Surface engineering of poly(methylmethacrylate): Effects on fluorescence immunoassay

Area of Science:

• Biomaterials Science
• Surface Chemistry
• Analytical Chemistry

Background:

• Poly(methylmethacrylate) (PMMA) is a common surface for immunoassays.
• Antibody immobilization on surfaces can lead to clustering and reduced assay performance.
• Optimizing antibody presentation is crucial for sensitive and specific immunoassays.

Purpose of the Study:

• To investigate surface engineering strategies for PMMA to improve fluorescence immunoassay performance.
• To understand how different surface chemistries affect antibody orientation, loading, and binding.
• To identify surface modifications that minimize antibody clustering and self-quenching.

Main Methods:

• Surface modification of PMMA using ultraviolet-ozone oxidation, poly(ethyleneglycol) (PEG4) chains, and carboxylic acid-terminated dendrimers (G1.5 to G5.5).
• Chemical coupling of anti-human IgG antibodies via amide formation.
• Characterization using fluorescence immunoassay (FIA) and neutron reflectometry (NR).
• Evaluation of antibody surface loading, antigen binding capacity, and nonspecific binding.

Main Results:

• Physical adsorption on PMMA resulted in multilayers with low antigen binding.
• Carboxylated surfaces formed monolayers with chemical coupling.
• Antibody clustering and self-quenching were observed on unmodified and some modified surfaces.
• PEG4 surfaces showed high conformational flexibility.
• Dendrimer-modified surfaces exhibited collapse and densification.
• The G3.5 dendrimer surface provided the optimal balance of high specific and low nonspecific signals in FIA.

Conclusions:

• Surface chemistry significantly influences antibody behavior and immunoassay results.
• Dendrimer surface modification, particularly G3.5, effectively controls antibody presentation.
• Optimized antibody orientation and reduced clustering on G3.5 dendrimers enhance immunoassay specificity and sensitivity.