Electronic properties of 2D materials and their junctions

With an extensive range of distinctive features at nano meter-scale thicknesses,two-dimensional(2D)materials drawn the attention of the scientific community.Despite tremendous advancements in exploratory research on 2D materials,knowledge of 2D electrical transport and carrier dynamics still in its infancy.Thus,here we highlighted the electrical characteristics of 2D materials with electronic band structure,electronic transport,dielectric constant,carriers mobility.The atomic thinness of 2D materials makes substantially scaled field-effect transistors(FETs)with reduced short-channel effects conceivable,even though strong carrier mobility required for high performance,low-voltage device operations.We also discussed here about factors affecting 2D materials which easily enhanced the activity of those materials for various applications.Presently,Those 2D materials used in state-of-the-art electrical and optoelectronic devices because of the extensive nature of their electronic band structure.2D materials offer unprecedented freedom for the design of novel p-n junction device topologies in contrast to conventional bulk semiconductors.We also,describe the numerous 2D p-n junctions,such as homo junction and hetero junction including mixed dimensional junctions.Finally,we talked about the problems and potential for the future.

Cardiogenic differentiation of mesenchymal stem cells on elastomeric poly (glycerol sebacate)/collagen core/shell fibers

AIM: To facilitate engineering of suitable biomaterials to meet the challenges associated with myocardial infarction. METHODS: Poly (glycerol sebacate)/collagen (PGS/ collagen) core/shell fibers were fabricated by core/ shell electrospinning technique, with core as PGS and shell as collagen polymer; and the scaffolds were characterized by scanning electron microscope (SEM), fourier transform infrared spectroscopy (FTIR), contact angle and tensile testing for cardiac tissue engineering. Collagen nanofibers were also fabricated by electrospinning for comparison with core/shell fibers. Studies on cell-scaffold interaction were carriedout using cardiac cells and mesenchymal stem cells (MSCs) co-culture system with cardiac cells and MSCs separately serving as positive and negative controls respectively. The co-culture system was characterized for cell proliferation and differentiation of MSCs into cardiomyogenic lineage in the co-culture environment using dual immunocytochemistry. The co-culture cells were stained with cardiac specific marker proteins like actinin and troponin and MSC specific marker protein CD 105 for proving the cardiogenic differentiation of MSCs. Further the morphology of cells was analyzed using SEM.RESULTS: PGS/collagen core/shell fibers, core is PGS polymer having an elastic modulus related to that of cardiac fibers and shell as collagen, providing natural environment for cellular activities like cell adhesion, proliferation and differentiation. SEM micrographs of electrospun fibrous scaffolds revealed porous, beadless, uniform fibers with a fiber diameter in the range of 380 ± 77 nm and 1192 ± 277 nm for collagen fibers and PGS/collagen core/shell fibers respectively. The obtained PGS/collagen core/shell fibrous scaffolds were hydrophilic having a water contact angle of 17.9 ± 4.6° compared to collagen nanofibers which had a contact angle value of 30 ± 3.2°. The PGS/collagen core/shell fibers had mechanical properties comparable to that of native heart muscle with a young's modulus of 4.24 ± 0.7 MPa, while that of collagen nanofibers was comparatively higher around 30.11 ± 1.68 MPa. FTIR spectrum was performed to confirm the functional groups present in the electrospun scaffolds. Amide Ⅰ and amide Ⅱ of collagen were detected at 1638.95 cm -1 and 1551.64 cm -1 in the electrospun collagen fibers and at 1646.22 cm -1 and 1540.73 cm -1 for PGS/collagen core/shell fibers respectively. Cell culture studies performed using MSCs and cardiac cells co-culture environment, indicated that the cellproliferation significantly increased on PGS/collagen core/shell scaffolds compared to collagen fibers and the cardiac marker proteins actinin and troponin were expressed more on PGS/collagen core/shell scaffolds compared to collagen fibers alone. Dual immunofluorescent staining was performed to further confirm the cardiogenic differentiation of MSCs by employing MSC specific marker protein, CD 105 and cardiac specific marker protein, actinin. SEM observations of cardiac cells showed normal morphology on PGS/collagen fibers and providing adequate tensile strength for the regeneration of myocardial infarction. CONCLUSION: Combination of PGS/collagen fibers and cardiac cells/MSCs co-culture system providing natural microenvironments to improve cell survival and differentiation, could bring cardiac tissue engineering to clinical application.

Effects of nanotopography on stem cell phenotypes

Stem cells are unspecialized cells that can self renew indefinitely and differentiate into several somatic cells given the correct environmental cues.In the stem cell niche,stem cell-extracellular matrix(ECM)interactions are crucial for different cellular functions,such as adhesion,proliferation,and differentiation.Recently, in addition to chemical surface modifications,the importance of nanometric scale surface topography and roughness of biomaterials has increasingly becoming recognized as a crucial factor for cell survival and host tissue acceptance in synthetic ECMs.This review describes the influence of nanotopography on stem cell phenotypes.

Conducting Polyaniline-Electrical Charge Transportation

Conductive polyanilines are synthesized by doping with inorganic and organic acids, namely Hydrochloric acid (HCl) and ±10-camphor sulfonic acid (CSA). The direct current (DC) conductivities (σDC) are found to be about 9.5 ′ 10-8, 1.8, and 95.8 S/cm for PANI base, PANI(HCl) and PANI(CSA), respectively. σDC is measured down to a temperature of ~100 K and the apparent change in the activation energies are found to be 98.16, 74.40, and 57.24 meV for PANI base, HCl, and CSA dopings respectively. σDC is less temperature dependent near room temperature, further decrease in temperature the σDC is strongly dependent. Upon the inspection of AC conductivities (σAC) versus frequency curves, it can be inferred that the conduction process is noticeably influenced upon doping and within the dopants. σAC has shown classical plateau (DC-AC crossover) region, nonetheless shifted crossover frequency (critical frequency) upon doping is rather interesting. Critical frequencies (wc) are obtained from universal power-law for all samples. The variation in the dielectric properties can be attributed to the dopant incorporation. In material characterization, successful doping is corroborated by FTIR, UV-vis spectroscopy and slight influence upon doping can also be seen in thermal properties. Intense photoluminescence (PL) peaks at 322.5, 581.4 and 644.2 nm are observed. PANI(CSA) exhibited highest peak intensity followed by PANI(HCl) and PANI base.

Strategies for regeneration of components of nervous system: scaffolds, cells and biomolecules

Nerve diseases including acute injury such as peripheral nerve injury(PNI),spinal cord injury(SCI)and traumatic brain injury(TBI),and chronic disease like neurodegeneration disease can cause various function disorders of nervous system,such as those relating to memory and voluntary movement.These nerve diseases produce great burden for individual families and the society,for which a lot of efforts have been made.Axonal pathways represent a unidirectional and aligned architecture allowing systematic axonal development within the tissue.Following a traumatic injury,the intricate architecture suffers disruption leading to inhibition of growth and loss of guidance.Due to limited capacity of the body to regenerate axonal pathways,it is desirable to have biomimetic approach that has the capacity to graft a bridge across the lesion while providing optimal mechanical and biochemical cues for tissue regeneration.And for central nervous system injury,one more extra precondition is compulsory:creating a less inhibitory surrounding for axonal growth.Electrospinning is a cost-effective and straightforward technique to fabricate extracellular matrix(ECM)-like nanofibrous structures,with various fibrous forms such as random fibers,aligned fibers,3D fibrous scaffold and core-shell fibers from a variety of polymers.The diversity and versatility of electrospinning technique,together with functionalizing cues such as neurotrophins,ECM-based proteins and conductive polymers,have gained considerable success for the nerve tissue applications.We are convinced that in the future the stem cell therapy with the support of functionalized electrospun nerve scaffolds could be a promising therapy to cure nerve diseases.