C oronary heart disease is the leading cause of the rising incidence of heart failure worldwide.1 Following myocardial infarction (MI), the limited regenerative potential of the heart causes scar formation in and around the infarction, leading to abnormal electric signal propagation and desynchronized cardiac activation and contraction.2 The lack of electric connection between healthy myocardium and the scar with its islands of intact cardiomyocytes contributes to progressive functional decompensation. Injectable biomaterial has shown promise as an alternative biological treatment option after MI to reduce adverse remodeling and preserve cardiac function.3,4 Among their many advantages, injectable materials can be delivered alone or as a vehicle carrying combination therapies, including cells or growth factors, and may provide mechanical and functional support to the injured heart. Over the past decade, several injectable biomaterials such as collagen, 5,6 alginate, 7 and fibrin 8 have been extensively studied. Organic polymers that conduct electricity (conductive polymers) were first described in 1977, and this discovery was awarded the Nobel prize in 2000.9,10 Conductive polymers are particularly appealing because they exhibit electric properties similar to metals and semiconductors while retaining flexibility, ease of processing, and modifiable conductivity. The electric properties of these materials can be fine-tuned by altering their synthetic processes, including the addition of specific chemical agents.11 Biological applications of conductive polymersBackground-Efficient cardiac function requires synchronous ventricular contraction. After myocardial infarction, the nonconductive nature of scar tissue contributes to ventricular dysfunction by electrically uncoupling viable cardiomyocytes in the infarct region. Injection of a conductive biomaterial polymer that restores impulse propagation could synchronize contraction and restore ventricular function by electrically connecting isolated cardiomyocytes to intact tissue, allowing them to contribute to global heart function. Methods and Results-We created a conductive polymer by grafting pyrrole to the clinically tested biomaterial chitosan to create a polypyrrole (PPy)-chitosan hydrogel. Cyclic voltammetry showed that PPy-chitosan had semiconductive properties lacking in chitosan alone. PPy-chitosan did not reduce cell attachment, metabolism, or proliferation in vitro. Neonatal rat cardiomyocytes plated on PPy-chitosan showed enhanced Ca 2+ signal conduction in comparison with chitosan alone. PPy-chitosan plating also improved electric coupling between skeletal muscles placed 25 mm apart in comparison with chitosan alone, demonstrating that PPy-chitosan can electrically connect contracting cells at a distance. In rats, injection of PPy-chitosan 1 week after myocardial infarction decreased the QRS interval and increased the transverse activation velocity in comparison with saline or chitosan, suggesting improved electric conduction. Optical mapping showed incr...
The necessity for new sources for greener and cleaner energy production to replace the existing ones has been increasingly growing in recent years. Of those new sources, the hydrogen evolution reaction has a large potential. In this work, for the first time, MoSe /Mo core-shell 3D-hierarchical nanostructures are created, which are derived from the Mo 3D-hierarchical nanostructures through a low-temperature plasma-assisted selenization process with controlled shapes grown by a glancing angle deposition system.
A noncatalytic and template-free vapor transport process has been employed to prepare single-crystalline Sn nanowires with diameters of 10-20 nm. The growth of one-dimensional Sn nanowires follows the mechanism similar to the vapor-solid (V-S) mechanism. Two-dimensional square-shaped nanostructures were also found to form in the region of lower deposition temperatures. The rich morphology may be attributed to the competition in growth rate among different crystallographic planes. Structural characterization with high-resolution transmission electron microscopy showed that the nanowires and nanosquares grew in a preferential direction of [200]. The superconducting transition temperatures for Sn nanowires and Sn nanosquares were about 3.7 K, which was very close to that of bulk beta-Sn. Magnetization measurements showed that the critical magnetic fields for both Sn nanowires and Sn nanosquares increased significantly as compared to that of bulk Sn.
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An environmentally friendly antisolvent approach, which involves only biocompatible chemicals and mild processing conditions, was developed to prepare various ZnO nanostructures including twin-cones and nanorods with controllable dimensions. The method was based on the dissolution of ZnO powders in a deep eutectic solvent (DES), followed by precipitation of ZnO nanostructures from the DES upon introduction of an antisolvent. It is the first example of the room temperature ionic liquid based antisolvent process for preparation of nanomaterials. Through suitably modulating the processing conditions, such as the ethanol content of the antisolvent and the injection time of the ZnO-containing DES, the morphology of the resulting ZnO nanostructures can be readily controlled. Anisotropic crystal growth was achieved without severe reaction conditions, such as high temperatures and high vacuums, or use of environmentally harmful chemicals, such as long carbon chain surfactants and capping reagents. The present method can be readily extended to produce versatile nanostructures of other functional materials.
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