FORMATION, DYNAMICS AND CHARACTERIZATION OF SUPPORTED LIPID BILAYERS ON SiO2 NANOPARTICLES
AdvisorWunder, Stephanie L.
Committee memberStrongin, Daniel R.
Ilies, Marc A.
Curvature Dependent Shifts in the Phase Transitions
Effect of Curvature On Lipid Bilayers
Effect of the Surface Properties On the Formation of Supported Lipid Bilayers
Lipid Packing and Morphology On Curved Surfaces
Lipid Sheaths That Envelope and Release Nanoparticle Supported Lipid Bilayers
Nanoparticle Supported Lipid Bilayers
Permanent link to this recordhttp://hdl.handle.net/20.500.12613/646
MetadataShow full item record
AbstractThis work is devoted to understanding the formation of supported lipid bilayers (SLBs) on curved surfaces as a function of lipid properties such as headgroup charge/charge density and alkyl chain length, and nanoparticle properties such as size and surface characteristics. In particular, the formation of SLBs on curved surfaces was studied by varying the size of the underlying substrate SiO2 nanoparticles with size range from 5-100 nm. Curvature-dependent shift in the phase transition behavior of these supported lipid bilayers was observed for the first time. We found that the phase transition temperature, Tm of the SLBs first decreased with decreasing the size of the underlying support, reached a minimum, and then increased when the size of the particles became comparable with the dimensions of the lipid bilayer thickness; the Tm was above that of the multilamellar vesicles (MLVs) of the same lipids. The increase in Tm indicated a stiffening of the supported bilayer, which was confirmed by Raman spectroscopic data. Moreover, Raman data showed better lipid packing and increased lateral order and trans conformation for the SLBs with increasing the curvature of the underlying support and decrease of the gauche kinks for the terminal methyl groups at the center of the bilayer. These results were consistent with a model in which the high free volume and increased outer headgroup spacing of lipids on highly curved surfaces induced interdigitation in the supported lipids. These results also support the symmetric lipid exchange studies of the SLBs as a function of the curvature, which was found to be slower on surfaces with higher curvature. Further, the effect of surface properties on the formation of SLBs was studied by changing the silanol density on the surface of SiO2 via thermal/chemical treatment and monitoring fusion of zwitterionic lipids onto silica (SiO2) nanoparticles. Our findings showed that the formation of SLBs was faster on the surfaces with lower silanol density and concomitantly less bound water compared to surfaces with higher silanol density and more bound water. Since the two SiO2 nanoparticles were similar in other respects, in particular their size and charge (ionization), as determined by zeta potential measurements, differences in electrostatic interactions between the neutral DMPC and SiO2 could not account for the difference. Therefore the slower rate of SLB formation of DMPC onto SiO2 nanoparticles with higher silanol densities and more bound water was attributed to greater hydration repulsion of the more hydrated nanoparticles. Lastly, we have investigated the effect and modulation of the surface charge of vesicles on the formation of SLBs by using different ratios of zwitterionic and cationic DMPC/DMTAP lipids. Through these studies we discovered a procedure by which assemblies of supported lipid bilayer nanoparticles, composed of DMPC/DMTAP (50/50) lipids on SiO2, can be collected and released from bilayer sacks as a function of the phase transition of these lipids. The lipids in these sacks and SLBs could be exchanged by lipids with lower Tm via lipid transfer.
ADA complianceFor Americans with Disabilities Act (ADA) accommodation, including help with reading this content, please contact firstname.lastname@example.org
Showing items related by title, author, creator and subject.
Controlling DNA compaction with cationic amphiphiles for efficient delivery systems-A step forward towards non-viral Gene TherapyWunder, Stephanie L.; Nicholson, Allen W.; Varnum, Susan A.; Ilies, Marc A. (Temple University. Libraries, 2012)The synthesis of pyridinium cationic lipids, their counter-ion exchange, and the transfection of lipoplexes consisting of these lipids with firefly luciferase plasmid DNA (6.7 KDa), into lung, prostate and breast cancer cell lines was investigated. The transfection ability of these newly synthesized compounds was found to be twice as high as DOTAP/cholesterol and LipofectamineTM (two commercially available successful transfection agents). The compaction of the DNA onto silica (SiO2) nanoparticles was also investigated. For this purpose, it was necessary to study the stability and fusion studies of colloidal systems composed of DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine), a zwitterionic lipid, and mixtures of DMPC with cationic DMTAP (1,2-dimyristoyl-3-trimethylammonium-propane).
Reducing Wound Hemorrhage: Use of Bilayer Collagen Matrix in Chronic Myelogenous LeukemiaLo, Alexis L.; Tyrell, Richard O.; Golarz, Scott R.; Jones, Christine M. (2019-11-27)Summary: Donor site preparation is a critical step before the application of an autologous split-thickness skin graft (STSG). Comorbidities can lead to complications and graft loss, including that due to hematoma. In this case, a bilayer collagen matrix was used as a temporary wound dressing in a 25-year-old woman with active chronic myelogenous leukemia. She presented with a bleeding diathesis and spontaneous intramuscular and intracompartmental hematomas of the right leg. She experienced ongoing high-volume blood loss from her fasciotomy wounds, requiring wound care to be performed in the operating room under general anesthesia, and requiring multiple blood and platelet transfusions. Instead of immediate STSG, a bilayer collagen matrix was placed to reduce the bleeding and further prepare the wound bed over a 9-week period while she underwent medical optimization. Once stabilized from a hematologic standpoint, STSG was performed with total graft take. Both uncontrolled chronic myelogenous leukemia and its therapy, tyrosine kinase inhibitors, have a risk of hemorrhagic and thrombotic complications. Bilayer collagen matrix serves as an adjunct in the limb salvage algorithm that can reduce transfusion needs whereas a temporary bleeding diathesis is medically corrected before the application of an autologous skin graft.
Topographic cues of a novel bilayered scaffold modulate dental pulp stem cells differentiation by regulating YAP signalling through cytoskeleton adjustmentsDu, Y; Montoya, C; Orrego, S; Wei, X; Ling, J; Lelkes, PI; Yang, M; Lelkes, Peter|0000-0003-4954-3498 (2019-11-01)© 2019 The Authors. Cell Proliferation Published by John Wiley & Sons Ltd. Objectives: Topographic cues can modulate morphology and differentiation of mesenchymal stem cells. This study aimed to determine how topographic cues of a novel bilayered poly (lactic-co-glycolic acid) (PLGA) scaffold affect osteogenic/odontogenic differentiation of dental pulp stem cells (DPSCs). Methods: The surface morphology of the scaffolds was visualized by scanning electron microscope, and the surface roughness was measured by profilometry. DPSCs were cultured on each side of the scaffolds. Cell morphology, expression of Yes-associated protein (YAP) and osteogenic/odontogenic differentiation were analysed by immunohistochemistry, real-time polymerase chain reaction, and Alizarin Red S staining. In addition, cytochalasin D (CytoD), an F-actin disruptor, was used to examine the effects of F-actin on intracellular YAP localisation. Verteporfin, a YAP transcriptional inhibitor, was used to explore the effects of YAP signalling on osteogenic/odontogenic differentiation of DPSCs. Results: The closed side of our scaffold showed smaller pores and less roughness than the open side. On the closed side, DPSCs exhibited enhanced F-actin stress fibre alignment, larger spreading area, more elongated appearance, predominant nuclear YAP localization and spontaneous osteogenic differentiation. Inhibition of F-actin alignments was correlated with nuclear YAP exclusion of DPSCs. Verteporfin restricted YAP localisation to the cytoplasm, down-regulated expression of early osteogenic/odontogenic markers and inhibited mineralization of DPSCs cultures. Conclusions: The surface topographic cues changed F-actin alignment and morphology of DPSCs, which in turn regulated YAP signalling to control osteogenic/odontogenic differentiation.