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1 |
Optimizing the electrical conductivity of polyacrylonitrile/polyaniline with nickel nanoparticles for the enhanced electrostimulation of Schwann cells proliferation
بهینه سازی رسانایی الکتریکی پلی اکریلونیتریل/پلی آنیلین با نانوذرات نیکل برای تحریک الکتریکی افزایش یافته تکثیر سلول های شوان-2021 Tissue engineering scaffolds made of biocompatible polymers are promising alternatives for nerve reparation. For this application, cell proliferation will be speeded up by electrostimulation, which required
electrically-conductive materials. Here, a biomimicking scaffold with optimized conductivity was developed from electrospun polyacrylonitrile/electrically-conductive polyaniline (PAN/PANI) nanofibers
doped with Ni nanoparticles. PAN/PANI/Ni was biocompatible for Schwann cells and exhibited a suitable
tensile strength and wettability for cell proliferation. When compared with unmodified PAN/PANI, the
electrical conductivity of PAN/PANI/Ni was 6.4 fold higher. Without electrostimulation, PAN/PANI and
PAN/PANI/Ni exhibited similar Schwann cells’ proliferation rates. Upon electrostimulation at
100 mV cm1 for one hour per day over five days, PAN/PANI/Ni accelerated Schwann cells’ proliferation
2.1 times compared to PAN/PANI. These results demonstrate the importance of expanding the electrical
conductivity of the tissue engineering scaffold to ensure optimal electrostimulation of nerve cell growth.
Additionally, this study describes a straightforward approach to modulate the electrical conductivity of
polymeric materials via the addition of Ni nanoparticles that can be applied to different biomimicking
scaffolds for nerve healing.
Keywords: Nerve tissue engineering | Electrospinning | PAN/PANI | Ni nanoparticles | Schwann cells |
مقاله انگلیسی |
2 |
Sustainable chitosan-based electrical responsive scaffolds for tissue engineering applications
داربست های پاسخگو الکتریکی مبتنی بر کیتوزان پایدار برای کاربردهای مهندسی بافت-2021 Electroconductive biomaterials have potential in the regeneration of electrically active biological tissues (neural,
orthopedic, cardiac). The aim of this study was to develop an electroconductive scaffold using natural and/or
sustainable materials. A composite scaffold made of chitosan, a compound of natural origin, and with incorporated with graphitic carbon obtained from cork (natural and sustainable source) as an electroconductive filler,
was prepared. Chitosan (Ch) scaffolds with different concentration of pyrolyzed cork (PC) were prepared and
fully characterized. An electroconductivity of 5.5 × 10−5 S/cm, i.e. in the range of cardiac tissues, was obtained.
FTIR and XPS analysis did not show the presence of chemical bonds between the two components. Despite
this, the composite scaffold showed higher thermal stability; moreover, their mechanical strength was significantly higher than for the pure chitosan. The biocompatibility of Ch-PC composite scaffolds has been verified
by SH-SY5Y neuroblastoma cell viability assay. This study shows that a sustainable composite made with chitosan
and an innovative electroconductive filler has potential application in tissue engineering.
Keywords: Conductive polymers | Chitosan | Tissue engineering | Graphitic carbon | Natural sources |
مقاله انگلیسی |
3 |
3D-printable conductive materials for tissue engineering and biomedical applications
مواد رسانای قابل چاپ سه بعدی برای مهندسی بافت و کاربردهای زیست پزشکی-2021 Many patients that undergo autografting suffer from donor site morbidity and risk of immune rejection. Tissue
engineering is receiving considerable attention as engineered tissues could help overcome the drawbacks of
autografts and achieve better performance on tissue repair, replacement and regeneration. Conductivity is one of
the desired properties of engineered scaffolds and tissue constructs as bioelectricity plays an important role in the
native physiological environment. Hence, conductive materials have been extensively used in the making of
biosensors, tissue engineering scaffolds and drug delivery systems to elicit electrically-mediated signals, thus
mimicking the natural cellular environment. Conductive polymers, carbon-based materials, and metal nanoparticles are the main categories of conductive materials used. Ionic liquids, especially biocompatible ionic
liquids, is currently being explored as a competitive filler composite to greatly improve the conductivity of
polymers with little to zero cytotoxicity. The effects of electrical stimulation on cell alignment, migration,
proliferation, and differentiation as well as detailed properties of different types of conductive materials are
briefly yet succinctly reviewed. Furthermore, 3D printing of conductive scaffolds and hydrogels, and their corresponding biomedical applications are also discussed.
Keywords: Conductive biomaterials | Bioprinting | Tissue engineering | Ionic liquids | Electrical stimulation |
مقاله انگلیسی |
4 |
Electro-conductive carbon nanofibers containing ferrous sulfate for bone tissue engineering
Electro-conductive carbon nanofibers containing ferrous sulfate for bone tissue engineering-2021 The application of electroactive scaffolds can be promising for bone tissue engineering applications. In the
current paper, we aimed to fabricate an electro-conductive scaffold based on carbon nanofibers (CNFs) containing ferrous sulfate. FeSO4⋅7H2O salt with different concentrations 5, 10, and 15 wt%, were blended with
polyacrylonitrile (PAN) polymer as the precursor and converted to Fe2O3/CNFs nanocomposite by electrospinning and heat treatment. The characterization was conducted using SEM, EDX, XRD, FTIR, and Raman
methods. The results showed that the incorporation of Fe salt induces no adverse effect on the nanofibers
morphology. EDX analysis confirmed that the Fe ions are uniformly dispersed throughout the CNF mat. FTIR
spectroscopy showed the interaction of Fe salt with PAN polymer. Raman spectroscopy showed that the incorporation of FeSO4⋅7H2O reduced the ID/IG ratio, indicating more ordered carbon in the synthesized nanocomposite. Electrical resistance measurement depicted that, although the incorporation of ferrous sulfate
reduced the electrical conductivity, the conductive is suitable for electrical stimulation. The in vitro studies
revealed that the prepared nanocomposites were cytocompatible and only negligible toxicity (less than 10%)
induced by CNFs/Fe2O3 fabricated from PAN FeSO4⋅7H2O 15%. Although various nanofibrous composite
fabricated with Fe NPs have been evaluated for tissue engineering applications, CNFs exhibited promising
properties, such as excellent mechanical strength, biocompatibility, and electrical conductivity. These results
showed that the fabricated nanocomposites could be applied as the bone tissue engineering scaffold.
Keywords: Bone tissue engineering | Electrospinning | Carbon nanofiber | Ferrous sulfate |
مقاله انگلیسی |
5 |
Electrically conductive biocompatible composite aerogel based on nanofibrillated template of bacterial cellulose/polyaniline/nano-clay
ایروژل کامپوزیتی زیست سازگار رسانای الکتریکی بر اساس الگوی نانوفیبریل شده از سلولز باکتریایی/پلی آنیلین/نانو خاک رس-2021 Bacterial cellulose (BC) aerogel owing to its porous and 3D structure, poses a suitable matrix for embedding
nanomaterials and polymers. Herein, BC composites comprising nano-clay/polyaniline (PANI) were synthesized
via a two-step procedure. Clay nanoplatelets were dispersed in the BC membrane to form a nanofibrillated template for aniline in-situ polymerization leading to formation of a double interconnected network of electrically
conductive path within the aerogel. Deposition of PANI particles on BC/clay nanocomposite was confirmed by
FTIR, XRD, FESEM, and EDX techniques. The surface electrical conductivity of 0.49 S/cm was obtained for the composite aerogel comprising 5 wt% nano-clay which is 16 folds higher than that of the sample without nano-clay.
Thermal stability and storage modulus of the aerogels was improved by inclusion of PANI and nano-clay. Synergistic effect of clay and polyaniline on biocompatibility and cell adhesion was obtained with no mutagenic or carcinogenic effects. The developed electrically conductive composite aerogels can be utilized as suitable scaffolds
for tissue engineering applications demanding a good balance of flexibility, dimensional and thermal stability
and biocompatibility.
Keywords: Bacterial cellulose | Nanocomposite aerogels | Polyaniline | Nano-clay | Biocompatibility |
مقاله انگلیسی |
6 |
Printable alginate/gelatin hydrogel reinforced with carbon nanofibers as electrically conductive scaffolds for tissue engineering
هیدروژل آلژینات/ژلاتین قابل چاپ تقویت شده با نانوالیاف کربن به عنوان داربست های رسانای الکتریکی برای مهندسی بافت-2021 Shortages of organs and damaged tissues for transplantation have prompted improvements in biomaterials
within the field of tissue engineering (TE). The rise of hybrid hydrogels as electro-conductive biomaterials offers
promise in numerous challenging biomedical applications. In this work, hybrid printable biomaterials comprised
of alginate and gelatin hydrogel systems filled with carbon nanofibers (CNFs) were developed to create electroconductive and printable 3-D scaffolds. Importantly, the preparation method allows the formation of
hydrogels with homogenously dispersed CNFs. These hybrid composite hydrogels were evaluated in terms of
mechanical, chemical and cellular response. They display excellent mechanical performance, which is
augmented by the CNFs, with Young’s moduli and conductivity reaching 534.7 ± 2.7 kPa and 4.1 × 10− 4 ± 2 ×
10− 5 S/cm respectively. CNF incorporation enhances shear-thinning behaviour, allowing ease of 3-D printing. Invitro studies indicate improved cellular proliferation compared to controls. These conductive hydrogels have the
potential to be used in a myriad of TE strategies, particularly for those focused on the incorporation of electroconductive components for applications such as cardiac or neuronal TE strategies.
Keywords: Electroactive | Hydrogels | Tissue engineering |
مقاله انگلیسی |
7 |
Assemblies of Perisomatic GABAergic Neurons in the Developing Barrel Cortex
مجامع سلولهای عصبی گاباژیک پریسوماتیک در توسعه قشر بارل-2020 The developmental journey of cortical interneurons
encounters several activity-dependent milestones.
During the early postnatal period in developing
mice, GABAergic neurons are transient preferential
recipients of thalamic inputs and undergo activitydependent
migration arrest, wiring, and programmed
cell-death. Despite their importance for
the emergence of sensory experience and the role
of activity in their integration into cortical networks,
the collective dynamics of GABAergic neurons during
that neonatal period remain unknown. Here, we
study coordinated activity in GABAergic cells of the
mouse barrel cortex using in vivo calcium imaging.
We uncover a transient structure in GABAergic
population dynamics that disappears in a sensorydependent
process. Its building blocks are anatomically
clustered GABAergic assemblies mostly
composed by prospective parvalbumin-expressing
cells. These progressively widen their territories until
forming a uniform perisomatic GABAergic network.
Such transient patterning of GABAergic activity is a
functional scaffold that links the cortex to the
external world prior to active exploration |
مقاله انگلیسی |
8 |
Design of fluorescent sensors based on azaheterocyclic push-pull systems towards nitroaromatic explosives and related compounds: A review
طراحی سنسورهای فلورسنت مبتنی بر سیستمهای فشار کششی azaheterocyclic به سمت مواد منفجره نیتروارماتیک و ترکیبات مرتبط: بررسی-2020 Highly sensitive and selective detection of nitro containing high energy organic compounds such as picric acid
(PA), 2,4,6-trinitrotoluene (TNT) and 2,4-dinitrotoluene (DNT) has become a challenging task due to concerns
over national security, criminal investigations and environment protections. Among various known detection
methods, fluorescence sensors have gained special attention in recent time. The family of fluorescent sensors
based on push-pull systems that incorporate nitrogen heterocycles as an electron-withdrawing group have a
growing interest due to their high sensitivity, selectivity and easy tuning. The fluorescent sensors discussed in
this review are classified and organized according to used azaheterocyclic scaffold, their functionality and their
ability to detect of nitroaromatics by fluorescence quenching. Keywords: Nitroaromatic explosives | Fluorescence quenching | Pyridines | Pyrimidines | Pyrazines | Triazines |
مقاله انگلیسی |
9 |
Do international marketing simulations provide an authentic assessment of learning? A student perspective
آیا شبیه سازی بازاریابی بین المللی ارزیابی معتبر از یادگیری ارائه می دهد؟ دیدگاه دانشجویی-2020 This paper seeks to determine whether international marketing simulations provide an authentic
assessment of learning. The principles of authentic assessment dictate that assigned learning
activities be aligned with the attitudes, skills and knowledge that students will be required to
demonstrate in the real world. Research on the application of authentic assessment principles in
management education is limited and most of the works that have examined the issue have done
so from the perspective of the educator, not the student. A content analysis was undertaken of
122 final reports submitted by teams participating in an online international marketing simulation.
The results demonstrate that the simulation provided students with opportunities for
reflection and the development of an understanding of the real world of international marketing,
with all its complexities and challenges. The simulation also allowed students to receive feedback,
correct mistakes and gain an appreciation of the varied activities that contribute to the
achievement of an overall objective. Students did not, however, appreciate the transferability of
skills acquired in the simulation to other domains of knowledge. Similarly, the final reports did
not reflect a significant appreciation of the communication and collaboration benefits that simulations
should provide. Further, provision of instructional support was shown to have no
impact on students perceptions of the simulations authenticity. Keywords: Authentic assessment | International marketing simulation | Business simulation | Learning | Marketing education | Scaffolding | International marketing | Management education |
مقاله انگلیسی |
10 |
Demonstrating reliability through transparency: A scientific validity framework to assist scientists and lawyers in criminal proceedings
اثبات قابلیت اطمینان از طریق شفافیت: یک چارچوب اعتبار علمی برای کمک به دانشمندان و حقوقدانان در دادرسی کیفری-2020 In recent decades, forensic science evidence has come to play an increasingly significant role in criminal
proceedings. However, the ability of non-scientists (lay-persons, including lawyers and judges) within
criminal justice systems to recognise and resolve issues of validity and reliability relating to expert
opinion evidence has not maintained pace with the need to do so. Despite international scrutiny from
scientists, statisticians, governments and those involved in law reform, the parameters of a) different
forensic disciplines and b) some case specific interpretations, remain elusive to some legal practitioners
and judges. It is therefore essential that within the context of national, and increasingly international and
transnational criminal investigations, forensic science experts convey the evidential value of the
scientific findings in a manner that is understandable to, and useable by all.
To assist, this paper first identifies the organisational structures necessary to scaffold and support the
delivery of reliable expert opinion evidence. This is followed by a format for transparently reporting the
reasoning and the scientific validity underpinning the expert’s evidence within their report: a tripartite
Scientific Validity Framework. This framework is comprised of (i) foundational validity, (ii) applied
validity and (iii) the new concept of evaluative validity. Such a framework, because of its underlying
scientific principles, is applicable to expert reports in any jurisdiction and is complementary to different
national approaches. That is because utilising this framework could ensure that experts can, and do,
demonstrate that their case-specific opinion is reliable and alert the legal profession to the expert’s
reasoning process and any limitations in the scientific validity underpinning the opinion Keywords: Expert opinion evidence | Scientific validity | Critical trust | Reliability |
مقاله انگلیسی |