Publications by authors named "Gordon G Wallace"

268 Publications

Catechol functionalized ink system and thrombin-free fibrin gel for fabricating cellular constructs with mechanical support and inner micro channels.

Biofabrication 2021 Oct 12. Epub 2021 Oct 12.

University of Wollongong, Intelligent Polymer Research Institute, North Wollongong, New South Wales, 2500, AUSTRALIA.

The development of 3D bio printing technology has contributed to protocols for the repair and regeneration of tissues in recent years. However, it is still a great challenge to fabricate structures that mimic the complexity of native tissue, including both the biomechanics and microscale internal structure. In this study, a catechol functionalized ink system was developed to produce tough and elastic scaffolds with built-in micro channels that simulate the vascular structure. A skin model was designed to evaluate the cytocompatibility of the scaffolds. The mechanical support stemmed from the double network based on catechol-hyaluronic acid and alginate, the micro channels were generated using sacrificial gelatin. HACA/alginate and gelatin were firstly printed using a 3D extrusion printer. Thrombin-free fibrinogen were then mixed with human dermal fibroblasts and introduced to the printed scaffolds to induce gelation. An immortal human keratinocyte cell line (HaCaT) was introduced on top of the cellular construct to mimic the full thickness skin structure. The printed scaffolds demonstrated high elasticity and supported the formation of a double-layered cell-laden skin like structure. The results suggest the 3D printing platform developed here provides a platform for skin regeneration and could be explored further to engineer functional skin tissue by incorporation of other types of cells.
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http://dx.doi.org/10.1088/1758-5090/ac2ef8DOI Listing
October 2021

Platinized graphene fiber electrodes uncover direct spleen-vagus communication.

Commun Biol 2021 09 17;4(1):1097. Epub 2021 Sep 17.

Biomedical Engineering and Biomedical Sciences, University of Houston, Health 2, 4849 Calhoun Rd., Room 6014, Houston, TX, 77204-6064, USA.

Neural interfacing nerve fascicles along the splenic neurovascular plexus (SNVP) is needed to better understand the spleen physiology, and for selective neuromodulation of this major organ. However, their small size and anatomical location have proven to be a significant challenge. Here, we use a reduced liquid crystalline graphene oxide (rGO) fiber coated with platinum (Pt) as a super-flexible suture-like electrode to interface multiple SNVP. The Pt-rGO fibers work as a handover knot electrodes over the small SNVP, allowing sensitive recording from four splenic nerve terminal branches (SN 1-4), to uncover differential activity and axon composition among them. Here, the asymmetric defasciculation of the SN branches is revealed by electron microscopy, and the functional compartmentalization in spleen innervation is evidenced in response to hypoxia and pharmacological modulation of mean arterial pressure. We demonstrate that electrical stimulation of cervical and sub-diaphragmatic vagus nerve (VN), evokes activity in a subset of SN terminal branches, providing evidence for a direct VN control over the spleen. This notion is supported by adenoviral tract-tracing of SN branches, revealing an unconventional direct brain-spleen projection. High-performance Pt-rGO fiber electrodes, may be used for the fine neural modulation of other small neurovascular plexus at the point of entry of major organs as a bioelectronic medical alternative.
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http://dx.doi.org/10.1038/s42003-021-02628-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8448843PMC
September 2021

Fused filament fabrication 3D printed polylactic acid electroosmotic pumps.

Lab Chip 2021 09 6;21(17):3338-3351. Epub 2021 Jul 6.

ARC Centre of Excellence for Electromaterials Science (ACES), Intelligent Polymer Research Institute, University of Wollongong, 2522 Australia.

Additive manufacturing (3D printing) offers a flexible approach for the production of bespoke microfluidic structures such as the electroosmotic pump. Here a readily accessible fused filament fabrication (FFF) 3D printing technique has been employed for the first time to produce microcapillary structures using low cost thermoplastics in a scalable electroosmotic pump application. Capillary structures were formed using a negative space 3D printing approach to deposit longitudinal filament arrangements with polylactic acid (PLA) in either "face-centre cubic" or "body-centre cubic" arrangements, where the voids deliberately formed within the deposited structure act as functional micro-capillaries. These 3D printed capillary structures were shown to be capable of functioning as a simple electroosmotic pump (EOP), where the maximum flow rate of a single capillary EOP was up to 1.0 μl min at electric fields of up to 750 V cm. Importantly, higher flow rates were readily achieved by printing parallel multiplexed capillary arrays.
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http://dx.doi.org/10.1039/d1lc00452bDOI Listing
September 2021

Shaping collagen for engineering hard tissues: Towards a printomics approach.

Acta Biomater 2021 09 27;131:41-61. Epub 2021 Jun 27.

Intelligent Polymer Research Institute, ARC Centre of Excellence for Electromaterials Science, AIIM Facility, Innovation Campus, University of Wollongong, NSW 2519, Australia. Electronic address:

Hard tissue engineering has evolved over the past decades, with multiple approaches being explored and developed. Despite the rapid development and success of advanced 3D cell culture, 3D printing technologies and material developments, a gold standard approach to engineering and regenerating hard tissue substitutes such as bone, dentin and cementum, has not yet been realised. One such strategy that differs from conventional regenerative medicine approach of other tissues, is the in vitro mineralisation of collagen templates in the absence of cells. Collagen is the most abundant protein within the human body and forms the basis of all hard tissues. Once mineralised, collagen provides important support and protection to humans, for example in the case of bone tissue. Multiple in vitro fabrication strategies and mineralisation approaches have been developed and their success in facilitating mineral deposition on collagen to achieve bone-like scaffolds evaluated. Critical to the success of such fabrication and biomineralisation approaches is the collagen template, and its chemical composition, organisation, and density. The key factors that influence such properties are the collagen processing and fabrication techniques utilised to create the template, and the mineralisation strategy employed to deposit mineral on and throughout the templates. However, despite its importance, relatively little attention has been placed on these two critical factors. Here, we critically examine the processing, fabrication and mineralisation strategies that have been used to mineralise collagen templates, and offer insights and perspectives on the most promising strategies for creating mineralised collagen scaffolds. STATEMENT OF SIGNIFICANCE: In this review, we highlight the critical need to fabricate collagen templates with advanced processing techniques, in a manner that achieves biomimicry of the hierarchical collagen structure, prior to utilising in vitro mineralisation strategies. To this end, we focus on the initial collagen that is selected, the extraction techniques used and the native fibril forming potential retained to create reconstituted collagen scaffolds. This review synthesises current best practises in material sourcing, processing, mineralisation strategies and fabrication techniques, and offers insights into how these can best be exploited in future studies to successfully mineralise collagen templates.
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http://dx.doi.org/10.1016/j.actbio.2021.06.035DOI Listing
September 2021

Electrochemiluminescence at 3D Printed Titanium Electrodes.

Front Chem 2021 25;9:662810. Epub 2021 May 25.

National Centre for Sensor Research, Chemistry Department, Dublin City University, Dublin, Ireland.

The fabrication and electrochemical properties of a 3D printed titanium electrode array are described. The array comprises 25 round cylinders (0.015 cm radius, 0.3 cm high) that are evenly separated on a 0.48 × 0.48 cm square porous base (total geometric area of 1.32 cm). The electrochemically active surface area consists of fused titanium particles and exhibits a large roughness factor ≈17. In acidic, oxygenated solution, the available potential window is from ~-0.3 to +1.2 V. The voltammetric response of ferrocyanide is quasi-reversible arising from slow heterogeneous electron transfer due to the presence of a native/oxidatively formed oxide. Unlike other metal electrodes, both [Ru(bpy)] and [Ru(bpy)] can be created in solutions which enables electrochemiluminescence to be generated by an annihilation mechanism. Depositing a thin gold layer significantly increases the standard heterogeneous electron transfer rate constant, k, by a factor of ~80 to a value of 8.0 ± 0.4 × 10 cm s and the voltammetry of ferrocyanide becomes reversible. The titanium and gold coated arrays generate electrochemiluminescence using tri-propyl amine as a co-reactant. However, the intensity of the gold-coated array is between 30 (high scan rate) and 100-fold (slow scan rates) higher at the gold coated arrays. Moreover, while the voltammetry of the luminophore is dominated by semi-infinite linear diffusion, the ECL response is significantly influenced by radial diffusion to the individual microcylinders of the array.
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http://dx.doi.org/10.3389/fchem.2021.662810DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8186460PMC
May 2021

Abuse-Tolerant Electrolytes for Lithium-Ion Batteries.

Adv Sci (Weinh) 2021 Jun 18;8(11):e2003694. Epub 2021 Mar 18.

ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, AIIM Facility, Innovation Campus, University of Wollongong, Wollongong, NSW, 2500, Australia.

Safety issues currently limit the development of advanced lithium-ion batteries (LIBs) and this is exacerbated when they are misused or abused. The addition of small amounts of fillers or additives into common liquid electrolytes can greatly improve resistance to abuse without impairing electrochemical performance. This review discusses the recent progress in such abuse-tolerant electrolytes. It covers electrolytes with shear thickening properties for tolerating mechanical abuse, electrolytes with redox shuttle additives for suppressing electrochemical abuse, and electrolytes with flame-retardant additives for resisting thermal abuse. It aims to provide insights into the functioning of such electrolytes and the understanding of electrolyte composition-property relationship. Future perspectives, challenges, and opportunities towards practical applications are also presented.
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http://dx.doi.org/10.1002/advs.202003694DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8188208PMC
June 2021

Reference Phantom Method for Ultrasonic Imaging of Thin Dynamic Constructs.

Ultrasound Med Biol 2021 08 29;47(8):2388-2403. Epub 2021 May 29.

ARC Centre of Excellence for Electromaterials Science (ACES), Intelligent Polymer Research Institute, AIIM Facility, Innovation Campus, University of Wollongong, Wollongong, New South Wales, Australia. Electronic address:

Quantitative ultrasound has a great potential for the non-destructive evaluation of tissue engineered constructs, where the local attenuation and the integrated backscatter coefficient (IBC) can be used for monitoring the development of biological processes. The local determination of both parameters can be achieved using the reference phantom method (RPM). However, its accuracy can be affected when evaluating constructs of evolving sound speed, attenuation and thickness, for example, when evaluating biodegradable hydrogels developing neocartilage. To assess the feasibility of using the RPM under such dynamic conditions while employing a 50-MHz transducer, we conducted a series of experiments on 3-mm-thick acellular hydrogels laden with microspheres. The ultrasonic evaluation procedure used was validated by detecting and compensating for large attenuation variations occurring in the construct, up to 20-fold with respect to the reference phantom, with estimations errors below 1%. We found that sound speed mismatch does not affect the local attenuation estimation, but causes a strong diffraction effect by reducing the backscatter intensity. Such intensity reduction was compensated by determining the IBC percentage change (IBC) as function of sound speed mismatch with respect to the reference phantom (ΔSS), with the equation IBC = (0.63 ± 0.07) ΔSS + (8.54 ± 0.76) 10 ΔSS. The investigated ΔSS interval was up to 120 m/s and using two different concentrations of microspheres, with estimation errors below 7% relative to the construct's actual IBC. Finally, we found that the spectral difference method is sufficient to measure within a few millimetres in depth mismatch, and when combining with sound speed mismatch, we found negligible additional effects. These results pave the way for the use of a generic reference phantom for the evaluation of thin dynamic constructs, thus simplifying the need for using different phantoms depending on the construct's properties.
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http://dx.doi.org/10.1016/j.ultrasmedbio.2021.04.014DOI Listing
August 2021

Boosting Formate Production from CO at High Current Densities Over a Wide Electrochemical Potential Window on a SnS Catalyst.

Adv Sci (Weinh) 2021 Aug 29;8(15):e2004521. Epub 2021 May 29.

ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, AIIM, Innovation Campus, University of Wollongong, Wollongong, NSW, 2500, Australia.

The flow-cell design offers prospect for transition to commercial-relevant high current density CO electrolysis. However, it remains to understand the fundamental interplay between the catalyst, and the electrolyte in such configuration toward CO reduction performance. Herein, the dramatic influence of electrolyte alkalinity in widening potential window for CO electroreduction in a flow-cell system based on SnS nanosheets is reported. The optimized SnS catalyst operated in 1 m KOH achieves a maximum formate Faradaic efficiency of 88 ± 2% at -1.3 V vs reversible hydrogen electrode (RHE) with the current density of ≈120 mA cm . Alkaline electrolyte is found suppressing the hydrogen evolution across all potentials which is particularly dominant at the less negative potentials, as well as CO evolution at more negative potentials. This in turn widens the potential window for formate conversion (>70% across -0.5 to -1.5 V vs RHE). A comparative study to SnOx counterpart indicates sulfur also acts to suppress hydrogen evolution, although electrolyte alkalinity resulting in a greater suppression. The boosting of the electrochemical potential window, along with high current densities in SnS derived catalytic system offers a highly attractive and promising route toward industrial-relevant electrocatalytic production of formate from CO .
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http://dx.doi.org/10.1002/advs.202004521DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8336617PMC
August 2021

Wireless electrochemiluminescence at functionalised gold microparticles using 3D titanium electrode arrays.

Chem Commun (Camb) 2021 May;57(38):4642-4645

National Centre for Sensor Research, School of Chemical Sciences, Dublin City University, FutureNeuro SFI Research Centre, Dublin 9, Ireland. and SensorLab (UWC Sensor Laboratories), Chemical Sciences Building, University of Western Cape Town, Robert Sobukwe Road, Bellville 7535, Cape, South Africa.

Wireless electrochemiluminescence is generated using interdigitated, 3D printed, titanium arrays as feeder electrodes to shape the electric field. Gold microparticles (45 μm diameter), functionalised with 11-mercaptoundecanoic acid, act as micro-emitters to generate electrochemiluminescence from [Ru(bpy)3]2+, (bpy is 2,2'-bipyridine) where the co-reactant is tripropylamine. The oxide coated titanium allows intense electric fields, whose distribution depends on the geometry of the array, to be created in the absence of deliberately added electrolyte. COMSOL modelling and long exposure ECL imaging have been used to map the electric field distribution. Significantly, we demonstrate that by controlling the surface charge of the gold microparticles through the solution pH, the light intensity can be increased by a factor of more than 10.
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http://dx.doi.org/10.1039/d1cc01010gDOI Listing
May 2021

Engineering human neural tissue analogs by 3D bioprinting and electrostimulation.

APL Bioeng 2021 Jun 2;5(2):020901. Epub 2021 Apr 2.

ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, AIIM Facility, University of Wollongong, Fairy Meadow, NSW 2519 Australia.

There is a fundamental need for clinically relevant, reproducible, and standardized human neural tissue models, not least of all to study heterogenic and complex human-specific neurological (such as neuropsychiatric) disorders. Construction of three-dimensional (3D) bioprinted neural tissues from native human-derived stem cells (e.g., neural stem cells) and human pluripotent stem cells (e.g., induced pluripotent) in particular is appreciably impacting research and conceivably clinical translation. Given the ability to artificially and favorably regulate a cell's survival and behavior by manipulating its biophysical environment, careful consideration of the printing technique, supporting biomaterial and specific exogenously delivered stimuli, is both required and advantageous. By doing so, there exists an opportunity, more than ever before, to engineer advanced and precise tissue analogs that closely recapitulate the morphological and functional elements of natural tissues (healthy or diseased). Importantly, the application of electrical stimulation as a method of enhancing printed tissue development , including neuritogenesis, synaptogenesis, and cellular maturation, has the added advantage of modeling both traditional and new stimulation platforms, toward improved understanding of efficacy and innovative electroceutical development and application.
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http://dx.doi.org/10.1063/5.0032196DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8019355PMC
June 2021

Fibrinogen, collagen, and transferrin adsorption to poly(3,4-ethylenedioxythiophene)-xylorhamno-uronic glycan composite conducting polymer biomaterials for wound healing applications.

Biointerphases 2021 03 22;16(2):021003. Epub 2021 Mar 22.

ARC Centre of Excellence for Electromaterials Science (ACES), Intelligent Polymer Research Institute, University of Wollongong, Wollongong, Australia.

We present the conducting polymer poly (3,4-ethylenedioxythiophene) (PEDOT) doped with an algal-derived glycan extract, Phycotrix™ [xylorhamno-uronic glycan (XRU84)], as an innovative electrically conductive material capable of providing beneficial biological and electrical cues for the promotion of favorable wound healing processes. Increased loading of the algal XRU84 into PEDOT resulted in a reduced surface nanoroughness and interfacial surface area and an increased static water contact angle. PEDOT-XRU84 films demonstrated good electrical stability and charge storage capacity and a reduced impedance relative to the control gold electrode. A quartz crystal microbalance with dissipation monitoring study of protein adsorption (transferrin, fibrinogen, and collagen) showed that collagen adsorption increased significantly with increased XRU84 loading, while transferrin adsorption was significantly reduced. The viscoelastic properties of adsorbed protein, characterized using the ΔD/Δf ratio, showed that for transferrin and fibrinogen, a rigid, dehydrated layer was formed at low XRU84 loadings. Cell studies using human dermal fibroblasts demonstrated excellent cell viability, with fluorescent staining of the cell cytoskeleton illustrating all polymers to present excellent cell adhesion and spreading after 24 h.
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http://dx.doi.org/10.1116/6.0000708DOI Listing
March 2021

One-Pot Hydrothermal Synthesis of Solution-Processable MoS/PEDOT:PSS Composites for High-Performance Supercapacitors.

ACS Appl Mater Interfaces 2021 Feb 2;13(6):7285-7296. Epub 2021 Feb 2.

Intelligent Polymer Research Institute, ARC Centre of Excellence for Electromaterials Science, AIIM Facility, Innovation Campus, University of Wollongong, Wollongong, New South Wales 2522, Australia.

It is challenging to hydrothermally synthesize solution-processable MoS, as the strong van der Waals force between MoS nanosheets induces self-assembly of agglomerates. Here, we introduce poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) into the precursor to impede aggregate formation in the hydrothermal process. A hybrid MoS/PEDOT:PSS (MP) hydrogel is formed due to the electrostatic interactions between the negatively charged MoS and positively charged PEDOT chains. This hydrogel can be easily dispersed in water for subsequent solution processing such as vacuum filtration to form free-standing flexible films or extrusion 3D printing to create novel patterns. The MP film with a fracture strength of 18.59 MPa displays excellent electrochemical performance in both aqueous NaSO electrolyte (474 mF cm) and solid-state PVA-HPO electrolyte (360 mF cm). Flexibility and robustness can be evidenced by high capacitance retention rates of 94 and 89% after being repeatedly bent to 180° for 5000 cycles in aqueous and solid-state electrolytes, respectively.
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http://dx.doi.org/10.1021/acsami.0c21439DOI Listing
February 2021

In vitro characterisation of 3D printed platelet lysate-based bioink for potential application in skin tissue engineering.

Acta Biomater 2021 03 18;123:286-297. Epub 2021 Jan 18.

ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, Innovation Campus, University of Wollongong, Wollongong, NSW 2500, Australia. Electronic address:

Wounds impact millions of patients every year and represent a serious cause of morbidity and mortality worldwide, yet current treatment outcomes are far from ideal. Therapies based on delivery of multiple growth factors offer a promising approach for optimal wound management; however, their high production cost, low stability, and lack of effective delivery system limits their application in the clinic. Platelet lysate is a suitable, abundant and cost-effective source of growth factors that play an important role in the healing cascade. The aim of this current work is to develop an extrusion-based bioink consisting of platelet lysate (PL) and gelatin methacryloyl (GelMA) (PLGMA) for the fabrication of a multifunctional 3D printed dermal equivalent. This bioink meets the essential requirements of printability in terms of rheological properties and shape fidelity. Moreover, its mechanical properties can be readily tuned to achieve stiffness that is equivalent to native skin tissue. Biologically relevant factors were successfully released in a sustainable manner for up to two weeks of study. The bioavailability of those factors was demonstrated by high cell viability, good cell attachment and improved proliferation of printed dermal fibroblasts. Furthermore, growth factors upregulated ECM synthesis and deposition by dermal fibroblasts after two weeks of culture.
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http://dx.doi.org/10.1016/j.actbio.2021.01.021DOI Listing
March 2021

Fabrication of Aligned Biomimetic Gellan Gum-Chitosan Microstructures through 3D Printed Microfluidic Channels and Multiple In Situ Cross-Linking Mechanisms.

ACS Biomater Sci Eng 2020 06 26;6(6):3638-3648. Epub 2020 May 26.

Intelligent Polymer Research Institute (IPRI), ARC Centre of Excellence for Electromaterials Science (ACES), Australian Institute for Innovative Materials (AIIM), University of Wollongong, Innovation Campus, Wollongong, NSW 2522, Australia.

In this study we use a combination of ionic- and photo-cross-linking to develop a fabrication method for producing biocompatible microstructures using a methacrylated gellan gum (a polyanion) and chitosan (a polycation) in addition to lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) as the photoinitiator. This work involves the development of a low-cost, portable 3D bioprinter and a customized extrusion mechanism for controlled introduction of the materials through a 3D printed microfluidic nozzle, before being cross-linked in situ to form robust microstructure bundles. The formed microstructures yielded a diameter of less than 1 μm and a tensile strength range of ∼1 MPa. This study is the first to explore and achieve GGMA:CHT microstructure fabrication by means of controlled in-line compaction and photo-cross-linking through 3D printed microfluidic channels.
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http://dx.doi.org/10.1021/acsbiomaterials.0c00260DOI Listing
June 2020

3D hybrid printing platform for auricular cartilage reconstruction.

Biomed Phys Eng Express 2020 03 4;6(3):035003. Epub 2020 Mar 4.

ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, University of Wollongong, Wollongong, NSW 2522, Australia.

As scaffolds approach dimensions that are of clinical relevance, mechanical integrity and distribution becomes an important factor to the overall success of the implant. Hydrogels often lack the structural integrity and mechanical properties for use in vivo or handling. The inclusion of a structural support during the printing process, referred to as hybrid printing, allows the implant to retain structure and protect cells during maturation without needing to compromise its biological performance. In this study, scaffolds for the purpose of auricular cartilage reconstruction were evaluated via a hybrid printing approach using methacrylated Gelatin (GelMA) and Hyaluronic acid (HAMA) as the cell-laden hydrogel, Polycaprolactone (PCL) as structural support and Lutrol F-127 as sacrificial material. Furthermore, printing parameters such as nozzle diameter, strand spacing and filament orientation scaffolds were investigated. Compression and bending tests showed that increasing nozzle sizes decrease the compressive modulus of printed scaffolds, with up to 82% decrease in modulus when comparing between a 400 μm and 200 μm sized nozzle tip at the same strand spacing. On the contrary, strand spacing and orientation influences mainly the bending modulus due to the greater porosity and changes in pore size area. Using a 400 μm sized nozzle, scaffolds fabricated have a measured compression and bending modulus in the range similar to the native cartilage. The viability and proliferation of human mesenchymal stem cells delivered within the bioink was not affected by the printing process. Using results obtained from mechanical testing, a scaffold with matching mechanical properties across six distinct regions mimicking the human auricular cartilage can be completed in one single print process. The use of PCL and GelMA-HAMA as structural support and cell-laden hydrogel respectively are an excellent combination to provide tailored mechanical integrity, while maintaining porosity and protection to cells during differentiation.
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http://dx.doi.org/10.1088/2057-1976/ab54a7DOI Listing
March 2020

3D bioprinting dermal-like structures using species-specific ulvan.

Biomater Sci 2021 Apr 11;9(7):2424-2438. Epub 2021 Jan 11.

ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, Innovation Campus, University of Wollongong, NSW 2500, Australia.

3D bioprinting has been increasingly employed in skin tissue engineering for manufacturing living constructs with three-dimensional spatial precision and controlled architecture. There is however, a bottleneck in the tunability of bioinks to address specific biocompatibility challenges, functional traits and printability. Here we report on a traditional gelatin methacryloyl (GelMA) based bioink, tuned by addition of an ulvan type polysaccharide, isolated from a cultivated source of a specific Australian Ulvacean macroalgae (Ul84). Ul84 is a sulfate- and rhamnose-rich polysaccharide, resembling mammalian glycosaminoglycans that are involved in wound healing and tissue matrix structure and function. Printable bioinks were developed by addition of methacrylated Ul84 (UlMA) to GelMA solutions. The inclusion of UlMA in the bioinks facilitated the extrusion printing process by reducing yield stress. The resultant printed structures containing ulvan exhibited improved mechanical strength and regulated the rate of scaffold degradation. The 3D printed cell-laden structures with human dermal fibroblasts demonstrated high cell viability, support of cell proliferation and dermal-like properties as evidenced by the deposition of key dermal extracellular matrix components including collagen I, collagen III, elastin and fibronectin. In vitro degradation suggested the role of UlMA in supporting structural stability of the printed cellular structures. Taken together, the present work demonstrates progression towards a biocompatible and biofunctional ink that simultaneously delivers improved mechanical, structural and stability traits that are important in facilitating real world applications in skin tissue repair.
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http://dx.doi.org/10.1039/d0bm01784aDOI Listing
April 2021

Hybrid Printing Using Cellulose Nanocrystals Reinforced GelMA/HAMA Hydrogels for Improved Structural Integration.

Adv Healthc Mater 2020 12 16;9(24):e2001410. Epub 2020 Nov 16.

Intelligent Polymer Research Institute, University of Wollongong, Wollongong, NSW, 2500, Australia.

3D printing of soft-tissue like cytocompatible single material constructs with appropriate mechanical properties remains a challenge. Hybrid printing technology provides an attractive alternative as it combines a cell-free ink for providing mechanical support with a bioink for housing embedded cells. Several hybrid printed structures have been developed, utilizing thermoplastic polymers such as polycaprolactone as structural support. These thermoplastics demonstrated limited structural integration with the cell-laden components, and this may compromise the overall performance. In this work, a hybrid printing platform is presented using two distinct hydrogel inks that share the same photo-crosslinking chemistry to enable simple fabrication and seamless structural integration. A mechanically reinforced hydrogel ink is developed comprising cellulose nanocrystals and gelatin methacryloyl/hyaluronic acid methacrylate (GelMA/HAMA) as the structural component, and GelMA/HAMA as the cytogel containing a mouse chondrogenic cell line, ATDC5. Hybrid printed constructs with encapsulated cells are fabricated using the two optimized inks, and the structural integration of the constructs is evaluated by cyclic mechanical compression. Finally, the cell viability of encapsulated ATDC5 cells in the hybrid printed structures is evaluated.
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http://dx.doi.org/10.1002/adhm.202001410DOI Listing
December 2020

FLASH: Fluorescently LAbelled Sensitive Hydrogel to monitor bioscaffolds degradation during neocartilage generation.

Biomaterials 2021 01 14;264:120383. Epub 2020 Sep 14.

Department of Surgery, The University of Melbourne, Australia; BioFab3D-ACMD-St Vincent's Hospital Melbourne, Australia; Department of Orthopaedics, St Vincent's Hospital Melbourne, Australia.

Regenerative therapies based on photocrosslinkable hydrogels and stem cells are of growing interest in the field of cartilage repair. Cell-mediated degradation is critical for the successful clinical translation of implanted hydrogels. However, characterising cell-mediated degradation, while simultaneously monitoring the deposition of a distinct new matrix, remains a major challenge. In this study we generated a Fluorescently LAbelled Sensitive Hydrogel (FLASH) to correlate the degradation of a hydrogel bioscaffold with neocartilage formation. Gelatine Methacryloyl (GelMA) was covalently bound to the FITC fluorophore to generate FLASH and bioscaffolds were produced by casting different concentrations of FLASH GelMA, with and without human adipose-derived stem cells (hADSCs) undergoing chondrogenesis. The loss of fluorescence from FLASH bioscaffolds was correlated with changes in mechanical properties, expression of chondrogenic markers and accumulation of a cartilaginous extracellular matrix. The ability of the system to be used as a sensor to monitor bioscaffold degradability during chondrogenesis was evaluated in vitro, in a human ex vivo model of cartilage repair and in a full chondral defect in vivo rabbit model. This study represents a step towards the generation of a high throughput monitoring system to evaluate de novo cartilage formation in tissue engineering therapies.
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http://dx.doi.org/10.1016/j.biomaterials.2020.120383DOI Listing
January 2021

Data on the bipolar electroactive conducting polymers for wireless cell stimulation.

Data Brief 2020 Dec 11;33:106406. Epub 2020 Oct 11.

ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, Australian Institute for Innovative Materials, Innovation Campus, University of Wollongong, Squires Way, North Wollongong, NSW 2519, Australia.

Data in this article is associated with our research article "Bipolar Electroactive Conducting Polymers for Wireless Cell Stimulation" [1]. Primarily, the present article shows the data of PPy-TS, PPy-DS and PPy-DS/collagen in conventional electrochemical process and bipolar electrochemical process for comprehensive supplement and comparison to help with better understanding and developing conducting polymers based bipolar electrochemistry. Secondly, the presented data of bipolar electrostimulation (BPES) protocol development constitute the complete dataset useful for modeling the bipolar electroactive conducting polymers focusing on wireless cell stimulation, which are reported in the main article. All data reported were analysed using Origin 2018b 64Bit.
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http://dx.doi.org/10.1016/j.dib.2020.106406DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7567922PMC
December 2020

Dual Delivery of Gemcitabine and Paclitaxel by Wet-Spun Coaxial Fibers Induces Pancreatic Ductal Adenocarcinoma Cell Death, Reduces Tumor Volume, and Sensitizes Cells to Radiation.

Adv Healthc Mater 2020 11 1;9(21):e2001115. Epub 2020 Oct 1.

School of Chemistry and Molecular Bioscience, Molecular Horizons, University of Wollongong, Wollongong, NSW, 2522, Australia.

Pancreatic ductal adenocarcinoma (PDAC) has a dismal prognosis, with surgical resection of the tumor in conjunction with systemic chemotherapy the only potential curative therapy. Up to 80% of diagnosed cases are deemed unresectable, prompting the need for alternative treatment approaches. Herein, coaxial polymeric fibers loaded with two chemotherapeutic agents, gemcitabine (Gem) and paclitaxel (Ptx), are fabricated to investigate the effect of local drug delivery on PDAC cell growth in vitro and in vivo. A wet-spinning fabrication method to form a coaxial fiber with a polycaprolactone shell and alginate core loaded with Ptx and Gem, respectively, is used. In vitro, Gem+Ptx fibers display significant cytotoxicity as well as radiosensitizing properties toward PDAC cell lines greater than the equivalent free drugs, which may be attributed to a radiosensitizing effect of the polymers. In vivo studies assessing Gem+Ptx fiber efficacy found that Gem+Ptx fibers reduce tumor volume in a xenograft mouse model of PDAC. Importantly, no difference in mouse weight, circulating cytokines, or liver function is observed in mice treated with Gem+Ptx fibers compared to the empty fiber controls confirming the safety of the implant approach. With further development, Gem+Ptx fibers can improve the treatment of unresectable PDAC in the future.
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http://dx.doi.org/10.1002/adhm.202001115DOI Listing
November 2020

Bidirectional Core Sandwich Structure of Reduced Graphene Oxide and Spinnable Multiwalled Carbon Nanotubes for Electromagnetic Interference Shielding Effectiveness.

ACS Appl Mater Interfaces 2020 Oct 30;12(41):46883-46891. Epub 2020 Sep 30.

Center for Self-Powered Actuation, Department of Biomedical Engineering, Hanyang University, Seoul 04763, Korea.

Thin and flexible electromagnetic shielding materials have recently emerged because of their promising applications in drones, portable electronics, military defense facilities, etc. This research develops an electromagnetic interference (EMI) shielding material by a bidirectional lattice sandwich structure (BLSS), which is formed by liquid crystalline graphene oxide (LCGO) and an orthogonal pattern of spinnable multiwalled (OPSM) nanotubes in consideration of the movement of electromagnetic waves. The average EMI shielding effectiveness (SE) of the developed material with 0.5 wt % reduced LCGO (r-LCGO) and an OPSM nanotube composed of 64 layers was approximately 66.1 dB in the X-band frequency range (8.2-12.4 GHz, wavelength: 3.5-2.5 cm), which corresponds to a shielding efficiency of 99.9999%. Also, its absorption effectiveness is 99.7% of the total EMI SE, indicating that it has a remarkable ability to prevent secondary damage induced by EM reflection. The specific EMI SE (SSE/) of the composite material considering the contribution of thickness () ranged from 21 953 to 2259 dB cm/g.
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http://dx.doi.org/10.1021/acsami.0c11460DOI Listing
October 2020

3D Printing of Cytocompatible Graphene/Alginate Scaffolds for Mimetic Tissue Constructs.

Front Bioeng Biotechnol 2020 17;8:824. Epub 2020 Jul 17.

ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, AIIM Facility, University of Wollongong, Wollongong, NSW, Australia.

Tissue engineering, based on a combination of 3D printing, biomaterials blending and stem cell technology, offers the potential to establish customized, transplantable autologous implants using a patient's own cells. Graphene, as a two-dimensional (2D) version of carbon, has shown great potential for tissue engineering. Here, we describe a novel combination of graphene with 3D printed alginate (Alg)-based scaffolds for human adipose stem cell (ADSC) support and osteogenic induction. Alg printing was enabled through addition of gelatin (Gel) that was removed after printing, and the 3D structure was then coated with graphene oxide (GO). GO was chemically reduced with a biocompatible reductant (ascorbic acid) to provide electrical conductivity and cell affinity sites. The reduced 3D graphene oxide (RGO)/Alg scaffold has good cytocompatibility and can support human ADSC proliferation and osteogenic differentiation. Our finding supports the potential for the printed scaffold's use for engineering of bone and other tissues using ADSCs and potentially other human stem cells, as well as regenerative medicine.
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http://dx.doi.org/10.3389/fbioe.2020.00824DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7379132PMC
July 2020

Nanotechnology-based disinfectants and sensors for SARS-CoV-2.

Nat Nanotechnol 2020 08;15(8):618-621

NOVA Medical School, Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Lisboa, Portugal.

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http://dx.doi.org/10.1038/s41565-020-0751-0DOI Listing
August 2020

A Self-Assembled CO Reduction Electrocatalyst: Posy-Bouquet-Shaped Gold-Polyaniline Core-Shell Nanocomposite.

ChemSusChem 2020 Sep 10;13(18):5023-5030. Epub 2020 Aug 10.

ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, AIIM Facility, University of Wollongong, North Wollongong, NSW, 2500, Australia.

Here it was demonstrated that the decoration of gold (Au) with polyaniline is an effective approach in increasing its electrocatalytic reduction of CO to CO. The core-shell-structured gold-polyaniline (Au-PANI) nanocomposite delivered a CO -to-CO conversion efficiency of 85 % with a high current density of 11.6 mA cm . The polyaniline shell facilitated CO adsorption, and the subsequent formation of reaction intermediates on the gold core contributed to the high efficiency observed.
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http://dx.doi.org/10.1002/cssc.202001248DOI Listing
September 2020

Biomimetic corneal stroma using electro-compacted collagen.

Acta Biomater 2020 09 8;113:360-371. Epub 2020 Jul 8.

ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, AIIM Facility, Innovation Campus, University of Wollongong, Fairy Meadow, New South Wales 2519, Australia. Electronic address:

Engineering substantia propria (or stroma of cornea) that mimics the function and anatomy of natural tissue is vital for in vitro modelling and in vivo regeneration. There are, however, few examples of bioengineered biomimetic corneal stroma. Here we describe the construction of an orthogonally oriented 3D corneal stroma model (3D-CSM) using pure electro-compacted collagen (EC). EC films comprise aligned collagen fibrils and support primary human corneal stromal cells (hCSCs). Cell-laden constructs are analogous to the anatomical structure of native human cornea. The hCSCs are guided by the topographical cues provided by the aligned collagen fibrils of the EC films. Importantly, the 3D-CSM are biodegradable, highly transparent, glucose-permeable and comprise quiescent hCSCs. Gene expression analysis indicated the presence of aligned collagen fibrils is strongly coupled to downregulation of active fibroblast/myofibroblast markers α-SMA and Thy-1, with a concomitant upregulation of the dormant keratocyte marker ALDH3. The 3D-CSM represents the first example of an optimally robust biomimetic engineered corneal stroma that is constructed from pure electro-compacted collagen for cell and tissue support. The 3D-CSM is a significant advance for synthetic corneal stroma engineering, with the potential to be used for full-thickness and functional cornea replacement, as well as informing in vivo tissue regeneration. STATEMENT OF SIGNIFICANCE: This manuscript represents the first example of a robust, transparent, glucose permeable and pure collagen-based biomimetic 3D corneal stromal model (3D-CSM) constructed from pure electro-compacted collagen. The collagen fibrils of 3D-CSM are aligned and orthogonally arranged, mimicking native human corneal stroma. The alignment of collagen fibrils correlates with the direction of current applied for electro-compaction and influences human corneal stromal cell (hCSC) orientation. Moreover, 3D-CSM constructs support a corneal keratocyte phenotype; an essential requirement for modelling healthy corneal stroma. As-prepared 3D-CSM hold great promise as corneal stromal substitutes for research and translation, with the potential to be used for full-thickness cornea replacement.
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http://dx.doi.org/10.1016/j.actbio.2020.07.004DOI Listing
September 2020

Multitechnology Biofabrication: A New Approach for the Manufacturing of Functional Tissue Structures?

Trends Biotechnol 2020 12 25;38(12):1316-1328. Epub 2020 May 25.

Department of Orthopaedics, University Medical Center Utrecht, Utrecht, The Netherlands; Regenerative Medicine Center Utrecht, Utrecht, The Netherlands; Department of Clinical Sciences, Faculty of Veterinary Sciences Utrecht University, Utrecht, The Netherlands.

Most available 3D biofabrication technologies rely on single-component deposition methods, such as inkjet, extrusion, or light-assisted printing. It is unlikely that any of these technologies used individually would be able to replicate the complexity and functionality of living tissues. Recently, new biofabrication approaches have emerged that integrate multiple manufacturing technologies into a single biofabrication platform. This has led to fabricated structures with improved functionality. In this review, we provide a comprehensive overview of recent advances in the integration of different manufacturing technologies with the aim to fabricate more functional tissue structures. We provide our vision on the future of additive manufacturing (AM) technology, digital design, and the use of artificial intelligence (AI) in the field of biofabrication.
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http://dx.doi.org/10.1016/j.tibtech.2020.04.014DOI Listing
December 2020

Nanoscale piezoelectric effect of biodegradable PLA-based composite fibers by piezoresponse force microscopy.

Nanotechnology 2020 Sep 27;31(37):375708. Epub 2020 May 27.

ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute/AIIM Faculty, Innovation Campus, Squires Way, University of Wollongong, Wollongong, NSW 2522, Australia. Materials Charaterisation and Fabrication Platform, University of Melbourne, Melbourne, VIC 3010, Australia.

The piezoelectricity of the biocompatible and biodegradable polymer polylactic acid (PLA) was investigated as a potential magnetoelectric (ME) nanocomposite for biomedical applications. A key focus was to quantify the piezoelectric properties of single PLA fibers while tuning their polymer degradability through the addition of faster degrading polymer, poly (DL-lactide-co-glycolide) (PLGA), which is not a piezoelectric polymer. Piezoresponse Force Microscopy (PFM) showed that electrospun PLA fibers gave a piezoelectric response of 186 ± 28 pm. For comparison both PLA/PLGA (75/25) and PLA/PLGA (50/50) fibers gave significantly lower piezoelectric responses of 89 ± 12 pm and 50 ± 9.1 pm, respectively. For the highest content PLGA fibers, PLA/PLGA (25/75), only very few fibers exhibited a low response of 28 pm while most showed no response. Overall, an increasing PLGA content caused a decrease in the piezoelectric response, thus an expected trade-off existed between the biodegradability (i.e. PLA to PLGA content ratio) versus piezoelectricity. The findings were considered significant due to the existence of piezoelectricity in a tuneable biodegradable material that has potential to impart piezoelectric induced effects on biointeractions with the surrounding biological environment or drug interactions with the polymer to control the rate of drug release. In such applications, there is an opportunity to magnetically control the piezoelectricity and henceforth PLA/CoFeO ME nanocomposite fibers with 5% and 10% of CoFeO nanoparticles were also investigated. Both 5% and 10% PLA/CoFeO nanocomposites gave lower piezoelectric responses compared to the PLA presumably due to the disturbance of polymer chains and dipole moments by the magnetic nanoparticles, in addition to effects from the possible inhomogeneous distribution of CoFeO nanoparticles.
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http://dx.doi.org/10.1088/1361-6528/ab96e3DOI Listing
September 2020

Electrofluidic control of bioactive molecule delivery into soft tissue models based on gelatin methacryloyl hydrogels using threads and surgical sutures.

Sci Rep 2020 04 28;10(1):7120. Epub 2020 Apr 28.

Australian Centre for Research on Separation Science (ACROSS) and ARC Centre of Excellence for Electromaterials Science (ACES), School of Natural Sciences, Faculty of Chemistry, University of Tasmania, Tasmania, TAS 7005, Australia.

The delivery of bioactive molecules (drugs) with control over spatial distribution remains a challenge. Herein, we demonstrate for the first time an electrofluidic approach to controlled delivery into soft tissue models based on gelatin methacryloyl (GelMA) hydrogels. This was achieved using a surgical suture, whereby transport of bioactive molecules, including drugs and proteins, was controlled by imposition of an electric field. Commonly employed surgical sutures or acrylic threads were integrated through the hydrogels to facilitate the directed introduction of bioactive species. The platform consisted of two reservoirs into which the ends of the thread were immersed. The anode and cathode were placed separately into each reservoir. The thread was taken from one reservoir to the other through the gel. When current was applied, biomolecules loaded onto the thread were directed into the gel. Under the same conditions, the rate of movement of the biomolecules along GelMA was dependent on the magnitude of the current. Using 5% GelMA and a current of 100 µA, 2 uL of fluorescein travelled through the hydrogel at a constant velocity of 7.17 ± 0.50 um/s and took less than 8 minutes to exit on the thread. Small molecules such as riboflavin migrated faster (5.99 ± 0.40 μm/s) than larger molecules such as dextran (2.26 ± 0.55 μm/s with 4 kDa) or BSA (0.33 ± 0.07 μm/s with 66.5 kDa). A number of commercial surgical sutures were tested and found to accommodate the controlled movement of biomolecules. Polyester, polyglactin 910, glycolide/lactide copolymer and polyglycolic acid braided sutures created adequate fluid connection between the electrodes and the hydrogel. With a view to application in skin inflammatory diseases and wound treatment, wound healing, slow and controlled delivery of dexamethasone 21-phosphate disodium salt (DSP), an anti-inflammatory prodrug, was achieved using medical surgicryl PGA absorbable suture. After 2 hours of electrical stimulation, still 81.1% of the drug loaded was encapsulated within the hydrogel.
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http://dx.doi.org/10.1038/s41598-020-63785-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7188853PMC
April 2020

3D Bioprinting and Differentiation of Primary Skeletal Muscle Progenitor Cells.

Methods Mol Biol 2020 ;2140:229-242

@BioFab3D Facility, St Vincent's Hospital Melbourne, Melbourne, VIC, Australia.

Volumetric loss of skeletal muscle can occur through sports injuries, surgical ablation, trauma, motor or industrial accident, and war-related injury. Likewise, massive and ultimately catastrophic muscle cell loss occurs over time with progressive degenerative muscle diseases, such as the muscular dystrophies. Repair of volumetric loss of skeletal muscle requires replacement of large volumes of tissue to restore function. Repair of larger lesions cannot be achieved by injection of stem cells or muscle progenitor cells into the lesion in absence of a supportive scaffold that (1) provides trophic support for the cells and the recipient tissue environment, (2) appropriate differentiational cues, and (3) structural geometry for defining critical organ/tissue components/niches necessary or a functional outcome. 3D bioprinting technologies offer the possibility of printing orientated 3D structures that support skeletal muscle regeneration with provision for appropriately compartmentalized components ranging across regenerative to functional niches. This chapter includes protocols that provide for the generation of robust skeletal muscle cell precursors and methods for their inclusion into methacrylated gelatin (GelMa) constructs using 3D bioprinting.
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http://dx.doi.org/10.1007/978-1-0716-0520-2_15DOI Listing
March 2021

Bioprinting Stem Cells in Hydrogel for In Situ Surgical Application: A Case for Articular Cartilage.

Methods Mol Biol 2020 ;2140:145-157

[email protected], St Vincent's Hospital, Melbourne, VIC, Australia.

Three-dimensional (3D) bioprinting is driving major innovations in the area of cartilage tissue engineering. As an alternative to computer-aided 3D printing, in situ additive manufacturing has the advantage of matching the geometry of the defect to be repaired without specific preliminary image analysis, shaping the bioscaffold within the defect, and achieving the best possible contact between the bioscaffold and the host tissue. Here, we describe an in situ approach that allows 3D bioprinting of human adipose-derived stem cells (hADSCs) laden in 10%GelMa/2%HAMa (GelMa/HAMa) hydrogel. We use coaxial extrusion to obtain a core/shell bioscaffold with high cell viability, as well as adequate mechanical properties for articular cartilage regeneration and repair.
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http://dx.doi.org/10.1007/978-1-0716-0520-2_9DOI Listing
March 2021
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