Judyta Dulnik, M.Sc., Eng.

Laboratory of Polymers and Biomaterials (SPPiB)
position: specialist
telephone: (+48) 22 826 12 81 ext.: 211
room: 343
e-mail: jdulnik

Recent publications
1.Dulnik J., Denis P., Sajkiewicz P., Kołbuk D., Choińska E., Biodegradation of bicomponent PCL/gelatin and PCL/collagen nanofibers electrospun from alternative solvent system, Polymer Degradation and Stability, ISSN: 0141-3910, DOI: 10.1016/j.polymdegradstab.2016.05.022, Vol.130, pp.10-21, 2016
Dulnik J., Denis P., Sajkiewicz P., Kołbuk D., Choińska E., Biodegradation of bicomponent PCL/gelatin and PCL/collagen nanofibers electrospun from alternative solvent system, Polymer Degradation and Stability, ISSN: 0141-3910, DOI: 10.1016/j.polymdegradstab.2016.05.022, Vol.130, pp.10-21, 2016

Abstract:
Bicomponent polycaprolactone/gelatin and polycaprolactone/collagen nanofibers formed by electrospinning using various solvents were subjected to biodegradation and compared. Hexafluoroisopropanol (HFIP) was used as a reference solvent, while the second, alternative solvent system was the mixture of acetic acid (AA) with formic acid (FA). Biodegradation of investigated materials was manifested mainly by the gelatin leaching, including collagen which is indeed denaturated to gelatin during electrospinning, leading to nanofibers erosion. There was no molecular degradation of PCL during 90 days of biodegradation procedure as deduced from no change in the elongation stress at break. The rate of biopolymer leaching was very fast from all materials during the first 24 h of biodegradation, being related to surface leaching, followed by a slower rate leaching from deeper material layers. Mass measurements showed much faster biopolymer leaching from nanofibers electrospun from AA/FA than from HFIP because of strongly emulsive nature of the solution in the former case. Irrespective of the solvent used, the leaching rate increased with initial content of gelatin. The analysis of Young modulus during biodegradation indicated complex mechanism of changes, including biopolymer mass loss, increase of PCL crystallinity and partial gelatin renaturation.

Keywords:
Bicomponent nanofibers, Biodegradation, Biopolymer

2.Jarząbek D.M., Chmielewski M., Dulnik J., Strojny-Nędza A., The Influence of the Particle Size on the Adhesion Between Ceramic Particles and Metal Matrix in MMC Composites, Journal of Materials Engineering and Performance, ISSN: 1059-9495, DOI: 10.1007/s11665-016-2107-3, Vol.25, No.8, pp.3139-3145, 2016
Jarząbek D.M., Chmielewski M., Dulnik J., Strojny-Nędza A., The Influence of the Particle Size on the Adhesion Between Ceramic Particles and Metal Matrix in MMC Composites, Journal of Materials Engineering and Performance, ISSN: 1059-9495, DOI: 10.1007/s11665-016-2107-3, Vol.25, No.8, pp.3139-3145, 2016

Abstract:
This study investigated the influence of the particle size on the adhesion force between ceramic particles and metal matrix in ceramic-reinforced metal matrix composites. The Cu-Al2O3 composites with 5 vol.% of ceramic phase were prepared by a powder metallurgy process. Alumina oxide powder as an electrocorundum (Al2O3) powder with different particle sizes, i.e., fine powder <3 µm and coarse powder of 180 µm was used as a reinforcement. Microstructural investigations included analyses using scanning electron microscopy with an integrated EDS microanalysis system and transmission microscopy. In order to measure the adhesion force (interface strength), we prepared the microwires made of the investigated materials and carried out the experiments with the use of the self-made tensile tester. We have observed that the interface strength is higher for the sample with coarse particles and is equal to 74 ± 4 MPa and it is equal to 68 ± 3 MPa for the sample with fine ceramic particles.

Keywords:
adhesion, interface strength, metal matrix composites, nanocomposites, tensile test

3.Denis P., Dulnik J., Sajkiewicz P., Electrospinning and Structure of Bicomponent Polycaprolactone/Gelatin Nanofibers Obtained Using Alternative Solvent System, International Journal of Polymeric Materials and Polymeric Biomaterials, ISSN: 0091-4037, DOI: 10.1080/00914037.2014.945208, Vol.64, No.7, pp.354-364, 2015
Denis P., Dulnik J., Sajkiewicz P., Electrospinning and Structure of Bicomponent Polycaprolactone/Gelatin Nanofibers Obtained Using Alternative Solvent System, International Journal of Polymeric Materials and Polymeric Biomaterials, ISSN: 0091-4037, DOI: 10.1080/00914037.2014.945208, Vol.64, No.7, pp.354-364, 2015

Abstract:
Bicomponent polycaprolactone/gelatin (PCL/Gt) nanofibers were successfully formed for the first time by electrospinning using a novel polymer–solvent system with solvents being alternative to the commonly used toxic solvents like fluorinated alcohols. The mixture of acetic acid (AA) with formic acid (FA; 90:10) was applied. Stable electrospinning was possible despite the fact the mixture of PCL and gelatin in AA/FA solvent showed emulsive structure. From the practical perspective, there is no doubt that it is possible to obtain PCL/Gt fibers using AA/FA mixture with morphology similar to that for fibers spun from hexafluoroisopropanol (HFIP) solutions.

Keywords:
Alternative solvents, electrospinning, gelatin, nanofibers, polycaprolactone, structure


Conference papers
1.Chwojnowski A., Kruk A., Wojciechowski C., Łukowska E., Dulnik J., Sajkiewicz P., The dependence of the membrane structure on the non-woven forming the macropores in the 3D scaffolds preparation, Desalination and Water Treatment, ISSN: 1944-3994, DOI: 10.5004/dwt.2017.11394, Vol.64, pp.324-331, 2017
Chwojnowski A., Kruk A., Wojciechowski C., Łukowska E., Dulnik J., Sajkiewicz P., The dependence of the membrane structure on the non-woven forming the macropores in the 3D scaffolds preparation, Desalination and Water Treatment, ISSN: 1944-3994, DOI: 10.5004/dwt.2017.11394, Vol.64, pp.324-331, 2017

Abstract:
Three types of membrane structures with wide pores were compared in this study. One of the membranes was obtained from polyethersulfone using cellulose fibers as the macropore precursors. Two of the fibers were obtained from poly(L-lactide). As the macropore precursors olyvinylpyrrolidone (1.2 MDa) and pork gelatin non-woven were used, the influence of non-woven fibers on the structure of membranes was shown. Necessity of specific membrane structure application was explained. The hoice of polymers and co-polymers with a range of biodegradation times can determine the scaffold type suitable for the age of a patient.

Keywords:
Polysulfone membrane, Polyester membranes, Membrane structures, Biodegradable membranes, 3D scaffold

2.Kruka A., Gadomska-Gajadhur A., Ruśkowski P., Chwojnowski A., Dulnik J., Synoradzki L., Preparation of biodegradable semi-permeable membranes as 3D scaffolds for cell cultures, Desalination and Water Treatment, ISSN: 1944-3994, DOI: 10.5004/dwt.2017.11415, Vol.64, pp.317-323, 2017
Kruka A., Gadomska-Gajadhur A., Ruśkowski P., Chwojnowski A., Dulnik J., Synoradzki L., Preparation of biodegradable semi-permeable membranes as 3D scaffolds for cell cultures, Desalination and Water Treatment, ISSN: 1944-3994, DOI: 10.5004/dwt.2017.11415, Vol.64, pp.317-323, 2017

Abstract:
Results of the preparation of semi-permeable membranes made of biodegradable polymers membranes were presented. Among known polyesters, polylactide was selected for research. The membranes were obtained using wet phase inversion method. The influence of polyvinylpyrrolidone and polymeric nano-non-wovens as pores precursors on the structure of obtained membranes was analysed. It was shown, that utilisation of polymeric nano-non-wovens enabled preparation of semi-permeable membranes, which could be used as wide-pore 3D-type cellular scaffolds.

Keywords:
Biodegradable polymers membranes, Biodegradable polyesters, Porous three-dimensional scaffolds, Inversion phase method


Conference abstracts
1.Dulnik J., Kołbuk D., Denis P., Sajkiewicz P., Cellular studies of electrospun PCL/biocomponent nanofibers from alternative and traditional solvents, TERMIS European Chapter Meetin, European Chapter Meeting of the Tissue Engineering and Regenerative Medicine International Society 2017, 2017-06-26/06-30, Davos (CH), pp.582, 2017
2.Dulnik J., Denis P., Sajkiewicz P., Kołbuk D., Bicomponent PCL/Biopolymer nanofibers electrospun from various solvents - cellular and biodegradation studies, ELECTROSPIN 2016, 4th International Conference on Electrospinning, 2016-06-28/07-01, Otranto (IT), pp.1, 2016
Dulnik J., Denis P., Sajkiewicz P., Kołbuk D., Bicomponent PCL/Biopolymer nanofibers electrospun from various solvents - cellular and biodegradation studies, ELECTROSPIN 2016, 4th International Conference on Electrospinning, 2016-06-28/07-01, Otranto (IT), pp.1, 2016

Abstract:
Electrospun nonwovens from PCL/gelatin and PCL/collagen structurally mimic native extracellular matrix and provide cells with chemical cues affecting them. Electrospinning of bicomponent nanofibres requires the use of a solvent which dissolves both of the polymers.
We have optimized the process of electrospinning of PCL/gelatin and PCL/collagen nanofibers based on the use of non-toxic, alternative solvents: acetic acid and formic acid (AA/FA) as previously described [1].
Bicomponent PCL/gelatin and PCL/collagen nanofibers were formed by electrospinning using the mixture of acetic acid and formic acid (9:1 w/w ratio), while hexafluoroisopropanol (HFIP) was used as a reference solvent. Nonwoven materials were subjected to cellular in vitro and biodegradation tests and compared.
All in vitro tests were performed using L929 mouse fibroblast cells. Cytotoxicity test was carried out on extracts and showed that all type of materials are not cytotoxic. Materials with 10% biopolymer content as well as made from PCL only underwent experiment in direct contact. Cells were cultured on materials for 3, 5 and 7 days and afterwards taken for SEM as well as fluorescent dying of nuclei and cytoskeleton. Obtained results proved that the addition of Arg-Gly-Asp (RGD) amino acid sequences from biopolymer, in comparison to pure PCL materials, facilitates cell adhesion and spreading on the surface of nonwovens regardless of solvent used in electrospinning.
PCL/gelatin and PCL/collagen nonwovens underwent biodegradation in PBS solution at 37°C. After different times, ranging from 1 to 90 days samples were subjected for comparative analysis via various methods.
Despite the fact that bicomponent nanofibers electrospun from alternative solvents have similar morphology to those electrospun from perfluorinated alcohols, they differ in the internal structure which seriously affects biodegradation process. Biodegradation of investigated materials is manifested mainly by the gelatin leaching, which leads to nanofibers erosion, particularly large for nanofibers spun from AA/FA.

Keywords:
electrospinning, bicomponent nanofibers, biodegradation, cellular studies

3.Chwojnowski A., Kruk A., Wojciechowski C., Łukowska E., Dulnik J., Sajkiewicz P., The dependence of the membrane structure on the non-woven forming the macropores in the 3D scaffolds preparation, MEMPEP 2016, XI-th Conference on Membranes and Membrane Processes in Environmental Protection, 2016-06-15/06-18, Zakopane (PL), pp.23, 2016
4.Dulnik J., Denis P., Sajkiewicz P., Kołbuk D., Biodegradation of bicomponent PCL/Gelatin nanofibres electrospun from alternative solvent system. Structure and properties analysis, Electrospun Nano- and Microfibres for Biomedical Applications Conference, 2015-08-31/09-03, Eger (HU), pp.1, 2015
Dulnik J., Denis P., Sajkiewicz P., Kołbuk D., Biodegradation of bicomponent PCL/Gelatin nanofibres electrospun from alternative solvent system. Structure and properties analysis, Electrospun Nano- and Microfibres for Biomedical Applications Conference, 2015-08-31/09-03, Eger (HU), pp.1, 2015

Abstract:
Bicomponent polycaprolactone/gelatin nanofibers were formed by electrospinning as previously described [1] using a novel polymer – solvent system with solvents being alternative to the commonly used toxic solvents like fluorinated alcohols. PCL/Gelatin nanofibres were electrospun from the mixture of acetic acid (AA) with formic acid (FA) (90:10) and from hexafluoroisopropanol (HFIP), that was used as reference solvent. PCL/Gelatin nanofibres with polymers w/w ratios 9:1, 8:2 and 7:3, underwent biodegradation in PBS solution at 37°C. After different times, ranging from 1 to 90 days, they were rinsed in demineralized water and dried. Weight loss and FTIR tests were performed to assess the kinetics of gelatin leaching, while SEM imaging and hydrophobicity tests to show its depletion from the surface. DSC measurements were carried out to examine changes in fibres’ internal structure and uniaxial tensile testing to compare their mechanical properties. Morphology of PCL/Gt fibers obtained from AA/FA is similar to that obtained from HFIP. Despite similar morphology, the internal structure of nanofibers formed from alternative solvents is different, reflecting the emulsive nature of PCL/gelati n mixture in AA/FA solvents contrary to clear, transparent solutions in HFIP. This apparent difference affects strongly the kinetics of leaching of gelatin from bicomponent fibres and thus how their mechanical and bioactive properties are changing in time after placing in living organism. There is substantial difference in kinetics of gelatin leaching depending on solvent used. Mass measurements show much faster gelatin degradation in nanofibres electrospun from AA/FA than from HFIP . For instance, for PCL/Gt 7:3 samples, gelatin content loss is 85% for AA/FA and 68% for HFIP after 90 days. Moreover, irrespective of the solvent used, the degradation rate increases with initial content of gelatin and is the highest in the first 24 hours: 27% for AA/FA 9:1 and 67% for 7:3 and 13% and 32% for HFIP respectively. The observed changes can be explained by nonuniform distribution of gelatin within fibres spun form AA/FA due to emulsive character of solution. Comparison of SEM images reveals linear groove-like sites remaining after gelatin leaching on a surface of fibres spun from AA/FA solvent. Contrary to this, fibres spun from HFIP remain smooth which can be attributed to molecular dispersion of both components.

Keywords:
nanofibers, biodegradation, polycaprolactone, gelatin

5.Kołbuk D., Denis P., Dulnik J., Sajkiewicz P., Modifications of polycaprolactone films crystallinity in terms of tissue engineering applications, 20th Swiss Conference on Biomaterials and Regerative Medicine, 2014-05-07/05-08, Basel (CH), Vol.28, No.6, pp.30, 2014
Kołbuk D., Denis P., Dulnik J., Sajkiewicz P., Modifications of polycaprolactone films crystallinity in terms of tissue engineering applications, 20th Swiss Conference on Biomaterials and Regerative Medicine, 2014-05-07/05-08, Basel (CH), Vol.28, No.6, pp.30, 2014

Abstract:
Few research groups have highlighted the unexpected degree of cell proliferation depending on the degree of crystallinity of the substrate. Commonly used methods of forming three-dimensional scaffolds do not take into account crystallinity optimisation.
The aim of proposed presentation is to investigate polycaprolactone (PCL) substrate supermolecular structure effect, mainly crystallinity, on cells spreading, activity and proliferation.

Keywords:
crystalllinity, PCL, solvent, molecular structure, L929

6.Denis P., Dulnik J., Sajkiewicz P., Electrospinning and structure of bicomponent polycaprolactone/gelatin nanofibers obtained using alternative solvent system, 2nd INTERNATIONAL CONFERENCE ON BIO-BASED POLYMERS AND COMPOSITES, 2014-08-24/08-28, Visegrad (HU), pp.1-2, 2014
Denis P., Dulnik J., Sajkiewicz P., Electrospinning and structure of bicomponent polycaprolactone/gelatin nanofibers obtained using alternative solvent system, 2nd INTERNATIONAL CONFERENCE ON BIO-BASED POLYMERS AND COMPOSITES, 2014-08-24/08-28, Visegrad (HU), pp.1-2, 2014

Abstract:
In this study bicomponent polycaprolactone/gelatin nanofibers were successfully formed by electrospinning using for the first time a novel polymer – solvent system consisting of acetic acid and formic acid. Such solvent system is alternative to the commonly used toxic solvents like fluorinated alcohols, mainly hexafluoroisopropanol. The effect of electrospinning conditions on morphology and structure of nanofibers were investigated.

Keywords:
nanofibers, electrospinning, polycaprolactone, gelatin, alternative solvents, structure

7.Urbanek O., Kucharska M., Dulnik J., Kołbuk D., Bicomponent nanofibers in tissue engineering, Szkoła Zimowa, 2014-12-15/12-16, Warszawa (PL), pp.30, 2014
Urbanek O., Kucharska M., Dulnik J., Kołbuk D., Bicomponent nanofibers in tissue engineering, Szkoła Zimowa, 2014-12-15/12-16, Warszawa (PL), pp.30, 2014

Abstract:
Bicomponent poly(caprolactone)/ chitosan (PCL/Chit) nanofibers are a promising alternative for cartilage tissue regeneration. Chitosan is characterized by high structural similarity to the glycosaminoglycans (GAG) which naturally occur in the extracellular matrix (ECM). Its hydrophilicity is beneficial for cells adhesion and proliferation [1]. The amino groups in chitosan are responsible for the formation of polycations, which subsequently form compounds with natural and synthetic anions (proteins, lipids, synthetic polymers which are negatively charged) [2, 3]. Electrospinning of polycations with positive charge on the needle, is difficult due to the instability of the stream resulting from large repulsion force in the polymer jet [3]. Introduction of synthetic polymer molecules to the solution decreases interactions between the chains of chitosan and reduces the viscosity of the solution, so they are easier to form by electrospinning, as well as with negative charge on the needle [4 ]. A synthetic polymer, which is poly(caprolactone), improves mechanical properties of the fibers and the time of the hydrolytic degradation of the scaffold [4]. Nanofibers are excellent material for cell scaffolds used in tissue engineering because of high similarity of their morphology to native extracellular matrix (ECM) [1, 2]. From the viewpoint of cartilage tissue regeneration scaffold in the form of nanofibers is particularly justified due to naturally occurring network of polymer fibers (proteins and glycosaminoglycans) called aggrecans, in ECM of cartilage. Chondrocytes are connected with aggrecans [4]. Both, the structure and composition of formed nanofibers may affect the time in which cells will reach their proper morphology and undertake its functions [4]. In order to study cell behavior on electrospun PCL/chitosan nonwoven, fibroblasts L929 were cultured. Actin Green staining was conducted in order to imagine actin cytoskeleton of fibroblasts. To characterize, both fibers structure and cell morphology, SEM imagining was done. AFM imaging was carried to describe fibers topography and phase distribution. Also conductivity and viscosity of the PCL/chitosan solution with various polymer ratio was measured.

Keywords:
electrospinninig, scaffolds, PCL, chitozan, cellular responce


Patents
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414353
2015-10-13
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Dulnik J., Denis P., Sajkiewicz P.
Sposób otrzymywania szerokoporowatego, poliestrowego rusztowania komórkowego
PL, Instytut Biocybernetyki i Inżynierii Biomedycznej im. Macieja Nałęcza PAN, Politechnika Warszawska, Instytut Podstawowych Problemów Techniki PAN
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