Direct immunosensing by spectral correlation interferometry: assay characteristics versus antibody immobilization chemistry

Abstract

A 3-channel biosensor based on spectral correlation interferometry (SCI) has been adapted for direct optical detection of antigens by measuring changes in thickness of a biolayer on functionalized glass slips employed as affordable single-use sensor chips. The instrument is insensitive to the bulk refractive index of a solution under test and provides signals in metrological units (pm or nm). Using real-time monitoring with the SCI, protocols for fabrication of sensor chips with different functional (epoxylated, carboxylated, and biotinylated) surfaces for antibody immobilization have been developed and optimized to minimize chip-to-chip variations and achieve better limit of detection (LOD), shorter assay time, and longer shelf life. The optimized coupling surfaces have been compared for detection of human serum albumin (HSA) used as a model agent of medical significance. The dynamic ranges for measuring the HSA concentration were 0.07-20, 0.12-30, and 0.25-10 μg/ml, and the assay durations were less than 20, 15, and 30 min for the epoxylated, carboxylated, and biotinylated chips, respectively. The advantages of each type of sensor chip have been shown, namely, the carboxylated chips feature the shortest assay time, the epoxylated ones demonstrate the best LOD, and the biotinylated chips exhibit the longest shelf life in an unprotected environment. The developed protocols of antibody immobilization can be used in different biosensors and assay techniques including those based on fluorescent, magnetic or plasmonic labels, etc. The SCI is well compatible with various partially transparent layers used in biosensing and with microarrays for multi-analyte detection.

Data on characterization and validation of assays for ultrasensitive quantitative detection of small molecules: Determination of free thyroxine with magnetic and interferometric methods

“…We used label-free biosensors based on the spectral-phase interferometry (SPI) [8] and spectral-correlation interferometry (SCI) [9] , [10] to evaluate the kinetic binding and performance of immunoreagents. The biosensors provide real-time monitoring of changes in thickness of a biomolecular layer bound on the sensor chip surface, averaged over the sensing area [11] , [12] .…”

Applications of Pristine and Functionalized Carbon Nanotubes, Graphene, and Graphene Nanoribbons in Biomedicine

“…Two basic requirements have to be met for bioimaging. There needs to be a fast and sensitive method for detection, and the contrast agents or spectroscopic markers must meet all the requirements, i.e., biodegradability, biocompatibility, high specificity, sensitivity, and general applicability [100][101][102][103]. Bioimaging can track the development of abnormal processes, such as cancer development, hypoxia/hyperoxia, or necrosis.…”

Critical assessment of relevant methods in the field of biosensors with direct optical detection based on fibers and waveguides using plasmonic, resonance, and interference effects

“…One of the interferometers is the glass slide with the recognition spots or wells, the second one is a scanning interferometer that employs periodical modulation of path differences of the interfering beams [389]. The quality of expoxilated or biotinylated sensor chips used in this type of spectro-correlation interferometry is reported with LOD values in the area of mg/L [390].…”