title: Noncovalent antibody immobilization on porous silicon combined with miniaturized solid-phase extraction (SPE) for array based immunoMALDI assays.
abstract: This paper presents a new strategy to combine the power of antibody based capturing of target species in complex samples with the benefits of microfluidic reverse phase sample preparation on an integrated sample enrichment target (RP-ISET) and the analysis speed of MALDI MS. The immunoaffinity step is performed on an in-house developed 3D-structured high surface area porous silicon (PSi) matrix, which allows efficient antibody immobilization by surface adsorption without any coupling agents in 30-60 min. The hydrophilic nature of the porous silicon surface at the molecular level displays a low adsorption of background peptides when exposed to complex digests or plasma samples, improving the conditions for the antigen specific extraction and subsequent readout. At the same time, the hydrophobic behavior, due to the nanostructured surface, of the PSi material facilitates liquid confinement during the assay. Using a footprint conforming to the standard for 384 well microplates, direct adaption of the protocol into standard sample handling robots is possible. The performance of the proposed immunoaffinity PSi-ISET immunoMALDI (iMALDI) assay was evaluated by specific detection of angiotensin I at a 10 femtomol level in diluted plasma samples (10 μL, 1 nM).
authors.affiliation: Department of Measurement Technology and Industrial Electrical Engineering, Division of Nanotechnology, Lund University, Lund, Sweden.
authors.forename: Hong
authors.initials: H
authors.lastname: Yan
authors.forename: Asilah
authors.initials: A
authors.lastname: Ahmad-Tajudin
authors.forename: Martin
authors.initials: M
authors.lastname: Bengtsson
authors.forename: Shoujun
authors.initials: S
authors.lastname: Xiao
authors.forename: Thomas
authors.initials: T
authors.lastname: Laurell
authors.forename: Simon
authors.initials: S
authors.lastname: Ekström
mesh_terms: D000803:Angiotensin I / Q000097:blood / Q000302:isolation & purification; D055910:Antibodies, Immobilized / Q000276:immunology*; D057927:Hydrophobic and Hydrophilic Interactions; D008904:Miniaturization; D049329:Nanostructures / Q000737:chemistry; D016062:Porosity; D012825:Silicon / Q000737:chemistry*; D052616:Solid Phase Extraction / Q000379:methods*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
chemical_list: D055910:Antibodies, Immobilized; D000803:Angiotensin I; D012825:Silicon