Characterisation of morphology of self-assembled PEG monolayers: a comparison of mixed and pure coatings optimised for biosensor applications

• Published in: Analytical and bioanalytical chemistry 2008-07, Vol.391 (5), p.1783-1791
• Main Authors: Mehne, Jochen, Markovic, Goran, Pröll, Florian, Schweizer, Nina, Zorn, Stefan, Schreiber, Frank, Gauglitz, Günter
• Format: Article
• Language: English
• Subjects: Adsorption; Analytical Chemistry; Antibodies; Atomic force microscopy (AFM); Atrazine - analysis; Atrazine - chemistry; Atrazine - immunology; Binding Sites; Biochemistry; Biosensing Techniques - methods; Biosensor; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Coated Materials, Biocompatible - chemistry; Dextrans - chemistry; Ellipsometry; Food Science; Glass - chemistry; Laboratory Medicine; Microscopy, Atomic Force; Molecular Weight; Monitoring/Environmental Analysis; Oligonucleotides - analysis; Oligonucleotides - chemistry; Original Paper; Ovalbumin - chemistry; Polarisation modulation infrared reflection absorption spectroscopy (PM-IRRAS); Poly(ethylene glycol); Polyethylene Glycols - chemistry; Reflectometric interference spectroscopy (RIfS); Sensitivity and Specificity; Spectrum Analysis - methods; Streptavidin - analysis; Streptavidin - chemistry; Surface chemistry; Surface Properties
• ISSN: 1618-2642; 1618-2650
• DOI: 10.1007/s00216-008-2066-0

For detection of low concentrations of analytes in complex biological matrices using optical biosensors, a high surface loading with capture molecules and a low nonspecific binding of nonrelevant matrix molecules are essential. To tailor biosensor surfaces in such a manner, poly(ethylene glycols) (PEG) in varying lengths were immobilised covalently onto glass-type surfaces in different mixing ratios and concentrations, and were subsequently modified with three different kinds of receptors. The nonspecific binding of a model protein (ovalbumin, OVA) and the maximum loading of the respective analytes to these prepared surfaces were monitored using label-free and time-resolved reflectometric interference spectroscopy (RIfS). The three different analytes used varied in size: 150 kDa for the anti-atrazine antibody, 60 kDa for streptavidin and 5 kDa for the 15-bp oligonucleotide. We investigated if the mixing of PEG in different lengths could increase the surface loadings of analyte mimicking a three-dimensional matrix as was found using dextrans as sensor coatings. In addition, the effect on the surface loading was investigated with regard to the size of the analyte molecule using such mixed PEGs on the sensor surface. For further characterisation of the surface coatings, polarisation modulation infrared reflection absorption spectroscopy, atomic force microscopy, and ellipsometry were applied.