Formation of Mesoporous Materials and their use as Lipid Bilayer Supports

Doctoral thesis, 2014

Mesoporous materials have acquired great scientific interest in various applications; something that is largely due to that their properties, such as pore size, pore orientation, material composition and surface chemistry, can be controlled to a large extent. One idea, which has been investigated in this thesis, is to use mesoporous materials as supports for lipid bilayers and by doing so fabricate devices that mimic the cell wall and at the same time has sufficient mechanical robustness for practical use. Such devices include biosensing and drug-delivery constructs where the pores are suggested to provide adequate environment for reconstituted sensing items, such as transmembrane proteins or serve as a reservoirs for therapeutics, and the pore-walls will provide stability to the bilayer. The aim of this thesis was to form mesoporous silica and titiania, and meso-ordered polyethylene glycol diacrylate (PEG-DA) hydrogels, and to use these as supports for lipid bilayers. Both freely supported bilayers and covalently anchored lipid bilayers using “spacers”, also called tethers, were examined. Moreover, the use of mesoporous silica and titania to enhance the detection of small analytes at low concentrations using quartz crystal microbalance with dissipation monitoring (QCM-D) was explored. Mesoporous silica, titiania and PEG-DA hydrogels were successfully synthesized using triblock copolymers or surfactants as structure directing agents. The results showed that bilayers were formed on mesoporous silica and that intact vesicle adsorption was obtained on titania, regardless of porosity. Homogeneously spread bilayers on PEG-DA bulk hydrogels were, however, difficult to form and resulted in that vesicles adsorbed intact or ruptured into lipid bilayer patches. Tethered lipid bilayers on amine-modified mesoporous silica were obtained by adsorbing tether containing vesicles on the surface and rupturing these using amphipathic α-helical (AH) peptides. The QCM-D signal-to noise ratio was shown to be improved when mesoporous silica and titania were used as sensing surfaces, which was investigated by adsorbing different generations of dendrimers. Based upon the results obtained in this thesis, mesoporous materials are considered to be promising supports for lipid bilayers in biosensing and drug delivery devices as well as to enhance the detection of small analytes at low concentration. Furthermore, the formed meso-ordered PEG-DA hydrogel particles have potential as drug delivery vehicles due to their narrow pore-size distribution, and soft and flexible structure.