Multifaceted characterization and in vitro assessment of polyurethane-based electrospun fibrous composite for bone tissue engineering

Introduction: Recently several new approaches were emerging in bone tissue engineering to develop a substitute for remodelling the damaged tissue. In order to resemble the native extracellular matrix (ECM) of the human tissue, the bone scaffolds must possess necessary requirements like large surface area, interconnected pores and sufficient mechanical strength.Materials and methods: A novel bone scaffold has been developed using polyurethane (PE) added with wintergreen (WG) and titanium dioxide (TiO2). The developed nanocomposites were characterized through field emission scanning electron microscopy (FESEM), Fourier transform and infrared spectroscopy (FTIR), X-ray diffraction (XRD), contact angle measurement, thermogravimetric analysis (TGA), atomic force microscopy (AFM) and tensile testing. Furthermore, anticoagulant assays, cell viability analysis and calcium deposition were used to investigate the biological properties of the prepared hybrid nanocomposites.Results: FESEM depicted the reduced fibre diameter for the electrospun PE/WG and PE/WG/TiO2 than the pristine PE. The addition of WG and TiO2 resulted in the alteration in peak intensity of PE as revealed in the FTIR. Wettability measurements showed the PE/WG showed decreased wettability and the PE/WG/TiO2 exhibited improved wettability than the pristine PE. TGA measurements showed the improved thermal behaviour for the PE with the addition of WG and TiO2. Surface analysis indicated that the composite has a smoother surface rather than the pristine PE. Further, the incorporation of WG and TiO2 improved the anticoagulant nature of the pristine PE. In vitro cytotoxicity assay has been performed using fibroblast cells which revealed that the electrospun composites showed good cell attachment and proliferation after 5 days. Moreover, the bone apatite formation study revealed the enhanced deposition of calcium content in the fabricated composites than the pristine PE.Conclusion: Fabricated nanocomposites rendered improved physico-chemical properties, biocompatibility and calcium deposition which are conducive for bone tissue engineering

Studies of surface preparation and structural adhesive bonding of aluminum and other materials

The growing need for lightweight and high-performance structures has fueled extensive research into refining the assembling of materials to bonding using structural adhesives. Unlike conventional methods (e.g., welding, riveting, and bolting), structural adhesive bonding excels by integrating advanced surface treatment techniques. These techniques play a crucial role in determining the stability and performance of the bonded joints. Traditional electrochemical surface treatments (e.g., acid anodization) involves use of acids and raise serious environmental and safety concerns. Hence, the present work aims to utilize eco-friendly, cost-effective, and less complex surface treatment techniques for preparing metal and polymer surfaces, facilitating similar and dissimilar adhesive bonding applications. This thesis work has been developed into two sections. The first section addresses surface preparation and adhesive bonding of metal/metal substrates, and the second section deals with the same on metal/polymer substrates. Aluminum (Al) was selected for the metal/metal system, while Al and polyvinyl chloride (PVC) were chosen as substrates for the metal/polymer system. A mechanical abrasion process using silicon carbide (SiC) and an electrochemical anodization technique were used to surface treat Al to tune it’s wetting properties. The erection of micro-rough structures on Al due to mechanical abrasion enhanced the hydrophilic nature providing a water contact angle of ~53°. The treated surfaces, were bonded using Adhesive #1 and Adhesive #2. This resulted in a relative gain of 46% in their single lap shear (SLS) strength compared to those bonded without any surface treatment using Adhesive #2. Furthermore, the effect of various environments (DI water, 3.5 and 7 wt.% aqueous NaCl solutions) on aging was explored, and a suitable model was proposed to explain the residual SLS strength in these samples. On the other hand, the growth of a porous oxide layer was observed on the Al substrate when it was electrochemically anodized into an aqueous salt solution of disodium hydrogen phosphate (Na2HPO4). The average roughness of these surfaces was found to be ~ 1.4 μm providing a water contact angle of ~42°. These surfaces were bonded using an Adhesive #3, and the relative gain in the obtained SLS strength was 133% compared to as-received Al/Al joints. These results indicated that the anodization technique resulted in a superior performance as compared to the mechanical abrasion when bonded adhesively. Furthermore, the influence of an organosilane, namely [3-glycidoxypropyl] trimethoxysilane (GPS), on the roughness and morphological properties of anodized Al was performed to investigate their influence on the SLS strengths when bonded with Adhesive #4. In this study, the anodization was conducted in aqueous electrolytes of the organic GPS and an inorganic salt of zinc nitrate (Zn(NO3)2. The insertion of GPS molecules during anodization has provided a two-tire roughness effect with microroughness of ~ 8 μm on the anodized Al. These surfaces were bonded using a bio-based organic adhesive, and the measured SLS strength was enhanced by 160% compared to as-received Al/Al joints. As compared to the abrasion and anodization, this technique provides a higher relative gain in the SLS strengths when bonded adhesively. The second part of this work involves bonding PVC with Al, where PVC, by nature, is a hydrophobic material and presents very low surface reactivity and low affinity towards adhesives. Therefore, in order to treat the less reactive PVC, a corona discharge surface treatment method was used to activate their surfaces to favor adhesive bonding. Fourier transform infrared spectroscopy (FTIR) analyses presented evidence of incorporation of –OH polar functional groups at 3390 cm−1 leading to a lowering of water contact angle to ~36° from ~98o on untreated PVC surface, which is favorable to improving the bond strength between PVC and the adhesive. As a result, the SLS strength of adhesively bonded Al/PVC joints demonstrated a relative gain of 300% compared to its as-received counterparts. Apart from modifying the PVC substrates to improve the SLS strength, an additional attempt was made to mix two chemically dissimilar adhesives (epoxy and silicone) to bond two chemically dissimilar substrates (Al and PVC). FTIR spectra of the mixed adhesive revealed the presence of overlapping peaks with PVC, namely –CH2, –CH3 around 2800–3000 cm−1 and Si–CH3 at 1260 cm−1 confirming the signature of both adhesive chemistries. The SLS strength of Al/PVC joints bonded using mixed adhesive showed that the relative gain was 447% higher than that of Al/PVC joints made with only silicone adhesive. In both cases studied, namely, adhesively bonded Al/Al joints and Al/PVC joints, a surface treatment was required to improve the relative gain in the joint strengths. In the case of Al/Al adhesive joints, anodization techniques provided higher relative gain in the joint strengths than the mechanical abrasion treatment. In the case of Al/PVC, corona discharge treatment was required to increase the PVC surface affinity towards adhesive resulting in improved bond strengths. When Al/PVC adhesive joints were made using a mixed epoxy/silicone adhesive, the relative gain in adhesive strengths further increased to higher values. The results indicate the feasibility of tuning the surface characteristics of metals such as aluminum and even the most difficult-to-bond light weight material such as PVC in enhancing the adhesive bond strengths, hence demonstrating potentials to be used in structures where light-weight is increasingly sought. Le besoin croissant de structures légères et performantes a stimulé des recherches approfondies visant à améliorer l'assemblage des matériaux par le biais de liaisons à l'aide d'adhésifs structuraux. Contrairement aux méthodes conventionnelles (par exemple, soudage, rivetage et boulonnage), le collage adhésif structural excelle en intégrant des techniques avancées de traitement de surface. Ces techniques jouent un rôle crucial dans la détermination de la stabilité et des performances des joints collés. Les traitements de surface électrochimiques traditionnels (par exemple, l'anodisation acide) impliquent l'utilisation d'acides et soulèvent d'importantes préoccupations environnementales et de sécurité. Ainsi, le présent travail vise à utiliser des techniques de traitement de surface respectueuses de l'environnement, rentables et moins complexes pour préparer les surfaces métalliques et polymères, facilitant ainsi des applications de collage adhésif similaires et dissemblables. Ce travail de thèse a été développé en deux sections. La première section aborde la préparation de surface et le collage adhésif des substrats métal/métal, tandis que la deuxième section traite de la même chose sur des substrats métal/polymère. L'aluminium (Al) a été sélectionné pour le système métal/métal, tandis que l'Al et le chlorure de polyvinyle (PVC) ont été choisis comme substrats pour le système métal/polymère. Un processus d'abrasion mécanique utilisant du carbure de silicium (SiC) et une technique d'anodisation électrochimique ont été utilisés pour traiter la surface de l'Al afin d'ajuster ses propriétés de mouillage. L'érection de microstructures rugueuses sur l'Al en raison de l'abrasion mécanique a amélioré sa nature hydrophile en fournissant un angle de contact avec l'eau d'environ ~53°. Les surfaces traitées, lorsqu'elles étaient collées avec l'adhésif n #1 et l'adhésif n #2. Cela a entraîné un gain relatif de 46 % dans leur résistance au cisaillement simple (SLS) par rapport à celles collées sans aucun traitement de surface à l'aide de l'adhésif n #2. De plus, l'effet de divers environnements (eau déionisée, solutions aqueuses de NaCl à 3,5 et 7% en poids) sur le vieillissement a été exploré, et un modèle approprié a été proposé pour expliquer la résistance SLS résiduelle dans ces échantillons. D'autre part, la croissance d'une couche d'oxyde poreuse a été observée sur le substrat en Al lorsqu'il était électro chimiquement anodisé dans une solution aqueuse de phosphate de sodium dihydrogène (Na2HPO4). La rugosité moyenne de ces surfaces était d'environ ~1,4 μm, fournissant un angle de contact avec l'eau d'environ ~42°. Ces surfaces ont été collées à l'aide d'un adhésif n #3, et le gain relatif de la résistance SLS obtenue était de 133% par rapport aux joints Al/Al d'origine. Ces résultats indiquent que la technique d'anodisation a conduit à une performance supérieure par rapport à l'abrasion mécanique lorsqu'elle est collée adhésivement. De plus, l'influence d'un organosilane, à savoir le [3-glycidoxypropyl] triméthoxysilane (GPS), sur la rugosité et les propriétés morphologiques de l'aluminium anodisé a été étudiée pour investiguer leur influence sur les résistances au cisaillement simple (SLS) lorsqu'elles sont collées avec l'adhésif n #4. Dans cette étude, l'anodisation a été réalisée dans des électrolytes aqueux du GPS organique et d'un sel inorganique de nitrate de zinc (Zn(NO3)2). L'insertion de molécules de GPS pendant l'anodisation a produit un effet de rugosité à deux niveaux avec une microrugosité d'environ ~8 μm sur l'aluminium anodisé. Ces surfaces ont été collées à l'aide d'un adhésif organique à base biologique, et la résistance mesurée au cisaillement simple (SLS) a été améliorée de 160% par rapport aux joints d'aluminium d'origine. En comparaison avec l'abrasion et l'anodisation, cette technique offre un gain relatif plus élevé dans les résistances SLS lorsqu'elle est utilisée pour le collage adhésif. La deuxième partie de ce travail implique le collage du PVC avec de l'aluminium, le PVC étant, par nature, un matériau hydrophobe présentant une réactivité de surface très faible et une faible affinité envers les adhésifs. Par conséquent, afin de traiter le PVC moins réactif, une méthode de traitement de surface par décharge corona a été utilisée pour activer leurs surfaces en faveur du collage adhésif. Les analyses de spectroscopie infrarouge à transformée de Fourier (FTIR) ont présenté des preuves de l'incorporation de groupes fonctionnels polaires –OH à 3390 cm−1, entraînant une réduction de l'angle de contact avec l'eau à environ ~36° par rapport aux ~98° de la surface de PVC non traitée, ce qui est favorable à l'amélioration de la résistance de liaison entre le PVC et l'adhésif. En conséquence, la résistance au cisaillement simple (SLS) des joints Al/PVC collés adhésivement a montré un gain relatif de 300% par rapport à leurs homologues d'origine. En plus de modifier les substrats en PVC pour améliorer la résistance SLS, une tentative supplémentaire a été faite pour mélanger deux adhésifs chimiquement différents (époxy et silicone) pour coller deux substrats chimiquement différents (Al et PVC). Les spectres FTIR de l'adhésif mélangé ont révélé la présence de pics superposés avec le PVC, notamment –CH2, –CH3 autour de 2800–3000 cm−1 et Si–CH3 à 1260 cm−1, confirmant la signature des deux chimies adhésives. La résistance SLS des joints Al/PVC collés avec l'adhésif mixte a montré que le gain relatif était 447% plus élevé que celui des joints Al/PVC fabriqués uniquement avec de l'adhésif silicone. Dans les deux cas étudiés, à savoir les joints collés adhésivement Al/Al et Al/PVC, un traitement de surface était nécessaire pour améliorer le gain relatif des résistances des joints. Dans le cas des joints adhésifs Al/Al, les techniques d'anodisation ont fourni un gain relatif plus élevé dans les résistances des joints que le traitement par abrasion mécanique. Dans le cas du Al/PVC, un traitement par décharge corona était nécessaire pour augmenter l'affinité de la surface du PVC envers l'adhésif, ce qui a conduit à des résistances de liaison améliorées. Lorsque des joints adhésifs Al/PVC ont été réalisés à l'aide d'un adhésif mixte époxy/silicone, le gain relatif des résistances adhésives a encore augmenté à des valeurs plus élevées. Les résultats indiquent la faisabilité d'ajuster les caractéristiques de surface de métaux tels que l'aluminium et même de matériaux légers difficiles à coller comme le PVC, ce qui améliore les résistances des liaisons adhésives, démontrant ainsi un potentiel d'utilisation dans des structures où la légèreté est de plus en plus recherchée

Engineering electrospun multicomponent polyurethane scaffolding platform comprising grapeseed oil and honey/propolis for bone tissue regeneration

Essential oils play an important role in reducing the pain and inflammation caused by bone fracture.In this study, a scaffold was electrospun based on polyurethane (PU), grape seed oil, honey and propolis for bone tissue-engineering applications. The fiber diameter of the electrospun PU/grape seed oil scaffold and PU/grape seed oil/honey/propolis scaffold were observed to be reduced compared to the pristine PU control. FTIR analysis revealed the existence of grape seed oil, honey and propolis in PU identified by CH band peak shift and also hydrogen bond formation. The contact angle of PU/grape seed oil scaffold was found to increase owing to hydrophobic nature and the contact angle for the PU/grape seed/honey oil/propolis scaffold were decreased because of hydrophilic nature. Further, the prepared PU/grape seed oil and PU/grape seed oil/honey/propolis scaffold showed enhanced thermal stability and reduction in surface roughness than the control as revealed in thermogravimetric analysis (TGA) and atomic force microscopy (AFM) analysis. Further, the developed nanocomposite scaffold displayed delayed blood clotting time than the pristine PU in the activated prothrombin time (APTT) and partial thromboplastin time (PT) assay. The hemolytic assay and cytocompatibility studies revealed that the electrospun PU/grape seed oil and PU/grape seed oil/honey/propolis scaffold possess non-Toxic behaviour to red blood cells (RBC) and human fibroblast cells (HDF) cells indicating better blood compatibility and cell viability rates. Hence, the newly developed electrospun nanofibrous composite scaffold with desirable characteristics might be used as an alternative candidate for bone tissue engineering applications

Viral Infections and Neonatal Necrotizing Enterocolitis: A Meta-analysis.

CONTEXT: Necrotizing enterocolitis (NEC) is a devastating intestinal disease affecting preterm infants. Studies implicate viral infections in etiopathogenesis. OBJECTIVE: To summarize the association of viral infections with NEC by systematic review and meta-analysis. DATA SOURCES: We searched Ovid-Medline, Embase, Web of Science, and Cochrane databases in November 2022. STUDY SELECTION: We included observational studies that examined the association between viral infections and NEC in newborn infants. DATA EXTRACTION: We extracted data regarding the methodology, participant characteristics, and outcome measures. RESULTS: We included 29 and 24 studies in the qualitative review and meta-analysis, respectively. The meta-analysis demonstrated a significant association between viral infections and NEC (odds ratio [OR], 3.81, 95% confidence interval: 1.99-7.30, 24 studies). The association remained significant after excluding the outliers (OR, 2.89 [1.56-5.36], 22 studies) and studies with poor methodology (OR, 3.33 [1.73-6.43], 22 studies). In subgroup analysis based on participants\u27 birth weight, studies including very low birth weight infants only (OR, 3.62 [1.63-8.03], 8 studies) and non-very low birth weight infants only (OR, 5.28 [1.69-16.54], 6 studies) showed a significant association. In subgroup analysis based on specific viruses, infection with rotavirus (OR, 3.96 [1.12-13.95], 10 studies), cytomegalovirus (OR, 3.50 [1.60-7.65], 5 studies), norovirus (OR, 11.95 [2.05-69.84], 2 studies), and astrovirus (OR, 6.32 [2.49-16.02], 2 studies) was significantly associated with NEC. LIMITATIONS: Heterogeneity of the included studies. CONCLUSIONS: Viral infection is associated with an increased risk of NEC in newborn infants. We need methodologically sound prospective studies to assess the effect of preventing or treating viral infections on NEC incidence

Giant Magnetoresistance and Structure of Electrodeposited Co/Cu Multilayers: The Influence of Layer Thicknesses and Cu Deposition Potential

The giant magnetoresistance (GMR) and structure was investigated for electrodeposited Co/Cu multilayers prepared by a conventional galvanostatic/potentiostatic pulse combination from a pure sulfate electrolyte with various layer thicknesses, total multilayer thickness and Cu deposition potential. X-ray diffraction (XRD) measurements revealed superlattice satellite reflections for many of the multilayers having sufficiently large thickness (at least 2 nm) of both constituent layers. The bilayer repeats derived from the positions of the visible superlattice reflections were typically 10 – 20% higher than the nominal values.The observed GMR was found to be dominated by the multilayer-like ferromagnetic (FM) contribution even for multilayers without visible superlattice satellites. There was always also a modest superparamagnetic (SPM) contribution to the GMR and this term was the largest for multilayers with very thin (0.5 nm) magnetic layers containg apparently a small amount of magnetically decoupled SPM regions. No oscillatory GMR behavior with spacer thickness was observed at any magnetic layer thickness. The saturation of the coercivity as measured by the peak position of the MR(H) curves indicated a complete decoupling of magnetic layers for large spacer thicknesses. The GMR increased with total multilayer thickness which could be ascribed to an increasing SPM contribution to the GMR due to an increasing surface roughness, also indicated by the increasing coercivity. For multilayers with Cu layers deposited at more and more positive potentials, the GMRFM term increased and the GMRSPM term decreased. At the same time, a corresponding reduction of surface roughness measured with atomic force microscopy indicated an improvement of the multilayer structural quality which was, however, not accompanied by an increase of the superlattice reflection intensities. The present results underline that whereas the structural quality as characterized by the surface roughness generally correlates fairly well with the magnitude of the GMR, the microstructural features determining the amplitude of superlattice reflections apparently do not have a direct influence on the GMR

Grapefruit Oil and Cobalt Nitrate-Loaded Polyurethane Hybrid Nanofibrous Scaffold for Biomedical Applications

The goal of this work is to fabricate a new composite based on polyurethane (PU), grapefruit (GP) oil, and cobalt nitrate [Co(NO3)2] using an electrospinning technique. Morphology results revealed the reduction in the fiber diameter of the composites compared to pristine PU control. The interaction of PU with GP and Co(NO3)2 was confirmed by hydrogen bond formation evident in infrared analysis. The fabricated PU/GP composites depicted a more hydrophobic behavior, while PU/GP/Co(NO3)2 showed a hydrophilic behavior than the pristine PU. Atomic force micrographs (AFM) revealed that the developed composites showed a decrease in the surface roughness (Ra) compared to PU. The addition of GP and Co(NO3)2 improved the mechanical strength of the pristine PU. The blood compatibility assays concluded not only the increase in blood clotting levels but also the less toxic nature of the fabricated composites compared to the pristine PU. Hence, the newly designed composites possessing outstanding physicochemical and biological properties may be used as a potential candidate for scaffolding in tissue engineering applications

Biomimetic electrospun polyurethane matrix composites with tailor made properties for bone tissue engineering scaffolds

Bone tissue scaffolds require appropriate properties conducive for new tissue growth. In this study, we prepared a novel electrospun nanofiber scaffold using polyurethane (PU), rosemary (RM) oil and copper sulphate (CuSO4) respectively. The properties of the developed membranes were established through scanning electron microscopy (FESEM), atomic force microscopy (AFM), attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), thermal gravimetric analysis (TGA), contact angle and mechanical testing. Further, blood compatibility and cytocompatibility assay were carried out to evaluate their biological responses. The developed composites rendered appropriate surface morphology with tailor made wettability and roughness. Composites with engineered physicochemical properties improved the blood and cytocompatible properties which can be potentially exploited for bone tissue engineering applications

Electrospun polyurethane nanofibrous composite impregnated with metallic copper for wound-healing application

In this study, a wound dressing based on polyurethane (PU) blended with copper sulphate nanofibers was developed using an electrospinning technique. The prepared PU and PU nanocomposites showed smooth fibers without any bead defects. The prepared nanocomposites showed smaller fiber (663 ± 156.30 nm) and pore (888 ± 70.93 nm) diameter compared to the pristine PU (fiber diameter 1159 ± 147.48 nm and pore diameter 1087 ± 62.51 nm). The interaction of PU with copper sulphate was evident in the infrared spectrum through hydrogen-bond formation. Thermal analysis displayed enhanced weight residue at higher temperature suggesting interaction of PU with copper sulphate. The contact angle measurements revealed the hydrophilic nature of the prepared nanocomposites (71° ± 2.309°) compared with pure PU (100° ± 0.5774°). The addition of copper sulphate into the PU matrix increased the surface roughness, as revealed in the atomic force microscopy (AFM) analysis. Mechanical testing demonstrated the enhanced tensile strength behavior of the fabricated nanocomposites (18.58 MPa) compared with the pristine PU (7.12 MPa). The coagulation assays indicated the enhanced blood compatibility of the developed nanocomposites [activated partial thromboplastin time (APTT)—179 ± 3.606 s and partial thromboplastin time (PT)—105 ± 2.646 s] by showing a prolonged blood clotting time compared with the pristine PU (APTT—147.7 ± 3.512 s and PT—84.67 ± 2.517 s). Furthermore, the hemolysis and cytotoxicity studies suggested a less toxicity nature of prepared nanocomposites by displaying low hemolytic index and enhanced cell viability rates compared with the PU membrane. It was observed that the fabricated novel wound dressing possesses better physicochemical and enhanced blood compatibility properties, and may be utilized for wound-healing applications

Microwave-Assisted Dip Coating of Aloe Vera on Metallocene Polyethylene Incorporated with Nano-Rods of Hydroxyapaptite for Bone Tissue Engineering

Bone tissue engineering widely explores the use of ceramic reinforced polymer-matrix composites. Among the various widely-used ceramic reinforcements, hydroxyapatite is an undisputed choice due to its inherent osteoconductive nature. In this study, a novel nanocomposite comprising metallocene polyethylene (mPE) incorporated with nano-hydroxyapaptite nanorods (mPE-nHA) was synthesized and dip coated with Aloe vera after subjecting it to microwave treatment. The samples were characterized using contact angle, Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), atomic force microscopy (AFM) and 3D Hirox microscopy scanning. Contact angle results show that the hydrophilicity of mPE-nHA improved notably with the coating of Aloe vera. The surface topology and increase in surface roughness were observed using the SEM, AFM and 3D Hirox microscopy. Blood compatibility assays of pure mPE and the Aloe vera coated nanocomposite were performed. The prothrombin time (PT) was delayed by 1.06% for 24 h Aloe-vera-treated mPE-nHA compared to the pristine mPE-nHA. Similarly, the 24 h Aloe-vera-coated mPE-nHA nanocomposite prolonged the activated partial thromboplastin time (APTT) by 41 s against the control of pristine mPE-nHA. The hemolysis percentage was also found to be the least for the 24 h Aloe-vera-treated mPE-nHA which was only 0.2449% compared to the pristine mPE-nHA, which was 2.188%. To conclude, this novel hydroxyapatite-reinforced, Aloe-vera-coated mPE with a better mechanical and anti-thrombogenic nature may hold a great potential to be exploited for bone tissue engineering applications