ABSTRACT
Development of drug-delivery systems that allow simultaneous in vivo imaging has gained much interest. We report a novel strategy to encapsulate metal nanoparticles (NPs) within alginate gel for in vivo imaging. The cell lysate of recombinant Escherichia coli strain, expressing Arabidopsis thaliana phytochelatin synthase and Pseudomonas putida metallothionein genes, was encapsulated within the alginate gel. Incubation of alginate gel with metal ion precursors followed by UV irradiation resulted in the synthesis of high concentrations of metal NPs, such as Au, Ag, CdSe, and EuSe NPs, within the gel. The alginate gel with metal NPs was used as a drug-delivery system by further co-encapsulating doxorubicin and rifampicin, the release of which was made to be pH-dependent. This system can be conveniently and safely used for in vitro and in vivo bioimaging, enabled by the metal NPs formed within the gel matrix without using toxic reducing reagents or surfactants.
Subject(s)
Alginates/chemistry , Drug Carriers/chemistry , Fluorescent Dyes/chemistry , Gels/chemistry , Metal Nanoparticles/chemistry , Aminoacyltransferases/genetics , Aminoacyltransferases/metabolism , Animals , Antineoplastic Agents/chemistry , Antineoplastic Agents/pharmacology , Apoptosis/drug effects , Arabidopsis/enzymology , Doxorubicin/chemistry , Doxorubicin/pharmacology , Drug Liberation , Escherichia coli/genetics , Hep G2 Cells , Humans , Male , Metallothionein/genetics , Metallothionein/metabolism , Metals/chemistry , Mice, Nude , Pseudomonas putida/enzymology , Rifampin/chemistry , Rifampin/pharmacologyABSTRACT
A composite consisting of cerium oxide nanoparticles (nanoceria) and an oxidative enzyme co-entrapped in an agarose gel has been developed for the reagent-free colorimetric detection of biologically important target molecules. The oxidase, immobilized in the agarose matrix, promotes the oxidation of target molecules to generate H2O2 that subsequently induces changes in the physicochemical properties of nanoceria exhibiting a color change from white/light-yellow into intense-yellow/light-orange without any requirement for additional colorimetric substrates. By utilizing the unique color-changing property of nanoceria entrapped within the agarose gel, target glucose molecules were very specifically detected over a wide linear range from 0.05 to 2mM, which is suitable to measure the serum glucose level, with excellent operational stability over two weeks at room temperature. The biosensor also exhibited a high degree of precision and reproducibility when employed to detect glucose present in real human serum samples. We expect that this novel nanoceria-based biosensing format could be readily extended to other oxidative enzymes for the convenient detection of various clinically important target molecules.
Subject(s)
Biosensing Techniques/methods , Enzymes, Immobilized/chemistry , Glucose/isolation & purification , Oxidoreductases/chemistry , Cerium/chemistry , Colorimetry , Glucose/chemistry , Humans , Hydrogen Peroxide/chemistry , Nanoparticles/chemistry , Oxidation-ReductionABSTRACT
A colorimetric biosensor for convenient quantification of ethanol and methanol is described. The biosensor utilizes a 'one-pot' nanocomposite consisting of Fe3O4 magnetic nanoparticles (MNPs) and alcohol oxidase (Al Ox) simultaneously entrapped in large pore sized mesocellular silica. Al Ox immobilized in the silica generates H2O2 in the presence of alcohol in a sample, which subsequently activates MNPs in the mesopores of the silica to convert a colorimetric substrate into a colored product. Using this strategy, a target alcohol was specifically detected through a very convenient colorimetric signal resulting from the combined reactions. This strategy enabled successful sensing of ethanol and methanol in a linear concentration range from 100 to 500 microM with a detection limit as low as 25 microM by employing 2,2'-azino-bis(3-ethylbenzo-thiazoline-6-sulfonic acid) diammonium salt (ABTS) as a peroxidase substrate. Along with excellent reusability via simple magnetic capturing, enhanced operational stability was achieved by the nanocomposite system. The present nanocomposite would serve as a novel platform for rapid and convenient analysis of alcohol.