title: Ag@SiO2-entrapped hydrogel microarray: a new platform for a metal-enhanced fluorescence-based protein assay.
abstract: We developed a novel protein-based bioassay platform utilizing metal-enhanced fluorescence (MEF), which is a hydrogel microarray entrapping silica-coated silver nanoparticles (Ag@SiO2). As a model system, different concentrations of glucose were detected using a fluorescence method by sequential bienzymatic reaction of hydrogel-entrapped glucose oxidase (GOX) and peroxidase (POD) inside a hydrogel microarray. Microarrays based on poly(ethylene glycol)(PEG) hydrogels were prepared by photopatterning a solution containing PEG diacrylate (PEG-DA), photoinitiator, enzymes, and Ag@SiO2. The resulting hydrogel microarrays were able to entrap both enzymes and Ag@SiO2 without leaching and deactivation problems. The presence of Ag@SiO2 within the hydrogel microarray enhanced the fluorescence signal, and the extent of the enhancement was dependent on the thickness of silica shells and the amount of Ag@SiO2. Optimal MEF effects were achieved when the thickness of the silica shell was 17.5 nm, and 0.5 mg mL(-1) of Ag@SiO2 was incorporated into the assay systems. Compared with the standard hydrogel microarray-based assay performed without Ag@SiO2, more than a 4-fold fluorescence enhancement was observed in a glucose concentration range between 10(-3) mM and 10.0 mM using hydrogel microarray entrapping Ag@SiO2, which led to significant improvements in the sensitivity and the limit of detection (LOD). The hydrogel microarray system presented in this study could be successfully combined with a microfluidic device as an initial step to create an MEF-based micro-total-analysis-system (μ-TAS).
authors.affiliation: Department of Chemical and Biomolecular Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, South Korea. wongun@yonsei.ac.kr.
authors.forename: Eunji
authors.initials: E
authors.lastname: Jang
authors.forename: Minsu
authors.initials: M
authors.lastname: Kim
authors.forename: Won-Gun
authors.initials: WG
authors.lastname: Koh
mesh_terms: D001234:Aspergillus niger / Q000201:enzymology; D015374:Biosensing Techniques / Q000295:instrumentation / Q000379:methods*; D004800:Enzymes, Immobilized / Q000737:chemistry / Q000378:metabolism; D005947:Glucose / Q000032:analysis; D005949:Glucose Oxidase / Q000737:chemistry / Q000378:metabolism*; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000737:chemistry*; D056656:Lab-On-A-Chip Devices; D046228:Microarray Analysis / Q000295:instrumentation / Q000379:methods*; D011092:Polyethylene Glycols / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry*; D012834:Silver / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
chemical_list: D004800:Enzymes, Immobilized; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D012834:Silver; D011092:Polyethylene Glycols; D012822:Silicon Dioxide; D005949:Glucose Oxidase; D005947:Glucose