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- Glasbey, JC, et al.
(författare)
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- 2021
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swepub:Mat__t
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- Ahlinder, Astrid, et al.
(författare)
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Nondegradative additive manufacturing of medical grade copolyesters of high molecular weight and with varied elastic response
- 2020
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Ingår i: Journal of Applied Polymer Science. - : WILEY. - 0021-8995 .- 1097-4628. ; 137:15
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Tidskriftsartikel (refereegranskat)abstract
- Although additive manufacturing through melt extrusion has become increasingly popular as a route to design scaffolds with complex geometries the technique if often limited by the reduction in molecular weight and the viscoelastic response when degradable aliphatic polyesters of high molecular weight are used. Here we use a melt extruder and fused filament fabrication printer to produce a reliable nondegradative route for scaffold fabrication of medical grade copolymers of L-lactide, poly(epsilon-caprolactone-co-L-lactide), and poly(L-lactide-co-trimethylene carbonate). We show that degradation is avoided using filament extrusion and fused filament fabrication if the process parameters are deliberately chosen based upon the rheological behavior, mechanical properties, and polymer composition. Structural, mechanical, and thermal properties were assessed throughout the process to obtain comprehension of the relationship between the rheological properties and the behavior of the medical grade copolymers in the extruder and printer. Scaffolds with a controlled architecture were achieved using high-molecular-weight polyesters exhibiting a large range in the elastic response causing negligible degradation of the polymers.
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- Eltom, Mohamed A., et al.
(författare)
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Increasing prevalence of type 2 diabetes mellitus and impact of ethnicity in north Sudan
- 2018
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Ingår i: Diabetes Research and Clinical Practice. - : ELSEVIER IRELAND LTD. - 0168-8227 .- 1872-8227. ; 136, s. 93-99
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Tidskriftsartikel (refereegranskat)abstract
- Background: Diabetes mellitus constitutes a global health threat, with increasing burden of disease in low and middle-income countries witnessing ongoing epidemiological transition including Sudan.Aims: To study the prevalence of type 2 diabetes mellitus (T2DM) and prediabetes and determine the relationship to gender, age, waist circumference, body mass index, residence and ethnicity among the adult population in north Sudan.Methods: A cross-sectional, population-based study in Northern State and River Nile State using random multi-stage cluster sampling targeting 5376 participants from 14 localities divided into 60 urban and 40 rural clusters. In each cluster, 60 households were studied. Blood glucose level and anthropometric measurements were recorded and a questionnaire containing demographic data was obtained from each participant.Results: The prevalence of T2DM among participants was 18.7% and prediabetes was 12.9%. Among people living with T2DM, 694(71.0%) were known cases of T2DM, whereas 284 (29.0%) were newly diagnosed cases. The significant associated risk factors for T2DM included urban residence (AOR 1.23, 95% CI 1.09-1.41), age above 60 years (AOR 4.77, 95% CI 4.04-5.63), obese BMI (AOR 1.26, 95% CI 1.03-1.55) and central obesity (AOR 1.39, 95% CI 1.14-1.68). Compared to indigenous population, individuals of Egyptian descents (AOR 1.28, 95% CI 1.04-1.57) and mixed origin (AOR 1.24, 95% CI 1.04-1.48) had increased risk of T2DM.Conclusion: The prevalence of T2DM and prediabetes in north Sudan have increased significantly since 1996 with variations between ethnicities which showed to be an independent risk factor for T2DM. Health authorities are recommended to set plans to meet the health needs of these communities.
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- Gjerde, Cecilie, et al.
(författare)
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Cell therapy induced regeneration of severely atrophied mandibular bone in a clinical trial
- 2018
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Ingår i: Stem Cell Research & Therapy. - : BMC. - 1757-6512. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Background: Autologous grafting, despite some disadvantages, is still considered the gold standard for reconstruction of maxillofacial bone defects. The aim of this study was to evaluate bone regeneration using bone marrow-derived mesenchymal stromal cells (MSCs) in a clinical trial, a less invasive approach than autologous bone grafting. This comprehensive clinical trial included subjects with severe mandibular ridge resorption. Methods: The study included 11 subjects aged 52-79 years with severe mandibular ridge resorption. Bone marrow cells were aspirated from the posterior iliac crest and plastic adherent cells were expanded in culture medium containing human platelet lysate. The MSCs and biphasic calcium phosphate granules as scaffolds were inserted subperiosteally onto the resorbed alveolar ridge. After 4-6 months of healing, new bone formation was assessed clinically and radiographically, as were safety and feasibility. Bone at the implant site was biopsied for micro computed topography and histological analyses and dental implants were placed in the newly regenerated bone. Functional outcomes and patient satisfaction were assessed after 12 months. Results: The bone marrow cells, expanded in vitro and inserted into the defect together with biphasic calcium phosphate granules, induced significant new bone formation. The regenerated bone volume was adequate for dental implant installation. Healing was uneventful, without adverse events. The patients were satisfied with the esthetic and functional outcomes. No side effects were observed. Conclusions: The results of this comprehensive clinical trial in human subjects confirm that MSCs can successfully induce significant formation of new bone, with no untoward sequelae. Hence, this novel augmentation procedure warrants further investigation and may form the basis of a valid treatment protocol, challenging the current gold standard.
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- Jain, Shubham, et al.
(författare)
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Engineering 3D degradable, pliable scaffolds toward adipose tissue regeneration; optimized printability, simulations and surface modification
- 2020
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Ingår i: Journal of Tissue Engineering. - : SAGE Publications. - 2041-7314. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- We present a solution to regenerate adipose tissue using degradable, soft, pliable 3D-printed scaffolds made of a medical-grade copolymer coated with polydopamine. The problem today is that while printing, the medical grade copolyesters degrade and the scaffolds become very stiff and brittle, being not optimal for adipose tissue defects. Herein, we have used high molar mass poly(L-lactide-co-trimethylene carbonate) (PLATMC) to engineer scaffolds using a direct extrusion-based 3D printer, the 3D Bioplotter (R). Our approach was first focused on how the printing influences the polymer and scaffold's mechanical properties, then on exploring different printing designs and, in the end, on assessing surface functionalization. Finite element analysis revealed that scaffold's mechanical properties vary according to the gradual degradation of the polymer as a consequence of the molar mass decrease during printing. Considering this, we defined optimal printing parameters to minimize material's degradation and printed scaffolds with different designs. We subsequently functionalized one scaffold design with polydopamine coating and conducted in vitro cell studies. Results showed that polydopamine augmented stem cell proliferation and adipogenic differentiation owing to increased surface hydrophilicity. Thus, the present research show that the medical grade PLATMC based scaffolds are a potential candidate towards the development of implantable, resorbable, medical devices for adipose tissue regeneration.
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| 9. |
- Jain, Shubham, et al.
(författare)
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Printability and Critical Insight into Polymer Properties during Direct-Extrusion Based 3D Printing of Medical Grade Polylactide and Copolyesters
- 2020
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Ingår i: Biomacromolecules. - : AMER CHEMICAL SOC. - 1525-7797 .- 1526-4602. ; 21:2, s. 388-396
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Forskningsöversikt (refereegranskat)abstract
- Various 3D printing techniques currently use degradable polymers such as aliphatic polyesters to create well-defined scaffolds. Even though degradable polymers are influenced by the printing process, and this subsequently affects the mechanical properties and degradation profile, degradation of the polymer during the process is not often considered. Degradable scaffolds are today printed and cell-material interactions evaluated without considering the fact that the polymer change while printing the scaffold. Our methodology herein was to vary the printing parameters such as temperature, pressure, and speed to define the relationship between printability, polymer microstructure, composition, degradation profile during the process, and rheological behavior. We used high molecular weight medical-grade (co)polymers, poly(L-lactide-co-epsilon-caprolactone) (PCLA), poly(L-lactide-co-glycolide) (PLGA), and poly(D,L-lactide-co-glycolide) (PDLGA), with L-lactide content ranging from 25 to 100 mol %, for printing in an extrusion-based printer (3D Bioplotter). Optical microscopy confirmed that the polymers were printable at high resolution and good speed, until a certain degree of degradation. The results show also that printability can not be claimed just by optimizing printing parameters and highlight the importance of a careful analysis of how the polymer's structure and properties vary during printing. The polymers thermally decomposed from the first processing minute and caused a decrease in the average block length of the lactide blocks in the copolymers and generated lower crystallinity. Poly(L-lactide) (PLLA) and PCLA are printable at a higher molecular weight, less degradation before printing was possible, compared to PLGA and PDLGA, a result explained by the higher complex viscosity and more elastic polymeric melt of the copolymer containing glycolide (GA) and lactide (LA). In more detail, copolymers comprised of LA and epsilon-caprolactone (CL) formed lower molecular weight compounds over the course of printing, while the PLGA copolymer was more susceptible to intermolecular transesterification reactions, which do not affect the overall molecular weight, but cause changes in the copolymer microstructure. This results in a longer printing time for PLGA than PLLA and PCLA.
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| 10. |
- Jain, Shubham, et al.
(författare)
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Understanding of how the properties of medical grade lactide based copolymer scaffolds influence adipose tissue regeneration : Sterilization and a systematic in vitro assessment
- 2021
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Ingår i: Materials science & engineering. C, biomimetic materials, sensors and systems. - : Elsevier BV. - 0928-4931 .- 1873-0191. ; 124
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Tidskriftsartikel (refereegranskat)abstract
- Aliphatic polyesters are the synthetic polymers most commonly used in the development of resorbable medical implants / devices. Various three-dimensional (3D) scaffolds have been fabricated from these polymers and used in adipose tissue engineering. However, their systematic evaluation altogether lacks, which makes it difficult to select a suitable degradable polymer to design 3D resorbable implants and / or devices able to effectively mimic the properties of adipose tissue. Additionally, the impact of sterilization methods on the medical devices, if any, must be taken into account. We evaluate and compare five different medical-grade resorbable polyesters with l-lactide content ranging from 50 to 100 mol% and exhibiting different physiochemical properties depending on the comonomer (d-lactide, ε-caprolactone, glycolide, and trimethylene carbonate). The salt-leaching technique was used to prepare 3D microporous scaffolds. A comprehensive assessment of the physical, chemical, and mechanical properties of the scaffolds was carried out in PBS at 37 ° C. The cell-material interactions and the ability of the scaffolds to promote adipogenesis of human adipose tissue-derived stem cells were assessed in vitro. The diverse physical and mechanical properties of the scaffolds, due to the different composition of the copolymers, influenced human adipose tissue-derived stem cells proliferation and differentiation. Scaffolds made from polymers which were above their glass transition temperature and with low degree of crystallinity showed better proliferation and adipogenic differentiation of stem cells. The effect of sterilization techniques (electron beam and ethylene oxide) on the polymer properties was also evaluated. Results showed that scaffolds sterilized with the ethylene oxide method better retained their physical and chemical properties. Overall, the presented research provides (i) a detailed understanding to select a degradable polymer that has relevant properties to augment adipose tissue regeneration and can be further used to fabricate medical devices / implants; (ii) directions to prefer a sterilization method that does not change polymer properties. the presented research provides (i) a detailed understanding to select a degradable polymer that has relevant properties to augment adipose tissue regeneration and can be further used to fabricate medical devices / implants; (ii) directions to prefer a sterilization method that does not change polymer properties. the presented research provides (i) a detailed understanding to select a degradable polymer that has relevant properties to augment adipose tissue regeneration and can be further used to fabricate medical devices / implants; (ii) directions to prefer a sterilization method that does not change polymer properties.
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