| 1. |
- Dziewanowska, Julia, et al.
(author)
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Nanocrystallization as a tool for controlling in vitro dissolution of borophosphate glass
- 2023
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In: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 49:16, s. 27382-27390
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Journal article (peer-reviewed)abstract
- The controlled nanocrystallization of sodium-calcium-borophosphate glass (Na16.6Ca5.1B10.5Al0.8P10.5 O56.5 in at %) was conducted to investigate its influence on in vitro dissolution. Three temperatures (570 degrees C, 590 degrees C, and 610 degrees C) were selected based on thermal analysis and investigation of the morphology, structure, and in vitro dissolution of glass and glass-ceramics was conducted. The results of X-ray diffraction confirmed the presence of calcium phosphates nanocrystallites in glass-ceramics, with their contents increasing proportionally to the crystallization temperature. Infrared spectroscopy showed the presence of phosphate and borate network units, along with phosphates in a crystalline form. It was found that the target glass shows the highest mass loss in comparison to the glass-ceramics. Controlled nanocrystallization slowed down the dissolution of the materials (>10%), but did not adversely affect the deposition of hydroxyapatite layer. The presence of calcium phosphate nanocrystallites favors the process of B3+ release. The nanocrystallization of borophosphate glasses is a perspective tool for controlling the rate of dissolution of bioactive materials and enhancing their ability to de-posit hydroxyapatite on their surface.
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| 2. |
- Ignaczak, Justyna, et al.
(author)
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Fe-modified Mn2CuO4 spinel oxides: coatings based on abundant elements for solid oxide cell interconnects
- 2023
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In: International Journal of Hydrogen Energy. - 0360-3199. ; 48:92, s. 36076-36093
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Journal article (peer-reviewed)abstract
- The current state of the art steel interconnect coating materials are based on critical raw material - Co-oxide spinels. Replacing Co-oxide spinels with alternative, abundant materials can reduce the dependence on the critical raw materials. Cobalt-free coatings with the general formula Mn2-xCuFexO4, where x = 0, 0.1, 0.3, were electrophoretically deposited on a ferritic stainless-steel support and evaluated. Prior to deposition, the powders were prepared by a soft chemistry process and studied in terms of crystallographic phase analysis, electrical conductivity, thermal expansion, and sinterability behaviour. Coated steel samples were oxidised in an air atmosphere at 750 °C for 3000 h. In parallel, a state-of-the-art MnCo2O4 spinel oxide was tested as a reference. The coatings and oxide scale microstructures of the surfaces and cross-sections were examined by XRD, and SEM-EDX. TEM-EDX, XRF, and micro-XRD were also performed on the cross-section lamellae. The electrical properties of the steel-coating system were evaluated by Area Specific Resistance measurement. The results confirm that Mn–Cu–Fe oxides exhibit higher conductivity and lower TEC than Mn–Co oxide. Based on the obtained results, it might be concluded that the proposed coatings are a promising alternative to coatings that contain cobalt.
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| 3. |
- Mahlapuu, Margit, et al.
(author)
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Evaluation of LL-37 in healing of hard-to-heal venous leg ulcers : A multicentric prospective randomized placebo-controlled clinical trial
- 2021
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In: Wound Repair and Regeneration. - : Wiley. - 1067-1927 .- 1524-475X. ; 29:6, s. 938-950
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Journal article (peer-reviewed)abstract
- Many patients with venous leg ulcers do not reach complete healing with compression treatment alone, which is current standard care. This clinical trial HEAL LL-37 was a phase IIb double-blind, randomized, placebo-controlled study, with the aim to evaluate the efficacy and safety of a new drug LL-37 for topical administration, in combination with compression therapy, in 148 patients suffering from hard-to-heal venous leg ulcers. The study had three arms, consisting of two groups treated with LL-37 at concentrations of 0.5 or 1.6 mg/mL, and a placebo cohort. Patients had a mean age of 67.6 years, a median ulcer duration of 20.3 months, and a mean wound size at the time of randomization of 11.6 cm(2). Efficacy analysis performed on the full study population did not identify any significant improvement in healing in patients treated with LL-37 as compared with the placebo. In contrast, a post hoc analysis revealed statistically significant improvement with LL-37 treatment in several interrelated healing parameters in the subgroup of patients with large target wounds (a wound area of at least 10 cm(2) at randomization), which is a known negative prognostic factor for healing. The study drug was well tolerated and safe in both dose strengths. In summary, this clinical trial did not detect any significant differences in healing of venous lower leg ulcers in the entire study cohort comparing patients treated with LL-37 versus placebo. A subgroup analysis provided an interesting observation that LL-37 could offer a treatment benefit in patients with large ulcers, exigently warranting a further study adequately powered to statistically assess the treatment outcome in this patient group.
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| 4. |
- Wójcik, Natalia A., et al.
(author)
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DC and AC Conductivity, Biosolubility and Thermal Properties of Mg-Doped Na2O-CaO-P2O5 Glasses
- 2021
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In: Materials. - : MDPI. - 1996-1944. ; 14:10
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Journal article (peer-reviewed)abstract
- Bioactive glasses have recently been extensively used to replace, regenerate, and repair hard tissues in the human body because of their ability to bond with living tissue. In this work, the effects of replacing Na2O with MgO on the electrical, biosolubility, and thermal properties of the target glass 10Na2O-60P2O5-30CaO (in mol%) were investigated. The electrical properties of the glasses were studied with the impedance spectroscopy technique. At 473 K, DC conductivity values decreased from 4.21 x 10-11 to 4.21 x 10-12 S cm-1 after complete substitution of MgO for Na2O. All samples had a similar activation energy of the DC conduction process similar to 1.27 eV. Conduction mechanisms were found to be due to hop of ions: Na+, Mg2+ and probable H+. FTIR analysis showed that, as the Mg content increased, the Q2 unit (PO2-) shifted towards higher wavenumbers. The proportion of Q3 unit (P2O5) decreased in the glass structure. This confirmed that the replacement of Na+ by Mg2+ was accompanied by concurrent polymerization of the calcium-phosphate glass network. The biosolubility test in the phosphate-buffered saline solution showed that the magnesium addition enhanced the biosolubility properties of Na2O-CaO-P2O5 glasses by increasing their dissolution rate and supporting forming CaP-rich layers on the surface. The glass transition temperature increased, and thermal stability decreased substantially upon substitution of Na2O by MgO.
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| 5. |
- Wojcik, Natalia Anna, et al.
(author)
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Effect of crystallinity on structural, thermal, and in vitro dissolution properties of Na2O-CaO-Nb2O5/MgO-P2O5 glass-ceramics
- 2023
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In: Journal of the European Ceramic Society. - : Elsevier. - 0955-2219 .- 1873-619X. ; 43:5, s. 2234-2244
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Journal article (peer-reviewed)abstract
- The impact of the crystallinity on structural, thermal, and in vitro dissolution properties were examined for Na2O-CaO-Nb2O5/MgO-P2O5 glasses/glass-ceramics. Glass-ceramics were synthesized via a spontaneous crystallization process. The Nb content in the materials increased with melting temperature, furthermore, the crystallinity is proportional to the Nb content. The presence of crystalline niobates and phosphates is confirmed by FTIR analysis which is consistent with XRD. The FTIR results indicate that the phosphate network is built of different proportions of Q2, Q1, and Q0 units, depending on the amount and type of crystalline phase. Most of the samples show an improvement in thermal stability. The in vitro dissolution test showed that the highest mass loss for most of the samples occurred during the first 6 days of immersion in the PBS solution. The presence of small phosphate crystals favors the deposition of hydroxyapatite on samples' surfaces while the larger niobate crystals dissolve more readily.
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| 6. |
- Wójcik, Natalia A., et al.
(author)
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Effect of Nb and Al on in vitro dissolution behavior and structure of Na2O-MgO CaO-P2O5 glasses
- 2022
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In: Journal of Non-Crystalline Solids. - : Elsevier. - 0022-3093 .- 1873-4812. ; 585
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Journal article (peer-reviewed)abstract
- In vitro dissolution, structure, and thermal properties of the glass series Na2O-MgO CaO Nb2O5 -Al2O3-P2O5 were studied. The dissolution behavior in phosphate-buffered saline (PBS) confirmed the potential bioactive properties of tested glasses. The dissolution process was found to depend on the Al, Nb, and Mg contents. Al, respectively, suppresses the Nb and accelerates the Mg release process from the glasses. Moreover, Al stays highly bonded in the phosphate network during 14 days of immersion. In all glasses, the phosphate network was found to be highly disrupted and built mostly of Q1 units. Al and Mg addition decreases the polymerization of the glass network. The Nb addition effect was found to be the opposite. Thermal properties were correlated mostly with the Nb and Al contents. However, the fragility index of glasses increases with the content of P and Al.
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| 7. |
- Wójcik, Natalia A., et al.
(author)
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The effect of nitrogen on the structure and thermal properties of beryllium-containing Na-(Li)-Si-O-N glasses
- 2019
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In: Journal of Non-Crystalline Solids. - : Elsevier. - 0022-3093 .- 1873-4812. ; 522, s. 1-8
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Journal article (peer-reviewed)abstract
- Two oxynitride glass series with the composition of 35Na2O-5BeO-(60-x)SiO2-xSi3N4 and 9Li2O- 27Na2O-5BeO-(59-x)SiO2-xSi3N4, were prepared. The glasses' topography and structure were studied by Scanning Electron Microscopy and Raman spectroscopy. The composition was analyzed by Inductively Coupled Plasma Optical Emission Spectrometer, SEM-EDS and nitrogen and oxygen elemental analyzer. Na-(Li)-Be-silicate glasses were found to contain up to approximately 3.4 (or 5.2 for EDS measurements) at.% of N, respectively. The samples were homogenous in their topography and compositions of their cross-sections.The presence of three-fold coordinated nitrogen atoms in Na-Be-Si-O-N glasses results in higher degree of polymerization as was observed by Raman spectroscopy. The spectrum of analogous glasses with lithium did not show a significant decrease in Q2 units but exhibit the presence of Q4 units which also indicates a polymerization of the network. The incorporation of nitrogen in these glasses leads to the increase of the glass transition temperature and thermal stability.
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