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Abstract:
In recent years, one of the main goals of cartilage tissue engineering has been to find appropriate scaffolds for hyaline cartilage regeneration, which could serve as a matrix for chondrocytes or stem cell cultures. The study presents three types of scaffolds obtained from a blend of polyethersulfone (PES) and polyurethane (PUR) by a combination of wet-phase inversion and salt-leaching methods. The nonwovens made of gelatin and sodium chloride (NaCl) were used as precursors of macropores. Thus, obtained membranes were characterized by a suitable structure. The top layers were perforated, with pores over 20 µm, which allows cells to enter the membrane. The use of a nonwoven made it possible to develop a three-dimensional network of interconnected macropores that is required for cell activity and mobility. Examination of wettability (contact angle, swelling ratio) showed a hydrophilic nature of scaffolds. The mechanical test showed that the scaffolds were suitable for knee joint applications (stress above 10 MPa). Next, the scaffolds underwent a degradation study in simulated body fluid (SBF). Weight loss after four weeks and changes in structure were assessed using scanning electron microscopy (SEM) and MeMoExplorer Software, a program that estimates the size of pores. The porosity measurements after degradation confirmed an increase in pore size, as expected. Hydrolysis was confirmed by Fourier-transform infrared spectroscopy (FT-IR) analysis, where the disappearance of ester bonds at about 1730 cm −1 wavelength is noticeable after degradation. The obtained results showed that the scaffolds meet the requirements for cartilage tissue engineering membranes and should undergo further testing on an animal model.

Keywords:
articular cartilage, cartilage tissue engineering, hydrolysis process, materials for scaffolds, partly degradable scaffolds, polyethersulfone–polyurethane scaffolds, polyurethane degradation, regenerative medicine, scaffold requirements, tissue engineering

Abstract:
The cartilage tissue is neither supplied with blood nor innervated, so it cannot heal by itself. Thus, its reconstruction is highly challenging and requires external support. Cartilage diseases are becoming more common due to the aging population and obesity. Among young people, it is usually a post-traumatic complication. Slight cartilage damage leads to the spontaneous formation of fibrous tissue, not resistant to abrasion and stress, resulting in cartilage degradation and the progression of the disease. For these reasons, cartilage regeneration requires further research, including use of new type of biomaterials for scaffolds. This paper shows cartilage characteristics within its most frequent problems and treatment strategies, including a promising method that combines scaffolds and human cells. Structure and material requirements, manufacturing methods, and commercially available scaffolds were described. Also, the comparison of poly(L-lactide) (PLLA) and polyethersulfone (PES) 3D membranes obtained by a phase inversion method using nonwovens as a pore-forming additives were reported. The scaffolds' structure and the growth ability of human chondrocytes were compared. Scaffolds' structure, cells morphology, and protein presence in the membranes were examined with a scanning electron microscope. The metabolic activity of cells was tested with the MTT assay. The structure of the scaffolds and the growth capacity of human chondrocytes were compared. Obtained results showed higher cell activity and protein content for PES scaffolds than for PLLA. The PES membrane had better mechanical properties (e.g. ripping), greater chondrocytes proliferation, and thus a better secretion of proteins which build up the cartilage structure.

Keywords:
3D-scaffolds, membrane structure, polyethersulfone, poly(L-lactide), chondrocyte culture, cartilage regeneration

Abstract:
The study presents two types of three-dimensional membranes made of the biodegradable copolymer. They were obtained by the wet-phase inversion method using different solvent and pore precursors. In one case, a nonwoven made of gelatin and polyvinylpyrrolidone (PVP) as precursors of macropores and small pores, respectively, were used. In the second case, PVP nonwovens and Pluronic were used properly for macro- and micro-pores. As the material, a biodegradable poly(L-lactide-co-ε-caprolactone) is composed of 30% ε-caprolactone and 70% poly(L-lactic acid) was used. Depending on the pore precursors, different membrane structures were obtained. The morphology of pores was studied using the MeMoExplorer™, an advanced software designed for computer analysis of the scanning electron microscopy images. The scaffolds were degraded in phosphate-buffered saline and Hank’s balanced salt solutions at 37°C. Moreover, the porosity of the membranes before and after hydrolysis was calculated.

Keywords:
3D scaffolds, poly(L-lactide-co-ε-caprolactone), porosity of membrane, phase inversion method, degradation of scaffolds

Abstract:
Novel polyurethanes based on synthetic, atactic poly[(R, S)-3-hydroxybutyrate] (a-PHB) and polycaprolactone (PCL) or polyoxytetramethylene (PTMG) diols were synthesized. It was shown that the presence of a-PHB within soft segments reduces crystallinity of PUR. Because of the low melting temperature for polyurethanes with PCL in soft segments, at this stage of work, electrospinning was limited to polyurethanes containing PTMG and a-PHB. Polyurethane containing 80% of PTMG and 20% of a-PHB was electrospun at various parameters from hexafluoro-2-propanole solution, resulting in formation of fibers with the average diameter ca. 2 μm. The fiber diameter decreased with decreasing polymer concentration in a solution and was practically insensitive to the needle-collector distance in the applied range of distances.

Keywords:
polyurethane, polyhydroxybutyrate, electrospinning, scaffolds