Multiwalled Carbon Nanotube Scaffolds Research Articles

CNT incorporation improves the resolution and stability of porous 3D printed PLGA/HA/CNT scaffolds for bone regeneration

In this study, 3D printed porous poly(lactide-co-glycolide) (PLGA) and its nanocomposites with 5 wt. % hydroxyapatite (HA) and 0.5, 1 and 2 wt. % carboxyl-functionalized multi-walled carbon nanotube (CNT) scaffolds were fabricated by using extrusion-based printing. The printing parameters were optimized by rheological studies. The rheological studies demonstrated shear thinning properties for all compositions and an increase in storage modulus was observed after the addition of CNT. Porous PLGA/HA/CNT scaffolds were printed by applying a pressure of 4.76 bar at 125 °C. The addition of 0.5 wt. % of CNT reduced the strut size and increased the porosity from 42% to 60%. The increase in storage modulus and decrease in strut size were related to hydrogen bonding between CNT, HA and PLGA which ultimately improved shape fidelity. The scaffolds were characterized by analysis of their chemical structure, water contact angle measurement, in vitro bioactivity test, biodegradation test, mechanical analysis, and in vitro cell studies. The scaffolds were found to be more hydrophilic by the incorporation of CNTs. Also, degradation studies showed that the microstructure of the scaffold became more stable with the addition of HA and CNT. The compressive modulus of PLGA/HA/CNT2 scaffold was found to be 548.5 MPa, which is found suitable to replace cancellous bone. The scaffolds were found to be highly biocompatible which is possibly due to alignment of CNT and PLGA during 3D printing process. Alizarin red staining indicated improvement of mineralization of MC3T3-E1 cells on the CNT incorporated porous 3D scaffolds. The results suggest that the produced porous 3D printed PLGA/HA/CNT scaffolds are promising for bone regeneration applications.

Hydrolytic degradation and cytotoxicity of poly(lactic‐co‐glycolic acid)/multiwalled carbon nanotubes for bone regeneration

ABSTRACTBiodegradable poly(l‐lactide‐co‐glycolide) (PLGA)/multiwalled carbon nanotubes (MWCNTs) scaffolds produced by thermally induced phase separation (TIPS) are studied for bone regeneration. Their magnetic properties, cytotoxicity, and in vitro degradation are investigated. Certain properties are analyzed at 37 °C over 16 weeks in phosphate buffer saline (PBS) solution, as a function of degradation time: morphology, mass loss, pH value of PBS, and thermal behavior. The presence of small quantities of nanotubes in the scaffolds, ≤0.5 wt %, leads to a weak magnetic response although the PLGA was diamagnetic. The incorporation of MWCNTs in the scaffolds generated a morphology and a very different process of in vitro degradation than might be expected in a PLGA scaffold. The in vitro degradation process started on week 13 and rapidly advanced, although the structural integrity of the scaffolds was maintained and no collapse of the structure occurred. Cytotoxicity tests on the samples showed cytotoxicity behavior at concentrations of over 0.3 wt % MWCNTs. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48439.

Engineering of electrically-conductive poly(ε-caprolactone)/ multi-walled carbon nanotubes composite nanofibers for tissue engineering applications

In this communication, air jet spinning (AJS)was used to successfully fabricate nanofibers of poly (e-caprolactone)(PCL)onto which Multi-Walled Carbon Nanotubes (MWCNTs)were loaded at 0.5 to 1.0 wt % using a cost-effective fabrication technique. SEM images indicated that the incorporation of MWCNTs resulted in the production of larger fiber sizes with a more uniform size distribution than plain PCL. TEM observation showed the MWCNTs were parallel and oriented along the axes of the nanofibers. Specific interfacial interactions between the PCL and the MWCNTs enhanced the mechanical properties of the nanofibers in terms of tensile modulus and tensile strength. The electrical conductivity improved at the higher (1.0%)MWCNT concentration, alongside improved hydrophilicity, demonstrated through decreases in contact angle measurements. Moreover, in vitro studies with human bone osteosarcoma cells (Saos-2)revealed that MWCNT scaffolds displayed desired cell attachment and spreading. These high performance MWCNT-PCL nanocomposite fiber mats have been demonstrated as good candidates for modern microelectronics and tissue engineering applications.

The Application of Multi-Walled Carbon Nanotubes in Bone Tissue Repair Hybrid Scaffolds and the Effect on Cell Growth In Vitro.

In this study, composite scaffolds with different multi-walled carbon nanotubes (MWCNTs) content were prepared by freeze-drying. These scaffolds were characterized by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), porosity, hydrophilicity, mechanical strength, and degradation. The MWCNTs scaffolds were structurally sound and had porous structures that offered ample space for adherence, proliferation, and differentiation of MC3T3-E1 cells, and also supported the transport of nutrients and metabolic waste. CS/Gel/nHAp/0.3%MWCNTs scaffolds provided the best outcomes in terms of scaffold porosity, hydrophilicity, and degradation rate. However, CS/Gel/nHAp/0.6%MWCNTs scaffolds were found to support the optimal growth, homogenous distribution, and biological activity of MC3T3-E1 cells. The excellent properties of CS/Gel/nHAp/0.6%MWCNTs scaffolds for the adhesion, proliferation, and osteogenesis differentiation of MC3T3-E1 cells in vitro highlights the potential applications of this scaffold in bone tissue regeneration.

3D printing nano conductive multi-walled carbon nanotube scaffolds for nerve regeneration

Objective. Nanomaterials, such as carbon nanotubes (CNTs), have been introduced to modify the surface properties of scaffolds, thus enhancing the interaction between the neural cells and biomaterials. In addition to superior electrical conductivity, CNTs can provide nanoscale structures similar to those present in the natural neural environment. The primary objective of this study is to investigate the proliferative capability and differential potential of neural stem cells (NSCs) seeded on a CNT incorporated scaffold. Approach. Amine functionalized multi-walled carbon nanotubes (MWCNTs) were incorporated with a PEGDA polymer to provide enhanced electrical properties as well as nanofeatures on the surface of the scaffold. A stereolithography 3D printer was employed to fabricate a well-dispersed MWCNT-hydrogel composite neural scaffold with a tunable porous structure. 3D printing allows easy fabrication of complex 3D scaffolds with extremely intricate microarchitectures and controlled porosity. Main results. Our results showed that MWCNT-incorporated scaffolds promoted neural stem cell proliferation and early neuronal differentiation when compared to those scaffolds without the MWCNTs. Furthermore, biphasic pulse stimulation with 500 µA current promoted neuronal maturity quantified through protein expression analysis by quantitative polymerase chain reaction. Significance. Results of this study demonstrated that an electroconductive MWCNT scaffold, coupled with electrical stimulation, may have a synergistic effect on promoting neurite outgrowth for therapeutic application in nerve regeneration.

Biocompatibility of vertically aligned multi-walled carbon nanotube scaffolds for human breast cancer cell line MDA-MB-231

The aim of the current study was to determine whether the MWCNT-based scaffold has a suitable structure for cell growth and provides a biocompatible environment for human MDA-MB-231 cell lines. MWCNT-based nanostructured scaffolds were produced by plasma-enhanced chemical vapor deposition (PECVD) technique. MDA-MB-231 cells were seeded on MWCNTs-textured silicon scaffolds and on pristine silicon surfaces. After 1 week of culturing, the scaffolds were prepared for SEM analysis and immunocytochemical staining was performed for the two groups (MWCNT scaffold and pristine silicon surface), using MMP-2, MMP-9, PI3K, AKT and NF-κB primary antibodies. SEM analyses showed that the MDA-MB-231 cells better adhered to the MWCNT-based nanostructured scaffold than the pristine silicon surface. Immunohistochemical activity of the MDA-MB-231 cells on both materials has similar staining with anti-AKT MMP-2, MMP-9 and NF-κB primary antibodies. Therefore, the results of the present study suggest that the MWCNT-based scaffolds enhanced cell adhesion to the scaffold and exhibited more biomimetic properties and physiological adaptation with the potential to be used for in vitro metastasis studies of BrCa cell lines.

Three‐dimensional carbon nanotube scaffolds for long‐term maintenance and expansion of human mesenchymal stem cells

Expansion of mesenchymal stem cells (MSCs) and maintenance of their self-renewal capacity in vitro requires specialized robust cell culture systems. Conventional approaches using animal-derived or artificial matrices and a cocktail of growth factors have limitations such as consistency, scalability, pathogenicity, and loss of MSC phenotype. Herein, we report the use of all-carbon 3-D single- and multiwalled carbon nanotube scaffolds (SWCNTs and MWCNTs) as artificial matrices for long-term maintenance and expansion of human MSCs. Three-dimensional SWCNT and MWCNT scaffolds were fabricated using a novel radical initiated thermal cross-linking method that covalently cross-links CNTs to form 3-D macroporous all-carbon architectures. Adipose-derived human MSCs showed good cell viability, attachment, proliferation, and infiltration in MWCNT and SWCNT scaffolds comparable to poly(lactic-co-glycolic) acid (PLGA) scaffolds (baseline control). ADSCs retained stem cell phenotype after 30 days and satisfied the International Society for Cellular Therapy's (ISCT) minimal criteria for MSCs. Post expansion, (1) ADSCs showed in vitro adherence to tissue culture polystyrene (TCPS); (2) MSC surface antigen expression [CD14(-), CD19(-), CD34(-), CD45(-), CD73(+), CD90(+), CD105(+)]; and (3) trilineage differentiation into osteoblasts, adipocytes, and chondrocytes. Results show that cross-linked 3-D MWCNTs and SWCNTs scaffolds are suitable for ex vivo expansion and maintenance of MSCs for therapeutic applications. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1927-1939, 2017.

Evaluation of nanoparticles of hydroxyapatite and MWCNT’s in scaffolds of poly lactic acid

In the tissue engineering, the cytotoxicity test is an important part of the biomaterials performance. This research reports the production and characterization of polylactic acid (PLA)-supported hydroxyapatite (HA) and multiwalled carbon nanotubes (MWCNT) scaffolds as a bone graft material. Samples containing different HA/MWCNT wt% ratios were prepared by electrospinning. The obtained samples displayed valuable characteristics for the cell adhesion because of their porous-spongy bone-like morphology. The Fourier transforms infrared and Raman analyses indicated no chemical interaction of HA and MWCNT with PLA molecules, but they appear to be only embedded into the PLA fibers. As indicated by x-ray diffraction, crystalline HA and MWCNT’s are supported in the amorphous PLA fibers. Under tensile stress, scaffolds display a Young’s Modulus about 86 MPa, whilst the scaffolds resistance increases with the HA-MWCNT’s ratio. However, the MTS in-vitro assays using the hFOB 1.19 (ATCC CRL-11372) cells, for cell exposure time of 24 and 48 h, revealed that viability reduces for HA-MWCNT’s ratio values over 25 wt%. Our results suggest that a maximum HA/MWCNT’s ratio of 19:1 could be acceptable for cell proliferation while maintaining HA at 200 mg.

Iron polyphthalocyanine sheathed multiwalled carbon nanotubes: A high-performance electrocatalyst for oxygen reduction reaction

The past decade has witnessed a rapid surge of interest in the research and development of non-precious metal-based electrocatalysts for the oxygen reduction reaction (ORR). Until now, the best catalysts in acidic electrolytes have exclusively been Fe-N-C-type materials from high-temperature pyrolysis. Despite the ORR activities of metal phthalocyanine or porphyrin macrocycles having long been known, their durability remains poor. In this work, we use these macrocycles as a basis to develop a novel organic-carbon hybrid material from in-situ polymerization of iron phthalocyanine on conductive multiwalled carbon nanotube scaffolds using a low-temperature microwave heating method. At an optimal polymerto- carbon ratio, the hybrid electrocatalyst exhibits excellent ORR activity with a positive half-wave potential (0.80 V), large mass activity (up to 18.0 A/g at 0.80 V), and a low peroxide yield (<3%). In addition, strong electronic coupling between the polymer and carbon nanotubes is believed to suppress demetallization of the macrocycles, significantly improving cycling stability in acids. Our study represents a rare example of non-precious metal-based electrocatalysts prepared without high-temperature pyrolysis, while having ORR activity in acidic media with potential for practical applications.

Aligned carbon nanotube containing scaffolds for neural tissue regeneration.

Neuropathologies include the deterioration and damage of the nervous system, especially neurons present in the brain, spinal cord and peripheral nervous system. Damage or alternations in neurons makes their structure and functionality abnormal. Every year over 90,000 people get affected by neurodegenerative diseases in the USA. Among all the neurological pathologies, the spinal cord injuries alone influence 10,000 people in the USA every year. Millions of cases of neurodegenerative pathologies are registered worldwide. Without proper treatment and cure to these cases, the toll for patients suffering from neurode-generative disease is expected to reach at least 12 million in the USA 30 years from now (John, 2015).

Development of Chitosan/Poly(L-Lactide)/Multiwalled Carbon Nanotubes Scaffolds for Bone Tissue Engineering

This work focuses to improve the mechanical properties and investigates the growth of osteoblasts on a degradable chitosan/poly(L-lactide)/carbon nanotubes composite for tissue engineering. The morphological and mechanical properties characterizations were performed using scanning electronic microscopy (SEM) and rheometrics analysis system (RSA). Osteoblasts differentiation was determined by alkaline phosphatase activity, total number cells by an Alamar Blue assay, cell attachment and proliferation were visualized qualitatively using SEM, mineralization was characterized by transformed infrared spectroscopy, energy dispersive spectroscopy, and X-ray diffraction. The results suggest that the chitosan/poly(L-lactide)/multiwalled carbon nanotubes composites exhibit the ability to promote cell adhesion, proliferation, and differentiation on their surface.

Bacteriophage-nanocomposites: An easy and reproducible method for the construction, handling, storage and transport of conjugates for deployment of bacteriophages active against Pseudomonas aeruginosa

The purpose of this work was proof of concept to develop a novel, cost effective protocol for the binding of bacteriophages to a surface without loss of function, after storage in various media. The technology platform involved covalently bonding bacteriophage 13 (a Pseudomonas aeruginosa bacteriophage) to two magnetised multiwalled carbon nanotube scaffolds using a series of buffers; bacteriophage–nanotube (B–N) conjugates were efficacious after storage at 20°C for six weeks. B–N conjugates were added to human cell culture in vitro for 9days without causing necrosis and apoptosis. B–N conjugates were frozen (−20°C) in cell culture media for several weeks, after which recovery from the human cell culture medium was possible using a simple magnetic separation technique. The retention of viral infective potential was demonstrated by subsequent spread plating onto lawns of susceptible P. aeruginosa. Analysis of the human cell culture medium revealed the production of interleukins by the human fibroblasts upon exposure to the bacteriophage. One day after exposure, IL-8 levels transitorily increased between 60 and 100pg/mL, but this level was not found on any subsequent days, suggesting an initial but not long lasting response. This paper outlines the development of a method to deliver antimicrobial activity to a surface that is small enough to be combined with other materials. To our knowledge at time of publication, this is the first report of magnetically coupled bacteriophages specific to human pathogens which can be recovered from test systems, and could represent a novel means to conditionally deploy antibacterial agents into living eukaryotic systems without the risks of some antibiotic therapies.

Proposed model for biomineralization of novel nanohydroxyapatite/vertically aligned multiwalled carbon nanotube scaffolds

For the first time, the growth mechanism of biominerals formed on plate-like nanohydroxyapatite (nHAp) electrodeposited on superhydrophilic vertically aligned multi-walled carbon nanotubes (VAMWCNT-O2) is presented and a model for the specific growth preference is discussed. VAMWCNT-O2 films were obtained by microwave-assisted chemical vapor deposition method and funcionalized by oxygen plasma. nHAp/VAMWCNT-O2 nanocomposites were fabricated with a direct electrodeposition of the thin nHAp films onto the VAMWCNT-O2 films. The biomineralized "scaffolds" were obtained by soaking nHAp/VAMWCNT-O2 in simulated body fluid for 7, 14 and 21 days. Results show that the carboxyl functional groups directly attached onto VAMWCNT tips after oxygen plasma treatment were essential for the acceleration of the OH- formation and the deposition of plate-like nHAp crystals.

Calcification in vitro of biomineralizated nanohydroxyapatite/superydrophilic vertically aligned multiwalled carbon nanotube scaffolds

. The MWCNTs are of particular interest for regenerative medicine due to their biocompatibility that permits extensive cell adhesion, spreading, and growth. MWCNT has been shown to support the growth of osteoblast cells by stimulating ECM production in bone tissue formation and growth of hydroxyapatite crystals

Efficient method to produce biomineralizated nanohydroxyapatite/vertically aligned multiwalled carbon nanotube scaffolds

In this paper, we introduce a new biomimetic mineralization method employing nanohydroxyapatite/superhydrophilic vertically aligned multiwalled carbon nanotube (HA/VAMWCNT) nanocomposites as highly stable template materials. The biomineralization was obtained after HA/VAMWCNT nanocomposites were soaked in simulated body fluid (SBF) solution. Structural analysis revealed that the polycrystalline biological apatites were formed due to the high crystallinity of the produced nanohydroxyapatite (HA). These new nanocomposites are a very promising nanobiomaterial due to their excellent calcification in vitro process.

Photosensitization of multiwalled carbon nanotube scaffolds with ZnO quantum dots for photovoltaic applications

In this article, we have decorated multiwalled carbon nanotubes (MWCNTs) scaffold with ZnO quantum dots (QDs, size in the range of 2.9–4.5 nm) and investigated their prospects for photovoltaic applications. ZnO QDs, in the present study, work as photosensitizer instead of electron transporting media as used in recent conventional strategic solar cells. ZnO QDs/MWCNTs composite shows an increased visible absorbance and quenching of the broad visible emission at around ~560 nm, while only ZnO QDs exhibit a strong visible emission. An efficient electron–hole separation facilitates an increase in the short-circuit current. These results show a possibility of developing a nontoxic, ZnO QDs sensitized MWCNTs composite-based photovoltaic solar cell.

OPTIMIZATION OF THE MECHANICAL STRENGTH PROPERTIES OF POLY(L-LACTIDE)/MULTI-WALLED CARBON NANOTUBE SCAFFOLDS USING RESPONSE SURFACE METHODOLOGY

In this study the response surface methodology (RSM) coupled with the central composite design (CCD) were used to optimize the mechanical strength properties of poly(L-lactide)/multi-walled carbon nanotube (MWCNT) scaffolds. The scaffolds were prepared by the freeze-extraction method. MWCNTs were incorporated into PLLA composite as a reinforcement agent in order to improve the strength properties of the scaffolds. The effect of process parameters such as ratio of PLLA/(PLLA + MWCNT) (93–100%), solvent amount (100–200 ml), freezing time (5–7 h) and immersing time (2–4 days) were studied using the design of experiment (DOE). Based on CCD, quadratic model was obtained and developed to correlate the process parameters to the strength of the scaffolds. An analysis of variance (ANOVA) was applied to determine the significant factors affecting the experimental design response (strength) of the scaffolds. The predicted values after optimization process were in good agreement with the experimental values. The model was able to accurately predict the response of strength with less than 5% error.

Cytocompatibility studies of vertically-aligned multi-walled carbon nanotubes: Raw material and functionalized by oxygen plasma

It was presented a strong difference on cell adhesion and proliferation of functionalized vertically-aligned multi-walled carbon nanotube (VACNT) scaffolds compared to raw-VACNT. Biocompatibility in vitro tests were performed on raw-VACNT after superficial modification by oxygen plasma, which changes its superhydrophobic character to superhydrophilic. Two cytocompatibility tests were applied: 1) total lactate dehydrogenase colorimetric assay for the study of proliferating cells; and 2) cellular adhesion by scanning electron microscopy. Results showed that superhydrophilic VACNT scaffolds stimulate cell growth with proliferation up to 70% higher than normal growth of cell culture.

Monolayer formation of human osteoblastic cells on vertically aligned multiwalled carbon nanotube scaffolds

Monolayer formation of SaOS-2 (human osteoblast-like cells) was observed on VACNT (vertically aligned multiwalled carbon nanotubes) scaffolds without purification or functionalization. The VACNT were produced by a microwave plasma chemical vapour deposition on titanium surfaces with nickel or iron as catalyst. Cell viability and morphology studies were evaluated by LDH (lactate dehydrogenase) release assay and SEM (scanning electron microscopy), respectively. The non-toxicity and the flat spreading with monolayer formation of the SaOs-2 on VACNT scaffolds surface indicate that they can be used for biomedical applications.

Cytotoxicity analysis of vertically aligned multi-walled carbon nanotubes by colorimetric assays

A new methodology to evaluate the acute cytotoxicity of vertically aligned multi-walled carbon nanotube (VACNT) scaffolds was presented. A comparison between three different colorimetric assays was performed: (i) lactate dehydrogenase, (ii) 2-(4,5-dimethyl-2-thiazolyl)-3,5-diphenyl-2H-tetrazolium bromide, and (iii) neutral red. The results confirmed that a simple removing of VACNT scaffolds from the cell culture before the colorimetric assays, is necessary to obtain a high level of cell viability.