title: PEG Functionalization of Whispering Gallery Mode Optical Microresonator Biosensors to Minimize Non-Specific Adsorption during Targeted, Label-Free Sensing.
abstract: Whispering Gallery Mode (WGM) optical microresonator biosensors are a powerful tool for targeted detection of analytes at extremely low concentrations. However, in complex environments, non-specific adsorption can significantly reduce their signal to noise ratio, limiting their accuracy. To overcome this, poly(ethylene glycol) (PEG) can be employed in conjunction with appropriate recognition elements to create a nonfouling surface capable of detecting targeted analytes. This paper investigates a general route for the addition of nonfouling elements to WGM optical biosensors to reduce non-specific adsorption, while also retaining high sensitivity. We use the avidin-biotin analyte-recognition element system, in conjunction with PEG nonfouling elements, as a proof-of-concept, and explore the extent of non-specific adsorption of lysozyme and fibrinogen at multiple concentrations, as well as the ability to detect avidin in a concentration-dependent fashion. Ellipsometry, contact angle measurement, fluorescence microscopy, and optical resonator characterization methods were used to study non-specific adsorption, the quality of the functionalized surface, and the biosensor's performance. Using a recognition element ratio to nonfouling element ratio of 1:1, we showed that non-specific adsorption could be significantly reduced over the controls, and that high sensitivity could be maintained. Due to the frequent use of biotin-avidin-biotin sandwich complexes in functionalizing sensor surfaces with biotin-labeled recognition elements, this chemistry could provide a common basis for creating a non-fouling surface capable of targeted detection. This should improve the ability of WGM optical biosensors to operate in complex environments, extending their application towards real-world detection.
authors.affiliation: Department of Bioengineering, University of Missouri, Columbia, MO 65201, USA. fwwcb@mail.missouri.edu.
authors.forename: Fanyongjing
authors.initials: F
authors.lastname: Wang
authors.affiliation: Department of Biochemistry, University of Missouri, Columbia, MO 65201, USA. meawm4@mail.missouri.edu.
authors.forename: Mark
authors.initials: M
authors.lastname: Anderson
authors.affiliation: Department of Chemical Engineering, University of Missouri, Columbia, MO 65201, USA. bernardsm@missouri.edu.
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Bernards
authors.affiliation: Department of Bioengineering, University of Missouri, Columbia, MO 65201, USA. hunthk@missouri.edu.
authors.forename: Heather K
authors.initials: HK
authors.lastname: Hunt
mesh_terms: D000327:Adsorption; D000465:Algorithms; D000818:Animals; D015374:Biosensing Techniques / Q000295:instrumentation*; D001710:Biotin / Q000378:metabolism; D019921:Biotinylation; D002417:Cattle; D002645:Chickens; D005340:Fibrinogen / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008863:Microspheres; D008962:Models, Theoretical; D009113:Muramidase / Q000378:metabolism; D055095:Optics and Photonics / Q000295:instrumentation*; D011092:Polyethylene Glycols / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry; D013194:Staining and Labeling / Q000379:methods*
chemical_list: D011092:Polyethylene Glycols; D001710:Biotin; D012822:Silicon Dioxide; D005340:Fibrinogen; D009113:Muramidase
keywords: PEG; non-specific adsorption; nonfouling surfaces; optical microresonator; surface characterization; surface functionalization