Noncompetitive homogeneous immunodetection of small molecules based on beta-glucuronidase complementation.

Area of Science:

• Biochemistry
• Immunotechnology
• Biosensor Development

Background:

• Homotetrameric enzymes like beta-glucuronidase (GUS) require subunit assembly for activity.
• A mutant GUS (GUSm) with inhibited dimer-of-dimerization offers a basis for biosensor development.
• Antibody variable domains (VH/VL) exhibit antigen-dependent affinity changes.

Purpose of the Study:

• To develop a novel noncompetitive homogeneous immunoassay for antigen detection.
• To create a biosensor utilizing a mutant GUS (GUSm) enzyme system.
• To detect small molecules and proteins using antibody-GUSm fusion proteins.

Main Methods:

• Constructed fusion proteins of antibody VH/VL domains with GUSm subunits.
• Utilized GUS activity measurement to quantify antigen binding.
• Developed colorimetric and fluorescence assays for antigen detection.

Main Results:

• Successfully detected antigens 4-hydroxy-3-nitrophenylacetyl (NP) and bone Gla protein (BGP).
• Achieved detection of NP, 5-iodo-NP, and BGP within 1 hour.
• Demonstrated higher signal/background ratios compared to conventional ELISA.
• Showcased instantaneous response upon component mixing.

Conclusions:

• The developed biosensor system is convenient and high-throughput.
• The system enables rapid, separation-free antigen detection.
• This approach is effective for analyzing diverse small molecules in environmental and clinical samples.