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Browsing by Author "Minner, Daniel E."
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Item Functionalization of Polymeric Beads as Optical Reporters of Biomembrane Mimicking Cell Substrate Properties(Office of the Vice Chancellor for Research, 2013-04-05) Moretti, Leandro; Minner, Daniel E.; Herring, Vincent L.; Naumann, Christoph A.Novel biomembrane-mimicking cell substrates based on a polymer-tethered multi-lipid bilayer stack have been recently developed in the Naumann lab. These novel substrates have been shown to induce profound changes in cellular behavior dependent on the number of bilayers in the stack. However, the underlying mechanical substrate properties remain unclear. To overcome this problem, the central goal of my research is the development of a nanoparticle-based optical reporter that provides insight into the dynamic and viscoelastic properties of the multibilayer system. To achieve this goal, fluorescent polystyrene beads and magnetic polystyrene beads were functionalized for use in confocal microscopy and magnetic tweezers (MT) assays, respectively. Both kinds of beads were specifically tailored and functionalized to link the bilayer system to cellular adhesion proteins recognized by plated cells, thus acting as fluorescent cell-substrate linkages. To assure the correct surface functionalization of nanoparticles, Zetasizer assays were run on both kinds of beads to verify expected changes in hydrodynamic radius and zeta potential as reactions progressed. Fluorescent beads were specifically linked to lipid bilayers using maleimide-thiol coupling chemistry, thus allowing subsequent experiments in the presence of plated cells. As confirmed by analysis of cellular nanoparticle uptake, the cellular uptake kinetics of the newly synthesized fluorescent beads could be controlled through adjustment of nanoparticle coating composition. These results are significant because they validate the new nanobead design, which shows enhanced reporter efficiency for confocal microscopy and MT based assays.Item Osteocytic perilacunar/canalicular turnover in hemodialysis patients with high and low serum PTH levels(Elsevier, 2018-08) Yajima, Aiji; Tsuchiya, Ken; Burr, David B.; Minner, Daniel E.; Condon, Keith W.; Miller, Caroline A.; Satoh, Shigeru; Inaba, Masaaki; Nakayama, Takashi; Tanizawa, Tatsuhiko; Ito, Akemi; Nitta, Kosaku; Anatomy and Cell Biology, IU School of MedicineOsteocytic perilacunar/canalicular turnover in hemodialysis patients has not yet been reported. Osteocyte lacunae in lamellar bone and woven bone were classified as eroded surface-, osteoid surface-, and quiescent surface-predominant osteocyte lacunae (ES-Lc, OS-Lc, QS-Lc, respectively) in 55 hemodialysis patients with either high- (n = 45) or low- (n = 10) parathyroid hormone levels, and 19 control subjects without chronic kidney disease. We calculated the area and number of ES-Lc, OS-Lc, and QS-Lc. The mineralized surface on the osteocyte lacunar walls was measured in each group, and compared among the three groups. The shapes of the osteocyte lacunar walls were validated by backscattered electron microscopy. While the number of ES-Lc per bone area (N.ES-Lc/B.Ar) was higher than the number of OS-Lc per bone area (N.OS-Lc/B.Ar) in all groups, N.ES-Lc/B.Ar and N.OS-Lc/B.Ar were greater in high-parathyroid hormone group than in low-parathyroid hormone and control groups. The total volume of ES-Lc per bone area (ES-Lc.Ar/B.Ar) was greater than the total volume of OS-Lc per bone area (OS-Lc.Ar/B.Ar) in both parathyroid hormone groups. However, both lacunar erosion and lacunar formation increased proportionally, suggesting that global coupling between them was maintained. N.ES-Lc/B.Ar was higher in woven bone than in lamellar bone. The rate of OS-Lc stained by tetracycline hydrochloride, the mineralized lacunar surface and the mean area of OS-Lc with Tc obtained from both parathyroid hormone groups were greater than those in the control group. We conclude that osteocytic perilacunar/canalicular turnover is increased in hemodialysis patients with high parathyroid hormone levels. Osteocytic perilacunar/canalicular turnover depends, at least in part, on serum parathyroid hormone level. However, the ideal PTH level for osteocytic perilacunar/canalicular turnover could not be determined but osteocytic osteolysis was predominant in both the high- and low-PTH groups in this study. Thus, attention should be paid to bone loss from the viewpoint of osteocytic perilacunar/canalicular turnover in hemodialysis patients.Item Physisorbed Polymer-Tethered Lipid Bilayer with Lipopolymer Gradient(MDPI, 2012-11) Lin, Yu-Hung; Minner, Daniel E.; Herring, Vincent L.; Naumann, Christoph A.; Chemistry and Chemical Biology, School of SciencePhysisorbed polymer-tethered lipid bilayers consisting of phospholipids and lipopolymers represent an attractive planar model membrane platform, in which bilayer fluidity and membrane elastic properties can be regulated through lipopolymer molar concentration. Herein we report a method for the fabrication of such a planar model membrane system with a lateral gradient of lipopolymer density. In addition, a procedure is described, which leads to a sharp boundary between regions of low and high lipopolymer molar concentrations. Resulting gradients and sharp boundaries are visualized on the basis of membrane buckling structures at elevated lipopolymer concentrations using epifluorescence microscopy and atomic force microscopy. Furthermore, results from spot photobleaching experiments are presented, which provide insight into the lipid lateral fluidity in these model membrane architectures. The presented experimental data highlight a planar, solid-supported membrane characterized by fascinating length scale-dependent dynamics and elastic properties with remarkable parallels to those observed in cellular membranes.