Immobilized antibody orientation analysis using secondary ion mass spectrometry and fluorescence imaging of affinity-generated patterns.
This study assesses the capability of high-resolution surface analytical tools to distinguish immobilized antibody orientations on patterned surfaces designed for antibody affinity capture. High-fidelity, side-by-side copatterning of protein A (antibody Fc domain affinity reagent) and fluorescein (antibody Fab domain hapten) was achieved photolithographically on commercial amine-reactive hydrogel polymer surfaces. This was verified from fluorescence imaging using fluorescently labeled protein A and intrinsic fluorescence from fluorescein. Subsequently, dye-labeled murine antifluorescein antibody (4-4-20) and antibody Fab and Fc fragments were immobilized from solution onto respective protein A- and fluorescein- copatterned or control surfaces using antibody-ligand affinity interactions. Fluorescence assays support specific immobilization to fluorescein hapten- and protein A-patterned regions through antigen-antibody recognition and natural protein A-Fc domain interactions, respectively. Affinity-based antibody immobilization on the two different copatterned surfaces generated side-by-side full antibody "heads-up" and "tails-up" oriented surface patterns. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) analysis, sensitive to chemical information from the top 2 to 3 nm of the surface, provided ion-specific images of these antibody patterned regions, imaging and distinguishing characteristic ions from amino acids enriched in Fab domains for antibodies oriented in "heads-up" regions, and ions from amino acids enriched in Fc domains for antibodies oriented in "tails-up" regions. Principal component analysis (PCA) improved the distinct TOF-SIMS amino acid compositional and ion-specific surface mapping sensitivity for each "heads-up" versus "tails-up" patterned region. Characteristic Fab and Fc fragment immobilized patterns served as controls. This provides first demonstration of pattern-specific, antibody orientation-dependent surface maps based on antibody domain- and structure-specific compositional differences by TOF-SIMS analysis. Since antibody immobilization and orientation are critical to many technologies, orientation characterization using TOF-SIMS could be very useful and convenient for immobilization quality control and understanding methods for improving the performance of antibody-based surface capture assays.
Liu
Fang
F
Department of Pharmaceutics and Pharmaceutical Chemistry, University of Utah, Salt Lake City, Utah 84112-5820, USA.
Dubey
Manish
M
Takahashi
Hironobu
H
Castner
David G
DG
Grainger
David W
DW
D000818:Animals; D055910:Antibodies, Immobilized / Q000737:chemistry* / Q000276:immunology; D019793:Fluorescein / Q000737:chemistry; D006046:Gold / Q000737:chemistry; D020100:Hydrogels / Q000737:chemistry; D007140:Immunoglobulin Fab Fragments / Q000737:chemistry; D007141:Immunoglobulin Fc Fragments / Q000737:chemistry; D051379:Mice; D025341:Principal Component Analysis; D018629:Spectrometry, Mass, Secondary Ion / Q000379:methods*; D013205:Staphylococcal Protein A / Q000737:chemistry
D055910:Antibodies, Immobilized; D020100:Hydrogels; D007140:Immunoglobulin Fab Fragments; D007141:Immunoglobulin Fc Fragments; D013205:Staphylococcal Protein A; D006046:Gold; D019793:Fluorescein