The rationale and emergence of electroconductive biomaterial scaffolds in cardiac tissue engineering

The human heart possesses minimal regenerative potential, which can often lead to chronic heart failure following myocardial infarction. Despite the successes of assistive support devices and pharmacological therapies, only a whole heart transplantation can sufficiently address heart failure. Engineered scaffolds, implantable patches, and injectable hydrogels are among the most promising solutions to restore cardiac function and coax regeneration; however, current biomaterials have yet to achieve ideal tissue regeneration and adequate integration due a mismatch of material physicochemical properties. Conductive fillers such as graphene, carbon nanotubes, metallic nanoparticles, and MXenes and conjugated polymers such as polyaniline, polypyrrole, and poly(3,4-ethylendioxythiophene) can possibly achieve optimal electrical conductivities for cardiac applications with appropriate suitability for tissue engineering approaches. Many studies have focused on the use of these materials in multiple fields, with promising effects on the regeneration of electrically active biological tissues such as orthopedic, neural, and cardiac tissue. In this review, we critically discuss the role of heart electrophysiology and the rationale toward the use of electroconductive biomaterials for cardiac tissue engineering. We present the emerging applications of these smart materials to create supportive platforms and discuss the crucial role that electrical stimulation has been shown to exert in maturation of cardiac progenitor cells

The rationale and emergence of electroconductive biomaterial scaffolds in cardiac tissue engineering

The human heart possesses minimal regenerative potential, which can often lead to chronic heart failure following myocardial infarction. Despite the successes of assistive support devices and pharmacological therapies, only a whole heart transplantation can sufficiently address heart failure. Engineered scaffolds, implantable patches, and injectable hydrogels are among the most promising solutions to restore cardiac function and coax regeneration; however, current biomaterials have yet to achieve ideal tissue regeneration and adequate integration due a mismatch of material physicochemical properties. Conductive fillers such as graphene, carbon nanotubes, metallic nanoparticles, and MXenes and conjugated polymers such as polyaniline, polypyrrole, and poly(3,4-ethylendioxythiophene) can possibly achieve optimal electrical conductivities for cardiac applications with appropriate suitability for tissue engineering approaches. Many studies have focused on the use of these materials in multiple fields, with promising effects on the regeneration of electrically active biological tissues such as orthopedic, neural, and cardiac tissue. In this review, we critically discuss the role of heart electrophysiology and the rationale toward the use of electroconductive biomaterials for cardiac tissue engineering. We present the emerging applications of these smart materials to create supportive platforms and discuss the crucial role that electrical stimulation has been shown to exert in maturation of cardiac progenitor cells

Controlled Radiation Damage and Edge Structures in Boron Nitride Membranes

We show that hexagonal boron nitride membranes synthesized by chemical exfoliation are more resistant to electron beam irradiation at 80 kV than is graphene, consistent with quantum chemical calculations describing the radiation damage processes. Monolayer hexagonal boron nitride does not form vacancy defects or amorphize during extended electron beam irradiation. Zigzag edge structures are predominant in thin membranes for both a freestanding boron nitride monolayer and for a supported multilayer step edge. We have also determined that the elemental termination species in the zigzag edges is predominantly N

Controlled Radiation Damage and Edge Structures in Boron Nitride Membranes

We show that hexagonal boron nitride membranes synthesized by chemical exfoliation are more resistant to electron beam irradiation at 80 kV than is graphene, consistent with quantum chemical calculations describing the radiation damage processes. Monolayer hexagonal boron nitride does not form vacancy defects or amorphize during extended electron beam irradiation. Zigzag edge structures are predominant in thin membranes for both a freestanding boron nitride monolayer and for a supported multilayer step edge. We have also determined that the elemental termination species in the zigzag edges is predominantly N

Templated Synthesis of SiO₂ Nanotubes for Lithium-Ion Battery Applications: An In Situ (Scanning) Transmission Electron Microscopy Study

One of the weaknesses of silicon-based batteries is the rapid deterioration of the charge-storage capacity with increasing cycle numbers. Pure silicon anodes tend to suffer from poor cycling ability due to the pulverization of the crystal structure after repeated charge and discharge cycles. In this work, we present the synthesis of a hollow nanostructured SiO2 material for lithium-ion anode applications to counter this drawback. To improve the understanding of the synthesis route, the crucial synthesis step of removing the ZnO template core is shown using an in situ closed gas-cell sample holder for transmission electron microscopy. A direct visual observation of the removal of the ZnO template from the SiO2 shell is yet to be reported in the literature and is a critical step in understanding the mechanism by which these hollow nanostructures form from their core–shell precursors for future electrode material design. Using this unique technique, observation of dynamic phenomena at the individual particle scale is possible with simultaneous heating in a reactive gas environment. The electrochemical benefits of the hollow morphology are demonstrated with exceptional cycling performance, with capacity increasing with subsequent charge–discharge cycles. This demonstrates the criticality of nanostructured battery materials for the development of next-generation Li+-ion batteries

Two-Dimensional Chiroptically Active Copper Oxide Nanostructures

Induction of chirality in colloidal nanomaterials has been of great interest in recent years due to the broad range of potential applications for these materials, including in biomedicine, sensing, and photocatalysis. However, the investigation of chirality induction in two-dimensional (2D) nanomaterials is currently at a very early stage, despite their potential unique properties and important applications. Here, we report the synthesis and characterization of chiroptically active 2D copper(II) oxide (CuO)-based nanomaterials for the first time. In our studies we demonstrate that postsynthetic treatment of copper- aluminium carbonate intercalated layered double hydroxide (CuAl-CO3 LDH) nanosheets with phenylalanine at room temperature under basic conditions results in the formation of two-dimensional chiral CuO nanosheets exhibiting strong circular dichroism signals, far beyond the onset of the characteristic signals of the initial ligands

Quantitative Evaluation of Surfactant-stabilized Single-walled Carbon Nanotubes: Dispersion Quality and Its Correlation with Zeta Potential

Stable dispersions of single-walled carbon nanotubes in deionized water were prepared using six common surfactants: sodium dodecylbenzene sulfonate (SDBS), sodium dodecyl sulfate (SDS), lithium dodecyl sulfate (LDS), tetradecyl trimethyl ammonium bromide (TTAB), sodium cholate (SC), and Fairy liquid (FL). For all nanotube dispersions (CNT = 1 mg/mL), the optimum concentration of surfactant was found to be close to CSurf = 10 mg/mL by measuring the fraction of nanotubes remaining after centrifugation for a range of surfactant concentrations. The aggregation state of each nanotube−surfactant dispersion was characterized as a function of nanotube concentration by AFM analysis of large numbers of nanotubes/bundles deposited onto substrates. The dispersion quality could then be quantified by four parameters: the saturation value (at low concentration) of the root-mean-square bundle diameter, the maximum value of the total number of dispersed objects (individuals and bundles) per unit volume of dispersion, the saturation value (at low concentration) of the number fraction of individual nanotubes, and the maximum value of the number of individual nanotubes per unit volume of dispersion. According to these metrics, the dispersion quality of the six surfactant−nanotube dispersions varied as SDS > LDS > SDBS > TTAB > SC > Fairy liquid. It was found that each of these dispersion-quality metrics scaled very well with the measured ζ-potential of the surfactant−nanotube dispersion. This confirms that dispersion quality is controlled by the magnitude of electrostatic repulsive forces between coated nanotubes

Spontaneous Exfoliation of Single-Walled Carbon Nanotubes Dispersed Using a Designed Amphiphilic Peptide

We have observed concentration dependent exfoliation of single-walled carbon nanotubes dispersed in solutions of the synthetic peptide nano-1. As the nanotube concentration is reduced, the bundle diameters tend to decrease before saturating at −3 mg/mL. The fraction of individual nanotubes increases with decreasing concentration, saturating at ∼95% at low concentration. This concentration dependent exfoliation happens even if the dispersions are not sonicated on dilution, albeit over a longer time scale. The populations both of individual nanotubes and of bundles are much higher than expected at high concentrations, indicating the presence of repulsive internanotube interactions stabilizing the dispersions

High Quality Dispersions of Functionalized Single Walled Nanotubes at High Concentration

Single walled nanotubes are difficult to disperse in solvents, with dispersion quality limited by nanotube bundling at high concentration. We quantitatively study dispersions of singlewall nanotubes, functionalized with the bulky molecules PABS, PEG, and ODA, in common solvents. TGA measurements coupled with AFM analysis of deposited nanotubes shows almost complete coverage of the functionalities along the nanotube body. The best solvents are characterized by Hildebrand solubility parameters that are close to those of the functional groups. At low concentration, the dispersions contain predominately individual functionalized SWNTs as evidenced by root-mean-square bundle diameters of ∼3−4 nm. This can be compared with the measured diameter of individual functionalized nanotubes of ∼3 nm. These nanotubes display very weak concentration dependent aggregation when dispersed in common solvents. Root-mean-square bundle diameters of only ∼5−6 nm were observed at concentrations as high as 1 mg/mL. This translates into >100 bundles per cubic micron of solvent, much higher than observed in other systems. These results have practical implications for the production of well dispersed polymer-nanotube composites that would be expected to display high interfacial stress transfer

Spontaneous Debundling of Single-Walled Carbon Nanotubes in DNA-Based Dispersions

Natural salmon testes DNA has been used to disperse single-walled carbon nanotubes (SWNTs) in water. It has been found that the primary factor controlling the nanotube bundle size distribution in the dispersion is the nanotube concentration. As measured by AFM, the mean bundle diameter tends to decrease with decreasing concentration. The number fraction of individual nanotubes increases with decreasing concentration. At low nanotube concentrations, number fractions of up to 83% individual SWNTs, equating to a mass fraction of 6.2%, have been obtained. Both the absolute number density and mass per volume of individual nanotubes initially increased with decreasing concentration, displaying a peak at ∼0.027 mg/mL. This concentration thus yields the largest quantities of individually dispersed SWNTs. The AFM data for populations of individual nanotubes was confirmed by infrared photoluminescence spectroscopy. The photoluminescence intensity increased with decreasing concentration, indicating extensive debundling. The concentration dependence of the luminescence intensity matched well to the AFM data on the number density of individual nanotubes. More importantly, it was found that, once initially dispersed, spontaneous debundling occurs upon dilution without the need for sonication. This implies that DNA−SWNT hybrids exist in water as a solution rather than a dispersion. The effects of dilution have been compared to the results obtained by ultracentrifuging the samples, showing dilution methods to be a viable and cost-effective alternative to ultracentrifugation. It was found that even after 4 h of ultracentrifugation at 122 000g, bundles with diameters of up to 4 nm remained in solution. The bundle diameter distribution after ultracentrifugation was very similar to the equilibrium distribution for the appropriate concentration after dilution, showing ultracentrifugation to be equivalent to dilution