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Abstract: A highly facile and feasible strategy on the fabrication of advanced intrinsic peroxidase mimetics based on Mn2+ doped mixed ferrite (MnII x FeII 1−x FeIII 2O4) nanoparticles was demonstrated for the quantitative and sensitive detection of mouse IgG (as a model analyte). Mn2+ doped Fe1−x Mn x Fe2O4 nanoparticles were synthesized using varying ratios of Mn2+:Fe2+ ions and characterized by the well known complementary techniques. The increase of Mn2+ proportion had remarkably enhanced the peroxidase activity and magnetism. The catalytic activity of mixed ferrites was found to follow Michaelis–Menten kinetics and was noticeably higher than native Fe3O4. The calculated K m and K cat exhibited strong affinity with substrates which were remarkably higher than similar sized native magnetite nanoparticles and horseradish peroxidase (HRP). These findings stimulated us to develop carboxyl modified Fe1−x Mn x Fe2O4 nanoparticles using phosphonomethyl immunodiacetic acid (PMIDA) to engineer PMIDA–Fe1−x Mn x Fe2O4 fabricated enzyme linked immunosorbent assay (ELISA). Results of both PMIDA–Fe1−x Mn x Fe2O4 linked ELISA revealed that the enhancements in absorbance during the catalysis of enzyme substrate were linearly proportional to the concentration of mouse IgG within the range between 0.1μg/ml and 2.5μg/ml. Further, this detection was ten times lower than previous reports and the detection limit of mouse IgG was 0.1μg/ml. The advantages of our fabricated artificial peroxidase mimetics are combined of low cost, easy to prepare, better stability and tunable catalytic activity. Moreover, this method provides a new horizon for the development of promising analytical tools in the application of biocatalysis, bioassays, and bioseparation. [Copyright &y& Elsevier]

In this contribution, we demonstrate a rapid, sensitive, specific and efficient method for detection of Staphylococcus aureus(S. aureus) as the model analyte at ultra-low concentrations using antibody labelled multifunctional gold-magnetite nanocomposites. A simple and efficient approach was adopted to construct diverse multifunctional gold magnetite nanostructures using 2,2′-(ethylenedioxy)-bis-(ethylamine) (EDBE) as a linker. The gold magnetite nanostructures were fabricated by iterative deposition of gold nanoparticles on the previously decorated gold-seed stabilized magnetite nanoparticles. These nanocomposites were further bioconjugated with an anti-α-toxin antibody with the aim to generate biorecognition probes that can specifically allow ultrasensitive detection as well as removal of S. aureusat ultra-low concentrations. The fluorescence and optical images of bacterial cells after interaction with our bioprobes showed that the pathogenic bacteria could be first immunomagnetically captured, detected and removed from S. aureuscell suspension in 30 min within the range of 102–107CFU mL−1of bacterial concentration. The detection limit achieved of S. aureuswas 102CFU mL−1. The specificity of the detection of S. aureuswas also verified using Escherichia colias the model analyte using confocal microscopy. The combined functionalities of such antibody-targeted nanoprobes can be considered as a new tool box for the targeted, specific and sensitive detection of specific organisms (S. aureus) within 30 min. [ABSTRACT FROM AUTHOR]

A highly facile and feasible strategy on the fabrication of advanced intrinsic peroxidase mimetics based on Mn(2+) doped mixed ferrite (Mn(II)(x)Fe(II)(1-x)Fe(III)(2)O(4)) nanoparticles was demonstrated for the quantitative and sensitive detection of mouse IgG (as a model analyte). Mn(2+) doped Fe(1-x)Mn(x)Fe(2)O(4) nanoparticles were synthesized using varying ratios of Mn(2+):Fe(2+) ions and characterized by the well known complementary techniques. The increase of Mn(2+) proportion had remarkably enhanced the peroxidase activity and magnetism. The catalytic activity of mixed ferrites was found to follow Michaelis-Menten kinetics and was noticeably higher than native Fe(3)O(4). The calculated K(m) and K(cat) exhibited strong affinity with substrates which were remarkably higher than similar sized native magnetite nanoparticles and horseradish peroxidase (HRP). These findings stimulated us to develop carboxyl modified Fe(1-x)Mn(x)Fe(2)O(4) nanoparticles using phosphonomethyl immunodiacetic acid (PMIDA) to engineer PMIDA-Fe(1-x)Mn(x)Fe(2)O(4) fabricated enzyme linked immunosorbent assay (ELISA). Results of both PMIDA-Fe(1-x)Mn(x)Fe(2)O(4) linked ELISA revealed that the enhancements in absorbance during the catalysis of enzyme substrate were linearly proportional to the concentration of mouse IgG within the range between 0.1 μg/ml and 2.5 μg/ml. Further, this detection was ten times lower than previous reports and the detection limit of mouse IgG was 0.1 μg/ml. The advantages of our fabricated artificial peroxidase mimetics are combined of low cost, easy to prepare, better stability and tunable catalytic activity. Moreover, this method provides a new horizon for the development of promising analytical tools in the application of biocatalysis, bioassays, and bioseparation., (Copyright © 2011 Elsevier B.V. All rights reserved.)