Programmable interactions with biomimetic DNA linkers at fluid membranes and interfaces

At the heart of the structured architecture and complex dynamics of biological systems are specific and timely interactions operated by biomolecules. In many instances, biomolecular agents are spatially confined to flexible lipid membranes where, among other functions, they control cell adhesion, motility and tissue formation. Besides being central to several biological processes, \emph{multivalent interactions} mediated by reactive linkers confined to deformable substrates underpin the design of synthetic-biological platforms and advanced biomimetic materials. Here we review recent advances on the experimental study and theoretical modelling of a heterogeneous class of biomimetic systems in which synthetic linkers mediate multivalent interactions between fluid and deformable colloidal units, including lipid vesicles and emulsion droplets. Linkers are often prepared from synthetic DNA nanostructures, enabling full programmability of the thermodynamic and kinetic properties of their mutual interactions. The coupling of the statistical effects of multivalent interactions with substrate fluidity and deformability gives rise to a rich emerging phenomenology that, in the context of self-assembled soft materials, has been shown to produce exotic phase behaviour, stimuli-responsiveness, and kinetic programmability of the self-assembly process. Applications to (synthetic) biology will also be reviewed.Comment: 63 pages, revie

Adsorption and binding dynamics of graphene-supported phospholipid membranes using the QCM-D technique

We report on the adsorption dynamics of phospholipid membranes on graphene-coated substrates using the quartz crystal microbalance with dissipation monitoring (QCM-D) technique. We compare the lipid vescle interaction and membranne formation on gold and silicon dioxide QCM crystal surfaces with their graphene oxide (GO) and reduced (r)GO coated counterparts, and report on the different lipid structures obtained. We establish graphene derivative coatings as support surfaces with tuneable hydrophobicity for the formation of controllable lipid structures. One structure of interest formed are lipid monolayer membrannes which were formed on rGO, which are otherwise challenging to produce. We also demonstrate and monitor biotin-avidin binding on such a membranne, which will then serve as a platform for a wide range of biosensing applications. The QCM-D technique could be extended to both fundamental studies and applications of other covalent and non-covalent interactions in 2-dimensional materials

A basis for molecular factories: multifunctionality and immobilization of biomolecule-polymer assemblies

Bio-inspired planar polymer membranes are synthetic membranes designed to be combined with biomolecules such as proteins, enzymes or peptides. These membranes provide both an increased mechanical stability as well as an environment to preserve the functionality of the biomolecules. In this thesis, two different kinds of planar membrane systems are demonstrated. In the first project, a sensor for phenolic compounds based on a bio-inspired polymer membrane was developed. Functional surfaces were generated by combining enzymes with polymer membranes composed of an amphiphilic, asymmetric block copolymer. Firstly, polymer films which were formed at the air-water interface were transferred onto silica solid support, by using the Langmuir-Blodgett method. The films were characterized according to their properties, including film thickness, wettability, topography, and roughness. The most promising membranes were used for enzyme attachment. Two model enzymes, laccase and tyrosinase, were adsorbed to the surface and their activity regarding the conversion of phenolic compounds was measured. This project is described in Chapter 1 in detail. In the second project, the interaction of the model pore-forming peptide melittin was studied in combination with a planar synthetic membrane. The investigation focused the interaction of melittin with amphiphilic block copolymer-based synthetic planar membranes as well as the insertion of melittin into these membranes to induce pore formation. Some specific molecular properties of the block copolymers and of the resulting membranes were selected for the investigation, such as hydrophilic to hydrophobic block ratio, membrane thickness and surface roughness. Through melittin addition to the synthetic membranes, melittin insertion requirements were better understood. This project is described in Chapter 2 in detail. Each chapter contains a separate introduction, material and methods section and conclusion and outlook specific to the project.20 In summary, in this thesis the properties of different combinations and applications of polymer-based membranes with biomolecules were investigated to a deeper level

Recent Advances in Hybrid Biomimetic Polymer-Based Films: from Assembly to Applications

Biological membranes, in addition to being a cell boundary, can host a variety of proteins that are involved in different biological functions, including selective nutrient transport, signal transduction, inter- and intra-cellular communication, and cell-cell recognition. Due to their extreme complexity, there has been an increasing interest in developing model membrane systems of controlled properties based on combinations of polymers and different biomacromolecules, i.e., polymer-based hybrid films. In this review, we have highlighted recent advances in the development and applications of hybrid biomimetic planar systems based on different polymeric species. We have focused in particular on hybrid films based on (i) polyelectrolytes, (ii) polymer brushes, as well as (iii) tethers and cushions formed from synthetic polymers, and (iv) block copolymers and their combinations with biomacromolecules, such as lipids, proteins, enzymes, biopolymers, and chosen nanoparticles. In this respect, multiple approaches to the synthesis, characterization, and processing of such hybrid films have been presented. The review has further exemplified their bioengineering, biomedical, and environmental applications, in dependence on the composition and properties of the respective hybrids. We believed that this comprehensive review would be of interest to both the specialists in the field of biomimicry as well as persons entering the field