ARC Research Hub for Graphene Enabled Industry Transformation publications

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3D bioprinting of a cell-laden antibacterial polysaccharide hydrogel composite
(Elsevier, 2021) Rastin, H.; Ramezanpour, M.; Hassan, K.; Mazinani, A.; Tung, T.T.; Vreugde, S.; Losic, D.
Bioink with inherent antibacterial activity is of particular interest for tissue engineering application due to the growing number of bacterial infections associated with impaired wound healing or bone implants. However, the development of cell-laden bioink with potent antibacterial activity while supporting tissue regeneration proved to be challenging. Here, we introduced a cell-laden antibacterial bioink based on Methylcellulose/Alginate (MC/ Alg) hydrogel for skin tissue engineering via elimination of the risks associated with a bacterial infection. The key feature of the bioink is the use of gallium (Ga+3) in the design of bioink formulation with dual functions. First, Ga+3 stabilized the hydrogel bioink by the formation of ionic crosslinking with Alg chains. Second, the gallium- crosslinked bioink exhibited potent antibacterial activity toward both Gram-positive (Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa) bacteria with a bactericidal rate of 99.99 %. In addition, it was found that the developed bioink supported encapsulated fibroblast cellular functions.
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3D bioprinting of cell-laden electroconductive MXene nanocomposite bioinks
(Royal Society of Chemistry, 2020) Rastin, H.; Zhang, B.; Mazinani, A.; Hassan, K.; Bi, J.; Tung, T.T.; Losic, D.
MXenes, a new family of burgeoning two-dimensional (2D) transition metal carbides/nitrides, have been extensively explored in recent years owing to their outstanding properties such as a large specific surface area, high electrical conductivity, low toxicity, and biodegradability. Numerous efforts have been devoted to exploring MXenes for various biomedical applications such as cancer therapy, bioimaging, biosensing, and drug delivery. However, the potential application of MXene nanosheets in tissue engineering has been almost overlooked despite their excellent performance in other biomedical applications. The overarching goal of this paper is to demonstrate the potential of MXene cell-laden bioinks for tissue engineering and their ability to assemble functional scaffolds to regenerate damaged tissue via 3D bioprinting. We formulate a new electroconductive cell-laden bioink composed of Ti3C2 MXene nanosheets dispersed homogeneously within hyaluronic acid/alginate (HA/Alg) hydrogels and showed its performance for extrusion-based 3D bioprinting. The prepared hydrogel bioinks with MXenes display excellent rheological properties, which allows the fabrication of multilayered 3D structures with high resolution and shape retention. Moreover, the introduction of Ti3C2 MXene nanosheets within the HA/Alg hydrogel introduces electrical conductivity to the ink, addressing the poor electrical conductivity of the current bioinks that mismatch with the physico-chemical properties of tissue. In addition, the MXene nanocomposite ink with encapsulated Human Embryonic Kidney 293 (HEK-293) cells displayed high cell viability (>95%) in both bulk hydrogel and 3D bioprinted structures. These results suggest that MXene nanocomposite bioinks and their 3D bioprinting with high electrical conductivity, biocompatibility and degradability can synergize some new applications for tissue and neural engineering.
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3D bioprinting of methylcellulose/gelatin-methacryloyl (MC/GelMA) bioink with high shape integrity
(American Chemical Society; ACS Publications, 2020) Rastin, H.; Ormsby, R.T.; Atkins, G.J.; Losic, D.
The advent of three-dimensional (3D) bioprinting offers a feasible approach to construct complex structures suitable for tissue regeneration, during which cell-laden materials are dispensed on a substrate according to a predesigned structure. However, the lack of ideal printable bioinks with high shape fidelity and improved biological stability remains a major challenge. In this study, methylcellulose/gelatin-methacryloyl (MC/GelMA) bioink with high shape integrity is presented, which takes advantage of the printability of MC and the permanent photo-cross-linking of GelMA under UV irradiation. Although MC demonstrates good printability at room temperature, the lack of cross-linking ability causes distortion and finally dissociation of printed MC in biological media within a few days. However, UV-cross-linked MC/GelMA bioink remains stable in biological media over a period of several months. The shape integrity of MC/GelMA was systematically characterized in terms of yield stress and complex modulus. Unlike pure MC ink, the MC/GelMA ink demonstrated self-supporting behavior once printed due to the higher complex modulus and yield stress induced by GelMA in the system. Shape integrity of MC/GelMA ink resulted in higher resolution and printability which are evaluated by the successful printing of various 1D, 2D, and 3D constructs. Moreover, human primary osteoblasts encapsulated within the MC/GelMA hydrogel show cell viability of >95%. Overall, this work introduces MC/GelMA bioink with high shape integrity and improved biological stability and highlights the importance of rheological properties and post-cross-linking for fabrication of physiologically scaled tissue implants.
Open Access
3D printable electrically conductive hydrogel scaffolds for biomedical applications: a review
(MDPI, 2021) Athukorala, S.S.; Tran, T.S.; Balu, R.; Truong, V.K.; Chapman, J.; Dutta, N.K.; Roy Choudhury, N.
Electrically conductive hydrogels (ECHs), an emerging class of biomaterials, have garnered tremendous attention due to their potential for a wide variety of biomedical applications, from tissue-engineered scaffolds to smart bioelectronics. Along with the development of new hydrogel systems, 3D printing of such ECHs is one of the most advanced approaches towards rapid fabrication of future biomedical implants and devices with versatile designs and tuneable functionalities. In this review, an overview of the state-of-the-art 3D printed ECHs comprising conductive polymers (polythiophene, polyaniline and polypyrrole) and/or conductive fillers (graphene, MXenes and liquid metals) is provided, with an insight into mechanisms of electrical conductivity and design considerations for tuneable physiochemical properties and biocompatibility. Recent advances in the formulation of 3D printable bioinks and their practical applications are discussed; current challenges and limitations of 3D printing of ECHs are identified; new 3D printing-based hybrid methods for selective deposition and fabrication of controlled nanostructures are highlighted; and finally, future directions are proposed.
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3D printing interface-modified PDMS/MXene nanocomposites for stretchable conductors
(Elsevier, 2022) Aakyiir, M.; Tanner, B.; Yap, P.L.; Rastin, H.; Tung, T.T.; Losic, D.; Meng, Q.; Ma, J.
Additive manufacturing has rapidly evolved over recent years with the advent of polymer inks and those inks containing novel nanomaterials. The compatibility of polymer inks with nanomaterial inks remains a great challenge. Simple yet effective methods for interface improvement are highly sought-after to significantly enhance the functional and mechanical properties of printed polymer nanocomposites. In this study, we developed and modified a Ti3C2 MXene ink with a siloxane surfactant to provide compatibility with a polydimethylsiloxane (PDMS) matrix. The rheology of all the inks was investigated with parameters such as complex modulus and viscosity, confirming a self-supporting ink behaviour, whilst Fourier-transform infrared spectroscopy exposed the inks’ reaction mechanisms. The modified MXene nanosheets have displayed strong interactions with PDMS over a wide strain amplitude. An electrical conductivity of 6.14 × 10⁻² S cm⁻¹ was recorded for a stretchable nanocomposite conductor containing the modified MXene ink. The nanocomposite revealed a nearly linear stress-strain relationship and a maximum stress of 0.25 MPa. Within 5% strain, the relative resistance change remained below 35% for up to 100 cycles, suggesting high flexibility, conductivity and mechanical resilience. This study creates a pathway for 3D printing conductive polymer/nanomaterial inks for multifunctional applications such as stretchable electronics and sensors.
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3D printing of cell-laden electroconductive bioink for tissue engineering application
(Royal Society of Chemistry, 2020) Tung, T.T.; Rastin, H.; Zhang, B.; Bi, J.; Hassan, K.; Losic, D.
Bioprinting is an emerging powerful fabrication method, which enables the rapid assembly of 3D bioconstructs with dispensing cell-laden bioinks in pre-designed locations. However, to translate this technology into real applications, there are still a number of challenges that need to be addressed. First, the current inks are generally composed of polymeric materials with poor electrical conductivity that mismatches with the native tissue environment. The second challenge associated with the 3D bioprinting of hydrogel-based bioinks is the fabrication of anatomical-size constructs without any loss of shape fidelity and resolution. To address these challenges, in this work, we introduced a biocompatible bioink associated with current 3D bioprinting by combining methylcellulose and kappa-carrageenan (MC/κCA) hydrogels with poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) conducting polymers. The prepared ink exhibited highly thixotropic behaviour, which could be tuned via changing the concentration of MC and κCA to obtain easy printing with high shape fidelity. The ink was able to fabricate physiological-scale constructs without requiring a secondary support bath. In addition, varying the concentration of PEDOT:PSS could control the electrical conductivity of the ink. Moreover, the encapsulated human embryonic kidney 293 (HEK-293) cells in bulk hydrogels and 3D bioprinted structures maintained high cell viability (>96%) over a week, confirming the in vitro biocompatibility of the ink. Overall, these findings indicate that the MC/κCA/PEDOT:PSS bioink can be promising in biomedical applications, which improved the electroconductivity of bioinks and can exploit the advantage of conductive polymers in the 3D bioprinting technology.
Open Access
A facile synthesis procedure for sulfonated aniline oligomers with distinct microstructures
(MDPI, 2018) Karunagaran, R.; Coghlan, C.; Tran, D.; Tung, T.T.; Burgun, A.; Doonan, C.; Losic, D.
Well-defined sulfonated aniline oligomer (SAO) microstructures with rod and flake morphologies were successfully synthesized using an aniline and oxidant with a molar ratio of 10:1 in ethanol and acidic conditions (pH 4.8). The synthesized oligomers showed excellent dispersibility and assembled as well-defined structures in contrast to the shapeless aggregated material produced in a water medium. The synergistic effects among the monomer concentration, oxidant concentration, pH, and reaction medium are shown to be controlling parameters to generate SAO microstructures with distinct morphologies, whether micro sheets or micro rods.
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A new method for preparation of functionalized graphene and its epoxy nanocomposites
(Elsevier, 2020) Naeem, M.; Kuan, H.C.; Michelmore, A.; Meng, Q.; Qiu, A.; Aakyiir, M.; Losic, D.; Zhu, S.; Ma, J.
Organic solvents are often used to prepare epoxy/graphene nanocomposites. In this study a graphene precursor is developed, which in epoxy at 200 °C is able to directly exfoliate into three classes of graphene platelets: large, single-layer sheets, medium sized sheets with 5.2 ± 1.95 nm in thickness, and smaller 0.5–1.0 nm thick sheets of 200–500 nm in lateral dimension, with a Raman ID/IG ratio of 0.177. The yield of single-layer graphene is 41.45%. Due to oxygen-containing groups on the surface, these sheets are named functionalized graphene platelets. Platelet films of ~10 μm in thickness have an electrical conductivity of 978.65 ± 79.44 S/cm. A percolation threshold of electrical conductivity is observed at 0.80 vol% for epoxy/graphene nanocomposites. The composites show highly improved mechanical and dynamic thermo-mechanical properties. At 1.03 vol%, the nanocomposite has a fracture energy release rate of 850.78 ± 58.00 J m−2 corresponding to an increase of 170.61% over neat epoxy.
Open Access
A novel fabrication approach for multifunctional graphene-based thin film nano-composite membranes with enhanced desalination and antibacterial characteristics
(Springer Nature, 2017) Hegab, H.; Elmekawy, A.; Barclay, T.; Michelmore, A.; Zou, L.; Losic, D.; Saint, C.; Ginic-Markovic, M.
A practical fabrication technique is presented to tackle the trade-off between the water flux and salt rejection of thin film composite (TFC) reverse osmosis (RO) membranes through controlled creation of a thinner active selective polyamide (PA) layer. The new thin film nano-composite (TFNC) RO membranes were synthesized with multifunctional poly tannic acid-functionalized graphene oxide nanosheets (pTA-f-GO) embedded in its PA thin active layer, which is produced through interfacial polymerization. The incorporation of pTA-f-GOL into the fabricated TFNC membranes resulted in a thinner PA layer with lower roughness and higher hydrophilicity compared to pristine membrane. These properties enhanced both the membrane water flux (improved by 40%) and salt rejection (increased by 8%) of the TFNC membrane. Furthermore, the incorporation of biocidal pTA-f-GO nanosheets into the PA active layer contributed to improving the antibacterial properties by 80%, compared to pristine membrane. The fabrication of the pTA-f-GO nanosheets embedded in the PA layer presented in this study is a very practical, scalable and generic process that can potentially be applied in different types of separation membranes resulting in less energy consumption, increased cost-efficiency and improved performance.
Open Access
A unique 3D nitrogen-doped carbon composite as high-performance oxygen reduction catalyst
(MDPI AG, 2017) Karunagaran, R.; Tung, T.; Shearer, C.; Tran, D.; Coghlan, C.; Doonan, C.; Losic, D.
The synthesis and properties of an oxygen reduction catalyst based on a unique 3-dimensional (3D) nitrogen doped (N-doped) carbon composite are described. The composite material is synthesised via a two-step hydrothermal and pyrolysis method using bio-source low-cost materials of galactose and melamine. Firstly, the use of iron salts and galactose to hydrothermally produceiron oxide (Fe₂O₃) magnetic nanoparticle clusters embedded carbon spheres. Secondly, magnetic nanoparticles diffused out of the carbon sphere when pyrolysed in the presence of melamine as nitrogen precursor. Interestingly, many of these nanoparticles, as catalyst-grown carbon nanotubes (CNTs), resulted in the formation of N-doped CNTs and N-doped carbon spheres under the decomposition of carbon and a nitrogen environment. The composite material consists of integrated N-doped carbon microspheres and CNTs show high ORR activity through a predominantly four-electron pathway.
Open Access
A unique synthesis of macroporous N-doped carbon composite catalyst for oxygen reduction reaction
(MDPI, 2021) Karunagaran, R.; Tran, D.; Tung, T.T.; Shearer, C.; Losic, D.
Macroporous carbon materials (MCMs) are used extensively for many electrocatalytic applications, particularly as catalysts for oxygen reduction reactions (ORRs)—for example, in fuel cells. However, complex processes are currently required for synthesis of MCMs. We present a rapid and facile synthetic approach to produce tailored MCMs efficiently via pyrolysis of sulfonated aniline oligomers (SAOs). Thermal decomposition of SAO releases SO2 gas which acts as a blowing agent to form the macroporous structures. This process was used to synthesise three specifically tailored nitrogen (N)-doped MCM catalysts: N-SAO, N-SAO (phenol formaldehyde) (PF) and N-SAO-reduced graphene oxide (rGO). Analysis using Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and X-ray diffraction (XRD) analysis confirmed the formation of macropores (100–350 µm). Investigation of ORR efficacy showed that N-SAOPF performed with the highest onset potential of 0.98 V (vs. RHE) and N-SAOrGO showed the highest limiting current density of 7.89 mAcm−2. The macroporous structure and ORR efficacy of the MCM catalysts synthesised using this novel process suggest that this method can be used to streamline MCM production while enabling the formation of composite materials that can be tailored for greater efficiency in many applications.
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Activation of natural halloysite nanotubes by introducing lanthanum oxycarbonate nanoparticles: Via co-calcination for outstanding phosphate removal
(Royal Society of Chemistry, 2019) Wei, Y.; Yuan, P.; Liu, D.; Losic, D.; Tan, D.; Chen, F.; Liu, H.; Zhou, J.; Du, P.; Song, Y.
Halloysite nanotubes were activated via co-calcination of halloysite and the precursors of lanthanum oxycarbonate (LO), generating reactive alumina nanoparticles and uniformly anchoring LO nanoparticles to halloysite surfaces. The resulting LO-alumina combination exhibits record-high phosphate adsorption capacity as well as excellence in adsorption selectivity and sewage phosphate removal.
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Addressing challenges in providing a reliable ecotoxicology data for graphene-oxide (GO) using an algae (Raphidocelis subcapitata), and the trophic transfer consequence of GO-algae aggregates
(Elsevier, 2019) Markovic, M.; Andelkovic, I.; Shuster, J.; Janik, L.; Kumar, A.; Losic, D.; McLaughlin, M.J.
The graphene oxide (GO) due to its exceptional structure, physicochemical and mechanical properties is a very attractive material for industry application. Even though, the unique properties of GO (e.g. structure, size, shape, etc.) make the risk assessment of this nanomaterial very challenging in comparison with conventional ecotoxicology studies required by regulators. Thus, there is a need for standardized characterization techniques and methodology to secure a high quality/reliable data on the ecotoxicology of GO, and to establish environmentally acceptable levels. Herein, authors address the crucial quality criteria when evaluating the ecotoxicology of GO using an algae (Raphidocelis subcapitata) and a shrimp (Paratya australiensis). This study provides a detail characterization and modification of the used GO, robust quantification and a suspension stability in different media for ecotoxicology studies. It was observed that under the same exposure conditions the behavior of GO and the estimated outcomes (IC50 values) in modified algae media differed in comparison to the referent media. Further to that, the adverse effects of GO on the algae cell structure and the potential uptake of GO by the algae cells were examined using the TEM with different staining techniques to avoid artefacts. Shrimps which were exposed to GO-algae aggregates via the food intake did not indicate stress or accumulation of GO. Our work presents an important insight to necessity of establishing a benchmark ecotoxicology assays for GO (e.g. characterization techniques, choice of media, etc.) and providing a reliable data to be used by regulators in risk assessment of two-dimensional (2D) nanomaterials.
Open Access
Advancing dielectric and ferroelectric properties of piezoelectric polymers by combining graphene and ferroelectric ceramic additives for energy storage applications
(MDPI, 2018) Ishaq, S.; Kanwal, F.; Atiq, S.; Moussa, M.; Azhar, U.; Imran, M.; Losic, D.
To address the limitations of piezoelectric polymers which have a low dielectric constant andto improve their dielectric and ferroelectric efficiency for energy storage applications, we designed and characterized a new hybrid composite that contains polyvinylidene fluoride as a dielectric polymer matrix combined with graphene platelets as a conductive and barium titanite as ceramic ferroelectric fillers. Different graphene/barium titanate/polyvinylidene fluoride nanocomposite films were synthesized by changing the concentration of graphene and barium titanate to explore the impact of each component and their potential synergetic effect on dielectric and ferroelectric properties of the composite. Results showed that with an increase in the barium titanate fraction, dielectric efficiency ofthe nanocomposite was improved. Among all synthesized nanocomposite films, graphene/barium titanate/polyvinylidene fluoride nanocomposite in the weight ratio of 0.15:0.5:1 exhibited thehighest dielectric constant of 199 at 40 Hz, i.e., 15 fold greater than that of neat polyvinylidene fluoride film at the same frequency, and possessed a low loss tangent of 0.6. However, AC conductivity and ferroelectric properties of graphene/barium titanate/polyvinylidene fluoride nanocomposite films were enhanced with an increase in the graphene weight fraction. Graphene/barium titanate/polyvinylidene fluoride nanocomposite films with a weight ratio of 0.2:0.1:1 possessed a high AC conductivity of 1.2 × 10-4 S/m at 40 Hz. While remanent polarization, coercive field, and loop area of the same sample were 0.9 μC/cm², 9.78 kV/cm, and 24.5 μC/cm²·V, respectively. Our results showed that a combination of graphene and ferroelectric ceramic additives are an excellent approach to significantly advance the performance of dielectric and ferroelectric properties of piezoelectric polymers for broad applications including energy storage.
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Advancing of 3D-Printed Titanium Implants with Combined Antibacterial Protection Using Ultrasharp Nanostructured Surface and Gallium-Releasing Agents
(American Chemical Society, 2022) Maher, S.; Linklater, D.; Rastin, H.; Liao, S.T.-Y.; Martins de Sousa, K.; Lima-Marques, L.; Kingshott, P.; Thissen, H.; Ivanova, E.P.; Losic, D.
This paper presents the development of advanced Ti implants with enhanced antibacterial activity. The implants were engineered using additive manufacturing three-dimensional (3D) printing technology followed by surface modification with electrochemical anodization and hydrothermal etching, to create unique hierarchical micro/nanosurface topographies of microspheres covered with sharp nanopillars that can mechanically kill bacteria in contact with the surface. To achieve enhanced antibacterial performance, fabricated Ti implant models were loaded with gallium nitrate as an antibacterial agent. The antibacterial efficacy of the fabricated substrates with the combined action of sharp nanopillars and locally releasing gallium ions (Ga3+) was evaluated toward Staphylococcus aureus and Pseudomonas aeruginosa. Results confirm the significant antibacterial performance of Ga3+-loaded substrates with a 100% eradication of bacteria. The nanopillars significantly reduced bacterial attachment and prevented biofilm formation while also killing any bacteria remaining on the surface. Furthermore, 3Dprinted surfaces with microspheres of diameter 5−30 μm and interspaces of 12−35 μm favored the attachment of osteoblast-like MG-63 cells, as confirmed via the assessment of their attachment, proliferation, and viability. This study provides important progress toward engineering of next-generation 3D-printed implants, that combine surface chemistry and structure to achieve a highly efficacious antibacterial surface with dual cytocompatibility to overcome the limitations of conventional Ti implants.
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All-in-one bioinspired multifunctional graphene biopolymer foam for simultaneous removal of multiple water pollutants
(Wiley-VCH GmbH, 2020) Yap, P.L.; Hassan, K.; Auyoong, Y.L.; Mansouri, N.; Farivar, F.; Tran, D.N.H.; Losic, D.
Polluted waters are complex systems with many different co‐existing contaminants that make their simultaneous removal a very challenging task. To address this problem, all‐in‐one ad/ab‐sorbent with unique combination of interfacial properties and multiple surface chemistry is developed to simultaneously and efficiently remove several pollutants including heavy metals, dyes, oils, and organic solvents. By mimicking the wetting micro‐topology of a darkling beetle with a combined hydrophilic‐hydrophobic surface, a new bioinspired adsorbent, graphene biopolymer foam (Alg‐Fe3O4‐rGO‐4S) for removal of multiple water pollutants is engineered by combining alginate (Alg) and reduced graphene oxide (rGO) functionalized with tetrathiol that is also decorated with iron oxide nanoparticles (Fe3O4). This concept is first proved by single pollutant removal, showing adsorption capacity of 789.7 ± 36 mg/g for methylene blue (MB), 107.0 ± 2.1 mg/g for Hg (II), 73.5 ± 0.7 mg/g for Cu (II), and rapid oil‐water separation with high sorption capacity (11–18 g/g). A remarkable performance for simultaneous removal of their mixtures in milli‐Q, river, and sea water is demonstrated with efficiency for MB (≈90%), Cu (II) (>99.99%) and Hg (II) (100%) and rapid (≈30 s) uptake of organic solvents and oils. The obtained results indicate a valuable potential of proposed concept for simultaneous removal of co‐existing water pollutants.
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Applications of graphene in microbial fuel cells: the gap between promise and reality
(Elsevier, 2017) ElMekawy, A.; Hegab, H.M.; Losic, D.; Saint, C.P.; Pant, D.
Since the initial emergence of two-dimensional graphene (Gr) nano-material, there has been a great interest in its potential applications due to its excellent conductivity, enormous surface area and good mechanical strength. Microbial fuel cells (MFCs) are one of these important promising applications. The limited productivity of MFCs compared to other fuel cell technologies along with the high cost of their components are the two major obstacles to commercialization. Gr is proposed to help overcome such challenges by integrating with biocatalysts for the construction of Gr based MFCs, either as an anode to increase the electron transfer efficiency, or as a cathode to effectively catalyze the oxygen reduction reaction (ORR). This integration is relevant only if the favorable environment for bacterial biofilm adherence to Gr modified surfaces is available. Unfortunately, there is insufficient understanding of the interaction mechanism of bacterial cells with such modified surfaces. Despite this challenge, along with the complexity of the Gr modified electrode fabrication, Gr-based electrodes remain a promising option for developing MFCs to achieve sustainable wastewater treatment and bioelectricity generation. As a reflection on these facts, the aim of this review is to provide critical overview and to evaluate the recent advances for the applications of Gr in MFCs, focusing on electrode fabrication and power generation. Within that context, the concerns about microbial compatibility of Gr will be addressed.
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Assessment of thermoelectric, mechanical, and microstructural reinforcement properties of graphene-mixed heterostructures
(American Chemical Society, 2021) Zaferani, S.H.; Ghomashchi, R.; Vashaee, D.
We examine the role of graphene nanoplates (GNPs) in the critical properties of thermoelectric GNP nanocomposites. After a detailed analysis of the thermoelectric, microstructural, and mechanical characteristics of such nanocomposites, we present a case study based on CoVSn-GNP heterostructures. It is shown that GNPs can improve the mechanical properties without deteriorating the thermoelectric properties of the material. CoVSn-GNP bulk composites are fabricated using powder metallurgy and spark plasma sintering with a GNP weight percentage range of 0–1. All samples with the addition of GNPs showed improved mechanical properties compared with pristine CoVSn. The sample with 0.5 wt % GNPs showed the highest value of Vickers Hardness (737 HV) among all of the studied compositions. Moreover, the fracture toughness was higher for the samples with a lower average crystal size. The concentration and dispersion of GNPs did not significantly change the CoVSn multiphase microstructure; however, it influenced the thermoelectric factors by reducing the thermal conductivity and increasing the Seebeck coefficient, leading to the enhancement of the thermoelectric figure of merit.
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Biodegradable and biocompatible graphene-based scaffolds for functional neural tissue engineering: a strategy approach using dental pulp stem cells and biomaterials
(Wiley, 2021) Mansouri, N.; Al-Sarawi, S.; Losic, D.; Mazumdar, J.; Clark, J.; Gronthos, S.; O'Hare Doig, R.
Neural tissue engineering aims to restore function of nervous system tissues using biocompatible cell-seeded scaffolds. Graphene-based scaffolds combined with stem cells deserve special attention to enhance tissue regeneration in a controlled manner. However, it is believed that minor changes in scaffold biomaterial composition, internal porous structure, and physicochemical properties can impact cellular growth and adhesion. The current work aims to investigate in vitro biological effects of 3D graphene oxide (GO)/sodium alginate (GOSA) and reduced GOSA (RGOSA) scaffolds on dental pulp stem cells (DPSCs) in terms of cell viability and cytotoxicity. Herein, the effects of the 3D scaffolds, coating conditions, and serum supplementation on DPSCs functions are explored extensively. Biodegradation analysis revealed that addition of GO enhanced the degradation rate of composite scaffolds. Compared to the 2D surface, the cell viability of 3D scaffolds was higher (p <0.0001), highlighting the optimal initial cell adhesion to the scaffold surface and cell migration through pores. Moreover, the cytotoxicity study indicated that the incorporation of graphene supported higher DPSCs viability. It is also shown that when the mean pore size of the scaffold increases, DPSCs activity decreases. In terms of coating conditions, poly-l-lysine (PLL) was the most robust coating reagent that improved cell-scaffold adherence and DPSCs metabolism activity. The cytotoxicity of GO-based scaffolds showed that DPSCs can be seeded in serum-free media without cytotoxic effects. This is critical for human translation as cellular transplants are typically serum-free. These findings suggest that proposed 3D GO-based scaffolds have favourable effects on the biological responses of DPSCs. This article is protected by copyright. All rights reserved.
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Biotemplated top-down assembly of hybrid Ni nanoparticles/N doping carbon on diatomite for enhanced catalytic reduction of 4-nitrophenol
(Elsevier, 2020) Jiang, D.B.; Liu, X.; Yuan, Y.; Feng, L.; Ji, J.; Wang, J.; Losic, D.; Yao, H.C.; Zhang, Y.X.
Biotemplated top-down assembly of hybrid Ni nanoparticles/N doping carbon on diatomite (DE/Ni/N-C) was synthesized and used to catalytically reduce 4-nitrophenol (4-NP) solution in presence of NaBH₄. The uniform nickel silicate nanosheets uniformly grown on the diatomite with maintained porous structure, enlarging the specific surface area. The thin polyaniline layer was then controllably coated on the nickel silicate nanosheets. The well-dispersed Ni nanoparticles with mean diameter of 20.3 nm were reduced from nickel silicate nanosheets by carbon from polyaniline pyrolysis process. Meanwhile, the N doping carbon layer was in-situ generated outside of the Ni nanoparticles. In the catalytic reduction of 4-NP reaction, the DE/Ni/N-C-800 exhibited excellent catalytic activity with activity parameter 0.053 mg⁻¹ s⁻¹ and stability after ten cycles. The presented results show an enhanced catalytic behavior of the DE/Ni/N-C-800 prepared by the low-cost material and simple controllable process, which indicates their potential for environmental remediation applications.

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