Dip-pen nanolithography with lipids (L-DPN) has become a unique tool for the fabrication of structured lipid membranes. Biological membranes are heterogeneous structures composed of a combination of lipids, which gives the membrane its two-dimensional structure and fluidity, and proteins, which provide the membrane diverse biological functions. DPN uses the tip of an atomic force microscope to directly deposit, by physisorption, the phospholipid ink onto a substrate. Depending on the surface wetting properties, the phospholipid ink tends to stack three dimensionally on the surface or rather spreads to form thin homogeneous membranes. In addition, the phospholipid ink may contain admixings of different functionalized lipids, so that e.g. proteins tagged accordingly can be selectively bound to the lipid patterns. This results in fluid, multivalent biomimetic-patterned membrane systems that are suitable model systems to study biological processes.
An outstanding challenge in L-DPN is to monitor and elucidate the whole process from writing and self-organization in air to the reorganization of the stacks under water in details. Special attention should be paid to phase separation phenomena: it is still an open question, whether ink mixtures get transferred in equal proportions from tip to substrate and whether an homogeneously distribution of admixing can be generally assumed within the generated structures.
The aim of the proposed project is a detailed study and characterization of all processes involved in the generation and details on the organization of bio-mimetic phospholipid membrane stacks generated by DPN. Within this aim, the patterning behaviour of phospholipids in L-DPN will be studied systematically, a structural model of membrane stacks generated by L-DPN will be provided using a unique combination of microscopy techniques and a time resolved analysis of lipid spreading in liquid and of binding events on the lipid structures will also be performed.
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