20 results on '"Bender JD"'
Search Results
2. Cardiac Dysfunction in Children and Young Adults Treated With MEK Inhibitors: A Retrospective, Single-Center Study.
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Bender JD, Pillay-Smiley N, Hill GD, de Blank P, Hummel TR, Weiss BD, Kumar A, Zang H, Ollberding NJ, and Ryan TD
- Abstract
Competing Interests: This publication was supported by an institutional Clinical and Translational Science Award, National Institutes of Health/National Center for Advancing Translational Sciences (grant 1UL1TR001425) through the University of Cincinnati. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the National Institutes of Health. This work was additionally supported by divisional funding from the Heart Institute, Cincinnati Children’s Hospital Medical Center. This work was completed in partial fulfillment of the Master of Science degree in Clinical and Translational Research in the Division of Epidemiology, University of Cincinnati College of Medicine. Dr Hill serves as a consultant for Ultragenyx. Dr De Blank has served as an Advisory Board member for Alexion Pharmaceuticals for selumetinib. Dr Kumar serves as a consultant for Sobi. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
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- 2024
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3. Evolution of the availability of Information and Communication Technologies in primary health care in Brazil, 2012 to 2018.
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Bender JD, Facchini LA, Lapão LMV, Tomasi E, and Thumé E
- Subjects
- Brazil, Cross-Sectional Studies, Humans, Health Services Accessibility statistics & numerical data, Information Technology statistics & numerical data, Quality Improvement, Primary Health Care
- Abstract
Objective: To verify the evolution of the availability of information and communication technology equipment and inputs in primary health care services that participated in the external evaluation of the Access and Quality Improvement Program in Primary Care and its distribution according to context characteristics social and geographic., Methods: Cross-sectional study, analyzed the distribution of information and communication technology equipment in basic health units in Brazil, during the three cycles (2012 to 2018) of the Program for Improving Access and Quality in Primary Care. The variables were examined at the municipal level and stratified by geopolitical region. Univariate analysis was performed, using the chi-square test and testing the distributions of exposures among themselves and between the outcome and exposures., Results: The availability of information and communication technology equipment increased from 9.4% (2012) to 17.5% (2018), with emphasis on the Southeast and South regions, in municipalities with a population size of up to 10,000 inhabitants², with greater family health coverage and high/very high HDI-M. Over the period from 2012 to 2018, basic units joined the program and increased availability of information and communication technologies, such as Internet access, which ranged from 45.2% (n=6,249) to 74.0% (n=21,423), with emphasis on the Northeast region, which increased from 19.1% (n=970) to 58.8% (n=7,087)., Conclusion: Investment in technologies and constant evaluation of primary care in the country is necessary, contributing to its strengthening.
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- 2024
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4. The use of Information and Communication Technologies in Primary Health Care in Brazil - the period of 2014 to 2018.
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Bender JD, Facchini LA, Lapão LMV, Tomasi E, and Thumé E
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- Humans, Brazil, Cross-Sectional Studies, Primary Health Care, Communication, Education, Continuing
- Abstract
Information and Communication Technologies in Health allow the storage and processing of digital data, access to information and remote communications. The objective of this article was to describe the use of these Technologies to support clinical practice and continuing education by primary health care teams in Brazil the period of 2014 to 2018, within the scope of the Access and Quality Improvement Program Basic, according to characteristics of the geopolitical context. It's a cross-sectional study that analyzed the data collected from the teams of the Basic Health Units. A growing use by the teams of Telehealth resources, the Telemedicine University Network and the Open University of the Unified Health System was observed to aid clinical practice and permanent health education. In the North and Northeast regions, the use of these Technologies doubled, from cycle II to cycle III. The need for investments in infrastructure, human resources in Primary Health Care, qualification and professional training is a way to strengthen the Unified Health System and its Health Care Network, contributing to a continuous flow of care, with quality and access universal.
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- 2024
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5. Use of gemcitabine, oxaliplatin, and anti-CD20 therapy in children and adolescents with non-Hodgkin lymphoma unfit for intensive therapy.
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Bender JD, Rubinstein JD, Mizukawa B, Perentesis JP, and Pommert L
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- Adult, Humans, Child, Adolescent, Aged, Rituximab, Oxaliplatin, Retrospective Studies, Antineoplastic Combined Chemotherapy Protocols therapeutic use, Deoxycytidine, Treatment Outcome, Gemcitabine, Lymphoma, Non-Hodgkin drug therapy
- Abstract
Multiagent immunochemotherapy affords excellent outcomes in pediatric non-Hodgkin lymphoma (NHL); however, scarce data exist for patients unfit for intensive treatment. Rituximab, gemcitabine, and oxaliplatin (R-GemOx) is well tolerated and efficacious in elderly adults with NHL; however, its use has not been described in pediatrics. In this retrospective, single-center study, six children with mature B-cell NHL and significant comorbidities received anti-CD20 therapy with GemOx (rituximab or obinutuzumab or ofatumumab with gemcitabine and oxaliplatin [R/O-GemOx]). R/O-GemOx was well tolerated and resulted in complete response in two of three patients with newly diagnosed NHL and one of three patients with primary refractory NHL. R/O-GemOx is a viable treatment option for children with NHL who cannot tolerate intensive therapy., (© 2023 Wiley Periodicals LLC.)
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- 2023
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6. Reduced-Intensity Conditioning Mitigates Risk for Primary Ovarian Insufficiency but Does Not Decrease Risk for Infertility in Pediatric and Young Adult Survivors of Hematopoietic Stem Cell Transplantation.
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Bender JD, Oquendo-Del Toro H, Benoit J, Howell JC, Badia P, Davies SM, Grimley MS, Jodele S, Phillips C, Burns K, Marsh R, Nelson A, Wallace G, Dandoy CE, Pate A, Strine AC, Frias O, Breech L, Rose SR, Hoefgen H, Khandelwal P, and Myers KC
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- Humans, Male, Child, Female, Young Adult, Adult, Retrospective Studies, Cross-Sectional Studies, Luteinizing Hormone, Follicle Stimulating Hormone, Estradiol, Survivors, Primary Ovarian Insufficiency etiology, Oligospermia, Azoospermia, Hematopoietic Stem Cell Transplantation adverse effects, Hematopoietic Stem Cell Transplantation methods
- Abstract
Hematopoietic stem cell transplantation (HSCT) is a curative therapy for many pediatric malignant and nonmalignant conditions. Gonadal insufficiency or infertility is present in almost all HSCT survivors who received a myeloablative conditioning (MAC) regimen. Reduced-intensity conditioning (RIC) regimens are being increasingly used in medically fragile patients or in patients with nonmalignant diagnoses to limit the toxicities associated with HSCT; however, the short-term and long-term gonadal toxicity of RIC regimens in pediatric and young adult survivors remains unknown. In this study, we compared the prevalence of gonadal insufficiency and infertility among pubertal and postpubertal pediatric and young adult survivors of HSCT who received a RIC regimen versus those who received a MAC regimen. Twenty-three females (RIC, n = 8; MAC, n = 15) and 35 males (RIC, n = 19; MAC, n = 16) were included in this single-center, retrospective cross-sectional study. Eligible patients were those with available laboratory results who were ≥1 year post-HSCT, age <40 years, and pubertal or postpubertal as assessed by an endocrinologist. Follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol, and anti-Müllerian hormone (AMH) levels were measured in females, and FSH, LH, total testosterone, and inhibin B (InhB) levels were measured in males. Twenty-one males (RIC, n = 11; MAC, n = 10) underwent semen analysis through a separate consent. Parametric and nonparametric analyses were undertaken to compare the RIC and MAC groups. Female patients who received RIC were less likely than those who received MAC to develop primary ovarian insufficiency, as demonstrated by elevated FSH (P = .02) and low estradiol (P = .01) or elevated LH (P = .09). Most females in the RIC (75%) and MAC (93%) groups had low AMH levels, indicating low or absent ovarian reserve, with no significant difference between the groups (P = .53). In males, there were no significant differences between the 2 groups in the prevalence of abnormal FSH, LH, testosterone, or InhB levels. Ten of 11 RIC males (91%) and 10 of 10 MAC males (100%) had azoospermia or oligospermia, at a median time to semen analysis from HSCT of 3.7 years (range, 1.3 to 12.2 years). RIC may pose less risk than MAC for primary ovarian insufficiency among female survivors of HSCT; however, both female and male recipients of either RIC or MAC regimens are at high risk for infertility. In the largest reported series of semen analyses of pediatric and young adult male recipients of RIC, azoospermia or oligospermia was found in nearly all (91%) RIC survivors. All patients undergoing HSCT should receive counseling about the high risk of gonadal toxicity, and efforts should be made to preserve fertility in patients undergoing either RIC or MAC., (Copyright © 2022 The American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc. All rights reserved.)
- Published
- 2023
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7. Effect of urinary incontinence on negative self-perception of health and depression in elderly adults: a population-based cohort.
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Kessler M, Volz PM, Bender JD, Nunes BP, Machado KP, Saes MO, Soares MU, Facchini LA, and Thumé E
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- Adult, Aged, Cohort Studies, Female, Humans, Male, Prospective Studies, Self Concept, Depression epidemiology, Urinary Incontinence epidemiology
- Abstract
The scope of this study was to measure the prevalence of negative self-perceived health and depressive symptoms in elderly adults according to the presence of urinary incontinence, after a follow-up of nine years. This is a prospective population-based cohort study entitled Bagé Cohort Study of Aging, from Rio Grande do Sul. A total of 1,593 elderly adults were interviewed in the baseline study (2008) and 735 between September 2016 and August 2017. The "urinary incontinence (UI)" exposure was assessed in the baseline study and the outcomes "negative self-perceived health" and "depressive symptoms" in 2016/17. The odds ratio and 95% confidence interval were calculated by Logistic Regression and adjusted for demographic, social, behavioral and health conditions. The prevalence of UI was 20.7% in 2008 and 24.5% in 2016/17; the incidence was 19.8%, being 23.8% among women and 14.6% among men (p = 0.009). Elderly adults with UI at the baseline study had a 4.0 (CI95%: 1.8-8.8) and a 3.4 (CI95%: 1.8-6.2) greater chance to develop negative self-perception of health and depressive symptoms, respectively, after nine years of follow-up, compared to those without UI. The results show a greater probability of mental problems among elderly adults with UI.
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- 2022
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8. Vertebral osteomyelitis due to Salmonella Poona in a healthy adolescent female.
- Author
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Toofan Y, Tarun S, Bender JD, Auerbach SA, Stewart DA, and Watson ME Jr
- Abstract
We present a case of vertebral osteomyelitis in a previously healthy, adolescent Caucasian female athlete. After months of lower back pain, spinal imaging demonstrated phlegmon and suspected osteomyelitis of the L4 vertebral body. A bone biopsy was obtained, and microbiologic cultures yielded pure growth of Salmonella enterica subsp. enterica serovar Poona ( S . Poona), a member of the nontyphoid Salmonella group associated with food-borne gastroenteritis in the United States. This case represents the first reported association of S . Poona with osteomyelitis and is interesting in that the infection developed in a patient without traditional risk factors for invasive Salmonella disease (i.e. sickle cell disease). This case highlights the importance of keeping a broad differential diagnosis for lower back pain and emphasizes the value of obtaining specimens for microbiologic culture to aid in diagnosing non-traditional and potentially emerging bacterial pathogens., Competing Interests: Declaration of conflicting interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article., (© The Author(s) 2020.)
- Published
- 2020
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9. Health education and promotion actions among teams of the National Primary Care Access and Quality Improvement Program, Rio Grande do Sul state, Brazil.
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Kessler M, Thumé E, Duro SMS, Tomasi E, Siqueira FCV, Silveira DS, Nunes BP, Volz PM, Santos AAD, França SM, Bender JD, Piccinini T, and Facchini LA
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- Brazil, Cross-Sectional Studies, Delivery of Health Care organization & administration, Delivery of Health Care standards, Family Health, Health Services Accessibility, Humans, Patient Care Team organization & administration, Patient Care Team standards, Primary Health Care standards, Health Education methods, Health Promotion methods, Primary Health Care organization & administration, Quality Improvement
- Abstract
Objetivo: to investigate the provision of health education and promotion actions in primary care, and their association with demographic characteristics and Family Health Strategy (FHS) coverage in Rio Grande do Sul state, Brazil., Methods: this is a cross-sectional study conducted with 816 teams that adhered to the 2012 Primary Care Access and Quality Improvement Program., Results: the most frequent actions were directed towards people with diabetes (91.2%), hypertension (90.8%) as well as antenatal and postnatal care (84.6%). The least frequent were directed to wards crack, alcohol and other drug users (32.4%), anxiolytic/benzodiazepine users (20.3%), people with tuberculosis (31.4%) and leprosy (21.0%). The greatest provision of health promotion and education actions occurred in smaller municipalities and with greater Family Health coverage., Conclusion: actions aimed at the reproductive period and chronic morbidities were the focus of primary care. FHS implementation strengthens health promotion.
- Published
- 2018
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10. Potential energy surfaces of quintet and singlet O 4 .
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Paukku Y, Yang KR, Varga Z, Song G, Bender JD, and Truhlar DG
- Abstract
We present global ground-state potential energy surfaces for the quintet and singlet spin states of the O
4 system that are suitable for treating high-energy vibrational-rotational energy transfer and collision-induced dissociation in electronically adiabatic, spin-conserving O2 -O2 collisions. The surfaces are based on MS-CASPT2/maug-cc-pVTZ electronic structure calculations with scaled external correlation. The active space has 16 electrons in 12 orbitals. The calculations cover nine kinds of geometrical arrangements corresponding to dissociative diatom-diatom collisions of O2 , geometries corresponding to O3 -O, geometries identified by running trajectories, and geometries along linear synchronous transit paths. The global ground-state potential energy surfaces were obtained by a many-body approach with an accurate O-O pairwise interaction and a fit of the many-body interaction to 12 684 electronic structure data points for the singlet and 10 543 electronic structure data points for the quintet. The many-body fit is based on permutationally invariant polynomials in terms of bond-order functions of the six interatomic distances; the bond-order functions are mixed exponential-Gaussian functions.- Published
- 2017
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11. An improved potential energy surface and multi-temperature quasiclassical trajectory calculations of N2 + N2 dissociation reactions.
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Bender JD, Valentini P, Nompelis I, Paukku Y, Varga Z, Truhlar DG, Schwartzentruber T, and Candler GV
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Accurate modeling of high-temperature hypersonic flows in the atmosphere requires consideration of collision-induced dissociation of molecular species and energy transfer between the translational and internal modes of the gas molecules. Here, we describe a study of the N2 + N2⟶N2 + 2N and N2 + N2⟶4N nitrogen dissociation reactions using the quasiclassical trajectory (QCT) method. The simulations used a new potential energy surface for the N4 system; the surface is an improved version of one that was presented previously. In the QCT calculations, initial conditions were determined based on a two-temperature model that approximately separates the translational-rotational temperature from the vibrational temperature of the N2 diatoms. Five values from 8000 K to 30,000 K were considered for each of the two temperatures. Over 2.4 × 10(9) trajectories were calculated. We present results for ensemble-averaged dissociation rate constants as functions of the translational-rotational temperature T and the vibrational temperature T(v). The rate constant depends more strongly on T when T(v) is low, and it depends more strongly on T(v) when T is low. Quasibound reactant states contribute significantly to the rate constants, as do exchange processes at higher temperatures. We discuss two sets of runs in detail: an equilibrium test set in which T = T(v) and a nonequilibrium test set in which T(v) < T. In the equilibrium test set, high-v and moderately-low-j molecules contribute most significantly to the overall dissociation rate, and this state specificity becomes stronger as the temperature decreases. Dissociating trajectories tend to result in a major loss of vibrational energy and a minor loss of rotational energy. In the nonequilibrium test set, as T(v) decreases while T is fixed, higher-j molecules contribute more significantly to the dissociation rate, dissociating trajectories tend to result in a greater rotational energy loss, and the dissociation probability's dependence on v weakens. In this way, as T(v) decreases, rotational energy appears to compensate for the decline in average vibrational energy in promoting dissociation. In both the equilibrium and nonequilibrium test sets, in every case, the average total internal energy loss in the dissociating trajectories is between 10.2 and 11.0 eV, slightly larger than the equilibrium potential energy change of N2 dissociation.
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- 2015
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12. Potential energy surface fitting by a statistically localized, permutationally invariant, local interpolating moving least squares method for the many-body potential: method and application to N4.
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Bender JD, Doraiswamy S, Truhlar DG, and Candler GV
- Abstract
Fitting potential energy surfaces to analytic forms is an important first step for efficient molecular dynamics simulations. Here, we present an improved version of the local interpolating moving least squares method (L-IMLS) for such fitting. Our method has three key improvements. First, pairwise interactions are modeled separately from many-body interactions. Second, permutational invariance is incorporated in the basis functions, using permutationally invariant polynomials in Morse variables, and in the weight functions. Third, computational cost is reduced by statistical localization, in which we statistically correlate the cutoff radius with data point density. We motivate our discussion in this paper with a review of global and local least-squares-based fitting methods in one dimension. Then, we develop our method in six dimensions, and we note that it allows the analytic evaluation of gradients, a feature that is important for molecular dynamics. The approach, which we call statistically localized, permutationally invariant, local interpolating moving least squares fitting of the many-body potential (SL-PI-L-IMLS-MP, or, more simply, L-IMLS-G2), is used to fit a potential energy surface to an electronic structure dataset for N4. We discuss its performance on the dataset and give directions for further research, including applications to trajectory calculations.
- Published
- 2014
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13. Novel low temperature setting nanocrystalline calcium phosphate cements for bone repair: osteoblast cellular response and gene expression studies.
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Sethuraman S, Nair LS, El-Amin S, Nguyen MT, Greish YE, Bender JD, Brown PW, Allcock HR, and Laurencin CT
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- 3T3 Cells, Alkaline Phosphatase genetics, Animals, Base Sequence, Cell Adhesion, Collagen Type I genetics, DNA Primers genetics, Durapatite chemistry, Gene Expression, Materials Testing, Mice, Microscopy, Electron, Scanning, Osteocalcin genetics, Osteopontin genetics, Reverse Transcriptase Polymerase Chain Reaction, Surface Properties, Temperature, Tissue Engineering, Bone Cements chemistry, Calcium Phosphates chemistry, Nanoparticles chemistry, Osteoblasts cytology, Osteoblasts metabolism
- Abstract
Low temperature setting calcium phosphate cements (CPC) formed from reactive calcium phosphate precursors are receiving great attention in the fields of orthopaedics and tissue engineering. The purpose of this study was to evaluate the mechanical properties and osteocompatibility of a novel calcium deficient hydroxyapatite (CDSHA) with a Ca/P ratio of 1.6 developed in our laboratories and compare it to a previously developed calcium deficient hydroxyapatite (CDHA) with a Ca/P ratio of 1.5. The results demonstrated that the calcium-deficient hydroxyapatites (HA) formed from the CPCs were similar to biological HA at physiological temperature and the elastic moduli of CDHA and CDSHA were found to be 174.42 +/- 20.41 MPa (p < 0.05) and 115.86 +/- 24.8 MPa (p < 0.05), respectively. The surface morphologies of the two calcium deficient HA's formed were identical with a micro/nano porous structure as evidenced from SEM. The cellular proliferation on CDHA, and CDSHA, was comparable to the control, tissue culture polystyrene (TCPS) (p < 0.05). Alkaline phosphatase activity was significantly elevated on CDHA and CDSHA matrices at early time points when compared with the control (TCPS) (p < 0.05). Osteoblast cells gene expression on CDHA, and CDSHA showed type I collagen, alkaline phosphatase, osteocalcin, and osteopontin activity at both 7 and 14 days of culture. Thus, novel calcium-deficient HAs, CDHA, and CDSHA formed at low temperature are promising candidates for orthopaedic applications based on their ability to promote osteoblast cell adhesion and gene expression in vitro., (Copyright 2007 Wiley Periodicals, Inc.)
- Published
- 2007
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14. Formation of hydroxyapatite-polyphosphazene polymer composites at physiologic temperature.
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Greish YE, Bender JD, Lakshmi S, Brown PW, Allcock HR, and Laurencin CT
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- Calcium metabolism, Materials Testing, Molecular Structure, X-Ray Diffraction, Biocompatible Materials chemistry, Body Temperature, Hydroxyapatites chemistry, Organophosphorus Compounds chemistry, Polymers chemistry
- Abstract
Aspects of the formation of bone analog composites at 37 degrees C are described. The composites are composed of hydroxyapatite (HAp) and the calcium salt of a biocompatible polymer and are capable of forming under in vivo conditions. Composite formation involves the formation of monolithic HAp from particulate calcium phosphate precursors while Ca ions liberated to the aqueous medium in which this reaction is occurring form crosslinks with the acidic polymer. The reactants are poly[bis(carboxylatophenoxy)phosphazene] (acid-PCPP), tetracalcium phosphate [Ca4(PO4)2O, TetCP], and anhydrous dicalcium phosphate (CaHPO4, DCPA). The effects of the proportion of polymer (5, 10, or 15 wt %) on the kinetics of HAp formation were studied. Compositional evolution of the solid calcium phosphates present was followed by X-ray diffraction and infrared spectroscopy analyses. HAp formation through a dissolution-precipitation process provided a mildly alkaline medium suitable for deprotonation of the acid-PCPP and for the formation of the calcium crosslinks, as monitored by infrared spectroscopy. Concurrence of crosslinking of the polymer and HAp formation was established, indicating true composite formation can be realized at physiologic temperature., (Copyright (c) 2006 Wiley Periodicals, Inc.)
- Published
- 2006
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15. Synthesis, characterization, and osteocompatibility evaluation of novel alanine-based polyphosphazenes.
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Nair LS, Lee DA, Bender JD, Barrett EW, Greish YE, Brown PW, Allcock HR, and Laurencin CT
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- Alanine chemistry, Alkaline Phosphatase metabolism, Animals, Biocompatible Materials chemistry, Biodegradation, Environmental, Cell Adhesion, Cell Proliferation, Cells, Cultured, Materials Testing, Microscopy, Electron, Scanning, Organophosphorus Compounds chemistry, Osteoblasts cytology, Osteoblasts enzymology, Polymers chemistry, Rats, Biocompatible Materials chemical synthesis, Bone and Bones, Organophosphorus Compounds chemical synthesis, Polymers chemical synthesis, Tissue Engineering
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This study deals with the synthesis and in vitro osteocompatibility evaluation of two novel alanine-containing biodegradable ester polyphosphazenes as candidates to form self-setting composites with hydroxyapatite (HAp) precursors. The two novel biodegradable polyphosphazenes synthesized were poly[(ethyl alanato)1.0(ethyl oxybenzoate)1.0 phosphazene] (PN-EA/EOB) and poly[(ethyl alanato)1.0(propyl oxybenzoate)1.0 phosphazene] (PN-EA/POB). The polymers were characterized by multinuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC). Biodegradability and percentage water absorption of the polymers were evaluated by following the mass change in phosphate buffer (pH 7.4) at 37 degrees C. PN-EA/POB underwent faster degradation and showed higher water absorption compared to PN-EA/EOB. Both polymers became insoluble in common organic solvents following hydrolysis presumably due to crosslinking reactions accompanying the degradation process. Osteoblast cell adhesion and proliferation on PN-EA/EOB and PN-EA/POB was followed by scanning electron microscopy (SEM) and by using a biochemical assay. Both PN-EA/EOB and PN-EA/POB supported the adhesion and proliferation of primary rat osteoblast cells in vitro. Furthermore, the enzymatic activity of the osteoblast cells cultured on the polymers was confirmed by the alkaline phosphatase activity. Thus, these biodegradable amino-acid-based polyphosphazenes are promising new materials for forming self-setting bone cements., ((c) 2005 Wiley Periodicals, Inc)
- Published
- 2006
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16. Composite formation from hydroxyapatite with sodium and potassium salts of polyphosphazene.
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Greish YE, Bender JD, Lakshmi S, Brown PW, Allcock HR, and Laurencin CT
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- Biocompatible Materials analysis, Biocompatible Materials chemistry, Bone Substitutes analysis, Durapatite analysis, Hot Temperature, Hydrogen-Ion Concentration, Kinetics, Materials Testing, Organophosphorus Compounds analysis, Polymers analysis, Potassium analysis, Salts analysis, Sodium analysis, Solubility, Surface Properties, Bone Substitutes chemistry, Crystallization methods, Durapatite chemistry, Organophosphorus Compounds chemistry, Polymers chemistry, Potassium chemistry, Salts chemistry, Sodium chemistry
- Abstract
The low temperature synthesis of composites potentially suitable as bone substitutes which form in vivo, was investigated. The composites were comprised of stoichiometric hydroxyapatite (SHAp) and water-soluble poly phosphazenes. These constituents were selected because of their biocompatibility, and were mixed as powders with a phosphate buffer solution (PBS) to form the composites. The effects of poly[bis(sodium carboxylatophenoxy)phosphazene] (Na-PCPP) or poly[bis(potassium carboxylatophenoxy) phosphazene] (K-PCPP) on stoichiometric hydroxyapatite (SHAp) formation from tetracalcium phosphate and anhydrous dicalcium phosphate were assessed. The kinetics and reaction chemistries of composite formation were followed by isothermal calorimetry, X-ray diffraction, infrared spectroscopy and scanning electron microscopy. In the presence of 1% by weight of polyphosphazenes, composites comprised of SHAp and calcium cross-linked polymer salts were formed. Thus a mechanism for binding between polymer chains was established. Elevated proportions (5 and 10% by weight) of polyphosphazene, however, resulted in the inhibition of SHAp formation. This is attributed to the formation of viscous polymer solution coatings on the calcium phosphate precursors, retarding their reaction, and consequently inhibiting SHAp formation.
- Published
- 2005
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17. Low temperature formation of hydroxyapatite-poly(alkyl oxybenzoate)phosphazene composites for biomedical applications.
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Greish YE, Bender JD, Lakshmi S, Brown PW, Allcock HR, and Laurencin CT
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- Biomedical Engineering methods, Bone Substitutes chemical synthesis, Kinetics, Manufactured Materials, Molecular Conformation, Surface Properties, Temperature, Absorbable Implants, Bone Substitutes chemistry, Crystallization methods, Durapatite chemistry, Materials Testing, Organophosphorus Compounds chemistry, Polymers chemistry
- Abstract
The formation of biodegradable composites which may be suitable as bone analogs is described. Polyphosphazene-hydroxyapatite (HAp) composites were produced via an acid-base reaction of tetracalcium phosphate and anhydrous dicalcium phosphate in the presence of polyphosphazenes bearing alkyl ester containing side-groups. The polyphosphazenes used were poly(ethyl oxybenzoate)phosphazene (PN-EOB) and poly(propyl oxybenzoate) phosphazene (PN-POB). The effects of temperature and the proportions of polymers, PN-EOB and PN-POB on the kinetics, reaction chemistry and phase evolution during the formation of stoichiometric HAp were studied. Kinetics, phase evolution and microstructural development were evaluated using isothermal calorimetry, X-ray diffraction and scanning electron microscopy, respectively. Analysis of solution chemistry revealed that the increases in the pH during the formation of SHAp, resulted in partial hydrolysis of the polymer surfaces, which led in turn to the formation of a calcium cross-linked polymer surface. The calcium cross-linked polymer surface appeared to facilitate the nucleation and growth of apatite deposits on the polymer. The current study illustrates the in situ formation of HAp in the presence of polyphosphazenes, where HAp is chemically bonded to the polymer., (Copyright 2004 Elsevier Ltd.)
- Published
- 2005
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18. Fabrication and optimization of methylphenoxy substituted polyphosphazene nanofibers for biomedical applications.
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Nair LS, Bhattacharyya S, Bender JD, Greish YE, Brown PW, Allcock HR, and Laurencin CT
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- 3T3 Cells, Animals, Biocompatible Materials chemistry, Cattle, Cell Adhesion, Cell Proliferation, Chloroform, Dose-Response Relationship, Drug, Electrophysiology, Endothelium, Vascular cytology, Macromolecular Substances chemistry, Magnetic Resonance Spectroscopy, Mice, Microscopy, Electron, Scanning, Models, Chemical, Nanotechnology, Osteoblasts cytology, Solvents, Surface Properties, Temperature, Time Factors, Tissue Engineering methods, Ultraviolet Rays, Organophosphorus Compounds chemistry, Polymers chemistry
- Abstract
Electrospinning has developed as a unique and versatile process to fabricate ultrathin fibers in the form of nonwoven meshes or as oriented arrays from a variety of polymers. The very small dimension of these fibers can generate a high surface area, which makes them potential candidates for various biomedical and industrial applications. The objective of the present study was to develop nanofibers from polyphosphazenes, a class of inorganic-organic polymers known for high biocompatibility, high-temperature stability, and low-temperature flexibility. Specifically, we evaluated the feasibility of developing bead-free nonwoven nanofiber mesh from poly[bis(p-methylphenoxy)phosphazene] (PNmPh) by electrospinning. The effect of process parameters such as nature of solvent, concentration of the polymer solution, effect of needle diameter, and applied potential on the diameter and morphology (beaded or bead-free) of resulting nanofibers were investigated. It was found that solution of PNmPh in chloroform at a concentration range of 7% (wt/v) to 9% (wt/v) can be readily electrospun to form bead-free fibers at room temperature. The mean diameter of the fibers obtained under optimized spinning condition was found to be approximately 1.2 microm. The bead-free, cylindrical nanofibers formed under the optimized condition showed a slightly irregular surface topography with indentations of a few nanometer scale. Further, the electrospun nanofiber mats supported the adhesion of bovine coronary artery endothelial cells (BCAEC) as well as promoted the adhesion and proliferation of osteoblast like MC3T3-E1 cells.
- Published
- 2004
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19. Synthesis and self-association behavior of biodegradable amphiphilic poly[bis(ethyl glycinat-N-yl)phosphazene]- poly(ethylene oxide) block copolymers.
- Author
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Chang Y, Bender JD, Phelps MV, and Allcock HR
- Subjects
- Biocompatible Materials chemical synthesis, Biocompatible Materials chemistry, Biodegradation, Environmental, Micelles, Organophosphorus Compounds chemistry, Polyethylene Glycols chemistry, Polymers chemistry, Surface-Active Agents chemical synthesis, Surface-Active Agents chemistry, Polymers chemical synthesis
- Abstract
Amphiphilic diblock copolymers with varying compositions of hydrophilic poly(ethylene oxide) (PEO) and hydrophobic poly[bis(ethyl glycinat-N-yl)phosphazene] (PNgly) were synthesized via the controlled cationic-induced polymerization of a phosphoranimine (Cl(3)P=NSiMe(3)) at ambient temperature using a PEO-phosphoranimine macroinitiator. The aqueous-phase transition behavior of PEO-PNgly-3 (M(n) = 10,000) and micelle formation of both PEO-PNgly-3 and PEO-PNgly-4 (M(n) = 8,500) were investigated using fluorescence techniques and dynamic light scattering. The critical micelle concentrations (cmc's) of PEO-PNgly-3 and PEO-PNgly-4 were determined to be 3 and 12 mg/L with the mean diameters of micelles being 120 and 130 nm, respectively. The hydrolytic degradation of these diblock copolymers was also studied in solution. These studies coupled with the biodegradability of the poly[bis(ethyl glycinat-N-yl)phosphazene] block to give benign products make PEO-PNgly copolymers well-suited for a wide variety of biomedical applications including novel biodegradable drug-delivery systems.
- Published
- 2002
- Full Text
- View/download PDF
20. Thermal rearrangement of 7-methylbicyclo
- Author
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Bender JD, Leber PA, Lirio RR, and Smith RS
- Abstract
The gas-phase thermal rearrangement of exo-7-methylbicyclo[3.2.0]hept-2-ene yields almost exclusively 5-methylnorbornene products. Inversion (i) of configuration dominates this [1,3] sigmatropic shift although some retention (r) is also observed. Because the [1,3] migration can only occur suprafacially (s) in this geometrically constrained system, the si/sr ratio of 7 observed for the migration of C7 in exo-7-methylbicyclo[3.2.0]hept-2-ene indicates that the orbital symmetry rules are somewhat permissive for the [1,3] sigmatropic migration of carbon.
- Published
- 2000
- Full Text
- View/download PDF
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