title: Evaluation of back scatter interferometry, a method for detecting protein binding in solution.
abstract: Back Scatter Interferometry (BSI) has been proposed to be a highly sensitive and versatile refractive index sensor usable for analytical detection of biomarker and protein interactions in solution. However the existing literature on BSI lacks a physical explanation of why protein interactions in general should contribute to the BSI signal. We have established a BSI system to investigate this subject in further detail. We contribute with a thorough analysis of the robustness of the sensor including unwanted contributions to the interferometric signal caused by temperature variation and dissolved gasses. We report a limit of the effective minimum detectability of refractive index at the 10(-7) level. Long term stability was examined by simultaneously monitoring the temperature inside the capillary revealing an average drift of 2.0 × 10(-7) per hour. Finally we show that measurements on protein A incubated with immunoglobulin G do not result in a signal that can be attributed to binding affinities as otherwise claimed in literature.
authors.affiliation: Dept. of Clinical Biochemistry, Aalborg University Hospital, Hobrovej 18-22, 9000 Aalborg, Denmark.
authors.forename: S T
authors.initials: ST
authors.lastname: Jepsen
authors.forename: T M
authors.initials: TM
authors.lastname: Jørgensen
authors.forename: W
authors.initials: W
authors.lastname: Zong
authors.forename: T
authors.initials: T
authors.lastname: Trydal
authors.forename: S R
authors.initials: SR
authors.lastname: Kristensen
authors.forename: H S
authors.initials: HS
authors.lastname: Sørensen
mesh_terms: D015374:Biosensing Techniques; D006801:Humans; D007074:Immunoglobulin G / Q000737:chemistry / Q000378:metabolism*; D007368:Interferometry / Q000379:methods*; D011485:Protein Binding; D012031:Refractometry; D013205:Staphylococcal Protein A / Q000737:chemistry / Q000378:metabolism*
chemical_list: D007074:Immunoglobulin G; D013205:Staphylococcal Protein A