| 1. |
- Bravo, L, et al.
(författare)
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- 2021
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swepub:Mat__t
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| 2. |
- Tabiri, S, et al.
(författare)
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- 2021
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swepub:Mat__t
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| 3. |
- Kanai, M, et al.
(författare)
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- 2023
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swepub:Mat__t
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| 4. |
- Niemi, MEK, et al.
(författare)
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- 2021
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swepub:Mat__t
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| 5. |
- Naghavi, Mohsen, et al.
(författare)
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Global, regional, and national age-sex specific all-cause and cause-specific mortality for 240 causes of death, 1990-2013: a systematic analysis for the Global Burden of Disease Study 2013
- 2015
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Ingår i: The Lancet. - 1474-547X .- 0140-6736. ; 385:9963, s. 117-171
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Tidskriftsartikel (refereegranskat)abstract
- Background Up-to-date evidence on levels and trends for age-sex-specifi c all-cause and cause-specifi c mortality is essential for the formation of global, regional, and national health policies. In the Global Burden of Disease Study 2013 (GBD 2013) we estimated yearly deaths for 188 countries between 1990, and 2013. We used the results to assess whether there is epidemiological convergence across countries. Methods We estimated age-sex-specifi c all-cause mortality using the GBD 2010 methods with some refinements to improve accuracy applied to an updated database of vital registration, survey, and census data. We generally estimated cause of death as in the GBD 2010. Key improvements included the addition of more recent vital registration data for 72 countries, an updated verbal autopsy literature review, two new and detailed data systems for China, and more detail for Mexico, UK, Turkey, and Russia. We improved statistical models for garbage code redistribution. We used six different modelling strategies across the 240 causes; cause of death ensemble modelling (CODEm) was the dominant strategy for causes with sufficient information. Trends for Alzheimer's disease and other dementias were informed by meta-regression of prevalence studies. For pathogen-specifi c causes of diarrhoea and lower respiratory infections we used a counterfactual approach. We computed two measures of convergence (inequality) across countries: the average relative difference across all pairs of countries (Gini coefficient) and the average absolute difference across countries. To summarise broad findings, we used multiple decrement life-tables to decompose probabilities of death from birth to exact age 15 years, from exact age 15 years to exact age 50 years, and from exact age 50 years to exact age 75 years, and life expectancy at birth into major causes. For all quantities reported, we computed 95% uncertainty intervals (UIs). We constrained cause-specific fractions within each age-sex-country-year group to sum to all-cause mortality based on draws from the uncertainty distributions. Findings Global life expectancy for both sexes increased from 65.3 years (UI 65.0-65.6) in 1990, to 71.5 years (UI 71.0-71.9) in 2013, while the number of deaths increased from 47.5 million (UI 46.8-48.2) to 54.9 million (UI 53.6-56.3) over the same interval. Global progress masked variation by age and sex: for children, average absolute diff erences between countries decreased but relative diff erences increased. For women aged 25-39 years and older than 75 years and for men aged 20-49 years and 65 years and older, both absolute and relative diff erences increased. Decomposition of global and regional life expectancy showed the prominent role of reductions in age-standardised death rates for cardiovascular diseases and cancers in high-income regions, and reductions in child deaths from diarrhoea, lower respiratory infections, and neonatal causes in low-income regions. HIV/AIDS reduced life expectancy in southern sub-Saharan Africa. For most communicable causes of death both numbers of deaths and age-standardised death rates fell whereas for most non-communicable causes, demographic shifts have increased numbers of deaths but decreased age-standardised death rates. Global deaths from injury increased by 10.7%, from 4.3 million deaths in 1990 to 4.8 million in 2013; but age-standardised rates declined over the same period by 21%. For some causes of more than 100 000 deaths per year in 2013, age-standardised death rates increased between 1990 and 2013, including HIV/AIDS, pancreatic cancer, atrial fibrillation and flutter, drug use disorders, diabetes, chronic kidney disease, and sickle-cell anaemias. Diarrhoeal diseases, lower respiratory infections, neonatal causes, and malaria are still in the top five causes of death in children younger than 5 years. The most important pathogens are rotavirus for diarrhoea and pneumococcus for lower respiratory infections. Country-specific probabilities of death over three phases of life were substantially varied between and within regions. Interpretation For most countries, the general pattern of reductions in age-sex specifi c mortality has been associated with a progressive shift towards a larger share of the remaining deaths caused by non-communicable disease and injuries. Assessing epidemiological convergence across countries depends on whether an absolute or relative measure of inequality is used. Nevertheless, age-standardised death rates for seven substantial causes are increasing, suggesting the potential for reversals in some countries. Important gaps exist in the empirical data for cause of death estimates for some countries; for example, no national data for India are available for the past decade.
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| 6. |
- Forouzanfar, Mohammad H, et al.
(författare)
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Global, regional, and national comparative risk assessment of 79 behavioural, environmental and occupational, and metabolic risks or clusters of risks in 188 countries, 1990-2013 : a systematic analysis for the Global Burden of Disease Study 2013.
- 2015
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Ingår i: The Lancet. - 0140-6736 .- 1474-547X. ; 386:10010, s. 2287-2323
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The Global Burden of Disease, Injuries, and Risk Factor study 2013 (GBD 2013) is the first of a series of annual updates of the GBD. Risk factor quantification, particularly of modifiable risk factors, can help to identify emerging threats to population health and opportunities for prevention. The GBD 2013 provides a timely opportunity to update the comparative risk assessment with new data for exposure, relative risks, and evidence on the appropriate counterfactual risk distribution.METHODS: Attributable deaths, years of life lost, years lived with disability, and disability-adjusted life-years (DALYs) have been estimated for 79 risks or clusters of risks using the GBD 2010 methods. Risk-outcome pairs meeting explicit evidence criteria were assessed for 188 countries for the period 1990-2013 by age and sex using three inputs: risk exposure, relative risks, and the theoretical minimum risk exposure level (TMREL). Risks are organised into a hierarchy with blocks of behavioural, environmental and occupational, and metabolic risks at the first level of the hierarchy. The next level in the hierarchy includes nine clusters of related risks and two individual risks, with more detail provided at levels 3 and 4 of the hierarchy. Compared with GBD 2010, six new risk factors have been added: handwashing practices, occupational exposure to trichloroethylene, childhood wasting, childhood stunting, unsafe sex, and low glomerular filtration rate. For most risks, data for exposure were synthesised with a Bayesian meta-regression method, DisMod-MR 2.0, or spatial-temporal Gaussian process regression. Relative risks were based on meta-regressions of published cohort and intervention studies. Attributable burden for clusters of risks and all risks combined took into account evidence on the mediation of some risks such as high body-mass index (BMI) through other risks such as high systolic blood pressure and high cholesterol.FINDINGS: All risks combined account for 57·2% (95% uncertainty interval [UI] 55·8-58·5) of deaths and 41·6% (40·1-43·0) of DALYs. Risks quantified account for 87·9% (86·5-89·3) of cardiovascular disease DALYs, ranging to a low of 0% for neonatal disorders and neglected tropical diseases and malaria. In terms of global DALYs in 2013, six risks or clusters of risks each caused more than 5% of DALYs: dietary risks accounting for 11·3 million deaths and 241·4 million DALYs, high systolic blood pressure for 10·4 million deaths and 208·1 million DALYs, child and maternal malnutrition for 1·7 million deaths and 176·9 million DALYs, tobacco smoke for 6·1 million deaths and 143·5 million DALYs, air pollution for 5·5 million deaths and 141·5 million DALYs, and high BMI for 4·4 million deaths and 134·0 million DALYs. Risk factor patterns vary across regions and countries and with time. In sub-Saharan Africa, the leading risk factors are child and maternal malnutrition, unsafe sex, and unsafe water, sanitation, and handwashing. In women, in nearly all countries in the Americas, north Africa, and the Middle East, and in many other high-income countries, high BMI is the leading risk factor, with high systolic blood pressure as the leading risk in most of Central and Eastern Europe and south and east Asia. For men, high systolic blood pressure or tobacco use are the leading risks in nearly all high-income countries, in north Africa and the Middle East, Europe, and Asia. For men and women, unsafe sex is the leading risk in a corridor from Kenya to South Africa.INTERPRETATION: Behavioural, environmental and occupational, and metabolic risks can explain half of global mortality and more than one-third of global DALYs providing many opportunities for prevention. Of the larger risks, the attributable burden of high BMI has increased in the past 23 years. In view of the prominence of behavioural risk factors, behavioural and social science research on interventions for these risks should be strengthened. Many prevention and primary care policy options are available now to act on key risks.FUNDING: Bill & Melinda Gates Foundation.
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| 7. |
- Vos, Theo, et al.
(författare)
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Global, regional, and national incidence, prevalence, and years lived with disability for 301 acute and chronic diseases and injuries in 188 countries, 1990-2013: a systematic analysis for the Global Burden of Disease Study 2013
- 2015
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Ingår i: The Lancet. - 1474-547X .- 0140-6736. ; 386:9995, s. 743-800
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Tidskriftsartikel (refereegranskat)abstract
- Background Up-to-date evidence about levels and trends in disease and injury incidence, prevalence, and years lived with disability (YLDs) is an essential input into global, regional, and national health policies. In the Global Burden of Disease Study 2013 (GBD 2013), we estimated these quantities for acute and chronic diseases and injuries for 188 countries between 1990 and 2013. Methods Estimates were calculated for disease and injury incidence, prevalence, and YLDs using GBD 2010 methods with some important refinements. Results for incidence of acute disorders and prevalence of chronic disorders are new additions to the analysis. Key improvements include expansion to the cause and sequelae list, updated systematic reviews, use of detailed injury codes, improvements to the Bayesian meta-regression method (DisMod-MR), and use of severity splits for various causes. An index of data representativeness, showing data availability, was calculated for each cause and impairment during three periods globally and at the country level for 2013. In total, 35 620 distinct sources of data were used and documented to calculated estimates for 301 diseases and injuries and 2337 sequelae. The comorbidity simulation provides estimates for the number of sequelae, concurrently, by individuals by country, year, age, and sex. Disability weights were updated with the addition of new population-based survey data from four countries. Findings Disease and injury were highly prevalent; only a small fraction of individuals had no sequelae. Comorbidity rose substantially with age and in absolute terms from 1990 to 2013. Incidence of acute sequelae were predominantly infectious diseases and short-term injuries, with over 2 billion cases of upper respiratory infections and diarrhoeal disease episodes in 2013, with the notable exception of tooth pain due to permanent caries with more than 200 million incident cases in 2013. Conversely, leading chronic sequelae were largely attributable to non-communicable diseases, with prevalence estimates for asymptomatic permanent caries and tension-type headache of 2.4 billion and 1.6 billion, respectively. The distribution of the number of sequelae in populations varied widely across regions, with an expected relation between age and disease prevalence. YLDs for both sexes increased from 537.6 million in 1990 to 764.8 million in 2013 due to population growth and ageing, whereas the age-standardised rate decreased little from 114.87 per 1000 people to 110.31 per 1000 people between 1990 and 2013. Leading causes of YLDs included low back pain and major depressive disorder among the top ten causes of YLDs in every country. YLD rates per person, by major cause groups, indicated the main drivers of increases were due to musculoskeletal, mental, and substance use disorders, neurological disorders, and chronic respiratory diseases; however HIV/AIDS was a notable driver of increasing YLDs in sub-Saharan Africa. Also, the proportion of disability-adjusted life years due to YLDs increased globally from 21.1% in 1990 to 31.2% in 2013. Interpretation Ageing of the world's population is leading to a substantial increase in the numbers of individuals with sequelae of diseases and injuries. Rates of YLDs are declining much more slowly than mortality rates. The non-fatal dimensions of disease and injury will require more and more attention from health systems. The transition to non-fatal outcomes as the dominant source of burden of disease is occurring rapidly outside of sub-Saharan Africa. Our results can guide future health initiatives through examination of epidemiological trends and a better understanding of variation across countries.
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| 8. |
- Atluri, Rambabu, 1981-, et al.
(författare)
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Co-Structure Directing Agent Induced Phase Transformation of Mesoporous Materials
- 2009
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 25:5, s. 3189-3195
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis of cubic Pm (3) over barn mesocaged solid templated by cetyltrimethyl ammonium bromide (C(16)TMABr) surfactant by direct cocondensation of (3-aminopropyl)triethoxysilanes (APES) under strong alkaline conditions is reported. The novel route gives direct incorporation of amino functional groups on the porous silica wall, and the structural formation has been followed by means of in situ SAXS studies performed at a synchrotron beam line. Data shows that a molar ratio of C(16)TMABr/APES = 0.6 favors the formation of 3D cubic mesocaged solid with Pm3n symmetry which transforms to a cylindrical mesoporous phase with p6mm symmetry at higher molar ratios. Further structural evaluation has been performed by means electron crystallography (EC). Reconstructed 3D models based on EC show the presence of spherical cages (A-cages, 45 angstrom) and ellipsoidal cages (B-cages, 48 x 43 angstrom) whereby every cage in the unit cell is connected to 14 nearest cages with a window size of 18 angstrom. Finally, a mechanism is proposed, denoted S+similar to N degrees I-, in which penetration of the neutral aminopropyl moiety within the micellar corona is responsible for the formation of the Pm (3) over barn phase, accounting for the formation of the hexagonal phase at higher molar ratios and higher temperatures. In comparison to other mesocaged materials with the same symmetry this structure possesses a more open porous network which will help assess its potential in a variety of applications discussed herein.
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| 9. |
- Atluri, Rambabu, et al.
(författare)
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Non-Surfactant Supramolecular Templating Synthesis of Ordered Mesoporous Silica
- 2009
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 131:9, s. 3189-3191
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Tidskriftsartikel (refereegranskat)abstract
- Hoogsteen-bonded tetrads and pentamers are formed by a large variety of organic molecules through H-donor and acceptor groups capable of inducing self-organization to form columnar and hexagonal mesophases. The biological importance of such macromolecular structures is exemplified by the assembly of guanosine-rich groups of telomere units and their implication in chromosomal replication. Folic acid is composed of a pterin group, chemically and structurally similar to guanine, conjugated to an l-glutamate moiety via a p-amino benzoic acid. Our aim has been to develop a delivery vehicle for folic acid and at the same time provide a novel synthetic route for ordered mesoporous materials without the use of amphiphilic surfactants. We present a new nonsurfactant route for the synthesis of highly ordered mesoporous materials, based on the supramolecular templating of stacked arrays of the tetramer-forming pterin groups of folic acid under a variety of synthetic conditions. This method leads to hexagonally ordered mesoporous structures with gyroid, spherical, and chiral morphologies with pores on the order of 25−30 Å in diameter and surface areas above 1000 m2/g. More importantly circular dichroism studies reveal that the folate template possesses a chiral signature within the pores in the as-synthesized solid and that chirality is transferred from the folate template to the pore surface via the aminopropyl triethoxysilane costructure directing agent used in the supramolecular assembly. This novel templating approach for ordered mesoporous materials breaks the hegemony of surfactant micellar systems for the preparation of these exciting high surface area solids and opens new opportunities for structural control, design of pore geometry, and novel applications.
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| 10. |
- Atluri, Rambabu, 1981-
(författare)
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Novel Syntheses, Structures and Functions of Mesoporous Silica Materials
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The field of mesoporous silica has been studied for about 20 years but it is still an area attracting a lot of attention. The use of novel templating molecules and several issues related to the synthesis and fine structural details are still poorly understood. These aspects are of special relevance to the theme of this thesis, which includes novel work on three fronts; the synthesis, characterization and applications of mesoporous materials. The work described in this thesis aims to contribute to the mesoporous field by developing novel methods of mesoporous silica synthesis without relying on surfactant micelles as the templating agent but focusing instead on the stacking arrangement of aromatic molecules such as folic acid. The novel route presented here leads to 2D hexagonal structures with p6mm symmetry possessing high mesoporosity and large surface areas. The versatility of this route at various synthesis temperatures and using hydrothermal treatments has also been investigated. A novel strategy is also proposed for the synthesis of mesocaged materials with Pm3n symmetry structures. The mechanism relies on the penetration of the neutral propylamino moiety of a co-structure directing agent into the hydrophobic core of the surfactant micelles. Beside these novel pathways, the effect of hydrothermal treatment (HT) at 100 oC on the 3D cubic Ia3d structure (AMS-6) over a long period of time was also examined, and the results show a phase transformation from a 3D cubic Ia3d to a 2D hexagonal p6mm structure and a return to the 3D cubic Ia3d structure at a later stage in the synthesis. This unexpected result is discussed. In this work, the detailed structural characterization of mesoporous materials using electron microscopy techniques is an important task. In particular, to extend previous knowledge, the fine structural details of mesocaged materials possessing Pm3n symmetry prepared with various amphiphilic surfactants under acidic and alkaline conditions has been investigated using electron crystallography and sorption studies. The results show subtle fine structural differences with materials prepared under alkaline conditions exhibiting the largest mesocage sizes. The cage and window sizes are primarily determined by the charge density of the surfactant and the thickness of the hydration layer surrounding the surfactant micelles. The relationship between the mesoporous structure and its function has been investigated by evaluating the rate of release of amphiphilic molecules, used as model molecules, from the internal pore structures of mesoporous materials with different pore geometries. In a similar study, the rate of proton diffusion from a liquid surrounding the mesoporous nanoparticles into the pore system of AMS-n was also assessed. The results show that the diffusion coefficients for the proton absorption process are higher than those for the release of the surfactant template molecules, with more complex 3D mesocaged particles showing the highest diffusion coefficients in both cases. Finally, the quantity of CO2 adsorption was measured by modifying the internal surfaces of mesocaged material with n-propylamino groups. Results show that the cage-connecting window sizes limit the surface coverage of n-propylamino groups by pore blocking and affect the volume of CO2 adsorption. In addition, at the molecular level, CO2 adsorption shows physisorption or chemisorption depending on the localized distribution of n-propylamino groups, as studied by in-situ infrared spectroscopy.
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| 11. |
- Atluri, Rambabu, et al.
(författare)
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Self-Assembly Mechanism of Folate-Templated Mesoporous Silica
- 2013
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 29:38, s. 12003-12012
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Tidskriftsartikel (refereegranskat)abstract
- A method to form ordered mesoporous silica based on the use of folate supramolecular templates has been developed. Evidence based on in situ small-angle X-ray scattering (SAXS), electron microscopy, infrared spectroscopy, and in situ conductivity measurements are used to investigate the organic inorganic interactions and synthesis mechanism. The behavior of folate molecules in solution differs distinctively from that of surfactants commonly used for the preparation of ordered mesoporous silica phases, notably with the absence of a critical micellar concentration. In situ SAXS studies reveal fluctuations in X-ray scattering intensities consistent with the condensation of the silica precursor surrounding the folate template and the growth of the silica mesostructure in the initial stages. High-angle X-ray diffraction shows that the folate template is well-ordered within the pores even after a few minutes of synthesis. Direct structural data for the self-assembly of folates into chiral tetramers within the pores of mesoporous silica provide evidence for the in register stacking of folate tetramers, resulting in a chiral surface of rotated tetramers, with a rotation angle of 30 degrees. Additionally, the self-assembled folates within pores were capable of adsorbing a considerable amount of CO2 gas through the cavity space of the tetramers. The study demonstrates the validity of using a naturally occurring template to produce relevant and functional mesoporous materials.
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| 12. |
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| 13. |
- Atluri, Rambabu, et al.
(författare)
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Structural variations in mesoporous materials with cubic Pm(3)over-barn symmetry
- 2010
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Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 133:1-3, s. 27-35
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Tidskriftsartikel (refereegranskat)abstract
- The fine structural details of mesoporous materials possessing Pmn symmetry prepared with varying amphiphilic surfactants under acid and alkaline conditions are investigated using electron crystallography and sorption studies. The structural data derived is used to understand the parameters that govern the formation of cavity–windows and to propose synthetic strategies in order to control independently the size of the cavities and cavity–windows. Results support that whilst attainment of Pmn cubic packing is due to the overall surfactant geometry, the formation of cavity–windows is associated with the hydration layer formed at the interphase between the surfactant and the silica wall. The charge density at the micelle surface may be tailored using two strategies: (i) using dicationic gemini surfactants at low pHs resulting in an increase in the hydration layer; or (ii) by using co-structure directing agents such as organoalkoxysilanes which reduce the hydration layer surrounding the micelles. The latter leads to the formation of higher cavity sizes and may be useful for tuning fine structural details of mesoporous materials when considering their use in important applications such as gas separation.
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| 14. |
- Atluri, Rambabu, 1981-, et al.
(författare)
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Structural variations in mesoporous materials with cubic Pm3n symmetry
- 2010
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Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 133:1-3, s. 27-35
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Tidskriftsartikel (refereegranskat)abstract
- The fine structural details of mesoporous materials possessing Pm3n symmetry prepared with varying amphiphilic surfactants under acid and alkaline conditions are investigated using electron crystallography and sorption studies. The structural data derived is used to understand the parameters that govern the formation of cavity-windows and to propose synthetic strategies in order to control independently the size of the cavities and cavity-windows. Results support that whilst attainment of Pm3n cubic packing is due to the overall surfactant geometry, the formation of cavity-windows is associated with the hydration layer formed at the interphase between the surfactant and the silica wall. The charge density at the micelle surface may be tailored using two strategies: (i) using dicationic gemini surfactants at low pHs resulting in an increase in the hydration layer; or (ii) by using co-structure directing agents such as organoalkoxysilanes which reduce the hydration layer surrounding the micelles. The latter leads to the formation of higher cavity sizes and may be useful for tuning fine structural details of mesoporous materials when considering their use in important applications such as gas separation.
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| 15. |
- Bacsik, Zoltan, et al.
(författare)
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Mechanisms and Kinetics for Sorption of CO(2) on Bicontinuous Mesoporous Silica Modified with n-Propylamine
- 2011
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 27:17, s. 11118-11128
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Tidskriftsartikel (refereegranskat)abstract
- We studied equilibrium adsorption and uptake kinetics and identified molecular species that formed during sorption of carbon dioxide on amine-modified silica. Bicontinuous silicas (AMS-6 and MCM-48) were postsynthetically modified with (3-aminopropyl)triethoxysilane or (3-aminopropyl)methyldiethoxysilane, and amine-modified AMS-6 adsorbed more CO(2) than did amine-modified MCM-48. By in situ FTIR spectroscopy, we showed that the amine groups reacted with CO(2) and formed ammonium carbamate ion pairs as well as carbamic acids under both dry and moist conditions. The carbamic acid was stabilized by hydrogen bonds, and ammonium carbamate ion pairs formed preferably on sorbents with high densities of amine groups. Under dry conditions, silylpropylcarbamate formed, slowly, by condensing carbamic acid and silanol groups. The ratio of ammonium carbamate ion pairs to silylpropylcarbamate was higher for samples with high amine contents than samples with low amine contents. Bicarbonates or carbonates did not form under dry or moist conditions. The uptake of CO(2) was enhanced in the presence of water, which was rationalized by the observed release of additional amine groups under these conditions and related formation of ammonium carbamate ion pairs. Distinct evidence for a fourth and irreversibly formed moiety was observed under sorption of CO(2) under dry conditions. Significant amounts of physisorbed, linear CO(2) were detected at relatively high partial pressures of CO(2), such that they could adsorb only after the reactive amine groups were consumed.
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| 16. |
- Bacsik, Zoltan, et al.
(författare)
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Temperature-Induced Uptake of CO2 and Formation of Carbamates in Mesocaged Silica Modified with n-Propylamines
- 2010
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 26:12, s. 10013-10024
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Tidskriftsartikel (refereegranskat)abstract
- Adsorption-mediated CO2 separation can reduce the costs of carbon capture and storage. The reduction in cost requires adsorbents with high capacities for CO2 sorption and high CO2-over-N2 selectivity. Amine-modified sorbents are promising candidates for carbon capture. To investigate the details of CO2 adsorption in such materials, we studied mesocaged (cubic, Pm3n symmetry) silica adsorbents with tethered propylamines using Fourier transform infrared (FTIR) spectroscopy and volumetric uptake experiments. The degree of heterogeneity in these coatings was varied by either co-synthesizing or post-synthetically introducing the propylamine modification. In situ FTIR spectroscopy revealed the presence of both physisorbed and chemisorbed CO2 in the materials. We present the first direct molecular evidence for physisorption using FTIR spectroscopy in mesoporous silica sorbents modified with propylamines. Physisorption reduced the CO2-over-N2 selectivity in amine-rich sorbents. Samples with homogenous coatings showed typical CO2 adsorption trends and large quantities of IR-observable physisorbed CO2. The uptake of CO2 in mesocaged materials with heterogeneous propylamine coatings was higher at high temperatures than at low temperatures. At higher temperatures and low pressures, the post-synthetically modified materials adsorbed more CO2 than did the extracted ones, even though the surface area after modification was clearly reduced and the coverage of primary amine groups was lower. The principal mode of CO2 uptake in post-synthetically modified mesoporous silica was chemisorption. The chemisorbed moieties were present mainly as carbamate–ammonium ion pairs, resulting from the quantitative transformation of primary amine groups during CO2 adsorption as established by NIR spectroscopy. The heterogeneity in the coatings promoted the formation of these ion pairs. The average propylamine–propylamine distance must be small to allow the formation of carbamate–propylammonium ion pairs.
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| 17. |
- Bueno-Alejo, Carlos J., et al.
(författare)
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Supramolecular Transcription of Guanosine Monophosphate into Mesostructured Silica
- 2014
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 53:45, s. 12106-12110
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Tidskriftsartikel (refereegranskat)abstract
- There is large interest in replicating biological supramolecular structures in inorganic materials that are capable of mimicking biological properties. The use of 5-guanosine monophosphate in the presence of Na+ and K+ ions as a supramolecular template for the synthesis of well-ordered mesostructured materials is reported here. Mesostructured particles with the confined template exhibit high structural order at both meso-and atomic scales, with a lower structural symmetry in the columnar mesophase. Although a chiral space group can not be deduced from X-ray diffraction, analysis by electron microscopy and circular dichroism confirms a chiral stacking arrangement along the c-axis. Guanosine monophosphate based mesophases thus illustrate the possibility for specific molecular imprinting of mesoporous materials by genetic material and the potential for higher definition in molecular recognition.
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| 18. |
- Fadeel, Bengt, et al.
(författare)
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Better safe than sorry : understanding the toxicological properties of inorganic nanoparticles manufactured for biomedical applications
- 2010
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Ingår i: Advanced Drug Delivery Reviews. - : Elsevier BV. - 0169-409X .- 1872-8294. ; 62:3, s. 362-374
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Forskningsöversikt (refereegranskat)abstract
- The development of nanoparticles for biomedical applications including medical imaging and drug delivery is currently undergoing a dramatic expansion. However, as the range of nanoparticle types and applications increases, it is also clear that the potential toxicities of these novel materials and the properties driving such toxic responses must also be understood. Indeed, a detailed assessment of the factors that influence the biocompatibility and/or toxicity of nanoparticles is crucial for the safe and sustainable development of the emerging nanotechnologies. This review summarizes some of the recent developments in the field of nanomedicine with particular emphasis on inorganic nanoparticles for drug delivery. The synthesis routes, physico-chemical characteristics, and cytotoxic properties of inorganic nanoparticles are thus explored and lessons learned from the toxicological investigation of three common types of engineered nanomaterials of titania, gold, and mesoporous silica are discussed. Emphasis is placed on the recognition versus non-recognition of engineered nanomaterials by the immune system, the primary surveillance system against microorganisms and particles, which, in turn, is intimately linked to the issue of targeted drug delivery using such nanomaterials as carrier systems.
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| 19. |
- Garcia-Bennett, Alfonso E., et al.
(författare)
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A mechanistic study of the formation of mesoporous structures from in situ AC conductivity measurements
- 2007
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Ingår i: Langmuir. - 0743-7463 .- 1520-5827. ; 23:19, s. 9875-9881
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this work is to study the kinetics of self-assembly in the formation mechanism of anionic templated mesoporous solids (AMS-n) during die first few seconds of the synthesis as well as to demonstrate the use of alternating ion current (AIC) conductivity measurements to follow the self-assembly in complex hybrid systems. The formation of different AMS-n caged-type mesostructures through the delayed addition of the silica source is demonstrated and explained in terms of the interaction between the co-structure-directing agent (CSDA) and the oppositely charged surfactant headgroup regions. Our findings, supported by transmission electron microscopy, 29Si magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy, dynamic light scattering (DLS) measurements, and powder X-ray diffraction suggest that the interaction of the CSDA with the surfactant headgroup occurs within seconds after its addition to the synthesis gel leading to interaction between the polymerizing CSDAs and the oppositely charged micelle and to an increase in the micelle-CSDA aggregate size. Both DLS and AIC measurements agree that this process occurs within the first 1000 s after addition of the CSDA to the synthesis gel at room temperature. In addition to the mechanistic study it was found that the intermediate materials are comprised of a three-layer entity. Time-dependent 29Si MAS NMR studies reveal that an organo-silica layer forms around the micelles prior to a condensed outer inorganic shell of silica.
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| 20. |
- Garcia-Bennett, Alfonso E, et al.
(författare)
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Bicontinuous Cubic Mesoporous Materials with Biphasic Structures
- 2011
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 17:48, s. 13510-13516
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Tidskriftsartikel (refereegranskat)abstract
- The replication of amphiphilic systems within an inorganic silica matrix allows the study of the fundamental properties of mesostructural changes, that is, kinetic and structural parameters. Herein we report a detailed study of the transition between cubic bicontinuous mesostructure with space groups Ia$\bar 3$d and Pn$\bar 3$m symmetry, which are associated with the minimal G and D surfaces, respectively. The transition may be induced through micellar swelling of the anionic amphiphilic surfactant N-lauroyl alanine by trimethylbenzene. Rich kinetic behaviour is observed and has been exploited to prepare particles with biphasic structures. Transmission electron microscopy evidence indicates that there is epitaxial growth from one mesostructure to the other involving the [111] and [110] orientations of the Ia$\bar 3$d and Pn$\bar 3$m symmetry structures, respectively. From kinetic studies, we show that the formation of the Ia$\bar 3$d mesophase is preceded by a hexagonal phase (plane group p6mm) and an epitaxial relationship has been observed involving the sixfold or $\bar 3$ axis orientations of both structures. Our data suggests that the Pn$\bar 3$m mesostructure is kinetically stable at low temperatures whereas the Ia$\bar 3$d mesostructure is the more stable structure after prolonged periods of hydrothermal treatment. We present evidence from transmission electron microscopy and small-angle X-ray diffractograms and also electron crystallography modelling of the unit cells at particular points in the structural change.
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| 21. |
- Garcia-Bennett, Alfonso E., et al.
(författare)
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Delivery of Differentiation Factors by Mesoporous Silica Particles Assists Advanced Differentiation of Transplanted Murine Embryonic Stem Cells
- 2013
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Ingår i: Stem Cells Translational Medicine. - : Oxford University Press (OUP). - 2157-6564 .- 2157-6580. ; 2:11, s. 906-915
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Tidskriftsartikel (refereegranskat)abstract
- Stem cell transplantation holds great hope for the replacement of damaged cells in the nervous system. However, poor long-term survival after transplantation and insufficiently robust differentiation of stem cells into specialized cell types in vivo remain major obstacles for clinical application. Here, we report the development of a novel technological approach for the local delivery of exogenous trophic factor mimetics to transplanted cells using specifically designed silica nanoporous particles. We demonstrated that delivering Cintrofin and Gliafin, established peptide mimetics of the ciliary neurotrophic factor and glial cell line-derived neurotrophic factor, respectively, with these particles enabled not only robust functional differentiation of motor neurons from transplanted embryonic stem cells but also their long-term survival in vivo. We propose that the delivery of growth factors by mesoporous nanoparticles is a potentially versatile and widely applicable strategy for efficient differentiation and functional integration of stem cell derivatives upon transplantation.
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| 22. |
- Garcia-Bennett, Alfonso E., et al.
(författare)
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In vitro generation of motor neuron precursors from mouse embryonic stem cells using mesoporous nanoparticles
- 2014
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Ingår i: Nanomedicine. - 1743-5889 .- 1748-6963. ; 9:16, s. 2457-2466
-
Tidskriftsartikel (refereegranskat)abstract
- Aim: Stem cell-derived motor neurons (MNs) are utilized to develop replacement strategies for spinal cord disorders. Differentiation of embryonic stem cells into MN precursors involves factors and their repeated administration. We investigated if delivery of factors loaded into mesoporous nanoparticles could be effective for stem cell differentiation in vitro. Materials & methods: We used a mouse embryonic stem cell line expressing green fluorescent protein under the promoter for the MN-specific gene Hb9 to visualize the level of MN differentiation. The differentiation of stem cells was evaluated by expression of MN-specific transcription factors monitored by quantitative real-time PCR reactions and immunocytochemistry. Results: Mesoporous nanoparticles have strong affiliation to the embryoid bodies, penetrate inside the embryoid bodies and come in contact with differentiating cells. Conclusion: Repeated administration of soluble factors into a culture medium can be avoided due to a sustained release effect using mesoporous silica.
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| 23. |
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| 24. |
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| 25. |
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| 26. |
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| 27. |
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| 28. |
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| 29. |
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| 30. |
- Garcia-Bennett, Alfonso E.
(författare)
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Synthesis, toxicology and potential of ordered mesoporous materials in nanomedicine
- 2011
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Ingår i: Nanomedicine. - 1743-5889 .- 1748-6963. ; 6:5, s. 867-877
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Forskningsöversikt (refereegranskat)abstract
- Although ordered mesoporous silica materials have been studied for almost 20 years, their utilization within life science applications is relatively new and unexplored. An increasing number of researchers are transcending their respective fields in order to bridge the knowledge gap between materials chemistry and biotechnology, and to exploit the potential of mesoporous materials. Their intricate porosity with order in the nanoscale translates into high surface areas above 1000 m(2)/g, high selectivity for the encapsulation of biorelevant molecules as well as controlled surface chemistry. Their uses in pharmaceutics to improve drug formulation, drug bioavailability, mitigate drug toxicity and in cellular targeting, through controlled drug delivery strategies, have been shown. The incorporation of a high concentration of fluorescent and nuclear markers within their pores, whilst retaining good diffusion through their porous matrix, has shown them to be ideal candidates for sensing devices, in immunoassays such as flow cytometry and for their use in novel theranostic applications. This article aims to bring to the forefront some of the most important properties of mesoporous materials, which prove advantageous for their use in nanomedical applications and to highlight some of the potential areas into which the field may now emerge.
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| 31. |
- Kjellman, Tomas, et al.
(författare)
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Influence of microporosity in SBA-15 on the release properties of anticancer drug dasatinib
- 2014
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Ingår i: Journal of materials chemistry. B. - : Royal Society of Chemistry (RSC). - 2050-750X .- 2050-7518. ; 2:32, s. 5265-5271
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Tidskriftsartikel (refereegranskat)abstract
- The release of the hydrophobic cancer drug dasatinib from two mesoporous silica materials as drug delivery vehicles has been studied. One material is a reference 2D-hexagonal SBA-15 with the typical bimodal pore system with ordered primary mesopores and disordered intrawatI pores. The other material is a modified version of the same material where the intrawall porosity in the micropore regime has been selectively removed. Material characterization shows that, with the exception of the difference in intrawall porosity, the materials have identical properties. The drug dasatinib, a tyrosine kinase inhibitor, has been loaded, to the same extent, into the pores of both materials. The two materials give rise to very different release profiles of the drug. The presence of micropores leads to desired release properties: a high initial release of the drug, which is maintained over time. The lack of micropores also leads to a high initial release but followed by a rapid drop in the concentration of released drug, a consequence of its low solubility and hence crystallisation. We suggest that the presence of micropores in the carrier material, and the resultant kinetic release profile, leads to a stabilization of dasatinib in solution and to a sustained supersaturated level of the released drug. Our findings suggest that by controlling the mesoporous host with small variation in the textural properties, the kinetic release and crystallization behaviour of a drug can be altered. It is thus potentially possible to influence the drug post-release and thereby its bioavailability.
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| 32. |
- Kupferschmidt, Natalia, et al.
(författare)
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In vivo oral toxicological evaluation of mesoporous silica particles
- 2013
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Ingår i: Nanomedicine. - 1743-5889 .- 1748-6963. ; 8:1, s. 57-64
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Tidskriftsartikel (refereegranskat)abstract
- Background: Mesoporous silica particles are highly promising nanomaterials for biomedical applications. They can be used to improve bioavailability, solubility and drug stability and to protect drugs from the acidic conditions of the stomach, leading to increased drug effectiveness. Their biocompatibility in vivo has recieved little attention, in particular regarding oral administration. Aim: To study the oral tolerance of micron-sized nanoporous folic acid-templated material-1 (cylindrical, 2D hexagonal pore structure) and nanometer-sized anionic-surfactant-templated mesoporous silica material-6 (cylindrical, 3D cubic pore structure) mesoporous silica particles in Sprague Dawley rats. Materials & methods: A dose stepwise procedure or range finding test was followed by a consequent confirmatory test. The confirmatory test included daily administrations of 2000 and 1200 mg/kg doses for nanoporous folic acid-templated material-1 and anionic-surfactant-templated mesoporous silica material-6, respectively. Results: The maximum tolerated dose for anionic-surfactant-templated mesoporous silica material-6 was not reached. Similar results were observed for nanometer-sized anionic-surfactant-templated mesoporous silica material-1 in most of the animals, although adverse effects were observed in some animals that are most probably due to the administration by oral gavage of the formulated particles. Conclusion: The results are promising for the use of mesoporous silica materials as drug-delivery systems in oral administration.
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| 33. |
- Kupferschmidt, Natalia, et al.
(författare)
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In vivo oral toxicological evaluation of mesoporous silica particles
- 2013
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Ingår i: Nanomedicine. - : Future Medicine Ltd. - 1743-5889 .- 1748-6963. ; 8:1, s. 57-64
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Tidskriftsartikel (refereegranskat)abstract
- Background: Mesoporous silica particles are highly promising nanomaterials for biomedical applications. They can be used to improve bioavailability, solubility and drug stability and to protect drugs from the acidic conditions of the stomach, leading to increased drug effectiveness. Their biocompatibility in vivo has recieved little attention, in particular regarding oral administration. Aim: To study the oral tolerance of micron-sized nanoporous folic acid-templated material-1 (cylindrical, 2D hexagonal pore structure) and nanometer-sized anionic-surfactant-templated mesoporous silica material-6 (cylindrical, 3D cubic pore structure) mesoporous silica particles in Sprague Dawley rats. Materials & methods: A dose stepwise procedure or range finding test was followed by a consequent confirmatory test. The confirmatory test included daily administrations of 2000 and 1200 mg/kg doses for nanoporous folic acid-templated material-1 and anionic-surfactant-templated mesoporous silica material-6, respectively. Results: The maximum tolerated dose for anionic-surfactant-templated mesoporous silica material-6 was not reached. Similar results were observed for nanometer-sized anionic-surfactant-templated mesoporous silica material-1 in most of the animals, although adverse effects were observed in some animals that are most probably due to the administration by oral gavage of the formulated particles. Conclusion: The results are promising for the use of mesoporous silica materials as drug-delivery systems in oral administration.
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| 34. |
- Kupferschmidt, Natalia, et al.
(författare)
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Large pore mesoporous silica induced weight loss in obese mice
- 2014
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Ingår i: Nanomedicine. - 1743-5889 .- 1748-6963. ; 9:9, s. 1353-1362
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Tidskriftsartikel (refereegranskat)abstract
- Background: There is a need for medical treatments to curb the rising rate of obesity. Weight reduction is correlated with a decrease in associated risk factors and cholesterol levels in humans. Amorphous silica particles have been found to exert a hypocholesterolemic effect in humans, making them popular dietary additives. Aim: To investigate the effect of mesoporous silica, which possess sharp pore size distributions, on: weight loss, cholesterol, triglycerides and glucose blood levels in obese mice. Materials & methods: Mesoporous silicas with differing pore size were mixed in the high-fat diet of obese mice. Results: Animals receiving large pore mesoporous silica with a high-fat diet show a significant reduction in body weight and fat composition, with no observable negative effects. Conclusion: Pore size is an important parameter for reduction of body weight and body fat composition by mesoporous silica, demonstrating promising signs for the treatment of obesity.
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| 35. |
- Kupferschmidt, Natalia, et al.
(författare)
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Large pore mesoporous silica induced weight loss in obese mice
- 2013
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Ingår i: Nanomedicine. - : Future Medicine Ltd. - 1743-5889 .- 1748-6963. ; 9:9, s. 1353-1362
-
Tidskriftsartikel (refereegranskat)abstract
- Background: There is a need for medical treatments to curb the rising rate of obesity. Weight reduction is correlated with a decrease in associated risk factors and cholesterol levels in humans. Amorphous silica particles have been found to exert a hypocholesterolemic effect in humans, making them popular dietary additives. Aim: To investigate the effect of mesoporous silica, which possess sharp pore size distributions, on: weight loss, cholesterol, triglycerides and glucose blood levels in obese mice. Materials & methods: Mesoporous silicas with differing pore size were mixed in the high-fat diet of obese mice. Results: Animals receiving large pore mesoporous silica with a high-fat diet show a significant reduction in body weight and fat composition, with no observable negative effects. Conclusion: Pore size is an important parameter for reduction of body weight and body fat composition by mesoporous silica, demonstrating promising signs for the treatment of obesity.
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| 36. |
- Kupferschmidt, Natalia, et al.
(författare)
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Mesoporous silica particles potentiate antigen-specific T-cell responses
- 2014
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Ingår i: Nanomedicine. - 1743-5889 .- 1748-6963. ; 9:12, s. 1835-1846
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Tidskriftsartikel (refereegranskat)abstract
- Aim: To study the adjuvant effect of mesoporous silica particles and their capability of modifying an already existing allergic Th2-like immune response. Materials & methods: The adjuvant effect of Santa Barbara Amorphous-15 (SBA-15) mesoporous silica particles was studied in an antigen-specific ovalbumin (OVA) system in vitro and in vivo. The capacity of the OVA-loaded SBA-15 particles (SBA-15-OVA) to modify an existing immune response was assessed in a murine allergy model. Results: SBA-15-OVA induced significantly stronger OVA-specific splenocyte proliferation compared with OVA alone. Significantly higher IFN-gamma production was observed in ex vivo OVA-stimulated splenocytes from SBA-15-OVA-immunized mice compared with mice injected with only SBA-15 or OVA. Treatment of OVA-sensitized mice with SBA-15-OVA modified the immune response with significantly lower serum levels of OVA-specific IgE and higher IgG levels compared with the alum-OVA-treated group. Conclusion: The results are promising for the continued development of mesoporous silica materials for therapeutic applications.
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| 37. |
- Kupferschmidt, Natalia, et al.
(författare)
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Mesoporous silica particles potentiate antigen specific T cell responses
- 2014
-
Ingår i: Nanomedicine. - : Future Medicine Ltd. - 1743-5889 .- 1748-6963. ; 9:12, s. 1835-1846
-
Tidskriftsartikel (refereegranskat)abstract
- Aim: To study the adjuvant effect of mesoporous silica particles and their capability of modifying an already existing allergic Th2-like immune response. Materials & methods: The adjuvant effect of Santa Barbara Amorphous-15 (SBA-15) mesoporous silica particles was studied in an antigen-specific ovalbumin (OVA) system in vitro and in vivo. The capacity of the OVA-loaded SBA-15 particles (SBA-15-OVA) to modify an existing immune response was assessed in a murine allergy model. Results: SBA-15-OVA induced significantly stronger OVA-specific splenocyte proliferation compared with OVA alone. Significantly higher IFN-γ production was observed in ex vivo OVA-stimulated splenocytes from SBA-15-OVA-immunized mice compared with mice injected with only SBA-15 or OVA. Treatment of OVA-sensitized mice with SBA-15-OVA modified the immune response with significantly lower serum levels of OVA-specific IgE and higher IgG levels compared with the alum-OVA-treated group. Conclusion: The results are promising for the continued development of mesoporous silica materials for therapeutic applications. Original submitted 18 January 2013; Revised submitted 30 August 2013
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| 38. |
- Kupferschmidt, Natalia
(författare)
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Toxicological and Immunomodulatory Properties of Mesoporous Silica Particles : Applications in Life Sciences
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Mesoporous silica particles offer great potential benefits as vehicles for drug delivery and in other biomedical applications. They present a high loading capacity due their ordered and size-tuneable pores that allow molecules to be loaded and released. In addition, they offer the possibility to enhance oral bioavailability of drugs with limited aqueous solubility and to protect pH sensitive drugs from the acidic conditions in the stomach on their way to the intestine.The aim of this thesis was to evaluate the biocompatibility and effects of mesoporous silica particles on immunocompetent cells. Subsequently, two potential life sciences applications were investigated: as adjuvants and as weight reduction agents.Adjuvants are used in vaccines in order to enhance the immunological response towards attenuated and poorly immunogenic antigens. Their function can be mediated through dendritic cells which have a central role in the control of adaptive immunity including immunological memory. Our results show that different types of mesoporous silica particles were able to tune the development of T cells both in human cell cultures and in mice. In contrast to the approved adjuvant alum (aluminium salts) which is a specific inducer of Th2-type immune responses, the particles induced more Th1-like responses, which may be desired in vaccines against allergy and intracellular pathogens such as viruses. Particle exposure to macrophages did not affect their cell function which is crucial for tissue homeostasis, wound repair and in prevention of autoimmune responses. Likewise, the cytokine secretion was not affected, which suggest that macrophages would not modulate the immune response towards the particles.Furthermore, mesoporous silica particles were highly tolerated at daily oral administrations of up to 2000 mg/kg doses for some of the materials prepared. Large pore mesoporous silica particles were shown to act as weight and body fat reduction agents without other observable pathological signs when administered in the diet of obese mice.Together; those results are promising for the development of mesoporous silica as drug delivery systems and adjuvants for oral administration of drugs or vaccines. Additionally, large pore mesoporous silica materials are potential agents for the treatment of obesity.
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| 39. |
- Liu, Qingling, et al.
(författare)
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Aluminophosphates for CO2 Separation
- 2011
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Ingår i: ChemSusChem. - : Wiley. - 1864-5631. ; 4:1, s. 91-97
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Tidskriftsartikel (refereegranskat)abstract
- The pressure-swing adsorption method for carbon dioxide capture would ideally be facilitated by adsorbents with a high capacity and a high selectivity for CO2. Several aluminophosphates with 8-ring window apertures (AlPO4-17, AlPO4-18, AlPO4-53, and AlPO4-25) were synthesized by hydrothermal crystallization, calcined, and their CO2 uptake and CO2/N-2 selectivity were studied. CO2 and N-2 uptake was determined for pressures up to 101 kPa at 273 and 293 K. Langmuir and Toth adsorption models were used to describe the adsorption isotherms. The CO2 and N-2 uptakes strongly indicated that the squeezed 8-ring windows of certain aluminophosphates can sieve CO2 from a CO2 and N-2 gas mixture. Both AlPO4-53 and AlPO4-25 exhibited a remarkably higher uptake of CO2 compared to N-2. The hydrophilicity of the AlPO4 materials was investigated by means of water adsorption, and the results showed that all of the tested aluminophosphates were less water sensitive than a benchmark zeolite (13X). In particular, AlPO4-53 and AlPO4-25 showed a very low degree of water uptake with up to 20-30% relative humidity. Determination of cyclic adsorption and desorption confirmed the relatively hydrophobic nature of the aluminophosphates, which render them less energy costly for the regeneration of adsorbents.
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| 40. |
- Mihranyan, Albert, et al.
(författare)
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A Novel High Specific Surface Area Conducting Paper Material Composed of Polypyrrole and Cladophora Cellulose
- 2008
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 112:39, s. 12249-12255
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Tidskriftsartikel (refereegranskat)abstract
- We present a novel conducting polypyrrole-based composite material, obtained by polymerization of pyrrole in the presence of iron(III) chloride on a cellulose substrate derived from the environmentally polluting Cladophora sp. algae. The material, which was doped with chloride ions, was molded into paper sheets and characterized using scanning and transmission electron microscopy, N2 gas adsorption analysis, cyclic voltammetry, chronoamperometry and conductivity measurements at varying relative humidities. The specific surface area of the composite was found to be 57 m2/g and the fibrous structure of the Cladophora cellulose remained intact even after a 50 nm thick layer of polypyrrole had been coated on the cellulose fibers. The composite could be repeatedly used for electrochemically controlled extraction and desorption of chloride and an ion exchanging capacity of 370 C per g of composite was obtained as a result of the high surface area of the cellulose substrate. The influence of the oxidation and reduction potentials on the chloride ion exchange capacity and the nucleation of delocalized positive charges, forming conductive paths in the polypyrrole film, was also investigated. The creation of conductive paths during oxidation followed an effective medium rather than a percolative behavior, indicating that some conduction paths survive the polymer reduction steps. The present high surface area material should be well-suited for use in, e.g., electrochemically controlled ion exchange or separation devices, as well as sensors based on the fact that the material is compact, light, mechanically stable, and moldable into paper sheets.
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| 41. |
- Shi, Jingwen, et al.
(författare)
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Microsomal Glutathione Transferase 1 Protects Against Toxicity Induced by Silica Nanoparticles but Not by Zinc Oxide Nanoparticles
- 2012
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 6:3, s. 1925-1938
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Tidskriftsartikel (refereegranskat)abstract
- Microsomal glutathione transferase 1 (MGST1) is an antioxidant enzyme located predominantly in the mitochondrial er membrane and endoplasmk reticulum and has been shown to protect cells from lipid peroxidation induced by a variety of cytostatic drugs and pro-oxidant stimuli. We hypothesized that MGST1 may also protect against nanomaterial-induced cytotoxicity through a specific effect on lipid peroxidation. We evaluated the induction of cytotoxicity and oxidative stress by TiO2, CeO2, SiO2, and ZnO in the human MCF-7 cell line with or without overexpression of MGST1. SiO2 and ZnO nanoparticles caused dose- and time-dependent toxicity, whereas no obvious cytotoxic effects were induced by nanoparticles of TiO2 and CeO2. We also noted pronounced cytotoxicity for three out of four additional SiO2 nanoparticles tested. Overexpression of MGST1 reversed the cytotoxicity of the main SiO2 nanoparticles tested and for one of the supplementary SiO2 nanoparticles but did not protect cells against ZnO-induced cytotoxic effects. The data point toward a role of lipid peroxidation In SiO2 nanoparticle-induced cell death. For ZnO nanoparticles, rapid dissolution was observed, and the subsequent interaction of Zn2+ with cellular targets is likely to contribute to the cytotoxic effects. A direct inhibition of MGST1 by Zn2+ could provide a possible explanation for the lack of protection against ZnO nanoparticles in this model. Our data also showed that SiO2 nanoparticle-induced cytotoxicity is mitigated in the presence of serum, potentially through masking of reactive surface groups by serum proteins, whereas ZnO nanoparticles were cytotoxic both In the presence and in the absence of serum.
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| 42. |
- Strømme, Maria, et al.
(författare)
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Proton Absorption in As-Synthesized Mesoporous Silica Nanoparticles as a Structure-Function Relationship Probing Mechanism
- 2009
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 25:8, s. 4306-4310
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Tidskriftsartikel (refereegranskat)abstract
- A new method to investigate the effect of pore geometry on diffusion processes in mesoporous silica nanoparticles and other types of micro- and mesoporous structures is put forward. The method is based onthe study of proton diffusion from a liquid surrounding the mesoporous particles into the particle pore system. The proton diffusion properties are assessed for a variety of as-synthesized mesoporous nano- and microparticles with two-dimensional and three-dimensional connectivity. Results show that the diffusion coefficients are higher for the proton absorption process than for the release of surfactant template molecules, and that they overall follow the same trend with the more complex three-dimensional mesocaged particles showing the highest diffusion coefficients. The pore geometry (cylindrical pores versus cage-type pores) and structure connectivity are found to play a key role for the effects observed. The results put forward in the present work should offer a valuable tool in the development of porous nanomaterials in a range of applications including the use as catalysis and separation enhancers in the petrochemical industry, as scaffolds for hydrogen storage, and as drug delivery vehicles for sustained release and gene transfection.
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| 43. |
- Vallhov, Helen, et al.
(författare)
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Adjuvant Properties of Mesoporous Silica Particles Tune the Development of Effector T Cells
- 2012
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Ingår i: Small. - : John Wiley & Sons. - 1613-6810 .- 1613-6829. ; 8:13, s. 2116-2124
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Tidskriftsartikel (refereegranskat)abstract
- Alum is the most frequently used adjuvant today, primarily inducing Th2 responses. However, Th1-type responses are often desirable within immune therapy, and therefore the development of new adjuvants is greatly needed. Mesoporous silica particles with a highly ordered pore structure have properties that make them very interesting for future controlled drug delivery systems, such as controllable particle and pore size; they also have the ability to induce minor immune modulatory effects, as previously demonstrated on human-monocyte-derived dendritic cells (MDDCs). In this study, mesoporous silica particles are shown to be efficiently engulfed by MDDCs within 2 h, probably by phagocytic uptake, as seen by confocal microscopy and transmission electron microscopy. A co-culture protocol is developed to evaluate the capability of MDDCs to stimulate the development of naive CD4+ T cells in different directions. The method, involving ELISpot as a readout system, demonstrates that MDDCs, after exposure to mesoporous silica particles (AMS-6 and SBA-15), are capable of tuning autologous naive T cells into different effector cells. Depending on the size and functionalization of the particles added to the cells, different cytokine patterns are detected. This suggests that mesoporous silica particles can be used as delivery vehicles with tunable adjuvant properties, which may be of importance for several medical applications, such as immune therapy and vaccination.
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| 44. |
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| 45. |
- Vallhov, Helen, et al.
(författare)
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Mesoporous silica particles induce size dependent effects on human dendritic cells
- 2007
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 7:12, s. 3576-3582
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The effects of mesoporous silica nano- (270 nm) and microparticles (2.5 μm) with surface areas above 500 m2/g were evaluated on human monocyte-derived dendritic cells (MDDC). Size- and concentration-dependent effects were seen where the smaller particles and lower concentrations affected MDDC to a minor degree compared to the larger particles and higher concentrations, both in terms of viability, uptake, and immune regulatory markers. Our findings support the further development of mesoporous silica particles in drug and vaccine delivery systems.
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| 46. |
- Witasp, Erika, et al.
(författare)
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Efficient internalization of mesoporous silica particles of different sizes by primary human macrophages without impairment of macrophage clearance of apoptotic or antibody-opsonized target cells
- 2009
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier BV. - 0041-008X .- 1096-0333. ; 239:3, s. 306-319
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Tidskriftsartikel (refereegranskat)abstract
- Macrophage recognition and ingestion of apoptotic cell corpses, a process referred to as programmed cell clearance, is of considerable importance for the maintenance of tissue homeostasis and in the resolution of inflammation. Moreover, macrophages are the first line of defense against microorganisms and other foreign materials including particles. However, there is sparse information on the mode of uptake of engineered nanomaterials by primary macrophages. In this study, mesoporous silica particles with cubic pore geometries and covalently fluorescein-grafted particles were synthesized through a novel route, and their interactions with primary human monocyte-derived macrophages were assessed. Efficient and active internalization of mesoporous silica particles of different sizes was observed by transmission electron microscopic and flow cytometric analysis and studies using pharmacological inhibitors suggested that uptake occurred through a process of endocytosis. Moreover, uptake of silica particles was independent of serum factors. The silica particles with very high surface areas due to their porous structure did not impair cell viability or function of macrophages, including the ingestion of different classes of apoptotic or opsonized target cells. The current findings are relevant to the development of mesoporous materials for drug delivery and other biomedical applications.
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| 47. |
- Wu, Xiaowei, et al.
(författare)
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The Synthesis of Chiral Periodic Organosilica Materials with Ultrasmall Mesopores
- 2011
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 50:35, s. 8095-8099
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Tidskriftsartikel (refereegranskat)abstract
- Helical organosilica materials were synthesized for the first time using a novel binaphthyl-based chiral co-monomer in less than 1 hour. The incorporation of a chiral co-monomer in the wall was shown to influence the curvature of the helical materials. As the amount of the chiral co-monomer was increased, the degree of curvature increased, illustrating the importance of this monomer to the overall morphology.
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| 48. |
- Xia, Xin, 1984-
(författare)
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Dissolving the Rocks : Solubility Enhancement of Active Pharmaceutical Ingredients using Mesoporous Silica
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Poor aqueous solubility is one of the greatest barriers for new drug candidates to enter toxicology studies, let alone clinical trials. This thesis focuses on contributing to solving this problem, evaluating the oral toxicity of mesoporous silica particles, and enhancing the apparent solubility and bioavailability of active pharmaceutical ingredients in vitro and in vivo using mesoporous silica particles.Toxicological studies in rats showed that two types of mesoporous silica particles given by oral administration were well tolerated without showing clinical signs of toxicity. Solubility enhancement, including in vivo bioavailability and in vitro intracellular activity, has been evaluated for selected drug compounds. Mesoporous silica was shown to effectively increase drug solubility by stabilizing the amorphous state of APIs, such as itraconazole (anti-fungal), dasatinib (anti-cancer), atazanavir (anti-HIV) and PA-824 (anti-tuberculosis). Itraconazole was successfully loaded into a variety of porous silica materials showing a distinct improvement in the dissolution properties in comparison to non-porous silica materials (and the free drug). Microporosity in SBA-15 particles has advantages in stabilizing the supersaturation state of dasatinib. Small pore sizes show better confinement of atazanavir, contributing to a higher dissolution of the drug compound. In the in vivo animal studies, NFM-1 loaded with atazanavir shows a four-fold increase in bioavailability compared to free crystalline atazanavir. PA-824 has a higher dissolution rate and solubility after loading into AMS-6 mesoporous particles. The loaded particles show similar antibacterial activity as the free PA-824.This thesis aims at highlighting some of the important factors enabling the selection of adequate mesoporous structures to enhance the pharmacokinetic profile of poorly water-soluble compounds, and preparing the scientific framework for uncovering the effects of drug confinement within mesopores of varying structural properties.
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| 49. |
- Xia, Xin, et al.
(författare)
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Encapsulation of Anti-Tuberculosis Drugs within Mesoporous Silica and Intracellular Antibacterial Activities
- 2014
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Ingår i: Nanomaterials. - : MDPI AG. - 2079-4991. ; 4:3, s. 813-826
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Tidskriftsartikel (refereegranskat)abstract
- Tuberculosis is a major problem in public health. While new effective treatments to combat the disease are currently under development, they tend suffer from poor solubility often resulting in low and/or inconsistent oral bioavailability. Mesoporous materials are here investigated in an in vitro intracellular assay, for the effective delivery of compound PA-824; a poorly soluble bactericidal agent being developed against Tuberculosis (TB). Mesoporous materials enhance the solubility of PA-824; however, this is not translated into a higher antibacterial activity in TB-infected macrophages after 5 days of incubation, where similar values are obtained. The lack of improved activity may be due to insufficient release of the drug from the mesopores in the context of the cellular environment. However, these results show promising data for the use of mesoporous particles in the context of oral delivery with expected improvements in bioavailability.
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| 50. |
- Xia, Xin, et al.
(författare)
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In vivo Enhancement in Bioavailability of Atazanavir in the Presence of Proton-Pump Inhibitors using Mesoporous Materials
- 2012
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Ingår i: ChemMedChem. - : Wiley. - 1860-7179 .- 1860-7187. ; 7:1, s. 43-8
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Tidskriftsartikel (refereegranskat)abstract
- Matters of the HAART! The current treatment for human immunodeficiency virus (HIV), HAART, makes use of a combination of antiretroviral drugs, which are poorly soluble in aqueous media. Enhancing the solubility of such drugs through the use of mesoporous materials could lead to improved treatment efficiency and might provide a solution to the drug-drug interaction problems associated with these types of therapeutic regimes.
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