Исследование волокнистых 3-д полимерных скэффолдов полученных методом электроформирования с минерализованой поверхностью волокон для костной инженерии

В настоящей работе приведены результаты получения нетканых волокнистых трехмерных скэффолдов на основе полигидроксибутирата или полигидроксибутират-гидроксивалерата с минерализованной поверхностью волокон по всему объему скэффолда, и исследования их морфологии, химического состава и структуры. Скэффолды были получены методом электроформирования при скорости вращения коллектора 1200 или 600 об/мин. Для получения полностью покрытых волокон повсему объему скэффолда частицами карбоната кальция использовалась ультразвуковая обработка в растворах хлористого кальция и карбоната натрия. Осуществлялся контроль массы образцов до и после каждой обработки. Для исследования морфологии скэффолдов использовалась сканирующая электронная микроскопия. Для исследования структуры и химического состава образцов использовались рентгеновский фазовый анализ и энергодисперсионная рентгеновская спектроскопия, соответственно

Influence of Anodization Time and Voltage on the Parameters of TiO[2] Nanotubes

A vertically aligned titania nanotube layer was obtained by electrochemical anodic oxidation in the electrolyte contained 0.4 wt% solution of NH[4]F in 54 ml of ethylene glycol and 5 ml of deionized water, after titanium was chemically cleaned/etched with a mixture of HCl, H[2]O and HNO[3] solution for removing the natural oxide films. The morphology and composition of the titania nanotube layer were examined by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The anodization of TiO[2] nanotubes was done using 60 V for 240 min and 30 min, and 30 V for 30 min. The diameter of the titania nanotubes was about 52-156 nm, the wall thickness about 32-53 nm and the height about 0.9-6.3 [mu]m. The pore size of TiO[2] nanotubes influences the dissolution rate of CaP thin films and Young's modulus, which is significantly lower than that of the Ti substrate. Our future challenge will be investigation of the microstructure and mechanical behavior of titania nanotubes with CaP film

Influence of Calcium-Phosphate Coating on Wettability of Hybrid Piezoelectric Scaffolds

Herein, electrospun biodegradable scaffolds based on polycaprolactone (PCL), poly(3-hydroxybutyrate) (PHB) and polyaniline (PANi) polymers were fabricated. A calcium-phosphate (CaP) coating was deposited on the surface of the scaffolds via an improved soaking process. Influence of the deposition cycles and ethanol concentration in the solution on the relative increase of the scaffolds weight and water contact angle (WCA) are determined. The characterization of the molecular and crystal structure confirmed the formation of CaP phase. Importantly, WCA results showed that the pristine scaffolds have the hydrophobic surface, while the deposition of CaP coating onto scaffolds allows to significantly improve the surface wetting behavior, and infiltration of the water droplets into the CaP-coated scaffolds was observed. Thus, the fabricated hybrid biodegradable piezoelectric scaffolds can be utilized for regenerative medicine

Core-shell magnetoactive PHB/gelatin/magnetite composite electrospun scaffolds for biomedical applications

Novel hybrid magnetoactive composite scaffolds based on poly(3-hydroxybutyrate) (PHB), gelatin, and magnetite (Fe3O4) were fabricated by electrospinning. The morphology, structure, phase composition, and magnetic properties of composite scaffolds were studied. Fabrication procedures of PHB/gelatin and PHB/gelatin/Fe3O4 scaffolds resulted in the formation of both core-shell and ribbon-shaped structure of the fibers. In case of hybrid PHB/gelatin/Fe3O4 scaffolds submicron-sized Fe3O4 particles were observed in the surface layers of the fibers. The X-ray photoelectron spectroscopy results allowed the presence of gelatin on the fiber surface (N/C ratio–0.11) to be revealed. Incubation of the composite scaffolds in saline for 3 h decreased the amount of gelatin on the surface by more than ~75%. The differential scanning calorimetry results obtained for pure PHB scaffolds revealed a characteristic melting peak at 177.5 °C. The presence of gelatin in PHB/gelatin and PHB/gelatin/Fe3O4 scaffolds resulted in the decrease in melting temperature to 168–169 °C in comparison with pure PHB scaffolds due to the core-shell structure of the fibers. Hybrid scaffolds also demonstrated a decrease in crystallinity from 52.3% (PHB) to 16.9% (PHB/gelatin) and 9.2% (PHB/gelatin/Fe3O4). All the prepared scaffolds were non-toxic and saturation magnetization of the composite scaffolds with magnetite was 3.27 ± 0.22 emu/g, which makes them prospective candidates for usage in biomedical applications

Electrospun magnetic composite poly-3-hydroxybutyrate/magnetite scaffolds for biomedical applications: composition, structure, magnetic properties, and biological performance

Magnetically responsive composite polymer scaffolds have good potential for a variety of biomedical applications. In this work, electrospun composite scaffolds made of polyhydroxybutyrate (PHB) and magnetite (Fe3O4) particles (MPs) were studied before and after degradation in either PBS or a lipase solution. MPs of different sizes with high saturation magnetization were synthesized by the coprecipitation method followed by coating with citric acid (CA). Nanosized MPs were prone to magnetite-maghemite phase transformation during scaffold fabrication, as revealed by Raman spectroscopy; however, for CA-functionalized nanoparticles, the main phase was found to be magnetite, with some traces of maghemite. Submicron MPs were resistant to the magnetite-maghemite phase transformation. MPs did not significantly affect the morphology and diameter of PHB fibers. The scaffolds containing CA-coated MPs lost 0.3 or 0.2% of mass in the lipase solution and PBS, respectively, whereas scaffolds doped with unmodified MPs showed no mass changes after 1 month of incubation in either medium. In all electrospun scaffolds, no alterations of the fiber morphology were observed. Possible mechanisms of the crystalline-lamellar-structure changes in hybrid PHB/Fe3O4 scaffolds during hydrolytic and enzymatic degradation are proposed. It was revealed that particle size and particle surface functionalization affect the mechanical properties of the hybrid scaffolds. The addition of unmodified MPs increased scaffolds' ultimate strength but reduced elongation at break after the biodegradation, whereas simultaneous increases in both parameters were observed for composite scaffolds doped with CA-coated MPs. The highest saturation magnetization-higher than that published in the literature-was registered for composite PHB scaffolds doped with submicron MPs. All PHB scaffolds proved to be biocompatible, and the ones doped with nanosized MPs yielded faster proliferation of rat mesenchymal stem cells. In addition, all electrospun scaffolds were able to support angiogenesis in vivo at 30 days after implantation in Wistar rats

Hybrid biodegradable 3D scaffolds based on piezoelectric poly(3-hydroxybutyrate) for tissue engineering

Endogenous bioelectrical signals are one of the most relevant cues to determine tissue function in electrosensitive tissues and thus play a vital role in the tissue regeneration process. In this regard, piezoelectricity is considered as one of the key functionalities in biomaterials to electrically stimulate tissue regeneration. However, the integration of biocompatibility, biodegradability and 3D structure with pronounced piezoelectric activity to support tissues repair remains a challenge. Furthermore, the mere presence of a matrix for cell growth is often not sufficient for a good cell adhesion and proliferation; this often requires other components, which would provide additional functionalities, for example, improve cell adhesion and proliferation, provide antibacterial protection, etc (polymers, nano- and micro- particles, biological molecules, such as enzymes, and antibiotics). That stimulates development of hybrid polymer-based materials incorporating both organic and inorganic components. Composite biodegradable and piezoelectric polymer-based materials are emerging as a very potent and promising class of materials due to their diverse properties, which are proved to be a viable tool for tissue engineering applications for the formation of the extracellular matrix (ECM), avoiding a second surgery, and providing electrical stimulation. In this work, novel hybrid 3-D electrospun scaffolds are developed to improve cell adhesion and proliferation, biomimetic mineralization, and antibacterial activity. These scaffolds are based on biodegradable natural poly(3-hydroxybutyrete) polymer, which has piezoelectric properties relevant for a close contact to bone tissue. Specifically in this thesis work: 1) it has been demonstrated, for the first time to the best of our knowledge, that under dynamically applied mechanical stress, piezoelectric PHB-based scaffolds are capable of providing an enhanced biomimetic mineralization and more homogenous growth of the inorganic bone phases, such as calcium carbonate, resulting in an improved cell adhesion and proliferation; 2) design of composite PHB-based scaffolds is pursued by functionalizing it with CaCO3 particles and subsequent drug immobilization, which results in an enhanced osteoblastic cell adhesion/proliferation and 17 pronounced antibacterial effects; 3) surface functionalization of electrospun PHB-based scaffolds is performed close to surface monomolecular level by a non-destructive diazonium approach, leading to preserved piezoresponses and an improved wettability, which are important for cell adhesion for regenerative tissue engineering; 4) design of hybrid biodegradable PHB-based scaffolds are pursued by their functionalization with reduced graphene oxide (rGO) nanoflakes, resulting in an enhanced surface potential and piezoresponses, demonstrating improved cell adhesion and proliferation under static and dynamic mechanical conditions; 5) investigation of the biodegradation process and studies of its impact on the composition, structure, physio-mechanical and electromechanical properties of hybrid PHB-rGO scaffolds with an enhanced piezoresponses are performed. Our results emphasize the added value of hybrid biodegradable and piezoelectric polymer-based materials and approaches, particularly involving functionalization by microparticles, surface chemistry and bioactive molecules. Such new materials are envisioned to find applications in tissue engineering, biomedicine, and biology

Hybrid biodegradable electrospun scaffolds based on poly(l-lactic acid) and reduced graphene oxide with improved piezoelectric response

Piezoelectric poly-L-lactide (PLLA) is a biodegradable polymer used in various biomedical applications. However, tailoring and controlling the structure of PLLA to enhance its piezoelectric response remains a challenge. In this work, extensive characterization was performed to reveal the effect of the reduced graphene oxide (rGO) content (0.2, 0.7, and 1.0 wt%) on the morphology, structure, thermal and piezoelectric behavior of PLLA scaffolds. Randomly oriented homogeneous fibers and a quasi-amorphous structure for pure PLLA and hybrid PLLA-rGO scaffolds were revealed. The addition of rGO affected the molecular structure of the PLLA scaffolds: for example, the number of polar C=O functional groups was increased. Increasing the content of rGO to 1 wt% resulted in decreased glass transition and melting temperatures and increased the degree of crystallinity of the scaffolds. The addition of 0.2 wt% rGO enhanced the effective local vertical and lateral piezoresponses by 2.3 and 15.4 times, respectively, in comparison with pure PLLA fibers. The presence of the shear piezoelectric alpha-phase (P2(1)2(1)2(1)) in uniaxially oriented PLLA fibers and C=O bond rotation in the polymer chains explained the observed piezoresponse. Thus, this study revealed routes to prepare hybrid biodegradable scaffolds with enhanced piezoresponse for tissue engineering applications

Piezoelectric hybrid scaffolds mineralized with calcium carbonate for tissue engineering : analysis of local enzyme and small-molecule drug delivery, cell response and antibacterial performance

As the next generation of materials for bone reconstruction, we propose a multifunctional bioactive platform based on biodegradable piezoelectric polyhydroxybutyrate (PHB) fibrous scaffolds for tissue engineering with drug delivery capabilities. To use the entire surface area for local drug delivery, the scaffold surface was uniformly biomineralized with biocompatible calcium carbonate (CaCO3) microparticles in a vaterite–calcite polymorph mixture. CaCO3-coated PHB scaffolds demonstrated a similar elastic modulus compared to that of pristine one. However, reduced tensile strength and failure strain of 31% and 67% were observed, respectively. The biomimetic immobilization of enzyme alkaline phosphatase (ALP) and glycopeptide antibiotic vancomycin (VCM) preserved the CaCO3-mineralized PHB scaffold morphology and resulted in partial recrystallization of vaterite to calcite. In comparison to pristine scaffolds, the loading efficiency of CaCO3-mineralized PHB scaffolds was 4.6 and 3.5 times higher for VCM and ALP, respectively. Despite the increased number of cells incubated with ALP-immobilized scaffolds (up to 61% for non-mineralized and up to 36% for mineralized), the CaCO3-mineralized PHB scaffolds showed cell adhesion; those containing both VCM and ALP molecules had the highest cell density. Importantly, no toxicity for pre-osteoblastic cells was detected, even in the VCM-immobilized scaffolds. In contrast with antibiotic-free scaffolds, the VCM-immobilized ones had a pronounced antibacterial effect against gram-positive bacteria Staphylococcus aureus. Thus, piezoelectric hybrid PHB scaffolds modified with CaCO3 layers and immobilized VCM/ALP are promising materials in bone tissue engineering