In vitro high-content tissue models to address precision medicine challenges.

The field of precision medicine allows for tailor-made treatments specific to a patient and thereby improve the efficiency and accuracy of disease prevention, diagnosis, and treatment and at the same time would reduce the cost, redundant treatment, and side effects of current treatments. Here, the combination of organ-on-a-chip and bioprinting into engineering high-content in vitro tissue models is envisioned to address some precision medicine challenges. This strategy could be employed to tackle the current coronavirus disease 2019 (COVID-19), which has made a significant impact and paradigm shift in our society. Nevertheless, despite that vaccines against COVID-19 have been successfully developed and vaccination programs are already being deployed worldwide, it will likely require some time before it is available to everyone. Furthermore, there are still some uncertainties and lack of a full understanding of the virus as demonstrated in the high number new mutations arising worldwide and reinfections of already vaccinated individuals. To this end, efficient diagnostic tools and treatments are still urgently needed. In this context, the convergence of bioprinting and organ-on-a-chip technologies, either used alone or in combination, could possibly function as a prominent tool in addressing the current pandemic. This could enable facile advances of important tools, diagnostics, and better physiologically representative in vitro models specific to individuals allowing for faster and more accurate screening of therapeutics evaluating their efficacy and toxicity. This review will cover such technological advances and highlight what is needed for the field to mature for tackling the various needs for current and future pandemics as well as their relevancy towards precision medicine.

Catalyst-Free Click Chemistry for Engineering Chondroitin Sulfate-Multiarmed PEG Hydrogels for Skin Tissue Engineering.

The quest for an ideal biomaterial perfectly matching the microenvironment of the surrounding tissues and cells is an endless challenge within biomedical research, in addition to integrating this with a facile and sustainable technology for its preparation. Engineering hydrogels through click chemistry would promote the sustainable invention of tailor-made hydrogels. Herein, we disclose a versatile and facile catalyst-free click chemistry for the generation of an innovative hydrogel by combining chondroitin sulfate (CS) and polyethylene glycol (PEG). Various multi-armed PEG-Norbornene (A-PEG-N) with different molecular sizes were investigated to generate crosslinked copolymers with tunable rheological and mechanical properties. The crosslinked and mechanically stable porous hydrogels could be generated by simply mixing the two clickable Tetrazine-CS (TCS) and A-PEG-N components, generating a self-standing hydrogel within minutes. The leading candidate (TCS-8A-PEG-N (40 kD)), based on the mechanical and biocompatibility results, was further employed as a scaffold to improve wound closure and blood flow in vivo. The hydrogel demonstrated not only enhanced blood perfusion and an increased number of blood vessels, but also desirable fibrous matrix orientation and normal collagen deposition. Taken together, these results demonstrate the potential of the hydrogel to improve wound repair and hold promise for in situ skin tissue engineering applications.

Rotary Jet-Spun Polycaprolactone/Hydroxyapatite and Carbon Nanotube Scaffolds Seeded with Bone Marrow Mesenchymal Stem Cells Increase Bone Neoformation.

Clinically, bone tissue replacements and/or bone repair are challenging. Strategies based on well-defined combinations of osteoconductive materials and osteogenic cells are promising to improve bone regeneration but still require improvement. Herein, we combined polycaprolactone (PCL) fibers, carbon nanotubes (CNT), and hydroxyapatite (nHap) nanoparticles to develop the next generation of bone regeneration material. Fibers formed by rotary jet spinning (RJS) instead of traditional electrospinning (ES) with embedded bone marrow mesenchymal stem cells (BMMSCs) showed the best outcomes to repair rat calvarial defects after 6 weeks. To understand this, it was observed that different morphologies were formed depending on the manufacturing method used. RJS fibers presented a particular topography with rough fibers, which allowed for better cellular growth and cell spreading in vitro around and into a three-dimensional (3D) mesh, while fibers made by ES were more smooth and cellular growth was only measured on the 3D mesh surface. The fibers with incorporated nHap/CNT nanoparticles enhanced in vitro cell performance as indicated by more cellular proliferation, alkaline phosphatase activity, proliferation, and deposition of calcium. Greater bone neoformation occurred by combining three characteristics: the presence of nHap and CNT nanoparticles, the topography of the RJS fibers, and the addition of BMMSCs. RJS fibers with nanoparticles and seeded with BMMSCs showed 10 136 mm3 of bone neoformation, meaning a 10-fold increase compared to using RJS only and BMMSCs (0.853 mm3) and a 5-fold increase from using ES only (2054 mm3) after 6 weeks of implantation. Conversely, none of these approaches used individually showed any significant difference for in vivo bone neoformation, suggesting that their combination is essential for optimizing bone formation. In summary, our work generated a potential material composed of well-defined combinations of suitable scaffolds seeded with BMMSCs for enhancing numerous orthopedic tissue engineering applications.

Rotary-jet spun polycaprolactone/nano-hydroxyapatite scaffolds modified by simulated body fluid influenced the flexural mode of the neoformed bone.

Polycaprolactone (PCL) is a biocompatible, biodegradable synthetic polymer which in combination with nanohydroxyapatite (nHAp) can give rise to a low cost, nontoxic bioactive product with excellent mechanical properties and slow degradation. Here we produced, characterized and evaluated in vivo the bone formation of PCL/nHAp scaffolds produced by the rotary jet spinning technique. The scaffolds produced were firstly soaked into simulated body fluid for 21 days to also obtain nHAp onto PCL/nHAp scaffolds. Afterwards, the scaffolds were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy and Raman spectroscopy. For in vivo experiments, 20 male Wistar rats were used and randomly divided in 4 experimental groups (n = 5). A critical defect of 3 mm in diameter was made in the tibia of the animals, which were filled with G1 control (clot); G2-PCL scaffold; G3-PCL/nHAp (5%) scaffold; G4-PCL/nHAp (20%) scaffold. All animals were euthanized 60 days after surgery, and the bone repair in the right tibiae were evaluated by radiographic analysis, histological analysis and histomorphometric analysis. While in the left tibias, the areas of bone repair were submitted to the flexural strength test. Radiographic and histomorphometric analyses no showed statistical difference in new bone formation between the groups, but in the three-point flexural tests, the PCL/nHAp (20%) scaffold positively influenced the flexural mode of the neoformed bone. These findings indicate that PCL/nHAp (20%) scaffold improve biomechanical properties of neoformed bone and could be used for bone medicine regenerative.

Electrospraying Oxygen-Generating Microparticles for Tissue Engineering Applications.

BACKGROUND: The facile preparation of oxygen-generating microparticles (M) consisting of Polycaprolactone (PCL), Pluronic F-127, and calcium peroxide (CPO) (PCL-F-CPO-M) fabricated through an electrospraying process is disclosed. The biological study confirmed the positive impact from the oxygen-generating microparticles on the cell growth with high viability. The presented technology could work as a prominent tool for various tissue engineering and biomedical applications. METHODS: The oxygen-generated microparticles fabricated through electrospraying processes were thoroughly characterization through various methods such as X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) analysis, and scanning electron microscopy (SEM)/SEM-Energy Dispersive Spectroscopy (EDS) analysis. RESULTS: The analyses confirmed the presence of the various components and the porous structure of the microparticles. Spherical shape with spongy characteristic microparticles were obtained with negative charge surface (ζ = -16.9) and a size of 17.00 ± 0.34 µm. Furthermore, the biological study performed on rat chondrocytes demonstrated good cell viability and the positive impact of increasing the amount of CPO in the PCL-F-CPO-M. CONCLUSION: This technological platform could work as an important tool for tissue engineering due to the ability of the microparticles to release oxygen in a sustained manner for up to 7 days with high cell viability.

Advances in dual functional antimicrobial and osteoinductive biomaterials for orthopaedic applications.

A vast growing problem in orthopaedic medicine is the increase of clinical cases with antibiotic resistant pathogenic microbes, which is predicted to cause higher mortality than all cancers combined by 2050. Bone infectious diseases limit the healing ability of tissues and increase the risk of future injuries due to pathologic tissue remodelling. The traditional treatment for bone infections has several drawbacks and limitations, such as lengthy antibiotic treatment, extensive surgical interventions, and removal of orthopaedic implants and/or prosthesis, all of these resulting in long-term rehabilitation. This is a huge burden to the public health system resulting in increased healthcare costs. Current technologies e.g. co-delivery systems, where antibacterial and osteoinductive agents are delivered encounter challenges such as site-specific delivery, sustained and prolonged release, and biocompatibility. In this review, these aspects are highlighted to promote the invention of the next generation biomaterials to prevent and/or treat bone infections and promote tissue regeneration.

Bioprinting a Synthetic Smectic Clay for Orthopedic Applications.

Bioprinting technology has emerged as an important approach to bone and cartilage tissue engineering applications, because it allows the printing of scaffolds loaded with various components, such as cells, growth factors, or drugs. In this context, the bone has a very complex architecture containing highly vascularized and calcified tissues, while cartilage is avascular and has low cellularity and few nutrients. Owing to this complexity, the repair and regeneration of these tissues are highly challenging. Identification of the appropriate biomaterial and fabrication technologies can provide sustainable solutions to this challenge. Here, nanosized Laponite® (Laponite is a trademark of the company BYK Additives Ltd.) has shown to be a promising material due to its unique properties such as excellent biocompatibility, facile gel formation, shear-thinning property (reversible physical crosslinking), high specific surface area, degrade into nontoxic products, and with osteoinductive properties. Even though Laponite and Laponite-based composite for 3D bioprinting application are considered as soft gels, they may therefore not be thought exhibiting sufficient mechanical strength for orthopedic applications. However, through the merging with suitable composite and, also by incorporation of crosslinking step, desired mechanical strength for orthopedic application can be obtained. In this review, recent advances and future perspective of bioprinting Laponite and Laponite composites for orthopedic applications are highlighted.

Atomic Layer Deposited TiO2 and Al2O3 Thin Films as Coatings for Aluminum Food Packaging Application.

Titanium dioxide (TiO2) and aluminum oxide (Al2O3) coatings have been investigated in a wide range of bio-applications due to their biodegradation and biocompatibility properties, that are key parameters for their use in the food packaging and biomedical devices fields. The present study evaluates and compares the electrochemical behavior of the non-coated, commercial resin-coated, TiO2-coated and Al2O3-coated aluminum in commercial beer electrolyte. For this, TiO2 and Al2O3 thin films were deposited on aluminum (Al) substrates using atomic layer deposition (ALD). The evaluation of the corrosion barrier layer properties was performed by linear sweep voltammetry (LSV) during 10 min and electrochemical impedance spectroscopy (EIS). In addition, profilometry, grazing incidence X-ray diffractometry (GIXRD), scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FT-IR) analyses were performed to investigate the physical and chemical properties of the pristine and / or corroded samples. TiO2 and Al2O3 films presented an amorphous structure, a morphology that follows Al substrate surface, and a thickness of around 100 nm. Analysis of LSV data showed that ALD coatings promoted a considerable increase in corrosion barrier efficiency being 86.3% for TiO2-coated Al and 80% for Al2O3-coated Al in comparison with 7.1% of commercial resin-coated Al. This is mainly due to the lower electrochemical porosity, 11.4% for TiO2-coated Al and 20.4% for Al2O3-coated Al in comparison with 96% of the resin-coated Al, i.e. an increase of up to twofold in the protection of Al when coated with TiO2 compared to Al2O3. The EIS results allow us to complement the discussions about the reduced corrosion barrier efficiency of the Al2O3 film for beer electrolyte once SEM and FT-IR analyzes did not show drastic changes in both investigated ALD films after the corrosion assays. The above results indicate that ALD TiO2 and Al2O3 films may be a viable alternative to replace the synthetic resin coatings frequently used in aluminum cans of use in the food industry.

In vitro and in vivo evaluation of rotary-jet-spun poly(ɛ-caprolactone) with high loading of nano-hydroxyapatite.

Herein, poly(ɛ-caprolactone) (PCL) mats with different amounts of nanohydroxyapatite (nHAp) were produced using rotary-jet spinning (RJS) and evaluated in vitro and in vivo. The mean fiber diameters of the PCL, PCL/nHAp (3%), PCL/nHAp (5%), and PCL/nHAp (20%) scaffolds were 1847 ± 1039, 1817 ± 1044, 1294 ± 4274, and 845 ± 248 nm, respectively. Initially, all the scaffolds showed superhydrophobic behavior (contact angle around of 140oC), but decreased to 80° after 30 min. All the produced scaffolds were bioactive after soaking in simulated body fluid, especially PCL/nHAp (20%). The crystallinity of the PCL scaffolds decreased progressively from 46 to 21% after incorporation of 20% nHAp. In vitro and in vivo cytotoxicity were investigated, as well as the mats' ability to reduce bacteria biofilm formation. In vitro cellular differentiation was evaluated by measuring alkaline phosphatase activity and mineralized nodule formation. Overall, we identified the total ideal amount of nHAp to incorporate in PCL mats, which did not show in vitro or in vivo cytotoxicity and promoted lamellar bone formation independently of the amounts of nHAp. The scaffolds with nHAp showed reduced bacterial proliferation. Alizarin red staining was higher in materials associated with nHAp than in those without nHAp. Overall, this study demonstrates that PCL with nHAp prepared by RJS merits further evaluation for orthopedic applications.

Electrospun Nanofibrous Poly (Lactic Acid)/Titanium Dioxide Nanocomposite Membranes for Cutaneous Scar Minimization.

Poly (lactic acid) (PLA) has been increasingly used in cutaneous tissue engineering due to its low cost, ease of handling, biodegradability, and biocompatibility, as well as its ability to form composites. However, these polymers possess a structure with nanoporous that mimic the cellular environment. In this study, nanocomposites are prepared using PLA and titanium dioxide (TiO2) (10 and 35%-w/w) nanoparticles that also function as an active anti-scarring agent. The nanocomposites were prepared using an electrospinning technique. Three different solutions were prepared as follows: PLA, 10% PLA/TiO2, and 35% PLA/TiO2 (w/w%). Electrospun PLA and PLA/TiO2 nanocomposites were characterized morphologically, structurally, and chemically using electron scanning microscopy, transmission electron microscopy, goniometry, and X-ray diffraction. L929 fibroblast cells were used for in vitro tests. The cytotoxic effect was evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays. Versicam (VCAN), biglicam (BIG), interleukin-6 (IL6), interleukin-10 (IL-10), and type-1 collagen (COL1A1) genes were evaluated by RT-qPCR. In vivo tests using Wistar rats were conducted for up to 15 days. Nanofibrous fibers were obtained for all groups that did not contain residual solvents. No cytotoxic effects were observed for up to 168 h. The genes expressed showed the highest values of versican and collagen-1 (p < 0.05) for PLA/TiO2 nanocomposite scaffolds when compared to the control group (cells). Histological images showed that PLA at 10 and 35% w/w led to a discrete inflammatory infiltration and expression of many newly formed vessels, indicating increased metabolic activity of this tissue. To summarize, this study supported the potential of PLA/TiO2 nanocomposites ability to reduce cutaneous scarring in scaffolds.

Rotary jet-spun porous microfibers as scaffolds for stem cells delivery to central nervous system injury.

Stem cell transplantation is a promising strategy to treat brain injuries. However, cell-based therapies are limited because poor local cell engraftment. Here, we present a polylactic acid (PLA) scaffold to support mesenchymal stem cells (MSCs) delivery in stroke. We isolated bone marrow MSCs from adult C57/Bl6 mice, cultured them on PLA polymeric rough microfibrous (PRM) scaffolds obtained by rotary jet spinning, and transplanted over the brains of adult C57/Bl6 mice, carrying thermocoagulation-induced cortical stroke. No inflammatory response to PRM was found. MSCs transplantation significantly reduced the area of the lesion and PRM delivery increased MSCs retention at the injury site. In addition, PRM upregulated α6-integrin and CXCL12 production, which may be the cause for greater cell retention at the lesion site and may provide additional benefit to MSCs transplantation procedures. We conclude that PRM scaffolds offer a promising new system to deliver stem cells to injured areas of the brain.

Polypyrrole increases branching and neurite extension by Neuro2A cells on PBAT ultrathin fibers.

We present a methodology for production and application of electrospun hybrid materials containing commercial polyester (poly (butylene adipate-co-terephthalate; PBAT), and a conductive polymer (polypyrrole; PPy) as scaffold for neuronal growth and differentiation. The physical-chemical properties of the scaffolds and optimization of the electrospinning parameters are presented. The electrospun scaffolds are biocompatible and allow proper adhesion and spread of mesenchymal stem cells (MSCs). Fibers produced with PBAT with or without PPy were used as scaffold for Neuro2a mouse neuroblastoma cells adhesion and differentiation. Neuro2a adhered to PBAT and PBAT/PPy2% scaffolds without laminin coating. However, Neuro2a failed to differentiate in PBAT when stimulated by treatment with retinoic acid (RA), but differentiated in PBAT/PPy2% fibers. We hypothesize that PBAT hydrophobicity inhibited proper spreading and further differentiation, and inhibition was overcome by coating the PBAT fibers with laminin. We conclude that fibers produced with the combination of PBAT and PPy can support neuronal differentiation.

Nanohydroxyapatite/Graphene Nanoribbons Nanocomposites Induce in Vitro Osteogenesis and Promote in Vivo Bone Neoformation.

Nanomaterials based on graphene oxide nanoribbons (GNR) and nanohydroxyapatite (nHAp) serve as attractive materials for bone tissue engineering. Herein, we evaluated the potential of nHAp/GNR toward in vitro analysis of specific genes related to osteogenesis and in vivo bone regeneration using animal model. Three different concentrations of nHAp/GNR composites were analyzed in vitro using a cytotoxicity assay, and osteogenic potential was determined by ALP, OPN, OCN, COL1, and RUNX2 genes and alkaline phosphatase assays. In vivo bone neoformation using a well-established in vivo rat tibia defect model was used to confirm the efficiency of the optimized composite. The scaffolds were nontoxic, and the osteogenesis process was dose-dependent (at 200 µg mL-1 of nHAp/GNR) compared to controls. The in vivo results showed higher bone neoformation after 15 days of nHAp/GNR implantation compared to all groups. After 21 days, both nHAp/GNR composites showed better lamellar bone formation compared to control. We attributed this enhanced bone neoformation to the high bioactivity and surface area presented by nHAp/GNR composites, which was systematically evaluated in previous studies. These new in vivo results suggest that nHAp/GNR composites can be exploited for a range of strategies for the improved development of novel dental and orthopedic bone grafts to accelerate bone regeneration.

Electrospun ultrathin PBAT/nHAp fibers influenced the in vitro and in vivo osteogenesis and improved the mechanical properties of neoformed bone.

Combining polyester scaffolds with synthetic nanohydroxyapatite (nHAp), which is bioactive and osteoconductive, is a plausible strategy to improve bone regeneration. Here, we propose the combination of PBAT [poly(butylene-adipate-co-terephthalate)] and synthetic nHAp (at 3 and 5wt%). PBAT is a relatively a new polymer with low crystallinity and attractive biodegradability and mechanical properties for orthopedic applications, however, with a still underexplored potential for in vivo applications. Then, we performed a careful biological in vitro and in vivo set of experiments to evaluate the influence of PBAT containing two different nHAp loads. For in vitro assays, osteoblast-like MG63 cells were used and the bioactivity and gene expression related to osteogenesis were evaluated by qRT-PCR. For in vivo experiments, twenty-four male rats were used and a tibial defect model was applied to insert the scaffolds. Micro-computed tomography (Micro-CT) and histological analysis were used to assess e bone neoformation after 6 weeks of implantation. Three point flexural tests measured the mechanical properties of the neoformed bone. All scaffolds showed promising in vitro properties, since they were not cytotoxic against MG-63 cells and promoted high cell proliferation and formation of mineralized nodules. From a mechanistic point-of-view, nHAp loading increased hydrophilicity, which in turn allowed for a better adsorption of proteins and consequent changes in the phenotypic expression of osteoblasts. nHAp induced better cellular responses on/in the scaffolds, which was mainly attributed to its osteoconductive and osteoinductive properties. Micro-CT images showed that nHAp at 3% and 5wt% led to more effective bone formation, presenting the highest bone volume after 6 weeks of implantation. Considering the three point flexural tests, 5wt% of nHAp positively influenced the flexural mode of the neoformed bone, but the stiffiness was similar between the 3% and 5wt% groups. In summary, this investigation demonstrated great potential for the application of these novel scaffolds towards bone regeneration and, thus, should be further studied.

Graphene oxide/multi-walled carbon nanotubes as nanofeatured scaffolds for the assisted deposition of nanohydroxyapatite: characterization and biological evaluation.

Nanohydroxyapatite (nHAp) is an emergent bioceramic that shows similar chemical and crystallographic properties as the mineral phase present in bone. However, nHAp presents low fracture toughness and tensile strength, limiting its application in bone tissue engineering. Conversely, multi-walled carbon nanotubes (MWCNTs) have been widely used for composite applications due to their excellent mechanical and physicochemical properties, although their hydrophobicity usually impairs some applications. To improve MWCNT wettability, oxygen plasma etching has been applied to promote MWCNT exfoliation and oxidation and to produce graphene oxide (GO) at the end of the tips. Here, we prepared a series of nHAp/MWCNT-GO nanocomposites aimed at producing materials that combine similar bone characteristics (nHAp) with high mechanical strength (MWCNT-GO). After MWCNT production and functionalization to produce MWCNT-GO, ultrasonic irradiation was employed to precipitate nHAp onto the MWCNT-GO scaffolds (at 1-3 wt%). We employed various techniques to characterize the nanocomposites, including transmission electron microscopy (TEM), Raman spectroscopy, thermogravimetry, and gas adsorption (the Brunauer-Emmett-Teller method). We used simulated body fluid to evaluate their bioactivity and human osteoblasts (bone-forming cells) to evaluate cytocompatibility. We also investigated their bactericidal effect against Staphylococcus aureus and Escherichia coli. TEM analysis revealed homogeneous distributions of nHAp crystal grains along the MWCNT-GO surfaces. All nanocomposites were proved to be bioactive, since carbonated nHAp was found after 21 days in simulated body fluid. All nanocomposites showed potential for biomedical applications with no cytotoxicity toward osteoblasts and impressively demonstrated a bactericidal effect without the use of antibiotics. All of the aforementioned properties make these materials very attractive for bone tissue engineering applications, either as a matrix or as a reinforcement material for numerous polymeric nanocomposites.

Magnetic super-hydrophilic carbon nanotubes/graphene oxide composite as nanocarriers of mesenchymal stem cells: Insights into the time and dose dependences.

Among nanostructured materials, multi-walled carbon nanotubes (MWCNT) have demonstrated great potential for biomedical applications in recent years. After oxygen plasma etching, we can obtain super-hydrophilic MWCNT that contain graphene oxide (GO) at their tips. This material exhibits good dispersion in biological systems due to the presence of polar groups and its excellent magnetic properties due to metal particle residues from the catalyst that often remain trapped in its walls and tips. Here, we show for the first time a careful biological investigation using magnetic superhydrophilic MWCNT/GO (GCN composites). The objective of this study was to investigate the application of GCN for the in vitro immobilization of mesenchymal stem cells. Our ultimate goal was to develop a system to deliver mesenchymal stem cells to different tissues and organs. We show here that mesenchymal stem cells were able to internalize GCN with a consequent migration when subjected to a magnetic field. The cytotoxicity of GCN was time- and dose-dependent. We also observed that GCN internalization caused changes in the gene expression of the proteins involved in cell adhesion and migration, such as integrins, laminins, and the chemokine CXCL12, as well as its receptor CXCR4. These results suggest that GCN represents a potential new platform for mesenchymal stem cell immobilization at injury sites.

Influence of low contents of superhydrophilic MWCNT on the properties and cell viability of electrospun poly (butylene adipate-co-terephthalate) fibers.

The use of poly (butylene adipate-co-terephthalate) (PBAT) in tissue engineering, more specifically in bone regeneration, has been underexplored to date due to its poor mechanical resistance. In order to overcome this drawback, this investigation presents an approach into the preparation of electrospun nanocomposite fibers from PBAT and low contents of superhydrophilic multi-walled carbon nanotubes (sMWCNT) (0.1-0.5wt.%) as reinforcing agent. We employed a wide range of characterization techniques to evaluate the properties of the resulting electrospun nanocomposites, including Field Emission Scanning Electronic Microscopy (FE-SEM), Transmission Electronic Microscopy (TEM), tensile tests, contact angle measurements (CA) and biological assays. FE-SEM micrographs showed that while the addition of sMWCNT increased the presence of beads on the electrospun fibers' surfaces, the increase of the neat charge density due to their presence reduced the fibers' average diameter. The tensile test results pointed that sMWCNT acted as reinforcement in the PBAT electrospun matrix, enhancing its tensile strength (from 1.3 to 3.6MPa with addition of 0.5wt.% of sMWCNT) and leading to stiffer materials (lower elongation at break). An evaluation using MG63 cells revealed cell attachment into the biomaterials and that all samples were viable for biomedical applications, once no cytotoxic effect was observed. MG-63 cells osteogenic differentiation, measured by ALP activity, showed that mineralized nodules formation was increased in PBAT/0.5%CNTs when compared to control group (cells). This investigation demonstrated a feasible novel approach for producing electrospun nanocomposites from PBAT and sMWCNT with enhanced mechanical properties and adequate cell viability levels, which allows for a wide range of biomedical applications for these materials.

Bioactivity behaviour of nano-hydroxyapatite/freestanding aligned carbon nanotube oxide composite.

Bioactive and low cytotoxic three dimensional nano-hydroxyapatite (nHAp) and aligned carbon nanotube oxide (a-CNTO) composite has been investigated. First, freestanding aligned carbon nanotubes porous scaffold was prepared by large-scale thermal chemical vapour deposition and functionalized by oxygen plasma treatment, forming a-CNTO. The a-CNTO was covered with plate-like nHAp crystals prepared by in situ electrodeposition techniques, forming nHAp/a-CNTO composite. After that nHAp/a-CNTO composite was immersed in simulated body fluid for composite consolidation. This novel nanobiomaterial promotes mesenchymal stem cell adhesion with the active formation of membrane projections, cell monolayer formation and high cell viability.

Effect of ultrasound irradiation on the production of nHAp/MWCNT nanocomposites.

Large amounts of nanohydroxyapatite (nHAp)-multiwall carbon nanotube (MWCNT) nanocomposites are produced by two different aqueous precipitation methods. The ultrasonic irradiation (UI) and slow-drip addition under continuous magnetic stirring (DMS) methods were used to investigate the precipitation of nHAp acicular crystals. Calcium-nitrate, diammonium hydrogen phosphate, and ammonium hydroxide were used as precursor reagents. Superhydrophilic MWCNT were also employed. XPS analysis evidences that the functionalized MWCNTs are composed of 18 to 20 at.% of oxygen and that this property influences the nHAp formation. The high surface area of the MWCNT decreases the mean free path of ions, favoring the nHAp formation assisted by UI. The crystallinity was evaluated using the Scherrer equation. Semi-qualitative energy dispersive spectroscopy (EDS) analysis showed that the main components of HAp powders were calcium and phosphorus in the ratio Ca/P around of 1.67. Bioactivity properties of the nHAp/MWCNT-UI nanocomposites could be evaluated after 14 days soaking in simulated body fluid medium. Scanning electron microscopy, EDS, Fourier transform infrared attenuated total reflection spectroscopy, and X-ray diffraction techniques proved that the apatites formed on the surface and to points that the nHAp/MWCNT-UI have potential biological applications.