| 1. |
- Martinez-Sanz, Elena, et al.
(författare)
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Minimally invasive mandibular bone augmentation using injectable hydrogels
- 2012
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Ingår i: Journal of Tissue Engineering and Regenerative Medicine. - : Hindawi Limited. - 1932-6254. ; 6:S3, s. s15-s23
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Tidskriftsartikel (refereegranskat)abstract
- Hyaluronic acid-based hydrogels are proven biocompatible materials and excellent carriers of bone morphogenetic protein-2 (BMP-2) that have been successfully tested for bone generation in vivo. Different formulations, with or without nanohydroxyapatite, have shown promise for craniofacial applications. In this study, 28 rats were used to investigate whether it is possible to achieve mandibular bone augmentation upon injection of novel hyaluronic acid-based hydrogels containing nanohydroxyapatite and different concentrations of BMP-2 (0, 5 and 150ÎŒg/ml). The biomaterials were injected subperiosteally through fine needles into the innate mandibular diastema, imitating a clinical procedure for resorbed mandibles. No incisions, flaps or sutures were necessary. After 8weeks the mandibles were evaluated by peripheral quantitative computed tomography (pQCT), micro-computed tomography (ÎŒCT), histology, immunohistochemistry and fluorochrome labelling. As a result, engineered bone was observed in all treated mandibles, with a statistically significant increase in mandibular bone volume correlated with the amount of BMP-2 loaded in the hydrogel formula. We therefore demonstrated that minimally invasive mandibular bone augmentation is possible upon injection in rats, when using the appropriate injectable scaffolds. This represents an attractive clinical alternative for oral implantology patients.
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| 2. |
- Martinez-Sanz, Marta, et al.
(författare)
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Development of bacterial cellulose nanowhiskers reinforced EVOH composites by electrospinning
- 2012
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 124:2, s. 1398-1408
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Tidskriftsartikel (refereegranskat)abstract
- In the current study, hybrid electrospun ethylene vinyl alcohol (EVOH) fibers reinforced with bacterial cellulose nanowhiskers (BCNW) were developed and characterized. Additionally, electrospinning was suggested as a method for the incorporation of well-dispersed BCNW into an EVOH matrix by melt compounding. With the aim of maximizing the BCNW's loading in the electrospun fibers, an optimized method was applied for generating fibers from solutions containing up to 40 wt % BCNW. As demonstrated by FTIR spectroscopy, it was possible to incorporate BCNW concentrations up to similar to 24 wt %, although a complete incorporation of the nanofiller into the fibers was only achieved with solutions containing up to 20 wt % of the filler, DSC analyses suggested that the incorporation of the nanofiller reduced the crystallinity of the as-obtained EVOH fibers and produced an increase in the glass transition temperature of these during the second heating run. Thermogravimetric analyses showed that even though EVOH protects the nanowhiskers from thermal degradation, the electrospun hybrid fibers present a relatively lower thermal stability than the pure EVOH fibers. FTIR analyses of the samples subjected to different thermal treatments confirmed that the stiffening effect observed by DSC only occurs after melting of the EVOH phase and is cooperative with a partial acid chemical development in the BCNW, which promotes strong chemical interactions between the polymeric matrix and the nanofiller. Finally, the hybrid electrospun fibers were incorporated into pure EVOH by melt compounding to produce composite films. This methodology showed higher stability and dispersion of the BCNW than direct addition of the freeze-dried nanofiller to EVOH.
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| 3. |
- Martinez-Sanz, Marta, et al.
(författare)
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Development of electrospun EVOH fibres reinforced with bacterial cellulose nanowhiskers. Part I : Characterization and method optimization
- 2011
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Ingår i: Cellulose. - DORDRECHT : SPRINGER. - 0969-0239 .- 1572-882X. ; 18:2, s. 335-347
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, hybrid electrospun EVOH fibres reinforced with bacterial cellulose nanowhiskers (BCNW) were developed and characterized. The nanowhiskers, obtained by sulphuric acid digestion of native bacterial cellulose mats generated by Gluconacetobacter xylinum, were morphologically characterized by SEM and optical microscopy with polarized light and revealed a highly crystalline structure of nanofibrils aggregates. XRD analyses suggested a crystalline structure corresponding to the cellulose I allomorph. It was also confirmed by means of FT-IR spectroscopy that amorphous regions were preferentially digested by the acid treatment, whereas TGA analyses showed a decrease in the thermal stability of the nanowhiskers most likely due to incorporation of sulphate groups and the inherent acidity remaining in the filler even after extensive washing cycles. A method was developed for improving the incorporation of BCNW within the EVOH electrospun fibres, consisting on the addition of the BCNW in the form of a centrifuged precipitate, versus the most conventionally employed freeze-dried nanowhiskers. DSC analyses showed a significant increase in the glass transition temperature of the composites during the second heating run, which may be related to the acidic character of the nanofiller. Finally, sonication was seen to enhance interfacial interaction but to reduce the incorporation of the filler in the matrix in the case of the centrifuged material.
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| 4. |
- Varghese, Oommen P., et al.
(författare)
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Synthesis of Guanidinium-Modified Hyaluronic Acid Hydrogel
- 2010
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Ingår i: Macromolecular rapid communications. - : Wiley. - 1022-1336 .- 1521-3927. ; 31:13, s. 1175-1180
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Tidskriftsartikel (refereegranskat)abstract
- In this report, a new guanidinylating reagent is presented, which was developed without any protection/deprotection strategy and was successfully employed for linking to hyaluronan in aqueous solution. The dually functionalised HA biopolymer bearing guanidinium and hydrazide groups was synthesised to form hydrogel in Ho less than a minute when mixed with aldehyde-modified HA. This hydrogel exhibited higher storage modulus with enhanced stability in PBS when compared to the non-guanidine-containing gel. The gel shift assay showed that this biopolymer formed a stable complex with DNA as well as efficient gene transfection to cells that express HA-receptor CD44. The toxicity studies of this polymer with fibroblast cells revealed that the cells were almost 80% viable after 4 d of incubation at high HA concentration (2.5 x 10(-3) m).
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| 5. |
- Vilaplana, Francisco, et al.
(författare)
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Emission pattern of semi-volatile organic compounds from recycled styrenic polymers using headspace solid-phase microextraction gas chromatography-mass spectrometry
- 2010
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1217:3, s. 359-367
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Tidskriftsartikel (refereegranskat)abstract
- The emission of low molecular weight compounds from recycled high-impact polystyrene (HIPS) has been investigated using headspace solid-phase microextraction (HS-SPME) and gas chromatography-mass Spectrometry (GC-MS). Four released target analytes (styrene, benzaldehyde, acetophenone, and 2-phenylpropanal) were selected for the optimisation of the HS-SPME sampling procedure, by analysing operating parameters such as type of SPME fibre (polarity and operating mechanism), particle size, extraction temperature and time. 26 different compounds were identified to be released at different temperatures from recycled HIPS, including residues of polymerisation, oxidated derivates of styrene, and additives. The type of SPME fibre employed in the sampling procedure affected the detection of emitted components. An adsorptive fibre such as carbowax/polydimethylsiloxane (CAR/PDMS fibre) offered good selectivity for both non-polar and polar volatile compounds at lower temperatures: higher temperatures result ill interferences from less-volatile released compounds. An absorptive fibre as polydimethylsiloxane (PDMS) fibre is Suitable for the detection of less-volatile non-polar molecules at higher temperatures. The nature and relative amount of the emitted compounds increased with higher exposure temperature and smaller polymeric particle size. HS-SPME proves to be a suitable technique for screening the emission of semi-volatile organic compounds (SVOCs) from polymeric materials; reliable quantification of the content of target analytes in recycled HIPS is however difficult due to the complex mass-transfer processes involved, matrix effects, and the difficulties in equilibrating the analytical system.
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