjacent nanoparticles. The experimental study involves the design of plasmonics-active nanowire arrays on substrates that can provide efficient electromagnetic enhancement in regions around and between the nanostructures. Fabrication of these nanowire structures over large chip-scale areas (from a few millimeters to a few centimeters) as well as FDTD simulations to estimate the EM fields between the nanowires are described. The application of these nanowire chips using surface-enhanced Raman scattering (SERS) for detection of chemicals and labeled DNA molecules is described to illustrate the potential of the plasmonics chips for sensing.

20.
ACS Nano ; 3(9): 2776-88, 2009 Sep 22.
Artigo em Inglês | MEDLINE | ID: mdl-19678677

RESUMO

The spatial and spectral responses of the plasmonic fields induced in the gap of 3-D nanoshell dimers of gold and silver are comprehensively investigated and compared via theory and simulation using the multipole expansion (ME) and the finite element method (FEM) in COMSOL, respectively. The E-field in the dimer gap was evaluated and compared as a function of shell thickness, interparticle distance, and size. The E-field increased with decreasing shell thickness, decreasing interparticle distance, and increasing size, with the error between the two methods ranging from 1 to 10%, depending on the specific combination of these three variables. This error increases several fold with increasing dimer size, as the quasi-static approximation breaks down. A consistent overestimation of the plasmon's fwhm and red shifting of the plasmon peak occurs with FEM, relative to ME, and it increases with decreasing shell thickness and interparticle distance. The size effect that arises from surface scattering of electrons is addressed and shown to be especially prominent for thin shells, for which significant damping, broadening, and shifting of the plasmon band is observed; the size effect also affects large nanoshell dimers, depending on their relative shell thickness, but to a lesser extent. This study demonstrates that COMSOL is a promising simulation environment to quantitatively investigate nanoscale electromagnetics for the modeling and designing of surface-enhanced Raman scattering (SERS) substrates.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA