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1.
J Med Chem ; 63(23): 15037-15049, 2020 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-33206510

RESUMO

Macrophage elastase [matrix metalloproteinase (MMP)-12] is the most upregulated MMP in abdominal aortic aneurysm (AAA) and, hence, MMP-12-targeted imaging may predict AAA progression and rupture risk. Here, we report the design, synthesis, and evaluation of three novel hydroxamate-based selective MMP-12 inhibitors (CGA, CGA-1, and AGA) and the methodology to obtain MMP-12 selectivity from hydroxamate-based panMMP inhibitors. Also, we report two 99mTc-radiotracers, 99mTc-AGA-1 and 99mTc-AGA-2, derived from AGA. 99mTc-AGA-2 displayed faster blood clearance in mice and better radiochemical stability compared to 99mTc-AGA-1. Based on this, 99mTc-AGA-2 was chosen as the lead tracer and tested in murine AAA. 99mTc-AGA-2 uptake detected by autoradiography was significantly higher in AAA compared to normal aortic regions. Specific binding of the tracer to MMP-12 was demonstrated through ex vivo competition. Accordingly, this study introduces a novel family of selective MMP-12 inhibitors and tracers, paving the way for further development of these agents as therapeutic and imaging agents.

2.
Artigo em Inglês | MEDLINE | ID: mdl-32126587

RESUMO

The extracellular matrix (ECM) consists of proteins and carbohydrates that supports different biological structures and processes such as tissue development, elasticity, and preservation of organ structure. Diseases involving inflammation, fibrosis, tumor invasion, and injury are all attributed to the transition of the ECM from homeostasis to remodeling, which can significantly change the biochemical and biomechanical features of ECM components. While contrast agents have played an indispensable role in facilitating clinical diagnosis of diseases using magnetic resonance imaging (MRI), there is a strong need to develop novel biomarker-targeted imaging probes for in vivo visualization of biological processes and pathological alterations at a cellular and molecular level, for both early diagnosis and monitoring drug treatment. Herein, we will first review the pathological accumulation and characterization of ECM proteins recognized as important molecular features of diseases. Developments in MRI probes targeting ECM proteins such as collagen, fibronectin, and elastin via conjugation of existing contrast agents to targeting moieties and their applications to various diseases, are also reviewed. We have also reviewed our progress in the development of collagen-targeted protein MRI contrast agent with significant improvement in relaxivity and metal binding specificity, and their applications in early detection of fibrosis and metastatic cancer. This article is categorized under: Diagnostic Tools > in vivo Nanodiagnostics and Imaging Biology-Inspired Nanomaterials > Peptide-Based Structures Biology-Inspired Nanomaterials > Protein and Virus-Based Structures.

3.
Sci Adv ; 6(6): eaav7504, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-32083172

RESUMO

Liver metastases often progress from primary cancers including uveal melanoma (UM), breast, and colon cancer. Molecular biomarker imaging is a new non-invasive approach for detecting early stage tumors. Here, we report the elevated expression of chemokine receptor 4 (CXCR4) in liver metastases in UM patients and metastatic UM mouse models, and development of a CXCR4-targeted MRI contrast agent, ProCA32.CXCR4, for sensitive MRI detection of UM liver metastases. ProCA32.CXCR4 exhibits high relaxivities (r 1 = 30.9 mM-1 s-1, r 2 = 43.2 mM-1 s-1, 1.5 T; r 1 = 23.5 mM-1 s-1, r 2 = 98.6 mM-1 s-1, 7.0 T), strong CXCR4 binding (K d = 1.10 ± 0.18 µM), CXCR4 molecular imaging capability in metastatic and intrahepatic xenotransplantation UM mouse models. ProCA32.CXCR4 enables detecting UM liver metastases as small as 0.1 mm3. Further development of the CXCR4-targeted imaging agent should have strong translation potential for early detection, surveillance, and treatment stratification of liver metastases patients.


Assuntos
Biomarcadores , Meios de Contraste , Neoplasias Hepáticas/diagnóstico por imagem , Neoplasias Hepáticas/metabolismo , Imagem por Ressonância Magnética , Imagem Molecular , Receptores CXCR4/metabolismo , Animais , Meios de Contraste/química , Modelos Animais de Doenças , Detecção Precoce de Câncer , Expressão Gênica , Humanos , Neoplasias Hepáticas/patologia , Imagem por Ressonância Magnética/métodos , Camundongos , Modelos Moleculares , Metástase Neoplásica , Ligação Proteica , Curva ROC , Receptores CXCR4/química , Receptores CXCR4/genética , Reprodutibilidade dos Testes , Relação Estrutura-Atividade
4.
Nat Commun ; 10(1): 4777, 2019 10 29.
Artigo em Inglês | MEDLINE | ID: mdl-31664017

RESUMO

Early diagnosis and noninvasive detection of liver fibrosis and its heterogeneity remain as major unmet medical needs for stopping further disease progression toward severe clinical consequences. Here we report a collagen type I targeting protein-based contrast agent (ProCA32.collagen1) with strong collagen I affinity. ProCA32.collagen1 possesses high relaxivities per particle (r1 and r2) at both 1.4 and 7.0 T, which enables the robust detection of early-stage (Ishak stage 3 of 6) liver fibrosis and nonalcoholic steatohepatitis (Ishak stage 1 of 6 or 1 A Mild) in animal models via dual contrast modes. ProCA32.collagen1 also demonstrates vasculature changes associated with intrahepatic angiogenesis and portal hypertension during late-stage fibrosis, and heterogeneity via serial molecular imaging. ProCA32.collagen1 mitigates metal toxicity due to lower dosage and strong resistance to transmetallation and unprecedented metal selectivity for Gd3+ over physiological metal ions with strong translational potential in facilitating effective treatment to halt further chronic liver disease progression.


Assuntos
Meios de Contraste/química , Gadolínio/química , Hipertensão Portal/diagnóstico por imagem , Fígado/diagnóstico por imagem , Imagem por Ressonância Magnética/métodos , Doença Crônica , Diagnóstico Precoce , Humanos
5.
Biomaterials ; 224: 119478, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31542517

RESUMO

The Liver is the most common organ for metastasis for various cancers, including uveal melanoma, the most common primary intraocular tumor. Uveal melanoma metastasizes to the liver in ~90% of patients, and results in death in almost all cases due to late detection and lack of effective treatment. There is a pressing unmet medical need to develop MRI contrast agents and imaging methodologies with desired sensitivity and specificity to overcome the high heterogeneous background and in vivo properties as well as reduced toxicity. Herein, we report the development of a collagen targeting protein contrast agent (ProCA32.collagen1), since collagen is a diagnostic biomarker and therapeutic target for many types of primary and metastatic cancers and the tumor microenvironment. In addition to a strong affinity to collagen I, ProCA32.collagen1 possesses high relaxivities (r1 and r2 are 68.0 ±â€¯0.25 and 100.0 ±â€¯0.32 mM-1 s-1 at 1.4 T, respectively, and 42.6 ±â€¯1.0 and 217 ±â€¯2.4 mM-1s-1 at 7.0 T per particle). ProCA32.collagen1 also has strong serum stability against degradation, resistance to transmetallation, and 102 and 1013-fold higher metal selectivity for Gd3+ over Ca2+ and Zn2+, respectively, compared to clinical contrast agents. ProCA32.collagen1 does not exhibit any cell toxicity for various cell lines. Sensitive detection of liver lesions in animal models can be achieved using multiple imaging methodologies, taking advantage of the dual relaxation property of ProCA32.collagen1. ProCA32.collagen1 enables sensitive and early stage detection of hepatic micrometastasis as small as 0.144 mm2 and two different tumor growth patterns. Further development of ProCA32.collagen1 has the potential to greatly facilitate non-invasive, early detection and staging of primary and metastatic liver cancers, and devising effective treatments.


Assuntos
Colágeno/química , Meios de Contraste/química , Neoplasias Hepáticas/diagnóstico , Neoplasias Hepáticas/secundário , Imagem por Ressonância Magnética , Animais , Linhagem Celular , Sobrevivência Celular , Endocitose , Feminino , Humanos , Fígado/patologia , Camundongos Endogâmicos C57BL , Distribuição Tecidual
7.
Methods Mol Biol ; 1929: 111-125, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30710270

RESUMO

Early diagnosis, noninvasive detection, and staging of various diseases, remain one of the major clinical barriers to effective medical treatment and prevention of disease progression toward major clinical consequences. Molecular imaging technologies play an indispensable role in the clinical field in overcoming these major barriers. The increasing application of imaging techniques and agents in early detection of different diseases such as cancer has resulted in improved treatment response and clinical patient management. In this chapter we will first introduce criteria for the design and engineering of calcium-binding protein (CaBP) parvalbumin as a protein Gd-MRI contrast agent (ProCA) with unprecedented metal selectivity for Gd3+ over physiological metal ions. We will then discuss the further development of targeted MRI contrast agent for molecular imaging of PSMA biomarker for early detection of prostate cancer.


Assuntos
Meios de Contraste/síntese química , Gadolínio/química , Calicreínas/metabolismo , Parvalbuminas/química , Antígeno Prostático Específico/metabolismo , Neoplasias da Próstata/diagnóstico por imagem , Engenharia de Proteínas/métodos , Animais , Cálcio/metabolismo , Linhagem Celular Tumoral , Meios de Contraste/química , Meios de Contraste/farmacologia , Detecção Precoce de Câncer , Humanos , Imagem por Ressonância Magnética/métodos , Masculino , Camundongos , Modelos Moleculares , Conformação Molecular , Imagem Molecular/métodos , Transplante de Neoplasias , Neoplasias da Próstata/metabolismo
8.
Biochem J ; 474(24): 4035-4051, 2017 11 27.
Artigo em Inglês | MEDLINE | ID: mdl-28963343

RESUMO

Calmodulin (CaM) is an intracellular Ca2+ transducer involved in numerous activities in a broad Ca2+ signaling network. Previous studies have suggested that the Ca2+/CaM complex may participate in gap junction regulation via interaction with putative CaM-binding motifs in connexins; however, evidence of direct interactions between CaM and connexins has remained elusive to date due to challenges related to the study of membrane proteins. Here, we report the first direct interaction of CaM with Cx45 (connexin45) of γ-family in living cells under physiological conditions by monitoring bioluminescence resonance energy transfer. The interaction between CaM and Cx45 in cells is strongly dependent on intracellular Ca2+ concentration and can be blocked by the CaM inhibitor, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride (W7). We further reveal a CaM-binding site at the cytosolic loop (residues 164-186) of Cx45 using a peptide model. The strong binding (Kd ∼ 5 nM) observed between CaM and Cx45 peptide, monitored by fluorescence-labeled CaM, is found to be Ca2+-dependent. Furthermore, high-resolution nuclear magnetic resonance spectroscopy reveals that CaM and Cx45 peptide binding leads to global chemical shift changes of 15N-labeled CaM, but does not alter the size of the structure. Observations involving both N- and C-domains of CaM to interact with the Cx45 peptide differ from the embraced interaction with Cx50 from another connexin family. Such interaction further increases Ca2+ sensitivity of CaM, especially at the N-terminal domain. Results of the present study suggest that both helicity and the interaction mode of the cytosolic loop are likely to contribute to CaM's modulation of connexins.


Assuntos
Técnicas de Transferência de Energia por Ressonância de Bioluminescência/métodos , Cálcio/metabolismo , Calmodulina/metabolismo , Conexinas/metabolismo , Sequência de Aminoácidos , Sítios de Ligação , Calmodulina/química , Conexinas/química , Transferência de Energia , Células HEK293 , Células HeLa , Humanos , Cinética , Ligação Proteica , Conformação Proteica , Homologia de Sequência , Transdução de Sinais
9.
Nanoscale ; 8(25): 12668-82, 2016 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-26961235

RESUMO

Prostate-specific membrane antigen (PSMA) is one of the most specific cell surface markers for prostate cancer diagnosis and targeted treatment. However, achieving molecular imaging using non-invasive MRI with high resolution has yet to be achieved due to the lack of contrast agents with significantly improved relaxivity for sensitivity, targeting capabilities and metal selectivity. We have previously reported our creation of a novel class of protein Gd(3+) contrast agents, ProCA32, which displayed significantly improved relaxivity while exhibiting strong Gd(3+) binding selectivity over physiological metal ions. In this study, we report our effort in further developing biomarker-targeted protein MRI contrast agents for molecular imaging of PSMA. Among three PSMA targeted contrast agents engineered with addition of different molecular recognition sequences, ProCA32.PSMA exhibits a binding affinity of 1.1 ± 0.1 µM for PSMA while the metal binding affinity is maintained at 0.9 ± 0.1 × 10(-22) M. In addition, ProCA32.PSMA exhibits r1 of 27.6 mM(-1) s(-1) and r2 of 37.9 mM(-1) s(-1) per Gd (55.2 and 75.8 mM(-1) s(-1) per molecule r1 and r2, respectively) at 1.4 T. At 7 T, ProCA32.PSMA also has r2 of 94.0 mM(-1) s(-1) per Gd (188.0 mM(-1) s(-1) per molecule) and r1 of 18.6 mM(-1) s(-1) per Gd (37.2 mM(-1) s(-1) per molecule). This contrast capability enables the first MRI enhancement dependent on PSMA expression levels in tumor bearing mice using both T1 and T2-weighted MRI at 7 T. Further development of these PSMA-targeted contrast agents are expected to be used for the precision imaging of prostate cancer at an early stage and to monitor disease progression and staging, as well as determine the effect of therapeutic treatment by non-invasive evaluation of the PSMA level using MRI.


Assuntos
Antígenos de Superfície/análise , Meios de Contraste , Glutamato Carboxipeptidase II/análise , Imagem por Ressonância Magnética , Imagem Molecular , Neoplasias Experimentais/diagnóstico por imagem , Neoplasias da Próstata/diagnóstico por imagem , Animais , Linhagem Celular Tumoral , Gadolínio , Humanos , Masculino , Camundongos , Camundongos Nus
10.
Sci Rep ; 5: 16214, 2015 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-26577829

RESUMO

Gastrin-releasing peptide receptor (GRPR) is differentially expressed on the surfaces of various diseased cells, including prostate and lung cancer. However, monitoring temporal and spatial expression of GRPR in vivo by clinical MRI is severely hampered by the lack of contrast agents with high relaxivity, targeting capability and tumor penetration. Here, we report the development of a GRPR-targeted MRI contrast agent by grafting the GRPR targeting moiety into a scaffold protein with a designed Gd(3+) binding site (ProCA1.GRPR). In addition to its strong binding affinity for GRPR (Kd = 2.7 nM), ProCA1.GRPR has high relaxivity (r1 = 42.0 mM(-1)s(-1) at 1.5 T and 25 °C) and strong Gd(3+) selectivity over physiological metal ions. ProCA1.GRPR enables in vivo detection of GRPR expression and spatial distribution in both PC3 and H441 tumors in mice using MRI. ProCA1.GRPR is expected to have important preclinical and clinical implications for the early detection of cancer and for monitoring treatment effects.


Assuntos
Meios de Contraste , Imagem por Ressonância Magnética , Imagem Molecular , Neoplasias/diagnóstico , Neoplasias/metabolismo , Receptores da Bombesina/metabolismo , Animais , Sítios de Ligação , Biomarcadores , Linhagem Celular Tumoral , Meios de Contraste/química , Meios de Contraste/metabolismo , Meios de Contraste/farmacocinética , Modelos Animais de Doenças , Expressão Gênica , Xenoenxertos , Humanos , Ligantes , Imagem por Ressonância Magnética/métodos , Camundongos , Modelos Moleculares , Conformação Molecular , Imagem Molecular/métodos , Neoplasias/genética , Ligação Proteica , Ratos , Receptores da Bombesina/química , Receptores da Bombesina/genética , Distribuição Tecidual
11.
Proc Natl Acad Sci U S A ; 112(21): 6607-12, 2015 May 26.
Artigo em Inglês | MEDLINE | ID: mdl-25971726

RESUMO

With available MRI techniques, primary and metastatic liver cancers that are associated with high mortality rates and poor treatment responses are only diagnosed at late stages, due to the lack of highly sensitive contrast agents without Gd(3+) toxicity. We have developed a protein contrast agent (ProCA32) that exhibits high stability for Gd(3+) and a 10(11)-fold greater selectivity for Gd(3+) over Zn(2+) compared with existing contrast agents. ProCA32, modified from parvalbumin, possesses high relaxivities (r1/r2: 66.8 mmol(-1)⋅s(-1)/89.2 mmol(-1)⋅s(-1) per particle). Using T1- and T2-weighted, as well as T2/T1 ratio imaging, we have achieved, for the first time (to our knowledge), robust MRI detection of early liver metastases as small as ∼0.24 mm in diameter, much smaller than the current detection limit of 10-20 mm. Furthermore, ProCA32 exhibits appropriate in vivo preference for liver sinusoidal spaces and pharmacokinetics for high-quality imaging. ProCA32 will be invaluable for noninvasive early detection of primary and metastatic liver cancers as well as for monitoring treatment and guiding therapeutic interventions, including drug delivery.


Assuntos
Meios de Contraste , Neoplasias Hepáticas Experimentais/diagnóstico , Neoplasias Hepáticas Experimentais/metabolismo , Imagem por Ressonância Magnética/métodos , Melanoma Experimental/diagnóstico , Melanoma Experimental/metabolismo , Parvalbuminas , Animais , Linhagem Celular Tumoral , Meios de Contraste/química , Meios de Contraste/farmacocinética , Feminino , Gadolínio , Limite de Detecção , Neoplasias Hepáticas Experimentais/secundário , Camundongos , Camundongos Endogâmicos C57BL , Modelos Moleculares , Parvalbuminas/química , Parvalbuminas/farmacocinética , Engenharia de Proteínas , Estabilidade Proteica , Proteínas Recombinantes/química , Proteínas Recombinantes/farmacocinética
12.
Food Chem ; 173: 1207-12, 2015 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-25466145

RESUMO

In this paper, we have introduced nanoporous carbon modified with mercapto groups as a new solid-phase method for extraction of cadmium(II) and copper(II) ions. The modified nanoporous carbon sorbent was characterised by thermogravimetric analysis, differential thermal analysis, transmission electron microscopy, Fourier transform infrared spectrometry, X-ray diffraction, and nitrogen adsorption surface area (BET) measurements. Effects of pH value, flow rates, type, concentration and volume of the eluent, breakthrough volume, and effect of other ions were studied. The experimental results show that simultaneous trace cadmium(II) and copper(II) ions can be quantitatively preconcentrated at pH 6.0 with recoveries >97%. Under optimised conditions, limits of detection are 0.04 and 0.09 ng mL(-1) for the ions of cadmium and copper respectively, and the precision of the method for analysis of cadmium and copper ions (5.0 µg of each target ions, N=8) are 2.4% and 2.1%, respectively. The obtained capacities of mercapto-nanoporous carbon were found to be 145 and 95 mg g(-1) for cadmium and copper ions, respectively. The accuracy of the proposed procedure was verified by analysing standard reference material. Finally, the introduced sorbent was successfully applied for trace determination of cadmium and copper ions in food samples.


Assuntos
Cádmio/análise , Carbono/química , Cobre/análise , Análise de Alimentos/métodos , Adsorção , Carboidratos/química , Concentração de Íons de Hidrogênio , Limite de Detecção , Microscopia Eletrônica de Transmissão , Porosidade , Extração em Fase Sólida , Espectrofotometria Atômica , Difração de Raios X
13.
Food Chem ; 158: 14-9, 2014 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-24731308

RESUMO

Due to importance of trace analysis of lead and copper ions because of their toxicity, in this paper, for the first time a unique tetragonal star-like morphology of polyaniline was applied as a efficient solid phase for selective trace separation of copper and lead at optimum experimental conditions in shrimp, fish and water samples. Due to the unique star like nanostructure of synthesized sorbent, the tendency of the sorbent toward selective extraction of lead and copper ion in the optimised pH is very interesting. The prepared polymeric resin displayed good figures of merits with analytical calibration curve ranging from 1 to 120 µg L(-1) for copper and 2 to 100 µg L(-1) for lead ions with limits of detection of 0.4 µg L(-1) for copper and 0.9 µg L(-1) for lead, adsorption capacities of 84 and 110 mg g(-1) for copper and lead ions, respectively, extraction efficiency of greater than 96%, and relative standard deviation (RSD) of less than 4% for eight separate column experiments in determination of 5.0 µg of lead and copper. The obtained data for adsorption capacity of the sorbent shows the high tendency of the sorbent toward the mentioned ions in this nanostructure form. Finally, this sorbent can be used as a simple, rapid, reliable, selective and sensitive method for determination of trace levels of Cu(II) and Pb(II).


Assuntos
Compostos de Anilina/química , Nanoestruturas/química , Alimentos Marinhos/análise , Frutos do Mar/análise , Animais , Peixes , Extração em Fase Sólida/métodos , Espectrofotometria Atômica/métodos
14.
FEBS Lett ; 588(8): 1430-8, 2014 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-24440348

RESUMO

Intracellular Ca(2+) activated calmodulin (CaM) inhibits gap junction channels in the low nanomolar to high micromolar range of [Ca(2+)]i. This regulation plays an essential role in numerous cellular processes that include hearing, lens transparency, and synchronized contractions of the heart. Previous studies have indicated that gap junction mediated cell-to-cell communication was inhibited by CaM antagonists. More recent evidence indicates a direct role of CaM in regulating several members of the connexin family. Since the intracellular loop and carboxyl termini of connexins are largely "invisible" in electron microscopy and X-ray crystallographic structures due to disorder in these domains, peptide models encompassing the putative CaM binding sites of several intracellular domains of connexins have been used to identify the Ca(2+)-dependent CaM binding sites of these proteins. This approach has been used to determine the CaM binding affinities of peptides derived from a number of different connexin-subfamilies.


Assuntos
Calmodulina/metabolismo , Conexinas/metabolismo , Sequência de Aminoácidos , Animais , Sítios de Ligação , Cálcio/metabolismo , Conexinas/química , Conexinas/genética , Humanos , Simulação de Dinâmica Molecular , Dados de Sequência Molecular , Ligação Proteica
15.
J Chromatogr A ; 1308: 25-31, 2013 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-23958696

RESUMO

A simple, rapid, and efficient method, based on surfactant assisted dispersive liquid-liquid microextraction (SA-DLLME), followed by high performance liquid chromatography (HPLC) has been developed for simultaneous preconcentration and trace detection of zonisamide and carbamazepine in biological samples. A conventional cationic surfactant called cethyltrimethyl ammonium bromide (CTAB) was used as a disperser agent in the proposed approach. 1.5 mL of CTAB (0.45 mmol L(-1)) (disperser solvent) containing 50.0 µL of 1-octanol (extraction solvent) was injected rapidly into the 7.0 mL of water or diluted plasma or urine. A cloudy solution (water, 1-octanol, and CTAB) was formed in the test tube. After formation of cloudy solution, the mixture was centrifuged and 20 µL of collected phase was injected into HPLC for subsequent analysis. Some parameters such as the type and volume of the extraction solvent, the type and concentration of surfactant, pH, ionic strength and centrifugation time were evaluated and optimized. Under optimum extraction conditions, the limits of detections (LODs) were 2.1 and 1.5 µg L(-1) (based on 3Sb/m) for urine samples, and 2.3 and 1.6 µg L(-1) for plasma samples. Linear dynamic range of 5-300 and 5-200 µg L(-1) were obtained for zonisamide and carbamazepine in all samples. Finally, the applicability of the proposed method was evaluated by extraction and determination of the drugs in urine and plasma samples.


Assuntos
Carbamazepina/isolamento & purificação , Isoxazóis/isolamento & purificação , Microextração em Fase Líquida/métodos , Tensoativos/química , 1-Octanol/química , Carbamazepina/sangue , Carbamazepina/urina , Cetrimônio , Compostos de Cetrimônio/química , Cromatografia Líquida de Alta Pressão/métodos , Dissonias , Humanos , Isoxazóis/sangue , Isoxazóis/urina , Modelos Lineares , Concentração Osmolar , Reprodutibilidade dos Testes , Hidróxido de Sódio/química , Zonisamida
16.
Food Chem ; 141(1): 48-53, 2013 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-23768325

RESUMO

A novel sorbent for separation of cadmium ions was prepared by functionalizing multiwall carbon nanotubes with diphenylcarbazide and underutilised to develop a solid-phase extraction method to separate and concentrate trace amounts of cadmium ions from some real samples by flame atomic absorption spectrophotometry measurements. The optimum experimental conditions such as pH, flow rates, type and the smallest amount of eluent for elution of cadmium ions, break through volume and effect of coexisting ions on the separation and determination of cadmium ions were evaluated. In the proposed method, the extraction efficiency for cadmium ions were greater than 97% and limit of detection (LOD) was 0.05 ng mL(-1). The preconcentration factor was 360 for cadmium and the relative standard deviation (RSD) of the method was 2.4%. The adsorption capacity of the modified MWCNT was 86 mg g(-1) for cadmium ions. Validation of the outlined method was performed by analysing certified reference material soil (NCS DC 73323). The practical applicability of the developed sorbent was examined in some real samples.


Assuntos
Cádmio/isolamento & purificação , Nanotubos de Carbono/química , Oryza/química , Extração em Fase Sólida/métodos , Verduras/química , Poluentes Químicos da Água/isolamento & purificação , Adsorção , Cádmio/análise , Difenilcarbazida/química , Contaminação de Alimentos/análise , Limite de Detecção , Extração em Fase Sólida/instrumentação , Poluentes Químicos da Água/análise
17.
J Chromatogr A ; 1300: 227-35, 2013 Jul 26.
Artigo em Inglês | MEDLINE | ID: mdl-23688683

RESUMO

Combination of different extraction methods is an interesting and debatable work in the field of sample preparation. In the current study, for the first time, solid phase extraction combined with electro membrane extraction (SPE-EME) was developed for ultra-preconcentration and determination of chlorophenoxy acid herbicides in environmental samples using capillary electrophoresis (CE). In the mentioned method, first, a 100mL of chlorophenoxy acid herbicides (2-methyl-4-chlorophenoxyacetic acid (MCPA), 2-(2,4-dichlorophenoxy) propanoic acid (2,4-DP) and 2-(4-chloro-2-methylphenoxy) propanoic acid (MCPP)) was passed through a column of graphene oxide as a solid phase, and then the adsorbed herbicides were eluted by 4.0mL of 8% acetic acid (HOAC) in methanol. Then, the elution solvent was evaporated and the herbicides residue was dissolved in 4.0mL of double distilled water (pH 9.0). Afterwards, the herbicides in 4.0mL of the aqueous solution were transferred to an EME glass vial. In the EME step, the herbicides were extracted from the sample solution into the basic acceptor solution (pH 13.0) under electrical potential, which was held inside the lumen of the fiber with 1-octanol as the supported liquid membrane (SLM). Under the optimized conditions, high enrichment factors were obtained in the range of 1950-2000. The limits of quantification (LOQs) and method detection limits (MDLs) were obtained in the range of 1.0-1.5 and 0.3-0.5ngmL(-1), respectively. Finally, the performance of the present method was evaluated for extraction and determination of chlorophenoxy acid herbicides in environmental samples.


Assuntos
Grafite/química , Herbicidas/isolamento & purificação , Fenoxiacetatos/isolamento & purificação , Extração em Fase Sólida/métodos , Poluentes Químicos da Água/isolamento & purificação , 1-Octanol/química , Eletroforese Capilar , Herbicidas/análise , Herbicidas/química , Concentração de Íons de Hidrogênio , Membranas Artificiais , Fenoxiacetatos/análise , Fenoxiacetatos/química , Reprodutibilidade dos Testes , Projetos de Pesquisa , Rios/química , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/química
18.
Food Chem ; 138(2-3): 2050-6, 2013 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-23411342

RESUMO

This paper describes the preparation of new Pb(II)-imprinted polymeric particles using 2-vinylpyridine as a functional monomer, ethylene glycol dimethacrylate as the cross-linker, 2,2'- azobisisobutyronitrile as the initiator, diphenylcarbazone as the ligand, acetonitril as the solvent, and Pb(NO(3))(2) as the template ion, through bulk polymerisation technique. The imprinted lead ions were removed from the polymeric matrix using 5 mL of HCl (2 mol.L(-1)) as the eluting solvent. The lead ion concentration was determined by flame atomic absorption spectrometry. Optimum pH for maximum sorption was obtained at 6.0. Sorption and desorption of Pb(II) ions on the IIP particles were quite fast and achieved fully over 5 min. In the proposed method, the maximum sorbent capacity of the ion-imprinted polymer was calculated to be 75.4 mg g(-1). The preconcentration factor, relative standard deviation, and limit of detection of the method were found to be 245, 2.1%, and 0.42 ng mL(-1), respectively. The prepared ion-imprinted polymer particles have an increased selectivity toward Pb(II) ions over a range of competing metal ions with the same charge and similar ionic radius. This ion-imprinted polymer is an efficient solid phase for extraction and preconcentration of lead ions in complex matrixes. For proving that the proposed method is reliable, a wide range of food samples with different and complex matrixes was used.


Assuntos
Contaminação de Alimentos/análise , Chumbo/isolamento & purificação , Nanoestruturas/química , Oryza/química , Polímeros/química , Alimentos Marinhos/análise , Extração em Fase Sólida/métodos , Verduras/química , Adsorção , Animais , Peixes , Chumbo/química , Impressão Molecular , Polímeros/síntese química , Extração em Fase Sólida/instrumentação , Espectrofotometria Atômica
19.
Talanta ; 99: 132-9, 2012 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-22967532

RESUMO

This paper describes the synthesis and application of novel magnetic metal-organic framework (MOF) [(Fe(3)O(4)-Pyridine)/Cu(3)(BTC)(2)] for preconcentration of Pd(II) and its determination by flame atomic absorption spectrometry (FAAS). A Box-Behnken design was used to find the optimum conditions for the preconcentration procedure through response surface methodology. Three variables including amount of magnetic MOF, extraction time, and pH of extraction were selected as factors for adsorption step, and in desorption step, four parameters including type, volume, and concentration of eluent, and desorption time were selected in the optimization study. These values were 30 mg, 6 min, 6.9, K(2)SO(4)+NaOH, 6 mL, 9.5 (w/v %)+0.01 mol L(-1), 15.5 min, for amount of MOF, extraction time, pH of extraction, type, volume, and concentration of the eluent, and desorption time, respectively. The preconcentration factor (PF), relative standard deviation (RSD), limit of detection (LOD), and adsorption capacity of the method were found to be 208, 2.1%, 0.37 ng mL(-1), and 105.1 mg g(-1), respectively. It was found that the magnetic MOF has more capacity compared to Fe(3)O(4)-Py. Finally, the magnetic MOF was successfully applied for rapid extraction of trace amounts of Pd (II) ions in fish, sediment, soil, and water samples.

20.
Talanta ; 89: 455-61, 2012 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-22284517

RESUMO

A novel sorbent for simultaneous separation of cadmium and copper was prepared by functionalizing SBA-15 nanoporous silica with diphenylcarbazide. A solid-phase extraction method using the above sorbent has been developed to separate and concentrate trace amount of cadmium and copper ions from environmental samples by flame atomic absorption spectrophotometry measurements. The optimum experimental conditions such as pH, flow rates, type and the smallest amount of eluent for elution of cadmium and copper ions, break through volume and effect of coexisting ions on the separation and determination of cadmium and copper ions were evaluated. The extraction efficiency for cadmium and copper ions were greater than 98% and limit of detection (LOD) was 0.15 and 0.45 ng mL(-1) for cadmium and copper, respectively. The preconcentration factor was 294 and 291 for cadmium and copper, respectively, and the relative standard deviation (RSD) of the method was <4% for 10 separate column experiments for the determination of 5.0 µg cadmium and copper ions. The adsorption capacity of the nanoporous silica was 198 mg g(-1) for cadmium and 105 mg g(-1) for copper on functionalized SBA-15 nanoporous silica. Validation of the outlined method was performed by analyzing certified reference materials (Soil (NCS DC 73323) and ore polymetallic gold Zidarovo-PMZrZ (206 BG 326)). The practical applicability of the developed sorbent was examined using real samples such as sea water, fish and sediment samples.


Assuntos
Cádmio/análise , Cobre/análise , Difenilcarbazida/química , Poluentes Ambientais/análise , Água do Mar/química , Dióxido de Silício/química , Solo/química , Adsorção , Animais , Monitoramento Ambiental , Peixes/metabolismo , Sedimentos Geológicos/química , Concentração de Íons de Hidrogênio , Limite de Detecção , Porosidade , Extração em Fase Sólida , Espectrofotometria Atômica
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