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Gamage NDH, Mei Y, Garcia J, Allen MJ. Oxidatively stable, aqueous europium(II) complexes through steric and electronic manipulation of cryptand coordination chemistry. Angew Chem Int Ed Engl 2011; 49:8923-5. [PMID: 20927788 DOI: 10.1002/anie.201002789] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Rasool HI, Song EB, Allen MJ, Wassei JK, Kaner RB, Wang KL, Weiller BH, Gimzewski JK. Continuity of graphene on polycrystalline copper. NANO LETTERS 2011; 11:251-256. [PMID: 21117698 DOI: 10.1021/nl1036403] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The atomic structure of graphene on polycrystalline copper substrates has been studied using scanning tunneling microscopy. The graphene overlayer maintains a continuous pristine atomic structure over atomically flat planes, monatomic steps, edges, and vertices of the copper surface. We find that facets of different identities are overgrown with graphene's perfect carbon honeycomb lattice. Our observations suggest that growth models including a stagnant catalytic surface do not apply to graphene growth on copper. Contrary to current expectations, these results reveal that the growth of macroscopic pristine graphene is not limited by the underlying copper structure.
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Mei Y, Dissanayake P, Allen MJ. A new class of ligands for aqueous, lanthanide-catalyzed, enantioselective Mukaiyama aldol reactions. J Am Chem Soc 2011; 132:12871-3. [PMID: 20806902 DOI: 10.1021/ja107197p] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The development of aqueous methods for generating enantiopure β-hydroxy carbonyl compounds is an important goal because these subunits compose many bioactive compounds and the ability to synthesize these groups in water has environmental and cost benefits. In this communication, we report a new class of ligands for aqueous, lanthanide-catalyzed, asymmetric Mukaiyama aldol reactions for the synthesis of chiral β-hydroxy ketones. Furthermore, we have used luminescence-decay measurements to unveil mechanistic information regarding the catalytic reaction via changes in water-coordination number. The precatalysts presented here yielded β-hydroxy carbonyls from aliphatic and aryl substrates with outstanding syn:anti ratios and enantiometric excesses of up to 49:1 and 97%, respectively.
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Gamage NDH, Mei Y, Garcia J, Allen MJ. Oxidatively Stable, Aqueous Europium(II) Complexes through Steric and Electronic Manipulation of Cryptand Coordination Chemistry. Angew Chem Int Ed Engl 2010. [DOI: 10.1002/ange.201002789] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Arrington SA, Fisher ER, Willick GE, Mann KA, Allen MJ. Anabolic and antiresorptive drugs improve trabecular microarchitecture and reduce fracture risk following radiation therapy. Calcif Tissue Int 2010; 87:263-72. [PMID: 20563797 DOI: 10.1007/s00223-010-9390-z] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2010] [Accepted: 05/30/2010] [Indexed: 11/30/2022]
Abstract
Many patients with symptomatic bone metastases receive radiation therapy, even though radiation is known to have potential adverse effects on bone. We hypothesized that the concurrent use of a bisphosphonate drug (zoledronic acid, ZA) or a combination of ZA plus an anabolic agent (parathyroid hormone, PTH) would lead to improvements in the microarchitecture and mechanical properties of irradiated bone. Human breast cancer cells were injected into the distal femur of 56 female nude mice, which were then divided into four groups: no treatment (0 Gy), radiation administered 4 weeks postinjection (20 Gy), radiation plus ZA (12.5 microg/kg weekly from weeks 4 to 12) (20 Gy + ZA), and radiation followed by ZA (25 microg/kg weekly from weeks 4 to 8) and PTH(1-34) (100 microg microg/kg daily from weeks 8 to 12) (20 Gy + ZA + PTH). Left limbs served as normal control bones. Bone loss over the 12-week study was tracked with serial radiography and bone densitometry. At the end of the study, micro-computed tomography and mechanical testing were used to quantify bone microarchitecture and bone strength. Radiation alone failed to prevent tumor-induced decreases in bone mineral density (BMD), trabecular bone volume, and bone strength. Treatment with 20 Gy + ZA or 20 Gy + ZA + PTH as adjuncts to radiation was effective at preserving trabecular bone architecture and bone strength at normal levels. ZA reduced the risk of mechanical fragility following irradiation of a lytic bone lesion. Supplemental use of PTH did not result in further increases in bone strength but was associated with significant increases in BMD and bone mass, suggesting that it may be beneficial in enhancing bone architecture following radiation therapy.
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Allen MJ, Leone KA, Lamonte K, Townsend KL, Mann KA. Cemented total knee replacement in 24 dogs: surgical technique, clinical results, and complications. Vet Surg 2009; 38:555-67. [PMID: 19573056 DOI: 10.1111/j.1532-950x.2009.00528.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
OBJECTIVE To characterize the performance of cemented total knee replacement (TKR) in dogs. STUDY DESIGN Preclinical research study. ANIMALS Skeletally mature, male Hounds (25-30 kg; n=24) with no preexisting joint pathology. METHODS Dogs had unilateral cemented TKR and were evaluated at 6, 12, 26, or 52 weeks (6 dogs/time point) by radiography, bone density analysis, visual gait assessment, and direct measurement of thigh circumference and stifle joint range of motion as indicators of functional recovery. At study end, the stability of the cemented tibial component was determined by destructive mechanical testing. RESULTS Joint stability was excellent in 16 dogs (67%) and good in 8 dogs. None of the tibial components had evidence of migration or periprosthetic osteolysis whereas 1 femoral component was loose at 52 weeks. There was an early and significant decrease in tibial bone density, likely because of disuse of the operated limb. Dogs returned to full activity by 12 weeks. The tibial cement-bone interface maintained its strength over 52 weeks. CONCLUSIONS Cement provides stable fixation of the tibial component in canine TKR. CLINICAL RELEVANCE Cemented TKR yields adequate clinical function and stifle joint excursion in the dog. Clinical studies are needed to determine the long-term fate of cemented TKR implants, to assess the influence of implant design on implant fixation and wear, and to obtain objective functional data.
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Allen MJ, Wang M, Jannuzzi SAV, Yang Y, Wang KL, Kaner RB. Chemically induced folding of single and bilayer graphene. Chem Commun (Camb) 2009:6285-7. [PMID: 19826696 DOI: 10.1039/b911972h] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Here we report chemically induced folding of thin graphene flakes. The folding occurs spontaneously when an intercalating species interrupts the adhesion between graphene and a supporting substrate. The morphology of induced folds suggests that the conjugated pi network is capable of extremely sharp curvature. Adjacent folds are often parallel, suggesting preferential deformation along certain crystallographic planes.
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Losquadro WD, Tatum SA, Allen MJ, Mann KA. Polylactide-co-glycolide fiber-reinforced calcium phosphate bone cement. ACTA ACUST UNITED AC 2009; 11:104-9. [PMID: 19289682 DOI: 10.1001/archfacial.2008.512] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
OBJECTIVE To compare the strength of polylactide-co-glycolide fiber-reinforced calcium phosphate bone cement (FRC) with nonreinforced calcium phosphate bone cement (NRC) subjected to simulated dural pulsations in defects larger than 25 cm(2). METHODS Seven NRC and 7 FRC specimens were set in both medium (37.5 cm(2)) and large (50.0 cm(2)) model skull defects while subjected to simulated dural pulsations. Specimens were removed after 24 hours and analyzed using 3-point flexural testing. RESULTS All 14 FRC specimens maintained structural integrity during extraction and testing. Only 2 of 7 (29%) medium specimens and 2 of 7 (29%) large NRC specimens survived setting. The mean (SD) energy to peak force (in newton millimeters [Nmm]) of the medium and large NRC specimens was 0.88 (0.83) and 3.00 (3.54) Nmm, respectively, compared with 28.97 (16.52) and 49.91 (38.10) Nmm for the medium and large FRC specimens. The material strength (in megapascals) of the medium and large NRC specimens was 0.17 (0.15) and 0.39 (0.33) MPa, respectively, compared with 3.73 (0.99) and 2.62 (1.34) MPa for the medium and large FRC specimens. The energy to peak force and material strength of the medium and large FRC specimens were significantly greater than for the corresponding NRC specimens; results were not statistically significant between medium and large FRC specimens. CONCLUSIONS Fiber-reinforced calcium phosphate bone cement exhibits superior structural integrity and material strength than NRC when subjected to unshielded simulated dural pulsations. Further studies are needed to evaluate the biophysical parameters of FRC in vivo.
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Allen MJ, Wangkanont K, Raines RT, Kiessling LL. ROMP from ROMP: A New Approach to Graft Copolymer Synthesis. Macromolecules 2009; 42:4023-4027. [PMID: 20161406 DOI: 10.1021/ma900056b] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A new strategy is presented for the synthesis of graft copolymers using only the ring-opening metathesis polymerization (ROMP). From a ROMP-derived main chain, pendant maleimide functional groups are converted into norbornene moieties via a Diels-Alder reaction with cyclopentadiene. The norbornene groups serve as sites of initiation, and subsequent ROMP from the main chain yields graft copolymers with both main and side chains derived from ROMP. This strategy offers ready access to defined graft copolymers.
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Dissanayake P, Allen MJ. Dynamic measurements of aqueous lanthanide triflate-catalyzed reactions using luminescence decay. J Am Chem Soc 2009; 131:6342-3. [PMID: 19385628 PMCID: PMC2750840 DOI: 10.1021/ja900630d] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
There is tremendous interest in water-compatible lanthanide triflate-based catalysts for carbon-carbon bond forming reactions; however, poor understanding of their aqueous mechanism severely limits the ability to increase the utility of these catalysts. Here, we report dynamic measurements of the water-coordination number of lanthanide triflate-based catalysts using luminescence-decay measurements in a range of aqueous systems. This unique characterization method is a reliable, convenient, and fast approach to analyze lanthanide-based catalysts in aqueous systems.
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Tung VC, Chen LM, Allen MJ, Wassei JK, Nelson K, Kaner RB, Yang Y. Low-temperature solution processing of graphene-carbon nanotube hybrid materials for high-performance transparent conductors. NANO LETTERS 2009; 9:1949-1955. [PMID: 19361207 DOI: 10.1021/nl9001525] [Citation(s) in RCA: 417] [Impact Index Per Article: 27.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We report the formation of a nanocomposite comprised of chemically converted graphene and carbon nanotubes. Our solution-based method does not require surfactants, thus preserving the intrinsic electronic and mechanical properties of both components, delivering 240 ohms/square at 86% transmittance. This low-temperature process is completely compatible with flexible substrates and does not require a sophisticated transfer process. We believe that this technology is inexpensive, is massively scalable, and does not suffer from several shortcomings of indium tin oxide. A proof-of-concept application in a polymer solar cell with power conversion efficiency of 0.85% is demonstrated. Preliminary experiments in chemical doping are presented and show that optimization of this material is not limited to improvements in layer morphology.
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Fowler JD, Allen MJ, Tung VC, Yang Y, Kaner RB, Weiller BH. Practical chemical sensors from chemically derived graphene. ACS NANO 2009; 3:301-306. [PMID: 19236064 DOI: 10.1021/nn800593m] [Citation(s) in RCA: 567] [Impact Index Per Article: 37.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We report the development of useful chemical sensors from chemically converted graphene dispersions using spin coating to create single-layer films on interdigitated electrode arrays. Dispersions of graphene in anhydrous hydrazine are formed from graphite oxide. Preliminary results are presented on the detection of NO(2), NH(3), and 2,4-dinitrotoluene using this simple and scalable fabrication method for practical devices. Current versus voltage curves are linear and ohmic in all cases, studied independent of metal electrode or presence of analytes. The sensor response is consistent with a charge transfer mechanism between the analyte and graphene with a limited role of the electrical contacts. A micro hot plate sensor substrate is also used to monitor the temperature dependence of the response to nitrogen dioxide. The results are discussed in light of recent literature on carbon nanotube and graphene sensors.
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Wilson WH, Van Etten JL, Allen MJ. The Phycodnaviridae: the story of how tiny giants rule the world. Curr Top Microbiol Immunol 2009; 328:1-42. [PMID: 19216434 DOI: 10.1007/978-3-540-68618-7_1] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The family Phycodnaviridae encompasses a diverse and rapidly expanding collection of large icosahedral, dsDNA viruses that infect algae. These lytic and lysogenic viruses have genomes ranging from 160 to 560 kb. The family consists of six genera based initially on host range and supported by sequence comparisons. The family is monophyletic with branches for each genus, but the phycodnaviruses have evolutionary roots that connect them with several other families of large DNA viruses, referred to as the nucleocytoplasmic large DNA viruses (NCLDV). The phycodnaviruses have diverse genome structures, some with large regions of noncoding sequence and others with regions of ssDNA. The genomes of members in three genera in the Phycodnaviridae have been sequenced. The genome analyses have revealed more than 1000 unique genes, with only 14 homologous genes in common among the three genera of phycodnaviruses sequenced to date. Thus, their gene diversity far exceeds the number of so-called core genes. Not much is known about the replication of these viruses, but the consequences of these infections on phytoplankton have global affects, including influencing geochemical cycling and weather patterns.
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Tung VC, Allen MJ, Yang Y, Kaner RB. High-throughput solution processing of large-scale graphene. NATURE NANOTECHNOLOGY 2009; 4:25-9. [PMID: 19119278 DOI: 10.1038/nnano.2008.329] [Citation(s) in RCA: 912] [Impact Index Per Article: 60.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2008] [Accepted: 10/16/2008] [Indexed: 05/19/2023]
Abstract
The electronic properties of graphene, such as high charge carrier concentrations and mobilities, make it a promising candidate for next-generation nanoelectronic devices. In particular, electrons and holes can undergo ballistic transport on the sub-micrometre scale in graphene and do not suffer from the scale limitations of current MOSFET technologies. However, it is still difficult to produce single-layer samples of graphene and bulk processing has not yet been achieved, despite strenuous efforts to develop a scalable production method. Here, we report a versatile solution-based process for the large-scale production of single-layer chemically converted graphene over the entire area of a silicon/SiO(2) wafer. By dispersing graphite oxide paper in pure hydrazine we were able to remove oxygen functionalities and restore the planar geometry of the single sheets. The chemically converted graphene sheets that were produced have the largest area reported to date (up to 20 x 40 microm), making them far easier to process. Field-effect devices have been fabricated by conventional photolithography, displaying currents that are three orders of magnitude higher than previously reported for chemically produced graphene. The size of these sheets enables a wide range of characterization techniques, including optical microscopy, scanning electron microscopy and atomic force microscopy, to be performed on the same specimen.
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Margulies BS, Damron TA, Allen MJ. The differential effects of the radioprotectant drugs amifostine and sodium selenite treatment in combination with radiation therapy on constituent bone cells, Ewing's sarcoma of bone tumor cells, and rhabdomyosarcoma tumor cells in vitro. J Orthop Res 2008; 26:1512-9. [PMID: 18473385 DOI: 10.1002/jor.20679] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The purpose of this study was to determine the differential effects of therapeutic X-radiation on constituent bone cells relative to the pediatric tumor cells: Ewing's sarcoma of bone and rhabdomyosarcoma. In addition, the radioprotectant drugs amifostine and sodium selenite were administered to constituent bone cells and the two tumor cells to determine if the radioprotectants differentially protect bone cells while not benefiting the tumor cells. These studies are a necessary first step in determining the potential clinical benefit of radioprotective therapy. An established in vitro cell culture model employing both constituent bone cells (osteoblasts, primary bone marrow monocytes, osteoclasts chondrocytes, and endothelial cells) and the tumor cells lines (Ewing's sarcoma of bone and rhabdomyosarcoma) were exposed to irradiation, amifostine, and sodium selenite. Cells were then assayed for changes in cell number, cytotoxicity, mineralization, bone resorption, cell attachment, osteocalcin, caspase-3 expression, clonogenic survival, and alkaline phosphatase expression. Radiation therapy differentially decreased cell number; with osteoblasts being shown to be the least sensitive to irradiation, the tumor cells had an intermediate sensitivity and monocytes were the most sensitive. Both amifostine and sodium selenite protected chondrocytes and osteoblasts from the negative effects of irradiation, while not protecting the tumor cells. The pediatric tumor cell lines were generally more radiosensitive than the bone cells examined. The radioprotectant drugs amifostine and sodium selenite provided significant radioprotection to constituent bone cells while not protecting the tumor cells. Finally, amifostine and sodium selenite therapy provided an additional benefit beyond radioprotection by increasing cytotoxicity in nonirradiated and irradiated tumor cells.
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Mann KA, Lee J, Arrington SA, Damron TA, Allen MJ. Predicting distal femur bone strength in a murine model of tumor osteolysis. Clin Orthop Relat Res 2008; 466:1271-8. [PMID: 18404290 PMCID: PMC2384034 DOI: 10.1007/s11999-008-0241-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2007] [Accepted: 03/17/2008] [Indexed: 01/31/2023]
Abstract
Predicting pathologic fractures of long bones caused by metastatic disease continues to be a challenging clinical problem. We assessed the ability of noninvasive imaging and computational techniques to predict the strength of bones with osteolytic lesions. A murine model of induced tumor osteolysis to the distal femur was used as a model system resulting in a wide range of lesion sizes. Microcomputed tomography scans were obtained and specimen-specific, voxel-based, finite element analyses were performed and results were compared with direct measurement of biomechanical strength via axial compressive loading of the distal femur. Additional indirect surrogates of bone strength included dual-energy xray absorptiometry to determine bone mineral density, radiographic scoring, and computed tomography volume/mineral estimates. Predicted bone strength was weakest (r(2) = 0.55) for the dual-energy xray absorptiometry measure and strongest (r(2) = 0.91) for the direct computed tomography voxel-based, finite element analysis. The relative success of the voxel-based, finite element modeling approach to estimate bone strength in a murine osteolytic tumor model indicates this approach, with further development and validation, could serve as a way to nondestructively estimate bone strength in a clinical setting.
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Allen MJ, Bunce C, Presland AH. The effect of warming local anaesthetic on the pain of injection during sub-Tenon's anaesthesia for cataract surgery. Anaesthesia 2008; 63:276-8. [PMID: 18289234 DOI: 10.1111/j.1365-2044.2007.05351.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
In a double blind, randomised controlled trial, we examined the effect of warming local anaesthetic solutions on the pain experienced by patients undergoing a sub-Tenon's block for cataract surgery. In all, 140 patients were randomly allocated to receive either local anaesthetic stored at room temperature (control group) or local anaesthetic warmed to 37 degrees C (study group). Pain scores were assessed using a verbal analogue scale from 0 to 10. There was no significant difference in pain scores between the two groups. We conclude that the practice of warming local anaesthetic prior to performing a sub-Tenon's block does not significantly reduce the amount of pain experienced by patients.
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Arrington SA, Damron TA, Mann KA, Allen MJ. Concurrent administration of zoledronic acid and irradiation leads to improved bone density, biomechanical strength, and microarchitecture in a mouse model of tumor-induced osteolysis. J Surg Oncol 2008; 97:284-90. [DOI: 10.1002/jso.20949] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Allen MJ, Turner AS, Sairyo K, Ferrara L. Basic Science Symposium III: Animal Models for Orthopaedic Implant Evaluation. Int J Spine Surg 2008; 2:195-200. [PMID: 25802622 PMCID: PMC4365662 DOI: 10.1016/sasj-2008-symposium4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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147
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Allen MJ, Raines RT, Kiessling LL. Contrast agents for magnetic resonance imaging synthesized with ring-opening metathesis polymerization. J Am Chem Soc 2007; 128:6534-5. [PMID: 16704234 DOI: 10.1021/ja061383p] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A monomer for ring-opening metathesis polymerization (ROMP) has been developed that also functions as a portion of a GdIII chelating moiety for a magnetic resonance imaging contrast agent. An increase in per GdIII relaxivity was shown upon transition from monomer to polymer. Additionally, extremely large molecular relaxivities were achieved through incorporation of multiple GdIII ions per polymer. The nature of ROMP-derived polymers allows for functionalization of the monomer units and termini through orthogonal chemistry. This strategy is the basis for a new class of highly sensitive, targeted imaging agents.
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Allen MJ, Leone KA, Hasenwinkel JM, Gilbert JL. Tissue response toin situ polymerization of a new two-solution bone cement: Evaluation in a sheep model. J Biomed Mater Res B Appl Biomater 2006; 79:441-52. [PMID: 16615074 DOI: 10.1002/jbm.b.30559] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
A two-solution bone cement (2-SC) was evaluated in a non-load bearing sheep model that simulated insertion of a cemented total joint replacement. A commercial powder-liquid bone cement formulation (Palacos R) was used as the control. The systemic response to the two cements was determined by monitoring changes in arterial blood pressure (ABP) and serum concentrations of methyl methacrylate monomer at intervals after insertion of the cement. The short-term tissue response to the two cements was assessed by quantifying histomorphometric parameters of new bone formation at 2, 4, and 12 weeks postsurgery. Intraoperatively, injection and pressurization of bone cement were well tolerated, with no significant changes in ABP in either group and no detectable circulating monomer in any animal. Several interesting trends were identified in the histomorphometry data. In the trabecular specimens, new bone formation immediately adjacent to the cement mantle was apparently suppressed in the first 2 weeks postsurgery, increased dramatically at 4 weeks, and then returned to baseline values by 12 weeks. This pattern was seen with both Palacos and 2-SC. In the cortical specimens, new bone formation was reduced on the endosteal surface when compared with the periosteal surface, with this effect being more noticeable at 2 and 4 weeks than at 12 weeks. There were no significant histopathological findings in either the bone or the draining lymph nodes. These data indicate that the biological response to 2-SC is substantially equivalent to that of Palacos R. Additional testing in a functional, load-bearing animal model is now recommended to more fully characterize the long-term biological response to 2-SC and to determine the mechanical performance of this new cement in vivo.
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Endres PJ, Macrenaris KW, Vogt S, Allen MJ, Meade TJ. Quantitative imaging of cell-permeable magnetic resonance contrast agents using x-ray fluorescence. Mol Imaging 2006; 5:485-97. [PMID: 17150161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2023] Open
Abstract
The inability to transduce cellular membranes is a limitation of current magnetic resonance imaging probes used in biologic and clinical settings. This constraint confines contrast agents to extracellular and vascular regions of the body, drastically reducing their viability for investigating processes and cycles in developmental biology. Conversely, a contrast agent with the ability to permeate cell membranes could be used in visualizing cell patterning, cell fate mapping, gene therapy, and, eventually, noninvasive cancer diagnosis. Therefore, we describe the synthesis and quantitative imaging of four contrast agents with the capability to cross cell membranes in sufficient quantity for detection. Each agent is based on the conjugation of a Gd(III) chelator with a cellular transduction moiety. Specifically, we coupled Gd(III)-diethylenetriaminepentaacetic acid DTPA and Gd(III)-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid with an 8-amino acid polyarginine oligomer and an amphipathic stilbene molecule, 4-amino-4'-(N,N-dimethylamino)stilbene. The imaging modality that provided the best sensitivity and spatial resolution for direct detection of the contrast agents is synchrotron radiation x-ray fluorescence (SR-XRF). Unlike optical microscopy, SR-XRF provides two-dimensional images with resolution 10(3) better than (153)Gd gamma counting, without altering the agent by organic fluorophore conjugation. The transduction efficiency of the intracellular agents was evaluated by T(1) analysis and inductively coupled plasma mass spectrometry to determine the efficacy of each chelate-transporter combination.
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Endres PJ, MacRenaris KW, Vogt S, Allen MJ, Meade TJ. Quantitative Imaging of Cell-Permeable Magnetic Resonance Contrast Agents Using X-Ray Fluorescence. Mol Imaging 2006. [DOI: 10.2310/7290.2006.00026] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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