AVS 53rd International Symposium
    Biomaterial Interfaces Thursday Sessions
       Session BI+AS-ThA

Invited Paper BI+AS-ThA5
Multi-Technique Characterization of Lipid/PEG Interactions and Oligonucleotide Microarrays

Thursday, November 16, 2006, 3:20 pm, Room 2014

Session: Biomolecule-Surface Characterization I
Presenter: H.J. Griesser, University of South Australia
Authors: H.J. Griesser, University of South Australia
K. Vasilev, University of South Australia
B. Thierry, University of South Australia
K. Bremmell, University of South Australia
S. Griesser, University of South Australia
P.-C. Nguyen, University of South Australia
P. Hale, LaTrobe University, Australia
P. Pigram, LaTrobe University, Australia
Correspondent: Click to Email
This contribution will discuss two recent studies utilizing multi-technique characterization of surfaces by both vacuum spectroscopic methods and in contact with aqueous solutions. The first study aimed to investigate why PEG graft surfaces have produced excellent protein resistance in vitro but disappointing outcomes in vivo. Our hypothesis was that a possible reason involves attractive interfacial interactions with lipids that then provide a platform for subsequent protein adsorption. Using three different proein-resistant PEG coatings it was indeed found that two of them gave measurable lipid adsorption. Using lipid molecules that were neutral, positively charged, or negatively charged, and aqueous media of various ionic strengths, we explored the possible role of electrostatic interactions. Interaction force measurements using the AFM colloid probe method showed purely repulsive steric forces on approach, but on retraction adhesive forces were observed in some cases. A key issue is to differentiate between interfacial forces that emanate from the substrate and ‘shine through’ the PEG graft layers, and forces associated with the PEG layer itself. The second study involves the fabrication of micro-patterned surfaces and their use for oligonucleotide and protein microarrays. Using a mask with circular holes we plasma polymerize arrays of dots consisting of thin layers of plasma polymers that carry reactive groups (aldehyde, amine, or epoxy) suitable for covalent immobilization of end-functionalized oligonucleotides or proteins. XPS imaging using a Kratos Ultra unit with a DLD clearly showed the arrays of dots on perfluoropolymer substrate and the immobilization of biomolecules. An IonTOF ToF-SIMS unit with a Bi3+ beam was used to analyze immobilized oligonucleotides. Clearly identifiable peaks were observed with masses up to 2,500 Da and higher, from fragments as large as containing five nucleotides. Different oligonucleotides could be distinguished by the distinct fragmentation patterns.