In situ peptide-modified supported lipid bilayers for controlled cell attachment

The control of cellular interactions with engineered materials is critical for the development of cell-integrated biochips used in cell-based sensors, "lab-on-a-chip" bioanalytical systems, and artificial neuronal networks, as well as medical implants and functional biomaterial scaffolds for tissue engineering. Supported lipid bilayers offer efficient reduction of nonspecific cell and protein binding and, if selectively functionalized, constitute one attractive approach to surface modification strategies of materials used in such devices. The present work describes the in situ modification of supported lipid bilayers through the coupling of a cysteine-terminated peptide to thiol-reactive maleimido lipids incorporated in the bilayer. The accumulation of peptide at the lipid bilayer interface was monitored by the quartz crystal microbalance technique with dissipation monitoring (QCM-D). Coupling of the peptide could be detected by QCM-D with a high signal-to-noise ratio despite its low molecular weight (2 kDa), primarily because the mass uptake included both peptide and the water associated to it. Lipid bilayers that were modified with the cysteine-terminated IKVAV-containing peptide promoted the binding of anti-IKVAV antibodies, as well as the attachment of PC 12 cells, which express a membrane receptor for the IKVAV sequence. Very low nonspecific binding of peptides, proteins, and the cells was observed on nonfunctionalized lipid bilayers. Similarly, IKVAV-functionalized lipid bilayers were resistant to serum protein adsorption as well as the binding of non-IKVAV-specific antibodies. QCM-D and fluorescence recovery after photobleaching revealed that the lipid bilayers persisted under all the experimental conditions used for cell attachment, including staining and fixation. Thus, the described lipid-based surface modification is highly relevant for the development of controlled cell-attachment substrates and can even be applicable for patterning cell attachment because lipid-bilayer formation by vesicle fusion is material-specific.