Modifying Polydimethylsiloxane (PDMS) surfaces

The aim of the project was to modify polydimethylsiloxane (PDMS) surfaces in order to minimize adsorption of proteins. PDMS is used in micro-fluidic devices that control the delivery of samples to a sensor chip in Biacore instrumentation. These instruments are used to characterize interactions between biomolecules with a detection principle based on surface plasmon resonance (SPR). To minimize adsorption of proteins poly-ethylene-oxide (PEO) based surfactants, were added to the buffer. The added PEO surfactants were P20, Pluronic F-127 and Brij 35. Interaction of these surfactants with the sensor chip in Biacore instruments was also examined. Creating a more hydrophilic surface layer on PDMS by oxidation was also examined.
When surfactants were continuously added to protein samples, as in dynamically coating of PDMS surfaces, Brij 35 resulted in the strongest reduction in protein adsorption. Brij 35 was also the surfactant that was easiest to remove from both PDMS and the sensor surfaces. Pluronic bound strongest to surfaces, and is most suitable when only adding surfactant to the buffer in a pre-coating step…


1 Introduction
1.1 Biacore instrumentation
1.2 Surface plasmon resonance detection of molecular interactions
1.3 The microfluidic system
1.4 Protein Adsorption
2 Modifying PDMS
2.1 Dynamic coating with surfactants
2.1.1 HLB
2.1.2 CMC
2.2 Physical properties of PEO based surfactants; P20, Pluronic F-127 and Brij 35
2.2.1 Polyoxyethylene (20) sorbitan monolaurate (P20)
2.2.2 Pluronic F-127
2.2.3 Brij 35
2.3 Protein repelling properties of surfactants
2.4 Chemical modifications of PDMS
2.4.1 Oxidation, extraction and swelling of PDMS
2.4.2 Embedding
2.4.3 Grafting
3 Materials and method
3.1 Chemicals
3.2 Proteins
3.3 Infra red spectra of PDMS surfaces and modifies PDMS surfaces
3.4 Interaction of surfactants with dextran
3.5 Flow system
3.6 Quantification of adsorbed proteins to PDMS
3.7 Dynamic- and pre-coating of PDMS
3.8 Oxidation of PDMS
3.9 Removing adsorbed proteins from PDMS
4 Results and discussion
4.1 Dynamic coating of PDMS
4.2 Pre-coating of PDMS
4.3 Dynamic coating versus Pre-coating
4.4 Oxidation of PDMS
4.5 Removing adsorbed proteins from PDMS
4.6 Infra red Spectra of PDMS surfaces and modifies PDMS surfaces
4.7 Interaction of surfactants and dextran
4.8 Challenges with the development of fluorescence- based quantification method
5 Conclusions
6 Acknowledgements

Author: Essö, Carola

Source: Malardalen University

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