Agnieszka Witecka, Ph.D., Eng.

Department of Mechanics of Materials (ZMM)
Division of Advanced Composite Materials (PZMK)
position: assistant
telephone: (+48) 22 826 12 81 ext.: 418
room: 142
e-mail: awitecka

Doctoral thesis
2016-12-09Improvement of biocompatibility of magnesium alloys AZ91 and ZM21 by surface modification  (PW)
supervisor -- Wojciech Święszkowski, Ph.D., Dr. Habil., Eng., PW
supervisor -- Prof. Dr. Akiko Yamamoto, NIMS
1329 
Recent publications
1.Rydzek G., Pakdel A., Witecka A., Shri D.N.A., Gaudière F., Nicolosi V., Mokarian-Tabari P., Schaaf P., Boulmedais F., Ariga K., pH-Responsive Saloplastics Based on Weak Polyelectrolytes: From Molecular Processes to Material Scale Properties, Macromolecules, ISSN: 0024-9297, DOI: 10.1021/acs.macromol.8b00609, Vol.51, No.12, pp.4424-4434, 2018
Abstract:

Compact polyelectrolyte complexes (COPECs), also named saloplastics, represent a new class of material with high fracture strain and self-healing properties. Here, COPECs based on poly(methacrylic acid) (PMAA) and poly(allylamine hydrochloride) (PAH) were prepared by centrifugation at pH 7. The influence of postassembly pH changes was monitored chemically by ATR-FTIR, ICP, DSC, and TGA, morphologically by SEM, and mechanically by strain to break measurements. Postassembly pH stimuli misbalanced the charge ratio in COPECs, impacting their concentration in counterions, cross-link density, and polymer chain mobility. At the material level, changes were observed in the porosity, composition, water content, and mechanical properties of COPECs. The cross-link density was a prominent factor governing the saloplastic’s composition and water content. However, the porosity and mechanical properties were driven by several factors including salt-induced plasticization and conformational changes of polyelectrolytes. This work illustrates how multiple-scale consequences arise from a single change in the environment of COPECs, providing insights for future design of stimuli-responsive materials.

Affiliations:
Rydzek G.-National Institute for Materials Science (JP)
Pakdel A.-World Premier International Center for Materials Nanoarchitectonics (MANA) (JP)
Witecka A.-IPPT PAN
Shri D.N.A.-Universiti Malaysia Pahang (MY)
Gaudière F.-Université de Strasbourg (FR)
Nicolosi V.-Trinity College (IE)
Mokarian-Tabari P.-Trinity College (IE)
Schaaf P.-Institut National de la Santé et de la Recherche Médicale (FR)
Boulmedais F.-Université de Strasbourg (FR)
Ariga K.-National Institute for Materials Science (JP)
2.Pakdel A., Witecka A., Rydzek G., Shri D.N.A., Nicolosi V., A comprehensive analysis of extrusion behavior, microstructural evolution, and mechanical properties of 6063 Al–B4C composites produced by semisolid stir casting, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, ISSN: 0921-5093, DOI: 10.1016/j.msea.2018.02.080, Vol.721, pp.28-37, 2018
Abstract:

In this study, composites of aluminum alloy 6063 reinforced with 10 wt% boron carbide microparticles were successfully fabricated by a combination of spark plasma sintering and stir casting methods, followed by hot extrusion. A systematic study on the relationship between extrusion process variables (i.e. extrusion ratio, temperature, and punch speed) and porosity, particle refinement, particle distribution and consequently tensile properties and fracture behavior of the composites was performed. Extensive electron microscopy analysis and tensile testing of the composites revealed a multifactoral interdependency of microstructural evolution and mechanical properties on the extrusion process variables. For example, while increasing the extrusion ratio at higher temperatures led to moderate particle refinement, better densification of the composites, and improvement in mechanical properties, concurrent particle fragmentation and microvoid formation around the particles at lower temperatures had opposing effects on the mechanical behavior. We show that the dependency of mechanical properties on all such microstructural factors makes it difficult to predict optimum extrusion conditions in aluminum matrix composites. That is, unlike the common approach, extruding the composites at higher temperatures and achieving more reduction in area may not necessarily lead to the most favorable mechanical properties.

Keywords:

Aluminum matrix composite, Hot extrusion, Mechanical behavior, Microstructure, Spark plasma sintering, Stir casting

Affiliations:
Pakdel A.-World Premier International Center for Materials Nanoarchitectonics (MANA) (JP)
Witecka A.-IPPT PAN
Rydzek G.-National Institute for Materials Science (JP)
Shri D.N.A.-Universiti Malaysia Pahang (MY)
Nicolosi V.-Trinity College (IE)
3.Witecka A., Yamamoto A., Święszkowski W., Influence of SaOS-2 cells on corrosion behavior of cast Mg-2.0Zn0.98Mn magnesium alloy, COLLOIDS AND SURFACES B-BIOINTERFACES, ISSN: 0927-7765, DOI: 10.1016/j.colsurfb.2016.10.041, Vol.150, pp.288-296, 2017
Abstract:

In this research, the effect of the presence of living cells (SaOS-2) on in vitro degradation of Mg-2.0Zn-0.98Mn (ZM21) magnesium alloy was examined by two methods simple immersion/cell culture tests and electrochemical measurements (electrochemical impedance spectroscopy and potentiodynamic polarization) under cell culture conditions. In immersion/cell culture tests, when SaOS-2 cells were cultured on ZM21 samples, pH of cell culture medium decreased, therefore weight loss and Mg2+ ion release from the samples increased. Electrochemical measurements revealed the presence of living cells increased corrosion rate (Icorr) and decreased polarization resistance (Rp) after 48 h of incubation. This acceleration of ZM21 corrosion can mainly be attributed to the decrease of medium pH due to cellular metabolic activities.

Keywords:

Biodegradable metals, Biomaterials, Electrochemical impedance spectroscopy, Immersion, Cell culture condition

Affiliations:
Witecka A.-other affiliation
Yamamoto A.-National Institute for Materials Science (JP)
Święszkowski W.-other affiliation
4.Pakdel A., Witecka A., Rydzek G., Shri D.N.A., A comprehensive microstructural analysis of Al–WC micro- and nano-composites prepared by spark plasma sintering, MATERIALS AND DESIGN, ISSN: 0261-3069, DOI: 10.1016/j.matdes.2017.01.064, Vol.119, pp.225-234, 2017
Abstract:

There have been many investigations on metal matrix microcomposites produced by conventional casting routes; however, in the past decade, the focus has shifted more toward nanocomposites produced via solid state routes. To have a realistic view of performance prediction and optimum design of such composites, in this work Al matrix composites (AMCs) reinforced with WC microparticles, nanoparticles, and bimodal micro-/nano-particles were prepared by spark plasma sintering. The effects of particle size and concentration, and process variables (i.e. sintering temperature, duration, and pressure) on the evolution of microstructure, density and hardness of the composites were studied comprehensively. Full densification of AMCs with high particle concentration was problematic because of ceramic cluster formations in the microstructure. This effect was more emphasized in AMCs containing nanoparticles. AMCs with microparticles were more easily densified, but their hardness benefits were inferior. On the other hand, the mixture of micro- and nano-particles in Al-WC bimodal composites led to better matrix reinforcement integrity and an overall improvement in the microstructural properties. Finally, increasing the sintering temperature improved the microstructural features and hardness of the composites (more enhanced in high wt.% samples), but sintering duration and pressure did not have a big impact on the composite properties.

Keywords:

Composite, Nanoparticle, Microparticle, Powder metallurgy, SPS, Microstructure

Affiliations:
Pakdel A.-World Premier International Center for Materials Nanoarchitectonics (MANA) (JP)
Witecka A.-IPPT PAN
Rydzek G.-National Institute for Materials Science (JP)
Shri D.N.A.-Universiti Malaysia Pahang (MY)
5.Witecka A., Yamamoto A., Idaszek J., Chlanda A., Święszkowski W., Influence of biodegradable polymer coatings on corrosion, cytocompatibility and cell functionality of Mg-2.0Zn-0.98Mn magnesium alloy, COLLOIDS AND SURFACES B-BIOINTERFACES, ISSN: 0927-7765, DOI: 10.1016/j.colsurfb.2016.04.021, Vol.144, pp.284-292, 2016
Abstract:

Four kinds of biodegradable polymers were employed to prepare bioresorbable coatings on Mg-2.0Zn-0.98Mn (ZM21) alloy to understand the relationship between polymer characteristics, protective effects on substrate corrosion, cytocompatibility and cell functionality. Poly-l-lactide (PLLA), poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) or poly(lactic-co-glycolic) acid (PLGA) was spin-coated on ZM21, obtaining a smooth, non-porous coating less than 0.5 μm in thickness. Polymer coating characterization, a degradation study, and biocompatibility evaluations were performed. After 4 w of immersion into cell culture medium, degradation of PLGA and PLLA coatings were confirmed by ATR-FTIR observation. The coatings of PLLA, PHB and PHBV, which have lower water permeability and slower degradation than PLGA, provide better suppression of initial ZM21 degradation and faster promotion of human osteosarcoma cell growth and differentiation.

Keywords:

Biodegradable metal, Magnesium alloy, Biodegradable polymer, SaOS-2 differentiation, Calcification

Affiliations:
Witecka A.-other affiliation
Yamamoto A.-National Institute for Materials Science (JP)
Idaszek J.-other affiliation
Chlanda A.-Warsaw University of Technology (PL)
Święszkowski W.-other affiliation
6.Witecka A., Bogucka A., Yamamoto A., Máthis K., Krajňák T., Jaroszewicz J., Święszkowski W., In vitro degradation of ZM21 magnesium alloy in simulated body fluids, Materials Science and Engineering C-Materials for Biological Applications, ISSN: 0928-4931, DOI: 10.1016/j.msec.2016.04.019, Vol.65, pp.59-69, 2016
Abstract:

In vitro degradation behavior of squeeze cast (CAST) and equal channel angular pressed (ECAP) ZM21 magnesium alloy (2.0 wt% Zn-0.98 wt% Mn) was studied using immersion tests up to 4 w in three different biological environments. Hanks' Balanced Salt Solution (Hanks), Earle's Balanced Salt Solution (Earle) and Eagle minimum essential medium supplemented with 10% (v/v) fetal bovine serum (E-MEM + 10% FBS) were used to investigate the effect of carbonate buffer system, organic compounds and material processing on the degradation behavior of the ZM21 alloy samples. Corrosion rate of the samples was evaluated by their Mg2 + ion release, weight loss and volume loss. In the first 24 h, the corrosion rate sequence of the CAST samples was as following: Hanks > E-MEM + 10% FBS > Earle. However, in longer immersion periods, the corrosion rate sequence was Earle > E-MEM + 10% FBS ≥ Hanks. Strong buffering effect provided by carbonate buffer system helped to maintain the pH avoiding drastic increase of the corrosion rate of ZM21 in the initial stage of immersion. Organic compounds also contributed to maintain the pH of the fluid. Moreover, they adsorbed on the sample surface and formed an additional barrier on the insoluble salt layer, which was effective to retard the corrosion of CAST samples. In case of ECAP, however, this effect was overcome by the occurrence of strong localized corrosion due to the lower pH of the medium. Corrosion of ECAP samples was much greater than that of CAST, especially in Hanks, due to higher sensitivity of ECAP to localized corrosion and the presence of Cl−.

The present work demonstrates the importance of using an appropriate solution for a reliable estimation of the degradation rate of Mg-base degradable implants in biological environments, and concludes that the most appropriate solution for this purpose is E-MEM + 10% FBS, which has the closest chemical composition to human blood plasma.

Keywords:

ZM21 magnesium alloy, ECAP, Simulated body fluids, In vitro degradationBicomponent nanofibers, Biodegradation, Biopolymer

Affiliations:
Witecka A.-other affiliation
Bogucka A.-Warsaw University of Technology (PL)
Yamamoto A.-National Institute for Materials Science (JP)
Máthis K.-Charles University in Prague (CZ)
Krajňák T.-Charles University in Prague (CZ)
Jaroszewicz J.-other affiliation
Święszkowski W.-other affiliation
7.Witecka A., Yamamoto A., Święszkowski W., Influence of SaOS-2 cells on corrosion behaviour of cast ZM21 magnesium alloy, European Cells and Materials, ISSN: 1473-2262, Vol.28, No.Suppl. 3, pp.71, 2014

Conference papers
1.Witecka A., Yamamoto A., Święszkowski W., Improvement of cytocompatibility of magnesium alloy zm21 by surface modification, TMS 2014, The Magnesium Technology Symposium, 2014-02-16/02-20, San Diego (US), DOI: 10.1002/9781118888179.ch71, pp.375-380, 2014
Abstract:

Application of a biodegradable polymer coating is one of the methods to improve the initial corrosion resistance and cytocompatibility of magnesium (Mg) alloys. However, bulging of the coating film during long term immersion has been reported. Therefore, improvement of interface strength between the coating and the substrate surface is a key for the success of this method. Combination of surface modification [silanization with 3- (glycidyloxypropyl) triethoxysilane (GPTES)] and biodegradable polymer coating [poly-L-lactide (PLLA)] were applied to a Mg- 2.0Zn-0.98Mn (ZM21) cast alloy. Results of a cell proliferation assay show that PLLA and GPTES+PLLA coating successfully improved cell growth during 7 days of incubation and suppressed Mg2+ release after 4 days of incubation. The silanization process had no impact on suppression of corrosion. Calcification was observed on all samples after 1 week of incubation with calcification medium, but the calcified area was much larger on the GPTES+PLLA coated sample than on the uncoated sample.

Keywords:

biodegradable metal, ZM21, cytocompatibility, silane-coupling, PLLA

Affiliations:
Witecka A.-other affiliation
Yamamoto A.-National Institute for Materials Science (JP)
Święszkowski W.-IPPT PAN

Conference abstracts
1.Witecka A., Yamamoto A., Święszkowski W., Basista M., Influence of polymer film concentration on cytocompatibility and corrosion suppression of ZM21 magnesium alloy, 7th KMM-VIN Industrial Workshop “Biomaterials: Key Technologies for Better Healthcare”, 2017-09-27/09-28, Erlangen (DE), pp.1-1, 2017