Theoretical guidelines for the design of membrane based biosensors: From lipid membrane stability to polymer mediated specific targeting

This thesis presents the study of four different problems, which are relevant to the design of membrane based biosensors and to the understanding of the physics involved in problems such as cell membrane function. A molecular theory that explicitly includes the molecular details and configurational properties of the species composing the system of interest is used to address these problems. Chapter 1 presents a general introduction. In Chapter 2, the binding of small proteins to ligands that are attached to the free ends of polymers tethered to a planar surface is studied. Chapter 3 describes the study of the interactions between a receptor-modified surface and a bimodal polymer layer tethered to a planar surface, where one of the polymers is ligand functionalized. The results presented in Chapters 2 and 3 can be used to design modified surfaces with tailored abilities for specific targeting. In chapter 4, the phase stability of a fluid lipid layer that is a mixture of monopolar and bipolar lipids is studied. Finally, Chapter 5 presents the study of the phase stability of a fluid lipid layer that is mixture of DSPC and shorter D Cns PCs. The findings of Chapters 4 and 5 suggest that hydrophobic mismatch between different lipid species may play a role in inducing lateral inhomogeneities, which are essential for cell membrane function, in fluid lipid mixtures. The theoretical results presented in this dissertation can be applied to the design of experimental devices such as biosensors and drug delivery systems, where high sensitivity in biospecific recognition, reduction of non-specific interactions and lipid membrane stability are required