| 1. |
- Aminlashgari, Nina, et al.
(författare)
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Characterization of degradation fragments released by arc-induced ablation of polymers in air
- 2016
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Ingår i: Journal of Physics D. - : Institute of Physics Publishing (IOPP). - 0022-3727 .- 1361-6463. ; 49:5
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Tidskriftsartikel (refereegranskat)abstract
- Polymers exposed to high intensity arc plasmas release material in a process called arc-induced ablation. In order to investigate the degradation fragments released due to this process, two different polymeric materials, poly(oxymethylene) copolymer (POM-C) and poly(methyl methacrylate) (PMMA), were exposed to a transient, high-power arc plasma in air. A small fraction of the ablated material drifting away from the arcing volume was deposited on a fixed glass substrate during the total duration of a 2 kA ac current semicycle. In addition, another fraction of the released material was deposited on a second moving substrate to obtain a time-resolved streak 'image' of the arc-induced ablation process. For the first time, mass spectra of degradation fragments produced by arc-induced ablation were obtained from the material deposited on the substrates by using laser desorption ionization time-of-flight mass spectrometry (LDI-ToF-MS). It was found that oligomers with mean molecular weight ranging between 400 and 600 Da were released from the surface of the studied polymers. The obtained spectra suggest that the detected degradation fragments of POM could be released by random chain scission of the polymer backbone. In turn, random chain scission and splitting-off the side groups are suggested as the main chemical mechanism leading to the release of PMMA fragments under arc-induced ablation.
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| 2. |
- Aminlashgari, Nina, et al.
(författare)
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Degradation product profiles of melt spun in situ cross-linked poly(epsilon-caprolactone) fibers
- 2015
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Ingår i: Materials Chemistry and Physics. - : Elsevier BV. - 0254-0584 .- 1879-3312. ; 156, s. 82-88
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Tidskriftsartikel (refereegranskat)abstract
- In situ cross-linking of poly(epsilon-caprolactone) (PCL) fiber with bis-(epsilon-caprolactone-4-yl) (BCY) was shown to be a feasible approach to compensate for reduction in molar mass of PCL during melt-spinning. The effect of in situ cross-linking on the degradation profile of melt spun PCL fibers with different amounts of BCY was evaluated using electrospray ionization-mass spectrometry. Degradation of the cross-linked fibers was carried out in aqueous medium at 37 degrees C and 60 degrees C for different periods of time. The degradation profiles were then compared with uncross-linked fiber and 3D porous cross-linked film of PCL Interesting differences in the degradation product profiles with linear, cyclic or BCY-related low molar mass compounds were observed, clearly demonstrating the effect of cross-linking and processing on the degradation process and formation of water-soluble products. In addition the degradation product profiles demonstrated that in situ cross-linking is a feasible technique for counteracting degradation reactions during melt-spinning.
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| 3. |
- Aminlashgari, Nina, et al.
(författare)
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Degradation profile and preliminary clinical testing of a resorbable device for ligation of blood vessels
- 2013
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Ingår i: Acta Biomaterialia. - : Elsevier BV. - 1742-7061 .- 1878-7568. ; 9:6, s. 6898-904
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Tidskriftsartikel (refereegranskat)abstract
- A resorbable device for ligation of blood vessels was developed and tested in vitro to reveal the degradation profile of the device and to predict the clinical performance in terms of adequate mechanical support during a healing period of I week. In addition, preliminary clinical testing was performed that showed complete hemostasis and good tissue grip of renal arteries in five pigs. The device was made by injection molding of poly(glycolide-co-trimethylene carbonate) triblock copolymer, and it consisted of a case with a locking mechanism connected to a partly perforated flexible band. A hydrolytic degradation study was carried out for 7, 30 and 60 days in water and buffer medium, following the changes in mass, water absorption, pH and mechanical properties. A new rapid matrix-free laser desorption ionization-mass spectrometry (LDI-MS) method was developed for direct screening of degradation products released into the degradation medium. The combination of LDI-MS and electrospray ionization-mass spectrometry analyses enabled the comparison of the degradation product patterns in water and buffer medium. The identified degradation products were rich in trimethylene carbonate units, indicating preferential hydrolysis of amorphous regions where trimethylene units are located. The crystallinity of the material was doubled after 60 days of hydrolysis, additionally confirming the preferential hydrolysis of trimethylene carbonate units and the enrichment of glycolide units in the remaining solid matrix. The mechanical performance of the perforated band was followed for the first week of hydrolysis and the results suggest that sufficient strength is retained during the healing time of the blood vessels.
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| 4. |
- Aminlashgari, Nina, et al.
(författare)
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Emerging Mass Spectrometric Tools for Analysis of Polymers and Polymer Additives
- 2012
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Ingår i: Advances in Polymer Science. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 0065-3195 .- 1436-5030. - 9783642280405 ; 248, s. 1-38
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Tidskriftsartikel (refereegranskat)abstract
- The field of mass spectrometry has experienced enormous developments in the last few years. New interesting mass spectrometric techniques have arrived and there have been further developments in the existing methods that have opened up new possibilities for the analysis of increasingly complex polymer structures and compositions. Some of the most interesting emerging techniques for polymer analysis are briefly reviewed in this paper. These include new developments in laser desorption ionization techniques, like solvent-free matrix-assisted laser desorption ionization (solvent-free MALDI) and surface-assisted laser desorption ionization (SALDI) mass spectrometry, and the developments in secondary ion mass spectrometry (SIMS), such as gentle-SIMS and cluster SIMS. Desorption electrospray ionization (DESI) mass spectrometry and direct analysis in real time (DART) mass spectrometry offer great possibilities for analysis of solid samples in their native form, while mobility separation prior to mass spectrometric analysis in ion mobility spectrometry (IMS) mass spectrometry further facilitates the analysis of complex polymer structures. The potential of these new developments is still largely unexplored, but they will surely further strengthen the position of mass spectrometry as an irreplaceable tool for polymer characterization.
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| 5. |
- Aminlashgari, Nina, 1984-
(författare)
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LDI-MS strategies for analysis of polymer degradation products, additives and drugs
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The advancement of mass spectrometry (MS) has been and continues to be a prominent analytical technique for highly accurate determination of analytes. The goal of this thesis was to develop new laser desorption ionization-mass spectrometric (LDI-MS) methods for analysis of polymer degradation products, additives and drugs. Modifications in the sample preparation were evaluated in the presence and absence of surface assisting materials. Various nanoparticles were evaluated as effective absorbents for energy transfer in the LDI procedure of the small molecules.In paper I and II, LDI-MS methods were developed for following the progression of chemical reactions. First, the procedure to optimize microwave assisted hydrothermal degradation products of cellulose were analyzed; second, the synthesis of glucose hexanoate ester plasticizers was monitored as a function of reaction time. The LDI-MS method provided rapid detection for the elucidation of the chemical products and their relative ratios. In contrast, the electrospray ionization-mass spectrometry (ESI-MS) analysis produced a noisy spectrum primarily containing peaks from salt clusters. A surface assisted laser desorption ionization-mass spectrometry (SALDI-MS) method was developed in paper III enabling the identification of poly(e-caprolactone) and its degradation products by using nanoparticles as the substrate. Similar analysis by matrix assisted laser desorption ionization-mass spectrometry (MALDI-MS) was not as successful due to convolution of the analyte peaks with clusters released from the matrix. ESI-MS analysis verified the SALDI-MS method as comparable degradation product patterns were observed. Furthermore, the possibility of using polylactide based nanocomposites as surfaces in the analysis of drugs was evaluated in paper IV. An advantage was the ease of handling compared to the use of free nanoparticles. Paper V introduces the potential of direct examination of oxygen plasma modified parylene C surfaces by a LDI-MS methodology.
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| 6. |
- Aminlashgari, Nina, et al.
(författare)
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Nanocomposites as novel surfaces for laser desorption ionization mass spectrometry
- 2011
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Ingår i: Analytical Methods. - : Royal Society of Chemistry (RSC). - 1759-9660 .- 1759-9679. ; 3:1, s. 192-197
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Tidskriftsartikel (refereegranskat)abstract
- The possibility to utilize nanocomposite films as easy-to-handle surfaces for surface assisted laser desorption ionization-mass spectrometry (SALDI-MS) of small molecules, such as pharmaceutical compounds, was evaluated. The signal-to-noise values of acebutolol, propranolol and carbamazepine obtained on the nanocomposite surfaces were higher than the values obtained on plain PLA surface showing that the nanoparticles participate in the ionization/desorption process even when they are immobilized in the polymer matrix. The advantages of nanocomposite films compared to the free nanoparticles used in earlier studies are the ease of handling and reduction of instrument contamination since the particles are immobilized into the polymer matrix. Eight inorganic nanoparticles, titanium dioxide, silicon dioxide, magnesium oxide, hydroxyapatite, montmorillonite nanoclay, halloysite nanoclay, silicon nitride and graphitized carbon black at different concentrations were solution casted to films with polylactide (PLA). There were large differences in signal intensities depending on the type of drug, type of nanoparticle and the concentration of nanoparticles. Polylactide with 10% titanium oxide or 10% silicon nitride functioned best as SALDI-MS surfaces. The limit of detection (LOD) for the study was ranging from 1.7 ppm up to 56.3 ppm and the signal to noise relative standard deviations for the surface containing 10% silicon nitride was approximately 20-30%. Scanning electron microscopy demonstrated in most cases a good distribution of the nanoparticles in the polymer matrix and contact angle measurements showed increasing hydrophobicity when the nanoparticle concentration was increased, which could influence the desorption and ionization. Overall, the results show that nanocomposite films have potential as surfaces for SALDI-MS analysis of small molecules.
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| 7. |
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| 8. |
- Aminlashgari, Nina, 1986-
(författare)
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SALDI-MS Method Development for Analysis of Pharmaceuticals and Polymer Degradation Products
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Surface assisted laser desorption ionization-mass spectrometry (SALDI-MS) was evaluated as a new tool for analysis of polymer degradation products. A SALDI method was developed enabling rapid analysis of low molecular mass polyesters and their degradation products. In addition, the possibility to utilize nanocomposite films as easy-to-handle surfaces for analysis of pharmaceutical compounds was investigated. Poly(ε-caprolactone) was used as a model compound for SALDI-MS method development. The signal-to-noise values obtained by SALDI-MS were 20 times higher compared to traditional matrix assisted laser desorption ionization-mass spectrometry (MALDI-MS) of the same samples with 2,5-dihydroxybenzoic acid as a matrix. Halloysite nanoclay and magnesium oxide showed best potential as surfaces and clean backgrounds in the low mass range were observed. The SALDI-MS method for the analysis of polyester degradation products was also verified by electrospray ionization-mass spectrometry (ESI-MS). An advantage over ESI-MS is the possibility to directly analyze degradation products in buffer solutions. Compared to gas chromatography-mass spectrometry (GC-MS) it is possible to analyze polar compounds and larger molecular mass ranges at the same time as complicated extraction steps are avoided. The possibility to use nanocomposite films as surfaces instead of free nanoparticles was evaluated by solution casting of poly(lactide) (PLA) films with eight inorganic nanoparticles. The S/N values of the pharmaceutical compounds, acebutolol, propranolol and carbamazepine, analyzed on the nanocomposite surfaces were higher than the values obtained on the surface of plain PLA showing that the nanoparticles participated in the ionization/desorption process even when they are immobilized. Beside the ease of handling, the risk for instrument contamination is reduced when nanocomposites are used instead of free nanoparticles. The signal intensities depended on the type of drug, type and concentration of nanoparticle. PLA with 10 % titanium oxide or 10 % silicon nitride functioned best as SALDI-MS surfaces.
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| 9. |
- Aminlashgari, Nina, et al.
(författare)
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Surface Assisted Laser Desorption Ionization-Mass Spectrometry (SALDI-MS) for Analysis of Polyester Degradation Products
- 2012
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Ingår i: Journal of the American Society for Mass Spectrometry. - : American Chemical Society (ACS). - 1044-0305 .- 1879-1123. ; 23:6, s. 1071-1076
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Tidskriftsartikel (refereegranskat)abstract
- Novel surface assisted laser desorption ionization-mass spectrometry (SALDI-MS) method was developed for rapid analysis of low molecular mass polyesters and their degradation products by laser desorption ionization-mass spectrometry. Three polycaprolactone materials were analyzed by the developed method before and after hydrolytic degradation. The signal-to-noise values obtained by SALDI-MS were 20-100 times higher compared with the ones obtained by using traditional MALDI-MS matrices. A clean background at low mass range and higher resolution was obtained by SALDI-MS. Different nanoparticle, cationizing agent, and solvent combinations were evaluated. Halloysite nanoclay and magnesium hydroxide showed the best potential as SALDI surfaces. The SALDI-MS spectrum of the polyester hydrolysis products was verified by ESI-MS. The developed SALDI-MS method possesses several advantages over existing methods for similar analyses.
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| 10. |
- Golda-Cepa, M., et al.
(författare)
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LDI-MS examination of oxygen plasma modified polymer for designing tailored implant biointerfaces
- 2014
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 4:50, s. 26240-26243
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Tidskriftsartikel (refereegranskat)abstract
- A versatile polymer coating for biomaterials was fabricated by the mild oxygen plasma treatment of Chemical Vapour Deposited (CVD) parylene C. The surface properties were tailored while the excellent protective properties of the bulk were preserved. The species, formed due to the plasma functionalisation, were fingerprinted by a novel Laser Desorption/Ionisation-Mass Spectrometry (LDI-MS) method. Improved osteosarcoma cells (line MG-63) attachment and viability on a modified surface were demonstrated.
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