title: An organic thin film photodiode as a portable photodetector for the detection of alkylphenol polyethoxylates by a flow fluorescence-immunoassay on magnetic microbeads in a microchannel.
abstract: An organic thin film photodiode (OPD) was successfully employed as a portable photodetector in a competitive enzyme-linked immunosorbent assay (ELISA) of a class of nonionic surfactants, namely alkylphenol polyethoxylates (APnEOs) which are an environmental pollutant. Microbeads that were chemically immobilized with an anti-APnEOs antibody were used in the assay. The OPD consisted of a layer of copper phthalocyanine (CuPc), C60 and a second layer of bathocuproine (BCP) with a bulk heterojunction composed of CuPc and C60 prepared by a vapor deposition method on an indium-tin oxide coated glass substrate. The OPD showed an incident photon-current efficiency (IPCE) of approximately 19% for light at a wavelength of 585 nm. This relatively high IPCE at 585 nm makes it suitable for detecting the fluorescence of resorufin (λem=585 nm), the product of the competitive ELISA, produced through the enzymatic reaction of Amplex Red with horseradish peroxidase (HRP) and H2O2. A fluorometric detector was assembled on a microchip by combining the fabricated OPD and a commercial LED as a photodetector and a light source, respectively. The photocurrent of the OPD due to the fluorescence of resorufin was proportional to the concentration of resorufin in the concentration range from 0 to 8 μM. When the fabricated OPD was used as a portable photodetector, the competitive ELISA of APnEOs using HRP labeled APnEOs (HRP-APnEOs) was performed on magnetic microbeads on which surface an anti-APnEOs antibody had been immobilized. A typical sigmoidal calibration curve was obtained and the data were in good agreement with a numerical simulation, where the photocurrent of the OPD was plotted against the concentration of APnEOs, determined via the competitive ELISA. The detection limit of the immunoassay for APnEOs was approximately 2 and 4 ppb in batch and flow system, respectively.
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan.
authors.forename: Ryoichi
authors.initials: R
authors.lastname: Ishimatsu
authors.forename: Azusa
authors.initials: A
authors.lastname: Naruse
authors.forename: Rong
authors.initials: R
authors.lastname: Liu
authors.forename: Koji
authors.initials: K
authors.lastname: Nakano
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yahiro
authors.forename: Chihaya
authors.initials: C
authors.lastname: Adachi
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Imato
mesh_terms: D000906:Antibodies / Q000737:chemistry; D001667:Binding, Competitive; D002138:Calibration; D004785:Environmental Pollutants / Q000032:analysis*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005455:Fluorescent Antibody Technique; D037741:Fullerenes / Q000737:chemistry; D006735:Horseradish Peroxidase / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000737:chemistry; D007211:Indoles / Q000737:chemistry; D057230:Limit of Detection; D059346:Magnets; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation / Q000379:methods*; D009942:Organometallic Compounds / Q000737:chemistry; D010078:Oxazines / Q000737:chemistry; D010618:Phenanthrolines / Q000737:chemistry; D011092:Polyethylene Glycols / Q000032:analysis*; D013501:Surface-Active Agents / Q000032:analysis*; D017971:Tin Compounds / Q000737:chemistry
chemical_list: D000906:Antibodies; D004785:Environmental Pollutants; D037741:Fullerenes; D007211:Indoles; D009942:Organometallic Compounds; D010078:Oxazines; D010618:Phenanthrolines; D013501:Surface-Active Agents; D017971:Tin Compounds; C470430:Amplex Red; C015445:copper phthalocyanine; D011092:Polyethylene Glycols; C014180:resorufin; C109984:indium tin oxide; C002478:bathocuproine; D006861:Hydrogen Peroxide; D006735:Horseradish Peroxidase; C069837:fullerene C60
keywords: ELISA; Microbeads; Microchip; Organic photodiodes