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1.
ACS Omega ; 4(8): 13349-13359, 2019 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-31460463

RESUMO

Clay/polymer nanocomposites (CPNs) are polymers incorporating refined clay particles that are frequently functionalized with quaternary ammonium cations (QACs) as dispersion aids. There is interest in commercializing CPNs for food contact applications because they have improved strength and barrier properties, but there are few studies on the potential for QACs in CPNs to transfer to foods under conditions of intended use. In this study, we manufactured low-density poly(ethylene) (LDPE)-based CPNs and assessed whether QACs can migrate into several food simulants under accelerated storage conditions. QACs were found to migrate to a fatty food simulant (ethanol) at levels of ∼1.1 µg mg-1 CPN mass after 10 days at 40 °C, constituting about 4% total migration (proportion of the initial QAC content in the CPN that migrated to the simulant). QAC migration into ethanol was ∼16× higher from LDPE containing approximately the same concentration of QACs but no clay, suggesting that most QACs in the CPN are tightly bound to clay particles and are immobile. Negligible QACs were found to migrate into aqueous, alcoholic, or acidic simulants from CPNs, and the amount of migrated QACs was also found to scale with the temperature and the initial clay concentration. The migration data were compared to a theoretical diffusion model, and it was found that the diffusion constant for QACs in the CPN was several orders of magnitude slower than predicted, which we attributed to the potential for QACs to migrate as dimers or other aggregates rather than as individual ions. Nevertheless, the use of the migration model resulted in a conservative estimate of the mass transfer of QAC from the CPN test specimens.

2.
Anal Chim Acta ; 1048: 75-84, 2019 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-30598160

RESUMO

Multiplex detection of ultra-low abundant tumor markers is extremely important for early diagnosis and therapy evaluation. Herein, an ultrasensitive multiplex immunoassay was developed by combination of rolling circle amplification (RCA) and suspension bead array (SBA) technology. Based on a conventional sandwich-type immunoreaction on beads, the detection antibodies were conjugated with DNA primers, so RCA could be implemented to generate long-stranded DNA with abundant repeated sequences allowing for hybridization with fluorochrome-labeled oligonucleotide probes. Thus the fluorescence signal of immunocomplexes on the encoded beads can be greatly enhanced. Using the as-developed immuno-RCA suspension bead array (iRCA-SBA), simultaneous analysis of multiple tumor markers was achieved with the limits of detection of 3.1 pg/mL (∼0.1 pM) for prostate specific antigen (PSA), 9.1 pg/mL (∼50 fM) for carcinoembryonic antigen (CEA), and 0.66 pg/mL (∼9 fM) for α-fetoprotein (AFP), which are two to three orders of magnitude lower than those obtained by the conventional SBA method. The dynamic range were 4.5, 4.7, and 5.5 orders of magnitude for PSA, CEA, and AFP, respectively. Tests on clinical serum samples demonstrate that the tumor marker concentrations measured by the newly developed iRCA-SBA assay agreed well with those obtained by the conventional SBA method. These results indicate that the iRCA-SBA assay significantly increased the detection sensitivity and dynamic range without sacrificing the reliability and accuracy of conventional SBA. Upon the integration with iRCA, SBA could find more applications in the detection of low abundance protein biomarkers for early diagnosis of cancer and other diseases.


Assuntos
Biomarcadores Tumorais/sangue , Antígeno Carcinoembrionário/sangue , Imunoensaio/métodos , Calicreínas/sangue , Técnicas de Amplificação de Ácido Nucleico/métodos , Antígeno Prostático Específico/sangue , alfa-Fetoproteínas/análise , Anticorpos Imobilizados/imunologia , Anticorpos Monoclonais/imunologia , Biomarcadores Tumorais/imunologia , Antígeno Carcinoembrionário/imunologia , Sondas de DNA/genética , DNA de Cadeia Simples/genética , Citometria de Fluxo/métodos , Humanos , Calicreínas/imunologia , Limite de Detecção , Masculino , Hibridização de Ácido Nucleico , Antígeno Prostático Específico/imunologia , Reprodutibilidade dos Testes , alfa-Fetoproteínas/imunologia
3.
J AOAC Int ; 101(6): 1873-1880, 2018 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-29852893

RESUMO

Background: A flow-injection MS (FI/MS) method was evaluated for the quantitation of quaternary ammonium cations (QACs) in simple food simulants. Methods: The calibration standard was dimethyldioctadecyl ammonium ion (C18-C18), and the internal standard was benzyldimethylhexadecyl (BDMHD) ammonium ion. Calibration standards based on the C18-C18 ion were prepared in ethanol with a range of 5 to 500 ppb and contained 100 ppb BDMHD. The mobile phase was 90 + 10 (v/v) acetonitrile-5 mM aqueous ammonium acetate and flowed directly into an electrospray source of the mass spectrometer. Detection was accomplished by single ion recording (SIR) in positive mode. Results: Calibration curves were linear with coefficients of determination above 0.995, and the LOQ was 5 ppb. Recoveries of four QACs derived from Arquad 2HT-75, a commercially available surfactant, were measured in common food simulants: ethanol, water, 10% (v/v) ethanol in water, and 3% (v/v) aqueous acetic acid. A solvent exchange procedure was employed for the three aqueous solvents, which included complete evaporation of the sample followed by reconstitution in ethanol prior to injection. The solvent exchange method minimized losses because of QAC adsorption on glass surfaces. Recoveries ranged from 74.4 ± 4.0 to 106.7 ± 6.6% for the two most abundant Arquad 2HT-75 component cations, dimethyldioctadecyl ammonium and dimethyloctadecyl-hexadecyl ammonium. Conclusions: This method is suitable to quantify trace levels of QACs in food simulants as part of exposure evaluations related to their use in emerging food contact materials.


Assuntos
Espectrometria de Massas/métodos , Compostos de Amônio Quaternário/análise , Ácido Acético/química , Calibragem , Etanol/química , Água/química
4.
Dalton Trans ; 45(6): 2417-21, 2016 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-26782111

RESUMO

The first Krebs-type tungstoantimonate containing ferrous ions Na2H4[C3H5N2]4[Sb2W20Fe2(II)(H2O)6O70]·12H2O (1) was prepared by a new route of synthesis under mild reaction conditions. The facile synthesis route represented a favourable tactic for the successful synthesis of Fe(II)-based polyoxometalate. Its applications in both catalytic Fenton reaction and electrochemical sensing of ascorbic acid were also investigated primarily.


Assuntos
Ácido Ascórbico/análise , Complexos de Coordenação/síntese química , Técnicas Eletroquímicas , Compostos Ferrosos/química , Peróxido de Hidrogênio/química , Ferro/química , Antimônio/química , Catálise , Complexos de Coordenação/química , Cristalografia por Raios X , Conformação Molecular , Tungstênio/química , Compostos de Tungstênio/síntese química , Compostos de Tungstênio/química
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