| 1. |
- El-Sayed, Ashraf S. A., et al.
(author)
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Aspergillus nidulans thermostable arginine deiminase-Dextran conjugates with enhanced molecular stability, proteolytic resistance, pharmacokinetic properties and anticancer activity
- 2019
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In: Enzyme and microbial technology. - : Elsevier. - 0141-0229 .- 1879-0909. ; 131
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Journal article (peer-reviewed)abstract
- The potential anticancer activity of arginine deiminase (ADI) via deimination of L-arginine into citrulline has been extensively verified against various arginine-auxotrophic tumors, however, the higher antigenicity, structural instability and in vivo proteolysis are the major challenges that limit this enzyme from further clinical implementation. Since, this clinically applied enzyme was derived from Mycobacterium spp, thus, searching for ADI from eukaryotic microbes "especially thermophilic fungi" could have a novel biochemical conformational and catalytic properties. Aspergillus nidulans ADI was purified with 5.3 folds, with molecular subunit structure 48 kDa and entire molecular mass 120 kDa, ensuring its homotrimeric identity. The peptide fingerprinting analysis revealing the domain Glu(95)-Gly(96)-Gly(97) as the conserved active site of A. nidulans ADI, with higher proximity to Mycobacterium ADI Glade IV. In an endeavor to fortify the structural stability and anticancer activity of A. nidulans ADI, the enzyme was chemically modified with dextran. The optimal activity of Dextran-ADI conjugates was determined at 0.08:20 M ratio of ADI: Dextran, with an overall increase to ADI molecular subunit mass to (similar to)100 kDa. ADI was conjugated with dextran via the a-amino groups interaction of surface lysine residues of ADI. The resistance of Dextran-ADI conjugate to proteolysis had been increased by 2.5 folds to proteinase K and trypsin, suggesting the shielding of > 50% of ADI surface proteolytic recognition sites. The native and Dextran-ADI conjugates have the same optimum reaction temperature (37 degrees C), reaction pH and pH stability (7.0-8.0) with dependency on K+ ions as a cofactor. Dextran-ADI conjugates exhibited a higher thermal stability by (similar to) 2 folds for all the tested temperatures, ensuring the acquired structural and catalytic stability upon dextran conjugation. Dextran conjugation slightly protect the reactive amino and thiols groups of surface amino acids of ADI from amino acids suicide inhibitors. The affinity of ADI was increased by 5.3 folds to free L-arginine with a dramatic reduction in citrullination of peptidylarginine residues upon dextran conjugation. The anticancer activity of ADI to breast (MCF-7), liver (HepG-2) and colon (HCTB, HT29, DLD1 and LS174 T) cancer cell lines was increased by 1.7 folds with dextran conjugation in vitro. Pharmacokinetically, the half-life time of ADI was increased by 1.7 folds upon dextran conjugation, in vivo. From the biochemical and hematological parameters, ADIs had no signs of toxicity to the experimental animals. In addition to the dramatic reduction of L-arginine in serum, citrulline level was increased by 2.5 folds upon dextran conjugation of ADI. This is first report exploring thermostable ADI from thermophilic A. nidulans with robust structural stability, catalytic efficiency and proteolytic resistance.
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| 2. |
- Tabbara, A., et al.
(author)
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Evaluation of apical dimension, canal taper and maintenance of root canal morphology using XP-endo shaper
- 2019
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In: Journal of Contemporary Dental Practice. - : Jaypee Brothers Medical Publishers (P) Ltd. - 1526-3711. ; 20:2, s. 136-144
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Journal article (peer-reviewed)abstract
- To evaluate the shaping ability of the XP-endo shaper file system in maxillary molars, representing root canals with variation in morphology. Materials and methods: Twenty maxillary molars were instrumented according to recommended protocols. Pre- and postoperative microcomputed tomography (CT) scans were performed and the root canals classified according to canal type and curvature. The volume change, number of strokes needed to prepare the canals and the size of the 0.04-tapered gutta-percha cone that was adapted in the canal were recorded. Results: XP-endo shapercreated a significant change in volume after instrumentation in all the canals, with the biggest change found in the DB canals, followed by the MB1 and the P canals, both at full length and in the apical 4 mm. The number of strokes needed to achieve working length and final shape did not differ between the various root canals. Although not significant, the number of strokes needed to prepare the root canal increased with severity of the curvature, but the severity of the curvature did not result in increased removal of dentin in the apical 4 mm. It was possible to achieve a final root canal size where a 0.04-tapered gutta-percha cone could be adapted. Conclusion: The XP-endo shaper was a safe and effective instrument to achieve a root canal preparation of at least size 30 and a 0.04 taper. Clinical significance: The clinical performance of XP-endo shaper was to some extent dependent on preoperative volume and curvature of the root canal.
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| 3. |
- Yassin, Mohammed A., et al.
(author)
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Cell seeding density is a critical determinant for copolymer scaffolds-induced bone regeneration
- 2015
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In: Journal of Biomedical Materials Research. Part A. - : Wiley. - 1549-3296 .- 1552-4965. ; 103:11, s. 3649-3658
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Journal article (peer-reviewed)abstract
- Constructs intended for bone tissue engineering (TE) are influenced by the initial cell seeding density. Therefore, the objective of this study was to determine the effect of bone marrow stromal stem cells (BMSCs) density loaded onto copolymer scaffolds on bone regeneration. BMSCs were harvested from rat's bone marrow and cultured in media with or without osteogenic supplements. Cells were seeded onto poly(l-lactide-co-epsilon-caprolactone) [poly(LLA-co-CL)] scaffolds at two different densities: low density (1 x 10(6) cells/scaffold) or high density (2 x 10(6) cells/scaffold) using spinner modified flasks and examined after 1 and 3 weeks. Initial attachment and spread of BMSC onto the scaffolds was recorded by scanning electron microscopy. Cell proliferation was assessed by DNA quantification and cell differentiation by quantitative real-time reverse transcriptase-polymerized chain reaction analysis (qRT-PCR). Five-millimeter rat calvarial defects (24 defects in 12 rats) were implanted with scaffolds seeded with either low or high density expanded with or without osteogenic supplements. Osteogenic supplements significantly increased cell proliferation (p < 0.001). Scaffolds seeded at high cell density exhibited higher mRNA expressions of Runx2 p=0.001, Col1 p=0.001, BMP2 p<0.001, BSP p<0.001, and OC p=0.013. More bone was formed in response to high cell seeding density (p=0.023) and high seeding density with osteogenic medium (p=0.038). Poly (LLA-co-CL) scaffolds could be appropriate candidates for bone TE. The optimal number of cells to be loaded onto scaffolds is critical for promoting Extracellular matrix synthesis and bone formation. Cell seeding density and osteogenic supplements may have a synergistic effect on the induction of new bone.
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| 4. |
- Yassin, M. A., et al.
(author)
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Surfactant tuning of hydrophilicity of porous degradable copolymer scaffolds promotes cellular proliferation and enhances bone formation
- 2016
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In: Journal of Biomedical Materials Research. Part A. - : John Wiley & Sons. - 1549-3296 .- 1552-4965.
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Journal article (peer-reviewed)abstract
- Poly(l-lactide-co-e(open)-caprolactone) (poly(LLA-co-CL)) has been blended with Tween 80 to tune the material properties and optimize cell-material interactions. Accordingly, the aims of this study were fourfold: to evaluate the effect of low concentrations of Tween 80 on the surface microstructure of 3D poly(LLA-co-CL) porous scaffolds: to determine the effect of different concentrations of Tween 80 on proliferation of bone marrow stromal cells (BMSCs) in vitro under dynamic cell culture at 7 and 21 days; to assess the influence of Tween 80 on the degradation rate of poly(LLA-co-CL) at 7 and 21 days; and in a subcutaneous rat model, to evaluate the effect on bone formation of porous scaffolds modified with 3% Tween 80 at 2 and 8 weeks. Blending 3% (w/w) Tween 80 with poly(LLA-co-CL) improves the surface wettability (p<0.001). Poly(LLA-co-CL)/3% Tween 80 shows significantly increased cellular proliferation at days 7 and 21 (p<0.001). Moreover, the presence of Tween 80 facilitates the degradation of poly(LLA-co-CL). Two weeks post-implantation, the poly(LLA-co-CL)/3% Tween 80 scaffolds exhibit significant mRNA expression of Runx2 (p=0.004). After 8 weeks, poly(LLA-co-CL)/3% Tween 80 scaffolds show significantly increased de novo bone formation, demonstrated by μ-CT (p=0.0133) and confirmed histologically. It can be concluded that blending 3% (w/w) Tween 80 with poly (LLA-co-CL) improves the hydrophilicity and osteogenic potential of the scaffolds.
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| 5. |
- Eltom, Mohamed A., et al.
(author)
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Increasing prevalence of type 2 diabetes mellitus and impact of ethnicity in north Sudan
- 2018
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In: Diabetes Research and Clinical Practice. - : ELSEVIER IRELAND LTD. - 0168-8227 .- 1872-8227. ; 136, s. 93-99
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Journal article (peer-reviewed)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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| 6. |
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| 7. |
- Rashad, Ahmad, et al.
(author)
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Coating 3D Printed Polycaprolactone Scaffolds with Nanocellulose Promotes Growth and Differentiation of Mesenchymal Stem Cells
- 2018
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In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 19:11, s. 4307-4319
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Journal article (peer-reviewed)abstract
- 3D printed polycaprolactone (PCL) has potential as a scaffold for bone tissue engineering, but the hydrophobic surface may hinder optimal cell responses. The surface properties can be improved by coating the scaffold with cellulose nanofibrils material (CNF), a multiscale hydrophilic biocompatible biomaterial derived from wood. In this study, human bone marrow-derived mesenchymal stem cells were cultured on tissue culture plates (TCP) and 3D printed PCL scaffolds coated with CNF. Cellular responses to the surfaces (viability, attachment, proliferation, and osteogenic differentiation) were documented. CNF significantly enhanced the hydrophilic properties of PCL scaffolds and promoted protein adsorption. Live/dead staining and lactate dehydrogenase release assays confirmed that CNF did not inhibit cellular viability. The CNF between the 3D printed PCL strands and pores acted as a hydrophilic barrier, enhancing cell seeding efficiency, and proliferation. CNF supported the formation of a well-organized actin cytoskeleton and cellular production of vinculin protein on the surfaces of TCP and PCL scaffolds. Moreover, CNF-coated surfaces enhanced not only alkaline phosphatase activity, but also collagen Type-I and mineral formation. It is concluded that CNF coating enhances cell attachment, proliferation, and osteogenic differentiation and has the potential to improve the performance of 3D printed PCL scaffolds for bone tissue engineering.
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| 8. |
- Sharma, S., et al.
(author)
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Adenoviral mediated mono delivery of BMP2 is superior to the combined delivery of BMP2 and VEGFA in bone regeneration in a critical-sized rat calvarial bone defect
- 2019
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In: Bone Reports. - : Elsevier. - 2352-1872. ; 10
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Journal article (peer-reviewed)abstract
- Apart from osteogenesis, neovascularization of the defect area is an important determinant for successful bone healing. Accordingly, several studies have employed the combined delivery of VEGFA and BMP2 for bone regeneration. Nevertheless, the outcomes of these studies are highly variable. The aim of our study was to compare the effectiveness of adenoviral mediated delivery of BMP2 alone and in combination with VEGFA in rat bone marrow stromal cells (rBMSC)seeded on a poly(LLA-co-CL)scaffold in angiogenesis and osteogenesis using a critical-sized rat calvarial defect model. Both mono delivery of BMP2 and the combined delivery of a lower ratio of VEGFA and BMP2 (1:4)led to up-regulation of osteogenic genes (Alpl and Runx2)and increased calcium deposition in vitro, compared with the GFP control. Micro computed tomography (microCT)analysis of the rat calvarial defect at 8 weeks showed that the mono delivery of BMP2 (43.37 ± 3.55% defect closure)was the most effective in healing the bone defect, followed by the combined delivery of BMP2 and VEGFA (27.86 ± 2.89%)and other controls. Histological and molecular analyses supported the microCT findings. Analysis of the angiogenesis, however, showed that both mono delivery of BMP2 and combined delivery of BMP2 and VEGFA had similar angiogenic effect in the calvarial defects. Examination of the key genes related to host response against the adenoviral vectors showed that the current model system was not associated with adverse immune response. Overall, the results show that the mono delivery of BMP2 was superior to the combined delivery of BMP2 and VEGFA in healing the critical-sized rat calvarial bone defect. These findings underscore the importance of appropriate growth factor combination for the successful outcome in bone regeneration.
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| 9. |
- Sharma, Sunita, et al.
(author)
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Delivery of VEGFA in bone marrow stromal cells seeded in copolymer scaffold enhances angiogenesis, but is inadequate for osteogenesis as compared with the dual delivery of VEGFA and BMP2 in a subcutaneous mouse model
- 2018
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In: Stem Cell Research & Therapy. - : BioMed Central. - 1757-6512. ; 9
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Journal article (peer-reviewed)abstract
- Background: In bone tissue engineering (BTE), extensive research into vascular endothelial growth factor A (VEGFA)-mediated angiogenesis has yielded inconsistent results. The aim of this study was to investigate the influence on angio-and osteogenesis of adenoviral-mediated delivery of VEGFA alone or in combination with bone morphogenetic protein 2 (BMP2) in bone marrow stromal cells (BMSC) seeded onto a recently developed poly(LLA-co-CL) scaffold. Methods: Human BMSC were engineered to express VEGFA alone or in combination with BMP2 and seeded onto poly(LLA-co-CL) scaffolds. Changes in angiogenic and osteogenic gene and protein levels were examined by quantitative reverse-transcription polymerase chain reaction (RT-PCR), PCR array, and alkaline phosphatase assay. An in vivo subcutaneous mouse model was used to investigate the effect on angio-and osteogenesis of VEGFA alone or in combination with BMP2, using microcomputed tomography (mu CT), histology, immunohistochemistry, and immunofluorescence. Results: Combined delivery of a lower ratio (1: 3) of VEGFA and BMP2 (ad-BMP2 + VEGFA) led to upregulation of osteogenic and angiogenic genes in vitro at 3 and 14 days, compared with mono-delivery of VEGFA (ad-VEGFA) and other controls. In vivo, in a subcutaneous mouse model, both ad-VEGFA and ad-BMP2 + VEGFA scaffold explants exhibited increased angiogenesis at 2 weeks. Enhanced angiogenesis was largely related to the recruitment and differentiation of mouse progenitor cells to the endothelial lineage and, to a lesser extent, to endothelial differentiation of the implanted BMSC. mu CT and histological analyses revealed enhanced de novo bone formation only in the ad-BMP2 + VEGFA group, corresponding at the molecular level to the upregulation of genes related to osteogenesis, such as ALPL, RUNX2, and SPP1. Conclusions: Although BMSC expressing VEGFA alone or in combination with BMP2 significantly induced angiogenesis, VEGFA alone failed to demonstrate osteogenic activity both in vitro and in vivo. These results not only call into question the use of VEGFA alone in bone regeneration, but also highlight the importance in BTE of appropriately formulated combined delivery of VEGFA and BMP2.
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| 10. |
- Tan, B. K., et al.
(author)
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Investigation of the performance of an SIS mixer with Nb-AlN-NBN tunnel junctions in the 780-950 GHz frequency band
- 2018
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In: 2018 29th IEEE International Symposium on Space Terahertz Technology, ISSTT 2018. ; , s. 139-142
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Conference paper (peer-reviewed)abstract
- In this paper, we present preliminary measured performance of an SIS mixer employing a Nb/AIN/NbN tunnel junction in the frequency range of 780-950 GHz range. The mixer design is an upgrade of the Carbon Heterodyne Array of the Max-Planck-Institute Plus (CHAMP+) mixer, coupled with an easy to fabricate smooth-walled horn. The noise temperature of the mixer is measured using the standard Y-factor method, but all the RF optics is enclosed in the cryostat. We use a rotating mirror in the cryostat to switch between a room temperature load and a 4 K blackbody load. With this method, we have measured a noise temperature of 330 K around 850 GHz, corrected for a mismatch between a reduced height rectangular waveguide at the input of the mixer block and a full height waveguide at the output of the horn. To remove this mismatch we now plan to redesign a new mixer chip with a full-height waveguide back-piece. The expected performance of the new mixer chip is also reported.
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