Particle-by-particle quantification of protein adsorption onto poly(ethylene glycol) grafted surfaces

Abstract

The use and advantage of flow cytometry as a particle-by-particle, low sampling volume, high-throughput screening technique for quantitatively examining the non-specific adsorption of proteins onto surfaces is presented. The adsorption of three proteins: bovine serum albumin (BSA), immunoglobulin gamma (IgG) and protein G, incubated at room temperature for 2 h onto organosilica particles modified with poly(ethylene glycol) (PEG) of increasing MW (2000, 3400, 6000, 10,000 and 20,000 g mol⁻¹) and grafted amounts (0.14–1.4 mg m⁻²) was investigated as a model system. Each protein exhibited Langmuir-like, high affinity monolayer limited adsorption on unmodified particles with the proteins reaching surface saturation at 1.8, 4.0 and 2.5 mg m⁻² for BSA, IgG and protein G, respectively. Protein adsorption on PEG-modified surfaces was found to decrease with increasing amounts of grafted polymer. PEG grafting amounts >0.6 mg m⁻² effectively prevented the adsorption of the larger two proteins (BSA and IgG) while a PEG grafting amount >1.3 mg m⁻² was required to prevent the adsorption of the smaller protein G.

Keywords:

• protein adsorption
• protein antifouling layers
• PEG grafting and characterization
• flow cytometry

Acknowledgements

This project was financially supported by the Australian Research Council (FF0455861) and the NHMRC (301267).