title: HIgG detection by histidine carrying AFM tips (cantilevers).
abstract: "Atomic Force Microscope" (AFM) tips (cantilevers) carrying a pseudo-specific ligand, i.e., histidine were prepared and investigated for detection of Human Immunoglobulin-G (HIgG) in aqueous media. The AFM tips (cantilevers) were first treated with HNO(3) and silanized to create amino groups; then glutaraldehyde (GA) was bonded via these surface amino groups; and finally, histidine molecules were immobilized by reaction of the amino groups of histidine with the free aldehyde groups of GA. Optimal immobilization conditions were described. Immobilizations were observed both by optical and confocal laser scanning microscopy. Interactions between the histidine carrying AFM tips (cantilevers) and the aqueous medium containing HIgG with different concentrations were quantified by "the separation distance" measured with the AFM system as the main variable. A quite nice linear correlation between the HIgG concentration and the separation distance was measured with AFM system. Interactions were also followed by an alternative "Modified Lowry" method, in which similar behavior was observed. We were able to measure HIgG concentration in aqueous media down to 0.055 pmol/micro l (8 mg/dl) concentration with this AFM based novel immunosensor.
authors.affiliation: Baskent University, Ankara, Turkey.
authors.forename: M Oya
authors.initials: MO
authors.lastname: Cinar
authors.forename: I Cengiz
authors.initials: IC
authors.lastname: Koçum
authors.forename: Hakan
authors.initials: H
authors.lastname: Ayhan
authors.forename: Erhan
authors.initials: E
authors.lastname: Pişkin
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D006639:Histidine / Q000737:chemistry*; D006801:Humans; D007074:Immunoglobulin G / Q000032:analysis*; D008024:Ligands; D018625:Microscopy, Atomic Force / Q000295:instrumentation / Q000379:methods*; D018613:Microscopy, Confocal; D011437:Propylamines / Q000737:chemistry; D012821:Silanes / Q000737:chemistry; D017655:Silicon Compounds / Q000737:chemistry; D013499:Surface Properties
chemical_list: D007074:Immunoglobulin G; D008024:Ligands; D011437:Propylamines; D012821:Silanes; D017655:Silicon Compounds; C088294:3-aminopropyltrimethoxysilane; D006639:Histidine; C032734:silicon nitride